SPECIAL FEATURE
FIRE, SAFETY & SECURITY
POWERING A SAFETY-FIRST APPROACH Jenny Paramore, ABB Emergi-Lite’s Product Marketing Specialist, discusses the importance of selecting the best power supply equipment for emergency lighting – and explains how Central Power Supplies can safeguard people.
What do Central Power Supplies (CPS) contribute to emergency lighting systems?
ABB’s Emergi-Lite EMEX battery system is specified to deliver three and a half times the power of its output rating
Safety systems have always been important, but the 2017 Grenfell Tower fire really emphasised the need for more robust equipment and processes in buildings across the UK. Protecting residents, inhabitants, and visitors must always be paramount – and in a disaster situation, systems such as emergency lighting play a key role, guiding people to fire exits and helping them make their way to safety. CPSs (also known as static inverters) are a vital component of emergency lighting systems. They’re designed to offer the best possible performance in emergency situations, and while they may appear to be similar but more costly than an Uninterruptible Power Supply (UPS), there are important differences that provide peace of mind that your building’s occupants and visitors will be safe and sound within its walls. Both types of systems integrate batteries, chargers, alarms, circuitry, and instrumentation, and can be designed to provide three hours of power for all emergency lighting lamps and luminaries, with a response time of no more than five seconds.
Why don’t UPS systems work as well as CPSs?
What rules and regulations govern central power supplies?
While a CPS and a UPS will both provide backup power in the event that mains power goes down, UPS systems are seen as offering lower cost. This can be enticing to contractors and consultants on a tight budget. But safety can’t be compromised. The value that CPSs provide is that they have dramatically higher overload protection than UPS systems, meaning they’re better equipped to handle unexpected high fault currents that can arise in the immediate aftermath of an explosion or a fire. CPSs are rated to provide power to operate a building’s main switchgear before supplying up to 180 minutes of fail-safe power for emergency lighting systems. For example, the Emergi-Lite EMEX battery system is specified to deliver three and a half times the power of its output rating. This gives it the capability to clear fault currents and disruptions. Without the same level of overload protection performance that is built into a CPS, a UPS may not work as expected in the event of a physical disaster, because it would not be able to provide switching power required for the main switchgear to clear high fault currents. Unless it is specified as an uprated version, a UPS doesn’t have the ability to operate a switchgear, and why would it? It’s designed to provide backup power in data centres and telecoms installations – supporting cooling systems, electronic loads, and supplying enough power to bridge the period between the beginning and end of an outage. UPS units also regular power quality by absorbing voltage spikes and sags to protect high-value server racks and electronics, but they are not specifically designed for emergency power scenarios – they don’t have the power to switch the main switchgear, and therefore aren’t as reliable for emergency lighting. Essentially, a UPS system has a response time of minutes. A CPS system can respond in seconds. In an emergency situation, that can be the difference between a nuisance and a tragedy.
The UK uses a number of different standards for emergency lighting, chiefly the BS EN 50171 standard, which covers central power supplies. UPS systems don’t tend to meet this standard without a contractor uprating them, whereas CPSs are designed to meet them from the outset to be fit for purpose as far as emergency lighting systems are concerned.
“There has never been more scrutiny on safety systems in buildings, but manual testing of safety systems is a costly, timeconsuming process.”
The Emergi-Lite EMEX battery system has the capability to clear fault currents and disruptions
Are there any other differences? The other main difference is that a specially designed CPS can also help building managers meet government regulations for testing and reporting. There has never been more scrutiny on safety systems in buildings and it is vital that records are maintained – but manual testing of safety systems is a costly, time-consuming process. As a result, the latest generation of CPS integrates software and electronics that will look after periodic testing and record keeping in adherence to the IEC 62034 standard for automatic testing. This feature will run tests on the lighting circuits on a CPS to ensure they are operating as they should be. Essentially, during this process, a software controller will duplicate the conditions of a power cut and check emergency lighting circuits to find out if everything’s working properly. The system then records and uploads test results to building management systems such as LonWorks and BACnet and will send an alert if it detects a fault. In comparison, a standard UPS system will not have this functionality as a standard option – so will require additional engineering time and effort to set up and commission. As a result, their testing and reporting capabilities are another good example of why CPSs are better from a physical safety and from a cost standpoint. They might cost more upfront, but they’ll save your building money and time in the long run. A CPS is about more than performance – it’s about peace of mind. ABB, new.abb.com/uk
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