Features

In the first part of a two-part article for Electrical Review, Paul Owen from Substation Expertise explains how a standard, low cost, laptop computer can be installed and set up with ‘off the shelf' graphics software and used to gather information from remote devices, connected along a ‘data bus' cable, (twisted copper pair, and / or optic fibre) from remote locations around a large building, or building complex

This feature covers small scale projects, using low cost products, and is not relevant to large scale Scada schemes (supervisory, control and data acquisition) such as power network transmission and distribution monitoring over a large geographical area, for example a city or county. Such projects are large scale and require much more expensive hardware and software - to near military standards - in order to achieve the speed and reliability necessary. 

Monitoring
The definition of monitoring is usually regarded as look but don't touch and the computer displays data collected from input devices connected along the data bus. There are no outpu' devices in this case.  

Control
This function involves signals being sent either manually, via the mouse, or automatically via a ladder diagram to outputs connected along the data bus which then, in turn, initiates:
- motors to start or stop
- circuit breakers to close or open
- valves to close or open
- solenoids to close or open
- dampers to close or open

Intelligent electronic devices
Devices connected along the data bus are known as IEDs (intelligent electronic devices) and these can be simple products such as low end protection relays, power meters and digital I/O modules (input & output modules) etc which are both low-cost and easy to set up and prove. More complex IEDs such as disturbance recorders, fault analysers and protection relays where the parameters are remotely set, have very large data bases, and are considerably more expensive, and more time consuming to apply, set up and prove. Again, this article is focusing on the low end simple applications and in the writers view, for simple, small scale applications, any accessing of data from complex devices is best done by loading the specific data in question direct to specialist software within a laptop, down a short lead. Attempting to transmit this over the data bus, unnecessarily slows down communications and increases the volume of traffic and with it the increased risk of signal collision errors occurring. Each IED has a unique bus address, set either physically by small switches, or codes within the software.

To illustrate the difference between simple and complex IEDs one only has to look at the thickness of the applications & set up documents, which can vary from a few sheets of text to very thick manuals / CDs, which are very demanding both in time to read, and understanding.

Colour graphics
Modern graphics software can seamlessly integrate digital and analogue signals from a wide range of distantly sited modules. Colour screens can show a considerable amount of information simultaneously, with real time animation, and in many different formats. These screens can be simple or complex in nature and the appearance is limited only by the imagination of the designer. An example of innovative graphics can show the single line power distribution diagram overlaid against the physical shape and structure of the building, or plot of land, which makes for a clearer understanding by the operator. 
For small scale substation monitoring, the most suitable Scada software comes from a process control background and big names include In Touch by Wonderware Invensys and iFIX by Intellution. These products are well proven, well supported and modular in nature, which means the bigger the I/O (input / output) count, the more you pay.

Typical applications
There are many reasons for installing a laptop based substation monitoring system, which offers a range of benefits to the end user or facilities management company operating on their behalf.

Typical applications are listed below, and these can be standalone, or bundled together.
It should be noted that engineering time and integration costs will rise as more applications are added, and that the more complex you make it, the harder it will be to prove after installation.

Alarms gathering
Probably the most common application, where alarms can be very wide ranging, and include:-

- protection trips on 11KV & 415V circuit breakers
- 415V Main Switchboard Busbar volts lost
- computer hall temperature too high
- PDU (power distribution unit) busbar voltage too high (or too low)
- transformer high temperature & bucholtz gas detection relay operation
- watchdogs on protection relays, programmable controllers and uninterruptible power supplies
- fault passage indicators on 11KV ring main units, for identifying fault location
- substation alarms from tripping batteries, intruder detectors, smoke detectors 
- overload tripping of pump and fan motor starters
- pre overload alert at say 95% of circuit current rating

Volt free contacts from protection relays and thermostats are hard wired to input modules connected along the data bus. The status of these alarm inputs is monitored by the graphics and the time and date of any alarm is recorded and logged.

All graphics pages will include an area to alert the operator to any fresh alarms, and when the alarm page is subsequently accessed, any active alarms will be listed and flashing / audible. When acknowledged, by clicking the mouse on a screen button, the flashing and audible alert stops. When cleared they are deleted from the active alarm list and transfer permanently to the historical alarm list. Critical alarms can be given priority and differentiated over those which are of less importance.

An important difference between expensive high end systems and low cost low end systems is the accuracy of time stamping. For example with a low cost system, the delay in the communications may result in an alarm time as being logged say 0.3 seconds after it occurred.

High end systems will access the correct time, from the data base within the protection relay concerned, and log the exact time of the alarm to within a millisecond. This sort of accuracy requires specialist hardware and software and setting up, and is consequently very expensive to achieve.

For 132KV transmission protection such accuracy is essential, however for monitoring 11KV & 415V distribution protection, within a building complex, it is probably not.   

Watchdog supervision
Most microprocessor based protection relays include watchdog contacts for monitoring failure of the internal electronics, which could otherwise, and dangerously, remain undetected for many years. Watchdog circuits always usually use a volt free contact which is open when no auxiliary supplies are present and remains closed once the auxiliary supplies are connected. The only time this contact opens is when the auxiliary supply is removed, or in the case of an internal electronics failure.

In practice the vast majority of these watchdog circuits are not used and a classic example of this is the temperature monitoring devices for cast resin distribution transformers, which are usually connected to operate in a non failsafe mode such that removal of the ac auxiliary supply (or a short term loss of 11KV mains supply) will not inadvertently trip the feeding 11KV circuit breaker. (i.e. behaving like an undesirable no volt protection relay)
There is a watchdog contact provided within these temperature monitoring devices to alert attention to an internal electronics failure, however these are very rarely connected.

Status monitoring
Status monitoring is done in the same way as alarm monitoring, but without the urgency.
The date and time of all changes of state are logged and permanently recorded on a historical list, which can analysed later if required, should there be an incident. 
Examples include: 
- circuit breaker position, for example open / closed / in service / withdrawn
- earth switch position, for example earth switch open / earth switch closed 
- motor starter status, for example available / not available / running / stopped
- valve / damper position, for example open / closed 
- solenoid position, for example energised / de-energised
- substation doors, for example open / closed

Power distribution network overview
Graphics can show a helicopter view of an entire electrical distribution network, quickly diagnosing what has happened during a total or partial blackout, so that supplies can be reconfigured and restored as fast as possible.

In such situations, any fault must be identified, and located with confidence, before any switching can be done, otherwise an alternative supply circuit breaker may be closed onto the same fault, and so spread the blackout. This application can avoid the time wasted travelling from one substation to another, assessing and working out what has failed and where.

The health and status of the entire distribution system can be viewed from one point, with remote control of critical circuit breakers from the PC, if required. The single line power diagram can be shown very simply and clearly, with semaphores indicating circuit breaker status. Also, if deemed a good idea, line colours can show the conductor status, such as red for energised, blue for deenergised, flashing black / yellow for fault and solid green for an earthed section, possibly under maintenance. (Note, this does add complexity, so is best limited to the main circuits.)

The clearest symbol for a circuit breaker is probably a black and white semaphore, driven by two inputs to confirm open and closed conditions. Loss of both signals results in a default symbol of an empty circle (ie. condition unknown) and as such a broken wire, or loose connection, to an input module, will not indicate a false breaker position.
A similar situation arises in the event of lost communications, where you have a choice of freezing the symbols, or declaring position unknown.

Using two inputs to confirm one of two positions is known as double binary confirmation and ensures positive contact indication. Using only one input and defaulting to an assumed position saves on inputs but is not a reliable method.

Power consumption metering for load optimisation
Power consumption can be measured, at various points in the distribution network, then trended and the resulting profiles can be analysed and optimised, in an attempt to minimise overall consumption. This sort of analysis also focuses the mind on equipment left running for periods, when it could switched off. Also some very large loads may only be operated when other loads have been turned off, to minimise the maximum demand.

Multi function digital power meters can show a wide range of parameters such as Amps / Volts / KW / KVA / KVAR / power factor / frequency / max demand / harmonics etc, but the size of the display is relatively small and all values cannot be seen simultaneously, when viewing the instrument, they must be browsed. At the computer, the display is much larger and most values can be viewed simultaneously. Analogue values can be displayed in the graphics as either a digital number, or an analogue instrument, or both, whichever is preferred.

Circuits with power meters can also have pre overload alarms set in the graphics at say 95% of full load current, such that an alarm can be raised to initiate manual (or automatic) load shedding.

Also, a lost volts condition can be detected and alerted using a power meter, providing the auxiliary supply is separate and secure, otherwise communications will be lost during the lost volt period.

There are many multi function digital power meters available on the market, and the accuracy of the low cost meters is usually around 2%, which is sufficient for general analysis but possibly not for tariff purposes. High accuracy digital power meters are available for tariff purposes at around 0.2% accuracy, and for use in the UK they may need to be Ofgem approved.

When metering at 11KV, Utility companies often set the meters up to compensate for errors in the CT's & VT's which feed them, to achieve the highest possible accuracy.

To read the second part of this article, visit
www.electrical review.co.uk or see the October 2008 issue of Electrical Review.

Backup power is an integral part of a company's operations,  providing support throughout maintenance activity and in an emergency. in addition,  the use of temporary backup power can often have financial benefits for businesses. Tommy Conway, a technical support manager from Aggreko,  looks at the issues around specifying backup power

The use of backup power is relevant for practically every industry and business, from manufacturing to data centres,  hospitals and  storage facilities. For  projects within these areas, the use of temporary power can have significant benefits not only for the electrical contractor but also for the client.

