Abstract: The electronic trip device includes a processing unit having inputs to receive electrical signals representative of electrical quantities and an output to supply a tripping signal to a tripping relay, and a man-machine interface connected to the processing unit to supply setting parameters and to display information and tripping curves on a screen. The man-machine interface includes display means displaying setting parameters which modify the visual aspect of at least one portion of curve representative of a parameter whose setting is being adjusted. The circuit breaker includes such a trip device connected to current sensors and to contacts to interrupt currents in electrical conductors.

Abstract: The electronic trip device comprises in series for each phase of a power system a sampler, a squaring circuit and a finite impulse response (FIR) filter. A maximum circuit is connected to the output of the FIR filters and to the input of an infinite impulse response filter. A comparison circuit for comparison to thresholds is connected to the output of the IIR filter. It is thus possible to obtain both a good precision and good filtering of the harmonics of the frequencies of conventional power systems (50 Hz, 60 Hz and 400 Hz), and to reduce the necessary computing power, and consequently the cost of the trip device.

Abstract: 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.

Abstract: 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.

Abstract: 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.