Features

In a competitive market, mistakes can be costly. Pressure from time and resource constraints has never been greater, especially in the field of fire performance cables where increasing legislation can be confusing. Here, Graham Turner of AEI Cables examines the issues and focuses on the decision making process

The pace of legislative change and confusion over Building Regulations means the fire performance market is searching for clarity as a blizzard of new products are introduced to meet rapidly changing demands.


Landmark legislation such as the Regulatory Reform (Fire Safety) Order, coupled with increasing pressure to make sure modern electrical systems are integrated into the wider building infrastructure, means there has never been more need to get it right first time.
Meanwhile, the new 17th Edition of the wiring regulations also makes additional requirements for safety services, such as emergency escape lighting and fire protection applications.


The Fire Safety Reform Order has shifted the emphasis of responsibility onto a more risk-based approach, whereby the responsible person - that is to say, the owner, manager or other persons - is responsible for the maintenance of a building or premises.
As such, the responsibility for agreeing to the specification of fire prevention systems and products, including cabling into a building, lies with that person.


If a subcontractor changes the product for whatever reason and something goes wrong - for example, a fire occurs or a fault is found with the cabling - then the responsibility for the outcome rests with the named person.


Other important issues here are ensuring business continuity and protecting property as well as life. The responsible person should check with the contractor that the products installed comply fully with the specification.


There could not be a better illustration of weighing the risk than with those projects associated with The Olympics.


Here, modern electrical systems need to provide intelligence so that in the event of a fire the control panels can continue to work and help emergency services instruct a safe evacuation.
Critical control systems require secure power supplies, perhaps for the duration of a major fire. These systems will be used for safety and security, and stadium monitoring, providing intelligence on a range of subjects, with phased evacuation where relevant. Not only are specific deadlines set on many of these projects, but delays can be very costly to all concerned.


A fire alarm system, for example, should be inspected and tested by those parties concerned together. On major projects, having to strip out cabling because the system is not working correctly, or because the wrong cable has been installed, would mean extra time - and thus cost - to a contractor or specifier, and should be avoided in the first place.
With the correct specification and information, contractors and wholesalers can then spend time more efficiently and cost-effectively delivering and installing the systems that are so critical in major building projects.


The only way to assess the most appropriate products and systems for each project is to consider the specific requirements of each on a case-by-case basis.
To be in a position to make informed decisions, however, we should be aware of all the options available and what is most appropriate.


Major government organisations agree that the most effective way to deal with safety in this sector is to take the wider, integrated approach.


The Health & Safety Executive (HSE) points out that the primary cause of control system failure in a major study was specification (44.1%), with 20.6% linked to changes in systems after commissioning, 14.7% to design and implementation, 14.7% to operation and maintenance and 5.9% on installation and commissioning.


The conclusion here is that all products should be considered to ensure they are suitable for the system, and that all lifecycle phases should be addressed for functional safety to be covered.


Functional safety relies on the overall safety that in turn depends on a system or equipment operating correctly in response to installation.


The HSE believes a risk-based approach offers significant potential safety benefits as long as an active risk management system is in place, and that functional safety should be adopted if the safety benefits from new technologies are to be realised.


Furthermore, under the Corporate Manslaughter and Corporate Homicide Act 2007 which came into force in April this year, companies face unlimited fines and other penalties if found guilty of corporate manslaughter. It is currently possible to prosecute companies for the existing offence of manslaughter, but it will be far easier to convict under the Act.
For a successful manslaughter conviction under the current law, the prosecution must prove that a director or senior manager - a ‘controlling mind' - is guilty of manslaughter.
In practice, particularly in prosecutions of large companies, it can be very difficult to prove a tangible link between a death and the ‘controlling mind' to secure a conviction. One of the most notorious prosecutions to fail in this respect was that of P&O European Ferries following the sinking of the Herald of Free Enterprise.


The new offence means organisations will be guilty of corporate manslaughter if there are gross failures in the management of health and safety resulting in death. A substantial part of this failure must be at senior level. Senior level is defined as the people who make significant decisions about the organisation, or at least substantial parts of it. This includes centralised headquarters functionaries as well as those in operational management roles.
The offence applies to all companies, corporate bodies, partnerships (if employers), government departments and police forces. Courts will look at management systems and practices across the organisation, and if these structures cause a death which is shown to have resulted from ‘a gross breach of duty of care' to the deceased, then the organisation will be considered guilty.


The organisation's conduct will have to have fallen far below what could be reasonably expected; juries will have to take into account any health and safety breaches, and how serious and dangerous they were.


While individuals can't be prosecuted for the new offence, they can still be prosecuted for the existing offence of gross negligence manslaughter/culpable homicide for health and safety offences.


Meanwhile, the revised BS 5839-1 (02) for fire detection and alarm equipment includes the requirement that cables for addressable alarms must be - and remain - data compatible but it does not include a specific test to demonstrate it.


Mineral Insulated Cabling (MIC) is the unrivalled fire performance cable for those applications where safety is paramount and the risk too great not to use the best.


It is recognised as the cable of choice for fire alarms, detection equipment and emergency lighting and the risk of anything going wrong is greatly reduced because of its key features:
- its ability to withstand temperatures over 1,000 degrees centigrade
- data transmission continuity during a real fire
- reduced need for maintenance
Add to this its ease of installation and it is easy to see why MIC is a cost effective solution where guaranteed safety is key.
Where risk assessments have been completed and all involved parties agree that an enhanced cable with a lower survival capability than a mineral insulated product can be installed in that particular specific application.


These products are designed for fire performance qualities which are flame retardant, robust and meeting the higher end requirements in BS 5839-1 (02). Where the project can be served with softskin cables which meet the desired criteria of for standard applications, and a risk assessment has been completed involving all parties, then standard cabling is the ideal choice, providing unequalled fire performance to this criteria.


There are many products now available in the fire performance sector and the sheer number and choice can make the selection process difficult, especially with so much legislative change to consider. Ultimately, it is down to each organisation and each person in the supply chain to meet their relative responsibilities and know they are not compromising the safety of others. With expert help and guidance, they can make considered judgements during the selection process, knowing they have made the correct choice without compromising the relevant standards and regulations.

The selection of static UPS systems has tended to focus on system reliability represented by availability and mean time between failure (MTBF). However, as energy costs have skyrocketed, two issues are conspiring to make efficiency central to UPS evaluation; a focus on total cost of ownership (TCO), and green or environmental considerations says Shri Karve, business development director, APC by Schneider Electric

UPS efficiency is invariably quoted at near full load, but when operating with a light load efficiency can drop substantially.  Losses fall under three categories: no-load loss, proportional loss, and square-law loss.


No-load losses can be considered as an overhead loss as they are independent of load and result from the need to power components like transformers, capacitors, and communication cards.  Since they represent more than 40% of all losses they are the largest opportunity for improving UPS efficiency.  Proportional losses increase as load increases and a larger amount of power must be "processed" by components in the power path.  As the load increases on the UPS, the electrical current running through its components increases causing losses with the square of the current sometimes called square-law losses.

System Design and Efficiency
When designing systems, it is important to balance levels of availability (i.e., how mission critical is the protected load), with overall capital costs, installation and engineering costs and operational expenses (TCO). However, system design has an impact on overall efficiency e.g., in a resilient, 2N system both sides of the "N" must be capable supporting the full load in the event of a failure. Even with one of the UPS operating at full capacity, the maximum efficiency of the system would be <50%. In reality it is highly unlikely that the UPS would be operating at full capacity and therefore inefficiency levels would be raised. And, of-course, there would be the cost impact of servicing and maintaining two units.


For more details about system design, White Paper #75 "Comparing UPS System Design Configurations" available from www.apc.com/gb provides a useful guide.

Improving UPS Efficiency
To meet today's efficiency demands, UPS manufacturers can utilise three factors to reduce UPS losses; technology, topology, and modularity.

Technology
IGBTs enable the power conversion process to be operated in a "high frequency pulse-width-modulation (PWM)" mode which reduces the size of filter components leading to further efficiency improvements. Replacing analog controls with more advanced DSP controls can improve efficiency through intelligent adaptive switching, especially at lighter loads. In addition, DSP controls are lower power and allow a substantial reduction in no-load losses.

Topology
Two principal topologies used in large UPS systems are double conversion on-line and delta conversion on-line. In delta conversion UPS, efficiency is improved mainly by reducing no-load losses and by a reduction in square-law losses. By using the input transformer in a series arrangement, the UPS input current and output voltage can be fully regulated without having to convert all incoming power to DC and back to AC again.

