Method for verifying influence quantity of error test circuit and standard leakage current of three-phase combined transformer

Abstract

The invention discloses a three-phase combined transformer error test line and standard leakage current influence quantity verification method. The circuit comprises a high-voltage standard current transformer TAo, a high-voltage up-flow transformer SLQ, a high-voltage test transformer SYQ, a standard voltage transformer PTo, a tested voltage transformer PTx, a tested current transformer TAx, a voltage transformer calibrator TVJYY, a current transformer calibrator TAJYY, a secondary load Z of TAx and a secondary load Y of PTx. The PTx and the TAx form a three-phase combined mutual inductor, and the PTx and the TAx share a polarity end AP1; the high-voltage current winding of the SLQ, the high-voltage end A of the SYQ and the polar end A of the PTo are arranged between the polar end L1 of the TAo and the polar end AP1; the TVJYY is connected with the PTo and the PTx; and the TAJYY is connected with the TAo and the TAx. According to the invention, the error verification of the current transformer in the three-phase combined transformer can be accurately carried out in the state of applying high voltage, and the influence quantity of the three-phase standard combined transformer and the loop leakage current on the error verification of the high-voltage current transformer can be quantified.

Description

Technical Field

[0001] The invention belongs to the technical field of mutual inductor error testing, and relates to a three-phase combined mutual inductor error testing circuit and a standard leakage current influence quantity verification method. Background Art

[0002] In this field, JJG 1165-2019 "Three-phase combination transformer verification regulations" stipulates that the three-phase combination transformer needs to be subjected to a basic error test, and three-phase voltage and three-phase current need to be applied simultaneously, and the corresponding current transformer error test points are given. At the same time, JJG 1165-2019 "Three-phase combination transformer verification regulations" also mentions the verification circuit of the current transformer. The wiring should avoid placing the voltage transformer of the combination transformer between the high-voltage standard current transformer and the current transformer under test, and gives the corresponding current transformer basic error test wiring diagram of the three-phase Y-connected combination transformer composed of three current transformers.

[0003] But in fact, the current domestic combined transformer manufacturers connect the polarity ends of the voltage transformer and the polarity ends of the current transformer inside the combined transformer, which cannot be separated. Figure 1-Figure 2 The AP1 of the three-phase combination transformer shown is both the polarity end of the current transformer and the polarity end of the voltage transformer, that is, the three-phase combination transformer has the problem of common polarity end of the current transformer and the voltage transformer, which makes it difficult to carry out error verification according to the basic error test wiring diagram given in the above-mentioned JJG 1165-2019 "Verification Procedure for Three-Phase Combination Transformers". Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a three-phase combination transformer error test circuit and a standard leakage current influence verification method. The influence of leakage current on the entire test system is less than 1 / 3 of the standard current transformer error limit, and the current transformer error verification in the three-phase combination transformer can be accurately carried out under high voltage.

[0005] The present invention adopts the following technical solution.

[0006] The first aspect of the present invention provides a three-phase combined transformer error test circuit, including a high-voltage standard current transformer TAo, a high-voltage current boost transformer SLQ, a high-voltage test transformer SYQ, a standard voltage transformer PTo, a voltage transformer to be tested PTx, a current transformer to be tested TAX, a voltage transformer tester TV_JYY, a current transformer tester TA_JYY, a secondary load Z of TAX and a secondary load Y of PTx, wherein TAo, SLQ, SYQ, and PTo ​​constitute a three-phase standard combined transformer, PTx and TAX constitute a three-phase combined transformer, and PTx and TAX share a polarity terminal AP1;

[0007] The high voltage current winding of the SLQ, the high voltage terminal A of the SYQ and the polarity terminal A of the PTo are short-connected together as a common polarity terminal A of the high voltage, and are sequentially arranged between the polarity terminal L1 of the TAo and the polarity terminal AP1;

[0008] The TV_JYY is connected to PTo and PTx respectively; and the TA_JYY is connected to TAo and TAx respectively.

