Partial discharge measuring device

Abstract

The utility model discloses a partial discharge measuring device, comprising a high voltage source; a coupling capacitor; a detection resistor; the detection circuit comprises a plurality of detection branches which are connected in parallel, each detection branch comprises a detection capacitor and a switching tube, and the detection capacitor is connected with a switching path of the switching tube in series; the capacitance values of a plurality of detection capacitors of the detection circuit are different; the detection branch is connected in parallel with the detection resistor; the first input end of the amplifier circuit is connected with one end of the detection resistor, and the second input end is connected with the other end of the detection resistor; the first input end of the comparator is connected with the output end of the amplifier circuit, and the second input end of the comparator is connected with reference voltage; the controller is connected with the output end of the comparator, the output end of the amplifier circuit and the control end of each switching tube; and the output end of the pulse generator is connected with the tested sample capacitor. The partial discharge measuring device provided by the utility model solves the technical problems of low resolution and easy overrange in the prior art.

Description

Technical Field

[0001] The utility model belongs to the technical field of circuits, and in particular relates to a partial discharge measuring device. Background Art

[0002] When measuring partial discharge using the pulse current method, the measurement circuit is divided into two types: narrowband method and broadband method.

[0003] The lower limit detection frequency of the broadband detection method is between 30 and 100 kHz, the upper limit detection frequency is <500 kHz, and the detection bandwidth is 100 to 400 kHz. It has the advantages of high pulse resolution and relatively rich information, but low signal-to-noise ratio.

[0004] The narrowband detection method has a small bandwidth, generally 9 to 30 kHz, and a center frequency of 50 kHz to 1 MHz. It has the advantages of high sensitivity and strong anti-interference ability, but has the disadvantages of low pulse resolution and insufficient information.

[0005] In the narrowband partial discharge test, when the product under test is subjected to high voltage, partial discharge will be formed inside. The discharge amount is related to the measured voltage. When the measured voltage exceeds the threshold voltage, partial discharge occurs.

[0006] If the capacitance of the product under test is large, the partial discharge signal will be small and the resolution will be low.

[0007] If the capacitance of the product under test is very small, the partial discharge signal will be very large. Although the resolution is high, an over-range problem will occur, affecting circuit safety. Summary of the invention

[0008] The utility model provides a partial discharge measuring device, which solves the technical problems of low resolution and easy over-range in the prior art.

[0009] In order to achieve the above technical objectives, the utility model adopts the following technical solutions:

[0010] A partial discharge measuring device, comprising:

[0011] a high voltage source having a positive output terminal and a negative output terminal;

[0012] A coupling capacitor, one end of which is connected to the positive output end, and the other end of which is connected to the negative output end;

[0013] A detection resistor, one end of which is connected to the positive output end through the capacitor of the sample under test, and the other end of which is connected to the negative output end;

[0014] A detection circuit, comprising a plurality of detection branches connected in parallel, each detection branch comprising a detection capacitor and a switch tube, the detection capacitor being connected in series with a switch path of the switch tube; the capacitance values ​​of the plurality of detection capacitors of the detection circuit are different; the detection branch is connected in parallel with the detection resistor;

[0015] an amplifier circuit, a first input terminal of which is connected to one end of the detection resistor, and a second input terminal of which is connected to the other end of the detection resistor;

[0016] a comparator, a first input terminal of which is connected to the output terminal of the amplifier circuit, and a second input terminal of which is connected to a reference voltage;

[0017] A controller, wherein a first input end thereof is connected to the output end of the comparator, a second input end thereof is connected to the output end of the amplifier circuit, and an output end thereof is respectively connected to the control end of each of the switch tubes;

[0018] A pulse generator, an output end of which is connected to the capacitor of the sample under test.

[0019] In some embodiments of the present application, the switch tube is a triode or a MOS tube.

[0020] In some embodiments of the present application, the switch tube is an NPN transistor.

[0021] In some embodiments of the present application, the detection circuit includes three detection branches connected in parallel.