Modularity
The closer a UPS operates to capacity, the more efficient it will be. Modularity allows users to size the UPS system closely to the load and to scale up as the power requirement grows.
Modularity enables improved serviceability and reduced maintenance requirements through self-diagnostics and user replaceable modules. 

Conclusion
As total cost of ownership has become a key decision factor when specifying large UPS systems, the differentiating value is efficiency. With the exception of Rotary solutions, UPS technologies continue to evolve toward greater electrical efficiency. In order to maximise energy use and reduce wastage through losses, it is both financially and environmentally expedient to specify the most efficient UPS and to design and operate systems as close to the protection needs of the load as possible while not ignoring future requirements.  UPS products and solutions from APC by Schneider Electric, with published efficiency numbers provide greater evidence for decision making.


For more details, please see White Paper #108, Making Large Static UPS More Efficient, available from www.apc.com/gb

 

By Rob Morris, UK country manager, POWERVAR

There are two important reasons for computers users to install UPS (uninterruptible power supply) technology. The first, ensuring continuity of AC power when the mains supply goes down, is widely understood. The second, protecting sensitive electronic equipment, especially computers, extending their working life and guarding against the corrosive causes of sudden component failures is less widely appreciated.


Fortunately, power cuts are relatively rare occurrences but organisations need to give more thought to the vital benefits of a supply of clean, quality power uncontaminated by line noise, impulses, common mode disturbances and other problems inherent in the mains supply. In theory, a UPS system will give users the best of both worlds. But in reality, many UPS designs are just not up to scratch as acceptable power quality tools. A closer look at the issues involved can help preventing costly and usually, sudden, system failures. After all, what is the point of a piece of equipment that provides a reasonable degree of backup but is not delivering the day-to-day protection against damaging ‘gremlins' in the power supply - spikes, surges and other disruptions, things that are not only be invisible but tend to occur more often than power failures.

An important choice
Choosing between on-line UPS or standby UPS is key. This choice should not be influenced by how much protection is offered by a particular inverter design, but rather what type of technology the UPS system is protecting. Many industrial plants use a combination of both linear and switch mode power supplies.


On the one hand linear supplies contribute less noise to the electrical environment, yet switch mode supplies are popular because of their lower cost, higher efficiency, smaller size and low heat contribution.


Most linear power supplies lack the internal storage necessary for them function during the 4-6 msec needed for a UPS to switch from AC line to battery-powered inverter. What is more, linear supplies are sensitive to voltage, which means  it is vital that they are well regulated.
By contrast , switch mode supplies are relatively immune even to large swings in line voltage and will perform satisfactorily as part of standby UPS systems. These criteria are crucial consideration in the initial choice of the most appropriate and effective UPS design namely, standby UPS for switch mode power supplies and on-line UPS for linear power supplies.
It is a myth that on-line UPS products deliver a higher level of power quality simply by virtue of their double conversion (AC-DC-AC) design. In fact, a well-designed standby UPS product (single conversion) can provide much better protection than more expensive poorly designed on-line systems.

Single or multiple units?
Another contentious point is whether it is best to install one large UPS or to use a number of smaller UPS products distributed throughout a facility.


Using a single large UPS offers the economies of scale. However, a number of small individual UPS systems offer more flexibility. A 15kVA system is, for example, likely to be less expensive than say, 30 individual 500VA units. And the ability to deliver more usable single-phase power from a centrally installed three-phase UPS than from several individual single-phase units can also be beneficial.


However, small individual UPS systems provide greater flexibility, require less distribution wiring, are easier to maintain and give the extra security of knowing that a UPS failure in one area will not affect the others. Ultimately, the user needs to make a decision that is consistent with their overall approach to maintenance and installation.

Clean Power
Power quality issues should be carefully considered when selecting a UPS. A system that is expected to protect against power outages should not be allowed to fail for other reasons either. The careful selection of a UPS system can deliver protection from a complete range of power problems, added to the fact that many UPS systems can be combined with other devices to further improve power quality.


Power quality involves more than having a clean, noise-free electrical supply. Ultimately it depends on the requirements of the equipment it is protecting. For industrial electronic systems some of the quality issues are:

- Impulses - They may be of short duration but these fast rise time, high energy events can pack significant destructive potential and can result in the catastrophic failure of semiconductor devices. Even when not immediately or apparently destructive, these impulses contain sufficient energy to erode or weaken semi-conductor junctions which can result in their eventual failure. The effect of these impulses can be mitigated by a surge diverter.

= Common mode voltage - This is any voltage measured with reference to safety earth. Since most modern computer systems use safety earth as their logic and communications reference, clean and quiet safety earths are essential. The kinds of problems that common mode voltage can cause computers include: processor lockup, lost or fragmented data, communication errors, or unexplainable ‘no trouble found' failures. Common mode voltage may occur in systems with daisy-chained or undersized neutrals, or when branch circuits become lengthy. Using an isolation transformer to create a separately derived power source eliminates common mode voltage.

- Noise - This is a result of the distribution and use of electrical power. RFI and EMI are generated by every device that uses electricity. Perversely, many of the disturbances that produce computer malfunctions are induced by the computer's own electrical system. Noise filters built from capacitive and inductive elements will divert disturbances to electrical system earth.

- Voltage regulation - This is more critical issue for linear power supplies than for systems powered by switch mode supplies. There are a number of methods of providing well-regulated voltage, including; tap-switching or ferro-resonant voltage regulators and buck/boost autoformers. An on-line UPS provides natural voltage regulation because of its built-in double conversion process.

- Outages. - These can only be mitigated with a UPS device that supplies reserve power from its batteries. These UPS systems can be an effective bridge until either the utility is restored or another source is brought on line.

- Frequency changes - These are caused by variations in the fundamental operating frequency of the electrical system. Unlike single conversion designs, double-conversion UPS systems can act as frequency regulators and high-quality on-line UPSs can regulate the output frequency tightly across a very wide range of input frequencies.

Clean, continuous power
While single-conversion UPS systems may not deal with all of the six elements described above, double-conversion systems will typically provide superior protection against normal mode noise and impulses.


Surge diverters, tap-switching voltage regulators and battery-powered inverters are found in single conversion designs but most do not include either a powerline noise filter or an isolation transformer.


Double-conversion UPSs offer better protection from normal mode noise and impulses and also produce an output free from voltage and frequency regulation problems. However, many do not include an output isolation transformer, which leaves the load vulnerable to disruptive common mode disturbances.


To ensure clean, continuous power for computing applications one should begin by examining the application itself and the technology to be protected. If linear power supplies are part of the application, the on-line UPS is a natural choice. If the application involves switch mode power supplies (as an increasing number do), either on-line or standby UPSs will provide backup power.


Other factors, such as personal preference, budget or other issues, can also come into play. If harmonics and power factor are factors there are on-line designs available with unity power factor input and low front-end harmonic contribution. These may be compelling reasons for preferring one technology over another.


Regardless of the design, it is important to ensure that a UPS delivers a high level of protection from noise, impulses and common mode disturbances. For this reason, noise filters, surge diverters and isolation transformers can be regarded as essential features of the UPS design.


Installation options
It should always be remembered that powerline noise and common mode disturbances are partly a function of branch circuit length. This means that while these disturbances may not exist in the output of an isolated UPS, they will gradually reappear as the output circuit length increases.


This is one disadvantage of a centralised UPS system. Even the best designed centralised UPS may prove incapable of providing clean power for a load located some distance from the UPS. So while the UPS portion of the overall power solution may be located where it can provide convenience and availability, the elements that ensure clean power (isolation transformers, filters, surge diverters etc) must be installed as close as possible to the load they are protecting.


As a result, industrial users are now specifying a less expensive central UPS and installing separate discrete power conditioners by each computer, control rack or cabinet.
Systems that must not fail when there is a power outage should also be protected from failures caused other power anomalies. But the fact is that not all UPS systems provide clean power. It is possible to select a UPS that does give complete protection. It is also feasible to combine a UPS with other devices to achieve clean, continuous power for industrial computing installations. The correct starting point is a close examination of the application and the technology that needs to be protected.

Peter Bentley, sales director at Uninterruptible Power Supplies, explains how ensuring UPS systems are lean and fit for purpose helps to keep data centres running

The health of a data centre is highly reliant on the health of its uninterruptible power supply. A regular assessment of the ‘FAT' factors - flexibility, availability and total cost of ownership - helps optimise UPS systems to increase efficiency, save running costs and reduce CO2 emissions.  Rising energy costs and pressure to shrink carbon footprints make these achievements all the more desirable.


