Neutral point resonance elimination resistor short circuit circuit, handcart type voltage transformer and method

Abstract

The invention belongs to the field of transformer substations, and discloses a neutral point resonance elimination resistor short-circuit circuit, a handcart type voltage transformer and a method, and the circuit achieves the quick switching of a resonance elimination resistor between a short-circuit state and a normal operation state through the introduction of a switching module. According to the invention, the tedious step of completing the short circuit of the resonance elimination resistor by manually pulling out and pushing in the PT handcart in the process of completing the system ground capacitance current test through the bus PT opening triangular side is solved, the measurement efficiency is greatly improved, and the risk in the operation process is also significantly reduced; the arrangement of the switching module enables the handcart type voltage transformer to be easily switched between a test state and an operation state, and extra physical operation does not need to be carried out on equipment. Therefore, not only is the operation process simplified, but also equipment loss possibly caused by frequent operation is reduced, so that the service life of equipment is prolonged; the circuit can improve the test efficiency, reduce the potential safety hazard and prolong the service life of equipment, and has good popularization and application values.

Description

Technical Field

[0001] The invention belongs to the technical field of substations, and specifically relates to the field of ground capacitance current testing of substation systems, and in particular to a neutral point detuning resistance short-circuiting circuit, a trolley-type voltage transformer and a method. Background Art

[0002] At present, a large number of electromagnetic voltage transformers (PT, Phase Voltage Transformer) are running in the 10kV system. When the system has single-phase direct grounding, single-phase arc grounding, and sudden closing of the busbar when no-load, it is easy to resonate due to the nonlinearity of the voltage transformer core inductance. When the PT primary inductance and the system ground capacitance meet the resonance condition, very high overvoltage and overcurrent will be generated, causing the PT primary fuse to burn out or even explode, seriously threatening the safe operation of the power grid.

[0003] Domestic and foreign scholars have proposed a variety of suppression methods for the ferromagnetic resonance overvoltage caused by electromagnetic PTs: First, connect a nonlinear resistor (detuning resistor) at the neutral point of the primary winding, which is currently a more commonly used method with less economic cost. Second, connect a resistor in parallel at the open triangle. Third, select an electromagnetic PT with good excitation inductance. Fourth, change the resonance parameters to detuning. Fifth, install an arc suppression coil. At present, in the 10kV line of the substation, the above method 1 is often used to suppress ferromagnetic resonance, that is, to connect a nonlinear resistor at the neutral point of the PT primary winding, that is, to use a trolley-type PT with a detuning resistor. However, when this neutral point is connected in series with a detuning resistor, when the system-to-ground capacitance current is tested on the open triangle side of the PT, the accuracy of the test will be affected. Therefore, it is necessary to short-circuit the detuning resistor before conducting the capacitance current test; at this time, this process will lead to the disadvantages of cumbersome operation steps, low efficiency, great safety hazards and shortened equipment life in the measurement.

[0004] It can be seen from this that in the capacitance current measurement measures when the neutral point of the trolley-type voltage transformer is connected in series with a detuning resistor, it is necessary to pull out and push in the PT trolley to complete the short-circuit of the detuning resistor before measuring, which leads to low efficiency and great safety hazards. Summary of the invention

[0005] The present invention provides a neutral point harmonic elimination resistor short-circuiting circuit, a trolley-type voltage transformer and a method, so as to solve the technical problem that in the capacitance current measurement measure when the neutral point of the trolley-type voltage transformer is connected in series with the harmonic elimination resistor, it is necessary to pull out and push in the PT trolley to complete the short-circuiting of the harmonic elimination resistor before measuring, resulting in low efficiency and great safety hazards.

[0006] In order to achieve the above object, the present invention adopts the following technical contents: A neutral point detuning resistor short-circuit circuit is used in the test and operation of a handcart-type voltage transformer, and includes a switching module; The switching module is arranged between the detuning resistor and the primary winding of the voltage transformer; The switching module is used to switch the detuning resistor between the short-circuited state and the normal operating state, so as to correspondingly switch the trolley-type voltage transformer between the test state and the operating state.

