Power quality is an unfamiliar issue for many in UK industry, but it is likely to become very well known in the near future. Power quality covers a vast range of issues from voltage excursions, frequency variations, supply imbalance and harmonic distortion. Uncorrected power quality issues can bring a host of problems from unnecessary power losses which can disrupt production through to catastrophic equipment failure. Steve Barker, energy and power quality manager at Siemens Automation & Drives, outlines the extent of the power quality problem in the UK and offers some solutions for business...
British industry of all sizes tends to take its electricity supply for granted. A simple flick of a switch and a plant or production facility has access to the supply network which will give a business as much electricity as it requires at any time of the day, no questions asked. A whole range of equipment from machinery and computers through to lighting and electric motors rely on the mains supply network with little thought given thereafter, other than paying the bill.
However, the use of increasing levels of electronic equipment by business is causing a phenomenon called “harmonic distortion” on the UK electricity supply network. Harmonic distortion is caused by non-linear loads on the electricity supply system, such as personal computers, lighting systems, switch mode power supplies and variable speed drives.
Regulation ER G5/4-1, published by the energy networks association (ENA) is the UK’s instrument to control this distortion and to assist compliance by business with the harmonised network standards such as the European EN50160 (it is important to note however that the UK measures are more severe than in the rest of Europe).
ER G5/4-1 which was first published in 2001 and subsequently updated in November 2005, is the UK’s attempt to control harmonic distortion back onto the supply network and is the updated version of the earlier ER G5/3 which was originally published in 1976. Ironically, many of those businesses affected by power quality issues remain unaware of the original regulations let alone the updated version which are far more stringent.
The updated regulation is far more onerous than previous regulations and specifies voltage and current limitation to which all industrial sites in the UK must comply in a three stage approach which takes into account different sizes of installation. Stage 1 applies mainly to small commercial installations supplied from the public low voltage network. Most industrial sites are typically assessed under Stage 2. Industrial sites of large users may fall under Stage 3 which applies for incoming supplies taken at 33kV and above.
Excess harmonic distortion on a site can lead to two types of problem. Firstly, ER G5/4-1 compliance issues which can ultimately result in disconnection if remedial measures are not taken. More often than not, electricity users are not familiar with compliance issues and attempts by a company to achieve compliance with ER G5/4-1 can consume huge resources of time and money. I have personal experience of a number of installations where compliance issues have been tackled badly and the remedial measures have been more costly than early preventative considerations. One example involved a company foregoing a £50k investment in preventative measures that could have saved a small food and beverage company in the North of England around £1m – a figure which was later spent on mandatory remedial issues to correct the problem.
Secondly there are a number of practical issues for end users involving power frequency harmonic distortion that can cause often hidden problems which can include:
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