Abstract: The trip device with an electronic processing unit which gives a tripping order in terms of the rms value of the current measured by current transformers and of the threshold and time delay setpoints. The non-linearity of response of the current transformers is corrected by a device which modifies the current, threshold, or time delay values. These corrected values enable precise trippings to be achieved in compliance with the values of the current flowing in the circuit breaker. The type of correction is adapted to the circuit breaker rating by parameters obtained by tests and previously stored in a device.

Abstract: To perform the long delay function of an electronic trip device, a quantity (TLR1) representative of the thermal current state varies proportionally to the difference (I.sup.2 -Is.sup.2) between the square of a value (I) representative of the current flowing in a conductor to be protected and the square of a current threshold (Is). This first quantity (TLR1) is used in combination with a second value (TLR2) to produce a tripping signal when the second value exceeds a preset value (TLR2max). The second quantity preferably increases proportionally to the square (I.sup.2) of the value representative of the current, when the first quantity exceeds a preset threshold (STLR1) and decreases, preferably exponentially, when the first quantity is lower than this threshold.

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.

Abstract: The circuit breaker comprises a thermistor located in a cold zone, near the front face of the trip device and at least one thermistor located in a hot zone, at the bottom of the circuit breaker case, in proximity to the circuit breaker connection terminals. The temperature difference measured between the hot and cold zones is representative of the temperature rise of the system protected by the circuit breaker and is used to modify the time delay of a delayed tripping function when the circuit breaker closes. The trip device can also take into account the temperature difference existing at the time of the previous trip.

Abstract: In a system-powered solid-state trip device, the measurement voltage Vm, representative of the current flowing in the conductor to be protected and applied to the input of an electronic processing unit, can also be applied to the cathode of a thyristor connected in series with the trip coil and receiving on its gate, the tripping orders from the processing unit. A Zener diode is connected between the thyristor gate and the ground so as to set an instantaneous tripping pick-up of the trip device. In this way, a short-circuit in the conductor causes instantaneous tripping of the circuit breaker independently from the value of the supply voltage.

Abstract: A signal representative of the zero sequence current is obtained from current transformers associated with each phase and with the neutral if applicable by separate summing, in two distinct conductors, of the positive half-wave currents and of the absolute value of the negative half-wave currents produced by the set of current transformers, the difference between the currents flowing through these two conductors being representative of the zero sequence current.

Abstract: A test circuit simulates the operation of a multipole electrical circuit breaker, and includes a pair of auxiliary terminals connected by a connection circuit to the input terminals of a bridge rectifier cell whose output is connected in parallel with the respective outputs to two other rectifier cells associated with current transformers. A first resistor delivers a first signal proportional to the maximum intensity of the mains currents. Diodes cooperate with a second measuring resistor of a residual earth leakage current discriminator. Reversing the direction of the test current flow in the test circuit is performed by simply changing the polarity of the test terminals, and enables overcurrent protection and earth leakage protection of the electronic trip device to be checked separately.