Flexibility
There are two distinct aspects of flexibility of UPS systems: The first relates to an individual UPS system's flexibility to efficiently protect its critical load in the data centre, even when the load changes over time, as it inevitably does. There is huge potential to reduce the electricity consumption of data centres, and to alleviate the burden on their stretched cooling systems, by continually matching the capacity of UPS systems to their respective critical loads. State-of-the-art modular 'transformerless' UPS systems are much more flexible than their traditional counterparts at matching load requirements and delivering optimum efficiency.
The second and equally important aspect of flexibility relates to a UPS system's ability to increase the level of protection it provides to its critical load. The level of protection is a matter of strategic choice by the data centre manager and is a trade-off between availability (not only of the UPS system but also the critical load) and initial capital costs to achieve that level of availability. However, capital expenditure should not be considered on its own; installation, operation and upgrade costs are important factors in how investments in power protection will be paid back (see total cost of ownership').


Figure 1 illustrates how the ability to ‘right-size' modular UPS systems promotes efficiency. The limited flexibility of a free-standing UPS would require the initial installed power to exceed the data centre's anticipated capacity requirements, resulting in a wasteful gap due to oversizing. However, the flexibility and scalability of modular UPS enables power to be added as the data centre requirements grow (without increasing footprint).
Inserting and removing ‘hot-swappable' UPS modules facilitates right-sizing a UPS system to its anticipated critical load. The trend for the size of critical loads, especially those within data centres, is to increase. However, right-sizing for decreasing loads is equally easy.

Availability
Since power problems are the largest single cause of computer downtime, increasing power availability is the most effective way for IT managers to increase their overall systems availability. The single most important issue in increasing power availability is to decrease the mean time to repair (MTTR) of the power protection system.


Referring to Figure 2, the availability of a traditional UPS system and an advanced modular UPS system are compared. The UPS system on the left comprises two 120kVA free-standing UPSs in 1+1 parallel-redundant configuration, and the one on the right comprises four 40kVA ‘hot-swappable' UPS modules in 3+1 parallel-redundant configuration.


Their MTBFs are 600,000 and 400,000 hours, and their MTTRs are 6 hours and 0.5 hours respectively. However, the availability of the free standing solution is 0.99999 (five nines) while the modular solution provides an availability of 0.999999 (six nines). This higher availability increases overall system availability by a factor of 10 compared to free-standing (non-modular) UPS systems that are not hot swappable.


Figure 3 categorises power protection systems in quadrants according to how well they meet the requirements of high power availability, redundancy and hot-swappability. As more components in a system become hot-swappable, the system moves from the bottom to the top of the graph; and as more components become redundant, it moves from left to right. The modern, modular UPS provides the highest power availability and the highest level of protection for IT managers' critical loads.


Parallel UPS systems comprise either centralised parallel architecture (CPA) or de-centralised parallel architecture (DPA). While CPA systems offer a cost benefit by sharing common components, the drawback is that this centralised configuration introduces a number of ‘single points of failure' into the system, which adversely affect its availability. DPA systems, with effectively no single-point-of-failure, offer very high availability. The additional capital expenditure on a DPA system will therefore be recouped by providing enhanced protection against revenue losses caused by system failures.

Total Cost of Ownership (TCO)
The lower purchase price of traditional UPS technology must also be offset against significantly higher operating costs in comparison with a modular system. In fact, reductions in energy loss costs mean that the potential higher outlay for a modular system can be recovered within the first year of operation. There are also a number of longer term benefits that contribute to significant cost savings with modular technology - more than £25,000 over five years.


TCO should also take account of the weight, volume and footprint of UPS systems, since these factors can increase transport and installation costs by 50% or more and impinge on valuable square footage. Compared with an advanced modular UPS, the traditional UPS system, based on two units, needs two to three times the amount of floor space and, since many utilize transformer based technology, weigh up to two or three times more.
Further significant reductions of TCO can accrue from rationalising installation, training and maintenance services, and by re-cycling reusable UPS modules. The scalability of modular systems also contributes major savings. Upgrading a traditional UPS requires extra space, costly cabling and taking the UPS off line. With a modular UPS, the upgrade is performed by simply inserting the additional power modules into the rack, provided the system's distribution and frame have been specified for the maximum foreseeable requirement. Such upgrades can be safely performed without any interruption to the load, without increasing the footprint, and with no additional work on site. This flexibility makes upgrading a system very easy, and with very little additional cost.


Modern hot-swap-modular, double-conversion, true on-line UPS systems optimise all the elements of FAT. However, many older UPSs employ out-of-date technology and are often sized incorrectly for today's needs. Such inefficiencies mean that companies could be burning excess electricity and creating needless heat emissions, compromising efforts to reduce their carbon footprint. In all, thousands of pounds can be saved on uninterruptible power supply expenditure, simply by giving systems a FAT health check.

Speak of deploying widespread AC inverter technology, or calculating cube law considerations for a plant's fans and pumps and the average finance director would keel over. However, as GAMBICA's variable speed drives group argues, until such topics are understood at the top table, industry will fail to maximise potential energy efficiencies

In most developed countries, industry accounts for about half the electricity consumed. Of this industrial consumption, two thirds is typically used in powering electric motors. For this reason, the control of motors must be placed high on any energy efficiency agenda. Yet, because motor control involves highly technical issues, the overwhelming majority of boards of directors and senior business managers continue to focus energy efficiency attention on readily understood areas such as insulating building fabric and reducing lighting consumption.

For many, energy measures revolve around the consideration of thermal issues in the building fabric with remedies such as insulation, glazing, and heat loss countermeasures. These are really only passive countermeasures that compensate for energy loss rather than the active control of the energy deployed.

Under the Kyoto Protocol industrialised countries have agreed to reduce their collective emissions of greenhouse gases by 5.2% by 2008-2012 compared to the year 1990 (however, compared to the emissions levels expected by 2012 prior to the Protocol, this limitation represents a 29% cut). The target in Europe is an 8% reduction overall with a target for CO2 emissions to fall by 20% by 2020.

The cost of an electric motor can be very deceptive; in particular, the annual energy cost to run the motor can be up to ten times its purchase price. Indeed, the running costs of a fully loaded motor operating at 50Hz can range from over £1,000 a year for a 2.2 kW motor to over £18,000 a year for a 37 kW one. Consider that, for example, a typical 11kW AC induction motor, that can be purchased these days for as little as £300, could cost as much as £30,000 in electricity consumed over a 10 year lifetime.

Fit a variable speed drive and simply by slowing the motor by 20% the energy bill is halved. About 105TW of electricity is consumed by British industry each year. It is estimated that two thirds of that is consumed powering electric motors; and of those motors about three quarters of them power fans, pumps or compressors in continuous duty variable torque applications. It is these variable torque applications where the greatest savings can be made from VSDs.

In other words, if every fan, pump and compressor motor was equipped with a VSD and had a 20% reduction in speed, the total consumption would fall by about 26TW per annum. Put another way, the savings would enable the closure of the UK's largest coal fired power station, saving 20 million tonnes of CO2 per annum. Even more dramatic to consider is that this figure effectively means that the CO2 emission attributable to  3.1 million homes would be negated. In other words, the whole of Greater Manchester and Birmingham would be rendered carbon neutral!

If the targets of those nations compliant with the Kyoto Protocol are to be met, greater attention must be placed on broader energy efficiency regimes. These have to include motor speed control.

Most of the bodies charged by government with communicating and effecting change in the approach to energy consumption are naturally focussed on conservation in the broadest public arena. For this reason, the public relations and other promotion has been almost exclusively targeted at the general public and on measures such as insulation, heating and lighting reduction. This is true even of the respected Carbon Trust and Energy Saving Trust in the UK. However, with ambitious national carbon reduction targets and current consumption trends failing to meet the rate of decrease needed indicates that the UK will fall drastically short within the 2020 deadline. Bodies such as Gambica, which represents most of the significant motor speed control manufacturers, know that more must be done.

That government may impose further levies, legislation or penalties relating to energy use is speculation, but as the 2020 deadline looms, it remains a possibility. Against this backdrop, is the almost exponential rise in energy prices that are directly impacting on industry, commerce and consumers by its significant and proportionate affect on costs.
In the simplest terms there are a number of things business can do: ignore energy issues completely and either pass on costs as increased prices or accept continuously reducing margins (rather than invest in energy efficiencies); take passive measures such as installing energy saving luminaires, improving insulation; take active energy initiatives and address all aspects of consumption.

Hence, we return to the topic of motor control. This for industry, commerce and large commercial buildings represents low hanging fruit in terms of making substantial energy savings. In many respects fitting motor speed controls is like changing to energy saving light bulbs in the home - but with on-going automatic savings.

