Test device for on-load tapchanger switching tests of power transformers
By introducing an energy storage absorption device into the test device, the instantaneous peak current generated in the power transformer is absorbed, which solves the problem of excessive load peak in the test power supply, reduces the risk of equipment, and improves the safety and reliability of the test device.
Patent Information
- Application Number
- CN202111653231.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-30
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2041-12-30
AI Technical Summary
The existing on-load tap-off switch switching test device used for power transformers has a large instantaneous load peak in the test power supply, resulting in an increase in equipment risk.
A test device is designed, including a test power supply, an intermediate transformer and an energy storage absorption device. The energy storage absorption device absorbs the instantaneous peak current generated in the power transformer through a capacitor module to suppress its impact on the test power supply.
It effectively reduces the peak of instantaneous current in the test power supply, reduces the risk of equipment failure and damage, and improves the safety and reliability of the test device.
Smart Images
Figure CN114563695B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of electric power equipment, and in particular to a test device for a switching test of an on-load tap changer of a power transformer. Background Art
[0002] In order to determine the reliability of power transformers and ensure their safe operation, various tests must be carried out on power transformers before they leave the factory in accordance with national or industry standards to verify whether the performance of the power transformers meets the standards and regulations. For example, existing large-capacity power transformers usually have a voltage regulation function, that is, they can change the transformation ratio of the power transformer under load, so it is necessary to conduct an on-load tap changer switching test to ensure that the power transformer can smoothly switch the tap changer under working conditions.
[0003] The on-load tap changer switching test of a power transformer usually requires that the power transformer to be tested be connected to the circuit of the test device, and that the test power supply be used to simulate the conditions that the power transformer may encounter during normal operation, and that the on-load tap changer be switched 10 times under load (i.e., at rated frequency and close to rated current). For power transformers used for large-capacity three-phase generators, during the switching test, due to the sudden change in impedance of the power transformer and the change in loop parameters, the test capacity under load changes greatly, so the winding may pass a large current and have a high voltage. Accordingly, a large capacity mutation will be caused to the test power supply, causing overvoltage, overcurrent, overheating, etc. to occur in the components of the test power supply, which may cause damage or failure of the test power supply.
[0004] Therefore, it is necessary to improve the existing test device for on-load tap changer switching test of power transformer. Summary of the invention
[0005] In view of this, the present invention proposes a test device for on-load tap changer switching test of power transformer to reduce the short-term load peak generated in the test power supply when the test capacity of the power transformer changes, thereby reducing equipment risks.
[0006] Therefore, according to one aspect of the present invention, there is provided a test device for an on-load tap changer switching test of a power transformer, the power transformer comprising a first primary winding and a first secondary winding, characterized in that the test device comprises: a test power supply, the test power supply having a first output terminal, a second output terminal and a third output terminal, and being configured to output three-phase alternating current through the first output terminal, the second output terminal and the third output terminal; an intermediate transformer, the intermediate transformer comprising a second primary winding and a second secondary winding, the second primary winding being configured to be electrically connected to the test power supply, and the second secondary winding being configured to be electrically connected to the first primary winding of the power transformer; and an energy storage absorption device, the energy storage absorption device being electrically connected to the first output terminal, the second output terminal and the third output terminal, and being configured to absorb the instantaneous peak current generated in the power transformer and coupled to the first output terminal, the second output terminal and the third output terminal via the intermediate transformer during the on-load tap changer switching test, so as to suppress the impact of the instantaneous peak current on the test power supply.
[0007] According to one embodiment of the present invention, the energy storage absorption device includes a first capacitor module, a second capacitor module and a third capacitor module, wherein the first capacitor module is electrically connected to the first output end and the second output end, the second capacitor module is electrically connected to the second output end and the third output end, and the third capacitor module is electrically connected to the first output end and the third output end.
[0008] According to an embodiment of the present invention, each of the first capacitor module, the second capacitor module and the third capacitor module includes a plurality of capacitors connected in series and / or in parallel.
