Method for identifying magnetizing inrush current and external fault CT (current transformer) saturation based on waveform discontinuous characteristic
A technology of excitation inrush current and out-of-area fault, applied in the direction of measuring current/voltage, measuring device, instrument, etc., to achieve the effect of protecting safe and stable operation, ensuring safe and stable operation, and avoiding refusal or misoperation
Active Publication Date: 2011-04-06
STATE GRID ELECTRIC POWER RES INST
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When the transformer is in normal operation, there is no discontinuity in the differential current waveform
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The invention relates to a method for identifying magnetizing inrush current and external fault CT (current transformer) saturation based on waveform discontinuous characteristic, which comprises the following steps: 1) carrying out differential operation on current of a differential sample; 2) carrying out integration within s points on the current of the differential sample after differencing; 3) obtaining waveform discontinuous floating threshold values according to the current integral value; and 4) considering the internal fault characteristic and the non-magnetizing inrush current and external fault characteristic as preset threshold values if the criterion is established when lasting for T time. The method can avoid failure to operation or maloperation of a transformer protection device and protect the safe and stable operation of a power system.
Description
technical field The invention relates to a method for identifying excitation inrush current and CT saturation of external faults in differential protection of power system transformers, in particular to a method for identifying excitation inrush current and CT saturation of external faults based on waveform discontinuity characteristics. Background technique In order to ensure the safe operation of the transformer, it must be equipped with differential protection. The inrush current of the transformer and the CT saturation of the external fault have always been a major hidden danger of the maloperation of the differential protection of the transformer. So far, the ability to quickly and accurately distinguish the inrush current from the fault current has always been the key to the performance of transformer protection. Relay protection workers at home and abroad have done a lot of in-depth research on this, and put forward many effective methods from different angles. The ...
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IPC IPC(8): H02H7/045G01R19/00
Inventor 郑玉平刘小宝潘书燕侯喆姚刚
Owner STATE GRID ELECTRIC POWER RES INST