[0022] In some embodiments of the present application, the partial discharge measurement device further includes a peak holding circuit;

[0023] The output end of the amplifier circuit is connected to the first input end of the comparator through the peak holding circuit;

[0024] The output end of the amplifier circuit is connected to the second input end of the controller through the peak holding circuit.

[0025] In some embodiments of the present application, the partial discharge measurement device further includes an ADC;

[0026] The peak holding circuit is connected to the second input terminal of the controller through the ADC.

[0027] In some embodiments of the present application, the amplifier circuit includes a first amplifier and a second amplifier;

[0028] The first amplifier has a first input end connected to one end of the detection resistor, a second input end connected to the other end of the detection resistor, and an output end connected to the first input end of the second amplifier;

[0029] A second input terminal of the second amplifier is grounded, and an output terminal of the second amplifier is connected to an input terminal of the peak holding circuit.

[0030] In some embodiments of the present application, an LCR resonant circuit is connected between the first amplifier and the second amplifier.

[0031] In some embodiments of the present application, the high voltage source is a transformer, and the high voltage side of the transformer has the positive output terminal and the negative output terminal.

[0032] In some embodiments of the present application, the positive output terminal is also connected to a filter resistor.

[0033] Compared with the prior art, the advantages and positive effects of the utility model are as follows: the partial discharge measuring device of the utility model, by designing a detection circuit including a plurality of detection branches in parallel, each detection branch including a detection capacitor and a switch tube, the detection capacitor being connected in series with the switch path of the switch tube; the capacitance values ​​of the plurality of detection capacitors of the detection circuit are different; the detection branch is connected in parallel with the detection resistor; by designing a comparator, the output voltage of the comparison amplifier circuit is compared with the reference voltage, the controller controls the on and off of the switch tube according to the output of the comparator, thereby connecting the detection capacitor with a suitable capacitance, and then the second input end of the controller can obtain a voltage signal with high resolution and without over-range, which not only improves the resolution of the apparent discharge quantity, but also avoids the over-range problem, and solves the technical problem of low resolution and easy over-range of partial discharge signals in the prior art.

[0034] After reading the detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become more clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0036] Figure 1 It is the principle block diagram of the existing partial discharge measurement circuit;

[0037] Figure 2 It is the charge distribution network diagram of partial discharge instant;

[0038] Figure 3 It is a circuit principle block diagram of an embodiment of the partial discharge measuring device proposed by the utility model;

[0039] Figure 4This is a circuit principle block diagram of another embodiment of the partial discharge measuring device proposed by the utility model. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0041] It should be noted that in the description of the present invention, the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element 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" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0042] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" 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 communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0043] Figure 1 The principle block diagram of the existing partial discharge measurement circuit using the narrowband method is shown.

[0044] The narrowband method is used to measure partial discharge. The circuit structure is generally as follows: Figure 1 As shown, the transformer generates the required high voltage, the resistor R plays a filtering role, and C K , C x , R D and C D Composed of coupling network, where C K It is a coupling capacitor, which is used to couple the pulse signal generated by the partial discharge of the sample to the detection impedance, and the coupling capacitor C K It plays the role of isolating the power frequency high voltage. x is the capacitance of the sample under test, R D and C D is the detection resistor and the detection capacitor. The measurement circuit detects C D The charge on the electrode is called the apparent charge.

[0045] When the sample produces partial discharge, the charge at both ends of the sample is q aIf the test circuit is not connected to both ends of the sample, the voltage change at both ends of the sample is If the test circuit is connected, Since the pulse voltage rise time is very short, in the above test circuit, C K , C D The initial value of the voltage on the upper resistor can be regarded as inversely proportional to its capacitance. At this time, the initial value of the voltage across the detection resistor is It can be seen that q a with U D Proportional to U D The signal passes through op amp G1 and then through L A , C A , R A The LCR resonant circuit formed by the amplifier generates a voltage signal with a fixed frequency, which is then amplified by the operational amplifier G2 and the maximum peak value of the signal is extracted through the peak holding circuit, and then enters the MCU through the ADC.

[0046] Discharge instant C K , C x , C D The charge distribution network between Figure 2 As shown, C K and C D in series, and then with C x in parallel.

