Features

John Clarke, of Zucchini EdM Transformers, discusses the environmental and cost-saving effects of cast-resin transformers

A transformer is a device that transfers electrical energy from one circuit to another through a shared magnetic field. A key application is to ‘tap off' 11,000 volts (11 kv) of electrical power from the national grid and step it down to 415 volts, which is the normal 3-phase electrical power system used in the UK for commercial, institutional or industrial applications. A transformer therefore makes raw electricity ‘usable', as well as allowing it to travel through cables. In fact, most of the world's electrical power has passed through transformers by the time it reaches the consumer.

Large, high-power transformers, in particular, need to have a built-in cooling facility to transport heat from the interior. Thus, one of the numerous ways of classifying transformers is according to cooling type. For example, for power transformers rated up to a nominal kVA, natural convective air-cooling, often fan-assisted, is adequate. Traditionally, oil transformers relied on highly refined mineral oil as a cooling medium, while the latest generation cast-resin transformers, the transformer core is insulated by a thin coating of inorganic material.

FIRE SAFETY
Over the last decade, remarkable advances in materials technology and manufacturing methods have fostered the popularity of cast resin transformers, particularly in fire-sensitive locations such as high-rise structures, hospitals, and public buildings where the transformer is located indoors and a fire outbreak would be particularly hazardous because of the high density of people.

Safety is high on the list of benefits provided by cast resin transformers. The advanced epoxy mixture used in EdM transformers is a non-hazardous material, which is both fire-resistant and self-extinguishing. Even when the material is exposed to arcing, no toxic gases are produced, and the transformer can be safely situated close to the load, saving on cabling, civil works and transmission loss.

Another key benefit is the fact that cast resin transformers require no maintenance during their lifetime.

NON-POLLUTING
Compare all these benefits with the disadvantages of traditional oil transformers with their relatively low fire point, pollution potential, higher installation costs (due in part to the fire-protection and containment measures often needing to be installed along with the installation), and a high maintenance requirement.

Oil-cooled transformers are not, it has to be said, a favourite with insurance companies. Oil, of course, is a non-renewable resource, while EdM transformers are insulated in a sustainable material, which has been developed and refined over 15-years to comply fully with European Union and national directives on the protection of the environment. Indeed, they do not pollute the environment where they are installed and are therefore recommended for all ISO locations, a standard that helps organizations minimise the negative effects of their operations on the environment.

AGGRESSIVE CONDITIONS
As well as protecting the environment, the high quality epoxy resin filled with silica and trihydrate alumina, that have developed to encapsulate transformers, stops moisture  ingress, thus preventing electrical breakdown under load, as well as inward pollution from the environment. This not only makes the transformers ideal for damp or dirty conditions, but extends the life of the transformer's working parts and eliminates maintenance. EdM transformers are also coated in high-vacuum chambers to reduce air and other gases in the resin that could produce partial earth discharges. In effect, they thermetically seal the transformer's core. As a result, consultants and specifiers looking for standard transformers with power outputs in the range of 100 to 3,500 kVA (and up to 16,000 kVA for specific projects), get complete peace of mind.

Another point is cast resin transformers do not have the noise and vibration problems associated with oil-based machines.

Cast resin transformers are now available in different specifications to meet the needs of the climate or hazardous and unforgiving environments, exceptionally cold ambient temperatures and environments with high fire risk.

MORE ENVIRONMENTALLY FRIENDLY
One of the most gratifying outcomes of installing environmentally friendly technology in recent years has been the realisation by individuals and companies that saving the environment  - can also save money! As well as being favourably priced, cast resin transformers are exceptionally energy-efficient, producing a high transformation yield and thus consuming less input energy.

At Zucchini EdM, we have developed ‘mathematical models' highlighting the savings that can be made by the user of a given electrical item on a case-by-case basis. For example, a 1,000 kVA energy-efficient transformer can produce savings of  €30,000 over a 20-year period, the equivalent of 20 MWh per year. The European Commission has assessed if equipment such as this were brought into general use, emissions of 11 million tonnes of carbon dioxide - equivalent to the electrical power used by 5 million homes - would be avoided.

When deciding whether to deploy static or rotary Uninterruptible Power Supplies (UPS), there is no easy way of weighing up comparative advantages and disadvantages. UPS systems vary greatly in physical size, weight, form factor, capacity, supported input power source, technological design, and cost.  APC by Schneider Electric makes a comparison of 3-phase static and rotary UPSs to support a data centre 

The Market
Compared to the massive global market share which static UPS systems enjoy, rotary UPS systems occupy only a small niche. According to IMS Research, only 4.3% of projected worldwide UPS revenues in 2008 will be rotary UPS systems, while the remaining 95.7% consists of static UPS.

They are also a niche within the data centre market where static UPS predominate at power levels of 500 kW and below, with the segment between 20 kW to 200 kW almost exclusively static.

Rotary and flywheel UPS systems begin to appear in use in the 200 kW to 500 kW range, for niche applications such as military and industrial. For mega data centres (< 100,000 square feet) where 500 kW to multiple megawatt UPSs are required, both architectures are present.

The Technologies
A UPS system is defined as static because, throughout its power path, it has no moving parts. The rectifier inside of the static UPS system converts the incoming utility AC current to DC, and the inverter converts DC back to clean sine-wave AC to supply the load. Regardless of the details of the internal topology, at some point there is a place where DC current interfaces with the ‘energy storage' medium - most commonly batteries, in which case it charges the batteries and receives power from the batteries when the utility power supply is distorted or fails.

In data centre applications, a 3-phase static UPS typically has a battery runtime of 5 to 30 minutes. Runtime is dictated by the size and criticality of the load together with available battery capacity. Static UPS battery systems are generally sized to allow enough time, during an outage or disturbance, to support the load while the power source shifts from utility to a standby generator. Should the generator power fail to come online, the UPS is configured with enough battery runtime and technological intelligence to allow for an orderly shutdown of the load.

The rotary UPS system is so-called because rotating components (such as a motor-generator) within the it are used to transfer power to the load. The true definition of a rotary UPS system is one whose output sine wave is the result of rotating generation.

Why the choice?
Rotary technology has been utilised for many years and came into prominence at a time when loads would commonly exhibit a low power factor and high harmonics. At first synchronous condensers which over time began to incorporate motor generators, inverters and rectifiers. Batteries or flywheels were then added for energy storage and the modern rotary UPS system was born. Ironically, the original reasons rotary UPS systems came into being, do not exist for data centre managers exist since most IT equipment is power factor corrected.

Characteristics of rotary and static UPS sytems

  • Investment

Rotary UPS systems are a fixed investment, usually oversized to accommodate future, unknown load requirements. In addition to being neither modular nor scalable (as with some modern static UPS), the upfront costs may be as much as 40% more than a comparative static system.

Auxiliary equipment costs for rotary UPS systems may also be higher since they require an external bypass switch together with special ventilation equipment to purge fumes from working areas. In the case of diesel rotary UPS, the construction of an additional building may be required to house the unit.

  • Maintenance

For a given level of availability, mechanical equipment such a rotary UPS system requires a maintenance regime incorporating weekly, monthly, annual and five-yearly checks. By comparison and depending on environment, most static UPS systems usually require only one annual maintenance visit.