[0009] According to an embodiment of the present invention, each capacitor module includes a first capacitor, a second capacitor, a third capacitor and a fourth capacitor, wherein the first capacitor and the third capacitor are connected in series, the second capacitor and the fourth capacitor are connected in series, and a first component formed by the first capacitor and the third capacitor in series is connected in parallel with a second component formed by the second capacitor and the fourth capacitor in series; wherein each capacitor module also includes a bypass wire corresponding to at least one of the first capacitor, the second capacitor, the third capacitor and the fourth capacitor, so as to bypass the at least one capacitor; wherein a ratio of a minimum value to a maximum value of the capacitance of the first capacitor, the second capacitor, the third capacitor and the fourth capacitor is in the range of 0.1 to 1.
[0010] According to an embodiment of the present invention, each capacitor module further includes a first switch, which is connected in the first component and is configured to electrically disconnect the first component when the first switch is opened, and to connect the first component in parallel with the second component when the first switch is closed.
[0011] According to an embodiment of the present invention, each capacitor module further includes a first bypass wire, a second bypass wire, a second switch and a third switch, wherein the second switch and the third switch are single-pole double-throw switches, a first end of the first bypass wire is electrically connected to the first end of the first capacitor, a second end of the first bypass wire is electrically connected to the first terminal of the second switch, a second terminal of the second switch is electrically connected to the second end of the first capacitor, and a third terminal of the second switch is electrically connected to the first end of the third capacitor, so that when the third terminal of the second switch is connected to the first terminal of the second switch, the first capacitor is bypassed by the first bypass wire, and when the third terminal of the second switch is connected to the second terminal of the second switch, the first capacitor is bypassed by the first bypass wire. When the second terminal of the switch is connected, the second end of the first capacitor and the first end of the third capacitor are electrically short-circuited; the first end of the second bypass wire is electrically connected to the first end of the second capacitor, the second end of the second bypass wire is electrically connected to the first terminal of the third switch, the second terminal of the third switch is electrically connected to the second end of the second capacitor, and the third terminal of the third switch is electrically connected to the first end of the fourth capacitor, so that when the third terminal of the third switch is connected to the first terminal of the third switch, the second capacitor is bypassed by the second bypass wire, and when the third terminal of the third switch is connected to the second terminal of the third switch, the second end of the second capacitor and the first end of the fourth capacitor are electrically short-circuited.
[0012] According to an embodiment of the present invention, the test device further comprises a power analyzer, and the power analyzer is configured to measure the load power of the power transformer through at least one voltage transformer and at least one current transformer.
[0013] According to an embodiment of the present invention, the at least one voltage transformer and the at least one current transformer are configured to be respectively coupled to a line electrically connecting the second secondary winding and the first primary winding.
[0014] It can be seen from the above scheme that since the test device of the present invention is connected with an energy storage absorption device between the output ends of the test power supply, when the circuit changes suddenly during the on-load tap changer switching test, the instantaneous peak current coupled to the output end of the test power supply due to the change of the test capacity can be absorbed, so that it can be released into the circuit in a more gentle manner, thereby reducing the instantaneous current generated in the test power supply and reducing the risk of the equipment. In addition, the energy storage absorption device used in the test device of the present invention can be composed of capacitors with different parameters connected in series and / or in parallel, and the configuration mode can be flexibly selected according to the different capacities of the test product. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the above and other features and advantages of the present invention will be more apparent to those skilled in the art. In the accompanying drawings:
[0016] Figure 1 A schematic block diagram of a test device for an on-load tap changer switching test of a power transformer according to an embodiment of the present invention;
[0017] Figure 2 for Figure 1 A schematic circuit diagram of the energy storage absorption device shown in ;
[0018] Figure 3 for Figure 2 A schematic circuit diagram of an exemplary capacitor module of an energy storage absorption device is shown in FIG.