[0047] In the partial discharge test, when the sample under test is subjected to high voltage, partial discharge will be formed inside. The discharge amount is related to the test voltage. When the test voltage exceeds the threshold voltage, partial discharge occurs.

[0048] When the sample is partially discharged, the discharge amount is calculated by the following formula:

[0049]

[0050] From the above equation, it can be concluded that when q a When fixed, the accuracy of pulse current measurement is determined by C K , C x , C D The ratio is determined by C. K , C D The value of is determined during product design. x When it is very large, U D The value will be very small, and the apparent discharge capacity resolution is low. x When I was very young, D The value will be very large, the measurement accuracy will be very high, and the resolution of the apparent discharge capacity will be high, but there will be an over-range problem.

[0051] Therefore, the partial discharge measurement device of the present application is designed with multiple detection capacitors with different capacitance values. The controller controls the on and off of the switch tube according to the output of the comparator, thereby connecting the detection capacitor with appropriate capacitance value to the circuit, which not only improves the measurement accuracy of the partial discharge signal, but also avoids the over-range problem.

[0052] The partial discharge measuring device of this embodiment includes a high voltage source, a coupling capacitor, a detection resistor, a detection circuit, an amplifier circuit, a comparator, a controller (MCU), a pulse generator, a capacitor of a sample to be tested, etc. Figure 3 shown.

[0053] The high voltage source has a positive output terminal and a negative output terminal. The high voltage source provides the high voltage required for the partial discharge test. In this embodiment, the negative output terminal is grounded.

[0054] Coupling capacitor C K , one end of which is connected to the positive output end of the high voltage source, and the other end of which is connected to the negative output end of the high voltage source.

[0055] Detection resistor R D , one end of which passes through the capacitor C x Connect the positive output terminal of the high voltage source, and the other end is connected to the negative output terminal of the high voltage source.

[0056] The detection circuit includes a plurality of detection branches connected in parallel, each detection branch includes a detection capacitor and a switch tube, and the detection capacitor is connected in series with the switch path of the switch tube; the capacitance values ​​of the plurality of detection capacitors of the detection circuit are different; the detection branch and the detection resistor R D in parallel.

[0057] The amplifier circuit has a first input terminal connected to a detection resistor R D The second input terminal is connected to the detection resistor R D The other end of the amplifier circuit is used to amplify the input signal.

[0058] A comparator, whose first input terminal is connected to the output terminal of the amplifier circuit, and whose second input terminal is connected to the reference voltage V ref . Reference voltage V ref Supplied by a DC power supply.

[0059] The controller has a first input end connected to the output end of the comparator, a second input end connected to the output end of the amplifier circuit, and an output end connected to the control end of each switch tube.

[0060] The pulse generator P1 has its output connected to the capacitor C of the sample under test. x The controller controls the operation of the pulse generator. The controller controls the pulse generator to supply the capacitor C x Injects a set charge.

[0061] Assume that the first input terminal of the comparator is the inverting input terminal, and the second input terminal is the non-inverting input terminal. Assume that there are n detection branches, there are n switch tubes, n detection capacitors, and the capacitance values ​​of the n detection capacitors are different. The capacitance value of the first detection capacitor is the smallest, and the capacitance value of the nth detection capacitor is the largest.

[0062] The controller turns on one of the switches and turns off the other switches. The corresponding detection capacitor is connected to the circuit. The pulse generator P1 sends a pulse to the capacitor C x Inject set charge q a , the voltage U across the detection capacitor D After being amplified by the amplifier circuit, it is transmitted to the comparator and the controller respectively. The comparator compares the input voltage with the reference voltage and outputs the comparison result to the controller.

[0063] If the comparator outputs a high level to the controller, it means that the capacitance of the detection capacitor is appropriate, and the voltage U across the detection capacitor is D The second input terminal of the controller receives a voltage signal with high resolution and within the range. The voltage signal received by the second input terminal of the controller is the voltage U across the detection capacitor. D , has a known proportional relationship. The controller can obtain U according to the voltage signal received by the second input terminal. D .

