CN101545944B

CN101545944B - Method for locating single-phase ground fault of a low current grounding system power distribution network

Info

Publication number: CN101545944B
Application number: CN200910116781XA
Authority: CN
Inventors: 赵海清; 赵杰
Original assignee: 合肥科盟电子科技有限责任公司
Priority date: 2009-05-14
Filing date: 2009-05-14
Publication date: 2012-11-07
Also published as: CN101545944A

Abstract

The present invention relates to a method for locating single-phase ground fault of a low current grounding system power distribution network, including determining a total length L[total] and a total impedance Z[total] between two lines of M and N, and injecting signals when occurring a fault, when a P point between the M and N positions occurring a single-phase ground fault, systems of the two positions inject signals at the M and N position, and measures the amplitude of a return current signal as well as a phase difference between the return current signal and the injection voltage signal, after a line selection device has selected the fault phase; calculating a loop total impedance Z[M] grounded through the P point from the M and N ends, the modulo of the Z[N], and a phase angle Phi[M] of the Z[M] and the Z[N], according to |Z| = |U| / |I|, the measured injection voltage, the amplitude of the return current signal and the phase difference, a distance from the fault point P to the M position is further calculated through the following formula. By the method of the invention, it is easy to detect when the signal amplitude is strong, the attrition in the power distribution network is low, the algorithm is high, and the accuracy is high.

Description

A kind of low current grounding system power distribution network method for locating single-phase ground fault

Technical field

The present invention relates to a kind of Fault Locating Method, be specifically related to a kind of low current grounding system power distribution network singlephase earth fault point method of location automatically that is used for.

Background technology

China 6～66kV distribution network adopts the small current neutral grounding system method of operation mostly.Singlephase earth fault is its topmost fault type.In case generation singlephase earth fault, traditional method are the artificial visually examines each bar branch road line walking is checked, wasted time and energy; And the operation of need operating a switch in a large number, normal operation of electrical network and productive life are brought very big inconvenience.Domestic localization method has following several kinds at present: traveling wave method: inject high-frequency row ripple at faulty line one end, the time and the velocity of wave that return from the trouble spot according to the row ripple calculate fault distance.Shortcoming is that high-frequency row ripple is very serious in the decay and the distortion of power distribution network, and the row wave head is difficult to identification, and bearing accuracy is not high.S injection method: utilize the phase voltage that is connected the automatic Monitoring Line of device on the PT, the back open-circuit line takes place and pass through the signal of PT injected frequency between power frequency n time and n+1 subharmonic at singlephase earth fault.Cooperate the hand-held current probe of people to survey the localization of faults along the line.This method needs the artificial line walking of hand-held detector, the location automatically of being unrealized.Impedance method: utilize the voltage and current amount of failure wave-recording equipment records fault moment, calculate the impedance of fault loop,, just can obtain fault distance because the circuit degree is directly proportional with impedance.The electric current and voltage amount that the record wave device recorded when shortcoming was fault is faint, is difficult to survey.Location algorithm need be separated iterative process, is prone to the situation that the result does not restrain or occur pseudo-root.And the algorithm of separating the differential equation is subject to the influence of transition resistance and system operation mode.Present method is all failed the automatic location of satisfied realization one-phase earthing failure in electric distribution network.

Summary of the invention

The present invention is directed to the deficiency of prior art, provide that a kind of signal amplitude is strong to be surveyed easily, in power distribution network loss low, and algorithm is simple, degree of accuracy is high is used for the low current grounding system power distribution network singlephase earth fault method of location automatically.

The present invention realizes through following technical scheme:

A kind of low current grounding system power distribution network method for locating single-phase ground fault comprises and confirms M, the total length L of N two places circuit _AlwaysWith resulting impedance Z _Always, and after fault takes place, inject signal, work as M; During P point generation singlephase earth fault in the middle of the N two places, route selection equipment select fault mutually after, the two places system is respectively at M; The N two places are carried out signal and are injected, and measure the amplitude of return current signal, with and with the phase differential of injecting voltage signal; According to | Z|=|U|/| I|, and the amplitude and the phase differential thereof of the injecting voltage that records, return current signal, calculate from M, the N two ends are through the loop resulting impedance Z of P point ground connection _M, Z _NMould and Z _M, Z _NPhase angle φ _M, φ _N, further calculate the distance of trouble spot P apart from M ground through following formula,

Wherein L _AlwaysAnd Z _AlwaysBe the preset parameter that measures, L ₁, L ₂Be respectively singlephase earth fault point P apart from circuit two ends M, the distance of N is positioning result.

A kind of low current grounding system power distribution network method for locating single-phase ground fault; After the faulty line both-end injects signal, measurement return signal; Change to inject the frequency of signal, remeasure return signal then, change many class frequencys after; Voltage under each frequency that obtains, current data are calculated fault distance respectively, and average.

A kind of low current grounding system power distribution network method for locating single-phase ground fault, respectively at M, the signal that the N two places are injected is that frequency is all between between n time of 50Hz and n+1 the multiple and less than the voltage signal of 1kHz.