[0019] The reference numerals are as follows:
[0020] 10 Test power supply 20 Intermediate transformer 30 Power transformer
[0021] 40 power analyzer 50 energy storage absorption device 101 first output terminal
[0022] 102 second output terminal 103 third output terminal 201 first input terminal
[0023] 202 second input terminal 203 third input terminal 21 second primary winding
[0024] 22 Second secondary winding 31 First primary winding 32 First secondary winding
[0025] 2u, 2v, 2w The first end of the second primary winding 1u, 1v, 1w The first end of the second secondary winding A, B, C The first end of the first primary winding
[0026] a, b, c The first end of the secondary winding CT Voltage transformer PT Current transformer
[0027] C1 First capacitor module C2 Second capacitor module C3 Third capacitor module
[0028] C11 First capacitor C12 Second capacitor C13 Third capacitor
[0029] C14 Fourth capacitor K1 First switch K2 Second switch
[0030] K3 Third switch L1 First bypass conductor L2 Second bypass conductor DETAILED DESCRIPTION
[0031] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail by the following embodiments. It should be understood by those skilled in the art that these exemplary embodiments do not mean any limitation to the present invention. In addition, the features in the embodiments of the present invention can be combined with each other without conflict. In different drawings, the same or similar parts are represented by the same reference numerals, and other parts are omitted for the sake of brevity, but this does not mean that the test device for the on-load tap changer switching test of the power transformer of the present invention cannot include other parts. It should be understood that the size, proportional relationship and number of parts in the drawings are not intended to limit the present invention.
[0032] The terms "first", "second", etc. are used herein to describe various components, but these components are not limited by these terms. These terms are only used to distinguish one component from other components. Therefore, the first component mentioned below can be the second component in the technical solution of the present invention.
[0033] Reference below Figure 1 A test device for an on-load tap changer switching test of a power transformer according to an embodiment of the present invention is described. Figure 1 Not only the test device of the present invention is shown, but also the power transformer 30, such as Figure 1 The power transformer 30 is, for example, a large-capacity power transformer for a three-phase AC generator, and includes a first primary winding 31 and a first secondary winding 32. According to an embodiment of the present invention, a test device for an on-load tap changer switching test of a power transformer includes a test power source 10, an intermediate transformer 20 (such as Figure 1 ) and an energy storage absorption device 50 (as shown in the middle dashed box in Figure 1). The test power supply 10 has a first output terminal 101, a second output terminal 102 and a third output terminal 103, and is configured to output three-phase AC power through the first output terminal 101, the second output terminal 102 and the third output terminal 103. The intermediate transformer 20 includes a second primary winding 21 and a second secondary winding 22, wherein the second primary winding 21 is configured to be electrically connected to the test power supply 10, and the second secondary winding 22 is configured to be electrically connected to the first primary winding 31 of the power transformer 30. The energy storage absorption device 50 is electrically connected to the first output terminal 101, the second output terminal 102 and the third output terminal 103, and is configured to absorb the instantaneous peak current generated in the power transformer 30 and coupled to the first output terminal 101, the second output terminal 102 and the third output terminal 103 through the intermediate transformer 20 during the on-load tap changer switching test, so as to suppress the impact of the instantaneous peak current on the test power supply 10. For example, in the load state, due to the switching test of the on-load tap changer, the impedance of the power transformer 30 will change sharply, and an instantaneous peak current may be generated in the test circuit, and its instantaneous peak value may reach tens of thousands of amperes. The instantaneous peak current is coupled to the first output terminal 101, the second output terminal 102 and the third output terminal 103 of the test power supply 10 through the intermediate transformer 20. If there is no energy storage absorption device 50, the instantaneous peak current will be coupled to the test power supply 10, causing the protection device of the test power supply 10 to trip and interrupt the test, or causing the test power supply 10 to be damaged.
[0034] Since an energy storage absorption device is provided between the output ends of the test power supply in the test device of the present invention, the energy storage absorption device can absorb the drastic change of the test capacity in the test circuit, reduce the instantaneous peak current caused by the change of the test capacity, make it become a relatively gentle energy and release it into the test circuit, thereby reducing the instantaneous current generated in the test power supply, avoiding the problems of overvoltage, overcurrent, overheating and the like in the test power supply during the on-load tap changer switching test, and reducing the risk of equipment.