[0007] Furthermore, the switching module includes a conversion switch; the conversion switch can short-circuit the detuning resistor when it is converted to a first position, and can connect the detuning resistor in series with the primary winding of the voltage transformer for normal operation when it is converted to a second position.

[0008] Further, the transfer switch includes a common terminal, a test terminal and an operation terminal; The common terminal is connected to the primary winding of the voltage transformer; The test terminal is connected to one end of the detuning resistor; The operating terminal is connected to the other end of the detuning resistor; The common terminal can be selectively connected to the test terminal or the operation terminal.

[0009] Furthermore, one end of the detuning resistor is also connected to the ground.

[0010] Furthermore, one end of the primary winding of the voltage transformer is connected to the switching module; and the other end is connected to the electrical triangle structure of the substation system.

[0011] A working method of a neutral point harmonic elimination resistor short-circuit circuit, based on the above neutral point harmonic elimination resistor short-circuit circuit, comprising: The switching module is used to switch the detuning resistor from the normal operating state to the short-circuited state; the trolley-type voltage transformer is switched to the test state to measure the system-to-ground capacitance current; After the measurement is completed, the switching module is used to restore the detuning resistor from the short-circuited state to the normal operating state, so that the trolley-type voltage transformer is restored to the operating state for normal operation.

[0012] Furthermore, before the test, the conversion switch is switched to the first position so that the detuning resistor is short-circuited to enter the test state; after the test, the conversion switch is switched to the second position so that the detuning resistor is connected in series with the primary winding of the voltage transformer to restore to a normal operating state.

[0013] Further, the transfer switch includes a common terminal, a test terminal and an operation terminal; Before testing, connect the common terminal to the test terminal and disconnect it from the running terminal, so that the detuning resistor is short-circuited to enter the test state; After the test is completed, the common terminal is connected to the operating terminal and disconnected from the test terminal, so that the detuning resistor is connected in series with the primary winding of the voltage transformer and returns to a normal operating state.

[0014] Furthermore, one end of the detuning resistor is also connected to the ground.

[0015] A trolley-type voltage transformer comprises the above-mentioned neutral point detuning resistance short-circuiting circuit.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention provides a neutral point harmonic elimination resistor short-circuiting circuit. The circuit realizes the rapid switching of the harmonic elimination resistor between the short-circuiting state and the normal operating state by introducing a switching module. This function directly solves the cumbersome steps of manually pulling out and pushing in a PT trolley to complete the short-circuiting of the harmonic elimination resistor in the traditional method, which not only greatly improves the measurement efficiency, but also significantly reduces the safety risks in the operation process; the setting of the switching module enables the trolley-type voltage transformer to be easily switched between the test state and the operating state without performing additional physical operations on the equipment; this not only simplifies the operation process, but also reduces the equipment loss that may be caused by frequent operations, thereby extending the service life of the equipment; the use of the circuit can improve the test efficiency, reduce safety hazards and extend the life of the equipment, and has good promotion and application value.

[0017] In addition, this circuit has high flexibility and adaptability; the design of the switching module can be flexibly adjusted according to actual test requirements to ensure that accurate and reliable measurement results can be obtained in different test scenarios; at the same time, it is also suitable for various types and specifications of trolley-type voltage transformers.

[0018] Preferably, in the present invention, a conversion switch is introduced in the switching module, and the conversion switch can be switched between two positions to respectively realize the short-circuit and normal operation states of the detuning resistor; this design not only improves the accuracy and reliability of the switching, but also facilitates the use of the operator; at the same time, the introduction of the conversion switch also makes the circuit structure more compact, reducing the floor space and cost.

[0019] Further preferably, in the present invention, the specific structure of the transfer switch includes a common terminal, a test terminal and an operation terminal; this design makes the function of the transfer switch clearer and easier to operate; at the same time, the common terminal can be selectively connected to the test terminal or the operation terminal, so that the detuning resistor can be quickly switched between the short-circuited state and the normal operating state. In addition, this structure also improves the reliability and safety of the circuit and ensures the stable operation of the power system.

