Failure measurement device and method for metallized film capacitor

Abstract

The invention discloses a failure measurement device and method for a metallized film capacitor, and belongs to the field of high-voltage insulation testing. Acquiring various partial discharge characteristic parameters of the thin film sample by analyzing a direct current partial discharge signal of the thin film sample collected when the RLC circuit loses balance due to partial discharge of the sample; according to the device, a high-voltage direct-current power supply with a wide voltage output range is adopted to apply voltage to the RLC circuit, and the range of an electric field capable of being measured is wider; in addition, the adopted film sample adopts a form of overlapping multiple layers of films, so that the measurement precision can be improved; when the film leaves a factory, the measuring device provided by the invention is adopted to detect the partial discharge performance of the film, so that the poor-quality film can be screened out, and the later reinspection frequency is reduced; the measuring device provided by the invention has the advantages of simple structure, convenient measuring method, high operability and the like, and has important significance for researching the insulation failure condition of the capacitor under the mechanical stress.

Description

Technical Field

[0001] The present invention belongs to the field of high voltage insulation testing, and more specifically, relates to a failure measurement device and method for a metallized film capacitor. Background Art

[0002] Metallized film capacitors are widely used in high-voltage power systems. The DC partial discharge detection method can effectively detect the insulation performance of capacitors. During the production process of capacitor film, due to factors such as inaccurate chain clamp position, mechanical vibration, and unbalanced rollers through which the film passes during stretching and winding, the winding film will produce axial lateral tension to the left or right. Under the action of these tensions, the film will move axially, resulting in longitudinal and transverse stripes or wrinkles. These typical characteristics are electrical weak points in the entire roll of film. Partial discharge occurs in large numbers at these insulation weak points, seriously affecting the service life of the capacitor.

[0003] With the improvement of capacitor manufacturing technology and the increasing requirements for accurate measurement of failure behavior, the measurement of capacitor failure behavior has become an important task. Usually, the capacitance of capacitors is measured with a bridge, and the degree of capacitance loss is used to characterize the failure of capacitors. However, this method has the disadvantages of little characterization data and cumbersome regular component testing. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a failure measurement device and method for metallized film capacitors, thereby solving the technical problems of the existing measurement devices, such as small amount of characterization data and cumbersome regular component testing.

[0005] To achieve the above-mentioned object, according to a first aspect of the present invention, a failure measurement device for a metallized film capacitor is provided, comprising: a high-voltage DC power supply, an RLC circuit, an acquisition module and a processing module;

[0006] The high voltage DC power supply is used to apply voltage to the RLC circuit;

[0007] The RLC circuit includes an equivalent capacitance C of a two-electrode system 1 , reference capacitor C 2 , detection impedance Z 1 And adjustable impedance Z 2 ; C 1 With Z 1 Series, C 2 With Z 2 The two series branches are connected in parallel, one end of which is connected to the high voltage DC power supply, and the other end is grounded; Z 2Used to balance the RLC circuit; the two-electrode system includes a film sample and a two-electrode fixture for clamping the film sample, the number of the film samples is M, and each of the N polymer films cut from the target area of ​​the polymer film roll of the metallized film capacitor to be tested according to the same size is stacked; C 1 , C 2 The capacitance is equal, M and N are both greater than 1;

[0008] The acquisition modules are connected to C 1 With Z 1 Between, C 2 With Z 2 between, for collecting DC partial discharge signals of each thin film sample respectively when a high-voltage DC power supply applies voltage to the RLC circuit and a partial discharge occurs in the target sample and the RLC circuit loses balance;

[0009] The processing module is used to process the DC partial discharge signal of each thin film sample respectively to obtain the partial discharge characteristic parameters of each thin film sample, and use the average value of the partial discharge characteristic parameters of all thin film samples as the partial discharge characteristic parameters of the capacitor to be tested; wherein the partial discharge characteristic parameters of the capacitor to be tested include the average starting discharge voltage, the average number of discharges, the average discharge amount and the maximum discharge amount.

[0010] According to a second aspect of the present invention, a failure measurement method for a metallized film capacitor is provided, which is applied to a failure measurement device for a metallized film capacitor as described in the first aspect, comprising:

[0011] Each thin film sample is used as a target sample and operated to obtain the local discharge characteristic parameters of each thin film sample; the operation includes: clamping the target sample between the upper and lower electrodes of the two-electrode clamp, applying voltage to the RLC circuit with a high-voltage DC power supply, and if the RLC circuit is unbalanced, adjusting Z 2 The RLC circuit is balanced, and the high-voltage DC power supply continuously applies voltage to the RLC circuit. When partial discharge occurs in the target sample and the RLC circuit loses balance, a DC partial discharge signal of the target sample is collected and processed to obtain a partial discharge characteristic parameter of the target sample;

[0012] The average value of the partial discharge characteristic parameters of all the film samples is used as the partial discharge characteristic parameter of the capacitor to be tested.