[0035] refer to Figure 2 , which shows the schematic structure and electrical connection of the energy storage absorption device 50 according to an embodiment of the present invention, wherein the energy storage absorption device 50 preferably includes a first capacitor module C1, a second capacitor module C2 and a third capacitor module C3. However, the energy storage absorption device 50 of the present invention is not limited to the capacitor module, and can also adopt an inductor module, a diode module, a MOSFET module, etc. The following only takes the capacitor module as an example to describe the energy storage absorption device of the present invention. Figure 2As shown, the first capacitor module C1 is electrically connected to the first output terminal 101 and the second output terminal 102, the second capacitor module C2 is electrically connected to the second output terminal 102 and the third output terminal 103, and the third capacitor module C3 is electrically connected to the first output terminal 101 and the third output terminal 103. It should be noted that since the intermediate transformer 20 includes a first input terminal 201, a second input terminal 202 and a third input terminal 203, and the first input terminal 201 is electrically connected to the first output terminal 101, the second input terminal 202 is electrically connected to the second output terminal 102, and the third input terminal 203 is electrically connected to the third output terminal 103, the first capacitor module C1, the second capacitor module C2 and the third capacitor module C3 can also be considered to be electrically connected between the first input terminal 201 and the second input terminal 202, between the second input terminal 202 and the third input terminal 203, and between the first input terminal 201 and the third input terminal 203, respectively. In this way, a capacitor module is connected between every two output terminals of the test power supply 10 , so as to provide protection for each phase of the test power supply 10 .
[0036] According to one embodiment of the present invention, the capacitance of the first capacitor module C1, the second capacitor module C2 and the third capacitor module C3 may be the same to maintain the balance between the three phases of the test power supply 10, and each may include one or more capacitors. Preferably, each of the first capacitor module C1, the second capacitor module C2 and the third capacitor module C3 includes a plurality of capacitors connected in series and / or in parallel. Therefore, when conducting the test, each capacitor module can select different configuration modes according to the capacity of the pressure test product, and flexibly adjust the capacity of the capacitor module. Accordingly, the interval of the tapping gear of the on-load tap changer can be shortened to provide more precise adjustment.
[0037] According to one embodiment of the present invention, Figure 3 As shown, the specific structure of an exemplary capacitor module in the energy storage absorption device is provided. For example, the exemplary structure of the first capacitor module C1 connected between the first output terminal 101 and the second output terminal 102 of the test power supply 10 is shown. However, the second capacitor module C2 and the third capacitor module C3 can also adopt the same structure. Therefore, the structure of the capacitor module described below can be used for any of the above-mentioned capacitor modules. Figure 3 , the capacitor module may include a first capacitor C11, a second capacitor C12, a third capacitor C13 and a fourth capacitor C14, wherein the first capacitor C11 and the third capacitor C13 are connected in series, the second capacitor C12 and the fourth capacitor C14 are connected in series, and the first component formed by the first capacitor C11 and the third capacitor C13 in series is connected in parallel with the second component formed by the second capacitor C12 and the fourth capacitor C14 in series. Figure 3It is shown that in an exemplary capacitor module, each capacitor module also includes a bypass wire corresponding to at least one of the first capacitor C11, the second capacitor C12, the third capacitor C13 and the fourth capacitor C14, so as to bypass the at least one capacitor. Through series, parallel and bypass wires, the flexibility of the capacitor module configuration can be more fully utilized, so that more different test capacities can be adapted. In order to facilitate effective capacity adjustment, the ratio of the minimum and maximum values in the capacitance of the first capacitor C11, the second capacitor C12, the third capacitor C13 and the fourth capacitor C14 can be in the range of 0.1 to 1. For example, the capacity of the first capacitor C11 and the second capacitor C12 can be the same, and is 2μF, while the capacity of the third capacitor C13 and the fourth capacitor C14 can be the same, and is 17.25μF. It should be noted that the present invention is not limited to the above-mentioned capacitor capacity, and the capacity of the first capacitor C11, the second capacitor C12, the third capacitor C13 and the fourth capacitor C14 as described above can be adjusted according to the parameters of the power transformer under test.
[0038] In addition, according to one embodiment of the present invention, Figure 3 The switch included in the exemplary capacitor module for implementing various configurations is also shown. For example, the capacitor module includes a first switch K1, wherein the first switch K1 is connected in the first component and is configured to electrically disconnect the first component when the first switch K1 is disconnected, and to connect the first component to the second component in parallel when the first switch K1 is closed. Therefore, the first switch K1 can realize the selection between the combined capacitance of the first component and the second component when they are connected in parallel and the individual capacitance of the second component.
