CN105676079A

CN105676079A - Cable partial discharge source positioning method based on online decision rule

Info

Publication number: CN105676079A
Application number: CN201510960848.3A
Authority: CN
Inventors: 夏向阳; 杜荣林; 杨超; 黄润知; 贺运九
Original assignee: Changsha University of Science and Technology
Current assignee: Changsha University of Science and Technology
Priority date: 2015-12-18
Filing date: 2015-12-18
Publication date: 2016-06-15
Anticipated expiration: 2035-12-18
Also published as: CN105676079B

Abstract

The invention discloses a cable partial discharge (PD) source positioning method based on an online decision rule. The cable partial discharge source positioning method is used for positioning a single PD source or double PD sources in a single-core cable network. The cable partial discharge source positioning method comprises the steps of: selecting PD signal energy after wavelet transformation as a signal feature, and acquiring energy distribution conditions of cable joints according to the signal feature; performing real-time monitoring on temperature of all the joints to obtain temperature distribution conditions of the cable joints; and performing comprehensive analysis on the acquired energy distribution and temperature variation situations of the joints by utilizing a three-dimensional coordinate system, and directly determining a position segment of the PD source according to the online decision rule. The cable partial discharge source positioning method is general enough for positioning the single PD source or the double PD sources without establishing a special database nor considering characteristics (defect size, thickness and insulation position) of the PD source as well as relevant parameters of the cable network. Even if the cable partial discharge source positioning method is only suitable for positioning the single PD source or double PD source cable segment, the accuracy is high, and synchronous measurement of the cable network is not needed.

Description

Cable local discharge source location based on on-line decision rule

Technical field

The present invention relates to a kind of localization method to Partial Discharge Sources in cable system, belong to technical field of electric power.

Background technology

In the installation process of cable system, particularly medium and high pressure cable system, its Condition assessment of insulation becomes more and more important. Its running status of assessment is not only in insulation assessment in cable system, and needs assessment does not have the signal of telecommunication of clear index, and such as shelf depreciation (PD), it is to be produced by defect and will little by little destroy the dielectric level of cable. In addition PD will also result in cable intermediate joint heating, and monitoring Joint Temperature situation is also the Consideration of Condition assessment of insulation in real time. The detection of PD phenomenon mainly has two states appraisal procedure: online and off-line. And supervisor is interested in online method, but the impact of some factors can be subject at line method, including the melange effect in multiple PD sources, the sensor impact on measuring the impact of signal, partial discharge pulse propagates and reflects in noise, the interference of outer partial discharge source, 1 cut cable or multiple cut cable.

In order to research and solve these problems at line method, the task that cable system first has to do is PD source location, this location is not carry out being accurately positioned of PD source for a certain section of cable, but the cut cable that whole cable system exists PD source positions. At present, most of PD source location methods contribute to the location in single PD source in individual cable section, also the less situation that can consider multiple PD source. Therefore, find the localization method in single PD source or double; two PD source in cable system the state estimation tool of cable is of great significance.

Summary of the invention

In order to position single PD source in two sides earth single-core cable network or double; two PD source, the present invention proposes a kind of Partial Discharge Sources localization method based on on-line decision rule. It is signal characteristic that the method chooses the PD signal energy after wavelet transformation, obtains the Energy distribution situation at each cable connector place according to this feature; And the temperature of all joints is monitored in real time, obtain the profiling temperatures at the cable connector place that PD phenomenon causes.Then according to on-line decision rule, cable connector place Energy distribution and temperature variations are comprehensively analyzed, directly determine the position section in PD source.

Technical scheme provided by the invention is as follows:

Described cable system, it is assumed that total m cable connector, Mk represents joint, is divided into m-1 section, and E represents the energy value at cable connector place, and T represents the temperature value at cable connector place. The current signal of each joint is recorded particular by High Frequency Current Sensor (HFCT), signal energy feature is extracted through wavelet transformation, obtain the Energy distribution situation of whole each joint of cable system, measured the temperature variations of each joint simultaneously by temperature sensor. Two end connectors of Partial Discharge Sources place cut cable have higher signal energy and temperature compared to other joints, and single PD source is considered insulation defect and two kinds of situations of transient fault, and during transient fault, connector temperature raises only small.

