Back-to-back capacitor bank on-off and on-off test circuit and test method thereof

Abstract

The invention belongs to the technical field of on-off tests, and particularly relates to a back-to-back capacitor bank on-off and on-off test circuit and method, and the circuit comprises a DC charging unit, an inrush current on-off unit, and a capacitive current on-off unit. Wherein the direct current charging unit is connected with the switching inrush current unit through a charging isolation switch QS, a test object TO is arranged in the switching inrush current unit, the capacitive current on-off unit comprises a sphere gap GP, a second inductor Ls, a second resistor Rs, a voltage source Ur and a second capacitor Cs which are connected in series, and bypass switches BP are arranged at the two ends of the sphere gap GP in parallel. The closing and opening of the test object TO can be remotely controlled. On the premise of meeting the inrush current parameter requirement, the test efficiency can be improved, and the test reliability can be enhanced.

Description

Technical Field

[0001] This invention belongs to the field of closing and opening test technology, specifically relating to a closing and opening test circuit and test method for a back-to-back capacitor bank. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Capacitive current switching tests are crucial for high-voltage circuit breakers, as switching capacitive loads is a fundamental task of high-voltage circuit breakers. While capacitive currents are typically small, switching such currents carries the risk of severe breakdown, potentially leading to overvoltages that endanger power grid safety or high-frequency transient voltages that affect power quality in the network. Traditional test circuits generally include an impulse generator set (or network power supply), protective switches, phase-selective closing switches, operating switches, short-circuit transformers, loop inductive reactance, and loop capacitive reactance to verify and assess the various switching and closing performance characteristics of the circuit breaker.

[0004] In the closing and breaking test circuit, capacitive current can be obtained by configuring the capacitor on the load side of the test object. Simultaneously, a certain number of capacitor banks can be configured on the power supply side of the test object to meet the requirements for the peak value and frequency of the closing inrush current. Therefore, capacitor banks on both the power supply and load sides of the test object are generally arranged in the closing and breaking test circuit for convenient wiring. However, in practical applications, due to the inherent inductive reactance of the power supply side capacitor bank circuit, the inrush current frequency during the actual test is lower than expected. While reducing the number of capacitors can meet the frequency requirement, it will not achieve the peak inrush current, thus failing to meet the requirements for the closing inrush current parameters. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a back-to-back capacitor bank closing and opening test circuit and its test method, which improves test efficiency and enhances test reliability while meeting inrush current parameter requirements.

[0006] According to some embodiments, the first aspect of the present invention provides a back-to-back capacitor bank closing and opening test circuit, employing the following technical solution: A back-to-back capacitor bank closing and opening test circuit includes a DC charging unit, a closing inrush current unit, and a capacitive current breaking unit. The DC charging unit is connected to the closing inrush current unit via a charging isolation switch QS. The closing inrush current unit contains a test sample TO. The capacitive current breaking unit includes a ball gap GP and a second inductor L connected in series. s Second resistor R s Voltage source U r Second capacitor C sA bypass switch BP is connected in parallel at both ends of the ball gap GP; the closing and opening of the test sample TO can be remotely controlled.

[0007] As a further technical limitation, the charging isolation switch QS and the first capacitor C in the inrush current closing unit are... h Parallel connection.

[0008] As a further technical limitation, it is located away from the voltage source U. r The second capacitor C s A second voltage divider FRC2 is provided on one side, and a third photoelectric sensor is also provided on the second voltage divider FRC2.

[0009] Furthermore, the back-to-back capacitor bank closing and opening test circuit also includes a data acquisition recorder, and the third photoelectric sensor is connected to the data acquisition recorder via an optical fiber; the data acquisition recorder is also connected to a second photoelectric sensor and a first photoelectric sensor via an optical fiber.

[0010] Furthermore, the second photoelectric sensor is connected to the Rog coil between the sample TO and the second capacitor Cs.

[0011] Furthermore, the first photoelectric sensor is connected to the first voltage divider FRC1, which is positioned between the first push-button switch AB1 and the sample TO in the inrush current closing unit. The inrush current closing unit also includes a first capacitor C. h First inductor L h and the first resistor R h The first capacitor C h The first inductor L h The first resistor R h The first push-button switch AB1, the test sample TO, and the Rog coil Rog are connected in sequence to form a circuit.

