Features

Kevin Beavan of PowerVar wonders why, despite the fact computers and other critical electronic systems can easily be damaged or destroyed by power fluctuations, UK businesses often choose ineffective solutions for limited cost savings


Many UK businesses will select surge protectors as their sole defence against power fluctuations without appreciating they can only provide rudimentary protection; without adequate protection there is a high likelihood of costly damage to computers and other sensitive electronic equipment. It is not just the damage to equipment that costs money, the more serious threat is the financial losses that can result from not being able to function normally.
There is one good reason surge protectors remain the prime choice; they are markedly cheaper than an effective solution. The savings in opting just for surge protectors are easily outweighed by the potentially massive costs resulting from any damage in terms of replacing or restoring any damaged components.
Part of the problem is a failure to understand the inherent limitations of the surge protector that make it so poor for protecting sensitive electronic equipment.
Technically even the term surge protector is misleading since it implies the device will protect against all surges. A more accurate term for these devices is surge diverters since they divert high voltage transients or impulses away from the electronic system they are supposed to protect.
surge diverters
Surge diverters work by utilising a threshold voltage, often called the clamping voltage, and may also have a clamping response or delay. When the clamping voltage is exceeded, any transient voltages are shunted to an alternative path and away from the protected equipment. Once the surge voltage drops below the threshold the diverter stops operating and the normal electrical conducting path is restored allowing current through to the equipment. The clamping time simply acts as a delay to the diverter so that relatively short surges are not diverted. Every surge diverter is designed to handle a maximum amount of energy without being destroyed.

Different technologies
To achieve their basic function, surge diverter products are manufactured with a variety of different electronic components including metal oxide varistors (MOVs), silicon avalanche diodes (SADs), and gas tubes. Each of these components functions differently and can affect the surge diverter’s performance. Yet it is rare for suppliers to actually state which technology is used in their surge diverter.
Characteristically MOVs have a high clamping voltage of between 300 and 500 volts and a slow response time. This means that voltage impulses of less than 500 volts will not be diverted and can enter the computer system unimpeded. The slow response time means that very fast, high voltages can pass through the MOV before it responds leading to additional damage. MOVs do have an advantage because they can handle significant amounts of energy yet they physically degrade each time they clamp which adversely affects future performance and ultimately leads to their failure.
To overcome these disadvantages, manufacturers turned to silicon avalanche diodes (SADs) that have a faster response time and improved long term performance compared with MOVs. However, SADs have a much lower energy handling capability and impulses that merely degrade an MOV may destroy a SAD. Surge diverter manufacturers will either use multiple SADs in parallel or use the components in conjunction with MOVs to improve the diverter’s energy handling capability.
The final type of component that can be found in surge diverters is the gas tube. These act like bouncers at a nightclub because they can handle almost unlimited amounts of energy although they are comparatively slow and have a high clamp voltage. This capability means they can protect all other surge diverter components during a catastrophic power disturbance.

Combining components
The limitations of the different component types means that some surge diverter manufacturers include all three technologies in an effort to improve performance by combining their relative strengths. Yet since MOVs and SADs are both electronic components, both are subject to failure from a high-energy impulse whether they are used singly or in combination with one another. The high probability of total failure is the reason why many surge diverters include an indicator light to show that the protective elements are no longer functioning. In most cases, surge diverter components operate ‘naked’ on the power line and it is almost certain that they will eventually fail.

The modern power supply
Another factor that limits the effectiveness of surge diverters as the sole line of defence is the characteristics of the modern power supply. Older generation computers used linear power supplies that required voltage regulation compared with modern systems which are powered by switch mode power supplies (SMPS). While SMPS are immune to voltage regulation problems they do require protection from impulses, power line noise, and, most importantly, common mode (neutral to ground) voltage.
A computer’s microprocessor makes logic decisions with reference to a clean, quiet ground that is destroyed by common mode voltage resulting in lockups, lost data, and unexplained system failures. Common mode voltage is very disruptive to a computer’s operation. Because surge diverters divert disturbing energy to ground they create common mode voltage. Effectively they convert a destructive disturbance into a disruptive one. And since surge diverters still allow substantial energy to pass through to the computer, damage may still occur.
To avoid these problems businesses need to move beyond simple reliance on power diverters and enhance their systems by fitting a power conditioner. A power conditioner is any device that provides all the power protection elements needed by the technology it’s protecting. Although the surge diverter remains a key element in the circuit’s protection for sensitive equipment its performance can be enhanced by the addition of an isolation transformer and a power line noise filter to provide a power conditioner.