While in general electronic equipment such as static UPS has a more extended useful working life than mechanical rotary UPS, they do require an investment in maintenance of, for example., batteries, in addition to occasional replacement of cards and circuit boards.

 

  • Environmental Impact
Static UPS systems tend to be installed in a building or data centre whereas rotary UPS tend to be outside in a specially built enclosure. Because they often rely on flywheels as their source of energy storage (providing only up to 10 seconds of back up), they may also be noisier as diesel generators are activated during any power ‘situation'. Batteries and flywheels both support the load until back up mains flows, however, by virtue of their greater runtime, battery supported systems may not require generator power unless the outage is extensive (most tend to be of very short duration).
  • Reliability
Both systems are quite reliable and an analysis of the MTBF of major components does not reveal any great advantage either way. However, the weak link is diesel generation which, according to the IEEE (standard 493) experience quite high failure rates (one start in 74). This may present an unacceptable risk to data centre operators.
  • Efficiency
Static UPS topologies run more efficiently than their rotary counterparts over the entire normal operating range with a very significant advantage below 50% load. Rotary UPS systems also appear to sustain higher fixed losses such as .that utilized to preheat the engine coolant and lubrication systems, to power the controls, flywheels, and pony motors associated with the rotary UPS at zero load, and the frictional and windage losses. These standby losses represent the amount of energy required to keep a motor running or to keep a flywheel spinning.
  • Architecture
Rotary UPS systems lend themselves to centralised architecture, whereas static UPS have the flexibility to also deploy as distributed UPS solutions. The advantage with rotary is that the all aspects of power backup can integrated into a single solution. While this may be attractive from a management perspective, it does present the potential of a single point of failure scenario.

Conclusion
There is a broad range of applications for static UPS systems and certainly they are the solution of choice for data centres where there is a trend towards to modular, pre-engineered solutions for all aspects of physical infrastructure including power protection, distribution and cooling - coupled with a need for high availability and high efficiency solutions. Rotary UPS systems are perhaps more suited to environments characterised by multiple short inrushes of power, for example satellite and broadcast stations. Some rotary UPS systems are used in high security installations to prevent electrical eavesdropping, as a cost effective alternative to tempest filters.

For more details, please visit www.apc.com/gb and download a copy of APC white paper #92 "A Comparison of Static and Rotary UPS".

The introduction of two key European Directives in 2005/2006 changed the face of emergency lighting--and most particularly emergency lighting testing--forever. These two Directives--EN50172 Emergency escape lighting systems and EN62034 Automatic testing for battery powered emergency escape lighting--opened the door to new opportunities in the emergency lighting domain, and brought with them implicit challenges. Paul Wilmshurst explains

To-date, many of the challenges faced when implementing emergency lighting schemes have derived from a disjoint in conventional design approach. Emergency lighting schemes have traditionally been addressed by disparate systems--systems that are typically split along the boundaries of architectural and commercial energy management lighting.

The 2005/2006 European directives, coupled with significant advances in lighting control and monitoring technology, are creating a trend towards a more holistic approach to emergency lighting system design. This approach ‘engineers in' the emergency lighting functionality--most notably the mandatory testing regime--across the building or campus as a whole, rather than patching together disparate systems, or tacking on testing functionality as an afterthought.

Such holistic emergency lighting system design is empowered by four key technologies: advanced luminaire communications, centralised system monitoring tools, total campus distributed control architectures, and the increased use of campus-wide Ethernet backbones.
Innovative luminaire, ballast and inverter control and monitoring protocols - such as DALI and DALI's extended command-set, (which is currently under industry discussion) - provide the system ‘eyes and ears'. Complementing this, user-friendly PC-based graphical control and monitoring interfaces provide a centralised ‘total view' of the entire lighting installation, both operational and emergency. Powerful lighting system distributed control architectures empower the holistic design, by providing ubiquitous connectivity across the entire building or campus. Increasingly, such distributed control architectures are complemented by a building- or campus-wide Ethernet backbone, allowing system-to-system bridging, plus connectivity to services outside the building, such as Internet monitoring and e-mailing of event alarm notifications.

These four core technologies, coupled with advanced lighting system design, are underpinning an essential holistic view of the building emergency lighting network. Together, they are empowering a new generation of emergency lighting testing - one that is seeing automated and semi-automated testing actually engineered into the system itself.

Jim Wallace of Seaward Electronic urges employers to take a common sense approach to ensuring the safety of electrical equipment, as any cutbacks on safety procedures carry considerable risks

With HSE reporting around 1,000 workplace electrical accidents and 25 deaths each year, reducing the dangers associated with the use of unsafe electrical appliances in the workplace is of vital importance. Fires started by poor electrical installations and faulty appliances also cause many more deaths and injuries - and considerable disruption to business activities.

Nevertheless, in pursuit of maintaining cost efficiencies during difficult economic times, health and safety procedures are often among the first activities to be reviewed for cost cutting purposes.

However, before taking any action in this respect, company owners should fully understand their obligations and the risks associated with any short circuiting of proper health and safety procedures.

Employers have a duty of care obligation under the Health and Safety At Work Act 1974 to ensure the electrical safety of all those using their premises.
As well as facing penalties from the HSE, those that ignore their responsibilities not only put their employees and customers at risk, but may also invalidate their commercial insurance policies and liability protection.

In addition, the introduction earlier this year of the Corporate Manslaughter and Homicide Act also makes it easier to convict organisations guilty of negligence - with fines of more than 10% of turnover with no upper limit one of the penalties in waiting.
For any organisations contemplating a less rigorous approach to health safety in the interests of cutting costs, the stakes have never been higher.

The legal requirements relating to the use and maintenance of electrical equipment in the workplace are contained in the Electricity at Work Regulations 1989 (EAWR).  Regulation 4(2) of the EAWR requires that all electrical systems are maintained so as to prevent danger.
This requirement covers all items of electrical equipment including fixed, portable and transportable equipment. Crucially Regulation 29 adds that a suitable defence is proof that all reasonable steps and due diligence were exercised in avoiding unsafe regulations.
In response to this situation, the IEE's Code of Practice for In-Service Inspection and Testing recommends that maintenance of electrical equipment is carried out in four stages - visual inspection, a test to verify earth continuity, a test to verify insulation and a functional test.
Electrical portable appliances are often roughly handled when moved from place to place, operate in a variety of environments and in many instances have more arduous and onerous usage compared to fixed equipment. As a result, at any time around 20% of electrical appliances used in workplaces could require re-testing to ensure that they do not pose a hazard to users.

Workplace safety programmes must therefore be capable of detecting potential problems with electrical appliances before they occur. For example, how can gradual deterioration in the electrical integrity of power tool, kitchen appliance or piece of IT equipment be diagnosed?

he emphasis on maintaining a safe working environment is therefore constant and some examples of the sort of horror stories uncovered by periodic inspection and test programmes illustrate this point perfectly.

For example, one public sector employer now insists all faulty equipment must have the whole lead cut off as close to the appliance as possible.  This is the result of an earlier situation when a caretaker rewired a plug onto an appliance that had previously had the plug removed after failing its regular test.  The failed but reconnected appliance was then responsible for causing a fire causing thousands of pounds worth of damage.

In an engineering company, factory workers risked their lives by continually replacing a fuse that persistently failed in a power tool with a solid metal bar, rather than raise the issue and question why the fuse was always blowing. The temporary modification was uncovered during a periodic portable appliance test.

