CN110609216B

CN110609216B - A method for locating faults of EMU cable terminals

Info

Publication number: CN110609216B
Application number: CN201911062565.1A
Authority: CN
Inventors: 周利军; 邢立勐; 杨涵; 曹伟东; 张靖康; 权圣威
Original assignee: Southwest Jiaotong University
Current assignee: Shangdong Cable Co ltd
Priority date: 2019-11-03
Filing date: 2019-11-03
Publication date: 2021-04-13
Anticipated expiration: 2039-11-03
Also published as: CN110609216A

Abstract

The invention discloses a fault location method for a cable terminal of an EMU, comprising the steps of: EPR cable terminal simulation modeling, respectively calculating the electric field strength at the truncated layer of the cable terminal model, establishing a functional relationship between the air gap position and the electric field strength of the truncated layer, and defects. Theoretical position determination and position error correction. The beneficial effect of the invention is that the fault area and fault position of the EPR cable terminal can be located accurately and efficiently, and the maintenance workload is greatly reduced.

Description

Motor train unit cable terminal fault positioning method

Technical Field

The invention belongs to the field of fault processing of vehicle-mounted EPR cable terminals of motor train units, and particularly relates to a fault positioning method of a motor train unit cable terminal.

Background

The EPR cable in long-term operation of the motor train unit bears great mechanical stress due to movement, particularly a fragile cable terminal is easy to damage due to the mechanical stress, and uncertain factors such as severe surrounding environment, overlong operation time at high temperature and the like aggravate the defect degree of a damaged part, so that partial discharge is easily generated at the cable terminal, the cable terminal is broken down, and the safe and reliable operation of the motor train unit is threatened. When the cable terminal has a fault, if the fault area can be effectively positioned, the workload of maintainers can be greatly reduced, the outage time of the motor train unit due to the fault is shortened, and the economic benefit is improved.

However, at present, effective methods for intelligently positioning cable terminals and correcting position errors at home and abroad are few, so that a method for intelligently positioning faults and correcting position errors of a cable terminal of a motor train unit is urgently needed for accurately positioning fault positions and reducing unnecessary economic loss.

Disclosure of Invention

The invention discloses a method for intelligently positioning and correcting a fault area of a vehicle-mounted EPR cable terminal running for a long time, which comprises the following steps of:

a method for positioning a fault of a cable terminal of a motor train unit comprises

Step 1: EPR cable terminal simulation modeling:

according to the on-vehicle EPR cable termination of operating condition 1: 1, establishing n cable terminal simulation models containing air gap defects from an outer semiconductor truncation layer to a copper terminal, wherein the distance from the air gap defect position on each model to the truncation layer is increased by the gradient of h, namely the distance from the air gap defect of the No. 1 cable terminal model to the truncation layer x₁Air gap defect distance truncation layer x of No. 0 and No. 2 cable terminal model₂H, n cable termination model air gap defect distance truncation layer x_nH (n-1), n position sets are X,

X＝{x_n|x_n＝h(n-1),n≥1,n∈N⁺} (1)

step 2: respectively calculating the electric field intensity at the truncation layer of the No. 1 to the No. n cable terminal models:

note that the electric field intensity at the cut-off layer of the cable terminal simulation model No. 1 is E₁And the electric field intensity at the truncation layer of the No. 2 cable terminal simulation model is E₂And the electric field intensity at the truncation layer of the No. 3 cable terminal simulation model is E₃…, the electric field intensity at the truncation layer of the n cable terminal simulation model is E_nThe n sets of electric field strengths are E,

E＝{E₁，E₂，E₃，...,E_n} (2)

and step 3: establishing a functional relation between the air gap position x and the electric field intensity E of the truncation layer:

fitting a general function expression of the air gap position x and the truncation layer electric field intensity E, and fitting according to the formulas (1) and (2):

and 4, step 4: determining the theoretical position of the defect:

the electric field intensity tester is used for detecting the electric field intensity E at the outer sheath of the upper layer of the EPR cable terminal interception layer with an unknown position containing air gap defects₀Calculating the electric field intensity E at the cut-off layer_δ，

Wherein epsilon₀、ε₁、ε₂And ε₃The dielectric constants of the cable terminal outer sheath, the stress tube, the outer semi-conducting layer and the EPR insulating material are respectively; r is₀、r₁、r₂、r₃And r₄Respectively forming the radius of the outer wall of the outer sheath, the radius of the interface between the inner wall of the outer sheath and the stress tube, the radius of the interface between the inner wall of the stress tube and the outer semi-conductive layer, the radius of the interface between the inner wall of the outer semi-conductive layer and the EPR insulating outer wall and the inner diameter of the EPR insulating layer; u is the electromotive force on the cable core, gamma₀And gamma₁Conductivity of the outer semiconductive layer and EPR insulation, respectively; the electric field intensity E of the cut-off layer is equal to E_δSubstituting the formula (4) to calculate the position x of the air gap defect₀；

And 5: and (3) correcting the position error:

error correction of air gap defect location

Determining the air gap defect position range as follows:

the method has the advantages that the fault area and the fault position of the EPR cable terminal can be accurately and efficiently positioned, and the overhauling workload is greatly reduced.

Drawings

FIG. 1 is a flow chart of the present invention.

Detailed Description

The present invention will be further described with reference to the following examples.