Elegant power tools
Transformers are elegant power quality tools with unchanging secondary impedance. The benefit of using an isolation transformer is that bonding of neutral to ground on the transformer secondary is permitted and eliminates common mode voltages.
This enables the surge diverter to divert surge energy to ground without creating any common mode disturbances. Noise filters function in a similar manner by diverting EMI and RFI to ground and, when combined with an isolation transformer, their performance is enhanced.
This is of particular importance at the end of long-branch circuits where most computer equipment is installed. Wiring in buildings contains significant inductive and capacitive reactance giving rise to a unique frequency at which the system oscillates for every location in the building. This makes power line transients unpredictable.
Although a lot of research has been done by the IEEE to characterize a branch circuit impulse’s typical characteristics the reality varies greatly for every different location throughout the building. When a surge diverter is installed on a branch circuit it becomes part of the wiring system and the circuit impedance resulting from the wiring reactance affects the surge diverter’s performance.
This means the performance of surge diverters is often unpredictable since the varying electrical characteristics affect the frequency, wave form, and impulse’s rise time at different places throughout the building. This explains why a power diverter, when used as the sole form of protection, may reduce the frequency of hardware failures, while still making the system behave unreliably at times.
However, by fitting an isolation transformer and a noise filter, the surge diverter’s performance becomes predictable, controllable and repeatable.
On their own, surge diverters will limit transient impulses to hundreds of volts but by fitting an integrated power conditioner the same transient impulses are limited to typically ten volts or less. By fitting a transformer-based power conditioner far less of any disturbance is allowed to reach the critical electronic equipment ensuring improved functionality, greater reliability and enhanced longevity.

The BS 6651 British Standard on lightning protection has existed for decades. Now, a new standard, BS EN 62305, has been published for Britain. Compared to the BS 6651’s 118 pages, the 475-page BS EN 62305 is daunting. Expanding on an article in the May issue of Electrical Review John Sherlock of Furse (pictured right), offers an overview of the new standard and the consolation that, complex as the new standard may be, its key concepts are not alien, and, with relevant technical advice and support, it can be mastered

The British Standard on lightning protection (BS EN 62305) treats the protection of electrical and electronic systems as an integral part of an overall lightning protection scheme. Samad Khan, Product Manager, Electronic Systems Protection – Furse, reviews the new focus on protection against Lightning Electromagnetic Impulses (LEMP) and the role of Surge Protection Devices.

The importance of LEMP protection
In BS 6651, the protection of electronic and electrical equipment was included as a recommendation only, with its own independent risk assessment. As a result, protection was often fitted after damage had been suffered. With BS EN 62305, this protection has been made an integral part of the standard and is considered within the overall risk assessment detailed in part 2. Structural lightning protection cannot now be considered in isolation from transient overvoltage or surge protection.

Fusion power may be a long-term solution to the world's energy crisis, requiring the effective creation, capture and maintenance of complex engineering data today to help the scientists of tomorrow

Fusion power could be the fuel of the future, generating limitless amounts of energy with little environmental impact. But fusion requires technology so complex the scientists who began working on it 30 years ago are still laying the groundwork for its continued advancement by future scientists - who are currently just starting school. The world's leading fusion research programme is being carried out at the Culham Science Centre in Oxfordshire, where developers use Dassault Systemes' CATIA V5 and Enovia SmarTeam PLM, supplied and supported by Applied PLM Solutions, to create and maintain the vast amount of engineering data required to ensure that future generations can benefit from the work carried out today.

The UK Atomic Energy Authority (UKAEA) has been based at Culham since the 70s, when the experimental fusion energy machine was first designed and built as part of the Joint European Torus project (JET) - the flagship of Europe's integrated fusion programme. The same machine still forms the basis of the UKAEA's research today, though of course the design has gradually evolved as knew technologies and techniques become available. "CATIA V5 is used to model the entire device itself, plus the building and facilities which house it," explains Paul Carman, CATIA Manager at Culham. "This is a huge digital mock-up of JET, which consists of over a million parts built. Not only in CATIA V5 but in previous versions of CATIA."

Positive reaction
When work first began in the 70s, all designs were hand drawn (the UKAEA has 75,000 drawings to convert to CAD). With the evolution of CAD in the 80s, Carman and his team began using CATIA V2, then V3, then V4 and now V5. "We've certainly never seen a product to beat CATIA," says Carman, "There are other solutions which are good for designing lots of similar components, like in a washing machine. But we've got components 40 metres long that might contain a million parts, as well as miniature diagnostic electrical components. You need something that can handle all of that from one end of the scale to the other. CATIA has always fitted the bill."

Having been enthusiastic CAD users for the past 20 years, one of the biggest challenges facing Carman and his team is the amount of legacy data that exists for every detail of the project. "The thing that sets this project apart from other big OEM users of CATIA is the fact that we have a single large experimental machine which has remained in use, slowly evolving since it was built," explains Carman. "So we never have the opportunity to wipe the slate clean as they do in the automotive or aerospace industries. This means we have a massive amount of legacy data to contend with. Fortunately, one of the big advantages of V5 is that you can work with data from previous versions, so although we plan to convert everything into V5, we can still refer to the drawings we made years ago."

Future proof
In conjunction with CATIA V5, the UKAEA has also invested in ENOVIA SmarTeam, creating an extended enterprise level PDM system to enable the effective storage, sharing, maintenance and retrieval of engineering data between researchers and different agencies now and into the future. This capability is set to become increasingly important, as the European fusion community prepares itself for the next phase of its research: the construction of a new, international and even more advanced facility at Cadarache in France. The International Tokamak Experimental Reactor (ITER), which will begin being built in about 15 years time, will be the link between today's studies of plasma physics and tomorrow's electricity-producing fusion power stations.

Twice the size of JET, with over 10 million parts to design and construct, involving an increasing number of global participants (the project already includes Russia, China and Korea, as well as the rest of Europe), each with their own collection of domestic research agencies, ITER will be a collaborative engineering project on a truly epic scale. However, since the reactor is not expected to become operational for the next 35 years, the ongoing work of research centres such as Culham, and the effective collection, maintenance and storage of the engineering data produced remains absolutely vital. "Until ITER is built, JET will remain the only machine of its level of sophistication in the world," says Carman, "and it's important that we retain our world-class status ready for the transition to ITER. Effective PLM is a vital part of that process."

