A partial discharge coupling device

Abstract

The application relates to a partial discharge coupling device, which comprises a measuring resistor, a parallel inductor, a measuring capacitor, an overvoltage protector P1, an overvoltage protector P2, a partial discharge pulse output end, an AC test voltage output end and a grounding end; the measuring resistor is connected in series with the measuring capacitor, and the grounding end is connected to the measuring capacitor; the parallel inductor is connected in parallel with the measuring resistor, and the partial discharge pulse output end and the AC test voltage output end are connected to two ends of the parallel inductor; the overvoltage protector P1 is connected in parallel with the measuring resistor and the measuring capacitor; the first end of the overvoltage protector P2 is connected between the second end of the parallel inductor and the AC test voltage output end, and the second end of the overvoltage protector P2 is connected between the second end of the measuring capacitor and the grounding end. Compared with the prior art, the application has the advantages of integration, convenient use and the like, realizes the coupling device for completely separating the partial discharge pulse and the test voltage, avoids the need of installing a high-voltage voltage divider in the traditional test loop, and has the advantages of small size and low cost.

Description

Technical Field

[0001] This invention relates to the field of partial discharge detection technology, and in particular to a partial discharge coupling device. Background Technology

[0002] The sensitivity, resolution, and waveform characteristics of partial discharge (PD) measurements in high-voltage electrical equipment are directly affected by the detection impedance, i.e., the coupling device (CD). In practice, an appropriate coupling device (CD) should be selected based on the specific testing objective, the type of test sample, and the type of testing instrument used to achieve the desired testing results. The coupling device (CD) generally consists of a resistor... R ,capacitance C ,inductance L These components are used individually or in combination, and are typically employed. Figure 1 The types shown are: R-type, RC-type, L-type, LC-type, and RLC-type.

[0003] Figure 2 The diagram shows a typical PD test circuit using the pulse current method, under a certain test voltage. U Under the action of the test sample C a When a transient voltage drop (PD) occurs internally, a corresponding transient voltage drop will inevitably be generated across the test sample. However, when a PD does not occur, the test sample will not experience a transient voltage drop. C a With coupling capacitor C k The voltages at both ends are equal. Because C a A transient voltage drop across the terminals will cause C k The voltage across the terminals will be higher (or lower) than (or lower than) the specified voltage. C a The current voltage at both ends makes C k Immediately C a Charging (because the charging time constant of the power supply circuit is large, the power supply has not yet had time to charge the circuit) C a (Charging). That is, a charging pulse current is generated throughout the entire test circuit, and this pulse current generates a pulse voltage on the coupling device CD. U z , U z This refers to the PD signal measured by the measuring instrument MI.

[0004] However, since the generation of the PD signal is related to the applied test voltage U, the measuring instrument MI also needs to be connected to the high-voltage divider in the test circuit. Figure 2 (Not specified in the text) Connect to obtain the test voltage. U The waveform and other information are inconvenient to use, and require a large carrying and storage space. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a partial discharge coupling device with advantages such as integration and ease of use. It realizes the coupling device that completely separates the output of partial discharge pulse and test voltage, avoiding the need to install a high voltage divider in the traditional test circuit. It is small in size and inexpensive.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A partial discharge coupling device, comprising:

[0008] Measuring resistance, parallel inductors, measuring capacitance, overvoltage protectors P 1. Overvoltage protector P 2. Partial discharge pulse output terminal, AC test voltage output terminal, and grounding terminal;

[0009] The first end of the measuring resistor is a terminal, the second end of the measuring resistor is connected to the first end of the measuring capacitor, the measuring resistor and the measuring capacitor are connected in series, and the grounding terminal is connected to the second end of the measuring capacitor.

[0010] The first end of the parallel inductor is connected to the first end of the measuring resistor, the second end of the parallel inductor is connected to the second end of the measuring resistor, the parallel inductor and the measuring resistor are connected in parallel, the partial discharge pulse output terminal is connected to the first end of the parallel inductor, and the AC test voltage output terminal is connected to the second end of the parallel inductor.

[0011] The overvoltage protector P The first terminal of 1 is connected to the first terminal of the measuring resistor, and the overvoltage protector is also connected. P The second terminal of 1 is connected to the second terminal of the measuring capacitor, which is the overvoltage protector. P 1. Connected in parallel with the measuring resistor and the measuring capacitor;

[0012] The overvoltage protector P The first end of 2 is connected to the first connection point, which is located between the second end of the parallel inductor and the AC test voltage output terminal. (Overvoltage protector) P The second end of 2 is connected to the second connection point, which is located between the second end of the measuring capacitor and the grounding end.

