Low-frequency transformer performance testing system and method

Abstract

The present invention provides a low-frequency transformer performance testing system and method, comprising a power supply circuit connected to a tested transformer; the power supply circuit provides test power to the tested transformer; a mutual inductor circuit connected to the power supply circuit, the tested transformer, and a detection circuit; and a performance test result of the tested transformer obtained through the detection circuit. The performance test result includes at least one of the following: the tested transformer's induced withstand voltage, the tested transformer's no-load loss and no-load current, the tested transformer's load loss and impedance voltage, and the tested transformer's zero-sequence impedance. Using this technology to conduct low-frequency transformer performance testing can ensure the accuracy of the test results while reducing the cost of low-frequency transformer performance testing.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer testing, and in particular to a low-frequency transformer performance testing system and method. Background Art

[0002] Low-frequency transmission is a new type of power transmission method. By lowering the system operating frequency, on the one hand, the line inductance decreases as the frequency decreases, which greatly reduces the impedance of the transmission line and effectively shortens the electrical distance of the line; on the other hand, the line capacitance increases as the frequency decreases, which can reduce the reactive power charged by the cable line and greatly improve the transmission capacity of the line.

[0003] Transformers are key components in low-frequency power transmission systems, using the principle of electromagnetic induction to change AC voltage. Changing the transformer's frequency also alters performance parameters such as no-load losses and current, load losses, and impedance voltage. Since today's transformers primarily operate at 50Hz, the majority of test subsystems also operate at 50Hz. Testing the performance parameters of low-frequency transformers (i.e., transformers with frequencies below 50Hz) requires a correspondingly matched test system.

[0004] However, setting up a low-frequency transformer performance test system is time-consuming and expensive. Furthermore, the current transformers (CTs) and voltage transformers (PTs) in the test system also use electromagnetic induction to measure current and voltage. Therefore, they are affected by frequency similarly to transformers. When the frequency decreases, the measurement deviation of the CTs and PTs increases, resulting in inaccurate transformer performance test results. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a low-frequency transformer performance testing system and method for performing an induced withstand voltage test, a no-load loss and no-load current test, a load loss and impedance voltage test, and a zero-sequence impedance test on a low-frequency transformer, thereby ensuring the accuracy of the low-frequency transformer performance test results while reducing the cost of the low-frequency transformer performance test.

[0006] In a first aspect, an embodiment of the present invention provides a low-frequency transformer performance testing system, the system comprising a power supply circuit, a transformer circuit, a detection circuit and a test transformer; the power supply circuit is connected to the test transformer; the power supply circuit provides test power for the test transformer; the transformer circuit is respectively connected to the power supply circuit, the test transformer and the detection circuit; the transformer circuit comprises a current transformer, and the operating frequency of the test transformer is less than the operating frequency of the current transformer; or, the transformer circuit comprises a current transformer and a voltage transformer, the operating frequency of the current transformer is equal to the operating frequency of the voltage transformer, and the operating frequency of the test transformer is less than the operating frequency of the current transformer or the voltage transformer; the rated operating magnetic flux density of the current transformer satisfies a first preset condition; and the rated operating magnetic flux density of the voltage transformer satisfies a second preset condition.

[0007] As a possible implementation, the power supply circuit includes an alternating current power supply, a voltage regulator and an intermediate transformer; the inlet side of the voltage regulator is connected to the alternating current power supply; the outlet side of the voltage regulator is connected to the low-voltage side of the intermediate transformer; the high-voltage side of the intermediate transformer provides an inductive withstand voltage test power supply for the tested transformer; the high-voltage side of the intermediate transformer is connected to the low-voltage side of the tested transformer; the transformer circuit includes a current transformer and a voltage transformer; the primary side of the current transformer is connected in series between the high-voltage side of the intermediate transformer and the low-voltage side of the tested transformer; the primary side of the voltage transformer is connected in parallel with the low-voltage side of the tested transformer; the detection circuit includes an ammeter and a voltmeter; the ammeter is connected to the secondary side of the current transformer; and the voltmeter is connected to the secondary side of the voltage transformer.

[0008] As a possible implementation, the power supply circuit includes a variable frequency power supply; the outlet side of the variable frequency power supply is connected to the low-voltage side of the tested transformer; the outlet side of the variable frequency power supply provides the tested transformer with no-load loss and no-load current test power supply; the transformer circuit includes a current transformer and a voltage transformer; the primary side of the current transformer is connected in series between the outlet side of the variable frequency power supply and the low-voltage side of the tested transformer; the primary side of the voltage transformer is connected in parallel with the low-voltage side of the tested transformer; the detection circuit includes a power analyzer; the power analyzer is respectively connected to the secondary side of the current transformer and the secondary side of the voltage transformer.

[0009] As a possible implementation, the power supply circuit includes a variable frequency power supply; the outlet side of the variable frequency power supply is connected to the high voltage side of the tested transformer; the outlet side of the variable frequency power supply provides the tested transformer with load loss and impedance voltage test power; the transformer circuit includes a current transformer and a voltage transformer; the primary side of the current transformer is connected in series between the outlet side of the variable frequency power supply and the high voltage side of the tested transformer; the primary side of the voltage transformer is connected in parallel with the high voltage side of the tested transformer; the detection circuit includes a power analyzer; the power analyzer is respectively connected to the secondary side of the current transformer and the secondary side of the voltage transformer.

[0010] As a possible implementation, the power supply circuit includes a variable frequency power supply; the outlet side of the variable frequency power supply is connected to the low-voltage side of the tested transformer; the outlet side of the variable frequency power supply provides a zero-sequence impedance test power supply for the tested transformer; the transformer circuit includes a current transformer; the primary side of the current transformer is connected in series between the outlet side of the variable frequency power supply and the low-voltage side of the tested transformer; the detection circuit includes a power analyzer and a multimeter; the power analyzer is connected to the secondary side of the current transformer; and the multimeter is connected to the low-voltage side of the tested transformer.

[0011] As a possible implementation, the operating frequencies of the voltage regulator, the intermediate transformer, the current transformer, and the voltage transformer are equal; and the operating frequency of the tested transformer is lower than the operating frequency of the voltage regulator, the intermediate transformer, the current transformer, or the voltage transformer.