[0009] Preferably, the high-voltage primary winding of the TAo serves as a high-voltage shielding layer pb1, and the secondary winding serves as a grounding shielding layer pb2;

[0010] The high-voltage shielding layer pb1 is connected to the high-voltage terminal A of SYQ, so that the capacitive current on the high-voltage shielding layer pb1 to the ground, that is, the high-voltage capacitive leakage current i7 of Tao flows directly from the high-voltage terminal A of SYQ to pb2 to the ground. At this time, the test current on the high-voltage primary winding is i1.

[0011] Preferably, the high-voltage primary winding has n taps, namely L1, L2...Ln, and the secondary winding has n taps, namely K1, K2...Kn, so as to have various current transformation ratios to calibrate the measured current transformer error in combination transformers with different current transformation ratios.

[0012] Preferably, the high-voltage current winding of the SLQ is insulated from its input power winding, and a high-voltage current winding shielding layer and a low-voltage power winding shielding layer are not required.

[0013] Preferably, the SYQ increases the voltage and outputs the current i2 during the three-phase combined transformer error test, providing the excitation load current i3 of PTo, the primary excitation load current i4 of PTx, and the high-voltage capacitive leakage currents i7, i6 and i5 of TAo, TAx and SLQ.

[0014] Preferably, the SYQ also provides leakage currents i8 and i9 generated by stray capacitance of high-voltage and high-current wires through the air medium to the ground in the high-voltage loop composed of TAo, SLQ, SYQ, PTo, PTx, and TAX;

[0015] Among them, i8 does not flow into the primary winding of the standard current transformer TAo and the current transformer under test TAx, and does not produce additional error influence on the error check of the current transformer under test;

[0016] i9 is split into two leakage currents i91 and i92, which pass through the primary windings of TAo and TAx respectively, and finally converge into i9 and flow into the ground. The direction of the leakage current i91 flowing through the primary winding of TAo is opposite to the direction of the leakage current i92 flowing through TAx, which produces additional error in the error verification of the current transformer under test.

[0017] Preferably, the length of the connecting wire between the non-polarity terminals L2-Ln of the standard current transformer Tao and the non-polarity terminal AP2 of the current transformer TAx under test adopts the minimum value allowed in the test environment to reduce the distributed capacitance of the non-polarity terminal connecting wire to the ground.

[0018] Preferably, the high-voltage circuit uses a high-voltage, high-current cable with a shielding layer, and the shielding layer is connected to the high-voltage output A terminal of SYQ, so that the leakage current i9 on the shielding layer does not pass through the primary winding of TAo and TAx and becomes part of i8.

[0019] A second aspect of the present invention provides a method for verifying the influence of a standard leakage current on the error of a current transformer under test, the method comprising:

[0020] Step 1: Replace the current transformer TAX under test with a high-voltage standard current transformer TAoB, change the label of the high-voltage standard current transformer TAo in the three-phase standard combination transformer to TAoA, and remove the voltage transformer PTx under test, the voltage transformer tester TV_JYY, the current transformer tester TA_JYY, the secondary load Z of TAX and the secondary load Y of PTx;

[0021] Step 2: Use TAoA and TAoB, two high-voltage standard current transformers, to check the primary winding errors of each other under high voltage conditions and zero voltage or low voltage conditions;

[0022] The ratio error f1 and angle error δ1 are obtained under high pressure;

[0023] The ratio error f2 and the angle error δ2 are obtained under zero voltage or low voltage conditions;

[0024] Step 3: Calculate the ratio error change f3 = (f2 - f1) / 2 and the angle error change δ3 = (δ2 - δ1) / 2 of the three-phase standard combination transformer under high voltage;

[0025] Step 4: If f3 and δ3 are both less than 1 / 3 of the corresponding standard current transformer error limit, it is considered that the leakage current of the three-phase standard combination transformer and its circuit meets the requirements of the high-voltage standard current transformer for measurement transmission; otherwise, it is considered that the leakage current of the three-phase standard combination transformer and its circuit will bring a large error impact to the error verification of the high-voltage current transformer in the three-phase combination transformer under test, and even the qualified three-phase combination transformer under test will be judged as unqualified.

