Test method for dielectric loss factor of valve-side bushing and winding of converter transformer

Abstract

The present invention provides a method for testing the dielectric loss factor of the valve side bushing and winding of a converter transformer, and relates to the field of power measurement technology, including: connecting the converter transformer valve by the positive connection method; obtaining the test insulation resistance of the valve side winding to the grid-measurement winding; obtaining the capacitance and dielectric loss factor of the valve side winding to the grid-measurement winding; and testing the valve side winding to the grid-measurement winding according to the test insulation resistance value, capacitance and dielectric loss factor. The present invention adopts the positive connection method to measure the capacitance and dielectric loss factor of the converter transformer valve side winding to the grid-measurement winding without disconnecting the lead, so as to better improve work efficiency, reduce labor costs, and ensure the personal safety of operators. It has the advantages of shortening the test working hours and reducing the high labor intensity and high risks brought by the test wiring removal work, and has great significance for the lean maintenance work of converter stations in the future.

Description

Technical Field

[0001] The present invention relates to the field of electric power measurement technology, and in particular to a method for testing a dielectric loss factor of a converter transformer valve side bushing together with a winding, which is used for preventive testing of a converter transformer valve side bushing and a bushing together with a winding. Background Art

[0002] According to the "Preventive Test Procedure for ±800kV UHV DC Equipment" (DLT273-2012) and the "State Grid Corporation DC Converter Station Inspection Management Regulations", the current valve side bushing high-voltage test items include: insulation resistance measurement, dielectric loss tangent value and capacitance measurement, with a pre-test period of 3 years. When the valve side bushing is tested using the traditional test method, it is necessary to apply a test voltage to the top of the valve side bushing terminal and obtain a current signal from the bushing end screen connection.

[0003] Since the valve-side bushings of the 12 converter transformers in each pole of the converter station are all connected by hard tube busbars, it is very complicated to disconnect and reconnect the outlet lines of the valve-side bushings, and the workload of disconnection and reconnection is large, and it also causes certain damage to the hardware connection equipment. Summary of the invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the present invention provides a method for testing the dielectric loss factor of the valve-side bushing and the winding of the converter transformer, which effectively reduces the test preparation time and improves the maintenance efficiency of the converter transformer in the power industry.

[0005] The technical solution of the present invention is:

[0006] The dielectric loss factor test method of the valve-side bushing and winding of the converter transformer includes:

[0007] The positive connection method is used for wiring the converter valve;

[0008] Obtain the test insulation resistance of the valve side winding to the network test winding;

[0009] Obtain the capacitance and dielectric loss factor of the valve-side winding to the grid-side winding;

[0010] The valve side winding and the network test winding are tested according to the test insulation resistance value, capacitance and dielectric loss factor.

[0011] As a further technical solution of the present invention, the converter transformer valve is connected by the positive connection method; specifically, the positive connection method is used for wiring without disconnecting the lead wires, and the grounding terminal E of the transformer casing and the casing of the high-voltage dielectric loss bridge is grounded; the first bushing and the second bushing on the three-phase converter transformer valve side are short-circuited through the accessory test line, the first bushing and the second bushing on the valve side are connected to the valve tower arrester, and the internal cathode grounding knife, the anode grounding knife, and the converter transformer side grounding knife are disconnected from the valve group.

[0012] As a further technical solution of the present invention, the test insulation resistance of the valve side winding to the grid test winding is obtained; specifically, the test includes: applying a voltage of 5000V after the first bushing and the second bushing on the three-phase converter transformer valve side are short-circuited, the grid side winding is short-circuited, and the capacitive current and resistive current signals of the grid side winding are obtained after the iron core and the clamp are short-circuited.

[0013] As a further technical solution of the present invention, the capacitance and dielectric loss factor of the valve side winding to the grid side winding are obtained; specifically, a dielectric loss meter is used, the external standard capacitor access terminal of the dielectric loss meter is connected to the external standard capacitor, the test terminal of the dielectric loss meter is connected to the product to be tested, the positive poles of the external standard capacitor and the product to be tested are connected to the high-voltage output terminal, and the capacitance and dielectric loss are obtained by comparing the current difference between the product to be tested and the external standard capacitor.

[0014] Furthermore, the external standard capacitor and the product to be tested are connected to the dielectric loss meter using a shielded cable with a shielded plug.

[0015] Furthermore, the dielectric loss tester adopts a multi-channel tester with a model of AI6000LX and a capacity of 60nF.