[0020] Preferably, in the present invention, by connecting one end of the detuning resistor to the ground, the technical solution provides additional safety protection; this design not only helps to eliminate possible harmonic currents, but also improves the anti-interference ability and stability of the circuit; at the same time, the grounding design also complies with electrical safety regulations, ensuring the safety of operators.

[0021] The present invention also provides a working method of a neutral point harmonic elimination resistor short-circuit circuit. Based on the above neutral point harmonic elimination resistor short-circuit circuit, the method can easily switch the harmonic elimination resistor from a normal operating state to a short-circuit state by using a switching module, so that the harmonic elimination resistor can be short-circuited without pulling out or pushing in a PT trolley, so that the trolley-type voltage transformer can be smoothly switched to a test state for measurement; this improvement not only simplifies the operation process and improves the measurement efficiency, but also significantly reduces the safety hazards and equipment losses caused by frequent operation of the PT trolley; at the same time, after the measurement is completed, the switching module can also quickly restore the harmonic elimination resistor from a short-circuit state to a normal operating state, ensuring that the trolley-type voltage transformer can quickly resume normal operation. The use of this method has shown significant beneficial effects in improving measurement efficiency, ensuring operational safety, and extending equipment life.

[0022] Preferably, in the present invention, by clarifying the position of the conversion switch before the test (the first position), the short-circuiting of the detuning resistor is achieved, which provides the necessary conditions for the test state of the trolley-type voltage transformer; this step ensures the accuracy of the system ground capacitance current test and avoids the measurement error caused by the detuning resistor not being correctly short-circuited. At the same time, this step also simplifies the preparation work before the test and improves the test efficiency.

[0023] Further preferably, in the present invention, the common terminal of the conversion switch can accurately control the state of the detuning resistor by selectively connecting or disconnecting the test terminal and the operating terminal, thereby ensuring the accurate switching of the trolley-type voltage transformer between the test and operating states; in addition, this structural design also improves the flexibility and scalability of the circuit, facilitating subsequent maintenance and upgrades.

[0024] The present invention also provides a trolley-type voltage transformer, comprising the above-mentioned neutral point harmonic elimination resistor short-circuiting circuit; the trolley-type voltage transformer utilizes the switching module in the short-circuiting circuit to realize the rapid switching of the harmonic elimination resistor between the test state and the operation state, and there is no need to manually pull out and push in the PT trolley, thereby greatly improving the measurement efficiency, reducing the operation risk, and effectively extending the service life of the equipment; this innovative design not only optimizes the system ground capacitance current measurement process, but also significantly improves the safety and reliability of the trolley-type voltage transformer, providing a strong guarantee for the stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of an existing trolley-type voltage transformer provided by the present invention; Figure 2 A schematic diagram of the principle of the existing PT capacitance current test with detuning resistor provided by the present invention; Figure 3 A schematic diagram of the principle of the existing short-circuited detuning resistor provided by the present invention; Figure 4 A schematic diagram of a neutral point harmonic elimination resistor short-circuit circuit provided by an embodiment of the present invention; Figure 5 A schematic diagram of the wiring principle of a trolley-type voltage transformer provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0030] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] As mentioned in the background technology, domestic and foreign scholars have proposed a variety of suppression methods for the ferromagnetic resonance overvoltage caused by electromagnetic PT: First, connect a nonlinear resistor (detuning resistor) at the neutral point of the primary winding, which is currently a more commonly used method with less economic cost. Second, connect a resistor in parallel at the open triangle. Third, select an electromagnetic PT with good excitation inductance. Fourth, change the resonance parameters to detuning. Fifth, install an arc suppression coil. At present, in the 10kV line of the substation, the above method 1 is mostly used to suppress ferromagnetic resonance, that is, to connect a nonlinear resistor at the neutral point of the PT primary winding, that is, to use a trolley-type PT with a detuning resistor. However, this method will affect the test of the capacitor current, so it is necessary to short-circuit the detuning resistor before carrying out the capacitor current test; at this time, this process will lead to the disadvantages of cumbersome operating steps, low efficiency, great safety hazards and affecting the life of the equipment in the measurement.