Warehouse equipment when left around floor areas can be particularly liable to cable damage from fork lift trucks.  In one case a warehouse operative preferred to continue to use an electric drill with exposed wires rather than admit that it had been left out and damaged.

Even in offices, employees have been found to be taping up cracked power packs with cellotape rather than having them replaced. Elsewhere, in a school laboratory, a safety engineer had to take all the soldering out of service after the students had used them to burn through their own plugs.

All of these highly dangerous situations would not have been detected without the presence of regular inspection and testing procedures. Although many obvious defects can be identified by visual checks, inspection needs to be linked with a programme of testing to reveal potentially invisible electrical faults such as earth continuity, insulation integrity, correct polarity, unacceptable earth leakage and other potential problems.

Of course the need for establishing effective safety measures has to be balanced against practical aspects; realistic precautions for one organisation might be unacceptable for a larger or different type of business. In this respect guidelines on periodic safety testing intervals are provided in the IEE Code of Practice and supported by various HSE guidelines.
Given this situation, companies engaged in cost efficiency introductions need to think very clearly about the potential consequences.

In considering any cost reductions a clear distinction needs to be made between, for example, what might be regarded as potentially unnecessary and costly advice against those potentially vital life (or business) saving procedures.

This particularly applies to in-service electrical safety testing and ever more at a time when companies may be tempted to delay the replacement of older or damaged equipment with new tools and appliances, which so often happens during difficult economic conditions.
Where electrical safety is concerned, there is absolutely no room whatsoever for taking risks or adopting dangerous cost cutting practices.

The growing demand for clean, reliable power contrasts sharply with pressing concerns over energy supply, quality and price, and environmental issues. Peter Bentley, sales director of Uninterruptible Power Supplies (UPSL), makes the case for a new generation of modular UPS systems which are helping to address these issues

With dwindling North Sea oil and gas reserves and nuclear and coal-fired power stations nearing the end of their service lifetime, there is considerable uncertainty about the UK's future energy supplies. Combined with current price rises and pressure to meet environmental objectives, energy efficiency is undoubtedly of increasing importance to businesses. The consequent drive for new technologies that reduce power consumption and carbon emissions has been key to the development and uptake of modern, modular uninterruptible power supply (UPS) solutions that offer significant improvements in efficiency - not just in terms of energy but also physical footprint.

The proliferation of microprocessor-based equipment in industrial and commercial sectors has dramatically increased the numbers and types of electrical load falling into the ‘critical' category. The importance of protecting such sensitive and commercially vital IT and electronic systems against mains failures is now well understood, and as a consequence, continued growth in the UPS market has meant electrical contractors are now increasingly responsible for specifying and installing systems.

Reducing footprints
Energy and environment considerations are coupled with the high costs of real estate, particularly in city centre locations, and this has emerged as a major incentive for businesses to seek space savings for their IT systems and ancillary equipment.

IT energy consumption has increased by 400% per server rack since 2003, having grown almost exponentially. Demand for power can lead to the plant actually being larger than the data centre it is supporting, so it goes without saying that any contribution to space saving is to be welcomed.

For example, a floor space reduction of 70% could be achieved by replacing a 10 year old 400kVA parallel redundant UPS system (running at 45% of its rated capacity) with a new decentralised parallel architecture (DPA) 200kVA parallel redundant UPS system.
Such savings make an important financial contribution given the high cost of commercial property. For example, the biannual property market report (January 2008) from The Valuation Office Agency, shows that city centre office block rental values can reach over £300/m2 per annum.

The design and layout of commercial property frequently imposes physical constraints on the installation of IT systems and supporting infrastructure, particularly in old or converted buildings. Financial institutions for example have historically often occupied city-centre sites with considerable space challenges. On many occasions, installing modular rack-mounted transformerless UPS systems has proven to be the only viable solution for such exacting performance and floor space specifications, since they provide high power density and the smallest physical footprint on the market. Compared with legacy systems, such modular UPS systems typically take up only a quarter of the floor space.

Trying to cater for future needs with traditional stand-alone UPS systems can also lead to over-specification, creating a wasteful gap between installed capacity and the size of the actual critical load, and making inefficient use of costly floor space. However, today's modular, rack-mounted systems can be right-sized by inserting or removing ‘hot-swappable' modules, enabling power to be added as requirements grow without any footprint penalty.
This scalability helps specifiers and installation contractors to make flexible plans for space requirements and to manage this valuable resource in terms of immediate and future needs. Modular, transformerless UPS systems, with decentralised parallel architecture, provide a flexible, space-efficient and moveable system, versus monolithic stand-alone installations that may never be used to capacity and would certainly be a challenge to relocate.

Decentralised parallel architecture
Today's modular UPS systems are uniquely designed to remove any single point of failure, achieving virtually zero downtime and the elimination of costly disruptions to mission critical operations.

Decentralised parallel architecture works by paralleling independent rack-format UPS modules. This means that each individual module contains all the necessary hardware and software required for full system operation. With all critical components duplicated and distributed between the independent modules, potential single points of failure are eradicated, giving guaranteed system uptime.

With a minimum of one module over and above that required by the ‘capacity' system, the load is supported with UPS power if any one module shuts down, thereby providing full N+1 redundancy and significantly increasing system availability - an important factor at a time when power supply in the UK is becoming less dependable but more critical to business operations.

According to a recent report by business research and consulting firm Frost & Sullivan, rising energy costs, declining power quality and concerns over carbon emissions have highlighted the vital role of energy-efficient UPS. Commenting on the report, Frost & Sullivan programme manager Malavika Tohani commented: "Spiralling energy costs and increasing attention to reducing carbon emissions are driving the growth of energy-efficient UPS systems. It is therefore vital that applications consuming high amounts of power such as data centres and industrial applications adopt energy-efficient UPS."

Cost savings
Concerns over relatively high initial prices have in the past inhibited the uptake of energy-efficient modular UPS systems. However, as energy costs continue rising, total cost of ownership (TCO) increasingly favours a high efficiency solution as savings quickly compensate for the initial purchase premium.

By comparing the TCO for a traditional UPS and for an advanced modular system the savings become very apparent. The TCO advantage of modular UPSs derives from factors including size, transport and installation logistics, power security, maintenance, training, spare parts and upgrading, as well as energy costs and carbon emissions.

Modularity improves efficiency by working closer to the load capacity than traditional UPS systems but without sacrificing the security of the system. The more a load approaches the capacity of any UPS, the more efficiently the UPS operates. A traditional standalone parallel redundant system is typically just 50% loaded while a modular solution typically achieves a 70% or higher loading. This reduces both energy and UPS cooling costs.

As the table shows, for a modular 200kVA N+1 UPS system supplying a load of 180kVA, the TCO savings over five years can be nearly £145,900, with nearly 712 tonnes carbon emissions reduction and a carbon neutral offset equivalent to 1083 trees.

The financial benefits, efficiency and flexibility offered by modular UPSs means they are increasingly the de facto choice for ‘future-proof' power protection and to meet today's power supply and environmental challenges.