[0026] Preferably, the A-phase, B-phase and C-phase high-voltage standard current transformers in the three-phase standard combination transformer adopt the same manufacturing process, materials and parameters.

[0027] Compared with the prior art, the beneficial effects of the present invention include at least:

[0028] The test circuit leakage currents i5, i7 and i8 of the present invention are decoupled from the test current i1, thereby eliminating the influence of the leakage current generated by the distributed capacitance between components and components and between components and ground in the test circuits of each phase on the verification error of the current transformer TAx under test in the three-phase combination transformer under high-voltage error test.

[0029] The test circuit of the present invention realizes the decoupling of the excitation load current i4 of the tested voltage transformer PTx, the output current i2 of the step-up transformer (high-voltage test transformer SYQ), and the excitation load current i3 generated by the standard voltage transformer PTo under the high-voltage state of the test from the test current i1 in the current transformer error verification circuit, thereby eliminating the influence of the test current i1 on the primary winding of the tested current transformer TAx and the high-voltage standard current transformer TAo on the verification error of the three-phase combination transformer.

[0030] The present invention can also verify the influence of leakage current of a three-phase standard combination transformer on errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the front view of the three-phase combination transformer under test;

[0032] Figure 2 It is the top view of the three-phase combined transformer under test;

[0033] Figure 3 This is a schematic diagram of the error test circuit of the three-phase combination transformer of the present invention;

[0034] Figure 4 This is a schematic diagram for verifying the standard leakage current influence quantity of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0036] Embodiment 1 of the present invention provides a three-phase combined mutual inductor error test circuit, which performs error tests on a three-phase standard combined mutual inductor and a three-phase combined mutual inductor under test, such as Figure 3As shown, TAo, SLQ, SYQ, and PTo ​​constitute one phase of a three-phase standard combination transformer, and a total of three phases are required. The figure shows one phase, and the actual calibration is to calibrate three phases. The test circuit specifically includes a high-voltage standard current transformer TAo, a high-voltage current boost transformer SLQ, a high-voltage test transformer SYQ, a standard voltage transformer PTo, a voltage transformer to be tested PTx, a current transformer to be tested TAX, a voltage transformer tester TV_JYY, a current transformer tester TA_JYY, a secondary load Z of TAX, and a secondary load Y of PTx, wherein PTx and Tax constitute a three-phase combination transformer, and PTx and Tax share a polarity terminal AP1;

[0037] More preferably, Figure 3 The circuit shown verifies the error between one phase of the three-phase standard combination transformer composed of TAo, SLQ, SYQ, and PTo ​​and one phase of the current transformer TAX under test, wherein the phase difference of the three-phase standard combination transformer is consistent with the phase difference of the current transformer TAX under test; Figure 3 It is one of the phases of the three-phase standard combination transformer, and the three groups are the same. It is used as the standard and the corresponding phase of the three-phase combination transformer to be tested for verification; the transformer tester TA_JYY also has three phases, and can display the measured error value on the display interface of the instrument. The improvement of the present invention is mainly to verify the error of the current transformer under test; the error of the voltage transformer is also verified at the same time, but the conventional technology of the industry is adopted. The voltage transformer tester TV_JYY can measure the error of the voltage transformer under test and display it on the instrument interface.

[0038] The high-voltage current winding of the high-voltage boost transformer SLQ, the high-voltage terminal A of the high-voltage test transformer SYQ, and the polarity terminal A of the standard voltage transformer PTo are short-circuited together as the common polarity terminal A of the high voltage, and are placed between the polarity terminal L1 of the high-voltage standard current transformer TAo and the polarity terminal AP1 of the voltage transformer PTx under test and the polarity terminal AP1 of the current transformer TAX under test. Instead of placing the booster, standard voltage transformer, and voltage transformer under test at the non-polarity end of the current transformer under test as specified in the JJG1165-2019 three-phase combination transformer verification procedure.