[0013] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0014] The measuring device provided by the present invention realizes the balance of the RLC circuit through adjustable impedance, and obtains various local discharge characteristic parameters of the film sample, including the starting discharge voltage, the number of discharges and the discharge amount, by analyzing the DC local discharge signals of each film sample collected when the sample causes the RLC circuit to lose balance, and takes the average value of the local discharge characteristic parameters of all film samples as the local discharge characteristic parameters of the capacitor to be measured; the device uses a high-voltage DC power supply with a wide voltage output range to apply voltage to the RLC circuit, and can measure a wider electric field range, and can record and analyze the local discharge situation of the capacitor film under DC working conditions; In addition, considering that a single-layer film will not be used as a capacitor in actual applications, and the thickness (micrometer level) of a single-layer film is too small to be tightly clamped between the upper and lower electrodes of a two-electrode fixture, the film sample used is in the form of a multi-layer film stack to improve measurement accuracy; when the film leaves the factory, the measuring device provided by the present invention is used to detect the local discharge performance of the film, remove poor quality films, prevent capacitors wound with poor quality films from being put into use, and reduce the frequency of subsequent re-inspections; the measuring device provided by the present invention has the advantages of simple structure, convenient measurement method, strong operability, etc., and is of great significance for studying the insulation failure of capacitors under mechanical stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A structural diagram of a failure measurement device for a metallized film capacitor provided in an embodiment of the present invention;

[0016] Figure 2 It is the structure diagram of metallized film capacitor;

[0017] Figure 3 A structural diagram of a two-electrode system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0019] The embodiment of the present invention provides a failure measurement device for a metallized film capacitor, comprising: a high-voltage direct current power supply, an RLC circuit, a collection module, and a processing module;

[0020] The high voltage DC power supply is used to apply voltage to the RLC circuit;

[0021] The RLC circuit includes an equivalent capacitance C of a two-electrode system 1 , reference capacitor C 2, detection impedance Z 1 And adjustable impedance Z 2 ; C 1 With Z 1 Series, C 2 With Z 2 The two series branches are connected in parallel, one end of which is connected to the high voltage DC power supply, and the other end is grounded; Z 2 Used to balance the RLC circuit; the two-electrode system includes a film sample and a two-electrode fixture for clamping the film sample, the number of the film samples is M, and each of the N polymer films cut from the target area of ​​the polymer film roll of the metallized film capacitor to be tested according to the same size is stacked; C 2 The capacitance and C 1 The equivalent capacitance is close, so they are considered equal; M and N are both greater than 1;

[0022] The acquisition modules are connected to C 1 With Z 1 Between, C 2 With Z 2 between, used for respectively collecting DC partial discharge signals of each thin film sample when a high-voltage DC power supply applies voltage to the RLC circuit and a partial discharge occurs in the target sample and the RLC circuit loses balance;

[0023] The processing module is used to process the DC partial discharge signal of each film sample to obtain the partial discharge characteristic parameter of each film sample, and take the average value of the partial discharge characteristic parameters of all film samples as the partial discharge characteristic parameter of the capacitor to be tested; wherein, by repeated testing for multiple times, the DC partial discharge signal of each film sample is obtained and processed to obtain the partial discharge characteristic parameter of each film sample, and the partial discharge characteristic parameters of each film sample include: the starting discharge voltage U 0 , discharge times n, discharge amount Q, the local discharge characteristic parameters of the capacitor to be tested include the average starting discharge voltage Average discharge times Average discharge capacity Maximum discharge capacity Q max .

[0024] Specifically, Figure 1As shown, the acquisition module can use a digital acquisition card; the processing module can use computer software such as LabVIEW to extract the partial discharge characteristic parameters from the voltage and current waveforms (i.e., partial discharge signals) generated by partial discharge at the electrical weak points of the thin film sample. That is, the measuring device can adjust the balance of the RLC bridge through the adjustable impedance, and when partial discharge occurs in the target sample and the RLC circuit loses balance, the DC partial discharge signal of the thin film sample passes through the amplification circuit and the bandpass filter circuit, and is collected by the data acquisition card to the PC, and the partial discharge signal is displayed and analyzed and processed by the software to obtain the partial discharge characteristic parameters of the thin film sample.