Maintenance support
With all its associated costs of labour, materials and downtime, maintenance can be a serious drain on the running of any business, particularly if it involves disconnecting the source of power, for example when working on a site's transformer or switchgear. However, the situation can be greatly eased with the use of backup power, which can provide a reliable source of temporary power and act as the utility provider to allow the company to continue operating throughout the maintenance period.

In addition to maintenance support, contractors can use temporary generators for vital system testing and in the commissioning stages of a project. Loadbanks can be used to check a company's own backup supplies, if they have UPS systems or onsite generators, for example. While it may be possible to conduct ‘live' loadtesting, where the mains power supply is literally switched off to check that backup systems kick-in, for some businesses such as hospitals and data centres  this form of testing will not be possible, as their systems or operations rely heavily on having a constant source of power. In these cases, loadbanks can be hooked up to the backup power supply to simulate a situation as if the mains power supply had failed. This will help to test the reliability of the support equipment, providing  clients with the assurance  that in the event of an incident affecting their power supply, they can continue to operate.

Some applications will need temporary power in the commissioning stages to demonstrate to the client they are fully functioning and to check they are in full working order before final sign-off of the project. In addition, some technologies, for example gas turbines and Combined Heat and Power (CHP) units, need ‘exciting' with a temporary power supply to help them start to generate their own power as part of the commissioning stage.

Capital avoidance
While electrical contractors can recognise the benefits of using backup power for temporary situations, it may not always be as easy for the client who has to pay the bill. However, temporary equipment offers businesses a range of financial benefits. It allows capital to be retained for core business activities, as the provision of  equipment over the short term  is often financed out of operating or maintenance budgets, which helps customers to avoid time-consuming capital approval processes.

In addition, payments can be budgeted on a monthly basis, which can be a significant bonus for companies when managing their cash flow. And because the situation is temporary, should circumstances change, the equipment can be easily returned with no obligation. Also, should it be that more power is required, an additional generator can be on site promptly.

Continuity planning
Power disruption is the fastest growing down-time threat to UK organisations, and time lost to such disruptions  increased by more than 350 per cent between 2005 and 2006*.  With this in mind, electrical contractors are well placed to educate clients on the benefits of contingency planning.  In fact, many do not know there is a British Standard around contingency planning.

British Standard BS 25999 was launched in July 2007 and is a code of practice highlighting what organisations must do to ensure their business continuity management systems are running effectively. By following such guidelines,  businesses can keep going during the most challenging and unexpected circumstances. It will also  protect staff and bolster the company's reputation.
In order to gain the standard, organisations need to have contingency plans in place to ensure that in the event of power loss, the business can keep running. One option is to devise a plan whereby temporary generators are kept on site to start up when power is lost. For certification, there needs to be a clearly structured contingency plan, with a document outlining the process of restoring power. Simply having a temporary generator on site is not enough to comply:  the generator needs to be maintained and serviced and contingency plans need to be implemented by a knowledgeable and experienced specialist company.

Installation options
There are two options available when setting up a generator, depending on whether or not the client can go without power for a very short period. If he can,  then it is possible to run a generator with an Automatic Mains Failure panel (AMF) which monitors incoming power supply from the mains grid. In the event this is disconnected, the AMF panel will start a standby generator. When the original supply is reinstated, the panel switches back to monitoring the mains supply and stops the generator.

With this set-up there are breaks both when the generator first starts and when it stops. This option is ideal as part of a planned maintenance programme, which can be conducted at periods of low production when the interruption is less critical or when the client knows their power is going to be disconnected.

Alternatively, if going without power is a major problem - which may be the case where it  affects manufacturing  processes and the quality of an end product; or in the case of  a data centre, where records and information could be lost - then it is possible to use generators that can recognise when there is no mains power supply and then take over. Zero synchronisation, as it is known, involves installing generators that continuously run, monitoring the electricity waves from the grid. The generator is synchronised to three phase 50Hz with the grid, so that having recognised there is a dip in power supply, it automatically takes over the load. This means the company can continue to run, minimising downtime and protecting any process that requires constant operation.

When specifying a generator, working with a specialist company is key. This is because with a generator - as with any other machine that provides power to a process - output needs to meet demand for it to work efficiently. Using a generator that is over-sized for the amount of energy required and working under capacity can cause just as many problems as a machine that is not producing enough power. It is necessary to consider the type of load demand of the premises - such as low power loads, leading power factor loads and total harmonic distortion (THD) - which can otherwise have a detrimental effect on switchgear, cabling and alternators.

As well as considering the size of generator required to meet the company's energy needs, it is important to plan the location of the generator. If, say, it needs to be situated close to the point of use, this may dictate the need for silenced canopied generators, which lower the noise level of the machine. Other important considerations include the specification of cabling and pipework - which carry the load to the point of use - fuel supply and compliance with the G59 regulations, which cover the use of generating plant running in parallel with the grid.
The use of temporary backup power provides a viable solution for so many situations that can threaten a company's operations. Whether during maintenance or to cope with power emergencies, it is a technology that electrical contractors should use to their advantage to help minimise disruption to their clients' businesses.

*According to research by SunGard Availability

Costly disruption and disconnection of consumers are typical consequ-ences of faults in power cables. Yet locating these faults is often difficult and time consuming. Fortunately, there are a number of test techniques available to make this task much easier. Damon Mount of Megger looks at the most useful of these

Power cable faults come in many guises. The easiest to locate by far are permanent faults on simple networks where the cable run is known, such as the supply system for a street lamp installation. That doesn't mean, however, that finding a fault is a trivial job. In fact, it can be enormously costly, especially for buried cables. Nowadays, digging a single hole in a street in a large city, for example, can cost well in excess of £100,000 and excavating a cable typically costs around £4m per mile. A better, more cost effective technique is to adopt a structured approach to diagnosing and locating cable faults, based on the use of modern test equipment.

The preliminary stage is straightforward - simply carry out continuity and low-voltage resistance checks to confirm the presence of a fault. Do not, however, succumb to the temptation of subjecting the cable to a high voltage insulation test at this stage. Doing so might alter the characteristics of the fault, and make it harder to locate with subsequent tests.

The next step is to attempt to localise the fault using a time domain reflectometer (TDR) and standard pulse echo techniques. This instrument applies a brief low voltage pulse to the cable under test and looks for voltages reflected back along the cable. Clear reflections are, in most cases, obtained from open- and short-circuit faults. By measuring the time it takes for the reflection to return to the instrument, it is possible to provide a good indication of the distance to the fault. It is always a good idea to store a reference trace before any further tests are done on the cable as any change in condition of the fault can then be seen by comparing live with recorded traces.

Dual-channel TDRs are particularly versatile, since they allow tests to be made simultaneously on two phases. The benefit of this is that a good circuit can be compared with a faulty one, which makes the results easier to interpret as joints and cable ends will also contribute their reflections to the trace. Some models, such as the Megger TDR2000/2P, can even test live circuits without the inconvenience of having to use loose, separate blocking filters

Basic TDRs are compact, inexpensive and very easy to use. They do have some limitations, but these low-cost instruments can find a high percentage of faults. They are, therefore, an excellent investment where the purchase of more sophisticated equipment cannot be justified.

It sometimes happens though, particularly in the case of high resistance faults, that the TDR cannot see the fault. Conditioning (burning) of the fault is one way to change the fault condition so that it can be seen with a TDR. This is sometimes necessary but requires another instrument, and is dependent on the cable type but can cause problems later in the fault-finding process.

A more sophisticated option is to move on to the arc-reflection method of fault location. This involves sending a high voltage pulse down the cable, which causes a temporary arc at the site of the fault. The arc is momentarily sustained by a filter built into the arc reflection test set.

Because of its low impedance, the arc looks like a short-circuit fault that can be localised with a TDR. The time interval between the high voltage pulse and the TDR pulse is critical if good results are to be obtained. For this reason, a modified arc reflection technique, known as arc reflection plus, has been pioneered by Megger.

With this technique, not one but fourteen TDR pulses are automatically sent along the cable at varying time intervals after the high-voltage pulses. The resulting TDR traces are recorded separately and, in almost every case, at least one of the traces will clearly show the distance to the fault.

An alternative way of localising faults that can't easily be seen with a TDR alone is the impulse current method. For this, the test set sends out a high-voltage pulse to establish a flashover at the fault, and the transient memory function of the test set is used to record the transients created by the flashover.

These transients travel back and forth along the cable with peaks that can be used to indicate the distance to the fault. In practice, the first reflected peak must be ignored due to the re-ionisation period, but the time interval between the second and third peaks gives a good indication of the cable length between the test set and the fault.

The techniques described so far all have one thing in common - they provide a measurement of the fault distance to the cable fault from the point of connection of the test set. Even if details of the cable run are known, this is sufficient information to determine the fault distance but not to locate the fault, as the cable rarely sits straight and horizontal in a trench or duct. In many cases accurate information about the cable run is not available. So a little further work is needed to locate the fault.

To precisely locate the fault position, a technique called pinpointing is used. This method of pinpointing faults in cables uses a surge generator - often known as a thumper in this application - to apply high voltage pulses to the cable. These pulses result in flashover at the fault location, which generates an audible noise - the thump. It also generates an electromagnetic field that can be detected by a suitable receiver.

Sometimes the thump from the fault is loud enough to be heard without any additional equipment but more commonly, especially with buried cables, a pinpointer is used. This is basically a sensitive ground microphone connected to an amplifier and headphones. The user simply moves the pinpointer along the cable run until the thumping is most clearly heard and the magnetic field is strongest. This should be the fault location. 