[0039] Further preferably, the high-voltage primary winding (L1, L2~Ln) of the high-voltage standard current transformer TAo is made into a high-voltage shielding layer pb1, and the high-voltage shielding layer pb1 is connected to the high-voltage terminal A of the high-voltage test transformer SYQ, so that the capacitive current i7 on the high-voltage shield to the ground flows directly from the high-voltage terminal A of the high-voltage test transformer SYQ to the grounding shielding layer pb2 of the secondary winding to the ground, and does not pass through the high-voltage primary winding of the high-voltage standard current transformer TAo. At this time, the test current on the high-voltage winding is i1;

[0040] The secondary winding (K1, K2~Kn) of the high-voltage standard current transformer TAo is used as the grounded shielding layer pb2, so that the capacitive current on the high-voltage shielding layer flows i7 to the low-voltage shielding layer without flowing into the secondary winding (K1, K2~Kn) of the high-voltage standard current transformer TAo.

[0041] Since the current transformer calibration requires the use of a standard current transformer with the same current transformation ratio, the high-voltage primary winding of the high-voltage standard current transformer TAo has multiple taps (L1, L2~Ln), and the secondary winding also has multiple taps (K1, K2~Kn), so that it has various current transformation ratios to calibrate the measured current transformer error in the combination transformer with different current transformation ratios.

[0042] Further preferably, the high-voltage winding of the high-voltage current boost transformer SLQ only needs to have sufficient withstand voltage insulation with respect to the input power winding, and there is no need to make a dedicated high-voltage winding shielding layer and a low-voltage shielding layer for the power winding. Even if the high-voltage winding of the high-voltage current boost transformer SLQ has a leakage current i5 to the ground and to the power winding, it does not affect the primary current i1 of the high-voltage standard current transformer TAo and the current transformer TAx under test.

[0043] During the current transformer error test, the high-voltage test transformer SYQ increases the voltage, and the SYQ output current is i2; according to Kirchhoff's current law, it can be known that the vector amplitude of i2 is equal to the amplitude of the vector sum of i3, i4, i5, i6, i7, i8 and i9, and the vector direction of i2 is opposite to the vector sum direction of i3, i4, i5, i6, i7, i8 and i9. It can be considered that i2 and i3, i4, i5, i6, i7, i8 and i9 cancel each other out.

[0044] The high voltage test transformer SYQ provides the standard voltage transformer PTo excitation current i3;

[0045] The high-voltage test transformer SYQ provides the excitation load current i4 of the voltage transformer PTx under test, including the excitation current and the secondary winding load current;

[0046] The high-voltage test transformer SYQ provides the high-voltage capacitive leakage currents i7, i6, i5 of the high-voltage standard current transformer TAo, the current transformer under test TAx and the current boost transformer SLQ;

[0047] The high-voltage test transformer SYQ also provides leakage currents i8 and i9 generated by the stray capacitance of the high-voltage and high-current wires in the entire high-voltage circuit through the air medium to the ground.

[0048] i8 does not enter the calibration loop of the current transformer, so no additional error influence will be generated on the error calibration of the current transformer.

[0049] i9 will split into two currents i91 and i92 passing through the primary winding of TAo and TAx respectively, and finally converge into i9 and flow into the ground. The direction of the leakage current i91 flowing through the primary winding of TAo is opposite to the direction of the leakage current i92 flowing through TAx. Since the test current flowing into the primary winding of the standard current transformer is the vector sum of i1 and i91, and the test current flowing into the primary winding of the current transformer under test is the vector sum of i1 and i92, the primary winding current of the standard current transformer TAo and the primary winding current of the current transformer under test TAx are not equal, which will cause additional error to the error check of the current transformer under test.

[0050] How to reduce i9 is the key to reduce the additional impact of high voltage leakage current on error checking:

[0051] i1 is the test current of the current transformer. Ideally, i1 flowing through the primary winding of the standard current transformer and the current transformer under test should be the same.