Within a building, the price of capital equipment does not stop at the point of purchase. In fact, with electrical equipment, the lifetime running costs can dwarf the original purchase price. Identifying and understanding operating costs and implementing strategies to alleviate them can save huge sums of money argues Kevin Jones of Schneider Electric's Services & Projects

Electrical distribution, building automation and control equipment represents a major investment within any building, but the full costs of such equipment are often always apparent. While there are often intense negotiations over the original purchase price, the costs of operating the equipment, its maintenance and its consumption costs are largely overlooked, despite the fact that the operating costs of equipment can be ten times that of the initial capital cost. By deploying effective lifecycle support strategies, the operating expenditure can be minimised. The key is for building services engineers to become more focused on delivering key actions required to optimise equipment assets.

In the built environment there is the scope to apply optimisation policy to both existing and new installations. For existing equipment there are the potential benefits in improving the performance or extending the life expectancy of the equipment. For new buildings or those with new installations of equipment, there is the possibility to design in optimisation and best practice for maintenance. Consulting an organisation, such as Schneider Electric's Services and Projects, that has extensive knowledge of equipment duty cycles and service requirements, it is possible to maximise lifetimes as well as equipment service uptime at the lowest cost.

Ensuring the electrical system is designed correctly at the outset, for example, provides long-term cost benefits by reducing spurious tripping and network faults that impact on the availability of the system. This can be taken further by fully protecting the system against the loss of power. In the case of an installation where power is distributed via substations, failure can render a building with no power, while for distribution network operators (DNOs), a failure in the supply equates to lost sales of electricity. It also leads to unhappy tenants or occupiers and again, in the case of the DNOs, there are potential repercussions from government regulators. In privately run systems such as large commercial or manufacturing facilities, the loss of power can also lead to stoppages in output that creates immediate lost opportunity penalties. The cost of downtime is something every business would like to cut out of its P&L reports. In some instances, such as public buildings, schools/colleges, hospitals, ports and airports lives can be put at risk if power fails.

Choosing the right equipment to install within a system is just as important as making sure the system itself is robust. Clearly, a key factor influencing the operating costs of equipment is the reliability of the equipment itself!  Selecting equipment with a proven track record of reliability, checking that the equipment is compatible with other elements in the system and installing the equipment correctly will all help to reduce the running costs. Also, making sure the system is scalable means that the business can flex to meet changing demand levels, without having to replace existing systems with new ones - another potentially significant lifetime cost reduction

Maintenance is key
Maintenance is frequently perceived as a non-essential cost, endorsed with the mantra ‘if it ain't broke, don't fix it'. Factors that affect its low prioritisation include operators being unsure of what to do to maintain equipment (particularly electrical items), the inability to measure, monitor and predict when and what maintenance is required, as well as a general deskilling in the industry that has left resources stretched and knowledge limited. However, to ensure the smooth running of the system, developing and deploying maintenance strategy is absolutely vital. By routinely checking the health and predicted lifetimes of equipment, the risk of unplanned downtime, or worse still, unpredicted outages, can be minimised.

As one example of how the problem can be addressed, Schneider Electric developed software called Prodiag, which can provide a fast and concise health check on electrical switchgear. The diagnosis takes less than one hour per electrical panel and uses the manufacturer's specifically designed measurement software. The critical device characteristics are recorded and compared with defined tolerance bands for assessment of the device status. Overcoming the problem of a measurement method is the most crucial step to gathering useful and effective predictive maintenance and lifetime data.
Where the resources or capabilities of in-house staff are stretched, developing a long-term relationship with a third party supplier for lifecycle support services can pay dividends. By partnering with one company, users benefit from the partner's increased knowledge of the user's business. At the same time, a shared ownership of the maintenance and upgrade strategy can be developed. In this way a history can be built up in the partnership to improve the performance of the equipment.

For example, maintenance can be reduced through fitting better electrical protection equipment. Here, the performance, accuracy and longevity of a system and its installed switchgear can be improved by replacing old electromechanical or solid state protection measures with integrated microprocessor based digital relays. Such state of the art equipment can also provide metering with remote alarm, monitoring and diagnosis functions.
A further extension of the outsourced maintenance concept is that of having an embedded engineer. In such a regime, qualified engineers that are fully conversant with the user's system can be based on site for immediate response and technical support in the event of equipment or system failure.  Since the deployment of an embedded engineer can be regarded as a part of the cost of sale rather than as an overhead, there are positive tax ramifications for the user as well as the benefit of having expert know how on call at any time.

Invest on a timely basis
To ensure assets are fully optimised, an equipment installation should be an evolving thing - not a once only fit and forget system. Reviewing the system and the equipment in it, highlights where changes and upgrades are needed to maintain optimum performance.
Upgrades are cost-effective, since upgrading a network or building is a much cheaper option than starting from scratch, plus it allows the user to manage its cashflow by investing smaller amounts on a regular basis. Manufacturers continually invest in new product development and by regularly upgrading products and systems, users can immediately reap the benefits of technology improvements. This brings commercial and cost advantages over having to wait for a complete new system - giving the user increased productivity from its installed plant.

By defining and implementing an asset optimisation strategy, organisations can improve process and plant availability, increase operations and maintenance productivity and forecast expenditure more accurately.

Last month Ernest Magog from Lumicom shed light on who is responsible for what under the WEEE Regulations. This month, Peter Lees, commercial manager at specialist WEEE compliance scheme Recolight, explains why recycling doesn't necessarily have to be an expense or a chore

It's been over a year since the WEEE Regulations came into effect in the UK, and now that they are starting to ‘bed in' we are seeing many encouraging statistics about awareness levels amongst businesses and overall increasing levels of recycling .  The latest figures show that the average WEEE recycling rate in the UK is over 7kg per inhabitant each year which is well above the EU directive's target of 4kg.

However, nearly two million tonnes of WEEE is produced every year in the UK and, according to a recent survey by environmental guidance providers Netregs, only 12% of SMEs could name the regulations provided in the WEEE legislation and many were unsure of their responsibilities.

At Recolight, we run a not-for-profit compliance scheme specifically for the benefit of our lamp industry producer members, their customers and end users. This means that on behalf of these members (we represent over sixty producer members) we have a remit to organise the collection and recycling of their lamps when they reach end of life. We do this via our RecoNet network of collection points and also through one-off on-demand collections where volumes are sufficient.

Our priority is to recycle as many lamps as possible on behalf of our members, and to increase overall recycling rates for waste lamps. Providing simple solutions and valuable support to end users is, in my opinion, the best way to achieve this. 

Unfortunately we are still finding that many small businesses and end users are paying the full cost of recycling services for WEEE and are unaware that they could qualify for pre-funded services like Recolight's scheme for lamps.

As a WEEE compliance scheme we take on the legal responsibility of our members to put in place a system to collect and recycle their customers' end of life lamps. Their membership funds the cost of our collection and recycling services from which any qualifying organisation can benefit.

An overview of the WEEE regulations 12 months on
The gas discharge lamps (GDLs) covered by the Regulations account for 70-80% of the 100+ million lamps sold in the UK each year. Gas discharge lamps (GDLs) include compact fluorescent lamps (CFLs), mercury, metal halide and sodium SON and SOX lamps. Most of these lamp types are used in both household and non-household applications and are also covered by the Hazardous Waste Regulations. They therefore need to be dealt with in accordance with strict guidelines as they could cause a risk to the environment if sent to landfill sites or otherwise not disposed of properly.

According to the Department for Business Enterprise and Regulatory Reform (BERR), over 4,000 producers have now joined one of the forty EA approved producer compliance schemes (PCS) in a variety of product categories, which they are obliged to do under the WEEE Regulations . The Environment Agency is responsible for enforcing the Regulations and is currently undertaking a programme of identifying ‘free-riders' who haven't yet joined a scheme.