First, a quick physics lesson
Consider that billions of electric motors are in daily (often continuous use) every day. In most countries, fewer than 10% of the motors have any form of control. In continuous duty applications such as powering fans, pumps and compressors, it is possible to effect incredible savings by reducing the motor speed by a very small amount. This is because in such applications, the fundamental physical laws governing centrifugal fans and pumps also preside over the potential savings that can be achieved. In laws of physics, power is consumed as a cube of output. Indeed, affinity laws dictate that while motor torque varies with the speed squared, power varies with the speed cubed. Hence, the cube law impacts greatly the energy efficiency in such equipment.

On loads of this type any speed reduction will save large amounts of energy (that is, a 20% speed reduction will result in a 50% power saving). Remember, torque varies with the speed squared, power with the speed cubed. This means that variable torque loads, such as fans and pumps offer the greatest potential for energy saving.
 
Culture gaps inhibit industrial energy conservation
Why there has not yet been a huge uptake of motor speed controls lies largely with ignorance of the technology and ambiguity within industry over who owns the task of implementing energy efficiency. To explain this statement more clearly, in a manufacturing plant for example, the plant engineers are often acutely aware of the energy efficiency benefits of installing variable speed drives (VSDs) to AC motors. In the boardroom, managers may be alert to the need to economise on energy for any number of reasons: escalating fuel bills; corporate social conscience; or even just because it's good marketing sense to be seen to be green. The problem is plant engineers are never measured on their ability to save energy; while directors and managers are unaware their plant engineers could do so. It is a simplistic view, but one borne out by evidence throughout manufacturing industries.
Energy intensive industries such as metals manufacturing, glass and plastics processing and food and beverage production understand the need for energy management because their processes involve great amounts of heat. These businesses have traditionally sought ways to maximise their return on investment from the energy used in their primary processes. However, even these energy aware businesses often fail to realise how much more can be saved through building controls and a company wide energy policy.

Of far greater significance overall is the use of variable speed drives in a broad range of processes.

While in many countries industrial energy use has now been slightly outweighed by that consumed by commercial and residential buildings, it is a fact that industry consumes huge amounts of electrical power. About two thirds of that is typically consumed powering electric motors. Of these, an overwhelming majority can be made significantly more energy efficient by controlling their switching on and off or by controlling their speed.

This is a relatively simple task of equipment retrofitting, yet it is clear that most manufacturing and process plants fail to take the step. The reason is often because those that control the costs of an industrial operation are not communicating with those charged with the management of the production processes.

For example, if a painting plant uses hundreds of AC motors on fans, pumps and compressors (continuous duty applications) it could readily benefit from the use of variable speed drives. However, while the plant manager, as an engineer, understands this, he or she is invariable responsible only for improving productivity or output and not for the overhead costs. Higher management is concerned with paying the overheads but remains unaware that such a saving could be made because it is never on the agenda in engineering meetings.

In industry, senior management and plant engineers must learn to talk if an holistic and comprehensive energy efficiency policy is to be achieved. In no other sector is the communication gap wider, than between those charged with making energy decisions and engineers in industry who know how energy can be saved.

Now cost of ownership has become a significant specification criteria for lighting design, it is important to keep up to speed with the latest light source options, says Pat Godden of Megaman

A combination of soaring energy costs, greater environmental awareness and increasingly stricter energy efficiency legislation means end clients are now taking a more holistic view of their lighting and other services. In the case of lighting, of course, they expect it to provide a high quality lit environment as well as reducing carbon emissions and cost of ownership.
The underlying detail of ‘cost of ownership' is also now better understood by end clients so they are look beyond the high profile energy efficiency element. They also want an installation that will reduce maintenance and lamp disposal costs - and minimise any disruption and paperwork associated with working at height.

In parallel with these developments, lamp manufacturers have been busy designing new, improved light sources - improving energy performance and life, and making some sources available for a wider range of applications. This means there is now much more choice so, in theory, it's easier to meet these demands. However, it also means that it's important to keep up with the latest developments so they can be implemented where most appropriate.
Such developments have been very swift in recent years, with advances in existing technologies as well as the development of new sources such as LEDs. While the latter have great potential for the future, their relatively low light output currently places significant limitations on their use.

As far as established technologies are concerned, fluorescent lighting has probably moved forward faster than most. But many of these developments have gone unnoticed at the specification end of the market. While T5 linear fluorescent lamps have been widely accepted as an alternative to T8s, there have been similar, or perhaps even greater, advances in compact fluorescent lamps (CFLs) that have not received the same level of recognition.
To some extent this is due to their familiarity and the perceptions that were formed when CFLs were first introduced. Early models with BC and ES lamp bases were largely seen as replacement for GLS lamps but they were bulky and heavy and very expensive. Their use was also limited by their high surface luminance, which could cause problems with glare if the lamp was unshielded.

More recently we have seen the emergence of a new generation of CFLs, with a much wider range of applications than their predecessors. Offering high luminous efficacies, shorter pre-heat times and longer life (15,000 hours), they are also more compact thanks to major developments in glass bending and can now be used as replacements for many sources, including halogen spotlights and even high bay lighting. In addition, thanks to the advances in phosphor formulations, CFLs are now available in a wide range of colour temperatures and with much improved colour rendering, extending the scope of the projects they can be specified for.

A case in point is the introduction of a range of CFLs with GU10 lamp bases, which can be directly retrofitted to luminaires that were designed originally for GU10 halogen spotlights. For example, a 9W CFL GU10 provides an alternative for a 40W halogen lamp, while a 7W version will match the light output of a 30W halogen lamp. These lamps also feature a glass diffuser to provide a smooth and even distribution of light. In addition, a 15,000 hour life means the lamp will last up to 15 times as long as the halogen spotlight it replaced.

This longer life is particularly important in applications where the lighting is essential, such as display lighting in a retail environment. Here, the shop can't afford to have even one lamp out of use for more than a few hours and replacing them is disruptive to customers and expensive in terms of labour costs. Consequently, specifying CFL alternatives can help with compliance with CDM regulations.

Another consideration is the lower heat output of CFLs compared to incandescent sources. Again using retail as an example, vast arrays of display lighting can contribute significantly to air conditioning usage so CFLs will help to reduce this as well.

For other applications, the miniaturisation of CFLs has enabled the tubes to be enclosed inside a glass diffuser to eliminate glare, while keeping the overall size very similar to the GLS lamps they are designed to replace. These ‘GLS replacement' lamps are now available in a wide range of formats, from a classic ‘bulb' style to smooth and twisted candle lights, globes and softlight styles.

One relatively recent innovation is the introduction of a silicone sleeve on candle and ‘golf ball' lamps, so if the lamp breaks the sleeve acts as a safety shield against flying glass. A further benefit is that the sleeve replaces traditional non-environmentally friendly etching techniques to create a frosty appearance.

Another limitation of early CFLs was the fact they could not be dimmed without the use of special control gear. The latest generation of dimmable CFL lamps is compatible with most triac dimmers, so they can be retrofitted to existing luminaires switched via a standard dimmer and dimmed steplessly from 100% to 10% Thanks to a built-in cooling tube, the light output remains consistent and stable at any dimming position.

As well as increasing in their range of applications, CFLs are now able to provide much higher light outputs, making them suitable for replacing high intensity discharge (HID) lamps in some applications. For example, high output CFLs, containing a cluster of 4 x 18W lamps, can provide a direct replacement for a 200W mercury lamp in a low bay or high bay application. This provides a saving of 128W for each lamp with no compromise on performance, while a much longer life delivers big savings on maintenance.
Such high output CFLs can also be incorporated into floodlights that would usually use incandescent or high intensity discharge lamps. These provide a much more efficient solution for applications such as security lighting, lighting of construction sites, car parking areas and many other outdoor applications.

Just as importantly, in the aftermath of warnings about mercury in CFLs by the Environment Agency (and the subsequent media exaggeration), newer CFL designs use a mercury amalgam rather than liquid mercury.

Fluorescent lamps, and other gas discharge lamps, have always needed mercury to function and traditionally the mercury was inserted as a liquid. During the life of the lamp some of the mercury is absorbed into the glass, phosphors and electrodes.

A far more acceptable alternative is to use mercury amalgam rather than liquid mercury. Mercury amalgam is a 50% mercury alloy, used in lower doses than with liquid mercury, and has been used in dentistry, chemistry and mining for many years. When the lamp is activated, the amalgam pellet vaporises to contribute to the process described above. When the power supply is switched off it returns to its safe solid form again

In describing the recent changes in CFL technology here, my hope is specifiers will be prompted to take a fresh look at what is available and recognise the advantages modern CFLs can offer the end user.

