This relay is used to monitor the frequency of an electrical system. The relay are suitable for any application in industrial plants and to generators where definite time under or over frequency protection is required.
The operating principle of the relay is the comparison of the time interval of the incoming frequency with that of a preset time derived from an accurate oscillator within the relay. The incoming frequency signal is connected to an INPUT CIRCUIT, which then drives an IMPULSE GENERATOR to produce a pulse at the beginning of each period of the input voltage. The preset time interval is obtained from an OSCILLATOR and COUNTER and adjustment is achieved using SELECTOR switches, which drive a DECODER circuit. A COMPARATOR compares the two-time interval and this triggers an adjustable TIMER which then operates the output relay and latched light emitting diode (LED) glows.
