Neutral Unbalance Current Relay JRC 122

Additional Details

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.

 Features:

Software-based design

Instantaneous/Definite time

Insensitive to harmonics

Wide setting ranges

Trip test facility

 Application:

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

 Burden:

Current input : 0.2VA at Rated 5A, 0.05VA at Rated 1A

Aux. Supply : Less than 3W (Non Operated),  Less than 5W (Operated)

 Aux. Supply :

1) 20 to 60V DC

2) 75V to 150V AC/DC

3) 175 to 300V DC

185 to 250V AC

 Insulation:

(1) 2KV RMS, 50 Hz for 1 minute / 2.5 KV for 1 sec Between all terminals and earth.

(2) 1 KV RMS, 50 Hz for 1 minute across open contact

 Settings:

(1) Definite time : 0 to 25 seconds adjustable in steps of 0.1 second.

(2) Rejection ratio of 3rd harmonic to fundamental frequency: 25 : 1.The relay will not operate at third harmonic currents up to 25 times the settings