[0012] As a further technical limitation, the DC charging unit adopts a voltage doubler rectifier, which establishes a communication connection with the data acquisition and recorder through a voltage regulation control cabinet and a first host computer.

[0013] As a further technical limitation, a back-to-back capacitor bank closing and opening test circuit also includes a second host computer, a timing controller, and a secondary control system for remotely controlling the auxiliary switch and the test sample TO.

[0014] According to some embodiments, the second aspect of the present invention provides a test method for a back-to-back capacitor bank closing and opening test circuit, which adopts a back-to-back capacitor bank closing and opening test circuit provided by the first aspect, and employs the following technical solution: A test method for a back-to-back capacitor bank closing and opening test circuit includes: When the charging isolation switch QS is closed, the first capacitor C... h Charge until the first capacitor C h When the voltage across the terminals is the test sample TO closing voltage, disconnect the charging isolation switch QS and remotely control the test sample TO to close, thus completing the closing inrush current test; During the closing process of the test sample TO, when the distance between the moving and stationary contacts is less than the pre-breakdown distance of the moving and stationary contacts, the moving and stationary contacts of the test sample TO will undergo pre-breakdown, the ball gap GP will be triggered to connect, and the bypass switch BP will close. Complete the closing and opening tests of the back-to-back capacitor bank. The capacitive current breaking unit provides the steady-state current before the test sample is broken and the recovery voltage after the break.

[0015] As a further technical limitation, the expected voltage and expected current are collected before the test, the closing and opening times of the test sample TO are set in the secondary control system, a communication connection is established between the second host computer and the timing controller, and the closing and opening of the auxiliary switch are remotely controlled by the timing controller through the power amplification module.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The inrush current unit in this invention uses an LC oscillation circuit to achieve the inrush current frequency (4250Hz and above) and peak inrush current (20kA and above). Adjustments are made according to changes in the rated voltage of the test sample, i.e., by changing the charging voltage of the capacitor. This makes the test circuit easier to operate and more flexible. Combining the oscillation circuit and the power supply circuit allows for both closing and opening tests in a single test, resulting in higher efficiency and a closer approximation of actual operating conditions. It is not limited by the capacity of the network power supply or impulse generator, and within the allowable charging voltage range of the oscillation circuit, it enhances the laboratory's testing capabilities, greatly improving the practicality of this invention. It can reliably and stably ensure that the closing voltage meets standard requirements. Attached Figure Description

[0017] The accompanying drawings, which form part of this embodiment, are used to provide a further understanding of this embodiment. The illustrative embodiments and their descriptions are used to explain this embodiment and do not constitute an improper limitation of this embodiment.

[0018] Figure 1 This is a schematic diagram of the topology of the back-to-back capacitor bank closing and opening test circuit in Embodiment 1 of the present invention. Figure 2 The first capacitor C in Embodiment 1 of the present invention h A schematic diagram of the curves relating the voltage across the two ends to the distance between the moving and stationary contacts of the test sample TO; Figure 3This is a schematic diagram of the closing and opening current curves in Embodiment 1 of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0023] In this invention, terms such as "fixed connection," "connected," and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0024] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0025] Example 1 Embodiment 1 of the present invention introduces a test circuit for the closing and opening of a back-to-back capacitor bank.

[0026] like Figure 1 The circuit shown is a test circuit for closing and opening a back-to-back capacitor bank, including a DC charging unit, a closing inrush current unit, a capacitive current breaking unit, a first host computer, a voltage regulating control cabinet, a second host computer, a timing controller, a secondary control system, and a data acquisition and recording instrument.

[0027] In this embodiment, the DC charging unit uses a voltage doubler rectifier to convert 380V AC power into DC power. The voltage doubler rectifier establishes a communication connection with the data acquisition and recorder through the control cabinet and the first host computer. The DC charging unit also includes a charging isolation switch QS set at both ends of the voltage doubler rectifier. The charging isolation switch QS is connected to close the inrush current unit.