Faults with cables in ducts can be difficult to find, however, as the sound can travel down the duct making the listener less able to pinpoint the exact fault location. It is at least easier and less costly to replace a section of cable in a duct than dig up a direct buried cable. Although many faults in power cables are high resistance faults where the thumping technique is very useful, it's worth mentioning that not all cable faults will thump. Short-circuit faults for example do not flashover, so no electromagnetic field is formed and because the energy of the pulse is not dissipated in the form of sound, there is no thump to locate.
In this instance a TDR and a cable route tracer can be used to find the distance to fault, but locating the exact site of the fault is more difficult. This is why the low voltage tests are applied first, before conditioning causes a resistive fault that may flashover to become a short circuit that won't thump.

No one would claim that locating faults on power cables is easy but there are many types of test instruments now available that, when used in conjunction with a structured approach to fault location, will provide assistance in locating even the most intransigent of faults. The days of the black art of cable fault locating are past, because it is now too costly and too time consuming to go down this route. Since the faults themselves often lead to downtime and the associated consequential losses, money invested in the latest cable fault location equipment is money very well spent indeed!

Modern Methods of Construction (MMC) is the term  used to describe a range of technologies and processes, all of which are designed to aid the efficient and cost-effective construction of buildings. The MMC concept has received many accolades and much encouragement, not least in Sir John Egan's ‘Rethinking Construction' report which was produced for the government in 2001. Keith Ball and Tom France from Schneider Electrical Building Systems and Solutions investigate

Until now, MMC has largely been confined to the building fabric, and has been variously defined as off-site construction (OSC); pre-engineered building; system building; volumetric; modular; and - its original name - prefabricated construction.

Now, in a development that represents a significant and important shift within the electrical industry, Schneider Electric is applying the principles of MMC to electrical installations for buildings. Of the above definitions, those which most closely match Schneider Electric's MMC initiatives are offsite construction and system building.

However, the company's development of Preassembled Standards, which lie at the core of the company's MMC offer, are far more than just a way of simplifying electrical installations. For this reason, this paper is divided into two parts. The first deals with fundamental thinking about the design of electrical installations, the second with the provision of tailored, factory built, easily connected electrical system solutions.

Circuit design
For more than fifty years, the UK has been one of a very few countries to adopt a ring-main topology for the majority of electrical installations, rather than the radial topology favoured in most of the rest of the world. So firmly entrenched is the ring main system that few specifiers or engineers ever spend time considering its merits and demerits. As we shall see, there is a strong case for arguing that it is now time for them to start doing so.
Let's look at some of the facts behind this statement. By its very nature, a ring main delivers power from a distribution board or consumer unit to the loads via two parallel paths. There is an implicit assumption in the design of ring main systems that the current in the two paths will be more or less balanced.

To test the validity of this assumption, Schneider Electric carried out extensive tests in its own ASTA-accredited laboratory. A conventional ring main was simulated with all of the socket outlets loaded, and the current in each of the two circuits linking the sockets to the power source was carefully monitored.

The results were surprising. Relatively small changes in the impedance of the wiring were all that was needed to produce a large imbalance in the currents. In fact, ratios of up to 2:1 could be produced under conditions that could easily be encountered in a real installation.
Does this matter? It certainly does, because the heating effect in the path which is carrying the larger current is much greater than might have been expected. In fact, tests show a standard 2.5mm2 PVC-insulated cable used in a ring main circuit protected by a standard 32A MCB can generate as much as 25% more heat than a similar cable used in a radial circuit protected by a 20A MCB, the loads being equal.

Almost certainly, this additional heating will be insufficient to create a short-term hazard but it is nevertheless significant, as we shall see shortly.

Now let's look at another aspect of ring main circuits protected by standard 32A MCBs which comply with BS EN 60898. It would be easy to think that the maximum total current which could flow in such a circuit for other than a very short period of time would be equal to the nominal rating of the breaker - that is, 32A. In fact, this is far from correct.

A reading of the standard will reveal that an MCB can carry a current of up to 1.45 times its nominal rating for up to an hour without tripping. So, in our ring main protected by a 32A breaker a current of up to 46.4A could flow for as long as an hour. This is clearly undesirable, especially when considered along with the potential for current imbalance discussed earlier.
The principal result of the shortcomings we have identified in relation to ring main systems is additional cable heating. Again, does this matter? Emphatically yes, as operating temperature has a large effect on the working life of cables.

This is an aspect of electrical installations that is rarely considered, but it certainly deserves closer attention, as figures provided by NICEIC reveal. These show that standard PVC cable conductors operating at 70ºC have a dependable working life of 69 years based on an eight hour usage day.

That may be acceptable. But if the temperature rises by just 5ºc, the life of the cable is halved to around 37 years, which is less likely to be acceptable. In fact, if the operating temperature of that cable conductor should reach 100ºC, its life will be just two years.
It's tempting to think that such high temperatures would never be encountered in practice but, before making this assumption, it's important to remember that, in their construction, modern buildings make extensive use of materials with excellent thermal insulating properties. Cables embedded in such materials can show remarkably large temperature rises.

Let's recap on the issue of radial versus ring main topologies. Ring mains, as we have seen, can have higher cable temperature rise characteristics. With radial circuits, the maximum potential temperature rise is lower, because the protection is provided by a 20A MCB rather than a 32A MCB, and it's also much more predictable, because there is no uncertainty about how the current will divide in the cabling.

If ring main topology is a rather poor technical compromise, surely this is offset by its cost benefits? In fact, this is another proposition that is difficult to support.
Ring mains can, of course, support multiple sockets, which suggests that they are economical in the amount of cable required. When they were first introduced, this might have been true, as far fewer electrical appliances were in use, which meant that the chances of all, or even most of the sockets on a ring main circuit being used simultaneously was slim.
Today, the situation is very different. Not only are all the sockets likely to be used, there's a very good chance that some will have extension leads plugged into to provide even more socket outlets.

It ‘s also necessary to bear in mind that, in line with the 16th Edition of the IEE Wiring Regulations, radial circuits can feed more than one socket. In fact, multiple sockets per radial can be taken as a realistic figure for modern installations. When these factors are taken together, the apparent cost benefits of ring main installations disappear.
These considerations lead to the inevitable conclusion that ring main systems are technically inferior and that they offer no cost benefits. There can, therefore, be very little argument in favour of their continued adoption in new electrical installations.

Equipment pre-assembly
The superiority of radial wiring topology is reflected in the design of the products developed in line with the principles of MMC. Essentially, these products centre around factory-assembled distribution boards and consumer units, which are delivered to site ready for immediate use, and which use plug-and-socket connectors for connections to external circuits.

The products are individually configured at the factory to suit the user's specific requirements. They can be supplied with incoming connectors rated at up to 63A and outgoing connectors rated at up 20A. They are, therefore, ideally suited for use in installations where a radial topology has been adopted for power distribution. To ensure maximum versatility, the boards can also incorporate other protective devices such as RCCBs and RCBOs along with simple control circuitry.

The boards and consumer units are, however, only part of Schneider's MMC solution. Junction boxes and sub-distribution boards, all with tool free connectors, are also available, as are pre-wired socket outlets.

The socket outlets are fitted with a cable of user-specified length, which is terminated in a tool free connector. This means that, on-site, the installation of power outlets involves no more than mounting the socket, running the cable to the nearest distribution board or junction box, and plugging in the connector. No conventional wiring is needed.
This approach offers substantial benefits over the traditional practices of assembling consumer units and distribution boards on site, and carrying out wiring on an ad-hoc basis.
Among the most significant of these benefits are the large reduction in the amount of costly on-site labour required, and the big reductions in overall time needed to complete the installation work. Indeed, on beta test sites for the new system, which include major school projects, time savings of up to eight times have been achieved.

Another less obvious but equally important benefit is the reduced reliance on skilled labour. All of the elements making up the system are not only supplied pre-assembled and wired, but also factory tested. This eliminates the risk of errors such as fitting MCBs with the wrong ratings and means that the new system is, for all practical purposes, plug-and-play.
As no conventional wiring is used, the level of electrical expertise needed to use the system successfully is comparatively small. With shortages of experienced electrical contractors currently being widely reported, this is a benefit that can only be expected to increase in significance.

All of the equipment included in Schneider Electric's pre-assembled standards range is, as its name suggests, custom assembled from standard products to meet the user's precise requirements. Since only standard products are used in the assembly, and efficient streamlined manufacturing techniques are employed, delivery times are short and installed costs are very competitive.

Pre-Assembled Standards extend the benefits of MMC, which have for so long been available only in the major constructional elements of building projects, to electrical installations. Suitable for virtually all power and lighting applications in healthcare facilities, schools, offices and other public or commercial buildings, they are already helping users to deliver solutions which combine technical excellence with convenience, flexibility and competitive pricing.
Further information is readily available. Schneider Electric welcomes the opportunity to consult and advise on MMC at an early stage in any project. Why not take advantage of this free service to discover advantages that Pre-Assembled Standards could provide in your next project?

With the increasing demand for ‘safe' buildings, more attention is being paid to the types of cables being installed, and the potential risks in the event of fire. It is now recognised that smoke and poisonous fumes are often a far greater risk to life and property than the fire itself says John Herbert of FS Cables

The main danger in a fire is often the smoke produced by combustible material - the fumes pose a huge threat to both people and property. The Kings Cross fire of 1987 still acts as a sobering reminder of the dangers of fire breaking out in enclosed spaces. At the inquest into the Kings Cross fire, many people were found to have been overcome by toxic smoke rather than injured by the flames.

London Underground has since banned halogenated cables from its underground stations following concerns about a repeat of the tragedy. Kings Cross station is now used by over 100,000 passengers every day and in the event of fire safe and fast evacuation is a challenge.

The main problem facing specifiers is the confusion over terminology and standards. Is LSHF better than LSOH? Is LSF the same as LSZH or RP? These terms are all widely used within the cable industry.