[0012] As a possible implementation, the operating frequency of the variable frequency power supply includes the operating frequency of the tested transformer; the operating frequency of the current transformer is equal to the operating frequency of the voltage transformer; and the operating frequency of the tested transformer is less than the operating frequency of the current transformer or the voltage transformer.

[0013] As a possible implementation, the ratio between the operating frequency of the current transformer and the operating frequency of the tested transformer is n; or, the operating frequency of the current transformer is equal to the operating frequency of the voltage transformer, and the ratio between the operating frequency of the current transformer or the voltage transformer and the operating frequency of the tested transformer is n; wherein n≥2.

[0014] As a possible implementation, the first preset condition includes at least: the rated operating magnetic flux of the current transformer ≤ a first preset magnetic flux threshold; the second preset condition includes at least: the rated operating magnetic flux of the voltage transformer ≤ a second preset magnetic flux threshold.

[0015] In a second aspect, an embodiment of the present invention further provides a low-frequency transformer performance test method, which is applied to the above-mentioned low-frequency transformer performance test system; the method comprises: if the transformer circuit includes the current transformer, then according to the first preset condition and the test current of the tested transformer, the rated current of the primary side of the current transformer is determined; according to the determined rated current, the corresponding current is input to the primary side of the current transformer; if the transformer circuit includes the current transformer and the voltage transformer, then according to the first preset condition and the test current of the tested transformer, the rated current of the primary side of the current transformer is determined; according to the second preset condition and the test voltage of the tested transformer, the rated current of the primary side of the current transformer is determined. the rated voltage of the primary side of the voltage transformer; inputting a corresponding current into the primary side of the current transformer according to the determined rated current, and inputting a corresponding voltage into the primary side of the voltage transformer according to the determined rated voltage; obtaining a performance test result of the tested transformer through the detection circuit; wherein, the performance test result includes at least one of the following: the induced withstand voltage of the tested transformer, the no-load loss and no-load current of the tested transformer, the load loss and impedance voltage of the tested transformer, and the zero-sequence impedance of the tested transformer; wherein, the performance test time of the induced withstand voltage of the tested transformer is determined according to the operating frequency of the tested transformer and the operating frequency of the current transformer or the voltage transformer.

[0016] The low-frequency transformer performance testing system and method provided by the embodiment of the present invention comprises a power supply circuit connected to a tested transformer; the power supply circuit provides a test power supply for the tested transformer; a mutual inductor circuit is respectively connected to the power supply circuit, the tested transformer, and the detection circuit; and a performance test result of the tested transformer is obtained through the detection circuit; wherein the performance test result includes at least one of the following: the induced withstand voltage of the tested transformer, the no-load loss and no-load current of the tested transformer, the load loss and impedance voltage of the tested transformer, and the zero-sequence impedance of the tested transformer. The above-mentioned technology is used to carry out performance testing of low-frequency transformers (such as induced withstand voltage test, no-load loss and no-load current test, load loss and impedance voltage test, zero-sequence impedance test, etc.), which can ensure the accuracy of the low-frequency transformer performance test results while reducing the cost of low-frequency transformer performance testing.

[0017] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purposes and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic structural diagram of a low-frequency transformer performance testing system provided by an embodiment of the present invention;

[0021] Figure 2 This is a circuit diagram of an inductive voltage withstand test subsystem according to an embodiment of the present invention;

[0022] Figure 3 This is a circuit diagram of a no-load loss and no-load current test subsystem in an embodiment of the present invention;

[0023] Figure 4 This is a circuit diagram of a load loss and impedance voltage test subsystem according to an embodiment of the present invention;

[0024] Figure 5 This is a circuit diagram of a zero-sequence impedance test subsystem according to an embodiment of the present invention;

[0025] Figure 6 A schematic flow chart of a low-frequency transformer performance testing method provided by an embodiment of the present invention;

[0026] Figure 7 A schematic flow chart of another low-frequency transformer performance testing method provided by an embodiment of the present invention.

[0027] Icons: 100-power supply circuit; 200-transformer circuit; 300-detection circuit; 1-voltage regulator; 2-intermediate transformer; 3-current transformer; 4-voltage transformer; 5-test transformer; 6-ammeter; 7-voltmeter; 8-variable frequency power supply; 9-power analyzer; 10-multimeter. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] Currently, low-frequency transformer performance testing systems require a long construction period and are expensive. Furthermore, the current transformers (CTs) and voltage transformers (PTs) in the testing system also use the principle of electromagnetic induction to measure current and voltage. Therefore, the CTs and PTs are affected by frequency similarly to transformers. When the frequency decreases, the measurement deviations of the CTs and PTs increase, resulting in inaccurate transformer performance test results. Based on this, the present invention provides a low-frequency transformer performance testing system and method that can be used to perform induced withstand voltage tests, no-load loss and no-load current tests, load loss and impedance voltage tests, and zero-sequence impedance tests on low-frequency transformers, thereby ensuring the accuracy of low-frequency transformer performance test results while reducing the cost of low-frequency transformer performance testing.

[0030] To facilitate understanding of this embodiment, a low-frequency transformer performance testing system disclosed in an embodiment of the present invention is first introduced in detail.

[0031] See also Figure 1 As shown, the low-frequency transformer performance test system includes a power supply circuit 100, a mutual inductor circuit 200, a detection circuit 300 and a test transformer 5; the power supply circuit 100 is connected to the test transformer 5; the power supply circuit 100 provides a test power supply for the test transformer 5; the mutual inductor circuit 200 is respectively connected to the power supply circuit 100, the test transformer 5 and the detection circuit 300.

[0032] As a possible implementation, for example Figures 2 to 4 The above-mentioned transformer circuit 200 may include a current transformer 3 and a voltage transformer 4. The operating frequency of the current transformer 3 is equal to the operating frequency of the voltage transformer 4 (e.g., both are 50 Hz), and the operating frequency of the test transformer 5 is less than the operating frequency of the current transformer 3 or the voltage transformer 4 (e.g., less than 50 Hz). This embodiment is generally applicable to performing induced withstand voltage tests, no-load loss and no-load current tests, load loss and impedance voltage tests, temperature rise tests, etc. on low-frequency transformers. Based on this, the ratio between the operating frequency of the current transformer 3 or the voltage transformer 4 and the operating frequency of the test transformer 5 is recorded as n, wherein, when performing the induced withstand voltage test on the test transformer 5, n≥2; when performing other tests on the test transformer 5 (e.g., no-load loss and no-load current tests, load loss and impedance voltage tests, temperature rise tests, etc.), n>1.