[0039] According to one embodiment of the present invention, Figure 3As shown, the capacitor module may further include a first bypass wire L1, a second bypass wire L2, a second switch K2 and a third switch K3, wherein the second switch K2 and the third switch K3 are shown as single-pole double-throw switches. The first end of the first bypass wire L1 is electrically connected to the first end of the first capacitor C11, the second end of the first bypass wire L1 is electrically connected to the first terminal of the second switch K2, the second terminal of the second switch K2 is electrically connected to the second end of the first capacitor C11, and the third terminal of the second switch K2 is electrically connected to the first end of the third capacitor C13, so that when the third terminal of the second switch K2 is connected to the first terminal of the second switch K2, the first capacitor C11 is bypassed by the first bypass wire L1, and when the third terminal of the second switch K2 is connected to the second terminal of the second switch K2, the second end of the first capacitor C11 and the first end of the third capacitor C13 are electrically short-circuited. The first end of the second bypass wire L2 is electrically connected to the first end of the second capacitor C12, the second end of the second bypass wire L2 is electrically connected to the first terminal of the third switch K3, the second terminal of the third switch K3 is electrically connected to the second end of the second capacitor C12, and the third terminal of the third switch K3 is electrically connected to the first end of the fourth capacitor C14, so that when the third terminal of the third switch K3 is connected to the first terminal of the third switch K3, the second capacitor C12 is bypassed by the second bypass wire L2, and when the third terminal of the third switch K3 is connected to the second terminal of the third switch K3, the second end of the second capacitor C12 is electrically short-circuited with the first end of the fourth capacitor C14. In this way, by selectively connecting the second switch K2 and the third switch K3 between the first capacitor C11 and the first bypass wire L1 and the second capacitor C12 and the second bypass wire L2, more capacitor capacity combinations can be provided to meet different test capacities.
[0040] It should be noted that the capacitor module may also have more or less than 4 capacitors, more or less than 3 switches. In addition, each assembly may include more than 2 capacitors in series, and more than 2 assemblies may be connected in parallel. Therefore, the present invention is not limited to the quantity of the capacitor modules and capacitors listed above. In addition, at least one of a resistor, an inductor, a diode (not shown) etc. may also be connected in the capacitor module to further improve the absorption effect of the instantaneous peak current.
[0041] exist Figure 1In the test apparatus shown, the three-phase windings of each of the second primary winding 21 and the second secondary winding 22 of the intermediate transformer 20 are electrically connected in a star connection, for example, the second primary winding head ends 2u, 2v and 2w of the second primary winding 21 (three-phase winding) are externally connected, and the ends of the three-phase windings (not marked) are grounded, while the second secondary winding head ends 1u, 1v and 1w of the second secondary winding 22 (three-phase winding) are externally connected, and the ends of the three-phase windings (not marked) are grounded. The three-phase windings of the first primary winding 31 of the power transformer 30 are electrically connected in a star connection, and the three-phase windings of the first secondary winding 32 of the power transformer 30 are electrically connected in a delta connection. For example, the first primary winding head ends A, B and C of the first primary winding 31 (three-phase winding) are externally connected, and the ends (not marked) of the three-phase windings are grounded, and the first secondary winding head ends a, b and c of the first secondary winding 32 (three-phase winding) are respectively connected to the ends of the adjacent windings. However, the present invention is not limited to this. According to different test requirements, the windings of the intermediate transformer 20 and the power transformer 30 can also have other connections. For example, the second primary winding and the second secondary winding of the intermediate transformer 20 are both connected in a delta connection, the first primary winding 31 of the power transformer 30 is connected in a delta connection, and the first secondary winding 32 is connected in a star connection.
[0042] It should be understood that the power transformer 30 further includes an on-load tap changer (not shown), which can adjust the voltage of the power transformer when the voltage fluctuates, thereby changing the transformation ratio of the power transformer 30 .
