Time graded phase and earth fault protection in JD100

Our numerical feeder protection relay type JD100 comes with time graded phase and earth fault protection of transformer, feeder and capacitor bank. The relay featured with MODBUS/IEC 60870-103 standard communication protocol over RS-485 facilitates interfacing the relay with SCADA systems and RS-232/RJ45 communication port provided at front of the relay allows engineers to programme the relay easily. Certain advanced features such as negative sequence protection, broken conductor detection, cold load pickup, RAPID (Rapid automatic planned imbalance current detection), local breaker backup and auto reclose improves the selectivity, sensitivity and stability of the power system.

Our numerical feeder protection relay measures the line current from each of the line CTs and if the current exceeds the set threshold, then relay extends a trip signal after an operating time. The relay’s “operating time” is determined by selecting “definite time” or one of the six “inverse time” characteristics. This principle of relaying is equally applicable to phase, earth fault and negative sequence protection elements (51N / 51G / 51Q).

Ratio of negative phase sequence current to positive phase sequence is used for broken conductor protection. If the ratio of positive phase sequence current to negative phase sequence current exceeds the user set value, the relay extends a trip signal after a definite operate time set by the user.

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