PVC: problems and perils
Standard PVC is made up of a significant number of halogens which are normally very stable but, when burnt, separate and give of toxic gases in particular hydrogen chloride (HCl). Hydrogen chloride is extremely dangerous and corrosive, and is in fact similar to mustard gas used as a chemical weapon.

These halogenated gases form highly corrosive acid when they come in contact with water - either moisture in the air, fire sprinkler systems or even moisture in the eyes or lungs of people. It is clear to see the devastation that can be caused by burning PVC in the event of fire. 

The hazards of hydrochloric acid depend on concentration. Hydrochloric acid in high concentrations forms acid mists. Both the mists and the solution have a corrosive effect on human tissue, potentially damaging respiratory organs, eyes, skin and intestines.
Additionally, the hydrogen chloride given off also reacts with the many other additives present in PVC creating even greater volumes of toxic fumes.

The damage caused by burning PVC is two-fold; firstly, dense smoke will obscure exit routes with fumes choking people. The second and less recognised problem is that the acid gas produced in the fire permeates electronic equipment, settling on and corroding printed circuit boards and over a period of time can cause random, unpredictable failure.
This won't just affect computers, it will also damage security/access control equipment, building management systems, lifts and just about anything else with a circuit board. The fire may have been extinguished within minutes with no great risk to life but the damage to equipment may be colossal.

IBT (Intelligent Building Technologies) such as PA systems, evacuation systems and CCTV networks are becoming more and more common in airports, train stations, hospitals and other places that can be difficult to evacuate, as are systems for handling data for diagnostics.

As heightened security becomes an issue in public places, particularly airports and train stations, there is a need for critical systems to continue functioning in the event of fire. In the event of a fire, the high performance cable connecting these networks needs not only to be LSHF, but also carry on functioning to allow the safe monitoring of evacuation routes without putting additional lives at risk. LSHF cables in themselves do not offer circuit integrity, and this is an important distinction. Cables specifically designed to survive in the event of fire need to be correctly specified. Fire resistant cabling for safety dependent or critical systems is another topic entirely and worthy of its own article.

Reducing the risk - the options
There has been a shift in recent years to using newly developed compounds that emit less of the harmful gases, particularly halogens, but still perform well in other respects.
The cheapest alternatives are modified PVC's - these are termed RP (Reduced Propagation) or in some cases LSF (Low Smoke and Fume). The difficulty for the cable buyer is that there are no specific standards for LSF cables. Ordinary PVC emits approximately 28% HCl, whilst modified PVC could give off a massive 22% HCl and still be sold as LSF.
If you want to be absolutely certain of what you are installing you should insist on a cable that uses insulation and sheathing materials that do not emit any Halogens and have reduced smoke emission properties. These are termed LSHF (Low Smoke Halogen Free), LS0H, LSZH (Low Smoke Zero Halogen) or sometimes OHLS (Zero Halogen Low Smoke).
These products must emit no more than 0.5% HCl. This is achieved by using materials such as polypropylene which don't produce the same gas or acid emissions when burnt.

Poisonous gases
Also, don't accept standard PVC cables over-sheathed with an LSHF jacket or cables with PVC insulation. When the jacket burns through, the PVC inner sheath or insulation will give off poisonous gases in just the same way as if the LSHF jacket wasn't there!
Another common misunderstanding is that LSF or LSHF cable is also flame retardant. This is not necessarily true. The cables may spread the fire even though minimal fumes are being emitted. In mainland Europe, polyurethane is popular as it emits very low levels of smoke and fumes. Unfortunately in its standard form it burns ferociously and can drip burning material onto anything below with the potential to rapidly spread the fire. There has been a recent move towards flame retardant varieties known as FRNC (Flame Retardant Non-Corrosive).

Counting the costs
As with most developing products, the durability of new safer compounds is improving all the time with cost penalties reducing as the market grows. LSHF compounds are approximately 2 - 3 times more expensive than PVC and many are considerably slower to extrude, with resulting production costs being substantially greater. Combine this with the much smaller demand for LSHF cable and you can begin to appreciate why they cost more.
However as the market grows the prices will fall. Standard products such as conduit wiring 6491 and booklet-armoured cables are now more readily available in Low Smoke Halogen Free versions than PVC in some areas.

Why confusion occurs
To add to the confusion, some power cables, in particular BS6724, are LSHF. However, some manufacturers class and even print them as LSF. This also extends to some BS5308 cables.
Great caution is needed when buying or specifying data cables particularly American or European. Belden style data cables are now widely used in buildings for security, access control and building management systems.

Specifying - the guidelines
First and foremost be sure to get written confirmation that the cable is halogen free, which means both insulation and sheath. Don't accept terms like LSF as they can be meaningless. Also confirm the availability of the product and take into account the manufacturing times and minimum production quantities should it be a non-stock item.
Contractors are increasingly being asked to complete jobs within a month, when the production time to make the cable may be six to eight weeks or longer!

Appropriately specified, most of the popular types are stocked in Low Smoke Halogen Free alternatives, manufactured to extremely high standards but with none of the risks associated with standard PVC cables. A specialist distributor should be able to provide the product with the appropriate certificate of conformity.

The price of LSHF cables is higher than standard PVC, but as more people are specifying PVC free alternatives the price difference is shrinking.

The ultimate LSHF non-combustible cable with a tough but highly flexible jacket with good ageing characteristics and resistance to water, oil and solvents is still to be developed. However with careful selection the most important factors can normally be catered for.

In industries where a clean and sanitary working environment is essential such as the food, beverage and processing industries, a strict hygienic protocol needs to be adhered to in order to prevent product contamination. In the constant battle to prevent cross contamination, which could have a disastrous negative impact on an organisation such as product recalls, reduced profits, tarnished reputations and loss of consumer confidence, daily washdowns of all equipment is paramount to protect product purity and quality. Glen Ward of Rittal explains

A daily washdown includes the enclosure housing the electrical controls to remove any particles that may be cultivating on the enclosure surface, crevices or recesses. Protecting the electrical equipment from daily washdowns while maintaining hygienic standards can prove to be a ‘hygienic headache'. Common problems that occur during the daily washdowns include solution pooling, the possibility of trapped contaminants between walls and mounted enclosures as well as the unreachable areas created by floor standing enclosures. Hygiene checks have also revealed that the use of pressure washes harbours the risk of organic contaminants entering niches and tiny recesses in standard enclosure designs such as the two-bit lock, hinges, seals and glands. However, these problems can be easily overcome if during the design phase the enclosure is properly specified.

To prevent any pooling from collecting on the roof area, an enclosure that incorporates a 30° sloped overhang allows cleaning fluids to completely drain away as well as stopping objects being placed on the roof which could potentially cause a contamination hazard. Ideally the slope at the back of the roof should be raised at an 8-20° angle over the door by 10mm to prevent liquids from reaching the door and seal. An increased gap between the door and the roof will offer easier cleaning and an bezzled door return will ensure that fluids do not run back and take residence on the seal.

A special silicone door seal should also be fitted - designed to protect against acids, alkaline solutions, detergents as well as disinfectants, and ought to have chamfered edge folds to prevent any liquid accumulation. The seal should be of a coloured variety to improve the visibility of particles that are then detectable with metal detectors. As the seal is subjected to a constant barricade of water the seal will need replacing on a regular basis. A one-piece replaceable seal is ideal as it is quick and easy to install as well as being gap free eliminating the possibility of bacteria forming within the small joins.

When it comes to the two bit locking mechanism, it was always difficult to tell if the recessed hole had been cleaned out completely. The solution has been to design a new hygienic lock that protrudes from the door surface, which contains no recesses eliminating the places where micro-organisims could fester while offering more reliable cleaning. The hinges on enclosures have also continued to provide a bacterial haven with the pin through the middle making it virtually impossible to keep hygienically clean, hinges that are mounted inside the seal remove it from the external environment therefore eliminating the potential hazard.
An area, which has until recently caused problems, has been the use of the traditional cable gland that has a number of design features making it unsuitable for hygienic environments, such as open screw threads and tiny recesses. To rectify this Rittal has introduced a new hygienically designed cable gland, which minimises the risk of deposits found in ‘open' production processes. Conventional cable glands contain various cavities and crevices where dirt and bacteria can gather; the new cable gland presents only smooth surfaces and gentle transitions, so dirt and micro-organisms have nowhere to congregate. A special feature of the new cable gland is the cap nut that extends all the way to the mounting surface, thereby concealing the entire clamping and sealing mechanism.

The mounting of the enclosure to avoid entrapment areas also needs careful consideration. Difficult to clean areas with floor standing enclosures can be eliminated by using adjustable levelling feet, with tubular threads, which support the enclosure while accommodating the floors drainage slope. For wall-mounted enclosures, tubular mounting brackets with a smooth finish will minimise entrapment areas. Open frame plinths with a clearance of 300mm designed from tubular stainless steel will also allow easy cleaning.

Enclosure mounting, seals, gaskets, and gland plates can also affect the IP rating and can often make the difference between the success and failure of the enclosure to meet its desired task. Typically, the more hostile the environment the enclosure is to be situated in, the higher the IP rating will need to be. For internal use where there is no likelihood of the enclosure being washed down, the IP rating could be as low as IP43. However, in an extreme environment, where the enclosure is subjected to a daily washdown, the internal equipment will need protection any form of water ingress so an IP69K enclosure will be required.