[0043] Since the variable frequency power supply can output a voltage waveform with stable frequency, stable voltage and close to zero internal resistance, and has the advantages of simple installation, convenient operation, easy maintenance and high precision, the test power supply 10 is preferably a variable frequency power supply, which is configured to convert the industrial frequency alternating current through AC→DC→AC to output power with adjustable voltage and frequency.
[0044] According to an embodiment of the present invention, the test device further comprises a power analyzer 40, which is configured to detect the power of a power transformer PT (such as Figure 1 3 as shown) and at least one current transformer CT (as shown Figure 1 3) to measure the load power of the power transformer 30. For example, a power analyzer of model TMS580 provided by Hafele Company of Switzerland can be used. To obtain test data, at least one voltage transformer PT and at least one current transformer CT are configured to be coupled with the line electrically connecting the second secondary winding 22 and the first primary winding 31, respectively. However, the present invention is not limited thereto, and other measuring instruments or sensors can also be used for testing.
[0045] Combined with Figures 1 to 3With reference to the structure of the test device shown in FIG, the working process of the exemplary test device of the present invention is described below.
[0046] In the on-load tap changer switching test of the power transformer, the test power supply 10 provides the intermediate transformer 20 with a voltage corresponding to the test capacity of the power transformer 30, and then performs a cyclic switching operation (for example, 10 times) on the on-load tap changer of the power transformer 30. Since the capacity of the power transformer is relatively large, during the on-load tap changer switching process, the impedance of the power transformer 30 changes suddenly, resulting in an instantaneous peak current in the test circuit, which will be coupled to the output end of the test power supply 10 through the intermediate transformer 20. However, since the test device of the present invention includes an energy storage absorption device located between the output ends of the test power supply 10, it can absorb this instantaneous peak current, thereby reducing the instantaneous current generated in the test power supply and reducing the risk of the equipment.
[0047] It should be understood that when the energy storage absorption device of the present invention is configured to include other modules different from the capacitor module described above, for example, an inductor module, a diode module, etc., the principle of the present invention is also applicable, and therefore, it is not repeated herein.
[0048] In summary, the present invention provides a test device for an on-load tap changer switching test of a power transformer 30, comprising: a test power supply 10, which has a first output terminal 101, a second output terminal 102 and a third output terminal 103, and is configured to output three-phase alternating current through the first output terminal 101, the second output terminal 102 and the third output terminal 103; an intermediate transformer 20, which includes a second primary winding 21 and a second secondary winding 22, and the second primary winding 21 is configured to be electrically connected to the test power supply 10. The second secondary winding 22 is configured to be electrically connected to the first primary winding 31 of the power transformer 30; and an energy storage absorption device 50 is electrically connected to the first output terminal 101, the second output terminal 102 and the third output terminal 103, and is configured to absorb the instantaneous peak current generated in the power transformer 30 and coupled to the first output terminal 101, the second output terminal 102 and the third output terminal 103 through the intermediate transformer 20 during the on-load tap changer switching test, so as to suppress the impact of the instantaneous peak current on the test power supply 10. The test device of the present invention can reduce the instantaneous current in the test power supply and reduce the risk of equipment.
