Test simulation method for failure line selection of small current ground system

Abstract

The invention relates to a measuring post simulation method of the fault wire selection for a low current grounding system. The invention belongs to the technical field of the power system relay protection. The method is realized by that when the instantaneous value of the voltage of a bus zero exceeds the limit, a fault wire selection device is started immediately and used for recording the wave.The invention adopts a digital filter algorithm to obtain the bus zero voltage and the transient pure fault components of zero current on each feedback line. When a low current grounding system takesplace a single-phase earth fault, the waveform of the zero current is quantitatively solved by using measuring post simulation according to the transient pure fault component of the measured value ofthe bus zero voltage and the feeder zero distribution capacitor parameter under the assumption premise of the perfect feeder of every feeder. The invention carries out correlativity analysis to compare the measured waveform of the current of every zero current with the transient pure fault component solved by the measuring simulation method under a definite data window and calculate both correlative coefficients, thereby the invention forms a line selecting criterion 1 and 2 and can carry out line selection to the system according to the line selecting criterion. The principle analysis and the simulation show that the line selection method has the advantages of accuracy and reliability.

Description

Technical field: [0001] The invention relates to a post-test simulation method for fault line selection of a small current grounding system, and belongs to the technical field of power system relay protection. Background technique: [0002] The neutral point non-effective grounding system where the single-phase grounding arc can be extinguished by itself is called the small current grounding system (also known as the small grounding current system), and the neutral point is not grounded, grounded through high resistance, or grounded through the arc suppression coil. The form appears. my country's 6-66kV distribution network is usually a small current grounding system. [0003] Operation and research have shown that the main reasons why the single-phase grounding line selection problem of low-current grounding system is difficult to solve is: (1) The fault boundary is too complicated and random, and it is difficult to describe with a single statistical model. (2) The steady-state ...

AI Technical Summary

Problems solved by technology

Because the zero-sequence current is obtained through a phase-sequence filter composed of three single-phase current transformers, the iron cores of each mutual inductor cannot be exactly the same, so there is a zero-sequence current error

In addition, the variable ratio of the current transformer is large, and the iron core is nonlinear, which will affect the line selection

The consistency of current transformers is poor; in practical applications, the saturation of current transformers in medium and low voltage power grids occurs from time to time

(4) For the resonant grounding system, although the integration of line selection and automatic compensation device is a promising solution, the automatic compensation device has been installed on site, so it is still necessary to study the line selection protection technology with independent functions

(5) A series of problems of sensitive start-up and line selection reliability still need to be solved

(6) Various methods have limitations, and it is difficult to find a universal method. How to solve the problem of effective fusion of multiple line selection criteria is also an important problem

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