Free riders are producers or importers who are not registered with a compliance scheme. Their customers, and ultimately the end users, are not covered for the cost of recycling these lamps when they become waste. In a worst case scenario other producers and their compliance schemes will end up incurring these recycling costs although no funding will have been provided. Non-compliance also means that there isn't an accurate national record of eligible EEE put on the market place, which is necessary for measuring achievement against targets, not to mention such practises leading to higher than necessary recycling costs.
One of our key messages to wholesalers, retailers and facilities managers is to make sure they buy lamps from a compliant producer. In particular it is sensible to ask your supplier to specify the compliance scheme to which the brand you are buying belongs. This way you can be sure that you won't be left trying to find a recycling scheme for your customers, and even better can avoid having to pay unnecessary charges to recycle the ‘free-rider' lamps when they reach end of life.

Working with Recolight's compliance scheme
All compliance schemes operate differently but we emphasise in our business model that recycling should be easy, cost effective and second nature. As a specialist scheme for lamps we provide (subject to conditions) free collection, via our RecoNet network of collection points, and can also make one-off on-demand collections where volumes of lamps are sufficient. We always welcome enquiries from businesses interested in becoming collection points and have recently seen an increase both in the number of one-off collections we are making and in the total number of fixed location RecoNet collection points we have. As awareness levels about both the need to recycle lamps and the services we offer grow we expect levels of recycling to increase further.

The wiring-harness architecture found in trucks, buses and other vehicles with electrical systems based on 24V technology has undergone considerable change as electrical and electronic content has increased. Conventional functions, such as the HVAC (heating, ventilating and air conditioning) system, continue to be converted to electronic control while many new features, such as GPS (global positioning systems) and entertainment systems, are being added to the electrical load. in the second of a two-part feature, Guillemette Paour of Tyco Electronics' Raychem circuit protection products explains

32V PPTC Devices Help Improve Design Flexibility
Truck and bus wiring harnesses must be protected from potential damage caused by a severe thermal event, such as a short circuit in the vehicle wiring. Circuits typically require 0.10 to 20A of current at system voltages of 28V with operation to 32V.
Until recently, a caveat in a vehicle's harness design was that 24V modules with resettable circuit protection devices could not be located under the hood in high-temperature environments. The introduction of Tyco Electronics' PolySwitch AHEF series of 32V devices rated from -40°C to 125°C eliminates this design drawback. The new PPTC devices are available in current ratings from 0.5A to 10A, allowing the harness' electrical architecture to be designed more closely to reflect the optimized tree structure with its accompanying size, weight, and cost benefits.

The benefits of these new circuit protection devices include a maximum 32V operating voltage rating and a maximum operating temperature of 125°C that allows them to be used both in the passenger and the engine compartments. Additionally, all devices are housed in through-hole packages and are tested to the AECQ200 standard. They are RoHS and ELV compliant.

Technology Benefits
As single-use devices, fuses must be replaced when they blow. This requires that fuses be mounted in accessible fuse boxes - a requirement that dictates system architecture and forces packaging and system layout compromises. Unlike fuses, PPTC devices do not require replacement after a fault event, and allow the circuit to return to normal operating condition after the power has been cycled and the overcurrent condition is removed.

PPTC devices are made from a composite of semi-crystalline polymer and conductive particles. At normal temperature, the conductive particles form low-resistance networks in the polymer (Fig. 4). However, if the temperature rises above the device's switching temperature (TSw) either from high current through the part or from an increase in the ambient temperature (or both), the crystallites in the polymer melt and become amorphous. The increase in volume during melting of the crystalline phase separates the conductive particles resulting in a large non-linear increase in the resistance of the device.
The resistance typically increases by three or more orders of magnitude. This increased resistance helps protect the equipment in the circuit by reducing the amount of current that can flow under the fault condition to a low, steady state level. The device remains in its latched (high resistance) position until the fault is cleared and power to the circuit is cycled - at which time the conductive composite cools and re-crystallizes, restoring the PPTC to a low resistance state in the circuit and the affected equipment to normal operating conditions.
Because PPTC devices transition to their high impedance state, based on the influence of temperature, they help provide protection for two fault conditions - overcurrent and overtemperature. Overcurrent protection is provided when the PPTC device is heated internally due to I2R power dissipated within the device. High current levels through the PPTC device heat it internally to its switching temperature causing it to trip and go into a high impedance state.

The PPTC device can also be caused to trip by thermally linking it to a component or equipment that needs to be protected against overtemperature conditions. If the equipment temperature reaches the PPTC device's switching temperature, the PPTC device will transition to its high impedance state, regardless of the current flowing through it. In this way, the device can be used either to reduce the current to the equipment to very low levels, or as an indicator to the control system that the equipment is overheating. The control system can then determine what action is appropriate to protect equipment and personnel.

PPTC devices are employed as series elements in a circuit. Their small form factor helps conserve valuable board space and, in contrast to traditional fuses that require user-accessibility, their resettable functionality allows for placement in inaccessible locations. Because they are solid-state devices, they are also able to withstand mechanical shock and vibration.

Resettable circuit protection also offers the benefit of making overcurrent protection less susceptible to misuse and tampering. Automotive fuses that have nominal current ratings from 2A to 30A are all packaged in the same form factor. A fuse can be incorrectly replaced by one of a higher value, offering no protection at all. When located in remote modules, PPTC devices cannot be readily accessed, changed or abused by the user.

Conclusion
The introduction of 32V PPTC devices enables reliable, resettable overcurrent protection for bus and truck wire harnesses utilising 24V electrical systems. Featuring operating temperatures from -40°C to 125°C and current ratings from 0.5A to 10A, the PolySwitch AHEF series devices offer designers the ability to locate protection close to their intended electronics - whether in the passenger compartment to help protect BCUs (body control units) or in the engine compartment to help protect HVAC or other control modules. Resettable circuit protection strategies can also help facilitate designs that use less copper, reduce weight, voltage drop and heat, and optimise PCB (printed circuit board) space.

The Department for Business, Enterprise and Regulatory Reform (BERR) is due to unveil its impact assessment report on smart metering next month. Decision makers across the utilities industry are on the edge of their seats, as the Government is expected to decide on a UK-wide smart meter roll-out based on BERR's December report. However, it has recently been suggested there isn't enough data for the Government to make its decision on time. David Hughes, utilities practice director, ABeam Consulting, discusses why the industry should move ahead with smart metering regardless of a public mandate

As UK plc prepares for an energy efficient future, the utilities industry is under the microscope. While using green energy sources is important in the long-term, empowering customers to be more energy efficient is part of the solution in the short-term. It is clear smart metering technologies will play a crucial role in this, enabling customers to better understand and regulate their own energy consumption.  Providing customers with real-time visibility of the energy they use enables them to see how they can save money, which is the ultimate incentive to change their behaviour. 

At first glance, the introduction of smart metering within the UK energy market could be viewed as extremely problematic. The installation of 26 million new smart electricity meters across the country will be costly, time-consuming, and complicated from a logistical perspective. There is also the immediate and very real impact on revenue: customers using less energy and ultimately paying less - which will hit the bottom line. An increasingly competitive market also creates issues around capital investment, ongoing asset ownership and supplier switching.