[0033] As other possible implementations, for example Figure 5The transformer circuit 200 may include a current transformer 3, and the operating frequency of the transformer under test 5 may be lower than the operating frequency of the current transformer 3 (e.g., lower than 50 Hz). This embodiment is generally applicable to performing zero-sequence impedance tests on low-frequency transformers, for example. To further ensure test effectiveness, the ratio between the operating frequency of the current transformer 3 and the operating frequency of the transformer under test 5 may be denoted as n. When performing a zero-sequence impedance test on the transformer under test 5, n>1.

[0034] To ensure the test accuracy of the low-frequency transformer performance test system, especially the measurement accuracy of the transformer circuit, it is necessary to ensure that the rated working magnetic flux of the transformer meets certain preset conditions, such as: the rated working magnetic flux of the current transformer in the transformer circuit meets the first preset condition, and the rated working magnetic flux of the voltage transformer in the transformer circuit meets the second preset condition.

[0035] The first preset condition is different from the second preset condition, and can be specifically determined according to the required test accuracy, and is not limited thereto.

[0036] The low-frequency transformer performance testing system provided by the embodiments of the present invention comprises a power supply circuit connected to a transformer under test; the power supply circuit provides test power to the transformer under test; and a mutual inductor circuit connected to the power supply circuit, the transformer under test, and a detection circuit. This system can be used to perform low-frequency transformer performance tests (such as induced withstand voltage tests, no-load loss and no-load current tests, load loss and impedance voltage tests, and zero-sequence impedance tests), ensuring the accuracy of low-frequency transformer performance test results while reducing the cost of low-frequency transformer performance testing.

[0037] In actual application, the low-frequency transformer performance testing system can be designed to include one or more subsystems.

[0038] For example, when performing an inductive withstand voltage test on a low-frequency transformer, the low-frequency transformer performance test system can be designed to include an inductive withstand voltage test subsystem. Figure 2 The power supply circuit 100 can be designed to include an alternating power supply ( Figure 2The transformer circuit 200 is not shown in the figure), the voltage regulator 1 and the intermediate transformer 2, the inlet side of the voltage regulator 1 is connected to the alternating power supply, the outlet side of the voltage regulator 1 is connected to the low-voltage side of the intermediate transformer 2, the high-voltage side of the intermediate transformer 2 provides the induction withstand voltage test power supply for the tested transformer 5, and the high-voltage side of the intermediate transformer 2 is connected to the low-voltage side of the tested transformer 5; the above-mentioned mutual inductor circuit 200 can be designed to include a current transformer 3 and a voltage transformer 4, the primary side of the current transformer 3 is connected in series between the high-voltage side of the intermediate transformer 2 and the low-voltage side of the tested transformer 5, and the voltage transformer 4 is connected in parallel with the low-voltage side of the tested transformer 5; the above-mentioned detection circuit 300 can be designed to include an ammeter 6 and a voltmeter 7, the ammeter 6 is connected to the secondary side of the current transformer 3, and the voltmeter 7 is connected to the secondary side of the voltage transformer 4; wherein, the operating frequencies of the voltage regulator 1, the intermediate transformer 2, the current transformer 3 and the voltage transformer 4 are equal (for example, all are 50 Hz), and the operating frequency of the tested transformer 5 is less than 1 / 2 of the operating frequencies of the voltage regulator 1, the intermediate transformer 2, the current transformer 3 and the voltage transformer 4 (for example, less than 25 Hz).

[0039] For example, when performing no-load loss and no-load current tests on a low-frequency transformer, the low-frequency transformer performance test system can be designed to include no-load loss and no-load current test subsystems. Figure 3 The power supply circuit 100 can be designed to include a variable frequency power supply 8, the outlet side of the variable frequency power supply 8 is connected to the low voltage side of the test transformer 5, and the outlet side of the variable frequency power supply 8 provides the test transformer 5 with no-load loss and no-load current test power; the transformer circuit 200 can be designed to include a current transformer 3 and a voltage transformer 4, the primary side of the current transformer 3 is connected in series between the outlet side of the variable frequency power supply 8 and the low voltage side of the test transformer 5, and the primary side of the voltage transformer 4 is connected in parallel with the low voltage side of the test transformer 5; the detection circuit 300 can be designed to include a power analyzer 9, which is respectively connected to the secondary side of the current transformer 3 and the secondary side of the voltage transformer 4; wherein, the operating frequency of the variable frequency power supply 8 includes the operating frequency of the test transformer 5, the operating frequency of the current transformer 3 is equal to the operating frequency of the voltage transformer 4 (such as both are 50 Hz), and the operating frequency of the test transformer 5 is less than the operating frequency of the current transformer 3 or the voltage transformer 4 (such as less than 50 Hz).

[0040] For example, when performing the load loss and impedance voltage test of a low-frequency transformer, the low-frequency transformer performance test system can be designed to include a load loss and impedance voltage test subsystem. Figure 4The power supply circuit 100 can be designed to include a variable frequency power supply 8, the outlet side of the variable frequency power supply 8 is connected to the high voltage side of the test transformer 5, and the outlet side of the variable frequency power supply 8 provides the test transformer 5 with a load loss and impedance voltage test power supply; the transformer circuit 200 can be designed to include a current transformer 3 and a voltage transformer 4, the primary side of the current transformer 3 is connected in series between the outlet side of the variable frequency power supply 8 and the high voltage side of the test transformer 5, and the primary side of the voltage transformer 4 is connected in parallel with the high voltage side of the test transformer 5; the detection circuit 300 can be designed to include a power analyzer 9, which is respectively connected to the secondary side of the current transformer 3 and the secondary side of the voltage transformer 4; wherein, the operating frequency of the variable frequency power supply 8 includes the operating frequency of the test transformer 5, the operating frequency of the current transformer 3 is equal to the operating frequency of the voltage transformer 4 (such as both are 50 Hz), and the operating frequency of the test transformer 5 is less than the operating frequency of the current transformer 3 or the voltage transformer 4 (such as less than 50 Hz).