Applied science
In order to establish the most effective PLM system possible for such an important project, Carman and his team called on the expertise of Dassault Systemes' VAR, Applied-PLM. "Finding the right systems provider is critical for a project of this scale and potential longevity," explains Carman. "Any mistakes made in this business tend to live with us for a very long time, so we have to have reliable solutions and integrators we can trust."
In addition to the close support required for an effective PLM implementation, Applied has provided training and consultancy as well as bespoke software solutions to further enhance the integration process.

Shaun Clark Applied MD added. " Providing technical support, and training on this project has given us valuable experience and knowledge of the power generation sector and its PLM needs at the very highest level. With this valuable experience gained in such a complex environment we are confident that applying V5 PLM to others in the power generation industry will produce the kind of benefits that have been experienced by the UKAEA at Culham"

Lifetime guarantee
The researchers, scientists and engineers like Carman who work within the fusion community have to be patient. They know that the effort they put in today may not achieve the world-altering results they believe to be possible within their own lifetimes, but they strive none-the-less to make as many advances in fusion technology as they can before handing over to the next generation. With this in mind, the ability to create, record, share and lay down data has become one of the most significant challenges for Carman and his team since the project began.

In the 30 years Carman has been working at Culham, since the centre was first built, he has witnessed unimaginable changes in the technologies used to evolve the fusion project. "But," he says, "there are still some big changes to come. We won't quite see anything as dramatic as the move from 2D to 3D full digital mock-up, but PLM offers amazing potential, and we intend to make the most of it."

For further information visit www.AppliedGroup.com

Following on from the 17th Edition report in the last issue of Electrical Review, Ken West from Fluke (uk) highlights some of the changes he believes will have the most impact on the electrical industry

The 17th Edition of IEE Wiring Regulations was published in January 2008. Installations designed after 30th June 2008 are required to comply with BS 7671: 2008. As with the introduction of earlier Editions, the 17th Edition takes account of the evolutionary progress of standards in the international and, more particularly, in the European arena where it is necessary to incorporate the changes agreed in CENELEC with our European contemporaries.
This is a summary of some of the changes which are likely to have the most impact.

Protection against electric shock
The terms direct contact and indirect contact, which contractors have become accustomed to over many years, have now been replaced by the concepts of basic protection and fault protection, respectively.
Chapter 41 Protection against electric shock has perhaps seen the most radical changes in terms of layout and now incorporates requirements which were previously included in Section 471.
The protective measures of automatic disconnection of supply, double or reinforced insulation, electrical separation and extra-low voltage provided by SELV or PELV are recognised in BS 7671: 2008 (Regulation 410.3.3 refers) with the measure of Automatic Disconnection of Supply being the measure that is employed in almost every electrical installation. The protective measure of Automatic Disconnection of Supply was previously known as Earthed Equipotential Bonding and Automatic Disconnection of Supply (EEBADS).
For a 230/400V a.c. system, maximum disconnection times for final circuits not exceeding 32A are now 0.4s for a TN system and 0.2s for a TT system. 5s disconnection times (TN systems) and 1s disconnection times (TT systems) are only permitted for final circuits exceeding 32A, distribution circuits and street lighting circuits.
Where the protective measure of Automatic Disconnection of Supply is employed, socket-outlets with a rated current not exceeding 20 A for general use (by ordinary persons) are now required to be provided with additional protection by means of an RCD with a rated residual operating current I?n of not more than 30mA. Similar protection is required for mobile equipment with a current rating not exceeding 32A for use outdoors. An exception is permitted for socket-outlets for use under the supervision of skilled or instructed persons, eg. in some commercial premises or a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment.
The data given for limiting earth fault loop impedance values (now contained in Tables 41.2, 41.3 and 41.4) has been modified to take account of the nominal voltage of 230V as opposed to 240V, reducing the limits to about 95% of their previous values.

Protection against overcurrent
Chapter 43 Protection against overcurrent now includes the requirements previously given in Section 473 in the 16th Edition. Guidance on the overcurrent protection of conductors in parallel is given in Appendix 10.

Protection against voltage disturbances
Chapter 44 Protection against voltage disturbances includes a new Section 442, dealing with protection of low voltage installations against temporary overvoltages due to earth faults in the high voltage system and due to faults in the low voltage system. Protection against overvoltages of atmospheric origin or due to switching in Section 443 retains the existing requirements but enables designers to use a risk assessment approach when designing installations which may be susceptible to overvoltages of atmospheric origin.

Selection and erection of wiring systems
Chapter 52 - Selection and erection of wiring systems, now requires cables concealed in a wall or partition (at a depth of less than 50mm) to be protected by a 30 mA RCD where the installation is not intended to be under the supervision of a skilled or instructed person, if the normal methods of protection including use of cables with an earthed metallic covering, mechanical protection (including use of cables with an earthed metallic covering, or mechanical protection) cannot be employed. The requirements also apply to a cable in a partition where the construction includes metallic parts other than fixings, irrespective of the depth of the cable.
Table 52.2, giving data relating to cables surrounded by thermal insulation, provides slightly more onerous de-rating factors, to take account of the ready availability of material with improved thermal insulation.
Chapter 52 now includes busbar trunking systems and powertrack systems.
Chapter 52, in Section 525 and Appendix 12 refers to voltage drop. The maximum permitted voltage drop for lighting circuits is now 3% and for other uses 5%.

