THE COMPARISON BETWEEN PRIMARY AND SECONDARY RELAYS IN THE 20 KV LINES

The over which is designed for protecting and highvoltage generators lines consists of two groups :The first one is primary rc1ay that series connected with the pole of the circuit breaker. Thesecond one is secondary relay which is unusual in lran and is high cost for. Protecting This presents the other lectronic primary which is mplemented relay , and a description about one project, which is implemented in Iean switch research department This relay is suitable for direct tripping of medium voltage circuit breakers andhas the following advantages : - Minimum overall dimension - Low power consumption - High drop – out / pick – up ratio When line current exceeds of the preset value , the secondary currents operate the electronic circuit ,firing the final SCR ontinuous setting of operating current and time. SCR Which permits the current flow necessary to operate the relay operation can occur instantaneously or with a preset delayed time according to the over current value through the circuit breaker pole.