FR2657194A1 - REACTANCE CIRCUIT BREAKER WITH LOW OVERVOLTAGES. - Google Patents

Abstract

The invention relates to a reactance circuit breaker. It relates to a reactance circuit breaker comprising for each phase at least one interrupting chamber, provided with an operating member, and at least one varistor across said interrupting chamber, characterized in that said operating member (3 ) is under the control of an ordering circuit (8) to allow an opening ensuring a sufficient duration of arc to avoid any re-ignition at the terminals of said chamber. Application to the equipment of high voltage electrical circuits.

Description

LOW OVERVOLTAGE REACTANCE CIRCUIT BREAKER

  The present invention relates to a circuit breaker

reactance at low voltages.

STATE OF THE ART

  Cutting a high voltage shunt reactance (or breaking any other inductive circuit) creates constraints on both the reactance and the circuit breaker. The constraints on the reactance are on the one hand the amplitude of the overvoltage, especially following a reboot in the circuit breaker, and, on the other hand, the rate of increase of the overvoltage; this speed depends on the oscillation frequency of the busbar circuit This last constraint is detrimental to the wound windings; these voltage waves are called

cut waves.

  In the report "High frequency switching surges in EHV shunt reactor installation with reduced insulation levels", F-78 659-5, IEEE PES, July 1978, Los Angeles, it was reported surges of 2.3 pu and frequencies of 300 kHz measured on a 500 kV reactance circuit of the BPA (Bonneville Power Administration, USA) The du / dt obtained is of the order of 560

Kilovolts by microseconds.

  According to this report, the design of the reactance allowed the latter to support without difficulty

all these constraints.

  In the report "Cutoff of inductive currents of shunt reactances at extra-high voltage", CIGRE 1978, report No. 13-06, surge waves with a front duration of a few microseconds were measured on

  networks 500 k V and 750 k V Soviet.

  In the report "Particular Problems of Cut-off of Industrial Circuits and their Solution by the Use of 2 Nonlinear Damping Resistances", CIRED Conference May 1977, London, Report No. 06-4, it is stated that, depending on whether the neutral of the circuit is isolated or grounded, it is possible to obtain more or less overvoltages With an isolated neutral, the overvoltage can reach 4 to 5 pu following reboots in the circuit breaker The authors strongly advised the use of resistors not linear to avoid reboots in circuit breakers and variations

  l O rapid tension resulting from it.

  The constraints on the circuit breaker are, for a voltage across the circuit breaker too high due to excessive current pulling for example, either an internal ignition or external bypass, which have already resulted in explosions of circuit breakers, if the weather conditions are unfavorable (snow, rain causing a bad distribution of the voltage on the circuit breaker, in particular in the case of a breaker with several

bedrooms).

  To reduce the amplitude of the overvoltages on the reactance, one can either use arresters at the terminals of the reactance, or prevent reboots in the circuit breaker, especially high reboots which

  cause high overvoltages.

  In the last quoted report and in the report "Non-overvoltage circuit breakers", CIGRE, 1958, report No. 146, it was proposed to use variable or non-linear resistors across the circuit-breaker for

limit overvoltages.

  In German Patent 2,361,203 of June 12, 1975 (Siemens), non-linear resistors with Zn O type metal oxides have been proposed. 3 The use of zinc oxide makes it possible to dispense with a series switch , given the high coefficient of non-linearity, of the order of 50 to

  compare to 6 for silicon carbide.

  This allows to obtain a current of very

  low to the permanent operating voltage of 1 p u.

  The higher the operating voltage of the varistor

  is low, the more effective the protection will be.

  In the current state of performance of the zinc oxides, it is not possible to set the operating threshold of the varistors below 1.5 to 1.6 pu without risking overheating the varistor in continuous operation to 1 pu, unless you use a switch

series with the varistor.

  To prevent ignition in the circuit-breaker, which causes wear of the contacts and the insulating nozzle, and creates steep-wave surges in the reactor, the authors of CIGRE report 13-06 of 1978 quoted above proposed to use the synchronized opening of the circuit breaker to avoid arc times

  short, that is to say, small distances between contacts.

  This is to synchronize the opening of the circuit breaker with the beginning of the industrial frequency current wave in order to obtain arc times of

cut long.

  By detecting the supply voltage of the reactor and taking into account the opening time of the circuit breaker, it is also possible to synchronize the opening of the circuit breaker with the voltage wave to have long arc times, knowing that the current is in quadrature with

voltage.

PURPOSE OF THE INVENTION

  An object of the invention is to provide a circuit breaker

  Low voltage surge reactance.

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OBJECT OF THE INVENTION

  The subject of the present invention is a reactor interrupter comprising for each phase at least one interrupting chamber, provided with an actuator, and at least one varistor at the terminals of said interrupting chamber, characterized in that said actuator is under the control of an ordering circuit to allow an opening ensuring a sufficient duration of arc to avoid any rebooting at the terminals of

said chamber.

  Advantageously, said varistor has a value of

  operation between 1.5 and 1.7 p u.

  DESCRIPTION OF A MODE Pk EFJOE Ki OF REALIZATION

  The invention is specified by the description of a

  preferred embodiment, with reference to the accompanying drawing in which the single figure is a schematic view of a phase of the circuit breaker of the invention and the associated reactance. In the figure, the reference numeral 1 designates a breaking chamber disposed at the end of a support 2 and operated by an actuator 3 The disjunctor is in series in the circuit 4 with a reactor 5 A varistor 6 is connected to the terminals of the breaking chamber. According to the invention, the circuit breaker is controlled by a synchronized opening gating circuit 8; the latter receives voltage information, for example by a capacitive divider C1, C 2, and current information, for example by means of a current transformer 9. From these data, the client prepares a trip command at a chosen time to ensure a sufficient arc time to avoid any reboot in the circuit breaker.

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  The presence of the varistor protects the circuit breaker against any voltage overload exceeding

  operating threshold of the varistor.

  It is noted that any excessive tearing of the current to be cut can create a high overvoltage; moreover, rain or snow can overload one of the

  or more of the breaking chambers of a given phase.

  Since there is no more reboot in the circuit breaker, the operating voltage threshold of the

  varistor can be usefully set between 1.5 and 1.7 p u.

  This voltage threshold will be determined as a function of the dielectric behavior between input and output of the

  circuit breaker and not that of the reactance.

  The invention finds application in the equipment of

  high voltage electrical networks.

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Claims (2)

  V / Reaction circuit breaker comprising for each phase at least one interrupting chamber, provided with an operating member, and at least one varistor across said breaking chamber, characterized in that said actuating member (3) is under the dependence of a gating circuit (8) to allow an opening ensuring a sufficient arc duration to prevent any rebooting to terminals of said chamber.   2 / circuit breaker according to claim 1, characterized in that said varistor (6) has a value of operation between 1.5 and 1.7 p u.