Established in 1993, the IP69K protection rating which is currently the highest available, was designed to address the high pressure, high temperature washdowns of road vehicles. As the cleaning method for these vehicles was quickly adopted by other industries, the IP69K enclosure was formed. When strong, high velocity hoses are directed at machinery and their controls to remove any remaining substances, it is important to protect the electrical controls, and if the enclosure were only rated at IP66 it could quickly turn to disaster. For example: the temperature in a processing factory could be around 10°C ambient when in use, but when the cleaning process takes place the refrigeration is switched off allowing the temperature to rise to 20°C. The water temperature for high velocity cleaning is often higher than 50°C and can have a water pressure of 70 bar. As the water temperature is higher than that of the enclosure and the pressure is greater than the design standard of the gaskets, the enclosure would soon begin to fill with water.

IP69K enclosures are subjected to a rigorous test before they receive their certified rating. The test consists of: water pressure up to 100 bar, 14-16 litres per minute flow rate; temperature up to 80°C; distance minimum of 100mm to a maximum of 150mm. The duration of the test calls for four directions and test jet times of 30 seconds each at an angle of 0°, 30°, 60° and 90°.

So how is IP69K different from UL Type 4? IP69K and UL Type 4 standards both require the enclosure to protect against the entry of water, but Type 4 test is mainly concerned with hose down conditions involving lower pressure water at a greater distance (10-12ft) and with a greater volume of water (65gallons/minute).  IP69K certification requires close range, low volume with very high pressure, which is similar to the type of washdowns found in the pharmaceutical, petrochemical and food and processing industries. IP69K is therefore an important standard for enclosure systems used within any environment where the equipment is subjected to high pressure cleaning.

Every industry faces its own challenges and the food and processing industry is no exception. However, the latest hygienic thinking has now been applied to the electrical enclosure packaging field, which can significantly reduce the contamination risk, facilitating in this constant battle. These new developments allow greater system availability, more efficient cleaning and lower energy requirements due to the reduced use of chemicals. With careful consideration when choosing an enclosure, a lot of the common problems in hygienic environments can be easily overcome.

Bill Earlie, of test instrument and precision measurement company Cropico, explains the implications of new guidance on electrical installations in medical environments

New Medical Electrical Installation Guidance Notes (MEIGaN) have recently been issued on the safety requirements of electrical systems installed in diagnostic imaging, patient treatment and radiotherapy rooms.

This guidance has been issued for new buildings, refurbished rooms and transportable diagnostic or treatment rooms in medical or health premises. The notes stipulate a range of measures to be taken in relation to the electrical mains supply and include new instructions regarding the earthing and equipotential bonding connection of permanently installed medical devices and associated equipment.

Developed for healthcare organisations and medical device suppliers, the new MEIGaN guidelines embody the basic principles of the BS7671 IEE Wiring Regulations, but refine this with specific requirements for medical environments.

Earthing & equipotential bonding 
Many electrically operated medical devices and equipment including sterilisation baths, heaters, treatment tables, drug cabinets and some lighting fittings can have exposed metalwork that could become live if a fault occurred. Anyone touching these surfaces could then receive a shock or even be killed depending on the current flowing through them to earth.

Equipotential bonding is therefore necessary as part of the safety measures associated with electrical installations to prevent significant touch voltages being generated within the patient environment.

MEIGaN requires earthing and equipotential bonding conductors shall not intentionally carry load or control circuits. In addition, it is stipulated that equipotential bonding conductor continuity between equipment and the associated mains supply isolator(s) shall not depend solely on the continuity of conduits, cable braiding, ducts or trunking and should be achieved with a dedicated copper earth cable connected with brass or copper fittings.
An earth reference bar (ERB) is required in medical a room that comprises one or more copper connection bars installed in an enclosure as part of the room's protective earth system. The ERB is designated as a reference or datum point for the purpose of defining and measuring resistance values.

All installed equipment needs to be earthed to the ERB if there are any conductive surfaces that are accessible to either patients or staff. This could include warning lights, injectors, water baths, contrast media warning equipment, viewing boxes and powered drug cabinets.
All non-powered equipment with metal surfaces must also be similarly bonded to the ERB. This includes protective screens, metal sinks and work surfaces, heating pipes and radiators, water pipes, drug cupboards, ceiling mounted hardware and other steel or wire cable trays, steel floor ducts and similar hardware. In all cases, such items must be returned to the ERB by means of a cable.

Each equipotential conductor connected to the ERB must be individually labelled and permanently identified. A typical ERB layout is as shown below (with black alligator clips of leads from test equipment).

Testing and verification
MEIGaN requires earthing and equipotential bonding connections are inspected and tested to verify compliance with the new guidance.
It advises resistance should be measured between each protective earth terminal, socket outlet or every accessible metal part and the ERB.  In terms of bonding resistance, the maximum acceptable resistance is 0.1Ω (or 100mΩ). Anything above this level would represent a failure of the earth continuity provided.

As a point of caution MEIGaN points out with the testing of socket outlets, care must be taken to ensure that the contact resistance of an inserted earth pin of a 13A plug should also be low. This is because there can be some variation in the resistance of plug pins, which could be manufacturer dependent. For this reason it is suggested the socket resistance is tested to the back of an inserted pin and not by probing the socket itself.

There has also been much debate about the current and voltage levels that should be used for this test. Traditionally the standard instrument used for equipotential bonding was a mains powered unit capable of supplying up to 35A at up to 25V for a 5 second test.
However, some modern electronic medical equipment could be susceptible to damage by large earth current pulses, especially on PCBs. In addition, the 35A, 5 sec test does not necessarily fuse frayed connections as easily as one might think.

Tests have shown a single strand of earth flex can withstand the test, so it is not in itself a reliable measure of ‘robustness'. Hence, testing at lower currents is not necessarily a weaker test that would miss potential failures.

The new MEIGaN guidelines appear to have taken these sort of considerations into account and now stipulate that a minimum test current of 1A can be used to test the equipotential bonding.

In doing so the new guidance means highly effective testing of the earthing and equipotential bonding of medical devices and fixed equipment in a treatment room or diagnostic suite can now be undertaken with lightweight, hand held digital microhmmeters.
One new example, the Cropico DO4002, has been specially developed for this application.
This instrument utilises forward and reverse current measurement with auto averaging to maintain highly accurate measurement of very low resistance. It also has the advantage of battery power which means equipotential bonding measurements can be taken without the risk of earth leakage currents from the main power supply interfering with resistance values.
In addition, the tester can be used with extended test leads of up to 20 metres without any loss of measurement accuracy, making room socket tests easily accessible and enabling individual plug tests can be undertaken fast and effectively.

Maintaining the integrity of electrical integrity in medical environments is critical to prevent patients being put at risk. The availability of new hand held test instrumentation enables electromedical service and installation engineers to meet this need by helping them undertake earthing and equipotential bonding testing quickly and effectively - without compromising the accuracy of test results.

Largely regarded as an everyday consumable for electrical contractors, you could be forgiven for choosing price over quality when it comes to cable glands. How different could one gland possibly be from another? The answer is dangerously different. With cheap, substandard imports flooding the market and no industry body regulating them, there is a growing need to raise safety standards in this area. Here, Clive Haley, category manager for Newlec cable management at Newey & Eyre explains the real cost of buying inferior cable glands

With safety still very much a top priority on the public agenda, the electrical industry has been hit by a raft of legislation in recent years to raise standards within the sector. Part P of the Building Regulations was introduced in January 2005 to reduce the risk of death and injury caused by electricity or fires started by faults in electrical installations, which account for 30 per cent of all electrical accidents. More recently, the 17th edition of the IEE Wiring Regulations (BS 7671:2008) has been introduced, comprising of an even stricter regulations book that extends to over 400 pages.

Despite an array of rules and regulations permeating the industry, there is still one product area which can significantly impact the quality of electrical installations and yet continues to slip through the safety net - cable glands.

Although the British Approvals Service for Cables (BASEC) has been set up to approve and monitor cable standards, there is still no such industry body for glands, leaving them vulnerable to poor quality products. Following the recent surge of cheap, foreign and potentially highly-dangerous imported cable glands into the UK market, this should in itself present a massive cause for concern. Surprisingly then, there is still a commonly held belief in the industry that cable glands aren't really that important.

Unaware or unconcerned these products are covered by European legislation, meaning supplying any that do not comply with the relevant standards is punishable by large fines or even imprisonment, some wholesalers are supplying these cheap imports to be more price competitive.

Worse still, some contractors are often too busy concentrating on high value items such as cable, to focus on the quality of the cable glands. Many assume when it comes to cable glands, ‘brass is brass' and all products are seemingly the same. In reality however, the difference can be quite astonishing.

To understand why the price of this low cost item can vary so immensely, we need to look at the wider picture. Being a globally traded commodity, the cost of quality extruded brass; the predominant component of cable glands, around the world is similar. Therefore, to get around this level playing field the very low cost products are generally manufactured from what is known as ‘honey' brass - melted down scrap, mixed with other materials and re-cast into lengths to be worked on by manual machines. While good quality brass is a strictly controlled alloy of mainly copper and zinc, in proportions detailed in EN12168, this ‘honey' brass typically has a poorly controlled amount of other metals and impurities. This means that although the resulting metal has a deceivingly ‘brass-like' appearance, its properties and performance will be very different to true brass.

With the primary factors affecting the safe performance of cable glands being the integrity of their mechanical design and the quality of materials used in their production, the inferior and impure way in which these recycled brass versions are produced undermines the design strength of the product, which in turn carries massive implications for the integrity of an electrical installation.

