Single-phase earth fault positioning method based on neutral point earth current starting

Abstract

The invention relates to a single-phase earth fault positioning method based on neutral point earth current starting. The measured current of a current transformer installed at a bus neutral point earth resistor of a transformer substation is introduced, namely neutral point earth current. Neutral point earth current is used as a single-phase earth fault break variable starting element. A bus neutral point earth current starting device records the neutral point earth current waveform at the sudden change moment T, and calls the three-phase current waveforms of all wide-area synchronous intelligent sensors installed along the outgoing line of the transformer substation at the same moment T. Fault positioning is realized on the bus neutral point earth current starting device by using wide-area synchronous information. The method aims to solve the problem of single-phase earth fault positioning in the existing power distribution network small-resistance earth system, and especially medium-resistance and high-resistance earth faults.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a single-phase ground fault location method based on neutral point ground current start. Background technique [0002] With the rapid development of the national economy, the scale of the power system is also growing, the network structure is becoming more and more complex, and users have higher and higher requirements for the stability of power supply, all of which require continuous upgrading of the power system , Avoid the occurrence of faults during the operation of the system. Even if a fault occurs, it is necessary to quickly and accurately find the location of the fault after the fault occurs, and then quickly eliminate the fault to ensure the safe operation of the power system and minimize the loss. [0003] Most distribution networks in my country generally adopt the low-current grounding method that the neutral point is not grounded or grounded through the arc suppr...

AI Technical Summary

Problems solved by technology

[0006] The fault indicators or sensors that are widely used in fault location are generally started based on electric field mutation or phase current mutation, but this method has major defects in principle, so the practical effect is not good. The main problems are:

[0007] 1) The starting element is unreasonable

[0008] The use of electric field mutation as the starting element of the ground fault, on the one hand, is easily disturbed by external factors (environment, climate, arrangement of overhead lines) and misoperation; more importantly, in the small resistance grounding mode, the electric field change of the grounding point exceeding 100ohm is extremely Weak, difficult to start fault judgment

[0009] The sudden change of phase current is used as the start-up element of the ground fault, and the start-up threshold is difficult to set

If the gate limit is high, it is difficult to start with medium and high resistance grounding; if the gate limit is low, false alarms will be frequently triggered due to line load or other disturbances, which is difficult for practical application

[0010] 2) The sampling frequency is too low

Without high-quality sampling data, it is easy to lead to misjudgment

[0012] 3) Synchronization accuracy is too low

If the synthetic zero-sequence current error caused by synchronization error is greater than the actual grounding zero-sequence current itself, it will inevitably lead to fault line selection and location errors!

[0014] 4) Most of the local signals are used, and the information is incomplete

If the sampling is not synchronized and the synchronization time error reaches several milliseconds, the calculated cross-correlation coefficient is completely invalid. At this time, the algorithm fails and the faulty section cannot be determined

At present, the synchronization accuracy between ordinary fault indicators or sensors is too low, which can only reach 10 milliseconds, and it is impossible to use this algorithm to realize fault location

Images