[0028] In this embodiment, the inrush current closing unit includes a first capacitor C connected in series. h First inductor L h First resistor R h The first push-button switch AB1, the test sample TO, and the Rogowski coil Rog, the charging isolation switch QS, and the first capacitor C h The circuit is connected in parallel. The first voltage divider FRC1 is located between the first push-button switch AB1 and the test sample TO. The first voltage divider FRC1 is equipped with a first photoelectric sensor. The opening and closing of the test sample TO can be remotely controlled. The Rog coil Rog is equipped with a second photoelectric sensor.

[0029] It should be noted that the distance from the first resistor R h The first push-button switch AB1 side, the Rog coil Rog side away from the test sample TO side, and the first resistor R side away from the test sample TO side. h The first capacitor C on the side h One side is connected to a capacitive current interruption unit.

[0030] In this embodiment, the capacitive current interruption unit includes a second push-button switch AB2, a ball gap GP, and a second inductor L connected in series. s Second resistor R s Voltage source U r Second capacitor C s A bypass switch BP is connected in parallel across the two ends of the ball gap GP; it is located away from the voltage source U. r The second capacitor C on the side s A second voltage divider FRC2 is installed on one side, and a third photoelectric sensor is also installed on the second voltage divider FRC2.

[0031] It should be noted that the first, second, and third photoelectric sensors are all connected to the data acquisition and recorder via optical fibers; the first, second, and third photoelectric sensors all use photoelectric conversion modules, that is, they collect the low voltage of the voltage divider or the small current of the Rogowski coil, and at the same time convert the collected signals into optical signals and transmit them to the transient data acquisition and recorder.

[0032] First capacitor C h The main capacitor's function is to store energy, charge it to its initial voltage U0 using a DC charging device, and simultaneously connect it to the first inductor L. hA resonant circuit is formed to generate the required inrush frequency and peak closing inrush current; the first resistor R h The inherent resistance of the circuit; the second inductance L s Second resistor R s These are a current-limiting reactor and a resistor limiting the DC component, respectively, serving as the power supply side impedance; in this embodiment, the impedance of the power supply circuit should not be so low that its short-circuit current exceeds the rated short-circuit breaking current of the circuit breaker; C s For the load-side capacitor bank, and L s and R s Together they serve as impedance to calculate the required capacitive current; Rog is a Rogowski coil used to measure the current flowing through the test specimen; FRC1 and FRC2 are the first and second voltage dividers, respectively, measuring the test voltage when closed and the recovery voltage after opening; the measured current and voltage are waveforms that must be presented in the type test report as specified by the standard.

[0033] It should be noted that the second host computer is connected to the timing controller and, in conjunction with the secondary control system, enables remote control of the first push-button switch AB1, the second push-button switch AB2, the test sample TO, and the bypass switch BP.

[0034] In this embodiment, closing the charging isolation switch QS and the first push-button switch AB1 activates the first capacitor C. h Charge until the first capacitor C h Voltage U across the terminals o When the test specimen TO is closed at the specified voltage, the charging isolating switch QS is disconnected, and the test specimen TO is remotely controlled to close, completing the inrush current test. During the closing process of the test specimen TO, when the distance between the moving and stationary contacts is less than the pre-breakdown distance of the moving and stationary contacts, the moving and stationary contacts of the test specimen TO will undergo pre-breakdown. The second push-button switch AB2 is closed, the ball gap GP is triggered to conduct, and the bypass switch BP is closed to prevent the ball gap GP from being burned for a long time and affecting its lifespan. After the short-circuit interruption lasts for a certain period of time, the test specimen TO is controlled to open, completing the capacitive current interruption test and providing short-circuit current and recovery voltage for the capacitive current interruption unit.

[0035] like Figure 2 As shown, U0 is the first capacitor C h The voltage across the two ends, Tr is the stroke curve. When the sensor (i.e., the sliding rheostat) is fixed on the moving contact of the test sample, the voltage variable of the sensor can be transformed into the distance stroke variable between the moving and stationary contacts of the test sample. Among them, Tr0 is the distance between the moving and stationary contacts of the test sample, and Tr1 is the pre-breakdown distance of the moving and stationary contacts under the action of voltage U0. The measurement of the pre-breakdown distance Tr1 can be achieved through the expected wave test.