Concerns surround the quality of brass being used to manufacture the glands. Brass can be affected by exposure to salt water and certain chemicals and the result is that some of the zinc leeches out of the alloy, a process also known as de-zincification, which can reduce the strength of the gland. While glands made from a true brass alloy are strong enough to withstand any reduction in strength (and can be nickel plated if the lifetime exposure is expected to be extreme), those made using low grade brass are much less able to withstand the de-zincification process. They can become brittle and break, or can become detached affecting the earth continuity, both of which can cause an installation to completely fail. Furthermore, because they are typically manufactured with the minimum amount of metal in them, the range of armour sizes that they can grip is usually less than a good quality gland and there is a high risk of shearing threads when tightening them.
Other problems with these cheap imports include the degradation of seals over time. Sealing materials can vary greatly in their ability to withstand attack from airborne pollutants and environmental elements, and an effect known as ‘compression set'. This is where the seal material is compressed for long periods. If it suffers from compression set then it will eventually take up its compressed shape, which means that it is no longer exerts a sealing force against the cable. While reputable manufacturers will have tested their seals to prolonged exposure, inferior products made using low grade materials are more prone to compression set and can become weak, especially when installed outdoors, making them liable to fail.

In addition to the various safety implications of failed electrical installations, there are also return visits for maintenance for the contractors -  due to the difficult nature of locating them, replacing failed glands can take anywhere up to half a day's work to repair. In addition, there is the inconvenience inflicted upon the end-users.

Another consideration is liability. In a society which is ever more driven by a ‘blame culture', traceability is increasingly important. Should poor quality products be to blame for an accident or fatality, the consequences will be serious, as ultimate responsibility lies with the contractor, rather than a product which was ill-chosen for the application - not a good recipe for business success in an industry where reputation is everything.

Unfortunately, a visual comparison of cable gland products will reveal very little difference in quality, which is why control is difficult. This is why specifiers should verify the quality of a cable gland by confirming it (or its packaging) is CE marked, stamped with the manufacturer's name or logo and sourced from a reputable manufacturer. It is illegal to supply product without the CE mark and if the manufacturer is not identified any traceability ends with the installer or supplier.

Based on the European standards, principally BS6121 and BS: EN 50262, most premium manufacturers use the latest techniques to ensure that cable gland products reach installers in peak condition and offer superior performance. In meeting the tests contained within the standards, these glands ensure a sufficiently robust design; able to withstand continuous shearing forces at the point of entry into the product, and that the cable is adequately retained by the gland's seals and/or armour clamp.

Going forward, a more serious approach to cable gland specification needs to be adopted. It is no use paying careful attention when selecting the high value products for installation and then undermining the safety of the entire project by overlooking cable glands quality. Cable glands form part of a system and the wrong choice of product can result in the whole system failing, not to mention the incalculable damage to an installer's reputation and the cost of repairing the actual job. Only by assessing the quality of their cable glands can contractors fully and confidently guarantee the quality of their work and protect themselves and their business.

Newlec offers a wide range of quality, fully tested, CE marked cable gland kits produced by a British manufacturer. All Newlec cable glands are made from brass manufactured to comply with EN12168. With over 20,000 product lines in stock at any one time, Newey & Eyre holds more major brands than any other electrical wholesaler. The company is also well known for its specialist expertise and ability to quickly source rare or unusual electrical items from around the world.

The cables sector which provides the main electrical supply is undergoing a series of changes with revised standards, new installation approaches and even new elements in the make-up of the cables themselves. Here, Dr Jeremy Hodge, Chief Executive of the British Approvals Service for Cables, assesses the shifting issues

The power cables market - not traditionally the most high profile of the various sectors of the industry - has been developing steadily while market conditions have changed, new specifications and installation methods are adopted, and new and revised British and international standards are introduced.

The most significant drivers in the power cable market have been the setting of higher specifications by building designers - especially to address fire safety concerns - volatile commodity prices affecting the cable supply chain, and increasingly global trading in cable products.

The rise in the price of copper, which is the major cost component of power cables, has led many buyers to review their purchasing patterns and to look further afield, but some of these cables have demonstrated quality problems.

In some cases where physical size and flexibility are not a problem and where permitted in the standards, aluminium cables may prove to be a good option, although there remain some performance and usability concerns, such as with crimped terminations.
Two of the most commonly-used types of armoured power cable, PVC-sheathed to BS 5467 and low smoke to BS 6724, have recently been updated to incorporate the latest material specifications. The opportunity has also been taken to make the requirements on core and sheath colours more flexible to reflect the wider range of geographies and jurisdictions in which these cables are now being used.

The cables both use cross-linked polyethylene (XLPE) as the insulation material around the conductors, which offers several performance advantages. Armoured cables using PVC or other traditional materials, such as to BS 6346, are becoming less and less specified.

Fire Safety
With increasing expectations from fire safety legislation and concerns over liability, engineers and designers have been changing the cables they specify. Increasingly, the move is away from traditional cable sheathing materials like PVC towards Low Smoke Halogen Free (LSHF) construction.

Standards for these types of cable include requirements for testing smoke emission and the production of acid gases, and specifiers should check that these tests have been done if the cable does not carry appropriate approvals.

Fire resistant cables are also developing, with the recent publication of a new fire test for larger cross-section fire-resistant cables. For example, BS 8491 specifies an additional fire test that simultaneously applies flames at 842 ºC, direct mechanical impact and direct application of a water jet, simulating fire fighting conditions. Three ratings are possible for fire survival times of 30, 60 or 120 minutes - the latter being particularly suitable in cases where fire fighting services such as smoke extract systems will be used for an extended period. Cables which may pass this test include various special designs based on BS 7846 and other standards.

Mineral insulated cable, however, remains probably the best all-round performer for fire resistance, and is available in a wide range of sizes starting at the very small. It is used for fire alarms, detection equipment and emergency lighting where there can be no compromise, especially in large public buildings such as hospitals, schools, shopping malls and airports where large numbers of people may move about.

The risk of anything going wrong is greatly reduced because of its key features, namely its ability to withstand high temperatures up to the melting point of copper at over 1080 ºC, its ability to continue power and data transmission even after significant damage, and its reduced need for maintenance.

However, many fire alarm and emergency lighting installations have changed to use soft skin fire performance cable to BS 5839-1 and BS 7629-1, because of the relative ease of installation and the overall cost of the installation.

Installation
The installation of power cables on many projects is changing in that the installer is increasingly being expected to take care of both the medium voltage (e.g., 11kV to BS 6622 or BS 7835) cable from the utility supply and the low voltage power distribution cables around the building or site. In essence, this is quite a major step.
It requires the contractor to acquire further knowledge of this type of installation, a specialist area in its own right. Indeed, further training on medium voltage working and jointing may be required and is advisable to ensure best practice is applied. Even though jointing equipment is similar to low voltage, higher-rated products must be used and closer co-operation with the utility is needed.
Although standards for many types of cable have been harmonized at the European or international level, those for power supply cables remain closely linked to national regulations, guidance and practice.

Harmonics
Another issue which has an implication for cable choice is power harmonics. As more complex electrical loads are being used in buildings, for example computers and UPS systems, more installations are becoming prone to the effects of harmonics, which can result in overheating and other complex effects.
These problems are often difficult to investigate; they can occur in fully compliant cables and often mimic other faults such as low conductivity.

Power system designers need to be aware of the potential and if necessary apply alternative design approaches such as larger sized neutrals in three phase systems, in order to minimize or avoid the problem. Harmonic filter systems are available should the problem not be addressed at the design stage.

Approvals
One of the most serious problems for any project manager or installer is a batch of faulty cable. Project delays and the cost of replacement are unwelcome.
It is unfortunate that some buyers still take at face value the claims of compliance made by some manufacturers or traders of cable, without checking that compliance has been demonstrated.

Many non-approved cables have not been subject to the required tests and one of the early signs to recognising potential problematic cable is a product with few markings or marked with only a standard number. This should be treated with caution. It is possible that nobody independent of the manufacturer has examined that cable and the claims made may be unreliable.

Faulty cables have always been an issue but never to the extent that they are today. The source of much of it appears to be the rise in copper and other material prices which may have tempted some cable manufacturers to cut corners and use less copper or cheaper polymer materials in the manufacturing process. Drawing down the diameter of the copper wire too much has the effect of reducing conductivity, and cables with insufficient conductivity may overheat and cause fire or offer a reduced level of safety against electric shock. Cable standards specify the minimum conductivity required.

More recently we have also seen examples of materials other than pure copper, such as steel wire, copper-coated aluminium or badly recycled copper in cables that should be made from pure copper.

Poor quality insulation or sheathing material may result in insulation resistance problems on testing an installation, or they may have unacceptable fire or smoke performance.
It cannot be stressed enough that there is a need to move towards greater compliance in the purchase and use of approved products for now and the future.
For the power cables market, doing the simple things well in these changing times would ensure safe installations using quality products that are fit for purpose in an area of high importance for the short and longer term.

As news reports dwell upon the difficulty of procuring major utility power supply, the need for overall power efficiency has moved into the centre ground and with it prominent sources of consumption are therefore brought into focus. Shri Karve of APC by schneider electric explains

The ‘white space' of a datacentre has been identified as a particularly acute consumer due to the mission-critical nature of IT services, but it is not the only space that commands attention.  ‘Grey space', which houses the electrical switchgear and plant of critical facilities such as hospitals, transportation hubs, commercial and industrial premises entails equally catastrophic risks of failure.

In these situations uninterruptible power supplies (UPS) are required for protection since an interruption lasting no more than a fraction of a second can devastate operations and in some cases, threaten life. The consideration holds true that the greater the degree of mission criticality, the greater the need to avoid downtime, the more complex the deployment of UPS, and therefore the greater the emphasis on achieving high efficiency and reducing waste without compromising availability (resilience). In today's operational climate, no source of efficiency or saving can afford to be overlooked.

With UPS designs in general becoming more reliable, APC suggest that efficiency in terms of energy consumption mainly, but also in respect of footprint and skills, should become the major selection discriminator. The task however, is to understand how efficiency is being quoted by manufacturers, as each will no doubt quote a figure which presents their system in the best possible light. The reality is that under operating conditions, advertised levels of efficiency may never be achieved for a variety of reasons, primarily that efficiency claims are usually made on the basis of a higher loading than is normally faced due to redundant design concepts.

