ELECTRICAL RESILIENCE
electrical design standards. While the severity varies between UPS types, due to the nature of their design, transformer- based solutions are more resilient. However, regardless of UPS topology or type, nearly all back-up power solutions require a permanent neutral connection. The HTM advises designers to ‘consider the use of an external delta zigzag DznO isolation transformer to supply a fixed neutral reference to earth on the secondary supply side’. Doing this would also improve the earth- loop impedance to address BS7671 requirements. To ensure that UPS systems and the load have a permanently grounded neutral point, HTM 06-01 also suggests the use of this transformer on the UPS bypass line, which is on the input side. It is possible to install an external isolation transformer on either the UPS output or input, but placing it on the former will not provide a direct neutral reference to the UPS.
Dual supply
With regard to dual supply, most three- phase UPS solutions have the capacity for dual input supplies – a dedicated bypass line input and a separate rectifier input. This configuration is recommended, as it increases the resilience in the event of a fault, and can increase availability after a mains failure. Most UPS topologies will allow an input transformer to be installed on the bypass line when both supplies are from the same local source. Complications can arise if dual UPS inputs are from separate, unsynchronised sources. Standard commercial UPS systems bond separate neutral paths internally, which inherently changes the electrical design. It is advised, therefore, that specific UPS types – such as those from Borri Spa, which are compatible with unsynchronised inputs – are the preferred choice.
However, it is not just performance standards that need to be of the highest calibre; healthcare estates and healthcare engineering teams are under immense
Graeme Tucker and Power Control
Graeme Tucker has been with Power Control (formerly Borri) for over 20 years. With an electrical background, and years of experience in the power protection field, he now provides direct leadership and strategy for the company’s sales divisions as Sales director. The healthcare arena is one that he was personally responsible for developing in his early years at Power Control, and he continues to play an active role in supporting this key industry. Known within the industry for his extensive technical knowledge, which extends beyond just UPS systems, he is a trusted advisor for leading organisations across the UK.
Power Control has had over 26 years’ experience in the field, and has delivered hundreds of power protection solutions to the healthcare and medical industry. The company supports NHS facilities and healthcare estates across the country with project delivery and maintenance support for UPS, IPS, and other associated equipment. Power Control is part of the NHS SBS Hard Facilities Framework Agreement, has long- standing partnerships with global UPS manufactures including Borri Spa, Legrand, Huawei, and CertaUPS, and a product portfolio extending from 800 VA to 6.4 MVA.
pressure to reduce maintenance and energy costs without compromising patient care. Huge investments have been made by manufacturers such as Borri Spa and Legrand to achieve maximum UPS efficiency with their systems. A key part of Power Control’s consultative role is helping end-users realise those efficiency savings through careful strategy planning. Rather than reviewing areas in isolation, we look at the entire electrical landscape, as often this can achieve up to 15% greater efficiency gains. Equally, this also contributes to an improved TCO (total cost of ownership), and can even support more efficient maintenance strategies.
Keeping back-up power solutions in optimal condition Finally, effective maintenance is absolutely crucial. Like many other electrical devices found within a healthcare facility, UPS systems cannot afford to be neglected. Their installation will be part of a critical infrastructure plan, and must be able to safeguard the load in the event of a mains failure. It is therefore paramount that any back-up power solution is in optimum condition. It is recommended that routine preventative maintenance checks are carried out at least every six months. Adopting a regular schedule of service visits will ensure that systems are not neglected and forgotten about until it is too late. hej
October 2020 Health Estate Journal 71
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