Voltage transformer primary side neutral point controllable impedance harmonic elimination device

Abstract

The invention discloses a voltage transformer primary side neutral point controllable impedance harmonic elimination device. The device comprises a controller and a primary harmonic elimination controllable impedance; the primary harmonic elimination controllable impedance is composed of a switch K and an impedance Z, and the switch K and the impedance Z are connected in series or parallel; one end of the primary harmonic elimination controllable impedance is connected with a primary neutral point of a voltage transformer, and the other end is grounded; the controller judges that the voltage transformer is in resonance and the system is in single-phase grounding according to the voltage transformer secondary side three-phase voltage and / or voltage transformer secondary side opening triangle voltage; when the voltage transformer is in resonance or the power grid is in single-phase grounding, the controller controls the switch K to alternately open and close, thereby alternately changinga circuit parameter of a circuit located by the voltage transformer; the resonance is disappeared, or the voltage transformer is prevented from producing resonance; in the normal running, the opening-closing state of the switch K is maintained; and the primary harmonic elimination of the voltage transformer can be realized, and the safety running of the system is ensured.

Description

technical field [0001] The invention relates to a primary harmonic elimination device for a voltage transformer and a device for automatically insulating the neutral point of the voltage transformer in a line power failure from the ground. Background technique [0002] The voltage transformer is referred to as PT, and the resonance of the voltage transformer is a common fault in the power grid. GB50064 "Code for Design of Overvoltage Protection and Insulation Coordination of AC Electrical Installations" provides a variety of measures to eliminate resonance and overvoltage in Article 6, including : [0003] 1. Select an electromagnetic voltage transformer with a higher excitation characteristic saturation point; [0004] 2. Reduce the number of neutral point grounding of voltage transformers in the same system. Except for the neutral point grounding of high-voltage windings of voltage transformers on the power supply side, the neutral points of other voltage transformers sho...

AI Technical Summary

Problems solved by technology

In recent years, there have been primary resonance eliminators using nonlinear resistors such as silicon carbide and thermistors. However, on the one hand, nonlinear resistors affect the accuracy and reliability of voltage criterion protection, and injecting nonlinear quantities into the system does not It is conducive to the safe operation of the system; on the other hand, the nonlinear resistance makes the neutral point of the voltage transformer equivalent to the ground, which makes the protection equipment that needs to protect the ground voltage unable to work normally; Accidents where mutual inductors burnt together occur frequently

[0010] In addition, after a power outage, especially after a system failure, when performing a voltage withstand test on the line before power transmission, if a DC tester is used to perform a DC withstand voltage test on the line, all PTs on the line need to be manually pulled apart. , this process is time-consuming and laborious, as long as one PT is not pulled apart, the test cannot be implemented

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