APC highlights a multi faceted approach to enable efficiency strategies to be introduced which are appropriate to individual applications, for example in white space where loads are dynamic, scalable systems are key to ensuring that IT is adequately protected without the energy wastage associated with over-sizing of infrastructure. In grey space physical size and operating efficiency may be essential to ensuring economic operations and low total cost of ownership (TCO) independent of loadings.

To this end, APC by Schneider Electric has recently launched the MGE Galaxy 7000 range of three phase UPS which are designed to offer the highest efficiency as well as the highest power/ footprint ratio unit in its class. The series joins APC's Symmetra series of UPS systems (a component of the company's InfraStruXure solution for on-demand datacentres) which both match the stated criteria for the holistic view which is the basis for achieving both optimum efficiency and low TCO.

Meeting Efficiency Goals
Particular to the choice of UPS using criteria of efficiency is evaluation at true operating conditions. UPS efficiency is invariably quoted by manufacturers at full load, but when operating with lighter loads, efficiency drops off substantially, for example where the load is shared between UPS devices in N+N (Tier 4 Datacentre) configuration or where single devices are operated well below maximum capacity efficiency will be reduced substantially. The chart shown on the right illustrates the performance of the range alongside that of a traditional or legacy UPS unit in various load conditions.

What is most noticeable is the UPS system maintains levels of efficiency below a 30% load and generally has a ‘flatter' efficiency curve than some products of this class. This is important since rarely do datacentres or other electrical installations operate at or close to their maximum capacity. In fact research has shown, for example, that many datacentres only ever achieve 30% of their designed operational capacity due mainly to availability/redundancy mandates and the M&E engineering habit of ‘over-sizing'.  Thus claims of efficiency based on maximum load provision are like the stated maximum speed of a car, rarely a reflection of how the vehicle will be used in the real world. When using efficiency as specifying criteria, it is imperative to look at how a UPS performs under various load levels in which it is likely to operate.

The Financial Perspective
It's one thing to say that higher efficiency infrastructure equates to lower total cost of ownership, but it's obviously another to see how the numbers actually stack up. Take the example below, which compares the costs of running a 400kW Galaxy 7000 to protect a full load at 95% efficiency with that of a legacy UPS at 90% efficiency. Over a 12 year period, assuming energy prices remain static, the user could save almost £200,000. Allow 5% for inflation and the cost savings rise to in excess of £260,000, in other words the annual costs of running the Galaxy 7000 is 50% lower than an equivalent legacy UPS at £30,000.
As discussed earlier, with many UPS designed to provide the highest levels of efficiency at the highest load, the savings become more pronounced as the size of the load is reduced and efficiency starts to tail off. Therefore at 50% load, energy savings by using Galaxy 7000 in place of a legacy system are £128,664 - again, the savings are calculated without the effects of inflation. The savings are substantial with such a wide efficiency gap, but it is also true to say that even a percentage point here or there in efficiency terms particularly where the UPS are used in multiple configurations, could add up to a great deal in energy savings and therefore consequential cost reductions due to lower cooling/ventilation requirements.

Other Efficiency Criteria
APC UPS systems have been designed and manufactured for harsh environments, offering high fault-clearing capabilities, a high load crest factor and excellent voltage stability even for 100% load step changes or unbalanced loads when compared with rotary-type UPSes..
With growing concerns about the shortage of personnel with suitable skills for sophisticated datacentre and electrical environments, there is a premium placed upon ease of installation, operation, monitoring and management. For local management, the Galaxy 7000 has been designed with an intuitive interface to provide clear and relevant operational information including 5000 time-stamped events, analysis and pictograms. The unit can also be managed remotely via a number of different operational protocols and is compatible with APC remote management tools and, in a situation of datacentre deployment, with APC InfraStruXure Central Capacity and Change Management software which enables datacentre operations to monitor and project the impact of changes to the physical layer of the datacentre. Galaxy 7000 is supported by Schneider Electric Critical Power and Cooling Services maintenance services and upgrade solutions.

From an environmental perspective, in addition to the ecological advantages that are realised through higher efficiency and therefore lower emissions, the Galaxy 7000 addresses environmental issues at each stage of the production process. This is done to meet and exceed standards required by international environmental regulation including those relating to the sites at which the technology is manufactured. The series is designed with fewer electronic control boards with 91% of parts suitable for recycling in compliance with the WEEE Directive and its weight is half that of the previous Galaxy generation. The efficiency in its design and its more powerful IGBT rectifier reduces  the size of the electrical distribution system. Higher efficiency can be acheived through use of its Eco mode operation which offers up to a 97% efficiency rating.

There is great financial gain to be had by optimising levels of efficiency from ‘conspicuous consumers' of electricity such as UPS systems. But in order to take advantage, those responsible must carefully consider the demands of the load which is being protected in terms of mission criticality and system design. Strategies such as rightsizing of infrastructure will avoid waste and modular systems can help answer that need. Use of UPS with published efficiency details and which have been designed to be highly efficient even at light loads can help to reduce the operational costs, energy waste and carbon emissions with added sustainability.

The electricity grids that serve European consumers today have evolved using similar technologies and infrastructure for more than a hundred years and though they have served well to date, it is clear more of the same will not be sufficient to meet current challenges and policy imperatives. New challenges arising from market liberalisation, increasing use of renewable energy sources and level of service requirement, calls for fresh thinking and in order to meet future needs, Europe's electricity networks must be flexible, accessible, reliable and economic

Enabling Europe's electricity grids to meet these challenges, take advantage of future market opportunities and fulfil society's expectations requires vigorous research efforts and a robust technical solution. The SmartGrids European Technology Platform has been introduced to enhance the level of coherence between the European, national and regional programmes and address the challenges of future networks. In this article, Masoud Bazargan, general manager of Areva T&D's technology centre explains why it is critical that the industry strives towards a shared vision and the benefits that SmartGrids technology platform will bring to the industry. He also highlights a number of pilot studies which are currently taking place as a result of the research and development.

The creation of SmartGrids
During the first International Conference on the Integration of Renewable Energy Sources and Distributed Energy Resources back in 2004, industry stakeholders including regulators, network operators, network designers, equipment manufacturers and technology providers as well as the research community, recognised that a technology platform for the electricity networks of the future had to be created. It became apparent through these discussion groups that there were doubts as to whether the existing electricity grid would be able to effectively integrate existing and future concepts such as renewable energy, micro generation and consumer integration within the grid.


As a result, the European Commission Directorate General for Research developed the initial concept and guiding principles of the technology platform with the support of existing research alongside IRED (Integration of Renewable Energies and Distributed Generation) which represents over 100 stakeholders in the electricity networks sector. Subsequently, the SmartGrids European technology platform for electricity networks of the future was formed and began its work in 2005 with an overarching aim to formulate and promote a shared vision for the development of European electricity networks looking towards 2020 and beyond. Areva T&D was one of the founding organisations within the technology platform and was invited by its members to chair its top level advisory council.


The scope of this particular platform aims to provide a joint vision towards efficient and reliable electricity supply. The market for sourcing energy has widened and as a result the network needs to be flexible in order to adapt to future developments and fulfil the needs of both the consumers and the network operators. Customers' habits and the manner in which they use their energy will also transform over time and the network needs to be able to cope with such changes.


The network of the future is also required to be accessible in that it needs to grant connection access to all network users, particularly for renewable power sources and high efficiency local generation with zero or low carbon emissions. Traditionally, through transmission and distribution systems, power stations dispatch power and there is little or no consumer participation and no end to end communications. Individuals, small businesses and communities who utilise micro generation technologies such as small scale wind turbines, hydroelectric plants, ground source heat pumps and PV (Photovoltaic) solar systems, should be equipped with the ability to send electricity back to the grid so that it becomes a bi-directional flow of power. This of course would provide real benefits for both the operator and the consumer who should then be incentivised.


Assuring and improving the security and quality of the electricity supply, consistent with the demands of the digital age with resilience to hazards and uncertainties is also a key requirement to meet the needs of Europe's future and one which the technology platform will strive to ensure is implemented. Today's society depends on a secure supply of energy. There are countries without adequate reserves of fossil fuels that are facing increasing concerns as to primary energy availability. Furthermore, the ageing infrastructure of Europe's electricity transmission and distribution networks is threatening the security, reliability and quality of supply. We need to be looking at ways of re-designing grids which address these challenges.

The technology platform will also seek to form a network that is sustainable by providing best value through efficient energy management, deregulation and application of innovative technologies. Although SmartGrids seeks to address the challenges and opportunities for the electricity grids of 2020 and beyond, it needs to be an evolutionary process due to the cost and long life of the majority of existing network components. Short term issues require resolution immediately whilst defining and researching the long term challenges. The strategy needs to fulfil the expectations of society, protect the environment as well as minimise risk and allow for timely business decisions and actions to be taken.
It is important to note that SmartGrids is not just about the needs and opportunities of Europe. The majority of its features are appropriate and beneficial for networks around the world. However, it is triggers such as the liberalisation of the European energy market, the need for a secure cross-continent electricity network as well as Europe's recognition of identifying and implementing effective solutions that address global warming, which position Europe at the forefront of the SmartGrids revolution.

Challenges
Although the advantages to having a technology platform in place are evident, there are tough challenges ahead. The technology certainly exists, however more effort needs to be carried out in order to prove the effectiveness of the technology on existing, live networks.
Areva T&D is at the forefront of the SmartGrids revolution and is helping to design and build Europe's electricity grids of the future. It is partnering with network operators to understand their needs and concerns, explain how they can benefit from emerging technologies and deploy pilots and proof of concepts.