[0052] The currents i2, i3, i4, i5, i6, i7, and i8 generated under high voltage do not flow through the primary windings of the standard current transformer and the current transformer under test, and therefore do not change the primary current i1 of the standard current transformer and the current transformer under test, thereby having no effect on the calibration of the current transformer under test.

[0053] i9 is the leakage current of the non-polar end line, which will change the primary current i1 of the standard current transformer and the current transformer under test, and will affect the error check. Therefore, the size of i9 should be reduced as much as possible. There are two ways to reduce it.

[0054] 1) The verification process is carried out in the laboratory. The non-polar short-circuit test wire is as short as possible, so that the distributed capacitance of the non-polar end connecting wire to the ground can be reduced, thereby reducing the i9 leakage current, and then reducing the error impact of the high-voltage leakage current on the verification, so that the error of the current transformer under test can be accurately tested. Therefore, the length of the connecting wire between the non-polar end L2~Ln of the standard current transformer TAo and the non-polar end AP2 of the current transformer under test TAx can be reduced by reducing the length of the connecting wire and increasing the air insulation distance to the ground.

[0055] 2) A high-voltage, high-current cable with a shielding layer can be used, and the shielding layer is connected to the high-voltage output A terminal of the high-voltage test transformer, so that the leakage current on the shielding layer does not pass through the primary winding of the standard current transformer TAo and the current transformer under test TAx, and the leakage current on the shielding layer becomes part of i8.

[0056] In the error test circuit, i6 is considered to be the source of the error influence on the measured current transformer TAX under high voltage state, and is included in the error of the measured current transformer TAX.

[0057] Embodiment 2 of the present invention provides a method for verifying the influence of a standard leakage current on an error, and the test method includes:

[0058] Step 1: Replace the current transformer TAX with another high-voltage standard current transformer TAoB, change the original standard current transformer TAo to TAoA, remove the voltage transformer PTx, voltage transformer tester TV_JYY, current transformer tester TA_JYY, secondary load Z of TAX and secondary load Y of PTx, as shown in the following figure: Figure 4 As shown;

[0059] Right now Figure 3 and Figure 4 These are two completely independent experiments. Figure 4 The voltage transformer PTx to be tested, the voltage transformer tester TV_JYY, the current transformer tester TA_JYY, the secondary load Z of TAX and the secondary load Y of PTx are not required.

[0060] Figure 4 The circuit shown does not have the current transformer TAX under test. There are three groups of three-phase standard combination transformers, A, B and C. One group is used as a standard transformer to calibrate the other two groups. The error obtained is the error influence of the three-phase standard current transformer at high voltage.

[0061] In addition, the leakage current will not have any influence on the voltage transformer error, so there is no need to test the influence of the leakage current on the error of the voltage transformer being tested.

[0062] The A-phase, B-phase and C-phase high-voltage standard current transformers in the three-phase standard combination transformer are designed with the same technical means and manufactured at the same time, so the manufacturing process, materials and parameters of the three are the same.

[0063] Step 2: Use the primary windings of two standard current transformers, TAoA and TAoB, to check the errors between each other under high voltage and zero voltage conditions;

[0064] The secondary winding of the standard voltage transformer PTo is connected to a voltmeter V for monitoring the primary winding high voltage of the high voltage standard current transformer.

[0065] The ratio error f1 and angle error δ1 are obtained under high pressure;

[0066] The ratio error f2 and the angle error δ2 are obtained under zero voltage state;

[0067] Step 3: The ratio error change of the standard current transformer under high voltage is f3 = (f2-f1) / 2, and the angle error change is δ3 = (δ2-δ1) / 2.