[0013] Furthermore, the partial discharge pulse output terminal and the AC test voltage output terminal are signal output terminals used to connect to measuring instruments.

[0014] Furthermore, the coupling device is connected in series with the coupling capacitor.

[0015] Furthermore, the coupling device is connected in series with the sample.

[0016] Furthermore, the coupling device measures at the sleeve tap.

[0017] Furthermore, the coupling device measures the self-excited sample.

[0018] Furthermore, the calculated relationship between the measured resistance, the detection lower limit frequency, and the coupling capacitance is as follows:

[0019] f 1 = 1 / (2π * C k * R m )

[0020] in, f 1 represents the lower limit frequency for detection. C k This is the capacitance value of the coupling capacitor. R m To measure the resistance value.

[0021] Furthermore, the capacitance impedance of the coupling capacitor is:

[0022] Z c = 1 / (2π * f ac * C k )

[0023] in, f ac The excitation frequency.

[0024] Furthermore, the calculation relationship between the parallel inductor, the measured resistance, and the detection lower limit frequency is as follows:

[0025] L m > 10 * R m / (2π * f 1)

[0026] in, f 1 represents the lower limit frequency for detection. L m The inductance value of the parallel inductor R m To measure the resistance value.

[0027] Furthermore, the inductive impedance of the parallel inductor is:

[0028] Z l = 2π * f ac * L m

[0029] in, f ac The excitation frequency.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. Integrated design: This coupling device achieves complete separation of partial discharge pulse and test voltage output, making it convenient for users.

[0032] 2. Improved reliability and work efficiency: It avoids the need to install a high-voltage divider in traditional test circuits. The reduction of one high-voltage device improves the overall system reliability. In addition, it speeds up the construction and dismantling of test circuits, thus improving work efficiency.

[0033] 3. Small size and low cost: The resulting coupling device reduces the space required for carrying and storage, thus reducing the equipment purchase and maintenance costs of the high-voltage divider. Attached Figure Description

[0034] Figure 1 The circuit diagram of the existing coupling device CD;

[0035] Figure label: R—resistance; C d — Capacitor; L — Inductor;

[0036] Figure 2 Examples of PD test circuits using the pulse current method: (a) a coupling device connected in series with a coupling capacitor; (b) a coupling device connected in series with the test sample; (c) measurement at the bushing tap; and (d) measurement of a self-excited test sample.

[0037] Figure label: U —High voltage (HV) power supply; Z —Filter; C a —Sample; C k —Coupling capacitor; Z mi —Input impedance of the measurement system; CD —Coupled device; CC —Connecting cable; MI —Measuring instrument; OL —Optical connection;

[0038] Figure 3 This is a circuit diagram of a PD test detection loop that includes the coupling device of the present invention;

[0039] Figure label: (1) Sample To (2) Sample capacitance C a (3) Coupling capacitor C k (4) Coupling device CD (5) Measuring resistance R m (6) Parallel inductors L m (7) Measure capacitance C m (8) Overvoltage protector P 1; (9) Overvoltage protector P 2; (10) Partial discharge pulse output PD (11) AC test voltage output AC (12) Grounding terminal GD . Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them, and the scope of protection of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0041] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer and show the mating relationships between the components, some parts in the drawings have been appropriately scaled down, and the distances between the components have been increased or decreased.

[0042] In the description of the embodiments of this application, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly placed when the product of this application is used, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0043] In the description of the embodiments of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0044] Example 1:

[0045] A partial discharge coupling device, comprising:

[0046] Measuring resistance R m Parallel inductors L m Measure capacitance C m Overvoltage protector P 1. Overvoltage protector P 2. Partial discharge pulse output terminal PD AC test voltage output terminal AC and grounding terminal GD ; Measuring resistance R m The first terminal is the wiring terminal, used for measuring resistance. R m The second end is connected to the measuring capacitor. C m The first terminal measures the resistance. R m With measuring capacitance C m Series connection, ground terminal GD Connect to measure capacitance C m The second terminal; parallel inductor L m The first end is connected to the measuring resistor R m The first terminal, parallel inductor L m The second end is connected to the measuring resistor R m The second end, parallel inductor L m With measuring resistance R m Parallel connection, partial discharge pulse output terminal PD Connect parallel inductors L m The first terminal is the AC test voltage output terminal. AC Connect parallel inductorsL m The second terminal; overvoltage protector P The first terminal of 1 is connected to the measuring resistor. R m The first terminal, overvoltage protector P The second terminal of 1 is connected to the measuring capacitor. C m The second terminal, overvoltage protector P 1. Measuring resistance R m and measuring capacitance C m Parallel connection; overvoltage protector P The first end of 2 is connected to the first connection point, which is located in the parallel inductor. L m The second terminal is connected to the AC test voltage output terminal. AC Between, overvoltage protector P The second end of 2 is connected to the second connection point, which is set at the measurement capacitance. C m The second terminal and the ground terminal GD between.

