There are very few disasters so common and yet so potentially deadly as a fire. Be it inside a moving metal wagon or deep underground within a concrete tunnel, the deadly threat of an ignition and its consequences makes fire safety of the utmost importance in the rail sector.
To talk about that subject and how to prevent it, SmartRail World brings you John Newbury, Product Manager at Ramtech Electronics. John has a background in electronics and wireless technology and has been a part of the design, patenting, and development of a range of safety technology for the UK, and today, he joins us with an expert look at how the latest technology makes a steep change by preventing electrical fires before they start.
A major incident in June 2018 involving an electrical fire beneath a train lead to severe disruption at London Waterloo -- the country’s busiest railway station -- and numerous other electrical fires are regularly reported around the UK. Electrical fires are common to both rolling stock, station buildings and signalling assets. However, proper fires on-board trains and within railway buildings are thankfully rare, mainly down to the fact that the industry's use of fire resistant materials has done much to reduce the risk of it starting in the first place. But there is no room for complacency -- even small fires can escalate to something far more dangerous or be hugely disruptive to commuters and passengers.
Currently, all materials used in rail vehicles must follow the EN 45545-2 standard in order to achieve the highest level of fire safety. It covers the fire behaviour of materials and components including flooring, seats and cables on railway vehicles. BS EN 45545- Part 5 sets out the fire safety requirements for electrical equipment including that of trolley buses, track guided buses, and magnetic levitation vehicles.
The standard aims to lower the risk of a fire starting during operation as a result of technical defect and/or malfunction of the electrical equipment, and to ensure that electrical emergency equipment continues to be functional until evacuation is complete. In addition, there are a range of building regulations and other safety standards that cover the risk of fire in all buildings. These apply to stations, signal boxes, tickets offices, passenger waiting areas and other structures on the network.
The dangers of electrical fires
Several of these standards require protection against electrical overload and short circuiting, which generally means incorporating Circuit Breakers, RCD's, and RCBO's. However, these devices are unable to detect heat generated at points of connection, and therefore fail to respond to around 80% of electrical fires within low voltage installations. The danger of a fault developing at connections, causing "resistive" heat build-up, is exacerbated on rolling stock due to constant movement and vibration causing chafing and loosening of wiring.
Circuit Breakers, RCD's, and RCBO's are designed principally to avoid a person from being electrocuted, and cannot detect elevated temperatures generated by resistive heating. In order for them to operate and isolate the supply, ignition would have already occurred. Resistive heating of connections can generate heat in excess of 1000°C, well above the ignition point of many materials.
An effective method of detecting build-up of heat before ignition occurs would prevent many electrical fires. This was the start point for us when we set about developing WES Hotspot, a technology that monitors electrical installations and equipment, alerting nominated personal to the risk of an electrical fire long before it ignites. The Thermarestor technology behind WES Hotspot works by activating as soon as abnormal heat (80ºC ± 5°C) is detected. Once activated, these Single and Multi-Point Sensors provide a signal to an alarm system before the temperature increases further to the point of ignition.
Optionally, it is possible to automatically isolate the circuit supply by operating an RCD. In safety critical applications within the rail network, specifying the alarm option means power is not cut, whilst still highlighting that urgent action is needed by maintenance teams to prevent a far more serious situation developing. The range has been independently tested and is compliant with all applicable statutory regulations and requirements.
A smart solution
A report by the UK's DTI (Department of Trade and Industry) estimates that only 20% of all electrical fires could be prevented by the presence of an RCD, which still allows the remaining 80% to occur. The main source of ignition in electrical fires within low voltage installations is excessive heat. Circuit Breakers, RCD's and RCBO's are unable to detect heat generated at points of connection and therefore fail to respond to this major cause of fire until ignition has occurred.
RCDs are designed principally to avoid a person from being electrocuted and cannot detect the elevated temperatures generated by resistive heating. In order for an RCD to operate and isolate the supply via a current imbalance, ignition would have already occurred.
There is no doubt that a growing number of rail operators are seeking smart, technology-led approaches to fire safety, and that ought to include pre-ignition solutions that prevent a fire occurring in the first place. The benefit of alerting nominated personnel before the build-up of resistive heat causes outage or a fire offers significant benefits to operators looking to avoid passenger disruption. The technology has the ability to turn what at best could be major delays for passengers and at worst an emergency, life threatening situation into a simple maintenance task. The technology can be easily retrofitted to distribution boards, sockets and electrical equipment. Advances such as this provide an effective, easy to fit solution that actively prevents electrical fires.
For more information about crucial industry topics, including fire safety and security, join us at SmartTransit LA, on October 28-30th.