[0016] As a further technical solution of the present invention, the capacitance and dielectric loss factor of the valve-side winding to the grid-side winding are obtained; specifically, the following steps are included:

[0017] Test of capacitance and dielectric loss factor of valve side winding to grid side winding;

[0018] Test of capacitance and dielectric loss factor of valve side winding to core clamp;

[0019] Test the capacitance and dielectric loss factor of the valve side winding to the grid side winding and core clamps.

[0020] Furthermore, the test insulation resistance of the valve side winding to the grid test winding is obtained; specifically, the insulation resistance of the valve side winding to the grid side winding is used instead of the insulation resistance of the valve side winding to the grid side winding and the ground.

[0021] Furthermore, the dielectric loss value tested by the dielectric loss meter is ≤0.006, and the test value variation does not exceed 30%.

[0022] Furthermore, the dielectric loss meter capacity of the converter transformer valve is ≥60nf (10kV), and the insulation megohmmeter capacity is ≥3mA (5kV).

[0023] The beneficial effects of the present invention are:

[0024] 1. The test wiring of the capacitance and dielectric loss factor of the valve side winding to the grid side winding and the core clamp adopts the positive connection method. The E end of the transformer shell and the shell of the high-voltage dielectric loss bridge is grounded. After all the bushings on the valve side of the three-phase converter transformer are short-circuited, 10kV is applied, and the grid side winding and the core clamp (disconnected from grounding) are short-circuited to obtain the signal.

[0025] 2. It is not necessary to disconnect the valve side bushing from the valve tower arrester. When the insulation resistance between the valve side winding and the grid side winding is tested with the valve tower, the insulation resistance value does not drop significantly. The grounding knife switch connected to the valve group should be opened during the test.

[0026] 3. When conducting insulation test on valve side bushing (including main insulation, dielectric loss and capacitance test), apply 10kV voltage to the bushing end, take signal from the end screen, and conduct positive connection test. When conducting dielectric loss test on valve side winding, test capacitance and dielectric loss factor of valve side winding to grid side winding, capacitance and dielectric loss factor of valve side winding to core clamp, capacitance and dielectric loss factor of valve side winding to grid side winding and core clamp respectively. The test value can be controlled according to dielectric loss value ≤0.006, and the change with the last test value shall not exceed 30%.

[0027] 4. The present invention adopts the positive connection method to measure the capacitance and dielectric loss factor of the converter transformer valve side winding to the grid side winding without disconnection. It can better improve work efficiency, reduce labor costs, and ensure the personal safety of operators, which is of great significance to the lean maintenance of converter stations in the future. It has the advantages of shortening the test time and reducing the high labor intensity and high risk caused by the test disassembly work. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flow chart of a method for testing the dielectric loss factor of a converter transformer valve side bushing and windings proposed by the present invention;

[0029] Figure 2 It is a wiring diagram for testing the capacitance and dielectric loss factor of the valve side winding to the grid side winding and the core clamp proposed by the present invention;

[0030] Figure 3 The dielectric loss meter test wiring diagram proposed by the present invention;

[0031] Figure 4 A test diagram of a specific embodiment of the present invention;

[0032] Figure 5 A test diagram of a specific embodiment of the present invention;

[0033] Figure 6 A test diagram of a specific embodiment of the present invention; DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0035] In accordance with the "Preventive Test Procedures for ±800kV UHV DC Equipment" (DL / T273-2012), the insulation resistance and polarization index of the winding and bushing must be measured every three years; at the same time, the dielectric loss test of the winding and bushing must be carried out to determine whether the UHV DC equipment is affected by moisture and whether there are any local defects.

[0036] like Figure 1 As shown, the dielectric loss factor test method of the valve side bushing of the converter transformer valve together with the winding includes:

[0037] The positive connection method is used for the flow-changing valve;

[0038] Obtain the test insulation resistance of the valve side winding to the network test winding;

[0039] Obtain the capacitance and dielectric loss factor of the valve-side winding to the grid-side winding;

[0040] The valve side winding and the network test winding are tested according to the test insulation resistance value, capacitance and dielectric loss factor.