[0068] For example, TAoA can be used to check TAoB under high pressure to obtain errors f1 and δ1, such as f1 = -0.05%, δ1 = 1.2';

[0069] The errors f2 and δ2 can be obtained by using TAoA to check TAoB under low pressure and high pressure conditions, for example, f2 = -0.002%, δ2 = 0.03′;

[0070] Error influence ratio difference: f3 = (f2-f1) / 2 = (-0.002+0.05) / 2% = 0.024%;

[0071] Error influence angle difference: δ3 = (δ2-δ1) / 2 = (0.03-1.2) / 2 = -0.585′;

[0072] Step 4: If f3 and δ3 are both less than 1 / 3 of the standard current transformer error limit, it is considered that the standard current transformer and the loop leakage current meet the requirements of the high-voltage standard current transformer for measurement transmission. Otherwise, it will bring a large error impact to the error verification of the high-voltage current transformer in the three-phase combination transformer under test, and even judge the qualified three-phase combination transformer as unqualified. In this case, this three-phase standard combination transformer cannot be used as a standard to verify the three-phase combination transformer under test.

[0073] Based on the above steps, phase calibration can be carried out between phases A and B, phases B and C, and phases C and A to obtain the high-voltage error influence of each phase of the high-voltage standard current transformer in the three-phase standard combination transformer. Figure 4 In TAOB and TAoA, A is verified relative to B.

[0074] Compared with the prior art, the beneficial effects of the present invention include at least:

[0075] The test circuit leakage currents i5, i7 and i8 of the present invention are decoupled from the test current i1, thereby eliminating the influence of the leakage current generated by the distributed capacitance between components and components and between components and ground in the test circuits of each phase on the verification error of the current transformer TAx under test in the three-phase combination transformer under high-voltage error test.

[0076] The test circuit of the present invention realizes the decoupling of the excitation load current i4 of the tested voltage transformer PTx, the output current i2 of the step-up transformer (high-voltage test transformer SYQ), and the excitation load current i3 generated by the standard voltage transformer PTo under the high-voltage state of the test from the test current i1 in the current transformer error verification circuit, thereby eliminating the influence of the test current i1 on the primary winding of the tested current transformer TAx and the high-voltage standard current transformer TAo on the verification error of the three-phase combination transformer.

[0077] The present invention can also verify the influence of leakage current of a three-phase standard combination transformer on errors.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A three-phase combined transformer error test circuit, comprising a high-voltage standard current transformer TAo, a high-voltage current boost transformer SLQ, a high-voltage test transformer SYQ, a standard voltage transformer PTo, a voltage transformer to be tested PTx, a current transformer to be tested TAX, a voltage transformer tester TV_JYY, a current transformer tester TA_JYY, a secondary load Z of TAX and a secondary load Y of PTx, wherein TAo, SLQ, SYQ and PTo ​​constitute a three-phase standard combined transformer, PTx and TAX constitute a three-phase combined transformer, PTx and TAX share a polarity terminal AP1, characterized in that: The high voltage current winding of the SLQ, the high voltage terminal A of the SYQ and the polarity terminal A of the PTo are short-connected together as a common polarity terminal A of the high voltage, and are sequentially arranged between the polarity terminal L1 of the TAo and the polarity terminal AP1; The TV_JYY is connected to PTo and PTx respectively; TA_JYY is connected to TAo and TAx respectively.

2. A three-phase combined mutual inductor error test circuit according to claim 1, characterized in that: The high-voltage primary winding of the TAo is used as a high-voltage shielding layer pb1, and the secondary winding is used as a grounding shielding layer pb2; The high-voltage shielding layer pb1 is connected to the high-voltage terminal A of SYQ, so that the capacitive current on the high-voltage shielding layer pb1 to the ground, that is, the high-voltage capacitive leakage current i7 of Tao flows directly from the high-voltage terminal A of SYQ to pb2 to the ground. At this time, the test current on the high-voltage primary winding is i1.

3. A three-phase combined mutual inductor error test circuit according to claim 2, characterized in that: The high-voltage primary winding has n taps, namely L1, L2...Ln, and the secondary winding has n taps, namely K1, K2...Kn, so as to have various current transformation ratios to calibrate the error of the measured current transformer in the combination transformer with different current transformation ratios.

