ELECTRICAL RESILIENCE
Rapid response to generator issue at Scarborough hospital
HTM 06-01 is one of the most recognised sets of guidelines in the healthcare sector. Samuel Rea, Healthcare divisional manager at Power Control, emphasises the importance of secondary and tertiary power supplies, drawing on an example of a recent project undertaken by the company at Scarborough General Hospital, where it stepped in rapidly to help when two of the main generators failed.
Rapidly advancing healthcare technology is transforming the way patients are being diagnosed and treated. From sensitive medical imaging equipment, to connected devices, data monitoring, and laboratory testing, the future of healthcare lies in working hand-in-hand with technology, and with that comes a greater need for 24/7 regulated power and strict guidelines to ensure the safety of all patients and staff within the sector. Healthcare facilities in the UK should all follow a set of guidelines set out in Health Technical Memorandum, HTM 06-01: Electrical services supply and distribution, which outlines the safe practice of a facility’s electrical services supply and distribution. The guidance document emphasises the need to have both a secondary and tertiary supply of power to provide a back-up in case the primary supply (mains) fails.
Automatic switchover During a mains failure, a UPS would not have enough autonomy to support a hospital’s operational needs alone, but it provides a short ‘bridge’ while the generators kick in to supply the hospital with emergency power for the duration of the power outage. The generator starts up when the automatic transfer switch (ATS) senses the loss of power, and, once stabilised, the load is automatically switched over to the generator. A UPS system can support a load for a short duration itself determined by the size and number of UPS systems on the site, and the size of the load they are supporting. The ATS delays its signal to the standby generator by approximately 10 seconds, preventing the generator from having to start up unnecessarily. In contrast, the ATS will keep the UPS and generator running for a period of time, usually minutes, after the mains power is restored, to ensure stability.
As long as it is online double conversion, the UPS system continuously provides power to the load; there is thus no gap in power or transfer time when the mains
Delivery of one of the 770kVA standby diesel generators to Scarborough General Hospital just before Christmas last year.
power source fails, and the UPS batteries begin to support the load. Once stabilised, the load is automatically switched over to the generator.
Free from anomalies During normal operating circumstances, when the healthcare facility is running on mains power, an online double conversion UPS system also ensures that the power being supplied to sensitive medical and hospital equipment is clean and free from anomalies such as spikes, sags, surges, brownouts, noise, and transitory failures. The size of premises is often the principal factor dictating the size and
number of secondary power systems required to comply with HTM 06-01. Although in small healthcare premises the most economical and convenient arrangement may be a single diesel standby generator, hospitals typically require multiple generators because of their size, and the importance of power to overall operations. For larger premises, a better solution is for two or more standby generators, with interlocked and interconnected switching.
Scarborough generator failure When two of the main generators went into failure at Scarborough General
April 2022 Health Estate Journal 59
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