[0041] In the embodiment of the present invention, the positive connection method is used for wiring the converter transformer; specifically, the positive connection method is used for wiring without disconnecting the lead wire, and the grounding terminal E of the transformer housing and the housing of the high-voltage dielectric loss bridge is grounded; the first and second bushings on the three-phase converter transformer valve side are short-circuited through the accessory test line, the first and second bushings on the valve side are connected to the valve tower arrester B, and the inner cathode ground knife C, the anode ground knife D and the converter transformer side ground knife F are disconnected from the valve group. The positive connection method is used for the test wiring of the capacitance and dielectric loss factor (tgδ) of the valve side winding to the grid side winding and the core clamp. The E end of the transformer housing and the housing of the high-voltage dielectric loss bridge is grounded, and after the first bushing a and the second bushing b on the three-phase converter transformer valve side are all short-circuited, the voltage is applied to 10kV, and the grid side winding and the core clamp (disconnected from grounding) are short-circuited to obtain the capacitive current and resistive current signals, and the instrument automatically calculates tgδ. It is not necessary to disconnect the first bushing a and the second bushing b on the valve side from the valve tower arrester B. Only the soft connection at A needs to be disconnected. When the insulation resistance between the valve side winding and the grid side winding is tested with the valve tower, the insulation resistance value does not drop significantly. During the test, the grounding switches F, C, and D connected to the valve group should be opened.

[0042] In an embodiment of the present invention, the test insulation resistance of the valve side winding to the grid-measured winding is obtained; specifically, the test includes: applying a voltage of 5000V after the first bushing and the second bushing on the valve side of the three-phase converter transformer are short-circuited, the grid-side winding is short-circuited, and the capacitive current and resistive current signals after the grid-measured winding and the core clamp are short-circuited. Among them, the insulation resistance of the valve side winding to the grid side winding refers to directly measuring the insulation resistance between the windings, instead of the insulation resistance between the windings and the ground. The test is performed by short-circuiting the first bushing a and the second bushing b of the valve side bushing, applying a voltage of 5000V, and short-circuiting the grid-side winding.

[0043] Table 1 shows the results of three positive connection tests on the valve side during the annual inspection of Tianshan Converter Station in 2021, including no leads connected (opening the positive and negative pole grounding switches and the grounding switches on the valve side of the converter transformer), disconnecting the valve side bushing from the valve tower (disconnecting only the soft connection between the valve tower and the arrester), and all leads of the valve side bushing (one unit). The three positive connection tests were carried out without untying the leads. Whether the three grounding switches on the cathode, anode, and non-test converter transformer side of the valve side were disconnected had a great influence on the results (the grounding switches on the tested converter transformer side must be pulled open during the test). Table 2 shows the results of the dielectric loss capacitance test of the high YYB phase valve side of pole 2 to the core clamp, the valve side to the grid side, and the core clamp when the three grounding switches were in different states. It can be seen from Table 2 that the three grounding switches have a certain influence on the test results of the dielectric loss capacitance, and have a greater impact on the dielectric loss test. The test data after all the grounding switches were pulled open are basically consistent with the test data after the soft connection was disconnected.

[0044] Table 1

[0045]

[0046] Table 2

[0047]

[0048] In the embodiment of the present invention, the capacitance and dielectric loss factor of the valve-side winding to the grid-side winding are obtained; specifically, the following steps are performed:

[0049] Test of capacitance and dielectric loss factor of valve side winding to grid side winding;

[0050] Test of capacitance and dielectric loss factor of valve side winding to core clamp;

[0051] Test the capacitance and dielectric loss factor of the valve side winding to the grid side winding and core clamps.

[0052] See also Figure 3 When conducting the valve side winding dielectric loss test, follow Figure 3Wiring is carried out to test the capacitance and dielectric loss factor (tanδ) of the valve side winding to the grid side winding (iron core and clamps are grounded), the shell of the transformer, the iron core, the clamps, and the E end of the shell of the high-voltage dielectric loss bridge are grounded, and the a and b bushings on the three-phase converter transformer valve side are short-circuited and pressurized to 10kV, and the grid side winding is taken as a signal; according to Figure 4 Test the capacitance and dielectric loss factor (tgδ) of the winding on the connection valve side to the core clamp (the core and clamp are disconnected and grounded), the transformer shell and the E end of the high-voltage dielectric loss bridge shell are grounded, the grid side winding is short-circuited and grounded, and the a and b bushings on the three-phase converter transformer valve side are short-circuited and pressurized to 10kV, and the core clamp is disconnected and grounded and then short-circuited to obtain the signal; according to Figure 5 The capacitance and dielectric loss factor (tgδ) of the valve-side winding to the grid-side winding and the core clamp are tested (the core and clamp are disconnected and grounded). The E end of the transformer casing and the casing of the high-voltage dielectric loss bridge are grounded. After the a and b bushings on the three-phase converter transformer valve side are short-circuited, 10kV is applied, and the grid-side winding and the core clamp (disconnected and grounded) are short-circuited to obtain the signal.