[0034] In this embodiment, Figure 1 As shown, the voltage transformers used in 10kV systems are mostly center-mounted trolley-type PT cabinets.

[0035] For the system with ungrounded neutral point, PT with detuning resistor is needed to suppress electromagnetic resonance. Some old stations use arc suppression coil to ground the neutral point, but when the capacity of arc suppression coil is not enough, it is also necessary to increase the detuning resistor to compensate. For the line with detuning resistor at the primary neutral point of PT, when measuring the capacitance current, it is necessary to pull out and push in the PT trolley to complete the short circuit of the detuning resistor before measuring, which leads to the above-mentioned disadvantages. The specific test process is as follows: The 10kV system capacitance current test method is mainly completed by a capacitance current tester. Connect the test line to the open triangle side of the PT, inject the measurement current signal from the PT open triangle, obtain the system voltage feedback, and complete the measurement of the system capacitance current through the corresponding calculation formula. However, as described in the above actual working conditions, in order to suppress the PT resonance, a trolley PT with a detuning resistor at the neutral point is usually selected in the actual circuit. Figure 2 As shown. It can be seen that this method of eliminating the harmonic resistance will greatly affect the accuracy of the capacitance current test. Therefore, in the actual test process, it is necessary to short-circuit before measuring. Figure 3 shown.

[0036] Therefore, in actual work, the operator needs to manually pull out the PT trolley, complete the short-circuit operation and push the trolley in before performing the measurement operation.

[0037] In this wiring method, the following steps are required to carry out the capacitance current test: 1) Pull out the PT trolley, and the maintenance personnel use alligator clips to short-circuit the two ends of the detuning resistor; 2) Push the PT trolley forward and conduct capacitance and current test; 3) After the test is completed, the PT trolley is pulled out again and the maintenance personnel remove the short-circuit wire; 4) After removing the short-circuit wire, push the PT trolley in again to restore the initial operating state.

[0038] 5) Complete the test.

[0039] The test method is to obtain the capacitance current of the system through a capacitance current tester on the open triangle side of the PT. During the test, the PT trolley needs to be pulled out and pushed in twice, and the detuning resistor used to suppress resonance at the neutral point of the PT needs to be short-circuited and restored to complete the measurement.

[0040] Therefore, during the current testing process, the operation and maintenance personnel are required to pull out and push in the PT trolley twice, and the maintenance personnel are required to manually complete the short-circuit and recovery operations twice; this has the disadvantages of too much manual operation, low operating efficiency, and high hidden dangers.

[0041] In order to solve the above problems, this embodiment provides a neutral point detuning resistor short-circuiting circuit. This circuit is an improved design proposed based on the problems existing in the detuning resistor short-circuiting process during capacitor current testing, and is used to achieve the goals of improving efficiency and ensuring safety.

[0042] like Figure 4 As shown, this embodiment provides a neutral point detuning resistor short-circuiting circuit, which is applied to the test and operation process of a trolley-type voltage transformer, and includes a switching module; the switching module is arranged between the detuning resistor and the primary winding of the voltage transformer; the switching module is used to realize the switching of the detuning resistor between the short-circuited state and the normal operating state, so as to correspondingly realize the switching of the trolley-type voltage transformer between the test state and the operating state.

[0043] In this embodiment, the switching module includes a conversion switch; the conversion switch can short-circuit the detuning resistor when it is converted to a first position, and can connect the detuning resistor in series with the primary winding of the voltage transformer for normal operation when it is converted to a second position.

[0044] In this embodiment, the conversion switch includes a common terminal, a test terminal and an operating terminal; the common terminal is connected to the primary winding of the voltage transformer; the test terminal is connected to one end of the detuning resistor; the operating terminal is connected to the other end of the detuning resistor; the common terminal can be selectively connected to the test terminal or the operating terminal.

[0045] In this embodiment, one end of the detuning resistor is also connected to the ground; and one end of the neutral point loop of the primary winding of the voltage transformer is connected to the switching module; and the other end is connected to the electrical triangle structure of the substation system.