Then there are the customers, who are becoming increasingly intolerant of poor service. This is driving the need to focus efforts on external change, managing customer expectations and communication, to avoid additional costs associated with unplanned customer contact and complaints.

Yet, there are massive benefits that can be achieved with smart metering. Aside from the environmental advantages, it enables on-demand meter readings whilst eliminating manual meter reading costs. Smart meters eliminate the human error in meter reading and predicted costs based on previous history.  Removing such errors also eliminates any room for disagreement about billing, saving the customer time.  The cost to serve the customer will be reduced further, as customers tend to respond well to more accurate and frequent billing.  In fact, when tackled in the right way, smart metering can be seen as a huge business opportunity, which suppliers should take advantage of regardless of the Government's pending decision. ‘Smart' suppliers should look beyond the basic logistics and economics of implementation and begin to exploit smart metering as the catalyst for really getting to grips with their customer relationships.

Smart metering can provide a unique source of real-time customer information, which can be used across a retail energy providing organisation to drive efficiency and guide each individual customer journey. It also marks a shift in the evolution of customer management, from a reactive relationship that is geared towards problem solving, to a proactive relationship aimed at continually realigning and improving the customer experience. In the future, customers can expect to have personalised conversations centred on their individual tariff, product and service needs. 

The real-time consumption data provided through smart metering can also go a long way to address ‘green disadvantages', such as reduced revenue. It is important that tariff development taps into this detailed consumption information. This enables the delivery of a range of flexible tariffs that suit the needs of the customer, whilst supporting the revenue needs of the business. If applied intelligently, tariffs that help to control consumer demand can be developed, without a hugely detrimental impact on energy sales. Additionally, when combined with effective back office processes aimed at identifying the customer, real-time consumption information can be used to confront energy theft and minimise unbilled periods.

The advanced metering technology itself offers network maintenance benefits that often exceed expectations. For example, it enables auto and remote diagnostics, which support field force optimisation. This enables meter faults to be identified centrally, tapping into the work management system to send the right operative to complete the job. Additionally, smart metering enables some meter problems to be fixed remotely, eliminating the need for a visit completely.

In parts of the US and Europe, smart metering is delivering considerable benefits already. In Italy for example, the introduction of these technologies has resulted in customers making fewer unnecessary bill enquiries and paying their bills more diligently. To reap the benefits of smart metering for business and customers alike it is crucial that suppliers treat it as a fundamental catalyst to business-wide change.  Merely tinkering with smart metering will lead to creating inefficiencies in processes, systems and working practices.  Smart metering should be seen as a driver for standardisation and simplification - both internally and for the customer. Moreover, it should be regarded as a business transformation programme with the customer at the heart of future operating models, not just an IT project.

The question of if and how the Government eventually decides to move ahead with a smart meter roll-out should therefore be almost irrelevant for suppliers. The industry should start pushing for smart metering adoption before it becomes a legal necessity, because those that won't wait for Government enforcement will ultimately have the competitive edge. Suppliers need to remember that they dealing with increasingly demanding, price-sensitive customers in an extremely competitive market, and plan accordingly. To make the most of smart metering, suppliers need to be smart about it.

Anyone involved in specifying or installing lighting needs to be aware of who is responsible for what under the WEEE regulations, says Lumicom chief executive Ernest Magog

While the WEEE (Waste Electronic and Electrical Equipment) regulations have introduced a valuable ‘imperative to recycle' that will make a positive contribution to sustainability, they have also created some confusion. In particular, many of the people involved in the procurement and disposal of WEEE such as lighting are often unclear about their own responsibilities.

This is an area where specifiers and installers need to have clarity with regard to their own involvement and can also guide the end user to the most straightforward solutions.
My organisation - Lumicom - is a not-for-profit organisation that has been created to manage the recycling of luminaires under the WEEE Directive. It works closely with Recolight, which is responsible for light sources such as discharge lamps. And while our experience is with lighting products many of the general principles apply to all types of WEEE and serve to help clarify the situation.

As far as the WEEE Directive is concerned there are two categories of waste - historic waste, installed before 13th August 2005, and future waste, installed after that date. Future waste is marked with a crossed out wheelie bin to indicate that it cannot be consigned to the general landfill waste stream.

With historic waste, the producer of any replacement equipment is responsible for facilitating an infrastructure that will accept historic waste. In the case of future waste, it is the producer of the discarded waste that bears this responsibility. This effectively means that lighting manufacturers are responsible for the disposal of the majority of discarded light fittings from refurbishment and refit projects.

Similarly, suppliers of lighting equipment for current new-build projects will be responsible for disposing of those products when they are removed in the future. In most cases this will be through an accredited scheme such as Lumicom. However, if there are no replacements, such as in a demolition project, then the responsibility for disposal falls to the end user if the products were installed before 13th August 2005.

As with other forms of waste disposal, the building operator has a responsibility to ensure that this is carried out by whichever contractors or sub-contractors are involved. This means that while specifiers and installers do not have any direct responsibility for the disposal of light fittings, other than ensuring that waste is sorted properly on site (see below), there is an implied responsibility to the client.

Many would argue that it's reasonable for the client to expect and receive specialist advice on such matters from the experts employed to do the work. There is certainly a benefit to adding value to the service in this way and could be beneficial in terms of future work from that client.

For example, the high proportion of lighting projects will use light fittings from a number of different manufacturers to meet the needs of all the spaces. However, at the end of life of those fittings, which manufacturer will be responsible for disposal? Or will the building operator have to deal with a dozen or so different suppliers to dispose of used fittings. This is one of the reasons for the formation of schemes such as Lumicom as it brings manufacturers together under a single umbrella. So as long as all of the fittings are sourced from members of the same scheme there is still just one disposal body to deal with. Nor should this mean the designer's flexibility is hampered, as any such scheme ought to incorporate a significant number of the key players. Thus far, Lumicom is the only such scheme to have the necessary infrastructure in place.

In all cases, the contractor would be well advised to draw the client's attention to the need to have the discarded equipment transported to bulking up points established by recycling schemes as the cost for doing this will be additional to the stripping out work. If the client or specifier is unwilling to source all luminaires from members of a single scheme, contractors should also protect themselves by amending terms and conditions of trade. In particular, they need to exclude themselves from any WEEE responsibility for either the old luminaires coming out or the new ones going in. Such actions by contractors could have an impact on the design and specification of the lighting scheme, so specifiers also need to be aware of the implications of this.

Sorting on site
Another issue to be aware of is that the key components that make up a light fitting need to be recycled through different waste streams, so these have to be separated before being sent for recycling. Some waste disposal contractors will collect the entire fitting and separate the components themselves, while others will require the separation to be carried out before collection. In the latter case, this has implications for the waste management on site and the project managers responsible for this.

The three most important components that need to be handled separately are lamps, batteries in self-contained emergency luminaires and liquid filled power factor correction capacitors. Ensuring this separation is carried out is very important.

For example, discharge lamps - such as fluorescent, metal halide and sodium sources - are classified as hazardous waste because of the small amounts of mercury they contain. Consequently, not only do they need to be separated, they also have to be stored carefully on site in compliance with the CoSHH (Control of Substances Hazardous to Health) regulations.