[0064] If the comparator outputs a low level to the controller, it means that the capacitance of the detection capacitor is not appropriate, and a new detection capacitor is selected to connect to the circuit.

[0065] Working principle:

[0066] The controller turns on the first switch tube K1 and turns off the other switches. The corresponding first detection capacitor C D1 When the circuit is connected, the pulse generator P1 sends a pulse to the capacitor C x Inject set charge q a , detection capacitor C D1 The voltage across the two ends is U D After being amplified by the amplifier circuit, they are transmitted to the comparator and the controller respectively.

[0067] If the voltage transmitted to the comparator is less than the reference voltage, the output of the comparator outputs a high level. When the controller receives the high level signal from the comparator, it knows the first detection capacitor C D1 The capacitance value is appropriate.

[0068] If the voltage transmitted to the comparator is higher than the reference voltage, the output of the comparator outputs a low level. When the controller receives the low level signal from the comparator, it knows the first detection capacitor C D1The capacitance value is small, then the second switch tube K2 is controlled to be turned on, and the other switches are turned off. The corresponding second detection capacitor C D2 Connect to the circuit, and then the pulse generator P1 sends a pulse to the capacitor C x Inject set charge q a , detection capacitor C D2 The voltage across the two ends is U D After being amplified by the amplifier circuit, it is transmitted to the comparator and controller.

[0069] If the voltage transmitted to the comparator is less than the reference voltage, the output of the comparator outputs a high level. When the controller receives the high level signal from the comparator, it knows that the second detection capacitor C D2 The capacitance value is appropriate.

[0070] If the voltage transmitted to the comparator is higher than the reference voltage, the output of the comparator outputs a low level. When the controller receives the low level signal from the comparator, it knows that the second detection capacitor C D2 The capacitance value is small, then the third switch tube K3 is controlled to be turned on, and the other switches are turned off. The corresponding third detection capacitor C D3 Connect to the circuit, and then the pulse generator P1 sends a pulse to the capacitor C x Inject set charge q a , detection capacitor C D3 The voltage across the two ends is U D After being amplified by the amplifier circuit, it is transmitted to the comparator and controller.

[0071] If the voltage transmitted to the comparator is less than the reference voltage, the output of the comparator outputs a high level. When the controller receives the high level signal from the comparator, it knows that the third detection capacitor C D3 The capacitance value is appropriate.

[0072] If the voltage transmitted to the comparator is higher than the reference voltage, the output of the comparator outputs a low level. When the controller receives the low level signal from the comparator, it knows that the third detection capacitor C D3 If the capacitance is small, the next switch tube will be controlled to turn on and the other switches will be turned off.

[0073] Therefore, the partial discharge measuring device of this embodiment is designed to include a plurality of parallel detection branches by designing a detection circuit, each detection branch includes a detection capacitor and a switch tube, and the detection capacitor is connected in series with the switch path of the switch tube; the capacitance values ​​of the plurality of detection capacitors of the detection circuit are different; the detection branch is connected in parallel with the detection resistor; by designing a comparator, the output voltage of the comparison amplifier circuit is compared with the reference voltage, and the controller controls the on and off of the switch tube according to the output of the comparator, thereby connecting the detection capacitor with appropriate capacitance, and then the second input end of the controller can obtain a voltage signal with high resolution and without over-range, which not only improves the resolution of the apparent discharge quantity, but also avoids the over-range problem, and solves the technical problem of low resolution and easy over-range in the prior art.

[0074] The controller controls the power supply and gear position of the pulse generator P1. Different gear positions generate different amounts of charge. The high voltage source does not work. The controller controls the pulse generator to supply a charge to the capacitor C x Inject set charge q a According to the voltage signal received by the second input terminal of the controller, the voltage U across the detection capacitor can be obtained. D , due to U D ,q a , C K , C D The capacitance value is known, according to The capacitance C of the sample under test can be calculated x Capacitance value.

[0075] Here C D is the capacitance of the detection capacitor connected to the circuit, such as C D1 , C D2 or C D3 .

