Method for judging breakage of voltage transformer circuit

Abstract

The invention discloses a method for judging the breakage of a voltage transformer circuit; the secondary side three-phase voltage and the open triangular zero sequence voltage of a generator terminal voltage transformer TV are measured, and the tertiary harmonic voltage UA3, UB3 and UC3, and the tertiary harmonic component 3U03 of the open triangular zero sequence voltage are calculated; the value of the secondary phase voltage side is return counted to be U'03 according to the voltage transformation ratio of the voltage transformer TV on the 3U03: Umax=max{UA3, UB3, UC3, U'03}, Umin=min{UA3, UB3, UC3, U'03}; and when the Umax >=K.Uset0 and Umax>=K.Umin are met simultaneously, the breakage of the TV circuit is judged, wherein K is the fixed slope value, Uset0 is the inflection point fixed voltage value, and the two are constants. The method can accurately judge if the TV circuit is broken, and because the voltage measured of the TV is only used, the voltage of other TVs or the current of a TA do not need to be measured, and the criterion is simple and is easy to realize.

Description

technical field [0001] The invention relates to the field of electric power systems, more specifically to a method for judging disconnection of a voltage transformer circuit in a voltage measuring circuit of a generator, and to a relay protection device and a safety automatic device using the judging method. Background technique [0002] The generator is equipped with a voltage transformer (TV) at the machine end to monitor the voltage output of the generator when it is running. A fuse is connected in series on the primary side of the generator terminal TV, and a low-voltage miniature circuit breaker is connected in series on the secondary side. The fuse on the primary side may be blown instantaneously, poor contact or slow blown; the miniature circuit breaker on the secondary side may be disconnected; in addition, there may be loose wiring in the circuit, poor contact caused by the TV trolley not being pushed in place, etc. . All these situations, collectively referred to...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is: in order to overcome the existing TV loop disconnection discrimination method can not effectively distinguish the TV loop disconnection under various circumstances, to provide a method using the third harmonic voltage value and the third harmonic zero-sequence voltage value can effectively The method of judging the disconnection of TV circuit

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