Ferroresonant Harmonic Elimination Method for Detecting Zero Sequence Current Pulse Width

Abstract

The invention relates to a ferroresonance elimination method for detecting a zero-sequence current pulse width. The method comprises the following steps: determining whether a current transformer detects zero-sequence currents between a neutral point of an electromagnetic potential transformer and the ground; when it is detected that the zero-sequence currents reach preset zero-sequence currents, calculating the pulse width of the zero-sequence currents reaching preset pulse amplitude in first preset time; according to the pulse width of the zero-sequence currents, determining whether the electromagnetic potential transformer generates ferroresonance; and when the electromagnetic potential transformer generates the ferroresonance, controlling a first control switch connected in series with a resonance elimination resistor to be switched on, and performing resonance elimination processing on the electromagnetic potential transformer. Through the apparatus provided by the embodiments of the invention, the ferroresonance can be accurately and rapidly eliminated, and the resonance elimination efficiency of the ferroresonance is improved.

Description

technical field [0001] The invention relates to the technical field of power system safety prevention and control, in particular to a ferromagnetic resonance resonance elimination method for detecting zero-sequence current pulse width. Background technique [0002] In the distribution network below 66kV and below 66kV, a non-effective grounding system is usually adopted in which the neutral point of the system is not grounded and the neutral point is grounded through a small resistance or an arc suppression coil. The system bus is connected with an electromagnetic voltage for monitoring insulation to ground. Transformer (Potential Transformer, PT). Transient impacts caused by lightning strikes on the line, single-phase grounding, combined-air bus operation, drastic load changes, and secondary voltage-load switching may excite ferromagnetic resonance between the excitation reactance of the electromagnetic voltage transformer and the ground capacitance of the system . In rec...

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Problems solved by technology

[0004] However, the method of installing a resonance eliminator at the primary center point of the electromagnetic voltage transformer can prevent the ferromagnetic resonance between the three-phase voltage and the ground that is easily generated in the system, but for the power frequency resonance caused by disconnection The effect is poor, and it is easy to cause the voltage increase of the neutral point of the electromagnetic voltage transformer, the insulation breakdown of the end of the electromagnetic voltage transformer and other undesirable phenomena, causing the resonance eliminator to lose its function; adding a damping resistor will cause heat due to the damping resistor Affects the effect of harmonic elimination; using a microcomputer secondary resonance eliminator device, it is difficult to distinguish power frequency resonance due to the method of detecting zero-sequence voltage and three-phase voltage waveform, and there is a problem that the detection circuit and harmonic elimination circuit share or need to detect three-phase voltage

[0005] Therefore, adopting the above-mentioned existing harmonic elimination method will not only prolong the harmonic elimination time and increase the harmonic elimination cost, but also greatly affect the harmonic elimination efficiency, cause frequent damage to equipment, and pose a serious threat to the safe and stable operation of the power grid and equipment

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