[0046] This embodiment also provides a working method of a neutral point harmonic elimination resistor short-circuit circuit, including: The switching module is used to switch the detuning resistor from the normal operating state to the short-circuited state; the trolley-type voltage transformer is switched to the test state to measure the system-to-ground capacitance current through the PT open triangle; After the measurement is completed, the switching module is used to restore the detuning resistor from the short-circuited state to the normal operating state, so that the trolley-type voltage transformer is restored to the operating state for normal operation.

[0047] In this embodiment, before the test, the conversion switch is switched to the first position so that the detuning resistor is short-circuited to enter the test state; after the test, the conversion switch is switched to the second position so that the detuning resistor is connected in series with the primary winding of the voltage transformer to restore to the normal operating state.

[0048] In this embodiment, the transfer switch includes a common terminal, a test terminal and an operation terminal; Before testing, connect the common terminal to the test terminal and disconnect it from the running terminal, so that the detuning resistor is short-circuited to enter the test state; After the test is completed, the common terminal is connected to the operating terminal and disconnected from the test terminal, so that the detuning resistor is connected in series with the primary winding of the voltage transformer and returns to a normal operating state.

[0049] In the working method of the neutral point harmonic elimination resistor short-circuit circuit provided in this embodiment, one end of the harmonic elimination resistor is also connected to the ground.

[0050] In order to further explain the neutral point harmonic elimination resistor short-circuit circuit provided in this embodiment, further description is given below in conjunction with the accompanying drawings: The design principle is as follows: In view of the drawbacks of the above-mentioned short-circuiting detuning resistor process, an improvement idea is proposed. Is it possible to add a switching circuit to the original circuit of the PT trolley equipped with the detuning resistor, and the circuit can realize the short-circuiting of the detuning resistor through the conversion switch. After the test is completed, the circuit can also be restored to the normal operating state through the conversion switch. Based on this idea, the present invention designs a line conversion circuit with two states of operation and test. By adding a double-position switch, the short-circuiting process of the PT neutral point detuning resistor can be realized, and the specific implementation method is as follows: like Figure 4 As shown, here the existing PT trolley is taken as the main improvement object, a breakpoint is added to the upper end of the series detuning resistor, at which a common end and a running end are led out respectively, and a test end is led out below the detuning resistor, and these three ends are respectively connected to the three contacts of the conversion switch, and the conversion switch is set at the PT trolley panel for easy operation. It includes a two-position conversion switch and related wires, which are divided into a measuring position and an operating position. The line conversion can be completed by simple operation, which is simple and easy to operate.

[0051] This embodiment also provides a method for testing a neutral point harmonic elimination resistor short circuit, which is as follows: The test process of the system ground capacitance current is as follows: 1) Switch the switch SA (Switch Auxiliary) to the measurement position and conduct the capacitance current test; 2) Switch the transfer switch SA to the operating position to restore normal operation; 3) Complete the test.

[0052] It can be seen that the circuit improved by the present circuit and method is as follows: Figure 5 As shown, Figure 5This is the wiring schematic diagram of a trolley-type voltage transformer. This trolley-type voltage transformer has a conversion switch. When testing the capacitive current, there is no need to pull out and push in the PT trolley. The conversion between the operating state and the test state can be achieved through the conversion switch. It can be seen that by adopting the improved principle wiring, the process steps of measuring the capacitive current are simplified by half, reducing the manual operation process and the pulling out and pushing in of the equipment, improving work efficiency, reducing equipment loss, and reducing operational risks, with significant improvement effects.

[0053] The present embodiment also provides a trolley-type voltage transformer, including the above-mentioned neutral point detuning resistor short-circuiting circuit; the trolley-type voltage transformer utilizes the switching module in the short-circuiting circuit to realize the rapid switching of the detuning resistor between the test state and the operation state, and there is no need to manually pull out and push in the PT trolley, thereby greatly improving the measurement efficiency, reducing the operation risk, and effectively extending the service life of the equipment; this innovative design not only optimizes the measurement process, but also significantly improves the safety and reliability of the trolley-type voltage transformer, providing a strong guarantee for the stable operation of the power system.