[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A test device for an on-load tap changer switching test of a power transformer (30), wherein the power transformer (30) comprises a first primary winding (31) and a first secondary winding (32), characterized in that: The test device comprises: A test power supply (10), the test power supply having a first output terminal (101), a second output terminal (102) and a third output terminal (103), and configured to output three-phase alternating current through the first output terminal (101), the second output terminal (102) and the third output terminal (103); an intermediate transformer (20), the intermediate transformer comprising a second primary winding (21) and a second secondary winding (22), the second primary winding (21) being configured to be electrically connected to the test power supply (10), the second secondary winding (22) being configured to be electrically connected to the first primary winding (31) of the power transformer (30); and an energy storage absorption device (50), the energy storage absorption device being electrically connected to the first output terminal (101), the second output terminal (102) and the third output terminal (103), and being configured to absorb, during the on-load tap changer switching test, an instantaneous peak current generated in the power transformer (30) and coupled to the first output terminal (101), the second output terminal (102) and the third output terminal (103) via the intermediate transformer (20), so as to suppress the impact of the instantaneous peak current on the test power supply (10), The energy storage absorption device (50) comprises a first capacitor module (C1), a second capacitor module (C2) and a third capacitor module (C3), wherein the first capacitor module (C1) is electrically connected to the first output end (101) and the second output end (102), the second capacitor module (C2) is electrically connected to the second output end (102) and the third output end (103), and the third capacitor module (C3) is electrically connected to the first output end (101) and the third output end (103). Each of the first capacitor module (C1), the second capacitor module (C2) and the third capacitor module (C3) comprises a plurality of capacitors connected in series and / or in parallel. Each of the capacitor modules comprises a first capacitor (C11), a second capacitor (C12), a third capacitor (C13) and a fourth capacitor (C14), wherein the first capacitor (C11) and the third capacitor (C13) are connected in series, the second capacitor (C12) and the fourth capacitor (C14) are connected in series, and a first component formed by the first capacitor (C11) and the third capacitor (C13) connected in series is connected in parallel with a second component formed by the second capacitor (C12) and the fourth capacitor (C14) connected in series; Each of the capacitor modules further comprises a bypass wire corresponding to at least one of the first capacitor (C11), the second capacitor (C12), the third capacitor (C13) and the fourth capacitor (C14), so as to bypass the at least one capacitor; The ratio of the minimum value to the maximum value of the capacitance of the first capacitor (C11), the second capacitor (C12), the third capacitor (C13) and the fourth capacitor (C14) is in the range of 0.1 to 1.
2. The test device according to claim 1, characterized in that: Each capacitor module further includes a first switch (K1), which is connected in the first component and configured to electrically disconnect the first component when the first switch (K1) is opened, and to connect the first component in parallel with the second component when the first switch (K1) is closed.
3. The test device according to claim 2, characterized in that: Each capacitor module further comprises a first bypass wire (L1), a second bypass wire (L2), a second switch (K2) and a third switch (K3), wherein the second switch (K2) and the third switch (K3) are single-pole double-throw switches, a first end of the first bypass wire (L1) is electrically connected to a first end of the first capacitor (C11), a second end of the first bypass wire (L1) is electrically connected to a first terminal of the second switch (K2), a second terminal of the second switch (K2) is electrically connected to a second end of the first capacitor (C11), and a third terminal of the second switch (K2) is electrically connected to a first end of the third capacitor (C13), so that when the third terminal of the second switch (K2) is connected to the first terminal of the second switch (K2), the first capacitor (C11) is bypassed by the first bypass wire (L1), and when the third terminal of the second switch (K2) is connected to the first terminal of the second switch (K2), the first capacitor (C11) is bypassed by the first bypass wire (L1), and when the third terminal of the second switch (K2) is connected to the first terminal of the second switch (K2), the first capacitor (C11) is bypassed by the first bypass wire (L1). When the two terminals are connected, the second end of the first capacitor (C11) and the first end of the third capacitor (C13) are electrically short-circuited; the first end of the second bypass wire (L2) is electrically connected to the first end of the second capacitor (C12), the second end of the second bypass wire (L2) is electrically connected to the first terminal of the third switch (K3), the second terminal of the third switch (K3) is electrically connected to the second end of the second capacitor (C12), and the third terminal of the third switch (K3) is electrically connected to the first end of the fourth capacitor (C14), so that when the third terminal of the third switch (K3) is connected to the first terminal of the third switch (K3), the second capacitor (C12) is bypassed by the second bypass wire (L2), and when the third terminal of the third switch (K3) is connected to the second terminal of the third switch (K3), the second end of the second capacitor (C12) and the first end of the fourth capacitor (C14) are electrically short-circuited.
4. The test device according to any one of claims 1 to 3, characterized in that The test device also includes a power analyzer (40) configured to measure the load power of the power transformer (30) through at least one voltage transformer (PT) and at least one current transformer (CT).
5. The test device according to claim 4, characterized in that: The at least one voltage transformer (PT) and the at least one current transformer (CT) are configured to be coupled to lines electrically connecting the second secondary winding (22) and the first primary winding (31), respectively.