[0025] It is understandable that after the high voltage DC power supply adds voltage to the RLC circuit, if the RLC circuit is unbalanced, then Z 2 The RLC circuit is balanced. If the RLC circuit has reached balance, no adjustment is required. The high-voltage DC power supply continues to apply a higher voltage to the RLC circuit. When local discharge occurs in the film sample and the RLC circuit loses balance, the acquisition module collects the voltage and current waveforms.

[0026] To avoid corona caused by poor contact between the film sample and the upper and lower electrodes of the two-electrode fixture, preferably, metal powder is evaporated on the upper and lower surfaces of the film sample, for example, silver powder is evaporated on both the upper and lower surfaces of the film sample.

[0027] Preferably, the amplification and filtering module disposed between the RLC circuit and the acquisition module is used to amplify and filter the DC partial discharge signal of the thin film sample to improve the measurement accuracy.

[0028] Preferably, the target area is any one of the first area, the second area or the third area; wherein the first area is at a first distance from the core axis of the polymer film roll, the second area is at a second distance from the outermost layer of the polymer film roll, and the third area is the outermost layer of the polymer film roll.

[0029] Considering that selecting film samples in multiple areas of the capacitor can more comprehensively reflect the insulation quality of the film roll and improve the credibility of the test results, preferably, the target area includes the first to third areas; wherein the first area is at a first distance from the core axis of the polymer film roll, the second area is at a second distance from the outermost layer of the polymer film roll, and the third area is the outermost layer of the polymer film roll;

[0030] The local discharge characteristic parameters of the capacitor to be tested include the average value of the local discharge characteristic parameters of all film samples corresponding to the first area, the average value of the local discharge characteristic parameters of all film samples corresponding to the second area, and the average value of the local discharge characteristic parameters of all film samples corresponding to the third area.

[0031] The structure of metallized film capacitor is as follows: Figure 2 As shown, it includes a roll of polymer film.

[0032] The first distance and the second distance can be set accordingly according to the actual size of the metallized film capacitor to be measured, the measurement requirements, etc., so that the first to third areas are the inner, middle and outer areas of the polymer film roll respectively. For example, for a polymer film roll with a radius of 2 cm, the first distance and the second distance can be set to 5 mm.

[0033] like Figure 3 As shown, the two-electrode fixture includes an upper electrode, a conductive column, a lower electrode, an upper insulating support plate, a lower insulating support plate, a fixing screw and a stainless steel screw rod;

[0034] The upper electrode is a circular flat electrode connected to the conductive column. The upper insulating support plate is provided with a guide groove for fixing the conductive column together with the fixing screw, thereby fixing the upper electrode; that is, the upper electrode can move up and down to clamp the thin film sample. After the thin film sample is placed on the lower electrode, the conductive column can be fixed by the fixing screw so that the sample is clamped between the upper and lower electrodes.

[0035] The lower electrode is a circular flat plate electrode;

[0036] The stainless steel wire rod is arranged between the upper insulating support plate and the lower insulating support plate.

[0037] The upper and lower insulating support plates are both mica plates.

[0038] An embodiment of the present invention provides a failure measurement method for a metallized film capacitor, which is applied to a failure measurement device for a metallized film capacitor as described in any of the above embodiments, comprising:

[0039] Each thin film sample is used as a target sample and operated to obtain the local discharge characteristic parameters of each thin film sample; the operation includes: clamping the target sample between the upper and lower electrodes of the two-electrode clamp, applying voltage to the RLC circuit with a high-voltage DC power supply, and if the RLC circuit is unbalanced, adjusting Z 2 The RLC circuit is balanced, and the high-voltage DC power supply continuously applies voltage to the RLC circuit. When partial discharge occurs in the target sample and the RLC circuit loses balance, a DC partial discharge signal of the target sample is collected and processed to obtain a partial discharge characteristic parameter of the target sample;

[0040] The average value of the partial discharge characteristic parameters of all the film samples is used as the partial discharge characteristic parameter of the capacitor to be tested.

