Merlin Gerin

Alain Del Vecchio

Marc Ferrazzi

Paul Tripodi

The terminals of a test circuit are directly connected to outputs of the transformer secondary windings and to the input of the rectifying circuit so that the test current checks operation of the trip device. A sign detection circuit supplies a processing circuit with the values of the polarities of the rectified currents. The processing circuit comprises means for determining the presence of a test current when the sign of the rectified current comprising the test current remains continuously in the same polarity. A differentiation of the continuous polarity, positive or negative, of the test current enables testing to be carried out with or without earth protection tripping.

Electronic trip device comprising a test device

An electronic trip device comprising, for each phase or neutral line, a rectifier bridge formed by four diodes which rectify the transformer current, a resistance for measuring the rectified current, and a circuit for detecting the sign or polarity of the measured current connected to one end of the transformer. A processing circuit calculates a value representative of the earth fault current by adding all the current values whose corresponding sign is positive and subtracting all the current values whose corresponding sign is negative. This current value is processed so as to bring about tripping when a threshold is exceeded for a preset time.

Electronic trip device comprising an earth protection

The differential tripping threshold of the trip device is a polynomial function of an order greater than or equal to two of the highest phase current flowing in the power system protected by the circuit breaker comprising the trip device.

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Echirolles, France

Alain Del Vecchio