[0076] The pulse generator can be used to easily test the capacitance C of the sample under test. x Capacitance value.

[0077] The controller selects the appropriate detection capacitor through the output of the comparator and calculates the capacitance C of the sample under test. x After the capacitance value is reached, the pulse generator P1 stops working, the high voltage source starts working, and the formal test begins. Under the high voltage output by the high voltage source, the tested sample partially discharges, and the controller can receive a local discharge signal with high accuracy and within the range.

[0078] In some embodiments of the present application, in order to capture the peak value of the partial discharge signal and improve the measurement accuracy of the partial discharge signal, the partial discharge measurement device further includes a peak holding circuit, see Figure 4 shown.

[0079] The output end of the amplifier circuit is connected to the first input end of the comparator through the peak holding circuit; the output end of the amplifier circuit is connected to the second input end of the controller through the peak holding circuit.

[0080] The output end of the amplifier circuit is connected to the input end of the peak holding circuit, and the output end of the peak holding circuit is respectively connected to the first input end of the comparator and the second input end of the controller.

[0081] In some embodiments of the present application, an ADC (analog-to-digital converter) is integrated inside the controller to facilitate analog-to-digital conversion.

[0082] In some other embodiments of the present application, in order to reduce the cost of the controller, the controller and the ADC are independently provided, and therefore, the partial discharge measurement device further includes an ADC; and the peak holding circuit is connected to the second input terminal of the controller via the ADC.

[0083] The output end of the peak holding circuit is connected to the input end of the ADC, and the output end of the ADC is connected to the second input end of the controller.

[0084] In some embodiments of the present application, in order to better amplify the signal, the amplifier circuit includes a first amplifier G1 and a second amplifier G2.

[0085] The first amplifier G1 has a first input terminal connected to one end of the detection resistor, a second input terminal connected to the other end of the detection resistor, and an output terminal connected to a first input terminal of the second amplifier G2.

[0086] A second input terminal of the second amplifier G2 is grounded, and an output terminal of the second amplifier G2 is connected to an input terminal of the peak holding circuit.

[0087] In some embodiments of the present application, an LCR resonant circuit is connected between the first amplifier G1 and the second amplifier G2. The LCR resonant circuit is used to generate a voltage signal with a fixed frequency to ensure that the second amplifier G2 has a stable input signal.

[0088] In some embodiments of the present application, the LCR resonant circuit includes a resonant inductor L A , resonant capacitor C A , resonant resistance R A ; Resonant inductance L A , resonant capacitor C A A resonant resistor R is connected in series between the output terminal of the first amplifier G1 and the first input terminal of the second amplifier G2; A Connected between the two input terminals of the second amplifier G2.

[0089] In some embodiments of the present application, the high voltage source is a transformer having a low voltage side and a high voltage side. The high voltage side of the transformer has a positive output terminal and a negative output terminal, which provides high voltage to the test sample, causing partial discharge of the test sample.

[0090] By designing a transformer as a high voltage source, low voltage input and high voltage output can be achieved, which is convenient for control.

[0091] In some embodiments of the present application, a filter resistor R is also connected to the positive output end of the transformer to filter out clutter.

[0092] In some embodiments of the present application, the switch tube is a triode or a MOS tube, which is convenient for controlling on and off, has low cost and stable performance.

[0093] In some embodiments of the present application, the switch tube is an NPN transistor, which is easy to control and has stable performance.

[0094] In some embodiments of the present application, the detection circuit includes three detection branches connected in parallel. Each detection branch includes a detection capacitor and a switch tube. The capacitance values ​​of the three detection capacitors are different.

[0095] By designing three detection branches, there are three detection capacitors with different capacitances that can be selected for connection to the circuit, which can avoid the lack of detection capacitors with suitable capacitance due to too few detection branches, and the complexity of the circuit due to too many detection branches. Designing three detection branches can ensure the measurement accuracy of partial discharge signals and avoid exceeding the range.

[0096] The following describes the working process of the partial discharge measuring device in detail by taking the detection circuit having three detection branches as an example.