Protection, isolation, switching, control and monitoring
Simplification brings together the requirements previously in Chapter 46, Sections 476 and 537 of the 16th Edition in a single Chapter 53, which also includes a new Section 532 Devices for protection against the risk of fire, and another new Section 538 - Monitoring devices.

Earthing arrangements and protective conductors
Chapter 54?-?Earthing arrangements and protective conductors, retains the requirement that a metallic pipe of a water utility supply shall not be used as an earth electrode but also states that other metallic water supply pipework (such as a metallic water supply pipework of a privately owned water supply network) shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use.
The requirements relating to the installation of equipment having high protective conductor currents previously in Section 607 of the 16th Edition are now no longer considered to be a special location or installation and are moved to the General Rules. The requirements are to be found in Regulation Group 543.7.

Low voltage generating sets
Requirements for low voltage generating sets including small-scale embedded generators (SSEGs) such as wind turbines and photovoltaic (pv) generators are now to be found in Chapter 55.

Luminaires and lighting installations
A new series of requirements for fixed lighting installations, outdoor lighting installations, extra-low voltage lighting installations, lighting for display stands and highway power supplies and street furniture (previously in Section 611) are given in Section 559 - Luminaires and lighting installations.

Safety services
Requirements for safety services such as for emergency escape lighting, fire alarm systems, installations for fire pumps, fire rescue service lifts, smoke and heat extraction equipment, are dealt with under Chapter 35 (safety services) and Chapter 36 (continuity of service), the latter requiring an assessment to be made for each circuit of any need for continuity of service considered necessary during the intended life of the installation. In line with IEC standardisation, Chapter 56 - Safety services, has been expanded.

Inspection, testing, verfication and certification
A fundamental requirement has been introduced under Regulation 132.13 requiring documentation (including that required by Chapter 51, Part 6 and Part 7) to be provided for every electrical installation.
The requirements for inspection, testing and certification previously in Part 7 of the 16th Edition are now to be found in Part 6. Very little has changed but perhaps worthy of note is that the minimum values for insulation resistance is raised to 0.5M? for SELV and PELV (when measured at 250V) and 1.0M? for low voltage circuits up to a nominal voltage of 500V (when measured at 500V), and for nominal voltage above 500V (when measured at 1,000V).
Measuring instruments and monitoring equipment should be chosen to meet the requirements of the relevant parts of BS EN 61557 (see Appendix 2 of the 17th Edition). Where such equipment does not meet the requirements of this Standard, it must provide for no less a degree of performance and safety.
A caution is provided to warn that when testing in potentially explosive atmospheres appropriate safety precautions are necessary.

Special installations or locations
A number of changes have taken place in relation to special installations or locations. For a start, the requirements are now embodied in Part 7 (rather than in Part 6 as in the 16th Edition).  The main changes are in the following Sections:

Section 701: Locations containing a bath or shower
Section 702: Swimming pools and other basins
Section 703: Rooms and cabins containing sauna heaters
Section 704: Construction and demolition site installations
Section 705: Agricultural and horticultural premises
Section 706: Conducting locations with restricted movement
Section 708: Electrical installations in caravan/camping parks and similar locations

New special installations and locations
Section 709: Marinas and similar locations
Section 711: Exhibitions, shows and stands
Section 712: Solar photovoltaic (pv) power supply systems
Section 717: Mobile or transportable units
Section 721: Electrical installations in caravans and motor caravans (previously in Section 608 of the 16th Edition)
Section 740: Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses
Section 753: Floor and ceiling heating systems.

Section 611 of the 16th Edition relating to highway power supplies is now incorporated into Section 559.

Appendices 1 to 7
Necessary changes to Appendices 1 to 7 have been made, including in particular the Installation and Reference Methods and tables in Appendix 4.

New appendices
Appendix 8:  Current-carrying capacity and voltage drop for busbar trunking and powertrack systems
Appendix 9:  Definitions - multiple source, d.c. and other systems
Appendix 10:  Protection of conductors in parallel against overcurrent
Appendix 11: Effect of harmonic currents on balanced three-phase systems
Appendix 12:  Voltage drop in consumers' installations
Appendix 13: Methods for measuring the insulation resistance/impedance of floors and walls to Earth or to the protective conductor system
Appendix 14: Measurement of earth fault loop impedance: consideration of the increase of the resistance of conductors with increase of temperature
Appendix 15: Ring and radial final circuit arrangements, Regulation 433.1

Ken West gives thanks to Geoffrey Stokes and Benchmark Electrical Safety Technology for their input

The Fluke 1650 Series of Multifunction Installation Testers are ready for the 17th edition - new purchases as well as those already in the field. They are easy to operate, feature a large backlit display with a wide viewing angle, have an ergonomic design, and a padded neck-strap to free the hands of the operator. The Fluke 1650 Series comprises three models. The Fluke 1651 meets the requirements of Part P; the Fluke 1652 (pictured) and 1653 can perform automatic trip time and tripping current level (ramp) tests of residual current activated devices (RCDs) - both DC-sensitive and delayed-response types. The advanced capabilities of the 1653 also enable storage of results, which can be uploaded later to a PC for software analysis, and measurement of earth resistance and phase sequence.