Pilot studies taking place
Areva T&D's technology centre in Stafford is playing an integral role in performing short and long term research activities. Short term SmartGrids research which we are now starting to see being implemented is in the area of technology-based information and communications, whereby network owners are reaping the benefits, one of which is that they can still retain the same electricity network infrastructure without having to make significant changes. Thermal measurement equipment and thermal estimator algorithms are allowing the creation of products that allow network owners to manage the dispatch of power in their grid, which in turn, avoids overheating of components and associated network losses. Populating the future grid with nano-scale sensors may in the future allow us to optimise the performance of the grid in that it will permit real-time condition monitoring of all the components. However, in the short term, Areva T&D is creating network operation and management benefits through the incorporation of a more finite number of sensors in key equipment.
Another project aligned with the SmartGrids vision and one which Areva T&D is a leading player, is Fenix, whereby it is creating the network management software which allows owners of small-scale generators to aggregate and create a virtual power plant. In doing so, owners can trade on to the network and sell their power generation capacity for maximum value and benefit to the overall network.

Distribution network operators are also now providing Smart meters to domestic consumers. These devices allow remote reading of meters which enables automated billing. Areva T&D is creating the technology to enable these meters to act as a platform for real-time pricing of electricity to the consumer and to settle all transactions between consumer and the operator. Such a change could happen very soon and would lead to a demand-side revolution that will enable customers to participate directly in the electricity market as consumers and producers. In these customer-centric networks, consumers will decide whether to use energy intensive appliances at peak times, or instead delay their use until demand and the energy price is lower, thus smoothing and removing the peaks of demands that the industry experiences now. This could in turn lead to reduction of spinning reserve needed for system stability and security of supply and/or costly reinforcement of the network thus reducing the environmental impact.

Shaping the future
The importance of the SmartGrids technology platform cannot be underestimated. Throughout the development of the new grids, communication at every level is vital. Effective dialogue between industry stakeholders will ensure that relevant information influences the system design of the future. Many factors will shape future electricity networks and the actions and decisions taken today will influence longer term outcomes. In order to be sure our network will sufficiently meet future needs, the SmartGrids vision must be embraced. By doing so, industry stakeholders, consumers and the environment can reap the benefits such a vision seeks to provide.

Over the last few decades, control panels have changed beyond all recognition and this process of evolution shows no sign of stopping, or even of slowing down. Steve Rickard of Moeller Electric looks at the developments that can be expected in the not-too-distant future

Strange though it may seem to today's engineers, it's only a few decades ago that most control panels had no electronic devices in them at all. In those days, even the most complex of control schemes was implemented using electromechanical relays - sometimes hundreds of them in a single panel - pneumatic timers and other arcane electromechanical devices like stepping switches and uniselectors.


These panels actually worked, but they were huge, expensive, unreliable and almost impossible to modify or upgrade. Small wonder then that when the first programmable controllers appeared on the scene in the early 1970s, they were received with enthusiasm. At a stroke, they dramatically reduced size and physical complexity of control panels and, best of all, they made modifications easy.


Those early PLCs were still expensive and not particularly easy to program. For these reasons, their use was initially confined to larger projects. PLCs soon, however, became available in smaller, less expensive versions that were simple to program, making them an economical choice in smaller applications. Nevertheless, until quite recently the very smallest applications - typically those that might be implemented with less than a dozen conventional relays - remained uneconomic for programmable control.


The introduction of intelligent relays such as Moeller's easy Relay, has addressed this issue. These tiny programmable relays have most of the facilities of a low-end PLC, but are very small, very inexpensive and very easy to program.


In addition to their relay-replacement functions, they usually offer a range of extra facilities, such as real time clocks, retentive memory to preserve system status information even when the power is off and, in the more advanced versions, communications facilities. These intelligent devices have effectively taken over the last stronghold of control systems based on conventional relays and, as a result, these systems have all but disappeared in new applications.


The adoption of programmable devices vastly decreased the amount of control wiring needed in panels, but it did nothing to simplify the power sections of the panels and, in particular, the motor starters that are such a central feature of most control panels remained just as complex as ever to implement.


The first step to improving this situation was a move away from the conventional - even old-fashioned - UK starter design that is based on three fuses, a contactor and an overload. By replacing the fuses and the overload with a motor protection circuit breaker, the number of components in a DOL starter is reduced from five to two, which instantly cuts the mounting and wiring time for the starter components.


And that's not all. Because the connections between the contactor and the motor protection circuit breaker are standardised, it is possible to arrange for these components either to connect directly to one another, or to be linked by a simple tool-less plug-in connector. Both methods simplify the mounting of the starters, and both eliminate most of the wiring that would have been needed with a conventional starter.


The tool-less connector has the additional benefit that removal of the connector provides secure and positive isolation for the starter, which is a very useful aid during fault finding and commissioning. The best of the connector-based systems, such as those in the Moeller xStart range, also go beyond simple DOL starters, and make it equally easy and convenient to fabricate reversing and star-delta starters.


Another area of recent progress in relation to motor starters is the growing availability of electronically controlled coil systems. These provide much better control over the closing stroke of the contactor, thereby increasing its life because of reduced mechanical stresses. From the panel building point of view, however, they have another advantage.
 Since they reduce the coil current needed to close the contactor, they make it possible to switch even quite large contactors directly from low-power PLC outputs. This means that inexpensive high-density output modules can be used in the PLC, and also that the need for interposing relays, which always add complexity and cost to a control panel, is eliminated.
Of course, despite all of these improvements to the motor starters themselves, it is still necessary to provide power to those starters. The standardised size of starters based on motor protection circuit breakers has, however, made it possible to design convenient prefabricated busbar systems on which the starters can be directly mounted. Such an arrangement eliminates most of the power wiring, and makes modifications to the panel much easier.


Having considered motor starters in some depth, let's return to the control circuitry associated with panels. Here, the biggest development to date has, in fact, been outside the panel, where conventional field wiring has, in all but the smallest systems, been replaced by fieldbus connections.


Besides reducing the amount of costly field wiring needed by a very large factor, this change also provides the field installation with flexibility to match that of the PLC-based control system. No longer is it necessary, if changes are needed, to resort to expensive and inconvenient re-wiring for field devices. Instead, all that's usually needed is to connect any new field devices to the fieldbus and adjust the PLC program to accommodate them.
The widespread use of fieldbus systems has also brought about significant changes within the control panel. Gone are the banks and banks of screw terminals that used to be needed for the connection of conventional field wiring, and instead there are just a few fieldbus connectors. In addition, the PLCs no longer have racks and racks of I/O cards, just one or two fieldbus masters. The result is panels that are smaller, less expensive, easier to wire, easier to install and easier to maintain.


As we've seen, most areas of control panel design have undergone huge changes in recent times but, until now at least, one area has remained almost untouched. This is the control wiring within the panel, for example, between the motor starters and the programmable controller or intelligent relay.


This last bastion of conventional wiring is, however, about to fall, with the introduction of Moeller's SmartWire, the first in a new generation of smart panel wiring systems. The objective of smart panel wiring is to provide all of the benefits of a fieldbus system within the panel itself. Indeed, one way of looking at it is to consider it as a fieldbus system that is optimised for panel use.


With smart wiring, the ordinary control wiring between the motor starters and the PLC is replaced by daisy-chain style connections that use simple pre-fabricated cables with plug-in connectors. Not only does this reduce the amount of wiring and eliminate most of the I/O modules needed on the PLC, it also dramatically cuts the wiring time, and makes it virtually impossible to make wiring mistakes.


Further, smart wiring brings a high degree of flexibility. If it's necessary to add another starter, for example, all that's needed is to mount it and plug it in to the smart wiring system - usually the work of a few minutes.


Other important benefits of smart wiring, at least in the Moeller Electric implementation, are that it is completely self-addressing, so setting it up is a trivial task, and that it works with ordinary motor starters. To use the system, it's simply necessary to add a SmartWire interface to the starter in the same way that an ordinary auxiliary contact block would be added.


With the introduction of smart wiring, virtually every aspect of control panel design and construction has been given an overhaul, resulting in panels that are smaller, more cost effective, faster to produce and much more versatile. But what of the future?
One fairly obvious speculation is that smart panel wiring systems will expand in scope. At present, they are mostly limited to motor starter connections, but there's no real doubt that their scope will soon be extended to cover other devices such as pushbuttons and indicator lamps.


Also, given the close affinity between smart panel wiring and fieldbus systems, it's perfectly probable that a single system will evolve that efficiently and cost-effectively embraces the applications areas of both.


Power switching devices such as contactors are unlikely to see major changes unless dramatic developments are made in the materials from which they are fabricated. This is because they have already reached the limits of size and performance that can be achieved with present-day materials.


One possible development, however, is growth in the use of vacuum contactors for low voltage switching, especially in high power applications. Already widely used in MV applications, vacuum contactors are more compact than their air-break counterparts and deliver much better service in arduous applications. Their relatively high cost limits their adoption at present, but this may well change in the not too distant future as manufacturing volumes increase.

To those of us who have worked in the control gear industry for a long period, the changes in control panel design seem to have happened quite slowly. And so they have, but the cumulative effect is little short of amazing. Just about the only resemblance between a modern control panel and one built in, for example, the 1960s, is the enclosure!

The changes to date have been truly beneficial, delivering reduced cost, better performance, vastly enhanced reliability and much greater flexibility. One thing is for sure - the developments won't stop here. I've given some hints for the future but to stay up to date and get the maximum benefit from new developments, the best advice is to stay in close touch with your favourite controlgear suppliers and, in particular, watch out for their news announcements!