[0097] After the sample under test generates partial discharge, the voltage U across the capacitor is detected. D After passing through operational amplifier G1, it passes through L A , C A , R A The LCR resonant circuit formed by the circuit generates a voltage signal with a fixed frequency, which is then amplified by the operational amplifier G2 and the maximum peak value of the signal is extracted through the peak holding circuit. The signal then enters the MCU through the ADC and enters the inverting input terminal of the comparator.

[0098] See also Figure 4 As shown, the three detection capacitors C D1 C D2 C D3 The capacitance value increases successively and is known to be

[0099] Three detection capacitors C D1 C D2 C D3 Correspondingly, three switch tubes K1, K2, and K3 are connected in series.

[0100] (1) Connect the test device to the sample under test, close K1, open K2 and K3, and detect the capacitance C D1Before the formal test begins, the high voltage source does not work, and the MCU controls the pulse generator P1 to supply the capacitor C x Inject a predetermined discharge amount q a , the comparator and ADC will receive a pulse voltage V1. The pulse voltage V1 is D With a known proportional relationship, U can be obtained according to the pulse voltage V1. D , due to U D ,q a , C K , C D1 The value of is known, through C can be calculated x The value of .

[0101] If 0≤V1<V ref , that is, the controller receives the high level output by the comparator, indicating that the detection capacitor C D1 If the capacitance value is appropriate, the control pulse generator P1 stops working, the high voltage source sends out the voltage to be tested, and the formal test begins. During the formal test, under the high voltage of the high voltage source, the tested sample generates partial discharge, and the ADC receives the pulse voltage V1. Based on the known proportional relationship, U can be calculated based on V1. D , due to U D , C x , C K , C D1 The value of is known, through We can calculate q a This value is the discharge amount of the tested sample.

[0102] If V1>V ref , that is, the controller receives the low level output by the comparator, indicating that the detection capacitor C D1 The capacitance is small. At this time, the controller controls K1 and K3 to open and K2 to close, and detects the capacitance C. D2 Connect to the circuit.

[0103] (2) Detection capacitor C D2 After the circuit is connected, the high voltage source does not work, and the MCU controls the pulse generator P1 to pass the test sample capacitor C x Inject a predetermined discharge amount q a , the comparator and ADC will receive a pulse voltage V1.

[0104] If 0≤V1<V ref , that is, the controller receives the high level output by the comparator, indicating that the detection capacitor C D2If the capacitance value is appropriate, the control pulse generator P1 stops working, the high voltage source sends out the voltage to be tested, and the formal test begins. During the formal test, under the high voltage of the high voltage source, the tested sample generates partial discharge, and the ADC receives the pulse voltage V1. Based on the known proportional relationship, U can be calculated based on V1. D , due to U D , C x , C K , C D2 The value of is known, through We can calculate q a This value is the discharge amount of the tested sample.

[0105] If V1>V ref , that is, the controller receives the low level output by the comparator, indicating that the detection capacitor C D2 The capacitance is small. At this time, the controller controls K1 and K2 to open and K3 to close, and detects the capacitance C. D3 Connect to the circuit.

[0106] (3) Detection capacitor C D3 After the circuit is connected, the high voltage source does not work, and the MCU controls the pulse generator P1 to pass the test sample capacitor C x Inject a predetermined discharge amount q a , the comparator and ADC will receive a pulse voltage V1.

[0107] If 0≤V1<V ref , that is, the controller receives the high level output by the comparator, indicating that the detection capacitor C D3 If the capacitance value is appropriate, the control pulse generator P1 stops working, the high voltage source sends out the voltage to be tested, and the formal test begins. During the formal test, under the high voltage of the high voltage source, the tested sample generates partial discharge, and the ADC receives the pulse voltage V1. Based on the known proportional relationship, U can be calculated based on V1. D , due to U D , C x , C K , C D3 The value of is known, through We can calculate q a This value is the discharge amount of the tested sample.

