Ferroresonant Harmonic Elimination Method for Detecting the Consistency of Zero-Sequence Current Pulse Width

Abstract

The invention relates to a ferromagnetic resonance elimination method for detecting the pulse width uniformity of zero sequence current. The method comprises the following steps: judging whether a current transformer detects a zero sequence current between the neutral point of an electromagnetic voltage transformer and the ground; when detecting that the zero sequence current is greater than a preset zero sequence current, calculating the pulse width uniformity of a zero sequence current reaching a preset pulse amplitude in a first preset duration; judging whether ferromagnetic resonance occurs to the electromagnetic voltage transformer according to the pulse width uniformity of the zero sequence current; and when ferromagnetic resonance occurs to the electromagnetic voltage transformer, making a first control switch connected in series with a resonance elimination resistor closed, and eliminating resonance of the electromagnetic voltage transformer. With the device provided by the embodiment, ferromagnetic resonance can be eliminated accurately and quickly, and the efficiency of ferromagnetic resonance elimination can be 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 the consistency of 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 th...

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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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