[0041] In addition, the above-mentioned load loss and impedance voltage test subsystem can also be used as a temperature rise test subsystem to perform temperature rise tests on low-frequency transformers.

[0042] For example, when performing a zero-sequence impedance test on a low-frequency transformer, the low-frequency transformer performance test system can be designed to include a zero-sequence impedance test subsystem. Figure 4 The power supply circuit 100 can be designed to include a variable frequency power supply 8, the outlet side of the variable frequency power supply 8 is connected to the low voltage side of the tested transformer 5, and the outlet side of the variable frequency power supply 8 provides a zero-sequence impedance test power supply for the tested transformer 5; the transformer circuit 200 can be designed to include a current transformer 3, the primary side of the current transformer 3 is connected in series between the outlet side of the variable frequency power supply 8 and the low voltage side of the tested transformer 5; the detection circuit 300 can be designed to include a power analyzer 9 and a multimeter 10, the power analyzer 9 is connected to the outlet side of the current transformer 3, and the multimeter 10 is connected to the low voltage side of the tested transformer 5 (such as Figure 4 wherein the operating frequency of the variable frequency power supply 8 includes the operating frequency of the tested transformer 5, and the operating frequency of the tested transformer 5 is less than the operating frequency of the current transformer 3.

[0043] To further ensure the test accuracy of the above-mentioned low-frequency transformer performance test system, the above-mentioned first preset condition may at least include: the rated working magnetic flux of the current transformer ≤ the first preset magnetic flux threshold; the above-mentioned second preset condition may at least include: the rated working magnetic flux of the voltage transformer ≤ the second preset magnetic flux threshold.

[0044] For example, Figures 2 to 4The above-mentioned transformer circuit 200 includes a current transformer 3 and a voltage transformer 4. In order to ensure that the measurement accuracy of the current transformer 3 and the voltage transformer 4 reaches level 0.1, the rated working magnetic flux density of the selected current transformer 3 is ≤0.1T, and the rated working magnetic flux density of the selected voltage transformer 4 is ≤0.9T, and the current transformer 3 and the voltage transformer 4 should meet this condition at any frequency.

[0045] The above-mentioned inductive withstand voltage test subsystem, no-load loss and no-load current test subsystem, load loss and impedance voltage test subsystem, and zero-sequence impedance test subsystem are described below using a specific example.

[0046] See also Figure 2 As shown in FIG, the induction withstand voltage test subsystem mainly includes a voltage regulator 1 with an operating frequency of 50 Hz, an intermediate transformer 2, a current transformer (CT) 3, a voltage transformer (PT) 4, an ammeter 6 and a voltmeter 7, and a test transformer 5 with an operating frequency (i.e., rated frequency) of 50 / n Hz (n≥2); the inlet side of the voltage regulator 1 is connected to the AC power supply ( Figure 2 The output side of the voltage regulator 1 is connected to the low-voltage side of the intermediate transformer 2. The high-voltage side of the intermediate transformer 2 provides the inductive withstand voltage test power supply for the test transformer 5. The high-voltage side of the intermediate transformer 2 is connected to the low-voltage side of the test transformer 5. The primary side of the current transformer 3 is connected in series between the high-voltage side of the intermediate transformer 2 and the low-voltage side of the test transformer 5. The primary side of the voltage transformer 4 is connected in parallel with the low-voltage side of the test transformer 5. An ammeter 6 is connected to the secondary side of the current transformer 3, and a voltmeter 7 is connected to the secondary side of the voltage transformer 4. The test frequency (i.e., the operating frequency of the voltage regulator 1, intermediate transformer 2, current transformer 3, voltage transformer 4, ammeter 6 or voltmeter 7) is 50 Hz, which is n times the operating frequency of the test transformer, 50 / n Hz, meeting the frequency requirement for inductive withstand voltage (i.e., the ratio of the test frequency to the operating frequency of the test transformer, n ≥ 2). Since the induction voltage withstand test subsystem operates at 50 Hz, the measurement accuracy of the current transformer 3 and the voltage transformer 4 will not be affected. The parameters of the equipment in the induction voltage withstand test subsystem are selected by professionals according to the test requirements.

[0047] See also Figure 3As shown, the no-load loss and no-load current test subsystem primarily includes a variable-frequency power supply 8 operating at a frequency of 50 / n Hz (n>1), a power analyzer 9, a current transformer (CT) 3 and a voltage transformer (PT) 4 operating at 50 Hz, and a test transformer 5 operating at a frequency (i.e., rated frequency) of 50 / n Hz (n>1). The output side of the variable-frequency power supply 8 is connected to the low-voltage side of the test transformer 5, providing the test transformer 5 with power for no-load loss and no-load current testing. The primary side of the current transformer 3 is connected in series between the output side of the variable-frequency power supply 8 and the low-voltage side of the test transformer 5, while the primary side of the voltage transformer 4 is connected in parallel with the low-voltage side of the test transformer 5. The power analyzer 9 is connected to the secondary sides of the current transformer 3 and the secondary sides of the voltage transformer 4, respectively. As previously mentioned, the current transformer 3 and the voltage transformer 4 may experience significant measurement deviations at low frequencies. The current transformer and voltage transformer built into the power analyzer 9 also utilize the principle of electromagnetic induction for measurement. Measurement deviations increase at low frequencies, so the measurement accuracy of the power analyzer 9 can be improved by reducing the input current and voltage. Furthermore, the transformation ratio (secondary side) of the current transformer 3 and voltage transformer 4 in this no-load loss and no-load current test subsystem must be coordinated with the current and voltage limits of the power analyzer 9 at low frequencies. The voltage and current limits that can be input to the power analyzer 9, as well as the transformation ratio range of the current transformer 3 and voltage transformer 4, can be calculated based on the operating parameters, no-load loss, and no-load current parameters of the transformer under test 5.