With Lightning Protection facing its biggest changes in decades, Dave Allen, Operations Director of Omega Red Group - casts a critical eye over the readiness of the construction industry for the introduction of the new British Standard BS EN62305: Protection Against Lightning

The requirements of the new standard are much more comprehensive and progressive than before and it has taken Omega two years to fully digest its provisions. During that time the new and existing standards ran in parallel to enable lightning protection companies and their customers to get up to speed - from September this year, the new standard is the only show in town. But has the industry used the time available to adequately prepare itself for the changes ahead?

More than three times the size of its predecessor, the new British Standard BS EN62305 uses modern protection techniques for the design and construction maintenance of lighting protection systems.

When designing a power continuity plan for a data centre or any other type of critical operation, power quality should feature high on the tick list. Poor power quality can be as dangerous to critical loads as a partial or complete mains power supply failure and lead to intermittent data corruption and hardware failure explains Robin Koffler, general manager, Riello UPS

The actual quality of a mains power supply is measured in terms of its waveform, voltage and frequency and the presence or not of a variety of power problems including blackouts and momentary interruptions, sags, brownouts, surges, spikes and transients, electrical noise, frequency variations, and harmonics.


Of the eight most common types of power problem, harmonics is perhaps the least understood and planned for. Harmonics are voltage or current waveforms the frequencies of which are multiples of the fundamental. In Europe the fundamental frequency is 50Hz (50 cycles per second) and the multiples are ordered into a specific sequence. For example, the 2nd harmonic is 100Hz (2x50Hz), 3rd harmonic 150Hz (3x50Hz) and so on.


Often overlooked as a potential threat, harmonic pollution is a growing problem in the UK because its presence can be disruptive not only to a polluted site but also other customers of the utility provider. Most consumers are unaware that they are responsible, under the terms of their electricity supply contract, for the total harmonic values generated at the Point of Common Coupling (PCC) and building incomer when new installations are made. Acceptable levels are published within Engineering Recommendation G5/5-1, from The Energy Networks Association (www.energynetworks.org).  The critical point for new installations is that where the specified harmonic levels cannot be met, consumers must secure approval from their utility provider before connection or face penalties.


Within a new data centre, for example, the most prevalent loads will be high-end servers and associated data processing hardware, which are powered by Switch Mode Power Supplies (SMPS). It is the power supplies themselves which form the load on the electrical supply, and being non-linear draw their own power in regular modulated pulses of current, rather than as a continuous linear current. This action can lead to the generation of high levels of harmonics, especially where a large number are supplied from a three-phase mains power supply. Of the harmonics generated, it is the set known as Triple-Ns or Triplens whose harmonic orders are multiples of three and include 3rd, 9th and 15th. Other harmonic orders, not in phase with one another, simply cancel each other out and though still considered to degrade power quality, their impact is less severe.


When harmonics are present in a mains power supply they can lead to voltage distortion, overheating of building wiring circuits, neutral conductors, supply transformers and switchgear, and nuisance tripping of breakers. Harmonics can also cause disruption to equipment on the same supply and lead to random failures. Within a data centre environment their presence can therefore prove disastrous.


It is the 3rd order harmonics which potentially are the most serious within a three-phase mains supply (Fig. 1.11) due to the summing effects within its neutral conductor. As these harmonics are multiples of three, they are all in phase with one another and therefore their magnitudes are added together. Their effect is to greatly increase the current flowing within the neutral and this can lead to potential overload and affect associated switchgear.
Whilst, it is accepted practice to balance loads across the phases of a three phase mains power supply, even this will not counter-act the impact of Triplens. This is because Triplens can generate neutral currents up to 1.73 (?3) times the average currents present. This additional loading (and heat generation) can degrade upstream neutral conductors and/or wiring insulation leading to potential breakdown and a fire hazard if unmanaged.
Whilst SMPS may be the most common source of harmonics, others include: rectifiers, variable speed drives, discharge lamps, fluorescent lighting, mercury and sodium lamps. When designing a power continuity plan, it is therefore vital that all site loads are assessed for their impact and effect on overall power quality.

Mitigating Harmonic Pollution
Data centres are now one of the most concentrated users of SMPS in the racks of servers they deploy over relatively small footprints. Whilst most users apply a concerted effort to manage the resultant air conditioning demands, few realise the potential harm that can be done due to harmonic pollution.


Within such an environment it is common to select a centralised approach to power continuity and install an Uninterruptible Power Supply (UPS) and standby generator. Whilst the UPS will power critical loads, the generator will provide power to essential services such as air conditioning and security systems, as well as provide backup to the UPS should its battery set be discharged.


The UPS can therefore be considered to fit ‘in-line' between the loads and the mains power supply. In addition to providing power protection to the loads, it should also protect the mains power supply itself from any harmonics generated by the loads themselves.
However, it is again not commonly known that UPS themselves, by way of their design, also generate harmonic pollution. For any UPS this is typically stated as Total Harmonic Distortion (THDi). Care has to be taken when comparing different THDi values as these can differ when contrasting the two different types of on-line UPS (transformer-based and transformerless) and also with regard to the percentage of load applied for each measurement.
Within a UPS it is the rectifier that connects to the mains power supply and converts the mains alternating current (ac) into the levels of direct current (dc) required to power the inverter and charge the battery.


