CN111579925A

CN111579925A - Positive rail ground fault positioning method of fourth rail backflow traction power supply system

Info

Publication number: CN111579925A
Application number: CN202010436422.9A
Authority: CN
Inventors: 马庆安; 刘炜; 李鲲鹏; 潘卫国
Original assignee: Southwest Jiaotong University
Current assignee: Chengdu Shanghua Electric Co ltd
Priority date: 2020-05-21
Filing date: 2020-05-21
Publication date: 2020-08-25
Anticipated expiration: 2040-05-21
Also published as: CN111579925B

Abstract

The invention discloses a positive rail ground fault positioning method of a fourth rail backflow traction power supply system, which specifically comprises the following steps: the differential current is used to determine which power supply section the fault section is located in and the uplink or downlink of the section, and the fault location formula provided by the invention is used to determine the fault location. The invention is not influenced by traction load, and the unit resistances of the anode rail and the cathode rail can be different, thereby shortening the fault inspection time and improving the operation efficiency and the safety of the system.

Description

Positive rail ground fault positioning method of fourth rail backflow traction power supply system

Technical Field

The invention belongs to the field of fault diagnosis of urban rail transit traction power supply systems. In particular to a positive rail ground fault positioning method of a fourth rail backflow traction power supply system.

Background

The urban rail traction power supply system plays an important role in providing electric energy for trains. In order to reduce the corrosion of stray current to underground metal pipelines, part of urban rail traction power supply systems use a fourth rail backflow power supply mode. The urban rail traction power supply system can generate a positive rail ground fault, so that the related protection device acts and power supply interruption is caused. Due to the leakproofness of urban rail transit vehicles, a long-time power failure can cause difficulty in breathing and even loss of life of passengers. Therefore, when the urban rail traction power supply system has a ground fault, the power failure time should be reduced as much as possible. When a fault occurs, a maintenance person needs to patrol the line to remove the fault. Patrolling a route can take a considerable amount of time, affecting the operating efficiency and safety of the urban rail system.

Disclosure of Invention

In order to accurately give out the positions of a fault section and whether the fault is positioned in an uplink or downlink line and an anode rail ground fault, the fault inquiry time is conveniently shortened, and the operation efficiency and the reliability of the system are improved. The invention provides a method for positioning earth fault of an anode rail of an urban rail backflow traction power supply system.

The invention discloses a positive rail ground fault positioning method of a fourth rail backflow traction power supply system, which comprises the following steps of:

step 1: for the full-line power supply system, a power supply section is arranged between two adjacent traction substations; for the kth power supply section, the unit resistance z of the positive and negative rails and the through ground is input_P、z_NAnd z_GWAnd the length L of the section_k。

Step 2: setting a short-circuit current determination threshold I_th。

And step 3: for the uplink or downlink traction network of the section, measuring the current fed out by the traction substations on two sides to the anode rail and the cathode rail of the section and the voltage of the traction substations in real time: i is_Pk,iAnd I_Nk,iThe current is fed out from the traction substation k to the anode rail and the cathode rail of the row; i is_Pk+1,jAnd I_Nk+1,jThe current is fed out from the traction substation k +1 to the positive rail and the negative rail of the row; u shape_k,1And U_k+1,1The voltage of the positive electrode rails of the traction substation k and k +1 relative to the negative electrode rails is obtained; u shape_k,2And U_k+1,2The voltages of the traction network grounding leakage protection devices of the traction substations k and k + 1.

And 4, step 4: calculating the short-circuit current I of the power supply section k according to the formula (1)_kf

I_kf＝I_Pk,i-I_Nk,i+I_Pk+1,j-I_Nk+1,j(1)

And 5: determining whether I is satisfied_kf≥I_th(ii) a If yes, judging that the positive rail has a ground fault, and turning to the step 6; otherwise, judging that the positive rail is normal, and turning to the step 3.

Step 6: according to short-circuit test or simulation analysis, according to the formula (2)

Determining H when head end and tail end of fault section are short-circuited_k1And H_k2。

And 7: determining H in short circuit according to formula (2) based on voltage and current distribution in short circuit_k。

And 8: determining the location of the fault point relative to the head end of the section according to equation (3)

Compared with the prior art, the invention has the beneficial technical effects that:

(1) the method can definitely determine whether the fault is positioned on an uplink or a downlink, and give out the fault position, so that the fault position is not influenced by traction load, and the unit resistances of the positive rail and the negative rail can be different; the invention shortens the fault patrol time and improves the system operation efficiency and safety.

(2) Analysis shows that the fault location error is about 5% at most when the measurement error of the current transformer is not considered.

Drawings

FIG. 1 is a circuit diagram illustrating a fault location method (SS is traction substation, LD is traction load, f is positive rail short-circuit point, and a ground leakage protection device is arranged in a dotted line frame, wherein D is diode, and R is_eA ground leakage protection device series resistance).

FIG. 2 is a flow chart of the present invention.

Detailed Description

The implementation steps of the present invention are further described below with reference to the accompanying drawings.

The method comprises the steps of firstly determining whether the fault occurs, secondly determining a fault section and whether the fault is located in an uplink or a downlink, and finally determining the fault position.

