Summer power problems were predicted


In an in-depth article focusing on the elements of risk to the operation of standby power systems, published in Building Services & Environmental Engineer in September 2004, Harath Engineering (now part of Chloride) made predictions that business continuity issues would result from the National Grid reducing resilience of electricity supplies in summer months. It warned Hi-Tec business operations of risks to mission critical operations and the increased need to ensure the absolute integrity of a back-up power supply to maximise power availability. On 27 July 2006 these predictions proved accurate. After a period when daytime temperatures were consistently significantly above 30°C, Central London had an extensive and extended power interruption and many businesses were shocked to find they had deficiencies in their power protection systems. The seriousness of this type of event is typified by the experience of a major datacentre which recently had a failure in back-up to its mission critical power system, leaving its customers’ websites out of action for 12 hours.

Whilst not going into the reasons why power should be considered as a commodity with a reducing reliability profile, the article highlighted an aspect of it that is very relevant. The National Grid considers that their period of greatest demand is in the winter, which is true given a holistic view. It is, however, not true for any Hi-Tec organisation where the heat generated by their equipment is a liability. In these cases the period of increased demand is in the summer when air conditioning is drawing its greatest load. National Grid openly states that it reduces the resilience of its network in summer in order to accommodate their maintenance. It follows, then, that specific parts of the network, such as the commercial centres of any city, are subject to less resilience at the very point when they are at their most vulnerable. The London power interruption in July appears to confirm this as it has already been attributed to a high usage of air conditioning in the hot weather.

Most organisations, that are dependent upon electricity for the operation of their businesses, have installed standby power equipment, such as generators and Uninterruptible Power Supplies (UPS), in order to ride out power cuts. Unfortunately, this gives many a false sense of security because this equipment, too, can be prone to failure unless it has been correctly specified, installed properly and maintained continuously.

Main standby power components, diesel generators and UPS generate substantial amounts of heat. As any installation draws in its cooling air at these elevated ambient temperatures, it is immediately heated further by the heat rejected from the equipment. This effect often forms a vicious circle, ultimately resulting in the standby system losing its thermal equilibrium with temperatures climbing inexorably upwards until the whole system fails. Although this problem can be overcome, it may require special design and the use of cooling technology.

As a specialist in power system engineering and maintenance Chloride Harath carries out more than 500 load tests each year. This experience shows that many systems installed in the UK struggle to maintain thermal equilibrium at 30°C ambient temperatures – very few systems would sustain thermal equilibrium at 35°C and above.

In the original article for BSEE, Chloride Harath examined the elements of risk to the operation of standby power systems dividing them into two main categories; Internal Factors, over which you may have control and External Factors, like climate and mains supply reliability that you may not be able to control but for which you could take mitigating actions. Among the internal factors considered were risk assessment, system design, quality of installation, ongoing maintenance, the age of equipment and condition monitoring.

The Disaster Recovery Journal clearly identifies that the biggest risk to any business, by far, is that of power outage. Yet a survey of Risk Management and Disaster Recovery Organisations shows that relatively little attention is given to avoiding the risks associated with power outage. The very first job in assessing the ramifications of a power outage should be a comprehensive risk study of your critical power systems and that should be reviewed annually. Problems with convergence of any the various risks, could be compounded by the reduction in inner city supply resilience at the very time when ambient temperatures are high.

For readers who would like to see the full content of the original article, Chloride Harath has produced its ‘Essential Check-list for your critical power system’ which is available upon request.

John Taplin has considerable engineering experience in the power protection business encompassing design, planning and the execution of major projects. He has been involved in many of the most extensive and technically demanding projects within Canary Wharf – home to the largest single concentration of operational Chloride UPS and static switches in the UK – and manages Chloride’s sales support team.

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