For transformer-based UPS, rectifiers are typically six or twelve-pulse, dependent upon the thyristor number and configuration. A six-pulse rectifier at full load will typically generate a THDi of around 29% and a 12-pulse around 8%. To reduce these values further a passive harmonic filter can be installed alongside the UPS. The obvious disadvantages of this approach being increased capital cost, wiring, installation, loss of efficiency and increased footprint. Harmonic filters can be added post-installation but further installation costs and downtime need to be planned for.


Transformerless UPS have a different type of front-end whose configuration is usually that of a rectifier-booster. THDi levels of less than 7% can be achieved and reduced to less than 4% when an active harmonic filter is installed. For some designs, the harmonic filter may be positioned inside the UPS cabinet reducing impact on overall footprint but still resulting in higher capital and operating costs.


Harmonics is just one research and development area for UPS manufacturers with the goal of producing zero-impact uninterruptible power supplies. The latest developments offer THDi levels of less than 3% using IGBT-based (Insulated Gate Bipolar Transistors) rectifiers and it is forecast that this approach will be adopted as a standard for UPS up to 200kVA or more over the next one to two years. Achieving a zero-impact also covers the areas of operating efficiency and input power factor. Such designs can now offer efficiencies of 96-98% and input power factors close to unity. Their cumulative effective offers high reliability systems that can achieve 35% energy savings and quicker capital payback than traditional UPS.
Harmonics is therefore a ‘hot-topic' when it comes to power continuity but one most people avoid. The subject can appear complex but requires thought at the planning stage of any new installation if the systems are to deliver the benefits intended and satisfy the requirements of the utility providers who in the end has the ultimate power.

Erich H. Reuss, of DEHN (UK), discusses the potential problems associated with MOV combined arresters, and urges engineers to be aware of the limitations of these devices

According to European Standard EN 61643-11, low-voltage surge protection devices are classified as types 1, 2, and 3. Nowhere are these discrepancies more obvious than with so-called combined arresters, where a multitude of names such as combined arrester set, type 1/type 2 combination, B-C arrester, T1+T2+T3 arrester or even BCD arrester are a recipe for confusion, leading to the situation where different products are available with parameters, protective effects and even different wave shapes which deviate from one another.

Design engineers face many challenges with the layout of electrical and electronics enclosures, and one frequently asked question addresses the location of thermal management products. The goal is to position the equipment so as to provide adequate protection from temperature extremes as well as preventing the formation of condensation. Phil Herbert of Stego (UK) explains

Heating and cooling devices in enclosures are designed to protect electrical and electronic components primarily from condensation and also from low and high temperatures. However, even with the appropriate equipment and controls, problems may arise due to incorrect positioning within the enclosure.

Heating
As the requirement of heaters for the prevention of condensation formation becomes more widely acknowledged, engineers and design teams must consider the equipment placement in an enclosure along with the devices they are intended to protect. It is not uncommon to find systems added after the fact, fitted into whatever space remained. While this may be the only solution available, it could potentially be the cause of other problems such as creating ‘hot spots' or ‘heat nests' near temperature sensitive electronics.

Ideally, most heaters will perform optimally when mounted near the bottom of an enclosure and used in conjunction with a separate controller such as a thermostat and/or hygrostat. With the controller located in an area of the cabinet that is representative of the average temperature or humidity requirement, the heater should then be placed in a position near the bottom but not directly beneath the controller. This placement will ensure that the controller is not influenced by direct heat from the heater.

For smaller areas, heaters will generally provide adequate heating power to maintain temperature and humidity control. For example, a 900 x 600x 600 wall mounted, insulated stainless steel enclosure with a desired interior temperature of 10°C with an ambient temperature of 0°C will require a 100W heater:
Power (W)  = (enclosure surf. area) x (delta T) x (heat transmission coefficient)
= (1.014 m2) x (10 K) x (4.5W/ m2K)
= 91W
In the case of Fig. 2, with all other parameters remaining the same, the height and width have been increased to 800 and 600mm thereby increasing both the air volume and the surface area. Accordingly, the required heating power has also increased:
Power (W)    = (encl. surf. area) x (delta T) x (heat transmission coefficient)
= (1.428m2) x (10 K) x (4.5W/m2K)
=   129W
For larger enclosures with greater heating power requirements, standard heaters are not a practical solution. As Fig. 2 shows, the most effective heat distribution is accomplished by a fan-assisted heater with greater air circulation to ensure rapid and efficient control of the temperature and/or humidity.

However, as mentioned previously, space for a tall heater is not always available. Packing densities have increased as more equipment is designed into smaller spaces. In the case of an example enclosure, only 100W of heating power is required, but the high packing density limits the available space for a convection heater.

The alternative is a compact fan-assisted heater positioned to provide adequate heat distribution throughout the cabinet. The position of the controller can vary depending on the air flow and temperature gradient, providing that it is not impacted by direct heat.
In any circumstance where a heater is required, the location of all other equipment relative to a heater should be carefully considered. Most heater manufacturers recommend a minimum distance of 50 mm from components inside an enclosure. However, the temperature sensitivity of each component should be assessed along with the heater temperature profile to ensure no damage will occur. (Calculations are available online at  http://www.stego.co.uk/)

Cooling
Enclosure cooling solutions range from filter fans to heat exchangers and high performance air conditioning systems. In all cases, the intent is to remove excess heat from the cabinet interior. Whether naturally or mechanically achieved, the basic principle of heat rising is utilized.