1. Determination of occurrence of failure

The current of the earth leakage protection device is not influenced by the traction load, so that the earth leakage protection device is used as a criterion for judging whether the magnetic suspension power supply system has a fault or not. In actual engineering, a current threshold (1A can be taken) can be set. When the current is less than the threshold, the earth leakage protection device current is considered to be zero. When the current of the grounding leakage protection device of the full-line traction substation is zero, the system can be judged to operate normally; otherwise, the positive rail ground fault during system operation can be determined.

2. Determination of faulty section

The invention uses the deviation of the sum module value of the positive and negative pole rail currents to judge, can avoid the influence of traction load current, has accurate and reliable judging method, is not influenced by the traction load, but simultaneously requires to synchronously measure the current of each grounding leakage protection device and the current of a feeder line.

The principle of the fault section determination is explained below in conjunction with fig. 1. For the power supply section between SS3 and SS4 in FIG. 1, the sum of the positive and negative rail currents is calculated

Because the up positive rail of the section has a ground fault, there are

The deviation of the sum module value of the current of the uplink positive and negative electrode rails is

And the deviation of the sum module value of the current of the descending positive and negative electrode rails is

It can be determined that the upper positive rail in the sector has a ground fault.

For the power supply section between SS1 and SS2 and the power supply section between SS1 and SS2, the deviation of the sum modulus of the positive and negative rail currents is 0 because no ground fault occurs.

If the fault occurs in the power supply section with traction load, the correct judgment can be made for the fault section and the fault line.

3. Flow chart of fault location

A flow chart for fault location is shown in fig. 2. The method specifically comprises the following steps:

(1) for the full-line power supply system, a power supply section is arranged between two adjacent traction substations; for the kth power supply section, the unit resistance z of the positive and negative rails and the through ground is input_P、z_NAnd z_GWAnd the length L of the section_k。

(2) Setting a short-circuit current determination threshold I_th。

(3) For the uplink or downlink traction network of the section, measuring the current fed out by the traction substations on two sides to the anode rail and the cathode rail of the section and the voltage of the traction substations in real time: i is_Pk,iAnd I_Nk,iThe current is fed out from the traction substation k to the anode rail and the cathode rail of the row; i is_Pk+1,jAnd I_Nk+1,jThe current is fed out from the traction substation k +1 to the positive rail and the negative rail of the row; u shape_k,1And U_k+1,1The voltage of the positive electrode rails of the traction substation k and k +1 relative to the negative electrode rails is obtained; u shape_k,2And U_k+1,2The voltages of the traction network grounding leakage protection devices of the traction substations k and k + 1.

(4) Calculating the short-circuit current I of the power supply section k according to the formula (1)_kf

I_kf＝I_Pk,i-I_Nk,i+I_Pk+1,j-I_Nk+1,j(1)

(5) Determining whether I is satisfied_kf≥I_th(ii) a If yes, judging that the positive rail has a ground fault, and turning to the step 6; otherwise, judging that the positive rail is normal, and turning to the step 3;

(6) according to short-circuit test or simulation analysis, according to the formula (2)

Determining H when head end and tail end of fault section are short-circuited_k1And H_k2. Wherein the head end is H_k1And terminal is H_k2。

(7) Determining H in short circuit according to formula (2) based on voltage and current distribution in short circuit_k。

(8) Determining the position of the fault point relative to the head end of the section according to formula (3) by adopting a linear interpolation method

Claims

1. A positive rail ground fault positioning method of a fourth rail backflow traction power supply system is characterized by comprising the following steps:

step 1: for the full-line power supply system, a power supply section is arranged between two adjacent traction substations; for the kth power supply section, the unit resistance z of the positive and negative rails and the through ground is input_P、z_NAnd z_GWAnd the length L of the section_k；

Step 2: setting a short-circuit current determination threshold I_th；

And step 3: for the uplink or downlink traction network of the section, measuring the current fed out by the traction substations on two sides to the anode rail and the cathode rail of the section and the voltage of the traction substations in real time: i is_Pk,iAnd I_Nk,iThe current is fed out from the traction substation k to the anode rail and the cathode rail of the row; i is_Pk+1,jAnd I_Nk+1,jThe current is fed out from the traction substation k +1 to the positive rail and the negative rail of the row; u shape_k,1And U_k+1,1The voltage of the positive electrode rails of the traction substation k and k +1 relative to the negative electrode rails is obtained; u shape_k,2And U_k+1,2The voltage of the traction network grounding leakage protection device of the traction substation k and k + 1;

and 4, step 4: push buttonFormula (1) calculates short-circuit current I of power supply section k_kf

I_kf＝I_Pk,i-I_Nk,i+I_Pk+1,j-I_Nk+1,j(1)

And 5: determining whether I is satisfied_kf≥I_th(ii) a If yes, judging that the positive rail has a ground fault, and turning to the step 6; otherwise, judging that the positive rail is normal, and turning to the step 3;

Determining H when head end and tail end of fault section are short-circuited_k1And H_k2；

And 7: determining H in short circuit according to formula (2) based on voltage and current distribution in short circuit_k；

And 8: the position of the fault point relative to the head end of the section is determined according to the formula (3),