Making Power Sub-Station Safe

Human resources are considered as the invaluable assets. In low voltage (LV) and medium voltage (MV) substations, there is always a chance that people working around may get exposed to Arc Flash situation which is considered as the most fatal fault that may cost human lives. Arc Flash fault when occurs it releases huge amount of heat and light energy similar to a very powerful bomb blast causing huge damage to equipment, buildings and most importantly humans.

How Arc Flash occurs?
Arc Flash can occur because of placing of any instrument like spanner or something similar to it in busbar chambers or may be because of intrusion of animals like rats, lizards etc. causing short circuits in cable, busbar or breaker chamber or any undefined accident causing shorting of busbar or cables.

Can we avoid Arc Flash?
The damage due to Arc Flash explosion can be minimised by using proper protection relays.

Are regular numerical feeder protection relays sufficient to avoid Arc Flash fault?
Simply put – no. Various studies have shown that if Arc Flash fault is cleared within 100 milliseconds (ms) or less, there are increasing chances that human lives can be saved and cause minimum damage to equipment. Conventional relays are not fast enough to avoid Arc faults and normally take 40-60 ms to trip after that tripping time of master trip and breaker gets added which results into slower operation than desired.

What is the principle behind Arc Flash relays?
• Detection of light: By putting light sensors in busbar, breaker and cable compartment light gets detected and tripping command can be send to breaker directly within 10-20 ms.

• Detection of light and current both: In this method, current is used as additional check to avoid malfunctioning which is caused by false light signal.

For more details on Arc Flash explosion
protection relays, mail at dnyanesh@reliserv.in or visit www.reliserv.in