[0048] See also Figure 4 As shown, the load loss and impedance voltage test subsystem mainly includes a variable frequency power supply 8 with an operating frequency of 50 / n Hz (n>1), a power analyzer 9, a current transformer (CT) 3 and a voltage transformer (PT) 4 with an operating frequency of 50 Hz, and a test transformer 5 with an operating frequency (i.e., rated frequency) of 50 / n Hz (n>1); the output side of the variable frequency power supply 8 is connected to the high voltage side of the test transformer 5, and the output side of the variable frequency power supply 8 provides the test transformer 5 with load loss and impedance voltage test power; the primary side of the current transformer 3 is connected in series between the output side of the variable frequency power supply 8 and the high voltage side of the test transformer 5, and the primary side of the voltage transformer 4 is connected in parallel with the high voltage side of the test transformer 5; the power analyzer 9 is connected to the secondary side of the current transformer 3 and the secondary side of the voltage transformer 4, respectively. Since the impact of low frequency on the equipment and instruments in the load loss and impedance voltage test subsystem is similar to the impact of low frequency on the above-mentioned no-load loss and no-load current test subsystem, the voltage and current limits that can be input to the power analyzer 9 and the transformation ratio range of the current transformer 3 and the voltage transformer 4 can be calculated based on the operating parameters, load loss and impedance voltage parameters of the tested transformer 5.

[0049] In addition, the above Figure 4The load loss and impedance voltage test subsystem shown can also be used as a temperature rise test subsystem for performing temperature rise tests on low-frequency transformers; that is, the temperature rise test subsystem can share a set of equipment with the load loss and impedance voltage test subsystem.

[0050] See also Figure 5 As shown, the zero-sequence impedance test subsystem primarily includes a variable-frequency power supply 8 operating at a frequency of 50 / n Hz (n>1), a power analyzer 9, a current transformer (CT) 3 operating at 50 Hz, and a multimeter 10. The output side of the variable-frequency power supply 8 is connected to the low-voltage side of the transformer under test 5, providing zero-sequence impedance test power to the transformer under test 5. The primary side of the current transformer 3 is connected in series between the output side of the variable-frequency power supply 8 and the low-voltage side of the transformer under test 5. The power analyzer 9 is connected to the secondary side of the current transformer 3, and the multimeter 10 is connected to the low-voltage side o and a, b, and c of the transformer under test 5. The impact of low frequency on the zero-sequence impedance test subsystem is similar to that described above. Therefore, the current limit that can be input to the power analyzer 9 and the transformation ratio range of the current transformer 3 can be calculated based on the operating parameters and zero-sequence impedance parameters of the transformer under test 5.

[0051] Since the above-mentioned transformer circuit can include a current transformer and a voltage transformer, it is suitable for conducting induced voltage withstand test, no-load loss and no-load current test, load loss and impedance voltage test, temperature rise test, etc. of the low-frequency transformer. Based on this, for the case where the above-mentioned transformer circuit includes a current transformer and a voltage transformer, the embodiment of the present invention provides a low-frequency transformer performance test method, see Figure 6 As shown, the method may include:

[0052] Step S602: Determine the rated current of the primary side of the current transformer according to the first preset condition and the test current of the transformer under test.

[0053] Step S604: Determine the rated voltage of the primary side of the voltage transformer according to the second preset condition and the test voltage of the tested transformer.

[0054] Step S606: inputting a corresponding current into the primary side of the current transformer according to the determined rated current magnitude, and inputting a corresponding voltage into the primary side of the voltage transformer according to the determined rated voltage magnitude.

[0055] Step S608, obtaining the performance test result of the tested transformer through the detection circuit; wherein the performance test result may include at least one of the following: the induced withstand voltage of the tested transformer, the no-load loss and no-load current of the tested transformer, and the load loss and impedance voltage of the tested transformer.

[0056] The performance test time for the induced withstand voltage of the above-mentioned transformer under test is determined based on the operating frequency of the transformer under test (i.e., rated frequency) and the operating frequency of the current transformer or voltage transformer (i.e., test frequency). For example, performance test time = 120 × rated frequency / test frequency, but shall not be less than 15 seconds.

[0057] Since the above-mentioned mutual inductor circuit may include a current transformer, it is suitable for conducting a zero-sequence impedance test of a low-frequency transformer. Based on this, for the case where the above-mentioned mutual inductor circuit includes a current transformer, the embodiment of the present invention also provides another low-frequency transformer performance test method, see Figure 7 As shown, the method may include:

[0058] Step S702: Determine the rated current of the primary side of the current transformer according to the first preset condition and the test current of the transformer under test.

[0059] Step S704: inputting a corresponding current into the primary side of the current transformer according to the determined rated current.

[0060] Step S706: Acquire the performance test result of the tested transformer through the detection circuit; wherein the performance test result at least includes the zero-sequence impedance of the tested transformer.

[0061] The low-frequency transformer performance testing method provided by the embodiment of the present invention can carry out performance testing tests of low-frequency transformers (such as induced voltage withstand test, no-load loss and no-load current test, load loss and impedance voltage test, zero-sequence impedance test, etc.), which can ensure the accuracy of the low-frequency transformer performance test results while reducing the cost of low-frequency transformer performance testing.

[0062] For ease of description, the low-frequency transformer performance test method provided in an embodiment of the present invention is described as follows, taking the above n as 3 and the operating parameters of the tested transformer including "capacity of 400 kVA, rated voltage ratio of 10 kV / 0.69 kV, operating frequency of 50 / 3 Hz, connection group of Dyn11, high-voltage side rated current of 23.1 A, and low-voltage side rated current of 577.4 A" as an example.

[0063] (1) Selection method of current transformer (CT) and voltage transformer (PT) at low frequency:

[0064] 1. To ensure that the measurement accuracy of CT and PT at 50Hz in the low-frequency transformer performance test system reaches 0.1 level, the rated working magnetic flux density of CT is selected to be ≤0.1T, and the rated working magnetic flux density of PT is selected to be ≤0.9T. The current transformer and voltage transformer should meet this condition at any frequency.

[0065] 2. Calculation of CT's rated working magnetic flux density:

[0066] Load impedance: Where Z f -CT secondary side load impedance, Ω; S N -CT rated capacity, VA; I N -CT secondary side rated current, A;

[0067] Load direct resistance: - Secondary side load power factor, generally 0.8;

[0068] Load reactance:

[0069] Loop impedance: Wherein, the secondary side circuit impedance of Z-CT includes the load impedance and the CT impedance itself, Ω; R L - CT coil DC resistance, Ω; X L -CT reactance value, Ω; other variables have the same meaning as in formula (1);

[0070] The calculation is explained using a CT with a rated capacity of 15VA and a rated current ratio of 300A / 5A. Based on experience, the transformer's own impedance is approximately 0.15-0.25 times the secondary-side load impedance, with 0.2 times being used as an example.