[0053] The above tests are all tested using the positive connection method. The wiring diagram is as follows: Figure 2 . Whether the three earthing switches on the cathode, anode and non-tested converter transformer side of the valve side are disconnected has a great influence on the results (the earthing switch on the tested converter transformer side must be pulled open during the test). Table 1 shows the results of the dielectric loss capacitance test of the high YYB phase valve side to the core clamp, the valve side to the grid side and the core clamp when the three earthing switches are in different states. It should be noted that the test value can be controlled according to the dielectric loss value ≤ 0.006, and the change from the previous test value does not exceed 30% (the first use of the new test method can be compared between phases).

[0054] For the valve side winding test, the a and b bushings on the valve side of the three-phase converter transformer are short-circuited through an additional test line. Without removing the connection, the converter transformer is tested for windings. It should be noted that during the test, the cathode and anode grounding knives in the valve hall and the grounding knives on the converter transformer side are opened. The insulation resistance of the valve side winding to the grid side winding, the capacitance of the valve side winding to the grid side winding and the dielectric loss factor (tanδ) are measured to jointly assess the insulation of the valve side winding to the grid side winding.

[0055] In the embodiment of the present invention, the capacitance and dielectric loss factor test wiring of the valve side winding to the grid side winding and the core clamp adopts the positive connection method; when the valve side bushing insulation test (including main insulation and dielectric loss, capacitance test) is performed, 10kV is applied to the ends of the first bushing and the second bushing, and the signal is taken at the end screen. The positive connection method test is performed. Figure 2 As shown in the wiring diagram, when using an external standard capacitor Cn, a shielded wire with a shielded plug must be used for connection, and C / tgδ is placed in the instrument. The external high voltage level depends on the voltage level of the test sample Cx and the external standard capacitor Cn, and has nothing to do with the instrument. The instrument is at ground potential.

[0056] In the embodiment of the present invention, the capacitance and dielectric loss factor of the valve side winding to the grid side winding are obtained; specifically, a dielectric loss meter is used, the external standard capacitor of the dielectric loss meter is connected to the external standard capacitor, the test end of the dielectric loss meter is connected to the product to be tested, the positive poles of the external standard capacitor and the product to be tested are connected to the high-voltage output end, and the capacitance and dielectric loss are obtained by comparing the current difference between the product to be tested and the external standard capacitor. The dielectric loss tester uses a multi-channel tester with a model of AI6000LX and a capacity of 60nF.

[0057] In the embodiment of the present invention, the converter transformer manufacturer shall provide the capacitance and dielectric loss factor of the valve side winding to the grid side winding, the valve side winding to the core clamp, and the valve side winding to the grid side winding and the core clamp in the factory test report; the converter transformer structure type and capacity have a great influence on the capacitance value, and the reference value of the dielectric loss meter capacity is recommended to be ≥60nf (10kV), and the insulation megohmmeter capacity should be ≥3mA (5kV); when the instrument capacity meets the requirements, attention should be paid to the test power supply voltage during the capacitance and dielectric loss test. If the power supply voltage is too low, it is easy to cause the test voltage to fail to rise to the specified value (10kV). External high voltage method can be used during the test.

[0058] For the valve side winding test, the a and b bushings on the valve side of the three-phase converter transformer are short-circuited by adding a test line. The converter transformer is tested for windings without removing the connection. It should be noted that during the test, the cathode ground knife C, the anode ground knife D, and the converter transformer side ground knife F in the valve hall are opened. The insulation resistance of the valve side winding to the grid side winding and the capacitance and dielectric loss factor (tanδ) of the valve side winding to the grid side winding are measured to jointly assess the insulation of the valve side winding to the grid side winding. During the measurement of this experiment, Jinan Panhua AI-6000KX automatic anti-interference precision dielectric loss measuring instrument was used for positive connection. The instrument successfully added the insulation resistance measurement function without changing the original measurement function. The wiring method for measuring insulation resistance is exactly the same as that for dielectric loss measurement. One wiring can measure both dielectric loss and insulation resistance.

[0059] To further verify the accuracy of the test results without disconnecting the leads, all the connections of the bushings on the valve side of one of the converter transformers were disconnected for comparison. The test data are shown in Table 2. The test data of the dielectric loss capacitance without disconnecting the leads is completely consistent with the test data of disconnecting all the leads of the bushings on the valve side. It can be used as a method for conducting on-site dielectric loss capacitance tests. The insulation resistance tests of the valve side to the grid side and the valve side to the core clamp were carried out without disconnecting the leads, and the test results were greater than 10GΩ.