[0047] In this embodiment, the coupling device and the coupling capacitor C k Used in series (i.e.) Figure 2 (a)), its structure is as follows Figure 3 As shown:

[0048] The measurement circuit includes the sample. T o (1) and its corresponding sample capacitance C a (2) Coupling capacitor C k (3) Coupling device CD (4) Coupling device CD (4) Including resistance measurement R m (5) Parallel inductors L m (6) Measure capacitance C m (7) Overvoltage protector P 1 (8) and overvoltage protector P 2(9) and grounding terminal GD (12), and partial discharge pulse output PD (10) and AC test voltage output AC (11) Two signal output terminals. Coupling device. CD (4) with coupling capacitor ( Ck After being connected in series with the sample ( T o That is, the parallel test sample capacitor ( C a This constitutes the detection circuit for the pulse current method PD test. Partial discharge pulse output. PD (10) and AC test voltage output AC (11) Connect the two signal output terminals to the measuring instrument MI ( Figure 3 (Not shown in the image).

[0049] Overvoltage protector P 1 (8) and overvoltage protector P 2(9) can be set according to the specific design. Under normal circumstances, the protection limit is 100V, that is, the value at the instrument input terminal is not greater than 100V.

[0050] Figure 3 The parameters for the PD test detection circuit diagram shown are calculated as follows:

[0051] Assume the following circuit parameters: Measuring resistance R m = 500 Ω, the lower detection limit frequency can be obtained. f 1 = 100 kHz, calculated according to the formula in GB / T 7354-2018:

[0052] f 1 = 1 / (2π * C k * R m (1)

[0053] Coupling capacitor C k The required capacitance value can be calculated using the following formula:

[0054] C k = 1 / ( 2π * f 1 * R m ) = 3.2 nF (2)

[0055] In this case, current flows through the coupling capacitor C k The amplitude of the alternating current may cause the measured resistance R m The voltage drop across the terminals is relatively high, which may damage the partial discharge pulse output. PD (10) and AC test voltage output AC(11) Input unit of connected instruments. For example, if used for inductive PD testing of power transformers. f ac Given an excitation frequency of 400 Hz, the calculated capacitance impedance of the coupling capacitor is:

[0056] Z c = 1 / (2π * f ac * C k ) = 1 / (2π * 400 Hz * 3.2 nF) = 125 kΩ (3)

[0057] but, f ac The voltage division ratio at 400 Hz is 500 Ω / 125 kΩ = 1 / 250. Therefore, assuming U ac = 500kV AC test voltage amplitude causes resistance measurement impedance R m The voltage drop across the resistor can reach as high as 500 kV / 250 = 2000 V. To reduce this dangerous voltage, the resistance is measured. R m By parallel inductor L m Diversion, such as Figure 3 As shown. At this point, the lower limit frequency will not decrease significantly. This condition is achieved in the following way:

[0058] L m > 10 * R m / (2π * f 1) = L m > 10 * R m / (2π * 100 kHz) = 8 mH (4)

[0059] For the previously assumed maximum test frequency f ac = 400 Hz, parallel inductor L m The inductor impedance is:

[0060] Z l = 2π * 400 Hz * L m = 20 Ω (5)

[0061] Parallel inductors L m and measuring resistance R m With coupling capacitor C k The resulting frequency division ratio after series connection is approximately 20 Ω / 125 kΩ = 1 / 6250. This means that the 500 kV test voltage level will now only be 80 V, or 500 kV / 6250.

[0062] Similarly, the test voltage is 500 kV, and the AC test voltage is... AC To attenuate to 100 V, a voltage division ratio of 1:5000 is required. For the aforementioned coupling capacitor... C k = 3.2 nF, measured capacitance C m This condition is met when the capacitance is 16 µF. Here, the capacitance is measured. C m With coupling capacitor C k This forms the low-voltage arm of the capacitor voltage divider.

