Detection method of zero sequence current mutual inductor of small current system

Abstract

The invention discloses a detection method of a zero sequence current mutual inductor of a small current system, relates to a detection method of a current mutual inductor and in particular relates to a detection method of a zero sequence current mutual inductor of a small current system. According to the invention, a high-frequency current signal is injected into a secondary side for protecting the current mutual inductor, and a self-adaptive sine digital filter is used for extracting signals, so that the following major difficulties are solved: when the system is normally operated, the primary side of the system has a high voltage, so that the zero sequence current mutual inductor cannot get an exciting current directly through the primary side and the injected signal is submerged due to unbalance of a power frequency current; and the detection method can be used for detecting the zero sequence current mutual inductor under an uninterrupted power condition.

Description

technical field [0001] The invention relates to a detection method of a current transformer, in particular to a detection method of a zero-sequence current transformer in a small current system. Background technique [0002] In the distribution network, the zero-sequence current transformer is an important device that reflects the grounding fault. The direction of the current in the AC circuit changes with time. The polarity of the current transformer refers to the primary side current and the secondary side current at a certain moment. The current direction of a certain end is positive or negative at the same time, and this polarity is also called the end of the same name or the end of the same polarity. The primary side of the zero-sequence current transformer is the sum of the three-phase currents of the cable. The correctness of the zero-sequence current transformer Sexuality refers to the correct correspondence between the zero-sequence current transformer and the cable...

AI Technical Summary

Problems solved by technology

[0003] The polarity and correctness of the zero-sequence current transformer directly determine whether the grounding line selection device can operate correctly and whether the line can be selected correctly, so the polarity of the zero-sequence current transformer must be checked before installing the grounding line selection device and protection device. The current zero-sequence current transformer polarity and correctness detection method is to verify the polarity and correctness of the zero-sequence current transformer in the event of a power outage in the system. With the power supply reliability With the improvement of requirements and the repeated reduction of blackout plans, the polarity and correctness of the zero-sequence current transformer for blackout detection will not only cause blackout losses, but also be difficult to carry out

When the system is running normally, since the primary side of the system carries high voltage, it is impossible to directly pass the primary side to make the zero-sequence current transformer carry the excitation current, and the imbalance of the power frequency current will overwhelm the injected signal

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