[0071] At 50Hz: loop impedance Load DC resistance R f =0.6×0.8=0.48Ω, load reactance X f50 =0.6×0.6=0.36Ω, loop impedance

[0072] At 50 / 3Hz: loop impedance R f =0.48Ω, and the reactance value is proportional to the frequency, the load reactance Loop impedance

[0073] Among them, Z 50 / 3 / Z 50 =0.6 / 0.72=5 / 6;

[0074] Induced voltage: U = I N ×Z(3), where the secondary induced voltage of U-CT is V;

[0075] Rated working magnetic flux density of CT: Where B N - rated working flux density of CT; f- operating frequency of CT, Hz; S- core cross-sectional area, cm 2;W-number of coil turns;

[0076] The core cross-sectional area S remains unchanged, the number of coil turns W remains unchanged, and if the rated current of the CT secondary side I is required N unchanged, according to formula (4), the rated working magnetic flux density of CT at 50 / 3Hz is Rated working magnetic flux density of CT at 50Hz That is, the rated working magnetic flux density of the CT at 50 / 3Hz is 2.5 times the rated working magnetic flux density of the CT at 50 / 3Hz. The rated working magnetic flux density of the CT at 50 / 3Hz can reach up to 2.5×0.1=0.25T, which will cause the CT measurement accuracy to fail to reach level 0.1, and the accuracy of the measurement data will decrease.

[0077] To ensure the measurement accuracy of CT, it is necessary to ensure that the rated working magnetic flux density of CT at 50 / 3Hz is ≤0.1T. According to formula (4), the rated current of CT at a frequency of 50 / 3Hz is

[0078] I N50 / 3 =I N50 / 2.5, where I N50 / 3 - Rated current of CT at 50 / 3Hz, A; I N50 =I N50 / 2.5-CT rated current at 50Hz, A;

[0079] Therefore, the current needs to be reduced, that is, the rated current of the CT at 50Hz should be selected as 2.5 times the test current of the tested transformer to ensure that the CT meets the accuracy requirements.

[0080] 3. Calculation of PT's rated working magnetic flux density:

[0081] Where B N -Rated working magnetic flux density, T; U N -The rated voltage of the primary side of the PT, V; the meanings of other variables can be found in formula (4).

[0082] The core cross-sectional area S remains unchanged, the number of coil turns W remains unchanged, if U N It remains unchanged. According to formula (6), the rated working magnetic flux of PT at 50 / 3Hz is three times that of PT at 50Hz. The rated working magnetic flux of PT at 50 / 3Hz can reach up to 3×0.9=2.7T (note that the core of voltage transformer will be seriously saturated at this magnetic flux), which will cause the PT measurement accuracy to fail to reach 0.1 level. Not only will the accuracy of measurement data decrease, but the deviation will also be large, resulting in measurement data errors.

[0083] To ensure measurement accuracy, the rated working magnetic flux density of the PT at 50 / 3Hz must be ≤0.9T. According to formula (6), the rated voltage U of the PT at 50 / 3Hz is N50 / 3 =U N50 / 3, where U N50 / 3 - Rated voltage of the primary side of the PT at 50 / 3Hz, V; U N50 - Rated voltage of the primary side of the PT at 50 Hz, V;

[0084] Therefore, the voltage needs to be lowered, that is, the rated voltage of the primary side of the PT at 50Hz should be selected as 3 times the test voltage of the tested transformer to ensure that the PT meets the accuracy requirements.

[0085] (2) Induction withstand voltage test method for low-frequency transformers:

[0086] by Figure 2 For example, the voltage at the input end of the transformer under test (i.e., low-voltage side a, b, c, o) is required to be twice the rated voltage of the low-voltage side of the transformer under test (0.69×2=1.38kV), and the test frequency is also required to be ≥2 times the operating frequency. A 50Hz voltage regulator is used as the test power source, and its frequency is 3 times the operating frequency of the transformer under test (50 / 3Hz). Since the rated output voltage of a general voltage regulator is relatively low (generally 0.8kV), it cannot meet the test voltage required for this test. It can be boosted through a 50Hz intermediate transformer. After boosting, the output voltage of the intermediate transformer should be ≥1.38kV. The test time is 40s. Other procedures are the same as those for a normal induction withstand voltage test. During the test, observe whether the readings on the ammeter and voltmeter meet the requirements.

[0087] (3) Test method for no-load loss and no-load current of low-frequency transformer:

[0088] by Figure 3For example, the high-voltage sides A, B, and C of the transformer under test are open-circuited, and the rated voltage (0.69 kV) of the transformer under test is input to the input terminals (i.e., the low-voltage sides a, b, and c) of the transformer under test. The no-load loss and no-load current of the transformer are measured. A variable-frequency power supply with a frequency conversion range of 50 / 3 Hz is selected, and professional personnel calculate whether parameters such as capacity and voltage meet the test requirements. Current transformers (CTs) and voltage transformers (PTs) are installed in the corresponding positions, and the collected PT secondary voltage and CT secondary current signals are connected to the power analyzer. The rated voltage (0.69 kV) of the low-voltage side of the transformer under test is input to the input terminals (i.e., the low-voltage side) of the transformer under test, and the no-load loss and no-load current are read from the power analyzer. Because CTs and PTs, like transformers, operate based on the principle of electromagnetic induction, low frequencies can cause measurement deviations of CTs and PTs to increase. In addition, power analyzers also use CTs and PTs based on the electromagnetic induction principle, and the measurement deviations of the power analyzer's own CTs and PTs can also increase at low frequencies. To this end, this article proposes:

[0089] (1) Determine the input current limit and input voltage limit of the power analyzer: Assume that the input current limit of the power analyzer at 50 Hz is 75 A, and the input voltage limit of the power analyzer at 50 Hz is 750 V; based on this, the input current limit of the power analyzer at 50 / 3 Hz becomes 75 / 2.5 = 30 A, and the input voltage limit of the power analyzer at 50 / 3 Hz becomes 750 / 3 = 250 V.

