Method for detecting partial discharge capacity of dry-type transformer

Abstract

The invention relates to a method for detecting the partial discharge capacity of a dry-type transformer, and belongs to the technical field of transformer high-voltage tests. Firstly, a to-be-measured high-voltage-side three-phase connecting rod of the dry-type transformer is detached, measuring partial discharge points are arranged at the head end and the tail end of each phase of high-voltage-side winding respectively, then high-voltage-side head end terminals and high-voltage-side tail end terminals which are not connected with the tested measuring partial discharge points before the rod is detached are grounded, and low-voltage-side terminals corresponding to the tested measuring partial discharge points are pressurized. According to the method, the measured value of the discharge capacity of the tested measurement partial discharge point is obtained, the measured value of the discharge capacity of the tested measurement partial discharge point is compared with the threshold value, whether the tested measurement partial discharge point exceeds the standard or not is judged, the defect position is judged accordingly, no high-cost detection instrument needs to be used, the operation steps are simple, and the method is easy to implement. And the position with the defect can be quickly detected.

Description

Technical Field

[0001] The invention relates to a method for detecting partial discharge of a dry-type transformer, and belongs to the technical field of transformer high-voltage testing. Background Art

[0002] With the advancement of dry-type transformer manufacturing technology, general defects of high-voltage dry-type transformers can be detected or eliminated during the manufacturing process, but the partial discharge inside the dry-type transformer is not easy to control during the manufacturing process, so the partial discharge measurement of the dry-type transformer has become an important item in the dry-type transformer test. The size of the partial discharge of the dry-type transformer is an important indicator of the insulation performance of the transformer. Measuring the partial discharge level of the dry-type transformer is an effective method to evaluate the insulation performance of the transformer. The partial discharge test is an effective method that can successfully detect tiny defects in the insulation, and it is also used as an inspection method to assess whether the transformer can operate safely for a long time under the working voltage.

[0003] The invention patent document with the current publication number CN115184745A discloses a method for accurately locating partial discharge inside a Dyn11 dry-type transformer. This method combines the traditional pulse current method with ultraviolet detection, non-contact ultrasound and other live detection methods to detect whether there is a partial discharge signal exceeding the threshold inside or on the outer surface of the test equipment. After eliminating the interference, the position of the partial discharge source is preliminarily determined by the relationship between the transfer ratio and the magnitude of the partial discharge at each detection position, and then the judgment range is further narrowed by non-contact ultrasound. After that, optical fiber ultrasonic positioning is introduced to accurately determine the position of the partial discharge source. This method can determine the position of the partial discharge source, but the method is relatively complicated to operate and cannot quickly point out the defect location. At the same time, it is expensive to use ultrasonic equipment for accurate positioning. Summary of the invention

[0004] The purpose of the present invention is to provide a method for detecting partial discharge of a dry-type transformer, so as to solve the problems of high operating cost and complicated operating steps of the existing positioning method.

[0005] To achieve the above object, the solution of the present invention includes:

[0006] A method for detecting partial discharge of a dry-type transformer according to the present invention comprises the following steps:

[0007] 1) Remove the three-phase connecting rod on the high-voltage side of the dry-type transformer to be tested, and set the measurement partial discharge points at the beginning and end of each phase high-voltage side winding;

[0008] 2) The high-voltage side head and tail terminals that are not connected to the tested partial discharge point before the pole is removed are grounded, and the low-voltage side terminals corresponding to the tested partial discharge point are pressurized to obtain the discharge measurement value of the tested partial discharge point. By comparing the discharge measurement value of the tested partial discharge point with the threshold value, it is determined whether the tested partial discharge point exceeds the standard and thereby the location of the defect.

[0009] Beneficial effects: The dry-type transformer partial discharge detection method of the present invention sets the measurement points by removing the three-phase connecting rod on the high-voltage side of the dry-type transformer to be tested, and grounding the head and tail terminals on the high-voltage side that are not connected to the measured partial discharge point before the rod is removed, and detects each measurement point one by one. The method does not require any high-cost detection equipment, has simple operation steps, and can quickly detect the location of defects.

[0010] Furthermore, the dry-type transformer to be tested is a transformer that has been screened by a standard partial discharge test and has a partial discharge amount of at least one phase on the high-voltage side exceeding a second threshold.

[0011] Beneficial effect: Before carrying out the detection work of the present invention, the dry-type transformers to be tested can also be screened, and transformers with unqualified test results can be selected using the standard partial discharge test, and subsequent further testing can be carried out. This method performs preliminary screening through the standard partial discharge test, which can avoid unnecessary testing and improve the efficiency of partial discharge detection.

[0012] Furthermore, if the location of the excess is located in phase A, then the defective location is located in the upper half of phase A or the lower half of phase C; if the location of the excess is located in phase B, then the defective location is located in the upper half of phase B or the lower half of phase A; if the location of the excess is located in phase C, then the defective location is located in the upper half of phase C or the lower half of phase B.

[0013] Furthermore, when the head end of phase A is the test measurement point, the corresponding low-voltage side a0 terminal of A is pressurized, and the tail terminal of phase A on the high-voltage side, the head and tail terminals of phase B, and the head terminal of phase C are grounded respectively; when the lower end of phase A is the test measurement point, the corresponding low-voltage side a0 terminal of A is pressurized, and the head end of phase A on the high-voltage side, the tail end of phase B, and the head and tail ends of phase C are grounded.

[0014] Furthermore, when the head end of phase B is the test measurement point, the corresponding low-voltage side b0 terminal of B is pressurized, and the head end of phase A and the tail end of phase B are grounded, or the head and tail ends of phase C are grounded. When the tail end of phase B is the test measurement point, the corresponding low-voltage side b0 terminal of B is pressurized, and the head end of phase B and the tail end of phase C are grounded, or the head and tail ends of phase A are grounded.

[0015] Furthermore, when the head end of phase C is the test measurement point, the low-voltage side c0 terminal corresponding to C is pressurized, and the head and tail ends of phase A on the high-voltage side, the head end of phase B and the tail end of phase C are grounded respectively; when the tail end of phase C is the test measurement point, the low-voltage side c0 terminal corresponding to C is pressurized, and the head and tail ends of phase B, the head end of phase C and the tail end of phase A are grounded respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a measurement circuit diagram of a partial discharge test of the A-phase first end of a Dyn11 type dry-type transformer in a method embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of the pressurization process in the method embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0019] Dry-type transformer partial discharge detection method embodiment:

[0020] like Figure 1 A method for detecting partial discharge of a dry-type transformer is shown. First, the three-phase connecting rod on the high-voltage side of the dry-type transformer to be tested is removed, and a measuring partial discharge point is set at the head and tail ends of each phase high-voltage side winding. When measuring the partial discharge point of each phase, the head and tail terminals of the high-voltage side that are not connected to the measured partial discharge point are grounded, and the low-voltage side terminals corresponding to the measured partial discharge point are pressurized to obtain the discharge measurement value of each measured partial discharge point. Finally, the discharge measurement value of each measured partial discharge point is compared with the threshold value to determine whether the measured partial discharge point exceeds the standard. The specific implementation method is as follows:

[0021] This embodiment uses a Dyn11 dry-type transformer as an example to detect partial discharge. As another implementation, the detection method of this embodiment can be applied to any dry-type transformer with a D-type high-voltage side.

[0022] First, the dry-type transformer to be tested is screened out through the standard partial discharge test. Specifically, the pulse current method is used, and the partial discharge test wiring is performed according to the three-phase pressure method; first, square wave calibration is performed, and the standard calibration signal is injected into the upper outlet terminal of each phase, and the discharge amount at the same position of the other two phases is recorded, and the pressure is applied according to the standard test procedure to determine whether the partial discharge amount of each phase under the test voltage exceeds the second threshold. If it does not exceed the second threshold, the transformer is considered qualified. If it exceeds, it means that the transformer is unqualified, and further partial discharge detection is required, and the unqualified transformer is used as the dry-type transformer to be tested. The second threshold is the threshold of the standard test. According to GB1094.11-2022 "Power Transformer Part 11: Dry Transformer", the partial discharge amount should not be greater than 10pC, so the threshold is also not greater than 10pC when set. In this embodiment, the second threshold is 10pC.

[0023] Secondly, remove the three-phase connecting rod at the high-voltage end of the dry-type transformer to be tested, set measurement partial discharge points at the head and tail ends of the high-voltage side winding of each phase, and then ground the head and tail terminals of the high-voltage side that are not connected to the measured partial discharge points before the rods are removed, and pressurize the low-voltage side terminals corresponding to the measured partial discharge points to test each measurement partial discharge point of each phase.

[0024] Specifically, as shown in Table 1:

[0025] Table 1

[0026]

[0027] As shown in Table 1, when measuring whether the partial discharge point A (i.e., the head terminal of phase A) on the high-voltage side of the transformer to be tested exceeds the standard, point X (the tail terminal of phase A) and point C (the head terminal of phase C) are grounded, the head and tail ends of phase B are grounded respectively or the head and tail ends are short-circuited and then grounded, and voltage is applied to the a0 terminal on the low-voltage side;

[0028] When testing point X (the end terminal of phase A), point A (i.e. the beginning terminal of phase A) and point Y (i.e. the end terminal of phase B) which are not connected to point X are grounded respectively, the beginning and end of phase C are grounded respectively or the beginning and end are short-circuited and grounded, and voltage is applied to the a0 terminal on the low voltage side;

[0029] When testing point B (i.e., the head terminal of phase B), the terminals at point A and point Y are grounded, or as another implementation method, point C (i.e., the head terminal of phase C) and point Z (i.e., the tail terminal of phase C) are grounded, or the head and tail terminals of phase C are short-circuited and grounded, and voltage is applied to the b0 terminal on the low-voltage side;

[0030] When testing point Y (the tail terminal of phase B), point A and point X are grounded or short-circuited and then grounded, or as another implementation, point B and point Z are grounded, and voltage is applied to the b0 terminal on the low voltage side;

[0031] When testing point C (the first terminal of phase C), point A, point X, point B and point Z are grounded respectively, or as another implementation method, the terminals of point A and point X are short-circuited and then grounded, and points B and point Z are grounded respectively, and voltage is applied to the low-voltage side c0 terminal;

[0032] When testing point Z (the tail terminal of phase C), ground points A, X, B and Z respectively, or short-circuit the terminals at points B and Y and then ground them, ground points X and C respectively, and apply voltage to the c0 terminal on the low-voltage side.

[0033] The pressurization process is as follows: Figure 2 As shown, the measurement voltage in this embodiment is 1.3Ur*√3, and the excitation voltage is 1.8Ur*√3 (wherein Ur is the rated voltage of the transformer). The measured partial discharge points of the test subject are measured step by step, and then the partial discharge measurement values ​​of the upper and lower parts of the high-voltage windings of each phase A, B, and C of the dry-type transformer are obtained. The obtained partial discharge measurement values ​​are compared with the first threshold value, and the measurement data are compared to analyze the basic position of the defect in the dry-type transformer.

[0034] The first threshold is the maximum allowable discharge of the dry-type power transformer. In this embodiment, the maximum allowable discharge should not exceed 10pC according to GB1094.11-2022 "Power Transformer Part 11: Dry-type Transformer". The threshold is also not greater than 10pC when set. In this embodiment, the threshold can be 10pC. If the measured partial discharge value of the tested partial discharge point is greater than the first threshold, the phase where the tested partial discharge point is located exceeds the standard, and the location of the defect can be determined.

[0035] Specifically, when the excessive phase of local discharge is located in phase A, it can be determined that the defective position is located in the upper half of phase A or the lower half of phase C; when the excessive phase of local discharge is located in phase B, it can be determined that the defective position is located in the upper half of phase B or the lower half of phase A; when the excessive phase of local discharge is located in phase C, it can be determined that the defective position is located in the upper half of phase C or the lower half of phase B.

Claims

1. A method for detecting partial discharge of a dry-type transformer, characterized in that: The following steps are involved: 1) Remove the three-phase connecting rod on the high-voltage side of the dry-type transformer to be tested, and set the measurement partial discharge points at the beginning and end of each phase high-voltage side winding; 2) The head and tail terminals on the high-voltage side that are not connected to the partial discharge point under test before the pole is removed are grounded, and the low-voltage side terminals corresponding to the partial discharge point under test are pressurized to obtain the discharge measurement value of the partial discharge point under test, and the discharge measurement value of the partial discharge point under test is compared with the first threshold value to determine whether the partial discharge point under test exceeds the standard and thereby determine the location of the defect.

2. The dry-type transformer partial discharge detection method according to claim 1 is characterized in that: The dry-type transformer to be tested is a transformer that has been screened by a standard partial discharge test and has a partial discharge amount of at least one phase on the high-voltage side exceeding a second threshold.

3. The dry-type transformer partial discharge detection method according to claim 1, characterized in that: If the location where the standard is exceeded is in phase A, then the defective location is in the upper half of phase A or the lower half of phase C; if the location where the standard is exceeded is in phase B, then the defective location is in the upper half of phase B or the lower half of phase A; if the location where the standard is exceeded is in phase C, then the defective location is in the upper half of phase C or the lower half of phase B.

4. The method for detecting partial discharge of a dry-type transformer according to any one of claims 1 to 3, characterized in that: When the head end of phase A is the test measurement point, the corresponding low-voltage side a0 terminal of A is pressurized, and the tail terminal of phase A on the high-voltage side, the head and tail terminals of phase B, and the head terminal of phase C are grounded respectively; when the lower end of phase A is the test measurement point, the corresponding low-voltage side a0 terminal of A is pressurized, and the head end of phase A on the high-voltage side, the tail end of phase B, and the head and tail ends of phase C are grounded.

5. The method for detecting partial discharge of a dry-type transformer according to any one of claims 1 to 3, characterized in that: When the head end of phase B is the test measurement point, the corresponding low-voltage side b0 terminal of B is pressurized, and the head end of phase A and the tail end of phase B are grounded, or the head and tail ends of phase C are grounded. When the tail end of phase B is the test measurement point, the corresponding low-voltage side b0 terminal of B is pressurized, and the head end of phase B and the tail end of phase C are grounded, or the head and tail ends of phase A are grounded.

6. The method for detecting partial discharge of a dry-type transformer according to any one of claims 1 to 3, characterized in that: When the head end of phase C is the test measurement point, the low-voltage side c0 terminal corresponding to C is pressurized, and the head and tail ends of phase A, the head end of phase B and the tail end of phase C on the high-voltage side are grounded respectively; when the tail end of phase C is the test measurement point, the low-voltage side c0 terminal corresponding to C is pressurized, and the head and tail ends of phase B, the head end of phase C and the tail end of phase A are grounded respectively.

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