[0036] The closing and breaking tests must meet the following conditions: 1) The expected peak closing inflow is equal to or greater than the rated value; 2) The inrush frequency of the test was 4250 Hz; 3) The expected damping coefficient for closing inrush current should not be less than 0.75 for circuit breakers of 72.5kV and below, and not less than 0.85 for circuit breakers above 72.5kV. 4) The closing phase angle should be within ±25° of the peak value of the applied voltage.

[0037] The working principle of the test circuit will be explained in detail below: Let the attenuation coefficient for Damped oscillation angular frequency for ;but According to standard conditions, the initial voltage of the capacitor is known. ;in, The capacitive voltage coefficient, The rated voltage of the test sample TO; the peak value of the inrush current, i.e., the first maximum value. ; Indicates the damping coefficient; f Indicate frequency; determine parameter R h C h L h Solving for the current The maximum value corresponds to the time. .

[0038] It should be noted that before the test sample TO is closed, the initial voltage U0 of the capacitor is always applied across the test sample TO. Theoretically, this value is not less than the peak voltage of the AC power supply. This also illustrates the advantage of the present invention, because the capacitor voltage is a constant DC voltage. Regardless of when the test sample TO is closed, the voltage at the closing moment is always U0. Under AC power conditions, the closing moment is not necessarily at the voltage peak (the maximum value of the sine wave). This demonstrates the reliability and stability of the test circuit in this embodiment.

[0039] Specifically, Simplifying, we obtain the extreme point conditions: The general solution at the maximum point is: ,in, Let the oscillation angular frequency be fixed. ,because and ,Right now ;Depend on and , can be obtained ; and because ,Right now ; and because Therefore Therefore, the first maximum value of the closing current (i.e., the peak value of the closing inrush current) and the second maximum value are respectively at k =0 and k =1 is obtained, that is (1) (2); Depend on , k Given 0, 1, 2, 3, ..., we can obtain: (3); (4); (5); (6); (7); (8); Based on formulas (1) and (2), we can obtain: (9); From formulas (3), (4), and (5), we can obtain:

[0040] The attenuation coefficient is thus obtained, i.e. (10); Using formulas (1), (4), (6), and (10), we can obtain (11); From formulas (7), (8), (10), and (11), we obtain ,Right now (12); Then obtain ,Right now (13); Therefore, from formulas (8), (10), and (12), we get ,Right now (14); Then obtain R h and C h .

[0041] Calculate the charging voltage for the inrush current when the back-to-back capacitor bank is closed, provided that the closing and opening test conditions are met. ; Calculate R h and Ch Based on theoretical calculations, input reactance and capacitance; based on Figure 1 The experimental schematic diagram shown is connected to the actual test circuit of the sample. The resulting closing and opening currents are as follows: Figure 3 As shown; input the required charging voltage into the first host computer. When the charging isolating switch QS is closed, the DC charging device automatically charges; after charging is completed, the charging isolating switch QS automatically opens, and the host computer timing system controls the test sample to close, thus completing one inrush current test.

[0042] This embodiment significantly improves the laboratory's testing capabilities and effectively solves the problem that the closing inrush current parameters of traditional test methods cannot meet the standards; it is not affected by the discreteness of the test sample's TO closing time and can reliably and stably close at the voltage peak.

[0043] Example 2 Embodiment 2 of the present invention introduces a test method for a back-to-back capacitor bank closing and opening test circuit, which adopts a back-to-back capacitor bank closing and opening test circuit introduced in Embodiment 1.

[0044] A test method for a back-to-back capacitor bank closing and opening test circuit includes: Close the charging disconnect switch QS to charge the first capacitor Ch until the voltage across the first capacitor Ch is equal to the closing voltage of the test sample TO. Then, open the charging disconnect switch QS and remotely control the test sample TO to close, thus completing the closing inrush current test. During the closing process of the test sample TO, when the distance between the moving and stationary contacts is less than the pre-breakdown distance of the moving and stationary contacts, the moving and stationary contacts of the test sample TO will undergo pre-breakdown, the ball gap GP will be triggered to connect, and the bypass switch BP will close. Complete the closing and opening tests of the back-to-back capacitor bank. The capacitive current breaking unit provides the steady-state current before the test sample is broken and the recovery voltage after the break.

