SOTF will operate by detecting the fault current and line voltage. In this case, also SOTF function will operate and trip the CB immediately. In this situation, the SOTF protection will cover whole the line and during the persisting fault, it will immediately isolate the line.įurther, after maintenance work of transmission line, it also found many cases, the line charged from the one end whereas the line earth switch of the line not opened at the other end due to human error.

Which is not healthy for the connecting equipment and system stability. If any persisting fault detects beyond 80% of the line length, the fault will detect under Zone-2 and it will operate after a delay of 300 to 500 ms. Under Zone-2 protection, the CB will trip after 300 to 500 ms in the fault condition and it will protect up to 120% of the total length of the line. Under Zone-1 protection, the CB will trip immediately in the fault condition and it will protect up to 80% of the total length of the line. We know that Distance Protection is responsible to isolate the fault of the transmission line. If any fault is persisting in the transmission line during energization of Circuit Breaker or fault happens within 20 ms from the CB closing, the SOTF protection will activate and it will trip the Circuit Breaker immediately to isolate the fault.

SOTF protection stands for Switch On To Fault.

What is tor stands for