[0108] If V1>V ref , that is, the controller receives the low level output by the comparator, indicating that the detection capacitor C D3 The capacitance is small, so a larger detection capacitor needs to be connected. For example, C D1 , C D2 Connect to the circuit at the same time, that is, the controller can control K3 to open and K1 and K2 to close.

[0109] Therefore, when the high voltage source is not working and the pulse generator P1 is connected to the capacitor C x Inject set charge q a When the discharge amount formula is used, the capacitance C of the sample under test can be calculated. x Furthermore, the controller connects a detection capacitor with a suitable capacitance according to the output of the comparator.

[0110] During the formal test, the pulse generator does not work, the high voltage source outputs high voltage, and the tested sample produces partial discharge. According to the discharge calculation formula, C x of discharge capacity.

[0111] The partial discharge measuring device of this embodiment uses a pulse generator to estimate the capacitance of the sample under test and adjust the capacitance of the detection capacitor, so as to accurately measure the partial discharge amount of the sample under test.

[0112] The partial discharge measuring device of this embodiment compares the discharge voltage through a comparator and dynamically selects the detection capacitor, which can meet the highest resolution of the apparent discharge quantity without over-range. The partial discharge measuring device of this embodiment solves the problem of selecting the detection capacitor for different tested samples, which not only improves the measurement accuracy of partial discharge, but also avoids over-range.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the utility model.

Claims

1. A partial discharge measuring device, characterized in that: include: a high voltage source having a positive output terminal and a negative output terminal; A coupling capacitor, one end of which is connected to the positive output end, and the other end of which is connected to the negative output end; A detection resistor, one end of which is connected to the positive output end through the capacitor of the sample under test, and the other end of which is connected to the negative output end; A detection circuit, comprising a plurality of detection branches connected in parallel, each detection branch comprising a detection capacitor and a switch tube, wherein the detection capacitor is connected in series with a switch path of the switch tube; The capacitance values ​​of the multiple detection capacitors of the detection circuit are different; the detection branch is connected in parallel with the detection resistor; an amplifier circuit, a first input terminal of which is connected to one end of the detection resistor, and a second input terminal of which is connected to the other end of the detection resistor; a comparator, a first input terminal of which is connected to the output terminal of the amplifier circuit, and a second input terminal of which is connected to a reference voltage; A controller, wherein a first input end thereof is connected to the output end of the comparator, a second input end thereof is connected to the output end of the amplifier circuit, and an output end thereof is respectively connected to the control end of each of the switch tubes; A pulse generator, an output end of which is connected to the capacitor of the sample under test.

2. The partial discharge measurement device according to claim 1, characterized in that: The switch tube is a triode or a MOS tube.

3. The partial discharge measurement device according to claim 1, characterized in that: The switch tube is an NPN transistor.

4. The partial discharge measurement device according to claim 1, characterized in that: The detection circuit includes three detection branches connected in parallel.

5. The partial discharge measuring device according to claim 1, characterized in that: The partial discharge measurement device also includes a peak holding circuit; The output end of the amplifier circuit is connected to the first input end of the comparator through the peak holding circuit; The output end of the amplifier circuit is connected to the second input end of the controller through the peak holding circuit.

6. The partial discharge measuring device according to claim 5, characterized in that: The partial discharge measurement device also includes an ADC; The peak holding circuit is connected to the second input terminal of the controller through the ADC.

7. The partial discharge measurement device according to claim 5, characterized in that: The amplifier circuit includes a first amplifier and a second amplifier; The first amplifier has a first input end connected to one end of the detection resistor, a second input end connected to the other end of the detection resistor, and an output end connected to the first input end of the second amplifier; A second input terminal of the second amplifier is grounded, and an output terminal of the second amplifier is connected to an input terminal of the peak holding circuit.

8. The partial discharge measuring device according to claim 7, characterized in that: An LCR resonant circuit is connected between the first amplifier and the second amplifier.

9. The partial discharge measurement device according to any one of claims 1 to 8, characterized in that: The high voltage source is a transformer, and the high voltage side of the transformer has the positive output terminal and the negative output terminal.

10. The partial discharge measurement device according to claim 9, characterized in that: The positive output terminal is also connected with a filter resistor.

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