Numerical Over Flux Relay JNF 020

Application:

JNF 020 Over flux relay is used in power systems in order to protect transformers and generators against insulation failure and core damage due to over heating under prolonged over fluxing condition. It protects the equipment against abnormal V/F ratios due to system disturbance which can occur during starting, load sheding and shut down conditions.

Over fluxing of a transformer occurs when its flux density exceeds rated density, it is caused when its V/F ratio is greater than that which the manufacture deems it safe. This of course is the case when it is connected directly to the generator i.e, without benefit of an intervening circuitbreaker and the generator’s excitation system is energized while accelerating to operating speed JNF 020 monitors voltage & frequency ratio, when it exceeds the set value it indicates fault and the output relay operates after a set alarm time delay.