One common and simple method is by using forced air ventilation, which is most effectively achieved with filter fans. Since outside air is introduced into a clean sealed environment, high efficiency filters are required to maintain that integrity.

This arrangement with the filter fan (air intake) at the bottom and the exhaust filter near the top is highly effective by using cooler ambient air to displace the warmer air inside the enclosure. The exhaust filter is typically mounted as close to the top of the cabinet as possible to take advantage of natural convection forces, and should also be located as far as possible from any heat producing components. If designed properly, the air path created by the filter fan system will pass through critical areas that are to be cooled, allowing for maximum cooling efficiency. Ideally, a control thermostat should be located in one of the critical areas where it will turn the fan on and off when temperature set points are reached.
Many other arrangements are possible, even so far as letting ventilation occur naturally. One such system would allow for passive cooling by letting the warmer air escape through a roof-mounted vent. Again, the key is that cooler air is used for displacement, so an intake filter would be required near the bottom of the cabinet.

Conclusion
Designing the layout of cabinets and enclosures that house sensitive electronic components is a challenging task. While it may seem a less important consideration than many other aspects of proper control system design, the suitable placement of heating and/or cooling components can have a major impact on system operations. Following these simple guidelines will help ensure system functionality and long service life.

The introduction of BS EN 62305: Protection Against Lightning on 1 September 2008 is already having a profound impact on the industry and its customers says Colin McElhone, managing director at Omega Red Group

Having spent the past two years preparing for the introduction of the new standard, it shouldn't really be a surprise now it's here.

But like many in the lightning protection industry I have spent my entire working life working under its predecessor and knew it inside out. Doubtless we had all become comfortable with the old standard.

BS EN 62305 has given us new ways to apply concepts outlined within the standard to tackle problems with a logical, systematic approach. In BS 6651 basic surge protection was mentioned under Annex C. BS EN 62305-4 Electrical and Electronic systems within structures is a complete document dedicated to the problems, and solutions, encountered due to lightning current and induced surges. Mike Forsey, technical manager at DEHN (UK) explains

The new standard calls for a risk assessment calculation to be carried out, part of the assessment determines if surge protection is necessary and if so what type of surge protection device, or devices, needs to be installed.

With the increase of electrical and electronic systems being used within both business and private environments the continuing reliance, functioning and uninterrupted use of these systems is becoming essential. Equipment ranging from the basic power supply and distribution systems to specialist equipment for computer, networks, building management (BMS), telecommunications, control and security, etc now play an essential role in our lives. Damage caused by lightning and switching related events has not only a direct repair cost but also an indirect consequential cost due to down time, data re-instatement, etc.

Using the protection principles outlined in BS EN 62305-4 the protection of such systems against surges is based on the principle of lightning protection zones (LPZs), in which the building or structure being protected is divided subject to the location of the equipment within the structure. Using this approach, suitable zones can be defined according to the number, type, immunity and sensitivity of the electrical and electronic devices or systems present within the structure. Sizes ranging from small local zones to large integral zones that can encompass the whole building can be established. At the boundary of each internal zone, equipotential bonding must be carried out for all metal components and utility lines entering the building or structure. For mains power, data, telecomm, etc this is carried out with the use of suitable surge protection devices.

As can be seen from the diagram below a lightning current arrester, SPD Type 1,  (Waveform 10/350) is required at the interface of zones LPZ0/1 for any cable entering from a zone LPZ0A. At the boundaries of LPZ1/2 and higher a surge arrester, SPD Type 2 (Waveform 8/20) would be used.

The same principle is used for all conductive cables entering the structure be they mains power, telecomm, data, networks or CCTV.

Spatial shielding within the structure also forms part of the protective measures. By correct design and placing of suitable shielding the magnetic fields within the structure can be attenuated.

Protection management
For new buildings and structures, optimum protection of electrical and electronic systems within the structure can be best achieved cost-effectively if these systems are designed together with the building and are taken into account before its construction. For existing buildings and structures, the cost of this protection is usually higher than for new buildings and structures. If however, the LPZs are chosen appropriately and existing installations are used or upgraded, the costs can be reduced. If the risk analysis as specified in the new BS EN 62305 -2 shows that surge protection is required, this is best achieved if:
- The measures are designed by a lightning
protection specialist having knowledge of
electromagnetic compatibility;
- There is close co-ordination on all aspects of
the work between the building experts (e.g.
civil and electrical engineers) and the surge
protection experts;
- An appropriate management plan is
adhered to.

The rising cost of energy and the focus on "green issues" has put great responsibility on every commercial building manager and owner. The pressure is on to make continuous energy savings and this must be achieved through effective building management. Systems that track the energy performance of a building in real time can identify all areas where there is need for improvement, allowing the owner or occupier to take steps to further improve energy efficiency. Finding the best building management system and the most effective long-term solution to controlling energy usage is the challenge

The KNX Standard is the world's only open standard for building control and automation. The KNX standard is approved as: 
- European Standard (Cenelec EN 50090 and CEN EN 13321-1)
- International Standard (ISO/IEC 14543-3)
- Chinese Standard (GB/Z 20965) 
- US Standard ( ANSI/ASHRAE 135)

The standard has been adopted by many international manufacturers, who together provide a vast array of KNX certified products for a range of building control applications. The installation of KNX products can make major energy savings of up to 60%, significantly reducing the carbon footprint of a building. This is truly green sustainable technology that can be applied to small and large buildings alike.