[0060] In the present invention, the test wiring of the capacitance and dielectric loss factor (tgδ) of the valve side winding to the grid side winding and the core clamp adopts the positive connection method. The E end of the transformer casing and the casing of the high-voltage dielectric loss bridge are grounded. After the a and b bushings on the three-phase converter transformer valve side are all short-circuited, the voltage is increased to 10kV, and the grid side winding and the core clamp (disconnected from grounding) are short-circuited to obtain the signal. There is no need to disconnect the valve side bushing from the valve tower lightning arrester. When the insulation resistance between the valve side winding and the grid side winding is tested with the valve tower, the insulation resistance value does not drop significantly. The grounding knife switch connected to the valve group should be opened during the test. When conducting the valve side bushing insulation test (including main insulation and dielectric loss and capacitance tests), 10kV should be applied to the bushing end, and the signal should be taken at the end screen for positive connection testing.

[0061] The present invention adopts the positive connection method to measure the capacitance and dielectric loss factor of the converter transformer valve side winding to the grid side winding without disconnection. It can better improve work efficiency, reduce labor costs, and ensure the personal safety of operators, which is of great significance to the lean maintenance of converter stations in the future. It has the advantages of shortening the test time and reducing the high labor intensity and high risk caused by the test disassembly work.

[0062] The present invention is described in detail above, but the present invention is not limited to the above-mentioned embodiments. Various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. Many other changes and modifications can be made without departing from the concept and scope of the present invention. It should be understood that the present invention is not limited to specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A method for testing the dielectric loss factor of the valve-side bushing and winding of a converter transformer, characterized in that: include: The positive connection method is used for wiring the converter valve; Obtain the test insulation resistance of the valve side winding to the network test winding; Obtain the capacitance and dielectric loss factor of the valve-side winding to the grid-side winding; Test the valve side winding and the network test winding according to the test insulation resistance value, capacitance and dielectric loss factor; Obtain the test insulation resistance of the valve-side winding to the grid-measured winding; specifically, the test includes: applying 5000V of pressure after the first bushing and the second bushing on the three-phase converter transformer valve side are short-circuited, the grid-side winding is short-circuited, and the capacitive current and resistive current signals of the grid-side winding are obtained after the iron core and the clamp are short-circuited; The method of obtaining the capacitance and dielectric loss factor of the valve side winding to the grid side winding is specifically carried out by using a dielectric loss meter, wherein the external standard capacitor access terminal of the dielectric loss meter is connected to the external standard capacitor, the test terminal of the dielectric loss meter is connected to the product to be tested, the positive poles of the external standard capacitor and the product to be tested are connected to the high voltage output terminal, and the capacitance and dielectric loss are obtained by comparing the current difference between the product to be tested and the external standard capacitor.

2. The method according to claim 1, characterized in that The positive connection method is used for wiring the converter transformer valve; specifically, the positive connection method is used for wiring without disconnecting the leads, and the grounding terminals of the transformer casing and the casing of the high-voltage dielectric loss bridge are grounded; the first bushing and the second bushing on the three-phase converter transformer valve side are short-circuited through the accessory test line, the first bushing and the second bushing on the valve side are connected to the valve tower arrester, and the internal cathode grounding knife, anode grounding knife, and converter transformer side grounding knife are disconnected from the valve group.

3. The method according to claim 1, characterized in that The external standard capacitor and the product to be tested are connected to the dielectric loss meter using a shielded cable with a shielded plug.

4. The method according to claim 1, characterized in that: The dielectric loss tester is a multi-channel tester with a model of AI6000LX and a capacity of 60nF.

5. The method according to claim 1, characterized in that Obtain the capacitance and dielectric loss factor of the valve-side winding to the grid-side winding; specifically including: Test of capacitance and dielectric loss factor of valve side winding to grid side winding; Test of capacitance and dielectric loss factor of valve side winding to core clamp; Test the capacitance and dielectric loss factor of the valve side winding to the grid side winding and core clamps.

6. The method according to claim 1, characterized in that The test insulation resistance of the valve side winding to the grid test winding is obtained; specifically, the insulation resistance of the valve side winding to the grid side winding is used instead of the insulation resistance of the valve side winding to the grid side winding and the ground.

7. The method according to claim 1, characterized in that The dielectric loss value tested by the dielectric loss meter is ≤0.006, and the test value variation does not exceed 30%.

8. The method according to claim 1, characterized in that The dielectric loss meter capacity of the converter transformer valve is ≥60nf (10kV), and the insulation megohmmeter capacity is ≥3mA (5kV).

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