Referring to fig. 1, the method comprises the following specific steps:

step 1: EPR cable terminal simulation modeling

According to the on-vehicle EPR cable termination of operating condition 1: 1, establishing 25 cable terminal simulation models containing air gap defects from an outer semiconductor truncation layer to a copper terminal, wherein the distance from the air gap defect position on each model to the truncation layer is increased by a gradient of 10mm, namely the air gap defect of the No. 1 cable terminal model is x from the truncation layer₁0mm, 2 # cable terminal model air gap defect distance truncation layer x₂No. i cable termination model air gap defect distance truncation layer x of 10mm_iThe same holds true for 10(i-1) mm, and so on, and the model of No. 25 cable terminal is far away from the truncation layer x₂₅240 mm; the 25 position set X is, in units: mm;

X＝{x|x＝10(i-1),1≤i≤25,i∈N⁺}＝{0,10,20,...,230,240} (1)

step 2: respectively calculating the electric field intensity at the truncation layer of the No. 1 to No. 25 cable terminal simulation end model

Calculating the electric field intensity at the truncation layer of the No. 1 to No. 25 cable terminal simulation models, and recording the electric field intensity at the truncation layer of the No. 1 cable terminal simulation model as E₁And the electric field intensity at the truncation layer of the No. 2 cable terminal simulation model is E₂And the electric field intensity at the truncation layer of the No. 3 cable terminal simulation model is E₃And the electric field intensity at the truncation layer of the I cable terminal simulation model is E_iAnd by analogy, the electric field intensity at the truncation layer of the No. 25 cable terminal simulation model is E₂₅The 25 electric field intensity sets E are, in units: v/m:

E＝{E₁，E₂，E₃，...,E_i，E₂₅} (2)

and step 3: fitting functional relation between air gap position x and electric field intensity E at truncation layer based on simulation model

And 4, step 4: theoretical defect location determination

Detecting the electric field intensity E at the outer sheath of the upper layer of the EPR cable terminal interception layer at the unknown air gap defect position by using an electric field intensity tester₀Calculating the electric field intensity E at the cut-off layer_δ

In the formula (4), epsilon₀、ε₁、ε₂And ε₃The dielectric constants of the cable terminal outer sheath, the stress tube, the outer semi-conducting layer and the EPR insulating material are respectively; r is₀、r₁、r₂、r₃And r₄Respectively representing the radius of the outer wall of the outer sheath, the radius of the interface between the inner wall of the outer sheath and the stress tube, the radius of the interface between the inner wall of the stress tube and the outer semi-conductive layer, the radius of the interface between the inner wall of the outer semi-conductive layer and the EPR insulating outer wall and the inner diameter of the EPR insulating layer; u is the electromotive force on the cable core, gamma₀And gamma₁Conductivity of the outer semiconductive layer and EPR insulation, respectively; will E_δSubstituting the formula (4), and calculating to obtain the air gap position x₀；

And 5: position error correction

Error correction of air gap defect location

The range of the air gap position can be determined

Unit: mm. (6)

Claims

1. a method for locating faults in cable terminals of an EMU, is characterized in that, comprising

Step 1: EPR cable termination simulation modeling:

According to the actual working conditions of the vehicle-mounted EPR cable terminal 1:1, n simulation models of cable terminals with air gap defects are established. From the outer semiconductor truncation layer to the copper terminal, the distance from the air gap defect position on each model to the truncation layer is h The gradient increases, that is, the distance from the air gap defect of the No. 1 cable terminal model to the cut-off layer x ₁ =0, the distance of the air gap defect of the No. 2 cable terminal model to the cut-off layer x ₂ =h, and the distance of the air gap defect of the No. n cable terminal model to the cut-off layer x _n =h(n-1), the set of n positions is X,

X={x _n |x _n =h(n-1),n≥1,n∈N ⁺ } (1)

Step 2: Calculate the electric field intensity at the truncation layer of the No. 1 to n cable terminal models respectively, mark the electric field intensity at the truncation layer of the No. 1 cable terminal simulation model as E ₁ , and denote the electric field intensity at the truncation layer of the No. 2 cable terminal simulation model as E The electric field intensity at the truncation layer of the simulation model of No. ₂ and No. 3 cable terminals is E ₃ , ..., the electric field intensity at the truncation layer of the simulation model of the n cable terminal is E _n , and the set of n electric field intensities is E,

E={E ₁ , E ₂ , E ₃ , ..., E _n } (2)

Step 3: Establish the functional relationship between the air gap position x and the electric field strength E of the truncation layer:

The general function expression of the fitted air gap position x and the electric field strength E of the truncation layer is obtained by fitting according to equations (1) and (2):

Step 4: Determination of the theoretical location of defects:

Use an electric field strength tester to detect the electric field strength at the outer sheath of the upper layer of the truncation layer of an EPR cable terminal with an air gap defect at an unknown position as E ₀ , and calculate the electric field strength E _δ at the truncation layer,

Among them, ε ₀ , ε ₁ , ε ₂ and ε ₃ are the dielectric constants of the cable terminal outer sheath, stress tube, outer semiconducting layer and EPR insulating material, respectively; r ₀ , r ₁ , r ₂ , r ₃ and r ₄ are the radius of the outer wall of the outer sheath, the radius of the interface between the inner wall of the outer sheath and the stress tube, the radius of the interface between the inner wall of the stress tube and the outer semiconducting layer, the radius of the interface between the inner wall of the outer semiconducting layer and the outer wall of the EPR insulating layer, and the inner diameter of the EPR insulating layer; U is the cable The electromotive force on the core, γ ₀ and γ ₁ are the electrical conductivity of the outer semiconducting layer and the EPR insulation, respectively; the electric field strength of the truncation layer E=E _δ is brought into the formula (4), and the position x ₀ of the air gap defect is calculated;

Step 5: Position Error Correction:

Error correction for air gap defect locations

Determine the location range of the air gap defect as: