Calibration method for discharge test of transformer directly connected with GIS and oil-gas bushing

Abstract

The invention relates to the technical field of transformer calibration, and discloses a GIS and oil gas bushing direct connection transformer discharge test calibration method comprising the following steps: S1, recovering gas in a GIS, and taking out a high voltage bushing oil gas direct connection conductive connecting rod in a GIS connection gas chamber; s2, carrying out primary calibration; s3, recovering the gas in the GIS and putting back the taken-out high-voltage bushing oil-gas direct-connection conductive connecting rod in the GIS connection gas chamber, applying the square wave signal from the low-voltage side again before the partial discharge test, recording the ratio k2-1 of the low-voltage-to-high-voltage transfer relationship, and calculating to obtain the ratio k1-2 of the high-voltage-to-low-voltage transfer relationship; s4, calling the stored value in the step S2, starting a partial discharge test of the transformer, and recording data according to conversion ratios K1-2 and K2-1; according to the scheme, only the GIS air chamber and the three-phase conductive connecting rod in the GIS air chamber need to be dismounted once, so that the dismounting times are reduced; through two times of calibration, the partial discharge test precision is improved; the working efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of transformer calibration, and in particular to a transformer discharge test calibration method for direct connection of a GIS with an oil and gas casing. Background Art

[0002] At present, GIS is widely used in substations, power plants and other places due to its advantages such as small footprint, small operation and maintenance workload, high safety and reliability. There are two ways to connect GIS to power transformers. One is that conventional power transformers enter GIS through overhead lines, and the other is that GIS is directly connected to the transformer oil and gas bushing. Due to the advantages of small space occupation, good anti-pollution effect, high safety and reliability, this form of GIS and transformer oil and gas bushing is gradually being promoted in the power industry.

[0003] The transformer partial discharge test can effectively detect the partial discharge between turns, sections, and layers of the transformer, and assess the insulation performance of the transformer. According to the "Preventive Test Procedure for Power Equipment" (DL / T 596-2021), transformers of 110kV and above need to carry out partial discharge measurement after Class A maintenance or when necessary. According to the "Guidelines for On-site Measurement of Partial Discharge of Power Equipment" (DL / T 417-2019), the test circuit should be calibrated every time it is changed. However, the power transformer with GIS directly connected to the oil and gas casing is different from the conventional transformer. The high-voltage bushing of the transformer with the oil and gas casing structure is small and directly connected to the GIS, and the converted capacitance is large. The signal is weak or there is no signal during square wave calibration, which is not conducive to the implementation of partial discharge test. Therefore, when calibrating the square wave, it is necessary to open the GIS gas chamber and its internal conductive connecting rods phase by phase, and there will be certain changes in the calibration after inflation. The power transformer is a three-phase transformer, and partial discharge tests need to be carried out on all three phases. If the GIS gas chamber is deflated, inflated, and its internal conductive connecting rods are removed every time it is changed back, a lot of manpower, material resources and time are wasted. Summary of the invention

[0004] In view of this, the present invention provides a transformer discharge test calibration method in which a GIS is directly connected to an oil and gas casing, so as to solve the problem of complicated steps in the discharge test.

[0005] The present invention provides a transformer discharge test calibration method for direct connection between GIS and oil and gas casing, comprising the steps of:

[0006] S1, recover the gas in GIS, take out the high-voltage bushing oil-gas direct-connected conductive connecting rod in the GIS connecting gas chamber;

[0007] S2. Initial calibration: Connect the measuring impedance to the high-voltage bushing and the low-voltage bushing at the same time, perform square wave calibration on the high-voltage bushing and the low-voltage bushing respectively, the calibration value is X, and record the square wave value at each location, so as to obtain the ratio K of the transmission relationship between high pressure and low pressure1-2 , and the ratio of low pressure to high pressure transmission relationship K 2-1 , and store the value;

[0008] S3. Recalibrate; restore the gas in the GIS and put back the high-voltage bushing oil-gas direct-connected conductive connecting rod in the gas chamber of the GIS. Before entering the partial discharge test, apply a square wave signal from the low-voltage side again and record the ratio k of the transmission relationship between the low voltage and the high voltage. 2-1 , passing the ratio K of the relationship through step S2 1-2 , calculate the ratio k of the transmission relationship between high pressure and low pressure 1-2 , no value is stored after calibration is completed;

[0009] S4, call the value stored in S2, start the transformer partial discharge test, according to the conversion ratio K 1-2 and K 2-1 Record data; after the test is completed, change phases and repeat step S3 until the test is completed.

[0010] As a preferred solution, in step S1, the SF6 gas in the GIS is recovered phase by phase, and the recovery process strictly implements the process quality standards.