4. A three-phase combined mutual inductor error test circuit according to claim 1, characterized in that: The high-voltage current winding of the SLQ and its input power winding are insulated against voltage, and a high-voltage current winding shielding layer and a low-voltage power winding shielding layer are not required.

5. A three-phase combined mutual inductor error test circuit according to claim 1, characterized in that: The SYQ increases the voltage and outputs the current i2 during the three-phase combined transformer error test, providing the excitation load current i3 of PTo, the primary excitation load current i4 of PTx, and the high-voltage capacitive leakage currents i7, i6 and i5 of TAo, TAx and SLQ.

6. A three-phase combined mutual inductor error test circuit according to claim 5, characterized in that: The SYQ also provides leakage currents i8 and i9 generated by the stray capacitance of the high-voltage and high-current wires in the high-voltage circuit composed of TAo, SLQ, SYQ, PTo, PTx, and TAX through the air medium to the ground; Among them, i8 does not flow into the primary winding of the standard current transformer TAo and the current transformer TAx under test, and does not produce additional error influence on the error check of the current transformer under test; i9 is split into two leakage currents i91 and i92, which pass through the primary windings of TAo and TAx respectively, and finally converge into i9 and flow into the ground. The direction of the leakage current i91 flowing through the primary winding of TAo is opposite to the direction of the leakage current i92 flowing through TAx, which produces additional error in the error verification of the current transformer under test.

7. A three-phase combined mutual inductor error test circuit according to claim 6, characterized in that: The length of the connecting wire between the non-polarity terminals L2-Ln of the standard current transformer Tao and the non-polarity terminal AP2 of the current transformer TAx under test adopts the minimum value allowed in the test environment to reduce the distributed capacitance of the non-polarity terminal connecting wire to the ground.

8. A three-phase combined mutual inductor error test circuit according to claim 6, characterized in that: The high-voltage circuit uses a high-voltage and high-current cable with a shielding layer, and the shielding layer is connected to the high-voltage output A terminal of SYQ, so that the leakage current i9 on the shielding layer does not pass through the primary winding of TAo and TAx and becomes a part of i8.

9. A method for verifying the influence of a standard leakage current, used to verify the influence of the leakage current of a three-phase standard combination transformer on the error of a current transformer under test, using the circuit described in any one of claims 1 to 8, characterized in that: The method comprises: Replace the current transformer TAX under test with a high-voltage standard current transformer TAoB, change the label of the high-voltage standard current transformer TAo in the three-phase standard combination transformer to TAoA, and remove the voltage transformer PTx under test, the voltage transformer tester TV_JYY, the current transformer tester TA_JYY, the secondary load Z of TAX and the secondary load Y of PTx; The primary windings of two high-voltage standard current transformers, TAoA and TAoB, are used to check the errors of each other under high voltage and zero voltage or low voltage conditions: the ratio error f1 and angle error δ1 are obtained under high voltage conditions; the ratio error f2 and angle error δ2 are obtained under zero voltage or low voltage conditions; Calculate the ratio error change f3 = (f2 - f1) / 2 and the angle error change δ3 = (δ2 - δ1) / 2 of the three-phase standard combination transformer under high voltage; If f3 and δ3 are both less than 1 / 3 of the corresponding standard current transformer error limit, it is considered that the leakage current of the three-phase standard combination transformer and its circuit meets the requirements of the high-voltage standard current transformer for measurement transmission; otherwise, it is considered that the leakage current of the three-phase standard combination transformer and its circuit will bring a large error influence to the error verification of the high-voltage current transformer in the three-phase combination transformer under test, and even the qualified three-phase combination transformer under test will be judged as unqualified.

10. A method for verifying the influence of standard leakage current according to claim 9, characterized in that: The A-phase, B-phase and C-phase high-voltage standard current transformers in the three-phase standard combination transformer adopt the same manufacturing process, materials and parameters.

Images