[0041] Specifically, a thin film sample is placed between the upper and lower electrodes of the two-electrode system, and a voltage is applied to the RLC circuit through a high-voltage DC power supply. If the RLC circuit is unbalanced, Z is adjusted. 2 The RLC circuit is balanced, and the high voltage DC power supply continuously applies voltage to the RLC circuit. When partial discharge occurs in the target sample and the RLC circuit loses balance, Figure 1 As shown, the partial discharge signal of the film sample is transmitted to the digital acquisition card through the amplification and filtering module, and the computer reads the corresponding partial discharge characteristic parameters.

[0042] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A failure measurement device for a metallized film capacitor, characterized in that: include: High voltage DC power supply, RLC circuit, acquisition module and processing module; The high voltage DC power supply is used to apply voltage to the RLC circuit; The RLC circuit includes an equivalent capacitor C1 of a two-electrode system, a reference capacitor C2, a detection impedance Z1 and an adjustable impedance Z2; C1 is connected in series with Z1, C2 is connected in series with Z2, one end of the two series branches connected in parallel is connected to the high-voltage DC power supply, and the other end is grounded; Z2 is used to balance the RLC circuit; the two-electrode system includes a film sample and a two-electrode fixture for clamping the film sample, the number of the film samples is M, and they are respectively formed by stacking N polymer films cut from the target area of ​​the polymer film roll of the metallized film capacitor to be tested according to the same size; the capacitance of C1 and C2 is equal, and M and N are both greater than 1; The acquisition modules are respectively connected between C1 and Z1, and between C2 and Z2, and are used to respectively acquire DC partial discharge signals of each thin film sample when a high-voltage DC power supply applies voltage to the RLC circuit and partial discharge occurs in the target sample and the RLC circuit loses balance; The processing module is used to process the DC partial discharge signal of each thin film sample respectively to obtain the partial discharge characteristic parameters of each thin film sample, and use the average value of the partial discharge characteristic parameters of all thin film samples as the partial discharge characteristic parameters of the capacitor to be tested; wherein the partial discharge characteristic parameters of the capacitor to be tested include the average starting discharge voltage, the average number of discharges, the average discharge amount and the maximum discharge amount.

2. The device according to claim 1, characterized in that The target area is any one of the first area, the second area or the third area; wherein the first area is at a first distance from the core axis of the polymer film roll, the second area is at a second distance from the outermost layer of the polymer film roll, and the third area is the outermost layer of the polymer film roll.

3. The device according to claim 1, characterized in that The target area includes first to third areas; wherein the first area is at a first distance from the core axis of the polymer film roll, the second area is at a second distance from the outermost layer of the polymer film roll, and the third area is the outermost layer of the polymer film roll; The local discharge characteristic parameters of the capacitor to be tested include the average value of the local discharge characteristic parameters of all film samples corresponding to the first area, the average value of the local discharge characteristic parameters of all film samples corresponding to the second area, and the average value of the local discharge characteristic parameters of all film samples corresponding to the third area.

4. The device according to any one of claims 1 to 3, characterized in that: Metal powder is evaporated on the upper and lower surfaces of the film sample.

5. The device according to claim 1, characterized in that Also includes: An amplifying and filtering module is arranged between the RLC circuit and the acquisition module.

6. The device according to claim 1, characterized in that The two-electrode fixture comprises an upper electrode, a conductive column, a lower electrode, an upper insulating support plate, a lower insulating support plate, a fixing screw and a stainless steel screw rod; The upper electrode is a circular flat plate electrode connected to the conductive column. The upper insulating support plate is provided with a guide groove for fixing the conductive column together with a fixing screw, thereby fixing the upper electrode; The lower electrode is a circular flat plate electrode; The stainless steel wire rod is arranged between the upper insulating support plate and the lower insulating support plate.

7. A failure measurement method for a metallized film capacitor, applied to a failure measurement device for a metallized film capacitor as claimed in any one of claims 1 to 6, characterized in that: include: Taking each thin film sample as a target sample and performing operations to obtain the local discharge characteristic parameters of each thin film sample; The operation includes: clamping the target sample between the upper and lower electrodes of the two-electrode clamp, applying voltage to the RLC circuit with a high-voltage direct current power supply, and if the RLC circuit is unbalanced, adjusting Z2 to balance the RLC circuit, and continuously applying voltage to the RLC circuit with the high-voltage direct current power supply, and when partial discharge occurs in the target sample and the RLC circuit loses balance, collecting the DC partial discharge signal of the target sample and processing it to obtain the partial discharge characteristic parameters of the target sample; The average value of the partial discharge characteristic parameters of all the film samples is used as the partial discharge characteristic parameter of the capacitor to be tested.

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