CN103558533B - Based on insulation ag(e)ing diagnostic system and the method for 10kV XLPE cable - Google Patents

Abstract

The present invention relates to a 10kV? Insulation aging diagnosis system and method for XLPE cables, the system includes water-containing tree 10kV? XLPE cable, DC power supply, high-voltage pulse power supply and data acquisition and processing unit; the method includes the following steps: (1) 10kV for water-bearing trees? Apply a negative DC voltage V _dc to the XLPE cable; (2) Ground the high voltage side of the cable, and the trapped charge will become residual charge during the ground discharge process; (3) 10kV to the water-bearing tree? The XLPE cable applies a high-voltage pulse voltage, and at the same time collects the DC component signal of the voltage on the resistor R through the data acquisition and processing unit, and performs a time integral operation to obtain the residual charge; (4) judge the water tree aging degree of the cable according to the residual charge. The invention can better detect the aging degree of water trees, has obvious detection effect, and can effectively prevent the occurrence of insulation accidents.

Description

Insulation Aging Diagnosis System and Method Based on 10kV XLPE Cable

technical field

The invention belongs to the technical field of insulation aging analysis and diagnosis of cross-linked polyethylene cables, in particular to an insulation aging diagnosis system and method based on 10kVXLPE cables.

Background technique

The degree of cableization of urban power grid is an important symbol to measure the technical level of urban power grid, and it is also a necessary means to promote the rapid progress of urban civilization and improve the urban living environment. In the past 30 years, various technologies of power cables at home and abroad have developed rapidly, especially the development of three-layer co-extrusion production process to manufacture XLPE cables, which makes XLPE cables need no oil supply equipment and have better fire resistance compared with oil-filled cables. , Simple installation and maintenance, good mechanical and electrical performance, etc., are adopted by more and more countries. At present, the cables laid in many large cities are almost all XLPE cables. In 2007, the use of 10kVXLPE cables in the domestic power grid reached 40,000km, and the use of various industries was estimated to reach 120,000km. Among the high-voltage cables, there are only 64 lines of 220kV cable lines in Beijing, 164.1km, and 565 lines of 110kV cable lines, 647.4km. Foreign countries take Japan as an example, 22kV level Among the cables above and above, XLPE cables account for more than 70% of the total cable laying, and there is a trend of increasing year by year. In addition, the price of high-voltage XLPE cables is very expensive, the one-time investment cost is relatively large, and the cable line is not easy to change and branch.

In recent years, with the development of urban modernization and the continuous increase of unit capacity, the share of power cables in urban power supply has increased. In the urban areas of some cities, overhead transmission lines have gradually been replaced by laying cables; The increase and the extension of running time lead to frequent aging faults of the previously laid XLPE cables, causing insulation breakdown accidents, and even causing partial power grid blackouts, bringing interruptions and inconveniences to production and people's lives, and causing major economic losses. According to statistics, the insulation breakdown accidents of XLPE cables caused by the aging of water branches are on the rise year by year, and water branches have become a major hidden danger to the safe operation of power cables. In the 10-35kV domestic urban network system, ordinary XLPE cables used underground generally grow a large number of water trees after 8 to 12 years of operation, resulting in accidents caused by water tree breakdown of a large number of XLPE cables, short service life, and affecting the safety of the power grid run. At present, for the water tree aging detection of XLPE cables, a variety of methods have been proposed at home and abroad, mainly including: DC component method, DC superposition method, AC superposition method, low frequency superposition method, dielectric loss method and online partial discharge method, etc., and Corresponding detection devices have been developed. Among these methods, each method has its own advantages and disadvantages, and none of them can well reflect the water tree aging state of cable insulation. In recent years, the off-line diagnosis method using water tree as the object of aging diagnosis has AC excitation residual charge method, but its main disadvantage is that the release speed of residual charge is slow and the characteristic quantity is not obvious.

Contents of the invention

The purpose of the present invention is to propose a 10kVXLPE cable-based insulation aging diagnosis system and method for the deficiencies of the prior art.

The present invention solves its technical problem and realizes by taking the following technical solutions:

An insulation aging diagnosis system based on a 10kVXLPE cable, the system includes: a 10kVXLPE cable containing water, a DC power supply, a high-voltage pulse power supply and a data acquisition and processing unit, and one end of the core wire of the 10kVXLPE cable containing water is connected to the switch S1 and the switch S2 respectively through wires And one end of the switch S3, the other end of the switch S1 is connected to the DC power supply, the other end of the switch S2 is connected to the ground, the other end of the switch S3 is connected to the high-voltage pulse power supply, and the resistance R is connected between the outer side of the insulating layer of the 10kV XLPE cable near this end and the ground , the data acquisition and processing unit is connected at both ends of the resistor R, and the switch S4 is connected between the outer side of the insulating layer of the 10kV XLPE cable containing water and the ground near the other end far away from this end.