Over recent years there has been a continuous increase in installed wind power generation capacity throughout Europe. This has caused the transmission system operators (TSOs) to review their grid connection rules - otherwise known as grid codes - to limit the impact of wind farms on network power quality and stability. Peter Jones of ABB UK investigates

New rules demand power plants of any kind should support the electricity grid, not just in normal operation but also in case of voltage dips. Some of the key considerations are steady state and dynamic reactive power capability, continuously acting voltage control and fault ride-through behaviour.

The result of these new considerations is that some commonly used turbine designs may have limitations in meeting the grid code requirements of some countries, especially for steady state and dynamic reactive power. For wind farms where these types of turbine are installed the solution is to install appropriate "add-on" reactive power equipment to achieve the necessary grid code compliance for operation and power production.

Reactive power compensation
Reactive power control provided by generators or capacitor banks alone may be too slow for the sudden load changes found in wind farms. ABB offers two appropriate reactive power compensation solutions, the SVC (Static Var Compensator) and the Statcom (STATic COMpensator).

The first approach, the SVC, is based on conventional capacitor banks, together with parallel thyristor controlled inductive branches, which consume the excess of reactive power generated by the capacitor bank. This type of equipment can be directly connected to the intermediate voltage bus, which interconnects the wind farms (up to 69 kV). When needed, it is also possible to connect the SVC to the high-voltage network via a dedicated transformer.
The second, more advanced, approach to compensation for reactive power is the use of a Voltage Source Converter (VSC) incorporated as a variable source of reactive power. Compared to other solutions a voltage source converter is able to provide continuous control, very dynamic behavior due to fast response times and with single phase control also compensation of unbalanced loads. The ultimate aim is to stabilise the grid voltage and minimize any transient disturbances.

ABB's Statcom converters are based on power converter System (PCS) platforms providing the following control features:
- Power factor correction (cos phi control)
- Voltage control
- Active harmonics cancellation
- Flicker mitigation
- Unsymmetrical load balancing
The Statcom features the same state-of-the-art power electronic voltage source converter (VSC) technology used in ABB's PCS 6000 range of products, such as the ACS 6000 range of medium voltage drives. It is a purely static device, with no switched passive elements, that provides outstanding performance for both steady state and dynamic operation, with the added advantage of a small installation footprint.

ACS and PCS 6000 converter units are based on three-level IGCT (integrated gate commutated thyristor) phase modules. The IGCT is the state-of-the-art semiconductor element for this power range. Large numbers of these converter units have been sold worldwide and they have a proven track record of performance and reliability.
A particular advantage of the ABB Statcom in wind farm applications is its fast dynamic voltage control and its behaviour during both balanced and unbalanced grid faults (fault ride-through), which enable it to help meet stringent grid code requirements.

Reactive power requirements
An analysis of the requirements of the UK's grid code suggests the required reactive power is approximately one third of a wind farm's nominal active power. Typical wind farm nominal power ranges from 30 MW up to 100 MW for on-shore installations. Therefore, the required reactive power compensation is in the region of 10 MVar to 35 MVar. For large wind farms, typically several hundred MW, ABB recommends the more traditional SVC. While, as a rule of thumb, the Statcom is appropriate for small to medium sized wind farms.

Typically, the very compact Statcom power electronic modules are placed inside a cabinet. This also houses other equipment such as the DC link, cooling system and controls. Only a few additional external components are needed, such as the Statcom transformer, grid filter and heat exchanger.

STATCOM functionality
The STATCOM is equipped with a set of functions in order to help wind farms to fulfill the grid code requirements. These include:
- Steady state reactive power supply or absorption. This function can be fulfilled by following a reactive power set-point, a set-point for a power factor at the connection point of the wind farm or by operating according to a linear reactive power versus voltage characteristic (Q/U characteristic).
- The implementation of the latter case also fulfills the voltage control requirement generally called for in the grid codes. The grid companies often require a certain flexibility to change the basic behaviour of the voltage control scheme. A reduced set of changeable parameters has to be available, especially the target voltage and the slope of the linear characteristic. 
- Smoothly follow a set-point ramp. This is stepless, in contrast to solutions based on switched passive component
- Meeting the dynamic requirements of the grid codes, e.g. a step in the set-point is followed within less than 1 second without notable overshoots or oscillations.
- During voltage dips (balanced or unbalanced), the Statcom injects reactive current in the order of value of the nominal Statcom current and therefore helps to support the grid voltage.

Typical application
A typical application of a Statcom is a wind farm in Scotland that has used it to overcome its initial difficulties in complying fully with the grid code requirements in terms of: steady state reactive power supply; voltage control and dynamic reactive power supply. In addition, it also has helped to meet harmonic requirements. Since the wind farm is connected via two 33kV cable connections to the nearest 132kV/33kV substation, it is split into two parts that can also be connected via a coupling switch. However, both wind farm strings are required to run autonomously. Therefore, two 12.5 Mvar units were required.

Both converter units were placed inside the wind farm substation building,  this allowed a cost efficient installation in a well protected environment. Both transformers were located outdoors next to the converter units. Although the output voltage waveform of the Statcom is close to sinusoidal, a small harmonic filter was still needed to maintain harmonic distortion within acceptable limits. The filter is located on a steel structure close to the transformer. The heat exchangers for the converter closed loop water cooling system are also located outdoors.

Tests carried out with the units in continuous operation at nominal power have shown that they now enable the wind farm to comply with all the grid code requirements for steady and dynamic reactive power capability and voltage control. The behaviour of the wind farm during grid faults has also been modelled, and the results show that the units can be expected to support the wind farm during balanced faults - they inject reactive current in such a way that they help to maintain the voltage. And even during heavy unbalanced faults the Statcoms support the voltage.

ABB's latest development to help UK wind farm operators achieve grid code compliance is a containerized Statcom that provides a mobile, easily transportable, source of reactive power. It is designed primarily to act as a temporary solution while the need for a long term, permanent reactive power installation is assessed. The mobile unit is housed in a standard shipping container that incorporates the VSC, multi-voltage step-up transformer (to provide flexibility of use between the UK and Ireland) and associated control equipment. All the equipment is factory built and commissioned to provide the fastest possible deployment when it is delivered to site, and only basic foundation work with a small plinth is required.

A single modular unit can provide up to 10 MVar of reactive power, making it ideal for use with wind farms up to around 30 MW. However, the modular approach enables a number of units to be piggy-backed together to create larger solutions.

Cracking the grid code requirements present a definite challenge for wind farm developers in certain countries. Mainly because the steady state and dynamic reactive power injection/absorption requirements are difficult to fulfill with some wind farm designs. Therefore "add-on" equipment is often needed to comply with the grid codes. Statcoms present a cost-effective and efficient method of providing reactive power compensation for small to medium sized wind farms.

The food and drinks industry finds essential support in automation systems, in order to flexibly diversify production and improve the management of processes. This is to the full benefit of competitiveness and safety of operators, equipment and products says Carlo Marchisio, of Rockwell Automation, Italy

The role of automation in driving the worldwide growth of the food and drinks industry has been recognised by a number of major studies. According to Rexam Consumer Packaging Research (2005) more than 70% of the market for automated packaging systems is down to the food and beverage sector making the production processes of the companies operating in this sector more efficient. This is achieved through integrated systems such as Manufacturing Execution Systems (MES), ERP and IT integrations combined with innovative equipment and machinery equipped with devices such as PLC, drives and Scada.

Production flexibility
But what are the most important dynamics which affect the food and beverage business? Essentially there are four important points to be examined closely:
s Customer demand and satisfaction
s Competition in the international market
s Supply chain integration
s The safety of operators, equipment and products

Customer demand and satisfaction
In order to meet new customer requirements and obtain full satisfaction, production flexibility and agility are essential. Automation and information systems facilitate the production of new products and reduce time-to-market through integrated architecture, connectivity and scalability. Furthermore, these systems develop ongoing processes, facilitate the management of raw materials, and allow visibility of operations, thereby allowing a higher quality standard to be achieved and reducing rejects and waste materials.

Increasing competitiveness
The implementation of MES automation systems provide significant support for the supervision and analysis of production processes in order to identify the activities necessary to reduce production costs. This involves data collection of process parameters, monitoring of the efficiency of machines (OEE calculation), traceability of materials for the reduction of waste and the analysis of energy parameters to control consumption. As a result, this helps decrease machine downtime, extending the knowledge of the equipment for maintenance personnel - thanks to specific training on applied automation systems; improving the performance of the users and reducing spare parts as well as the MRO cost.

