Fault line selection method for single-phase-to-ground fault in small ground current distribution network

Abstract

The invention relates to a small earth current grid single-phase grounding fault wire-choosing method, which comprises: 1) Collecting the zero order voltage and the zero order current signal on the voltage sensor and the current sensor of each wire and computing the zero order voltage amplitude, if the amplitude is over the limit, it quotes that it occurs the fault and collects the zero order current after four period of the fault; 2) computing the second, third and forth period effect value I1, I2 and I3 when each line zero order current fault starts and computing the gradient factor K1, K2 of each line zero order current; 3) quoting weather it satisfies K1ú¥KSET and K2ú¥KSET, wherein KSET is the gradient factor setting value with the range 1.2-2.0; 4) if it satisfies K1ú¥KSET and K2ú¥KSET, the wire is earth fault wire. The wire-choosing system comprises a microcomputer including a fault detecting open unit, a zero order current gradient computing unit and a transient gradient wire-choosing unit.

Description

(1) Technical field [0001] The invention belongs to the field of power systems, and relates to a line selection method and a line selection device for a single-phase ground fault in a small ground current grid. (2) Background technology [0002] At present, there are two main ways of grounding the neutral point of the medium-voltage power grid in China: the neutral point is not grounded and the neutral point is grounded through the arc suppression coil. The power grids of these two neutral point grounding methods are called small current grounding power grids. [0003] These two power grids have different characteristics when a line single-phase ground fault occurs. [0004] For ungrounded networks, see figure 1 , in the power grid where the neutral point is not grounded, the line has the following characteristics when a single-phase ground occurs: (1), the zero-sequence current of the non-fault line is 3I 0 The magnitude of is equal to the ground capacitance current of t...

AI Technical Summary

Problems solved by technology

[0023] In order to overcome the disadvantages of poor accuracy, low success rate of line selection and complex operation and maintenance of the line selection device in the prior art, the present invention provides a line selection method with simple operation and maintenance, good line selection accuracy, and Single-phase ground fault line selection method and line selection system for small ground current power grid with high success rate

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