[0090] (2) Determine the rated current of the primary side of the current transformer: Assuming that the no-load current of the test transformer with a capacity of 400KVA is 1% of the rated current of the low-voltage side of the test transformer, the no-load current is 577.4x1%=5.77A; based on this, considering the influence of frequency on CT, the rated current of the primary side of CT should be greater than or equal to 5.77×2.5=14.5A to ensure the measurement accuracy of CT; the transformation ratio of CT needs to be calculated according to the range of power analyzer to ensure that the actual output current value of the secondary side of CT is not greater than the input current limit (30A) of the power analyzer at 50 / 3Hz frequency.

[0091] (3) Determine the rated voltage of the primary side of the voltage transformer: The rated voltage of the low-voltage side of the tested transformer is 690V. Considering the influence of frequency on PT, the rated voltage of the primary side of PT should be greater than or equal to 690×3=2070V to ensure the measurement accuracy. The transformation ratio of PT needs to be calculated according to the range of power analyzer to ensure that the actual output voltage value of the secondary side of PT is not greater than the input voltage limit (250V) of the power analyzer at 50 / 3Hz frequency.

[0092] (IV) Test methods for load loss and impedance voltage of low-frequency transformers:

[0093] by Figure 4 For example, the low-voltage sides a, b, and c of the tested transformer are short-circuited, and the rated current (23.1A) of the high-voltage side of the tested transformer is input to the input end of the tested transformer (i.e., the high-voltage side A, B, and C), and the load loss and impedance voltage of the transformer are measured. A variable-frequency power supply with a frequency conversion range including 50 / 3Hz is selected, and professional personnel are required to calculate whether the capacity, voltage and other parameters meet the test requirements. Current transformers (CTs) and voltage transformers (PTs) are installed at the corresponding positions, and the collected PT secondary voltage signals and CT secondary current signals are connected to the power analyzer. The rated current (23.1A) is input to the input end of the tested transformer (i.e., the high-voltage side), and the load loss and impedance voltage in the power analyzer are read. As mentioned above, the measurement accuracy of the power analyzer, CT, and PT are all affected by frequency. To this end, this article proposes:

[0094] (1) Determine the input current limit and input voltage limit of the power analyzer: Same as the no-load loss and no-load current tests, the input current limit of the power analyzer at 50 / 3Hz frequency is 30A, and the input voltage limit of the power analyzer at 50 / 3Hz frequency is 250V.

[0095] (2) Determine the rated current of the primary side of the current transformer: The rated current of the high-voltage side of the test transformer is 23.1A. Considering the effect of frequency on the CT, the rated current of the CT primary side should be greater than or equal to 23.1×2.5=57.8A to ensure measurement accuracy. The CT ratio must be calculated based on the power analyzer range to ensure that the actual output voltage value of the CT secondary side does not exceed the input current limit of the power analyzer at 50 / 3Hz (30A).

[0096] (3) Determine the rated voltage of the primary side of the voltage transformer: The impedance voltage of the test transformer at a capacity of 400kVA is 3.6% to 4.4% of the rated voltage of the high-voltage side of the test transformer. Assuming that the standard value is 4% of the rated voltage of the high-voltage side of the test transformer and the maximum value allowed by the national standard is 4.4% of the rated voltage of the high-voltage side of the test transformer, the maximum input voltage of the high-voltage side of the test transformer is 10000×4.4%=440V. Based on this, considering the effect of frequency on the PT, the rated voltage of the primary side of the PT should be greater than or equal to 440×3=1320V to ensure test accuracy. The PT's transformation ratio needs to be calculated according to the power analyzer range to ensure that the actual output voltage value of the PT's secondary side does not exceed the input voltage limit of the power analyzer at 50 / 3Hz (250V).

[0097] (5) Zero-sequence impedance test method for low-frequency transformer:

[0098] by Figure 5For example, open the high-voltage side A, B, and C of the tested transformer, short-circuit the low-voltage side a, b, and c of the tested transformer, and input current at the short-circuit point and the neutral point o three times the rated current of the low-voltage side of the tested transformer (i.e., 577.4×3=1732.2A). Use a multimeter to measure the voltage U between the short-circuit point a, b, and c and the neutral point o, read the current I of the power analyzer, and calculate the zero-sequence impedance Z=U / I×3. Select a variable-frequency power supply with a frequency conversion range including 50 / 3Hz, and have professionals calculate whether the capacity, voltage and other parameters meet the test requirements. Install a current transformer CT at the corresponding position, and connect the collected CT secondary current signal to the power analyzer. As mentioned above, the measurement accuracy of the power analyzer and CT is affected by the frequency. To this end, this article proposes:

[0099] (1) Determine the input current limit of the power analyzer: Same as the "no-load loss and no-load current" test, the input current limit of the power analyzer at 50 / 3Hz frequency is 30A.

[0100] (2) Determine the rated current of the primary side of the current transformer: Assuming the standard test current of the test transformer is 1732.2A, considering the effect of frequency on the CT, the rated current of the CT primary side should be greater than or equal to 1732.2×2.5=4330.5A to ensure measurement accuracy. However, current transformers with this ratio are too large and not commonly used. Since the connection group is Dyn11, there is a linear relationship between the test current and the test voltage of the test transformer, and the zero-sequence impedance of the test transformer is a fixed value. Therefore, the current input at the short-circuit points a, b, and c of the test transformer and the neutral point o can be 10% of the standard test current (i.e., 173A). The rated current of the CT primary side should be ≥433A. The CT ratio must be calculated based on the power analyzer range to ensure that the actual output current value of the CT secondary side does not exceed the input current limit of the power analyzer at a frequency of 50 / 3Hz (30A).

[0101] By adopting the above operation method, only the original 50Hz equipment and instruments are needed to carry out performance tests of low-frequency transformers below 50Hz (such as induced voltage withstand test, no-load loss and no-load current test, load loss and impedance voltage test, zero-sequence impedance test, etc.), which can ensure the accuracy of the low-frequency transformer performance test results while reducing the cost of low-frequency transformer performance testing.

[0102] The low-frequency transformer performance testing method provided in the embodiment of the present invention has the same implementation principle and technical effects as those of the aforementioned system embodiment. For the sake of brief description, for matters not mentioned in the method embodiment, reference can be made to the corresponding content in the aforementioned system embodiment.