[0063] Because the spectra of the PD pulse and the AC test voltage are very different, the two signals are at the partial discharge pulse output. PD (10) and AC test voltage output AC (11) is completely separated, which can satisfy the PD measurement system using an oscilloscope or a data acquisition device based on a high-speed acquisition card to display the PD pulse in a phase-resolved or voltage waveform manner.

[0064] The advantages of this invention are as follows:

[0065] 1. Integrated design: This coupling device achieves complete separation of partial discharge pulse and test voltage output, making it convenient for users.

[0066] 2. Improved reliability and work efficiency: It avoids the need to install a high-voltage divider in traditional test circuits. The reduction of one high-voltage device improves the overall system reliability. In addition, it speeds up the construction and dismantling of test circuits, thus improving work efficiency.

[0067] 3. Small size and low cost: The resulting coupling device reduces the space required for carrying and storage, thus reducing the equipment purchase and maintenance costs of the high-voltage divider.

[0068] Example 2:

[0069] In Example 1, the coupling device CD With coupling capacitor C k (3) Used in series (i.e.) Figure 2(a) Application form), resulting in, as Figure 3 The circuit diagram of the PD test detection loop shown is illustrated in this embodiment, and the coupling device... CD Used in series with the test sample (i.e.) Figure 2 (b) The application form), can also be used in other embodiments. Figure 2 (c) and Figure 2 (d) The self-excited sample is measured and measured at the tap of the sleeve. The principle is the same as in Example 1, which can be understood by those skilled in the art, and will not be repeated here.

[0070] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A partial discharge coupling device, characterized in that, include: Measuring resistance, parallel inductors, measuring capacitance, overvoltage protectors P 1. Overvoltage protector P 2. Partial discharge pulse output terminal, AC test voltage output terminal, and grounding terminal; The first end of the measuring resistor is a terminal, the second end of the measuring resistor is connected to the first end of the measuring capacitor, the measuring resistor and the measuring capacitor are connected in series, and the grounding terminal is connected to the second end of the measuring capacitor. The first end of the parallel inductor is connected to the first end of the measuring resistor, the second end of the parallel inductor is connected to the second end of the measuring resistor, the parallel inductor and the measuring resistor are connected in parallel, the partial discharge pulse output terminal is connected to the first end of the parallel inductor, and the AC test voltage output terminal is connected to the second end of the parallel inductor. The overvoltage protector P The first terminal of 1 is connected to the first terminal of the measuring resistor, and the overvoltage protector is also connected. P The second terminal of 1 is connected to the second terminal of the measuring capacitor, which is the overvoltage protector. P 1. Connected in parallel with the measuring resistor and the measuring capacitor; The overvoltage protector P The first end of 2 is connected to the first connection point, which is located between the second end of the parallel inductor and the AC test voltage output terminal. (Overvoltage protector) P The second end of 2 is connected to the second connection point, which is located between the second end of the measuring capacitor and the grounding end.

2. The partial discharge coupling device according to claim 1, characterized in that, The partial discharge pulse output terminal and the AC test voltage output terminal are signal output terminals used to connect to measuring instruments.

3. A partial discharge coupling device according to claim 1, characterized in that, The coupling device is connected in series with the coupling capacitor.

4. A partial discharge coupling device according to claim 1, characterized in that, The coupling device is connected in series with the sample.

5. A partial discharge coupling device according to claim 1, characterized in that, The coupling device measures at the sleeve tap.

6. A partial discharge coupling device according to claim 1, characterized in that, The coupling device measures the self-excited sample.

7. A partial discharge coupling device according to claim 1, characterized in that, The relationship between the measured resistance, the detection lower limit frequency, and the coupling capacitance is as follows: f 1 = 1 / (2π * C k * R m ) in, f 1 represents the lower limit frequency for detection. C k This is the capacitance value of the coupling capacitor. R m To measure the resistance value.

8. A partial discharge coupling device according to claim 7, characterized in that, The capacitance impedance of the coupling capacitor is: Z c = 1 / (2π * f ac * C k ) in, f ac The excitation frequency.

9. A partial discharge coupling device according to claim 8, characterized in that, The calculation relationship between the parallel inductor, the measured resistance, and the detection lower limit frequency is as follows: L m > 10 * R m / (2π * f 1) in, f 1 represents the lower limit frequency for detection. L m The inductance value of the parallel inductor R m To measure the resistance value.

10. A partial discharge coupling device according to claim 9, characterized in that, The inductive impedance of the parallel inductor is: Z l = 2π * f ac * L m in, f ac The excitation frequency.

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