Neutral Unbalance Current Relay

Application:

Neutral unbalance current protection of double star capacitor banks with floating neutral.

The sensing current is converted to voltage by an internal resistor and this voltage is fed to a harmonic network which is tuned to the fundamental frequency. The output of filter is fed to a voltage comparator. When the sensing current signal at the fundamental frequency exceeds the set value, the comparator gates a train of pulses to the processor. The program residing in the CPU performs the function of control and also gives output signals for relay and LED driver circuits. The operation of the relay is indicated by the glowing of a 'Red' LED,which has to be reset manually by means of a 'RESET' push button provided on the front of the relay. A 'Trip Test' push button is also provided in the relay to enable testing of the trip and alarm circuits. When this push button is pressed,the output element of the relay is energized and its contacts close to energize the trip and alarm circuits.