Power to the people

Such problems are relatively new. Desktop pcs, motors controlled by variable speed drives, and energy saving technology are all causing harmonic distortion of the power supply. This, in turn, can cause stress in conductors, capacitors, transformers and switchgear and lead to disruption and premature failure. Other power supply problems on the increase, such as transients, sags, surges and outages, can lead to the same devastating results: damage, disruption, downtime and loss of productivity.

While there are numerous power quality solutions on the market, there is a general lack of awareness of design and installation best practice which could minimise future problems at the initial design stage. A new pan-European project aims to do something about it.

The European Commission is to pump three million euros into an education programme on power quality via its Leonardo research fund. Led by the European Copper Institute, and including the UK's Copper Development Association, this three-year project will provide continuing professional development for electrical engineers in the building and construction sector.

It seems the initiative is much needed. "There are currently no undergraduate courses on offer to educate future electrical engineers in this very important field," explains Dr Milanovic, senior lecturer in electrical power engineering at UMIST. "This project will certainly help to raise the awareness of power quality problems that engineers are facing on a day-to-day basis and enable them to deal with them in the most efficient way."

The programme will produce a set of application notes and establish a web site including e-learning modules, a library and a discussion forum.

The Copper Development Association will be able to bring valuable experience from the UK. It founded the Power Quality Partnership with solutions providers MGE UPS Systems, Fluke, Rhopoint Systems and Claude Lyons. Each member company can offer support in its own field of expertise and will also provide contacts in other member companies where that is more appropriate. Solutions include site surveys, power quality measurement and analysis and products such as ups, voltage stabilisers, power conditioners, harmonic filters, pulse rectifiers and variable transformers.

While there are no regulations in place to tackle harmonics, the Electricity Association's G5 recommendation is the de facto standard for the industry. The recommendation was revised this year and published as G5/4. It sets levels for harmonic voltage distortion and advises on how best to connect variable speed drives to the network.

Contractors need to pay particular attention when designing and installing multiple loads over 16 A, when harmonic limits contained in international standard IEC 61 000: 3-4 kick in. Careful consideration must be paid to drive characteristics and the harmonics produced.

For example, G5/4 contains tougher limits for the all-important fifth harmonic. As this is the main emission from six-pulse rectifiers, the market is likely to see a shift to 12-pulse rectifiers.

Whatever is happening in the marketplace, continuing education is the key to avoiding problems in the first place. Let's hope that the findings from the new European programme are disseminated quickly.