An ever growing number of building owners are accepting KNX as a technology to achieve maximum energy efficiency. It has a number of advantages over alternative solutions including the ability for it to be integrated with any type of BMS thanks to its open protocol OPC Gateway. Once this integration has been achieved, KNX brings local and zonal control to every area of a building.

The over-riding advantage of KNX is it provides a holistic approach to efficient energy usage and is not limited to individual control of lighting/ HVAC/ intruder alarms/ audio visual systems/ household appliances/ blinds/solar control and automatic window control, façade management/ metering and monitoring applications. The KNX platform has been adopted by many and highly respected major manufacturers with their vast choice of products covering all these product lines. This is important to building owners in the longer term, as any installation is future proofed. Contractors, consultants, specifiers and end users looking for an open solution for building control applications are increasingly heralding KNX and recognising the drawbacks of proprietary solutions or various hardware-based controls. Were they to choose a proprietary protocol from a single manufacturer or integrator, then they would be beholden to that company and its technology. This could be problematic during the life cycle of a development. With KNX, in the event of a certain product no longer being available, there will be an alternative to replace it.

As KNX covers such a diversity of applications using one standard, it means cabling networks can be much simpler. A single twisted pair cable can often suffice, with multiple elements all operating together on a single network. KNX controlled devices are generally based around the standard green KNX bus cable (i.e. twisted pair) but can be run across radio bus (wireless), ethernet (structured cabling), fibre optic and occasionally power line.

A number of manufacturers have also developed ‘gateways' to other control protocols, such as DALI (digital addressable lighting intelligence). These simple devices are used to expand the capability of KNX control systems to provide the complete solution for a building. KNX has also worked closely with management-level protocols such as BACnet to enable a close co-operation between these two standards when the project requires additional integration.
What also helps to maintain KNX's superiority is that every KNX-compliant piece of equipment has been fully tested and certified to this highly stringent standard by an independent regulatory body. It is only at this point that it can carry the KNX logo, as controlled by the international KNX Association of Brussels. Therefore there is total confidence in reliability and interoperability, whatever KNX devices are chosen.

Another advantage of KNX is the ability to seamlessly add functions that work away in the background and go largely unnoticed. What is more, KNX is distributed technology so in the event of failure of one element of building services, the rest carries on regardless.
With the pressure on energy management, it is vitally important to make the most effective use of energy. For instance, a lighting control system can be simply configured to only put the lights on when someone is present in the room, and can monitor natural daylight levels to dim or turn the lights off when enough ambient light is present. A drive through any town centre or industrial estate at night will reveal there is much energy for lighting being wasted and this could be preserved by employing simple measures. Effective use of lighting control alone can result in highly significant energy savings and when integrated with shutter and blind controls, solar panels, façade management and effective monitoring, there are potentially massive savings.

Indeed, climate control is a critical area within office buildings and a KNX system will know when the blinds are closed as an inherent feature. At the same time, heating and ventilation can be regulated separately in each room via temperature sensors. During the winter, when warmth and light make an even greater contribution to the comfort that a building provides, KNX technology regulates climate and lighting for each room in accordance with the outdoor temperature and prevailing daylight levels. Investment return on each KNX device is highly geared as each product on the bus, such as a movement detector, can not only switch lighting as in conventional installations, but can also set back heating when a room is empty.
Another growth area is building security. In any property at night, for example, the KNX system can act as an "electronic watchdog" deterring crime. Motion detectors, glass break sensors and electronic shutter control can be connected to an alarm system or emergency call circuit. If there are suspicious noises, a panic button can be pressed and the lights go on and the shutters open. Should any alarm conditions occur, they can be conveyed by email or SMS and to a mobile phone.

Thus a KNX based intelligent building system offers benefits in terms of energy savings, comfort, lifestyle and security - as well as some more unexpected advantages. A growing application is in the area of assisted living where KNX can help in the execution of daily household tasks which otherwise may not be accomplished.

With the continued development of new KNX products from various manufacturers, the ability to record energy consumption data and to process this data for accounting and billing software products is now readily available.

Connection of the metering devices to the KNX bus system and coupling to IP allows the display and processing of the data on a touch panel. The visualisation can display the recorded and current data of every metering point. The conversion of the data with export functionality to Excel can be achieved with the push of a button and allows post-processing for the various accounting and billing software products currently available.

KNX metering products can record data such as heat consumption using heat meters; power consumption (different energy meters, flexible with IR interface); water consumption (water meter with KNX connection); fill level meter for tank content (oil, water, liquids).
The development of a worldwide standardised system to meter electronically the consumption of different commodities and to convert data for external post processing offers a number of advantages.  For example, customers can get an overview of the current consumption data at a push of a button and can identify irregularities faster and therefore save time, money and energy. A number of KNX manufacturers are involved in on-going development of meters.

There is a growing network of integrators who have joined KNX UK to share their experiences, to help to promote the KNX standard and assist consultants as well as building owners in achieving the optimum solution for their building. They can get involved at the drawing stage of any project, liaise with the client and install a KNX infrastructure that can be developed as the building itself develops or its use and occupants change.