[0054] In summary, the present invention provides a neutral point harmonic elimination resistor short-circuit circuit, a trolley-type voltage transformer and a method, which have the following advantages over existing measurement measures: Before the neutral point harmonic elimination resistor short-circuiting circuit designed by the present invention is applied, the PT trolley needs to be pulled out and pushed in twice in the process of testing the capacitor current to short-circuit and restore the neutral point harmonic elimination resistor that affects the measurement accuracy. This process has the disadvantages of many manual operations, low operating efficiency, and high risk hazards. In view of the above shortcomings, the present invention provides a neutral point harmonic elimination resistor short-circuiting circuit. The circuit can realize the switching of two working states only through a simple conversion switch, which has the advantages of improving work efficiency, reducing equipment loss and reducing operational hazards. The circuit can be used to conveniently, quickly, safely and reliably complete the short-circuiting of the series harmonic elimination resistor, and the operation steps are reduced by 50%, which can significantly improve the work efficiency and quality, and has high practical value.

[0055] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention.

Claims

1. A neutral point harmonic elimination resistor short circuit, characterized in that: Applied to the testing and operation of trolley-type voltage transformers, including switching modules; The switching module is arranged between the detuning resistor and the primary winding of the voltage transformer; The switching module is used to switch the detuning resistor between the short-circuited state and the normal operating state, so as to correspondingly switch the trolley-type voltage transformer between the test state and the operating state.

2. The neutral point harmonic elimination resistor short circuit according to claim 1, characterized in that: The switching module includes a conversion switch; the conversion switch can short-circuit the detuning resistor when it is converted to a first position, and can connect the detuning resistor in series with the primary winding of the voltage transformer for normal operation when it is converted to a second position.

3. The neutral point harmonic elimination resistor short circuit according to claim 2, characterized in that: The transfer switch comprises a common terminal, a test terminal and an operation terminal; The common terminal is connected to the primary winding of the voltage transformer; The test terminal is connected to one end of the detuning resistor; The operating terminal is connected to the other end of the detuning resistor; The common terminal can be selectively connected to the test terminal or the operation terminal.

4. The neutral point harmonic elimination resistor short circuit according to claim 3, characterized in that: One end of the detuning resistor is also connected to the ground.

5. The neutral point harmonic elimination resistor short circuit according to claim 1, characterized in that: One end of the primary winding of the voltage transformer is connected to the switching module; the other end is connected to the electrical triangle structure of the substation system.

6. A method for operating a neutral point harmonic elimination resistor short circuit, characterized in that: The neutral point harmonic elimination resistor short-circuit circuit according to any one of claims 1 to 5 is characterized by comprising: The switching module is used to switch the detuning resistor from the normal operating state to the short-circuited state; the trolley-type voltage transformer is switched to the test state to measure the system-to-ground capacitance current; After the measurement is completed, the switching module is used to restore the detuning resistor from the short-circuited state to the normal operating state, so that the trolley-type voltage transformer is restored to the operating state for normal operation.

7. The working method of the neutral point harmonic elimination resistance short circuit according to claim 6, characterized in that: Before testing, the conversion switch is switched to the first position so that the detuning resistor is short-circuited to enter the testing state; After the test is completed, the switch is switched to the second position so that the detuning resistor is connected in series with the primary winding of the voltage transformer and returns to a normal operating state.

8. The working method of the neutral point harmonic elimination resistance short circuit according to claim 7, characterized in that: The transfer switch includes a common terminal, a test terminal and a run terminal; Before testing, connect the common terminal to the test terminal and disconnect it from the running terminal, so that the detuning resistor is short-circuited to enter the test state; After the test is completed, the common terminal is connected to the operating terminal and disconnected from the test terminal, so that the detuning resistor is connected in series with the primary winding of the voltage transformer and returns to a normal operating state.

9. The working method of the neutral point harmonic elimination resistance short circuit according to claim 8, characterized in that: One end of the detuning resistor is also connected to the ground.

10. A trolley type voltage transformer, characterized in that: It includes the neutral point harmonic elimination resistance short-circuit circuit as described in any one of claims 1 to 5.

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