[0011] As a preferred solution, in step S1, after the gas is recovered, the GIS gas chamber is opened and the three-phase high-voltage bushing oil-gas direct-connected conductive connecting rods are taken out respectively.

[0012] As a preferred solution, in step S2, the transformer is wired for partial discharge test using the induction test method, the head end of the low-voltage test winding is pressurized, and the tail end is grounded. A measuring impedance is connected at the end screen or voltage divider of the low-voltage side bushing, and a coaxial cable is used to lead the signal to one channel of the partial discharge instrument; at the same time, a measuring impedance is connected at the end screen of the high-voltage bushing, and a coaxial cable is used to lead the signal to another channel of the partial discharge instrument. The measuring impedance is connected to the high-voltage bushing and the low-voltage bushing at the same time, and square wave calibration is performed on the high and low voltage of phase A, phase B, and phase C respectively.

[0013] As a preferred solution, in step S2, the calibration value is 500 pC.

[0014] As a preferred solution, in step S2, the high voltage neutral point in the calibration loop needs to be grounded.

[0015] As a preferred solution, in step S3, before entering the partial discharge test, a 500 pC square wave signal is applied again from the low voltage side.

[0016] As a preferred solution, in step S3, the process quality standard is implemented when the GIS air chamber is restored.

[0017] This solution only requires dismantling the GIS gas chamber and its internal three-phase conductive connecting rods once, thus reducing the number of dismantling times; through two calibrations, the calibration of SF6 gas pressure recovery is converted, thereby improving the accuracy of partial discharge tests; the present invention greatly improves work efficiency, reduces production costs, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a schematic diagram of the calibration of the A phase connection according to the embodiment of the present invention.

[0020] Figure 2 It is a top view of the oil-gas integrated transformer according to an embodiment of the present invention.

[0021] Description of reference numerals:

[0022] 1. Transformer body; 2. A-phase high-voltage bushing; 3. A-phase low-voltage bushing; 4. High-voltage bushing oil-gas direct-connected conductive connecting rod; 5. First GIS connection chamber; 6. Low-voltage excitation line; 7. Low-voltage side measurement impedance; 8. Low-voltage end screen lead-out terminal; 9. High-voltage side measurement impedance; 10. High-voltage end screen lead-out terminal; 11. Low-voltage side coaxial cable; 12. High-voltage side coaxial cable; 13. Partial discharge instrument; 14. Partial discharge ch1 channel; 15. Partial discharge ch2 channel; 16. Calibration pulse generator; 17. Second GIS connection chamber; 18. High-voltage neutral point; 19. B-phase low-voltage bushing; 20. C-phase low-voltage bushing; 21. Third GIS connection chamber. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0024] The present invention provides a transformer discharge test calibration method for direct connection between GIS and oil and gas casing, comprising the steps of:

[0025] S1, recover the gas in the GIS, and take out the high-voltage bushing oil-gas direct-connection conductive connecting rod 4 in the GIS connecting gas chamber;

[0026] S2. Initial calibration: Connect the measuring impedance to the high-voltage bushing and the low-voltage bushing at the same time, perform square wave calibration on the high-voltage bushing and the low-voltage bushing respectively, the calibration value is X, and record the square wave value at each location, so as to obtain the ratio K of the transmission relationship between high pressure and low pressure 1-2 , and the ratio of low pressure to high pressure transmission relationship K 2-1 , and store the value;

[0027] S3, recalibrate; restore the gas in the GIS and put back the high-voltage bushing oil and gas direct conductive connecting rod 4 in the gas chamber of the GIS. Before entering the partial discharge test, apply a square wave signal from the low-voltage side again and record the ratio k of the transmission relationship between the low voltage and the high voltage. 2-1 , passing the ratio K of the relationship through step S2 1-2 , calculate the ratio k of the transmission relationship between high pressure and low pressure 1-2 , no value is stored after calibration is completed;

[0028] S4, call the value stored in S2, start the transformer partial discharge test, according to the conversion ratio K 1-2 and K 2-1 Record data; after the test is completed, change phases and repeat step S3 until the test is completed.

[0029] This solution only requires dismantling the GIS gas chamber and its internal three-phase conductive connecting rods once, thus reducing the number of dismantling times; through two calibrations, the calibration of SF6 gas pressure recovery is converted, thereby improving the accuracy of partial discharge tests; the present invention greatly improves work efficiency, reduces production costs, and has significant economic and social benefits.

[0030] It should be noted that SF6 gas is sulfur hexafluoride gas, which is a common gas in GIS gas chambers. In this solution, it is mainly aimed at three-phase power transformers, so the GIS gas chambers also have three, namely phase A, phase B and phase C. It should be noted that the high-voltage side voltage in this solution is greater than the low-voltage side voltage.