[0103] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A low-frequency transformer performance testing system, characterized in that: The system includes a power supply circuit, a mutual inductor circuit, a detection circuit and a tested transformer; the power supply circuit is connected to the tested transformer; the power supply circuit provides test power for the tested transformer; the mutual inductor circuit is respectively connected to the power supply circuit, the tested transformer and the detection circuit; The transformer circuit includes a current transformer, and the operating frequency of the tested transformer is less than the operating frequency of the current transformer; or the transformer circuit includes a current transformer and a voltage transformer, the operating frequency of the current transformer is equal to the operating frequency of the voltage transformer, and the operating frequency of the tested transformer is less than the operating frequency of the current transformer or the voltage transformer; The rated working magnetic flux density of the current transformer meets the first preset condition; The rated operating magnetic flux density of the voltage transformer meets the second preset condition; The first preset condition includes: the rated working magnetic flux density of the current transformer is less than or equal to a first preset magnetic flux density threshold; The second preset condition includes: the rated operating magnetic flux of the voltage transformer is less than or equal to a second preset magnetic flux threshold.

2. The low-frequency transformer performance testing system according to claim 1, characterized in that: The power supply circuit includes an alternating current power supply, a voltage regulator, and an intermediate transformer; the inlet side of the voltage regulator is connected to the alternating current power supply; the outlet side of the voltage regulator is connected to the low-voltage side of the intermediate transformer; the high-voltage side of the intermediate transformer provides the induction withstand voltage test power supply for the tested transformer; the high-voltage side of the intermediate transformer is connected to the low-voltage side of the tested transformer; The mutual inductor circuit includes a current transformer and a voltage transformer; the primary side of the current transformer is connected in series between the high voltage side of the intermediate transformer and the low voltage side of the tested transformer; the primary side of the voltage transformer is connected in parallel with the low voltage side of the tested transformer; The detection circuit includes an ammeter and a voltmeter; the ammeter is connected to the secondary side of the current transformer; the voltmeter is connected to the secondary side of the voltage transformer.

3. The low-frequency transformer performance testing system according to claim 1, characterized in that: The power supply circuit includes a variable frequency power supply; the outlet side of the variable frequency power supply is connected to the low voltage side of the tested transformer; the outlet side of the variable frequency power supply provides no-load loss and no-load current test power for the tested transformer; The mutual inductor circuit includes a current transformer and a voltage transformer; the primary side of the current transformer is connected in series between the output side of the variable frequency power supply and the low voltage side of the tested transformer; the primary side of the voltage transformer is connected in parallel with the low voltage side of the tested transformer; The detection circuit includes a power analyzer; the power analyzer is connected to the secondary side of the current transformer and the secondary side of the voltage transformer respectively.

4. The low-frequency transformer performance testing system according to claim 1, characterized in that: The power supply circuit includes a variable frequency power supply; the outlet side of the variable frequency power supply is connected to the high voltage side of the tested transformer; the outlet side of the variable frequency power supply provides the tested transformer with a load loss and impedance voltage test power supply; The mutual inductor circuit includes a current transformer and a voltage transformer; the primary side of the current transformer is connected in series between the output side of the variable frequency power supply and the high voltage side of the tested transformer; the primary side of the voltage transformer is connected in parallel with the high voltage side of the tested transformer; The detection circuit includes a power analyzer; the power analyzer is connected to the secondary side of the current transformer and the secondary side of the voltage transformer respectively.

5. The low-frequency transformer performance testing system according to claim 1, characterized in that: The power supply circuit includes a variable frequency power supply; the outlet side of the variable frequency power supply is connected to the low voltage side of the tested transformer; the outlet side of the variable frequency power supply provides a zero-sequence impedance test power supply for the tested transformer; The mutual inductor circuit includes a current transformer; the primary side of the current transformer is connected in series between the output side of the variable frequency power supply and the low voltage side of the tested transformer; The detection circuit includes a power analyzer and a multimeter; the power analyzer is connected to the secondary side of the current transformer; and the multimeter is connected to the low-voltage side of the tested transformer.

6. The low-frequency transformer performance testing system according to claim 2, characterized in that: The operating frequencies of the voltage regulator, the intermediate transformer, the current transformer and the voltage transformer are equal; the operating frequency of the tested transformer is lower than the operating frequency of the voltage regulator, the intermediate transformer, the current transformer or the voltage transformer.

7. The low-frequency transformer performance testing system according to any one of claims 3 to 5, characterized in that: The operating frequency of the variable frequency power supply includes the operating frequency of the tested transformer; the operating frequency of the current transformer is equal to the operating frequency of the voltage transformer; and the operating frequency of the tested transformer is lower than the operating frequency of the current transformer or the voltage transformer.

8. The low-frequency transformer performance testing system according to claim 2, characterized in that: The ratio of the operating frequency of the current transformer to the operating frequency of the tested transformer is n; or, the operating frequency of the current transformer is equal to the operating frequency of the voltage transformer, and the ratio of the operating frequency of the current transformer or the voltage transformer to the operating frequency of the tested transformer is n; wherein n≥2.

9. A method for testing the performance of a low-frequency transformer, characterized in that: The low-frequency transformer performance testing system according to any one of claims 1 to 8 is applied; the method comprising: If the mutual inductor circuit includes the current transformer, determining the rated current of the primary side of the current transformer according to the first preset condition and the test current of the tested transformer; and inputting a corresponding current into the primary side of the current transformer according to the determined rated current; If the transformer circuit includes the current transformer and the voltage transformer, determining the rated current of the primary side of the current transformer according to the first preset condition and the test current of the tested transformer; determining the rated voltage of the primary side of the voltage transformer according to the second preset condition and the test voltage of the tested transformer; inputting a corresponding current into the primary side of the current transformer according to the determined rated current, and inputting a corresponding voltage into the primary side of the voltage transformer according to the determined rated voltage; Obtaining a performance test result of the tested transformer through the detection circuit; wherein the performance test result includes one of the following: the induced withstand voltage of the tested transformer, the no-load loss and no-load current of the tested transformer, the load loss and impedance voltage of the tested transformer, and the zero-sequence impedance of the tested transformer; The performance test time of the induced withstand voltage of the tested transformer is determined according to the operating frequency of the tested transformer and the operating frequency of the current transformer or the voltage transformer.

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