Another reason for separation is that the majority of discarded luminaires are shredded into small pieces of metal and plastic and sold as raw material - much of which ends up in the Far East and goes back into manufacturing. If the hazardous components were not separated first the entire batch could be contaminated. This would significantly increase the cost of disposal and could lead to legal action under hazardous waste regulations.

This highlights a further benefit of compliance schemes, namely that they will ensure all waste disposal in compliance with legislation, backed by a full audit trail. Yet another reason for ensuring that lighting suppliers for the project have a WEEE registration number and are members of a suitable compliance scheme.

As the WEEE regulations ‘bed down' and people are coming to accept waste disposal considerations as an integral part of any project, it is also becoming second nature to address these issues as part of the design and installation process. Equally, taking advantage of the schemes that have been put in place to make disposal safe and straightforward is also becoming the obvious and most sensible way forward.

The wide range of cables on the market today reflects the multiplicity of cabling applications available to the electrical engineer. As such, there is a great degree of variation in the production process making cables highly customisable and suitable for many different applications depending on their unique requirements. Owen Dale of FS Cables explains

Generic cable elements such as conductors and insulation can differ greatly according to the application, dramatically altering the properties and performance of the cable itself. This means using different manufacturing processes according to the materials and components specified. Production techniques vary too, for example in the way the conductors are insulated and how the core bundle is created in the laying up process. This article takes a look at the manufacturing processes involved in producing a cable, from the initial drawing of the conductors, insulation materials used and the ‘laying-up' of cores.

Conductors
Conductors are single or multiple strands of highly conductive metal, usually copper. Other materials commonly used include aluminium and nickel. Their purpose is to carry an electric current for data or power between two points.

Copper
Using the example of copper, the raw ore once extracted from the earth is smelted into ingots which then undergo electrolysis to remove impurities. This involves attaching a negative charge to the ingot and submersing it in a tank of copper solution.

This has the twin effect of dissolving the copper and at the same time attracting it to reform on the positive element.  The impurities drop to the bottom as they won't take the charge. While not all impurities are removed, this procedure can produce 99.99% pure copper. The purity of the copper has a huge effect on reducing resistance on the electrical charge passing along the conductor, greatly increasing its ability to carry a current. This is just as important for a signal as it is for a power or energy cable.

The pure copper is rolled out into rods and then drawn through a series of dies made from a very hard material such as ceramic or even diamond to make very thin strands. It is common to draw copper strands as small as 0.05mm diameter (a human hair is normally between 0.07mm to 0.1mm in diameter). These strands can either be used singly or in bunches to make a larger, more flexible conductor.

Depending on the application of the cable, the strands can be coated with an inert metal at this stage to reduce corrosion or enhance heat resistance. Tinning, the process of coating the conductors with a layer of tin either electronically or in molten form is very common for this process as it is low cost and relatively resistant to corrosion. Nickel plating is used where the cables will be working at temperatures between 200° - 400°C.

Stranding
Conductors are normally measured either by their diameter or cross-sectional area in mm². The method for measuring cross sectional area (CSA) is standard across Europe and is in accordance with BS6360 and IEC60028.

It is important to note the standards also specify the resistance of a conductor for a given stranding. This means that a conductor can be made up of fewer strands or smaller diameter strands but still conforms to the standard.

Another method is the American Wire Gauge size (AWG). This denotes the gauge size as a number i.e 24AWG followed by a number in brackets i.e (7) which shows the number of strands. It's worth mentioning, the higher the number the smaller the conductor, so a 24AWG conductor is smaller than a 20AWG. Full stranding charts and AWG / Metric conversion tables can be found on in our cabling guide - The Little Red Book.

Using the metric cross sectional area method, Class 5 stranding is the most common flexible grade, as it combines good flexibility with a reasonable cost. Generally, the more strands you have the more flexible the cable, but it also becomes more expensive. Classes 1 (solid) and 2 are widely used in fixed installations where the cable won't be moved or bent after it has been fitted.

Cores are normally made up from multiple strands by twisting or bunching the strands together. In larger or very finely stranded conductors the strands may be first twisted into groups and then twisted together to form a conductor similar in appearance to a rope. Conductors become ‘cores' when coated with an insulating material.

Insulation Materials
Insulation is a non-conductive material used to coat the conductor to keep the electricity flowing to its intended destination. In the case of a transformer or motor armature this may be a simple enamel varnish but in most cables and wires thermoplastic or elastomeric compounds are normally used.

With the exception of overhead power lines, conductors are normally insulated within a cable to ensure the electricity, whether it is data, signal or power, only goes where it is intended and doesn't jump from conductor to conductor. Insulation types vary enormously in range and application. The popular types are outlined below.

Thermoplastic compounds
These include PVC, Polyethylene and many Low Smoke Halogen Free (LSHF) materials. Thermoplastic compounds are defined as materials that can be melted in an extruder and, when cooled, reform with the original properties unaltered. The compounds are supplied in bulk in granules about the size of a match head. The advantage of these compounds is that they are relatively easy to work with and the equipment needed in manufacturing is generally fairly simple. It is also quite easy to change colours within a material type. However the cost of the compound varies significantly with high performance LSHF compounds costing up to five times that of basic PVC.

Elastomeric or Curing compounds
This group includes rubbers and materials that are altered after extrusion by a catalyst, for example by cross-linking the molecules to improve the performance of the material. XLPE is commonly used for signal and power cables.

In the case of silicone rubber, the silicone is squeezed out of the extruder cold, like a putty and then enters the curing process - normally a steam tunnel or through salts at very high temperatures.

Taping
Taping is not as popular as it used to be, although some products are still insulated by winding a tape around the conductor. Paper taping is used for some power cables and PTFE is used for heat resistant and high performance wires. One advantage of taping is the conductor is central or concentric within the insulation. In the case of PTFE the insulated wire is then subjected to extreme heat for a very short time (sintering) to fuse the edges of the tape together and stop it unwinding. Mica tape is often used to ensure circuit integrity during a fire. Mica is a naturally occurring substance which is bonded to an inert substrate that is wrapped around the conductor prior to the insulation being applied.

Lapping or braiding
These are now mainly used for heat resistant cables working over 250°C. Glass or ceramic fibres are wound around the conductor, normally in two layers in opposite directions with a glass fibre braid overall to hold it all together. These cables are stable at high temperatures (up to 750°C) but are not suitable at normal ambient temperatures where there may be moisture. Most of the products are silicone varnished to ease handling during installation but the varnish burns off at a high temperature.

As you can see there are many different types of insulation each with a specific job. PVC and XLPE are the most common and offer great all round properties in terms of flexibility and cost. Other materials are crucial for high performance applications such as fire alarm cables where it is important a cable can carry on functioning even in the event of fire.

When choosing insulation it is important to establish what the cable or wire is expected to do. Temperature, voltage, electrical characteristics, flexibility, performance in the event of fire and other physical factors all need to be taken in to account when specifying. With literally hundreds of different grades of PVC, eighty-plus grades of silicon and practically every other compound being able to be split into subgroups, there are insulations to meet practically every need.

The Laying Up Process
The laying up process is used to create the core bundle once the conductors have been insulated.

In a simple cable two cores can be laid next to each other and have a jacket extruded over them. However, in many two core cables and all multicore cables it is normal practice to twist the cores together. This has a number of benefits. Firstly, it improves flexibility with each core taking the same amount of stress as the others. Additional benefits include easier production (by keeping the cores together as they pass through the jacketing extruder) and better cable uniformity.