A kind of low current grounding system power distribution network method for locating single-phase ground fault injects signal and arrives the earth through the ground connection transition resistance, turns back to M respectively through the earth, and the N decanting point forms the loop.

Beneficial effect of the present invention is following:

1. pass through amplitude and phase information in faulty line double-end measurement return signal, quantitative Analysis, the realization singlephase earth fault is located automatically;

2. adopt low frequency to inject signal, in power distribution network loss low, degree of accuracy is high.

3. through double-end measurement, on algorithm, offset the influence of transition resistance, position fixing process does not receive the influence of the size and the type of transition resistance;

4. this patent can be measured the both-end data respectively, does not need the both-end data sync, implements convenient, flexible.

5. computation process is simple, only relates to a trigonometric function operation and the computing of once extracting square root, and other is algebraic operation.Help realizing localization of fault fast and accurately.

The present invention can realize the automatic location of low current grounding system power distribution network singlephase earth fault; And algorithm simply, does not need the both-end data sync, not influenced by the size of transition resistance and type; Can practice thrift the time of malfunction elimination; Reduce the influence of fault, improve the reliability of operation of power networks productive life.

Embodiment

M, singlephase earth fault possibly take place in the distribution line between the N two places.The step of utilizing the said method of this patent to position is following:

1. confirm L _AlwaysAnd Z _Always: obtain M, N two places line length L through known line parameter circuit value _Always, and M, the resulting impedance Z of circuit between the N _AlwaysZ _AlwaysAlso can obtain: injecting voltage signal U on M ground through following method _i ^M, on N ground with the direct ground connection of metal.Inject signal and directly turn back to M ground, form the loop through the earth on N ground.Measure the return current I on M ground _CT ^M, and the phase differential of voltage and current According to | Z|=|U|/| I| in conjunction with the enlargement factor of PT, CT, can obtain | Z _Always|, and L _AlwaysAnd Z _AlwaysBe the required parameter of location Calculation, they are stored in the main frame of positioning system.

2. both-end voltage injects the measurement with return current: work as M, when singlephase earth fault takes place in the P point in the middle of the N, route selection equipment select fault mutually after, the two places system carries out signal injection and measurement respectively.Injected frequency is between between n time of 50Hz and n+1 the multiple, and less than the voltage signal U of 1kHz _i ^M, U _i ^N, measure return current signal I _CT ^M, I _CT ^NAmplitude, and U _i ^M, U _i ^NWith I _CT ^M, I _CT ^NPhase differential.After accomplishing the injection under the frequency and measuring, measurement data is stored in the main frame, utilize Single-chip Controlling DDS signal source to change several different frequencies and inject respectively and measure.

3. main frame calculates: communication module is responsible for issuing the other side to local measurement result.The main frame of two places is basis at first | Z|=|U|/| I|, In conjunction with the enlargement factor of PT, CT, obtain Z successively _M, Z _NMould and phase angle φ _M, φ _NThen after converging the other side's data, the L that obtains in conjunction with the first step _Always, Z _Always, according to formula (1)-(2), calculate the trouble spot, the distance of N two places apart from M.Calculate fault distance respectively and average according to the measurement data under a plurality of frequencies.Result of calculation is trouble spot P apart from the distance on M ground is x.

Claims

1. a low current grounding system power distribution network method for locating single-phase ground fault comprises and confirms M, the total length L of N two places circuit _AlwaysWith resulting impedance Z _Always, and after fault takes place, inject signal, it is characterized in that working as M; When singlephase earth fault takes place in the P point in the middle of the N two places; Route selection equipment select fault mutually after, the two places system is respectively at M, the N two places are carried out signal and are injected; And measure the amplitude of return current signal, with and with the phase differential of injecting voltage signal; According to | Z|=|U|/| I|, and the amplitude and the phase differential thereof of the injecting voltage that records, return current signal, calculate from M, the N two ends are through the loop resulting impedance Z of P point ground connection _M, Z _NMould and Z _M, Z _NPhase angle φ _M, φ _N, further calculate the distance of trouble spot P apart from M ground through following formula,

2. a kind of low current grounding system power distribution network method for locating single-phase ground fault according to claim 1; It is characterized in that after the faulty line both-end injects signal, measurement return signal; Change to inject the frequency of signal, remeasure return signal then, change many class frequencys after; Voltage under each frequency that obtains, current data are calculated fault distance respectively, and average.

3. a kind of low current grounding system power distribution network method for locating single-phase ground fault according to claim 1 and 2; It is characterized in that respectively that at M the signal that the N two places are injected is that frequency is all between between n time of 50Hz and n+1 the multiple and less than the voltage signal of 1kHz.

4. a kind of low current grounding system power distribution network method for locating single-phase ground fault according to claim 1 and 2 is characterized in that injecting signal and arrives the earth through the ground connection transition resistance, turns back to M respectively through the earth, and the N decanting point forms the loop.