Single-phase grounding line selection method for small-current grounding system

Abstract

The invention discloses a single-phase grounding line selection method for a small-current grounding system, and the method comprises the following steps: 1, collecting the zero sequence voltage of a bus or an outgoing line and the zero sequence current of the outgoing line, and calculating the amplitude of the zero sequence voltage in real time; 2, determining that the bus or the outgoing line has a single-phase grounding fault when the amplitude of the zero sequence voltage is greater than the amplitude of a line selection start voltage, and switching to step 3; 3, extracting the data of zero sequence current and voltage of a cycle before a moment when a fault happens and a cycle after the moment of the fault happens, and carrying out the wavelet packet transformation of the data of transient zero sequence voltage and current; 4, comparing the phases of the transient zero sequence current and voltage after the wavelet packet transformation: determining that a line is not a fault line if the phases are the same, and determining that the line is a fault line if the phases are opposite, thereby completing the grounding line section. The method solves a problem of a higher line selection misjudgment rate caused by that the phases and amplitudes of the zero sequence currents of the fault line and the non-fault line when a conventional arc suppression coil grounding system has a single-phase grounding fault.

Description

technical field [0001] The invention relates to a single-phase grounding line selection method for a small current grounding system. Background technique [0002] In my country's 3kV ~ 66kV power supply and distribution network, most of them adopt the neutral point non-direct grounding method, because when a ground fault occurs, the current flowing through the ground point is small, so it is often called a small current grounding system (NUGS) , which includes the neutral point ungrounded system (NUS), the neutral point through the arc suppression coil grounding system (NES, also known as the resonant grounding system) and the neutral point through the resistance grounding system (NRS). In recent years, with the widespread use of automatic tracking arc-suppression reactors, in order to solve the resonance problem of the system at the moment of failure, the operation mode of arc-suppression coils connected in series (or in parallel) with nonlinear resistors and in parallel wit...

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Problems solved by technology

[0005] In view of the above problems, the present invention provides a single-phase grounding line selection method for a small current grounding system, which solves the problem of the phase and amplitude of the zero-sequence current between the faulty line and the non-faulty line when a single-phase grounding fault occurs in the arc-suppression coil grounding system. The values ​​are relatively close, which leads to the problem of high misjudgment rate of line selection

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