Multicore and multipair cables
Multicore cables have a number of cores twisted together to form the core bundle. The ideal core bundle is circular and to achieve this, dummy or blind cores may be added. These cores contain no metallic elements and just act as fillers. In cables with 12 cores or more, the cores will be arranged in layers with each layer twisted in opposite directions. This ensures the finished cable has the best chance of remaining circular even if driven over or trodden on. Cores can also be arranged into pairs, triples or quads. This is common for data, signal and instrumentation applications. By twisting the cores to form pairs the problem of crosstalk is reduced. Crosstalk occurs where the signal on one circuit leaks over onto another circuit. Analogue signals in particular can be affected by this.

By creating a twisted pair, the cores are in limited contact with adjacent cores and are exposed to equal levels of electromagnetic interference (EMI). The process of twisting cores into pairs is relatively fast with speeds of up to a few hundred metres a minute. The pairs are then laid up in the same way as with multicore cables. On high performance data cables the twist rate may vary, for example in Cat 5 cable the twist rate of pairs varies between 18mm and 22mm. On telephone cables this may extend to one complete twist every 80mm or so which is hardly noticeable.

Termination can be easier and faster on twisted paired cables. Core identification is normally achieved by either colouring each core differently (colour coding) or printing a number on each core. On twisted pair cables colour coding is very popular. Number coding on tapes wrapped around each pair, or a combination of colour and number coding are also sometimes used.

Talcum
Having laid the cores or pairs into a bundle the next stage is to add a jacket. There is one vital element prior to extrusion and this is to create a barrier between the core bundle and the jacket. A barrier is particularly important because if the insulation and jacket are of similar compounds the jacket could stick to the insulation.

The most common barrier is talcum or French chalk which is held in a trough through which the core bundle is pulled before going into the extruder. Talcum has the advantage of being both cheap and effective.

The disadvantage of talcum is that it is difficult to detect if it has run out or fails to cover the core bundle properly. This can result in a cable that is very difficult to strip and has reduced flexibility. Also, in a small number of applications the talcum could contaminate the surrounding equipment, for example with medical equipment or in clean rooms.

Other release agents can be used, including silicone oils, but these are more expensive than talcum and can be difficult to apply. Other methods include tapes of polyester or mylar and the non-woven polyester or fleece types. The latter are ideal for constantly flexing cables as they allow movement. They are sometimes used between layers in core bundles or either side of braid screens. Popular in robotics and audio cables, they are increasingly used in more general cables where flexibility and ‘stripability' are important.

This article was originally printed in the FS Cables quarterly newsletter Wired, available either in print or electronically by calling 01727 840 841 or emailing This email address is being protected from spambots. You need JavaScript enabled to view it.. The next instalment of ‘What's in a Cable' will be published in the winter edition of Wired, printed in December.

Modern control systems are invariably designed with safety as a prime requirement. Often this can add significantly to the cost, particularly where high-power contactors have to be duplicated to provide redundant operation. Fortunately, there's now a better approach, as Moeller Electric's Steve Rickard explains

Almost every control panel incorporates motor starters and there can be no doubt about it, when a safety relay operates or an emergency stop button is pressed, the motors controlled by those starters have to stop.

It's easy enough, of course, to design the control circuits to behave in this way, but what happens if there is a component failure? In particular, what happens if a contactor has welded closed? The answer is that, unless further measures have been taken, the motor controlled by the welded contactor will continue to run.

Clearly, this very dangerous state of affairs cannot be tolerated, particularly as welding is a relative common failure mode for contactors, especially those that have reached the end of their service lives.

The usual solution is to incorporate two identical contactors in series in the starter circuit which meets the requirements of Safety Category 3 and 4. The risk of both contactors welding simultaneously is unlikely, so at least one of the contactors will always open when required to do so, and the motor will be safely stopped.

While this approach of using redundant contactors is effective and widely used, it does have several drawbacks. The first is cost. While small contactors are relatively inexpensive, their larger counterparts certainly are not. So, with a 100kW drive, for example, using a second redundant contactor adds significantly to the overall cost of the control system. The next drawback is panel space. High current contactors take up a lot of panel space, and not only is panel space expensive, there is often insufficient room available on site to allow large panels to be accommodated. Finally, duplicated contactors increases the amount of heat generated within the panel, because of the losses from the coil and main contact circuits.

To address these issues, Moeller Electric has pioneered the development and introduction of a new type of control component - the contactor monitoring relay, a device which is both compact and inexpensive.

The principle of operation of this innovative device is easy to state. It simply compares the state of the main contacts of a contactor with the voltage that's being applied to the coil. If the coil is de-energised but the main contacts are still closed, the output relay of the contactor monitoring device operates, opening a set of contacts that can, for example, be used to trip an undervoltage release on the circuit breaker protecting the motor circuit. In this way, it's clear that, even if the contactor welds, the motor will still be brought to a stop safely. The need to use a duplicate contactor to ensure safe operation is, therefore, eliminated.

While the principle of operation of the contactor monitoring device may be simple to state, however, designing a practical product is a little more challenging. For example, what is the best way to monitor the main contacts of the contactor?

The solution adopted by Moeller Electric is for the monitoring device to look at the state of an auxiliary contact on the contactor. Not all auxiliaries are guaranteed to accurately reflect the state of the main contacts, however, especially when the contactor is faulty. The auxiliary used for this function must, therefore, meet the requirements for a mirror contact, as defined in the IEC EN 60947 Annex F.

Essentially, these requirements state that a mirror contact on a contactor is a normally closed contact that can only ever close if all of the main contacts have opened. All N/C contacts on DILM and DILH contactors from Moeller Electric meet this requirement. That's not quite the end of the story, however, as we need to consider what happens if the auxiliary contact itself welds closed. This is very unlikely, but by no means impossible. The solution here is to compare the state of the N/C auxiliary with an N/O auxiliary in the same contact block. Provided that the contacts are positively driven - a condition once again met by the standard auxiliaries used with Moeller Electric contactors - they can never be closed at the same time unless a fault has occurred.

By monitoring a positively driven N/O auxiliary as well as the N/C mirror contact, the contactor monitoring relay can, therefore, immediately detect problems with the mirror contact and generate an output to trip the drive.

As this discussion shows, the characteristics of the contactor and of its auxiliary contacts have a critical bearing on the operation of the contact monitoring device. For this reason, Moeller Electric provides details of approved product combinations that will ensure the appropriate levels of safety are achieved.

With these combinations, the operation of the contactor, the contactor monitoring device and the motor protective circuit breaker complies with the requirements of EN ISO 13849 for Performance Level e, provided the number of switching operations of the contactor does not exceed 350,400 per year, and that the number of switching operations of the protective device does not exceed 1,095 per year.

In the calculation of the overall performance level for the control system, however, the safety components upstream of the motor starter also have to be taken into account. When this is done, the result is that, with the aid of the contactor monitoring device, control systems that overall meet the requirements for Performance Level d can be readily implemented.

Small, easy to use and cost effective, contactor monitoring devices are a very attractive and convenient alternative to the adoption of redundant contactor designs in control systems. They save money and space, as well as reducing the amount of heat generated within the panel, all without compromising the level of safety achieved by the overall system.

With contactor monitoring devices offering so many benefits, surely it has to be time to make redundant contactors redundant?