Moreover, the data acquisition and processing unit includes a conventional high-speed data acquisition card, and after the high-speed data acquisition card collects the voltage DC component signal, the computer adopts a conventional numerical integration method to process and perform time integration operation, and then the residual voltage corresponding to the voltage DC component signal can be obtained. amount of charge.

A kind of method based on the insulation aging diagnosis system of 10kVXLPE cable, it is characterized in that the method comprises the steps:

(1) Apply a negative DC voltage V _dc to the 10kV XLPE cable containing the water tree; close the switch S1 and the switch S4, open the switch S2 and the switch S3, and apply the negative DC voltage V _dc to the 10kV XLPE cable containing the water tree;

(2) Ground the high-voltage side of the cable; that is, switch S1 and switch S3 are disconnected, switch S2 and switch S4 are closed, and the trapped charges become residual charges during the grounding discharge process;

(3) Apply a high-voltage pulse voltage to the 10kV XLPE cable containing water, that is, when the switch S1, switch S2, and switch S4 are disconnected, and the switch S3 is closed, apply a high-voltage pulse voltage, and at the same time collect the DC component of the voltage on the resistor R through the data acquisition and processing unit signal, and perform time integral operation on the DC component of the voltage to obtain the amount of residual charge,

(4) Judging the water tree aging degree of the 10kVXLPE cable containing water tree according to the amount of residual charge.

Moreover, the setting of the magnitude and application time of the negative DC voltage V _dc in the step (1) is: when testing a 10kV power cable with a commissioning time of 1-5 years, the negative DC voltage V _dc can be set to -5kV , the application time is 5min, and for the 10kV power cable with a running time of more than 5 years, the negative DC voltage V _dc can be set to -3.5kV, and the application time is 2min.

Moreover, the high-voltage pulse voltage value applied in the step (3) can be set to 8kV, the repetition frequency is 30Hz-50Hz, and the application time 30s, the pulse group interval is 10s, and the number of pulse group applications does not exceed 5 times; when testing 10kV power cables that have been in operation for more than 5 years, the high-voltage pulse voltage value can be set to 5kV, the repetition frequency is 10Hz-20Hz, and the application time 15s, the pulse group interval is 10s, and the pulse group is applied 5-8 times.

Moreover, the specific method for judging the water tree aging degree of the 10kVXLPE cable containing water tree according to the residual charge in the step (4) is: after the first group of pulse groups act, if the released charge accounts for 1% of the total residual charge at the end of the measurement /2 or more, it can be considered that the degree of aging of water trees is serious; if it is between 1/3 and 1/2, it can be considered moderate aging; if it is less than 1/3, it can be considered mild aging.

Advantages and positive effects of the present invention are

1. The present invention replaces the existing AC excitation technology by applying pulse groups to make it easier to release residual charges. The rate of released charges after the action of the first group of pulse groups is used as a characteristic quantity to judge, and the aging degree is more clearly distinguished.

2. The pulsed residual charge method of the present invention can better identify the aging degree of water tree branches of XLPE cables. This method can be applied to the aging detection of cables, belongs to a non-destructive experiment, and can better detect the water tree aging degree , and can give an early warning according to the release rate of the residual charge to prevent the occurrence of insulation accidents.

Description of drawings

Fig. 1 is the experimental circuit diagram that the inventive method uses.

detailed description

The implementation of the present invention will be described in further detail below in conjunction with the accompanying drawings. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

An insulation aging diagnosis system and method based on 10kVXLPE cables, the system includes: 10kVXLPE cables with water trees, DC power supply, high-voltage pulse power supply and data acquisition and processing unit, as shown in Figure 1, one end of the core wire of 10kVXLPE cables with water trees passes through The wires are respectively connected to one end of the switch S1, switch S2 and switch S3, the other end of the switch S1 is connected to the DC power supply, the other end of the switch S2 is connected to the ground, the other end of the switch S3 is connected to the high-voltage pulse power supply, and the insulating layer of the 10kV XLPE cable near this end Connect the resistance R between the outside and the ground, connect the data acquisition and processing unit at both ends of the resistance R, and connect the switch S4 between the outside of the water-containing tree 10kV XLPE cable insulation layer and the ground at the other end close to and far from this end. The insulation aging diagnosis method Steps include:

(1) Apply negative DC voltage V _dc to 10kV XLPE cable containing water tree; close switch S1 and switch S4, open switch S2 and switch S3, apply negative DC voltage V _dc to 10kV XLPE cable containing water tree, the magnitude of negative DC voltage V _dc and the application time are set according to the user's requirements. For example, when testing 10kV power cables with a short operation time of 1-5 years, the negative DC voltage V _dc can be set to -5kV, and the application time is 5 minutes. For 10kV power cables longer than 5 years, the negative DC voltage V _dc can be set to -3.5kV, and the application time is 2min.