After the Energy distribution obtaining joint and profiling temperatures, in order to apply online decision rules, first PD source single in cable system or double; two PD source are likely to place cut cable classify, 4 kinds of situations can be divided into: 1. two PD cut cables (centre is more than 1 normal reach) relatively far apart 2. two PD cut cables are separated by relatively near (only every 1 normal reach) 3. two PD cut cables adjacent 4. only 1 PD cut cables (insulation defect section or transient fault section).

Above 4 kinds of situations are listed decision rules:

1 (two PD cut cables are relatively far apart) of rule: if the energy indexes at two pairs of separating joint places exists higher value, joint is Mn, Mn+1, Mj and Mj+1, the temperature T of corresponding joint also has rising in various degree simultaneously, then cable system n-(n+1) section and j-(j+1) section are double; two places, PD source cut cable. Otherwise use next rule.

2 (two PD cut cables are separated by nearer) of rule: if the energy indexes two pairs of adjacent joints exists higher value, joint is Mn, Mn+1, Mn+2, Mn+3, the temperature T of corresponding joint also has rising in various degree simultaneously, then cable system n-(n+1) section and place, (n+2)-(n+3) Duan Weishuan PD source cut cable. Otherwise use next rule.

Rule 3 (two PD cut cables are adjacent): if only there is higher value at the energy indexes of 3 adjacent joints, joint is n, n+1, n+2, the temperature T of corresponding joint also has rising in various degree simultaneously, then cable system n-(n+1) section and place, (n+1)-(n+2) Duan Weishuan PD source cut cable. Otherwise use next rule.

Rule 4 (single PD cut cable): if only there is higher value at the energy indexes of 1 pair of adjacent joint, piece-ups are n, n+1, the temperature T of corresponding joint also has rising in various degree simultaneously, then cable system n-(n+1) section is defective cable section; The temperature T of corresponding joint only has minimum rising simultaneously, then cable system n-(n+1) section is transient fault cut cable.

Single PD source, application the method location or place, double; two PD source cut cable, have enough versatilities, do not need to set up special data base, without the relevant parameter of the characteristic (flaw size, thickness and position) and cable system that consider PD source. Even if the method is only applicable to the location of single PD source or double; two PD source power cable section, but its accuracy is significantly high, it is not necessary to cable system is carried out synchro measure.

Accompanying drawing explanation

Fig. 1 is cable system benchmark model

Fig. 2 (1) and 2 (2) is double; two PD source and normal condition for the signal energy at cable connector place under three-dimensional system of coordinate and temperature conditions schematic diagram wherein Fig. 2 (1), and Fig. 2 (2) is single PD source situation (contrast of insulation defect and transient fault)

Fig. 3 is the flow chart applying PD source, online decision rules location

Detailed description of the invention

Below in conjunction with accompanying drawing and specific implementation process, the invention will be further described.

Referring to Fig. 1, single-core cable grid reference model, as it can be seen, set total m cable connector, is divided into m-1 cut cable and every section of cable two sides earth. Being applied voltage by transformer station to cable system two ends makes cable system run, High Frequency Current Sensor and temperature sensor are installed at every section of cable connector place, the current signal detected is carried out wavelet transform process, signal energy feature after treatment obtains Energy distribution situation, monitors the situation of change of temperature in real time simultaneously. Wherein the morther wavelet of wavelet transformation elects db7 as, and signal characteristic chooses the energy content of the 9th decomposition level, because it is only small by noise effect.

