Under-frequency protection relay PHD series

over-frequencysingle-phaseDIN rail

The Frequency protector set point adjustment range is centred around the nominal system frequency of 50, 60 or 400Hz. The adjustable differential setting can be used to reduce nuisance tripping if the measured signal is noisy or unstable. Under normal conditions, with the supply frequency close to the nominal set point, both red LEDs are off with the Under relay energised and the Over relay de-energised. Should the supply fall below the opening threshold, both relays will de-energise and both red LEDs will flash slowly to indicate insufficient supply voltage.