(2) Ground the high-voltage side of the cable; that is, switch S1 and switch S3 are disconnected, switch S2 and switch S4 are closed, and the charge, polarization charge and part of the ionic charge on the equivalent capacitance of the cable will be released, and in the water There will still be charges in the tree part, especially the tip of the water tree. This part of the charge is a trap charge, which will not be released during the ground discharge process, and will exist in the water tree part for a long time, that is, the residual charge;

(3) Apply a high-voltage pulse voltage to the 10kV XLPE cable containing water trees, that is, when the switch S1, switch S2, and switch S4 are disconnected, and the switch S3 is closed, a high-voltage pulse voltage is applied to release the residual charge in the water tree, and the residual charge is in the loop. The DC component will be superimposed on the pulse current, and the DC component signal of the voltage on the resistor R is collected by the data acquisition and processing unit, and the time integral operation is performed on the DC component of the voltage to obtain the residual charge.

(4) Judging the water tree aging degree of the 10kVXLPE cable containing water tree according to the amount of residual charge.

In the specific implementation of the present invention, the data acquisition and processing unit adopts a conventional high-speed data acquisition card. After the instrument collects the voltage DC component signal, the computer adopts a conventional numerical integration method to process and perform a time integration operation to obtain the residual charge.

In the specific implementation of the present invention, the applied high-voltage pulse voltage value can be set to 8kV, and the repetition frequency is 30Hz-50Hz when detecting a 10kV power cable with a short commissioning time of 1-5 years. , the application time is 30s, the pulse group interval is 10s, and the number of pulse group applications does not exceed 5 times; when testing 10kV power cables that have been put into operation for more than 5 years, the high-voltage pulse voltage value can be set to 5kV, and the repetition frequency is 10Hz -20Hz, the application time is 15s, the pulse group interval is 10s, and the pulse group is applied 5-8 times.

In the specific implementation of the present invention, the water tree aging degree of the 10kVXLPE cable can be judged according to the release ratio of the residual charge. More than 2, it can be considered that the degree of aging of water trees is serious; if it is between 1/3 and 1/2, it can be considered moderate aging; if it is less than 1/3, it can be considered mild aging.

Claims (1)

1. A method based on the insulation aging diagnosis system of 10kVXLPE cable, the system includes: water-containing tree 10kVXLPE cable, DC power supply, high-voltage pulse power supply and data acquisition and processing unit, one end of water-containing tree 10kVXLPE cable core wire is respectively connected to switch by wire S1, switch S2 and one end of switch S3, the other end of switch S1 is connected to DC power supply, the other end of switch S2 is connected to ground, the other end of switch S3 is connected to high-voltage pulse power supply, between the outside of the insulating layer of 10kV XLPE cable near this end and the ground Connect the resistor R between them, connect the data acquisition and processing unit at both ends of the resistor R, and connect the switch S4 between the water-containing tree 10kVXLPE cable insulating layer outside and the ground at the other end far away from this end, it is characterized in that the method includes the following steps: (1) Apply a negative DC voltage V _dc to the 10kV XLPE cable containing water trees; close the switch S1 and switch S4, open the switch S2 and switch S3, and apply a negative DC voltage V _dc to the 10kV XLPE cable containing water trees, where the negative DC voltage V _dc The setting of the size and application time is as follows: when testing a 10kV power cable with a commissioning time of 1-5 years, the negative DC voltage V _dc can be set to -5kV, and the application time is 5min. For power cables, the negative DC voltage V _dc can be set to -3.5kV, and the application time is 2 minutes; (2) Ground the high-voltage side of the cable; that is, switch S1 and switch S3 are disconnected, switch S2 and switch S4 are closed, and the trapped charge becomes residual charge during the grounding discharge process; (3) Apply high-voltage pulse voltage to the 10kV XLPE cable containing water, that is, when the switch S1, switch S2, and switch S4 are disconnected, and the switch S3 is closed, the high-voltage pulse voltage is applied, and at the same time, the DC component of the voltage on the resistor R is collected through the data acquisition and processing unit signal, and perform time integral calculation on the DC component of the voltage to obtain the amount of residual charge. Among them, the value of the applied high-voltage pulse voltage can be set as 8kV, repetition frequency 30Hz-50Hz, application time 30s, pulse group interval 10s, pulse group application times no more than 5 times; when testing 10kV power cables that have been put into operation for more than 5 years, the high voltage pulse voltage value can be set as 5kV, repetition frequency 10Hz-20Hz, application time 15s, pulse group interval 10s, pulse group application times 5-8 times; (4) Judging the water tree aging degree of 10kVXLPE cables containing water trees according to the amount of residual charge. The specific method for judging the water tree aging degree of 10kVXLPE cables containing water trees according to the amount of residual charge is: after the first group of pulse groups act, release the charge If the amount accounts for more than 1/2 of the total residual charge at the end of the measurement, it can be considered that the aging degree of the water tree is serious; if it is between 1/3 and 1/2, it can be considered moderate aging; if it is less than 1/3, it can be considered Aging is mild.