Power interruptions are a threat to office systems, says Martin Coulthard

The recent power outage in London and events in the USA, Canada and Italy, together with warnings from the UK power generation and distribution companies, have raised awareness of the fallibility of our power supplies. Relying totally on the availability of mains electrical power is folly, for interruptions occur far more frequently than is generally recognised.

As well as power cuts, other disturbances to supply, such as surges, sags and electromagnetic interference, can affect the performance of sensitive electronic devices. These 'unseen' events constitute the largest threat to the operating capabilities of electronic equipment and contribute to the premature ageing of components. Equipment that has defined operating tolerances requires a clean and stable sinewave at all times.

Power outages are indiscriminate and caused by factors which are often outside the control of the power generators and distributors. When they occur, the result could be the loss of important data and disruption to operating systems. The cost in terms of lost business can be substantial, and reconfiguring systems may be time-consuming and expensive. It is not uncommon for businesses never to recover fully from a serious IT failure. The potential consequences for the healthcare and emergency services sectors are particularly worrying.

Commerce, national and local government and the emergency services rely on mission-critical systems, so their disaster management strategy should include power protection. This element is often either completely overlooked, or dismissed on the grounds of expense. However, for business continuity, a power protection system supporting mission critical equipment is as important as a back up power supply, in the form of a diesel generator set.

Power protection is readily available and comes in the shape of a UPS (Uninterruptible Power Supply) at a price that is often far less than the infrastructure being protected. It should no longer be considered an additional feature; it is an essential piece of technology.

How it works

The UPS is an item of electrical hardware that is positioned between the incoming mains power supply and selected items of electronic equipment, normally referred to as the 'load'. In the event of a power outage, its main purpose is to ensure that clean, unbroken power is available for a set time interval so that equipment can be safely shut down if necessary.

For large organisations, investing in an effective power protection solution may go beyond the purchase and installation of a UPS unit. The reliability of the power distribution infrastructure within buildings is critical to the availability of the power protection system. A high proportion of system failures are caused by problems in the distribution network within a building.

Where there is a demand for the constant availability of mission-critical systems, careful consideration should be given to designing and implementing a tailored power protection system. Providers of power protection solutions can help to establish the size of the load and the protection needed.

For example, installing a double conversion UPS can ensure the continuity and quality of the power supply, together with stable voltage and frequency at all times. Built-in redundancy, in the form of either an N+1 (Needed plus Standby) or N+N (Needed + Needed), provides additional layers of support and non-stop power availability.

How long the UPS will run for in an emergency varies according to the requirements of the user, the load and battery size. Periods can range from just a few minutes up to a couple of hours, so it is definitely not a substitute for a standby power diesel generator. However, where the standby power is fed from a generator through the UPS, the quality of the power can be substantially enhanced.

The international finance community has long been a major user of UPS technology, and the emergency services and health sectors have also substantially increased their investment in power protection equipment.

In hospitals it is common practice to operate essential and non-essential power supplies. In the event of a power outage, the essential supply supports all mission critical systems. The diversity of the demands for power protection within a hospital, together with the number of buildings normally located on a campus, mean that UPS units are usually dedicated to specific areas and items of equipment, such as critical care beds, and accident and emergency wards.

The dangers of relying on the mains power supply are evident. The availability of UPS systems from products for single PCs through to configurations of several MVA, means that there are power protection solutions for all eventualities and budgets.

Martin Coulthard is marketing manager, Chloride Power Protection, Tel: 02380 610311, E-mail:

Average cuts

Each year the UK Ofgen Distribution and Transmission Systems Performance Report publishes the average number of power cuts experienced by customers, together with the average number of minutes being lost. The report for the year 2001/2002 shows that the average number of customer power interruptions per 100 customers was 87.4 and the average number of customer minutes lost was 83.7.


The recent power outage in London was a test for Chloride's LIFE.net 24/7 system, which offers self-diagnostics; shutdown software, automatic battery monitoring, remote interrogation and power supply trend analysis. Chloride engineers were able to keep every connected customer informed as to how their UPS was functioning, as well as providing advice on factors, such as air conditioning failures, which could influence UPS performance. The equipment's environment is one of the parameters LIFE.net monitors. It proved particularly valuable to the transport network, where availability of continuous power to control rooms and emergency lighting for commuters' safety were priorities.