[0031] like Figure 1As shown, it should be noted that the square wave calibration circuit of the A-phase partial discharge test of the power transformer with GIS directly connected to the oil and gas bushing includes: A-phase high-voltage bushing 2, high-voltage neutral point 18, a-phase low-voltage bushing 3, c-phase low-voltage bushing 20, low-voltage excitation line 6, low-voltage side measurement impedance 7, low-voltage end screen lead-out terminal 8, high-voltage side measurement impedance 9, high-voltage end screen lead-out terminal 10, low-voltage side coaxial cable 11, high-voltage side coaxial cable 12, partial discharge instrument 13, partial discharge ch1 channel 14, partial discharge ch2 channel 15. The low-voltage excitation line 6, a-phase low-voltage bushing 3, and c-phase low-voltage bushing 20 constitute a low-voltage excitation circuit, and the A-phase high-voltage bushing 2 and the high-voltage neutral point 18 constitute a high-voltage induction circuit. The low-voltage side measuring impedance 7, the low-voltage end-screen lead-out terminal 8, the low-voltage side coaxial cable 11, the partial discharge instrument 13, the partial discharge ch1 channel 14, the high-voltage side measuring impedance 9, the high-voltage end-screen lead-out terminal 10, the high-voltage side coaxial cable 12, the partial discharge ch2 channel 15, and the calibration pulse generator 16 constitute a transfer calibration loop.

[0032] Furthermore, in step S1, the SF6 gas in the GIS is recovered phase by phase, and the recovery process strictly implements the process quality standards.

[0033] Furthermore, in step S1, after the gas is recovered, the GIS gas chamber is opened, and the three-phase high-voltage bushing oil-gas direct-connected conductive connecting rods 4 are taken out respectively.

[0034] Furthermore, in step S2, the transformer is wired for partial discharge test using the induction test method, the head end of the low-voltage test winding is pressurized, and the tail end is grounded. A measuring impedance is connected at the end screen or voltage divider of the low-voltage side bushing, and a coaxial cable is used to lead the signal to one channel of the partial discharge instrument 13; at the same time, a measuring impedance is connected at the end screen of the high-voltage bushing, and a coaxial cable is used to lead the signal to another channel of the partial discharge instrument 13. The measuring impedance is connected to the high-voltage bushing and the low-voltage bushing at the same time, and the square wave calibration is performed on the high and low voltage of phase A, phase B, and phase C respectively.

[0035] Further, in step S2, the calibration value X is 500 pC.

[0036] Furthermore, in step S2, the high voltage neutral point 18 in the calibration loop needs to be grounded.

[0037] Furthermore, in step S3, before entering the partial discharge test, a 500 pC square wave signal is applied again from the low voltage side.

[0038] Further, in step S3, the process quality standard is implemented when the GIS air chamber is restored.

[0039] It should be noted that, specifically, the first step is to recycle the SF6 gas and take out the high-voltage bushing oil-gas direct-connected conductive connecting rods 4 in the first GIS connecting air chamber 5, the second GIS connecting air chamber 17, and the third GIS connecting air chamber 21. The SF6 gas recovery device is used to recover the SF6 gas in the first GIS connecting air chamber 5, the second GIS connecting air chamber 17, and the third GIS connecting air chamber 21 phase by phase, and the specific recovery process strictly implements the relevant process quality standards. After recovering the gas, open the GIS air chamber and take out the three-phase high-voltage bushing oil-gas direct-connected conductive connecting rods 4 respectively. It should be noted that each GIS air chamber has a high-voltage bushing oil-gas direct-connected conductive connecting rod 4 and the connection form is the same.

[0040] The A-phase air chamber is the first GIS connection air chamber 5 , the B-phase air chamber is the second GIS connection air chamber 17 , and the C-phase air chamber is the third GIS connection air chamber 21 .

[0041] It should be noted that the transformer body 1 is a common transformer.

[0042] The second step is to connect the A-phase calibration loop and reliably ground the high-voltage neutral point 18; the low-voltage excitation line 6 is connected to the a-phase low-voltage bushing 3 terminal, and the c-phase low-voltage bushing 20 terminal is reliably grounded. At the same time, the low-voltage end screen lead-out terminal 8, the low-voltage side measurement impedance 7, and the low-voltage side coaxial cable 11 are connected to the ch1 channel 14 of the partial discharge instrument 13 in sequence; the high-voltage end screen lead-out terminal 10, the high-voltage side measurement impedance 9, and the high-voltage side coaxial cable 12 are connected to the ch2 channel 15 of the partial discharge instrument 13 in sequence. Square wave calibration is performed on the A-phase high and low voltage respectively, and the calibration value is 500pC. The transfer relationship K of high voltage to low voltage and low voltage to high voltage is recorded. 1-2 , K 2-1 Before the GIS air chamber restores pressure, phase A, phase B, and phase C need to be calibrated and stored.

[0043] The third step is to restore the GIS gas chamber and use the SF6 gas recovery device to restore the SF6 gas pressure in the GIS gas chamber to normal. The specific recovery process strictly complies with the relevant process quality standards. After recovery, the SF6 gas is subjected to a micro-water test to ensure that the test is qualified. According to the second step, the A phase calibration loop is connected again. Before the partial discharge test, a 500pC square wave signal is applied from the low voltage side again, and the transmission relationship between the low voltage and the high voltage is recorded. 2-1 , the conversion and the transfer relationship K in the second step 1-2 The value is not stored after calibration is completed.

[0044] Step 4: Retrieve the value stored in step 2, start the transformer partial discharge test, and record the data according to the conversion ratio. After the test is completed, change phases and repeat step 3 to complete the test.

[0045] It should be noted that according to Figure 2 As shown, a b-phase low-voltage bushing 19 and a c-phase low-voltage bushing 20 are also provided, and the b-phase low-voltage bushing 19 and the c-phase low-voltage bushing 20 are provided in the same manner as the a-phase low-voltage bushing 3 .

[0046] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A transformer discharge test calibration method for direct connection between GIS and oil and gas casing, characterized in that: Includes steps: S1, recover the gas in the GIS, and take out the high-voltage bushing oil-gas direct-connected conductive connecting rod (4) in the GIS connecting gas chamber; S2. Initial calibration: Connect the measuring impedance to the high-voltage bushing and the low-voltage bushing at the same time, perform square wave calibration on the high-voltage bushing and the low-voltage bushing respectively, the calibration value is X, and record the square wave value at each location, so as to obtain the ratio K of the transmission relationship between high pressure and low pressure 1-2 , and the ratio of low pressure to high pressure transmission relationship K 2-1 , and store the value; S3, recalibrate; restore the gas in the GIS and put back the high-voltage bushing oil-gas direct-connected conductive connecting rod (4) in the gas chamber of the GIS. Before entering the partial discharge test, apply a square wave signal from the low-voltage side again and record the ratio k of the transmission relationship between the low voltage and the high voltage. 2-1 , passing the ratio K of the relationship through step S2 1-2 , calculate the ratio k of the transmission relationship between high pressure and low pressure 1-2 , no value is stored after calibration is completed; S4, call the value stored in S2, start the transformer partial discharge test, according to the conversion ratio K 1-2 and K 2-1 Record data; after the test is completed, change phases and repeat step S3 until the test is completed.

2. The transformer discharge test calibration method for direct connection of GIS and oil and gas casing according to claim 1 is characterized in that: In step S1, the SF6 gas in the GIS is recovered phase by phase, and the recovery process strictly implements the process quality standards.

3. The transformer discharge test calibration method for direct connection of GIS and oil and gas casing according to claim 1 is characterized in that: In step S1, after the gas is recovered, the GIS gas chamber is opened and the three-phase high-voltage bushing oil-gas direct-connected conductive connecting rods (4) are taken out respectively.

4. The transformer discharge test calibration method for direct connection of GIS and oil and gas casing according to claim 1 is characterized in that: In step S2, the transformer is wired for partial discharge test using an induction test method, the head end of the low-voltage test winding is pressurized, and the tail end is grounded. A measuring impedance is connected to the low-voltage side bushing end screen or voltage divider, and a coaxial cable is used to lead a signal to one channel of the partial discharge instrument (13); at the same time, a measuring impedance is connected to the high-voltage bushing end screen, and a coaxial cable is used to lead a signal to another channel of the partial discharge instrument (13); the measuring impedance is connected to the high-voltage bushing and the low-voltage bushing at the same time, and square wave calibration is performed on the high and low voltages of phase A, phase B, and phase C respectively.

5. The transformer discharge test calibration method for direct connection of GIS and oil and gas casing according to claim 1 is characterized in that: In step S2, the calibration value is 500 pC.

6. The transformer discharge test calibration method for direct connection of GIS and oil and gas casing according to claim 1 is characterized in that: In step S2, the high voltage neutral point (18) in the calibration loop needs to be grounded.

7. The transformer discharge test calibration method for direct connection of GIS and oil and gas casing according to claim 1 is characterized in that: In step S3, before entering the partial discharge test, a 500 pC square wave signal is applied again from the low voltage side.

8. The transformer discharge test calibration method for direct connection of GIS and oil and gas casing according to claim 1 is characterized in that: In step S3, the process quality standard is implemented when the GIS air chamber is restored.

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