A well integrated supply chain
Integrated information-based automation systems, currently adopted on a vast scale, allow the monitoring of production orders, the management of the flow of raw materials and the connection of the plant to ERP systems. Thanks to these tools, it is possible to visualise in real time the status of production orders and schedule production based on the availability of material resources and equipment. The entire production system - machines, equipment and warehouse - is directly linked on an operational level to business systems, and therefore the plant manager can examine the status of the production process and help improve or modify the flow in accordance with product requirements.

Safety and functionality
The increasingly complex regulatory framework which imposes essential international safety requirements for the factory environment underlines the importance of sophisticated automation systems which provide the safety of operators and the prevention accidents. Some software functions safeguard applications and connection networks from possible failures, damage and intrusions which could halt production. The food and drinks industry must conform to food safety and regulatory compliance and thanks to the implementation of software systems and procedures that track operations and collect data, it is possible to fulfil the requirements of regulatory agencies and respect HACCP system regulations, in particular those concerning traceability against bioterrorism activities and EU 1:8/2002.

Summing up...
Companies operating in the food and beverage sector must be capable of rapidly adapting their processes in order to produce whatever is necessary to respond to consumer demands and introduce new products onto the market. In this regard automation systems can be programmed to react immediately to production variables providing reactivity and flexibility, while at the same time providing an increase in sales and market share. The capacity to reduce the variability of processes, and guarantee the uniform quality, reduces production costs - with favourable effects on profits. The speed with which automation companies respond to user demands makes them the ideal and established providers for food and drinks manufacturers, since they have, and are constantly increasing, the know-how necessary to fully understand the sectors problems and implement truly effective solutions.

Carlo Marchisio is industry sales manager, Consumer Goods, Rockwell Automation, Italy

The risk of exposure to electric arc is a hot topic when working with electricity. No matter how many steps are taken to minimise the potential for an accident, it is crucial to be prepared for the worst, as Paul Reader, Empower's electrical training specialist reiterates week after week at Empower's purpose-built, £2 million training centre, housed beneath the cooling towers of Ratcliffe Power Station in Nottinghamshire

Empower, a leading provider of training services to a host of major UK utility and manufacturing companies, is the UK's only Centre of Vocational Excellence (CoVE) for Electrical Power. The company specialises in training technical staff and engineers in everything from safety management to cable jointing. Paul Reader explained, "There is a common misconception amongst people who are highly experienced in electrical work that an electric arc "won't happen to them" or if it does, it won't be powerful enough for them to come to serious harm. On the contrary, however low the risk, when working with low or high voltage systems, equipment failure and/or human error have the potential to cause an electric arc generating up to 30,000°C in the core plasma of the arc - in a split second. When an electric arc occurs, there is no warning, and in worst-case scenarios, if inadequately protected, people can suffer fatalities or burn injuries that can affect them and their families for years.

"Wearing personal protective equipment (PPE) as a last resort is as important as carrying out risk assessments and applying mechanical control measures to reduce the risk of accidents. It is vital for people at risk of exposure to electric arc or flash fire to put a final protective barrier in place by wearing the appropriate flame resistant clothing. As a CoVE, we strive for excellence in everything we do and that includes providing our delegates with the very best advice on the very best PPE."

The purpose of protective clothing is to address the thermal effects - i.e. burn injury hazard - of exposure to flash fire and/or electric arc. Layered garments, made of materials like Nomex from DuPont, can stand the arc blast, absorb the bulk of the radiant heat energy caused by electric arc or flash fire, and help minimise the burn injury level through its inherent flame resistant properties. Designed with a high level of safety and comfort in mind, garment systems are evaluated according to the International Electrotechnical Commission (IEC) in the Standard IEC 61482-1. In addition to meeting the performance requirements for CE-certification, fabrics and garments made of Nomex must be submitted to DuPont's testing facility in Geneva, in order to qualify for partnership in the Nomex Quality Programme (NQP) - which entitles manufacturers to attach a Nomex label to a garment. Here in Geneva, they undergo a series of special tests and evaluations for heat and flame protection, heat stress management, wear-life, comfort, aesthetics and design.

Arc-Man Testing
The DuPont Arc-Man, a set-up consisting of a mannequin or panels with built in temperature sensors on their surfaces (‘skin'), is used to test garments that are designed to protect against the thermal effects of electric arc. The mannequin, wearing the garment system in question, or panels covered with fabrics, is exposed to an electric arc in a controlled environment to test whether the systems or single fabric layers can prevent second-degree burns. The Arc-Man testing facility, uses a circuit generator that can produce 500 MVA, 60 MJ. Arc currents up to 15kA are possible with a duration in the range between 100ms and 2 second.

Under these circumstances, there are two typical test set-ups and procedures:
The international standard IEC 61482-1 (‘open arc test'), which is currently under revision (future IEC 61482-1-1) specifies two test methods to measure the arc thermal performance value (ATPV) of materials or garments.
The Method A is used to measure the fabric's response to arc exposure when tested in a flat configuration.
Method B is used to measure the clothing response to an arc exposure and shows the effects on the garment, sewing thread, fastenings, fabrics and other accessories when tested on a mannequin torso.
  

Testing is typically done with an open arc at 8 kA and of varying arc duration in order to achieve the desired incident energy onto the test specimen. The ATPV is the value of the incident energy (usually given in cal/cm2 or kJ/m2) on a fabric or material that results in sufficient heat transfer through the fabric or material to cause the onset of a second-degree burn injury based on the Stoll-Chianta curve model.  On a basic level, when selecting a clothing system, the higher the ATPV, the better the protection.

The second test set-up and procedure is covered in the new IEC 61482-1-2:2007 (‘box test' or ‘arc in box test'), which supersedes ENV 50354:2001 and CLC/TS 50354:2003 (The two superseded standards did not require heat flux measurements, but based the performance rating only on visual evaluation of test results). The test set-up consists of a bipolar arrangement of electrodes which is surrounded by a box, which is open on one side only. The effects of the electric arc are thus constrained and directed towards the one panel or mannequin positioned at the open side in 30 cm distance from the centreline of the box. The test has been designed to be carried out in two fixed test classes (Class 1 or 2), selected by the amount of prospective short circuit current (4kA or 7kA). The test voltage 400V and the duration of the electric arc 500 ms are the same for both test classes. Materials and clothing will be tested with two methods:
  

The Material box test method is used to measure the material response to the exposure of an arc constrained by the specific box of this test method, when the material is in a flat configuration on top of a panel. A quantitative measurement of the arc thermal performance is made by means of the energy transmitted through the material. The Garment box test method is used to test the function of the protective clothing after an arc exposure including all the garment findings, sewing tread, fastenings and other accessories, no heat flux will be measured.

Designed to define
The essential difference between the test methods of IEC 61482-1 (or the future IEC 61482-1-1) (‘open arc test') and of IEC 61482-1-2 (‘box test') is that the ‘open arc test' has been designed to define and evaluate a protection parameter such as is the ATPV, which can be attributed to a material or garment as a product specific protection property, whereas the ‘box test' allows only a classification of materials and garments into two arc protection classes in case of exposure in front of a very specific box: Class 1 (4 kA), Class 2 (7 kA). In practice there can be higher risks than the Box-test Class 2, different arc enclosing boxes, etc. The most common classification of risks and protective clothing performance according to ATPV values is given by the NFPA 70E standard. It defines 4 risk categories and corresponding arc ratings for protective clothing: Category 1: ATPV > 4cal/cm2, Category 2: ATPV > 8 cal/cm2, Category 3: ATPV > 25 cal/cm2, Category 4: ATPV > 40 cal/cm2.
In any case, a risk analysis shall clarify the actual risk of exposure to an electric arc. And the testing according to both above mentioned IEC standards refers only to the thermal effects of an electric arc; it does not apply to other effects like noise, light emissions, pressure rise, hot oil, electric shock, the consequences of physical and mental shock, toxic or other influences caused by the decomposition of enclosures, etc.

But already the part of assessing the risk of thermal exposure in terms of incident energy is not an easy task. Elaina Harvey from DuPont Personal Protection, explained, "When talking about the incident energy relevant for the evaluation of the performance and the selection of arc-protective clothing, one is actually talking about values of incident energy per surface area, for example in units of cal/cm2. The calculated incident energy, against which protection is needed, comes from the end user's risk assessment. The incident energy will depend on:
- arc current i.e. fault value (kA)
- arc voltage (V)
- arc duration (milliseconds)
- distance from worker to arc (cm)
- electrode spacing (cm) and kind of electrode material (copper, aluminium, iron...) 
- whether single or triple phase electrical circuit
- whether in an open or a box environment, and on the dimensions and materials of the box."

How to obtain the incident energy value
There are various ways end users can carry out a risk assessment to obtain this calculated incident energy value from simplistic free of charge computer calculators to in-depth statistical studies. Meanwhile several companies offer their help to carry out an arc flash survey.

One of them is EmPower Training which can provide advice in carrying out a risk assessment and training courses.

EA Technology  is an organisation that can carry out an arc flash assessment to determine specific incident energy levels and this is tailored to the end user's network and operation. Therefore, PPE is one element of their arc flash study, other factors being assessed includes the reduction in electrical protection settings and network fault levels along with the operational practices.

TAS Engineering Consultants  has been carrying out electrical arc flash hazard studies since 1995 and has extensive experience in this field; the work is tailored to suit the individual site and circumstances.  A typical approach is to survey the site electrical distribution system, develop a single-line diagram, carry out a protection setting study, then calculate the electrical fault levels at each point in the system.  With this in place, TAS then analyse the potential arc energy levels to IEEE 1584 parameters at each point in the distribution system and advise on the appropriate FR PPE to be used to safely operate the electrical equipment at each point in the system.  Guidance is then given on rationalising all the information into one or two levels of FR PPE for use site-wide to cater for all circumstances.

As an example, if the end user risk assessment requires clothing to protect from 22 cal/cm2 then DuPont with the garment and fabric manufacturer, can recommend layered systems to achieve the protection required.  If underwear is taken in to account when recommending the system, steps must be taken to ensure that employees are supplied with and wear the undergarments.  If not, it is important to advise that, worn in high risk environments, undergarments made from fabrics like polyester and nylon (e.g. football shirts) can stick and melt onto the skin and cause further burn injury in the event of a flash fire or electric arc."
TAS uses two products that assist in the analysis, and detection, of arcing faults. These are the Arc Flash PTW software module, and the Falcon Arc Detection System, both supplied by CEE Relays, part of a protection relay manufacturing group.

CEE Relays has been supplying the Power Tools for Windows (PTW) power system analysis software for the last 20 years. The software consists of several modules, including the arc flash module, allowing users to quickly, and easily, calculate the incident energy caused by an arcing fault, investigate ways of reducing this energy, and identify suitable grades of protective clothing. Using the full suite of PTW software, CEE Relays also carries out all types of power system analysis, including arc flash analysis, and can also train engineers in the use of the software.  As well as a wide range of protection relays, CEE Relays also supplies the Falcon Arc Detection System. The arc detectors, which can be retrofitted into existing switchgear, detect the light created by an arc, and issue trip signals within 1ms. This fast response time significantly reduces the damage caused by an arcing fault.

Thermo-Man Testing
It is also important to protect from flash fire, which could occur after the arc incident, for example - if there are ignitable contaminates on the garments or around the working environment. DuPont Nomex systems can be assessed on Thermo-Man, a life-size mannequin equipped with 122 heat sensors and exposed to a flash fire with temperatures rising to 1000°C.  Data collected from the heat sensors, both during and after exposure to flames, predict the amount and location of second and third-degree burns.  The chance of survival rates can also be predicted across certain age groups, which is important information that can be used in helping companies if they have an ageing workforce.
Harvey continued. "PPE worn for protection against the thermal effects of electric arc should provide permanent flame resistance, not melt or ignite, resist break-open during exposure and insulate the wearer from heat so as to minimize burn injury. The principle of selection of PPE is that the arc rating of PPE exceeds the calculated incident energy of the arc for each specific working environment identified during the risk assessment. Garments made of Nomex are designed to offer excellent protection and comfort. The meta-aramid fibres do not drip or melt at high temperatures. The Limiting Oxygen Index is approximately 28. Thus, when exposed to flame at room temperature in a normal environment, Nomex will not continue to burn and will self extinguish, when the flame is removed. At temperatures above approximately 427°C Nomex carbonises and forms a tough char. Garments have a high resistance to ignition and break open and because they are inherently flame resistant (as opposed to having only a flame retardant coating), this protection is permanent and cannot be washed out or worn away."

Reader from Empower said, "As electrical training specialists, we are keen to develop technical partnerships with solutions providers and manufacturers of safety clothing and equipment intended for use in the utility and manufacturing industries. That way we can understand how and why products are developed, learn about the science behind the products and gain first hand experience of how they react in various environments, applications and situations. This information can then cascade through us to end users to improve their level of understanding of the risks and their effects.

"We were delighted to be invited to DuPont's European Technical Centre in Geneva to learn more about the technology behind Nomex and watch garments made being put through rigorous electric arc and flash fire tests. In comparative tests, flame resistant, protective utility garments made of Nomex scored very highly on the safety scale in relation to some garments made of conventional fabrics, and often exceeded the relevant European and International Standards. Through working with their customers to develop new solutions for the safety and protection of people at work, companies like DuPont are instrumental in improving the safety culture in today's working environments. Large power and manufacturing companies are driving the trend for better employee safety and thanks to this, many more companies are starting to recognize the importance of supplying protective workwear garments that offer high performance characteristics."

The popularity of withdrawable switchgear declined considerably in the UK during the last ten years, but has recently been making a comeback. However, its rise in popularity has raised concerns about compliance with new IEC regulations. Steve Goldspink, Siemens Transmission and Distribution, outlines the new regulations and tells the untold story of the return of withdrawable switchgear to the UK market

For the last decade, the UK switchgear industry has focused on fixed pattern switchgear. This being despite the fact its alternative - withdrawable switchgear - has a reputation for being, where required, much easier and safer to repair and maintain; particularly in process orientated environments where power outages can be extremely costly. In recent times however, withdrawable switchgear has made a comeback as the industry has begun to rediscover, understand and appreciate its benefits.

This new switchgear, now available, is not vastly different technology but changes in technical requirements of users based on operational safety, service continuity and maintenance needs have driven subtle change.
In order to keep abreast with these changes, the International Electrotechnical Commission (IEC), a leading global organisation that prepares and publishes international standards for all electrical and electronic related technologies, has developed a new standard for medium voltage switchgear - IEC 62271-200.
IEC 62271-200 is a standard for AC metal-enclosed switchgear and control gear for rated voltages above 1 kV and up to and including 52kV. There are a number of differences between the previous and new standard. Contrary to its predecessor, IEC62271-200 no longer classifies switchgear according to design features but on the basis of functional characteristics. It demands a detailed description of the characteristics concerning the aspects of service continuity, maintainability and safety classifications, which are all of prime importance to the user.
Introduced in 2003, it is a legal requirement for all switchgear built after 1 February 2007 to satisfy this standard. IEC 62271-200 supersedes the previous standard for medium voltage switchgear - IEC 60298 and aims to remove some of the ambiguities in this standard by means of classifying switchgear.
An increasing concern of mine, however, is a number of medium voltage switchgear manufacturers in the power transmission and distribution industry may be deterred from putting their equipment through the appropriate testing procedures to ensure it meets this standard, due to the significant investment required in doing so. Whilst accurate statistics are almost impossible to source, it is almost certainly the case that some switchgear being sold new into the UK market has not been tested to the new standards, and is therefore unlikely to be fully compliant with the new standard. In short, the ultimate benefit of the new IEC 62271-200 standard is to provide improved classifications regarding the levels of operator safety, service continuity and maintainability - features that should not be overlooked.

The new switchgear utilises well established, high availability maintenance-free vacuum circuit breaker technology, with operating cycles far exceeding the normal number, meaning frequent access to the circuit-breaker is no longer an ongoing concern for the switchgear operators. Additionally, the vacuum arc-quenching principle in modern switchgear is technologically superior to other arc-quenching principles currently employed within the industry.

Furthermore, in line with the latest requirements of the new standard, to ensure maximum operational and functional safety, the circuit breaker and earth switches are fully type tested inside the appropriate switchgear panel and not as a standalone device to ensure all functional influences are taken into account.

One particular area where safety is of critical importance is internal arc tested equipment, an issue which is gaining widespread awareness across the world due to operator safety concerns. An internal arc is a high resistance arc fault within the switchgear enclosure due to disruptive discharges between phases or phase to earth. Internal arcs can be created by a variety of causes including insulation failures, functional faults of devices and even negligence during routine operation and maintenance. The result however can be catastrophic, in that the arc reacts explosively with the surrounding atmosphere, causing a rapid increase in temperature and pressure which, if uncontrolled, can be extremely hazardous to people in the immediate area.