Energy and temperature conditions to above-mentioned gained are analyzed, referring to Fig. 2, this figure is the signal energy at cable connector place and temperature conditions schematic diagram under three-dimensional system of coordinate, and wherein Fig. 2 (1) is double; two PD sources and normal joint situation, and Fig. 2 (2) is single PD source situation. Fig. 2 (1) can draw, occurs two end connectors of PD cut cable to have higher energy, and temperature changes in higher range; Normal joint energy is very low, and temperature is maintained at normal value. When Fig. 2 (2) can draw existence list PD source, joint energy is higher, if temperature is also higher, is then the PD owing to cable built-in electrical insulation defect causes; If temperature raises minimum, then it is the PD owing to transient fault causes. This is because transient fault time-continuing process is very of short duration just at insulating inner generation self-cleaning, and joint temperature could not be caused to have greatly changed.

Analysis according to joint Energy distribution and profiling temperatures, referring to Fig. 3, application institute extracting method carries out PD source location. Detailed process is: first find out the joint higher compared to other joint energy, and comprehensive corresponding joints temperature conditions, meet rule 1, then cable system n-(n+1) section and j-(j+1) section are double; two PD source power cable section, otherwise carry out rule 2; Meet rule 2, then cable system n-(n+1) section and (n+2)-(n+3) Duan Weishuan PD source power cable section, otherwise carry out then 3; Meet rule 3, then cable system n-(n+1) section and (n+1)-(n+2) Duan Weishuan PD source power cable section, otherwise carry out rule 4; Meet rule 4, then cable system n-(n+1) section is single PD source power cable section, if connector temperature is higher, then the PD caused for insulation defect; If connector temperature rises seldom, then the PD caused for transient fault.

Claims

1. the cable local discharge source location method based on on-line decision rule, it is characterised in that for positioning single PD source in single-core cable network or double; two PD source. It is signal characteristic that the method chooses the PD signal energy after wavelet transformation, obtains the Energy distribution situation at each cable connector place according to this feature; And the temperature of all joints is monitored in real time, obtain the profiling temperatures at the cable connector place that PD phenomenon causes. Use three-dimensional system of coordinate that joint Energy distribution and the temperature variations of gained are comprehensively analyzed, further in accordance with the flow process of on-line decision rule, directly determine the position section in PD source.

2. cable system according to claim 1, it is characterized in that, it is a kind of single-core cable, and every section of cable both passes through two sides earth, assuming total m cable connector, Mk represents concrete joint, is divided into m-1 cut cable, E represents the energy value at cable connector place, and T represents the temperature value at cable connector place. Record the current signal of each joint particular by High Frequency Current Sensor (HFCT), and then obtain energy value, and measured the temperature value of each joint by temperature sensor.

3. single PD source according to claim 1 or the combination of double; two PD source, it is characterized in that there are 4 kinds of situations: 1. two PD cut cables (centre is more than 1 normal reach) relatively far apart 2. two PD cut cables are separated by relatively near (only every 1 normal reach) 3. two PD cut cables adjacent 4. only 1 PD cut cables.

4. on-line decision according to claim 1 rule, it is characterised in that

1 (two PD cut cables are relatively far apart) of rule: if the energy indexes at two pairs of separating joint places exists higher value, joint is Mn, Mn+1, Mj and Mj+1, the temperature T of corresponding joint also has rising in various degree simultaneously, then cable system n-(n+1) section and j-(j+1) section are double; two places, PD source cut cable.

2 (two PD cut cables are separated by nearer) of rule: if the energy indexes two pairs of adjacent joints exists higher value, joint is Mn, Mn+1, Mn+2, Mn+3, the temperature T of corresponding joint also has rising in various degree simultaneously, then cable system n-(n+1) section and place, (n+2)-(n+3) Duan Weishuan PD source cut cable.

Rule 3 (two PD cut cables are adjacent): if only there is higher value at the energy indexes of 3 adjacent joints, joint is n, n+1, n+2, the temperature T of corresponding joint also has rising in various degree simultaneously, then cable system n-(n+1) section and place, (n+1)-(n+2) Duan Weishuan PD source cut cable.

5. PD signal characteristic according to claim 1, it is characterised in that PD signal is through wavelet transform process, and morther wavelet elects db7 as, and the energy content extracting the 9th decomposition level is PD signal characteristic.