[0045] As one or more implementation methods, the expected voltage and expected current are collected before the test, the closing and opening times of the test sample TO are set in the secondary control system, a communication connection is established between the second host computer and the timing controller, and the closing and opening of the auxiliary switch are remotely controlled by the timing controller through the power amplification module.

[0046] The detailed steps are the same as the working principle of the back-to-back capacitor bank closing and opening test circuit provided in Example 1, and will not be repeated here.

[0047] The above description is merely a preferred embodiment of this practice and is not intended to limit the scope of this practice. Various modifications and variations can be made to this practice by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this practice should be included within the protection scope of this practice.

Claims

1. A back-to-back capacitor bank closing and opening test circuit, characterized in that, It includes a DC charging unit, a closing inrush current unit, and a capacitive current interruption unit; wherein, the DC charging unit is connected to the closing inrush current unit via a charging isolation switch QS, the closing inrush current unit contains a test sample TO, and the capacitive current interruption unit includes a ball gap GP and a second inductor L connected in series. s Second resistor R s Voltage source U r Second capacitor C s A bypass switch BP is connected in parallel at both ends of the ball gap GP; the closing and opening of the test sample TO can be remotely controlled.

2. The back-to-back capacitor bank closing and opening test circuit as described in claim 1, characterized in that, The charging isolation switch QS and the first capacitor C in the inrush current closing unit h Parallel connection.

3. The back-to-back capacitor bank closing and opening test circuit as described in claim 1, characterized in that, Keep away from voltage source U r The second capacitor C s A second voltage divider FRC2 is provided on one side, and a third photoelectric sensor is also provided on the second voltage divider FRC2.

4. The back-to-back capacitor bank closing and opening test circuit as described in claim 3, characterized in that, It also includes a data acquisition recorder, and the third photoelectric sensor is connected to the data acquisition recorder via an optical fiber; the data acquisition recorder is also connected to a second photoelectric sensor and a first photoelectric sensor via an optical fiber.

5. The back-to-back capacitor bank closing and opening test circuit as described in claim 4, characterized in that, The second photoelectric sensor is connected between the sample TO and the second capacitor C. s On the Rogau coil between them.

6. The back-to-back capacitor bank closing and opening test circuit as described in claim 5, characterized in that, The first photoelectric sensor is connected to the first voltage divider FRC1, which is located between the first push-button switch AB1 and the sample TO in the inrush current closing unit. The inrush current closing unit also includes a first capacitor C. h First inductor L h and the first resistor R h The first capacitor C h The first inductor L h The first resistor R h The first button switch AB1, the test sample TO, and the Rog coil Rog are connected in sequence to form a circuit.

7. The back-to-back capacitor bank closing and opening test circuit as described in claim 1, characterized in that, The DC charging unit adopts a voltage doubler rectifier, which establishes a communication connection with the data acquisition and recorder through a voltage regulation control cabinet and a first host computer.

8. The back-to-back capacitor bank closing and opening test circuit as described in claim 1, characterized in that, It also includes a second host computer, a timing controller, and a secondary control system for remotely controlling auxiliary switches and test samples (TO).

9. A test method for a back-to-back capacitor bank closing and opening test circuit, comprising the back-to-back capacitor bank closing and opening test circuit as described in any one of claims 1-8, characterized in that, include: When the charging isolation switch QS is closed, the first capacitor C... h Charge until the first capacitor C h When the voltage across the terminals is the test sample TO closing voltage, disconnect the charging isolation switch QS and remotely control the test sample TO to close, thus completing the closing inrush current test; During the closing process of the test sample TO, when the distance between the moving and stationary contacts is less than the pre-breakdown distance of the moving and stationary contacts, the moving and stationary contacts of the test sample TO will undergo pre-breakdown, the ball gap GP will be triggered to connect, and the bypass switch BP will close. Complete the closing and opening tests of the back-to-back capacitor bank. The capacitive current breaking unit provides the steady-state current before the test sample is broken and the recovery voltage after the break.

10. The test method for the closing and opening test circuit of a back-to-back capacitor bank as described in claim 9, characterized in that, Before the test, the expected voltage and current are collected. The closing and opening times of the test sample TO are set in the secondary control system. A communication connection is established between the second host computer and the timing controller. The timing controller remotely controls the closing and opening of the auxiliary switch through the power amplification module.

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