With the old IEC standard, much room was left for different ways of carrying out the test and interpreting the results. Although still an optional test in IEC 62271-200, the new standard gives clear guidance on how to perform the internal arcing test and defines the acceptance criteria. More specifically, test conditions are defined and are no longer subject to agreement between the equipment manufacturer and the test laboratory. Ultimately, internal arc classification is only granted if all criteria are met.

In addition, when an internal arc classification is selected, all five internal arc criteria must be fulfilled without exception. Firstly, covers and doors on the switchgear must remain closed, with limited deformations accepted. Secondly, no fragmentation of enclosure must occur, with zero projection of small parts above 60g in weight. There must also be no holes in the accessible sides of the switchgear up to a height of two metres and the horizontal and vertical indicators used in testing must not ignite due to the effect of hot gases. Finally, the enclosure must remain connected to its earthing connections at all times.

The key now must be for manufacturers of switchgear equipment to take their responsibilities seriously and ensure all new switchgear being produced goes through the appropriate testing where required, and is re-classified in line with the new IEC standard.
This is even more important given there is a general skills shortage facing the industry. We are now in a situation where more and more purchasers of switchgear equipment are either outsourcing their operations because of a lack of skilled engineers, or being forced to employ a smaller team of engineers to carry out the work. Both of these factors make health and safety even more important in order to protect those engineers operating and maintaining switchgear equipment.

My advice to end-users is to demand the switchgear they are purchasing meets the latest testing criteria and all switchgear used has been classified in accordance with IEC 62271-200. This is the only way that users of switchgear in industrial applications can have the peace of mind of being able to select products which utilise the latest developments in technology, safety, service continuity and reliability.

Withdrawable switchgear is making a welcome return to the UK market with process industries benefiting from easier maintenance and repair, which in turn can result in much reduced downtime. However, any move to withdrawable switchgear should only be contemplated when maximum operator safety can be guaranteed. In effect this means selecting equipment type-tested according to IEC 62271-200.

Jim Wallace of Seaward highlights the main changes to the new IEE Code of Practice for portable appliance testing

What is the IEE Code of Practice for PAT testing?

The IEE Code of Practice for In-Service Inspection and Testing of Electrical Equipment provides a guide to those with a responsibility for maintaining the safety of portable electrical appliances under the Electricity At Work Regulations 1989, Health and Safety at Work Act, Management of Health and Safety at Work Regulations and Provision and Use of Work Equipment Regulations.

By providing comprehensive guidance on periodic inspection and testing it ensures that organisations, administrators and those carrying out the testing fully understand the requirements of the EAWR 1989 and can demonstrate compliance with it.

So why the changes?

Recently the IEE has reviewed the Code of Practice. The new 3rd edition takes into account technology advances and the implications of other market changes in relation to in-service electrical safety testing. By expanding the Code of Practice by over 50 pages, the revised publication provides much clearer guidance on all aspects of portable appliance testing with the addition of a number of useful illustrations.  As an example, whilst the previous document provided detailed advice on checking mains plugs and cables, the revised version is supplemented by the inclusion of multiple illustrations showing typical faults that might be encountered. Similar clarification and added details are provided for all aspects of the inspection and test process.

Has the new Code changed the scope of equipment to be tested?

No - but it has clarified some earlier points. For example, in the past certain types of electrical equipment, hand dryers for example, may have been regarded as a appliance by anyone testing the electrical installation, or as a fixed installation by anyone carrying out in-service testing. As a result these items of electrical equipment may have remained untested. To overcome such confusion the new IEE Code makes it clear that appliances which are connected to the electrical supply by a flex should be tested, even if they are permanently installed.

What are the new recommendations for RCD testing?

One of the main changes in the updated IEE Code concern new requirements in relation to testing RCDs. In particular the revised version stipulates that when an extension lead or multiway adaptor is fitted with an RCD, the operation of the RCD should be checked using an RCD test instrument to determine that the trip time is within specified limits. For those responsible for carrying out portable appliance testing this may require some changes to be made to the type of test instruments used. However, Seaward has anticipated these changes and many of the company's testers are now equipped with an RCD trip time test.

How has guidance on insulation testing changed?

Testing insulation resistance at 500V d.c. can be problematic when the equipment under test is fitted with transient suppressors or mains filtering and until now the only alternative was to perform a protective conductor/touch current measurement. The revised Code of Practice introduces two new test methods which can be used as an alternative to the 500V insulation test. The first method is to reduce the insulation test voltage to 250V dc and the second is to perform an alternative/substitute leakage measurement.

Alternative or substitute leakage is measured using a technique similar to that used when measuring insulation resistance. A test voltage is applied between both live conductors (phase and neutral) and the protective conductor (earth) during a Class I test or a test probe connected to the equipment enclosure during a Class II test. The resultant current is measured and then scaled to indicate the current that would flow at the nominal supply voltage.

The test voltage is 50Hz AC and normally in the range of 40V to 250V. The test voltage is current limited and so there is no hazard to the test operative. As the test voltage has the same nominal frequency as the mains supply the leakage paths are similar to those found when the equipment is in operation. Similarly, because the test voltage is not greater than the nominal supply voltage of the equipment under test, measurements are not affected by transient suppressors, MOVs or other voltage limiting devices.

Who should carry out the testing?

The EAWR already require that testing should be carried by a competent person and the new IEE Code provides further clarification on the competency required. Specifically, the IEE Code advises that a competent person should possess sufficient technical knowledge or experience to be capable of ensuring that injury is prevented. The new Code continues with further explanation on what that technical knowledge or experience may comprise, including such factors as an adequate knowledge of electricity, an adequate understanding and practical experience of the system to be worked on and an understanding of the hazards that may arise and the precautions which need to be taken.

What other changes should be highlighted?

On a general note, it has always been recognised the PAT equipment used for testing should be calibrated annually or in accordance with manufacturers' instructions. A calibration certificate is issued which states that the test instrument is within specification at the time the calibration is performed.  However, the certificate does not guarantee the performance of the test equipment at any time after that and the revised IEE Code of Practice now recommends that test equipment is checked at regular intervals using a verification device such as a PAT Checkbox.  In addition, a record of the performance checks taken should also be kept and the revised document includes a specimen test instrument record form.

Where can I obtain the new Code of Practice?

Further details of the updated IEE Code of Practice for In-Service Inspection and Testing of Electrical Equipment are available by calling tel: 01438 313 311.

Steve Gallon explains why the integrity of a systems design depends on the reliability of conductors (wires, cables, and fibre optics), terminals, connectors, sockets, circuit boards, back plates, and the overall enclosure

Not wishing to teach Grandma how to suck eggs, it's worth reiterating electrical and electronic enclosures typically come in two grades: commercial and industrial.

Commercial cabinets ideally suit office and light industrial environments, whilst industrial equipment is normally more robust. The operating environment then determines the type of cooling, shielding, and IP protection needed.

These basic considerations establish the type of materials and plating or finishing needed for the enclosure to withstand the environment and successfully contain, protect and shield the device, to finally operate in.

Another consideration may be shock and vibration, especially in factories and environments prone to shaking as may found in the rail or mining industries.

Overall enclosure dimensions dictate the closest standard catalogue size available, and free space surrounding the cabinet works into calculations for selecting a cooling unit. (Heat exchanger and air-conditioner equations include the exposed surface area of the cabinet - enclosure bottoms and sides resting against walls and floors are ignored).

Intended use is important because some industries such as petroleum and food processing enforce rules and regulations concerning materials, finishes, paint, seals (for fluids and radiation), and explosion-hazard factors. For example, many food and beverage-processing plants mandate stainless-steel enclosures whilst other installations require GRP or polycarbonate enclosures.

There was once a time many UK panel builders and enclosure users overlooked GRP because they were of the belief that these products were not as strong as steel, however with today's advanced manufacturing techniques, modern GRP enclosures offer impact resistance (IK) ratings, equal to those of steel.

In addition and because of the material is inherently corrosion-proof, the suitability of GRP products for use in tough environments is amply demonstrated by their widespread adoption throughout Europe for extensive use in demanding applications which include traffic light controls, railway signalling, telecommunications and remote metering and monitoring.

Another issue crops up especially around telecommunications equipment, medical instruments, switchgear, machine tools, telephone links, and optical links. Many of these products are regulated by national standards, and special features may have to be incorporated in the cabinets.

Whenever possible, the designer should try to stick to standard enclosures as much as possible to keep costs down. What might be a custom job for one enclosure manufacturer may be a standard catalogue item for another. Standard enclosures, climate controllers, and accessories typically are available off the shelf or within two to three days. Modifications, however, may take four to six weeks!