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Solid-state trip device comprising a zero sequence current detection circuit

  • US 4,899,246 A
  • Filed: 03/01/1988
  • Issued: 02/06/1990
  • Est. Priority Date: 03/09/1987
  • Status: Expired due to Term
First Claim
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1. A multipole electrical circuit breaker, protecting an A.C. electrical supply system, including a solid-state trip device, comprising:

  • a current sensor per pole, which generates a signal proportional to the current flowing through the associated conductor of the supply system protected by the circuit breaker;

    a detection and rectification circuit to which said signals are applied to supply on the one hand signals representative of the currents flowing through the conductors to be protected and on the other hand a zero sequence signal if an insulation fault occurs; and

    an electronic processing unit to which the output signals from the detection and rectification circuit are applied to perform delayed and/or instantaneous tripping functions and delivering, with or without a time delay, a circuit breaker tripping order when preset thresholds are exceeded by the signals representative of the currents flowing through the conductors or by the zero sequence signal, wherein the detection and rectification circuit comprises first rectification means producing a first signal representative of the sum of the positive half-waves of the output signals from the set of current sensors, second rectification means producing a second signal representative, in absolute value, of the sum of the negative half-waves of the output signals from the set of current sensors, and means effecting the difference between the first and second summed signals so as to produce said zero sequence signal.

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