CN107632241A - A kind of apparatus and method for testing paper oil insulation partial discharge characteristic - Google Patents

Abstract

The invention provides a device and method for testing the partial discharge characteristics of oil-paper insulation. The device includes: a needle plate defect electrode model, which is used to place the oil-soaked paperboard sample on the needle electrode and plate of the needle plate defect electrode model Between the electrodes, and connected to the AC power supply and DC power supply of the AC-DC composite voltage generating unit to measure the partial discharge of the oil-immersed cardboard sample; the AC-DC composite voltage generating unit is used to measure the partial discharge of the oil-immersed cardboard sample The discharge capacity provides AC power and DC power, wherein the DC power of the AC-DC composite voltage generating unit is connected to the plate electrode through the DC end protection resistor, and the DC power is connected in parallel with the filter capacitor and the resistor divider, the AC power is connected to the needle electrode, and the AC A coupling capacitor connected in parallel with the power supply; a detection unit, which is used to collect and analyze the partial discharge signal of the oil-immersed cardboard.

Description

A device and method for testing partial discharge characteristics of oil-paper insulation

technical field

The invention relates to the field of electric instrument measurement, and more particularly, to a device and method for testing the partial discharge characteristics of oil-paper insulation.

Background technique

With the emergence and development of the UHV DC transmission system, the insulation requirements of the converter transformer, which is the key equipment in the DC transmission system, have also increased accordingly. Due to the complex working voltage environment of the valve side winding of the converter transformer - AC voltage, DC voltage, AC-DC composite voltage, etc., the insulation problem is prominent, which will directly affect the stability of the entire DC transmission system.

In the DC transmission system, the converter transformer plays an irreplaceable important role, and its operating conditions directly affect the safety and reliability of the system operation. Among the many faults of converter transformers, the faults caused by the deterioration of dielectric insulation are not uncommon. Compared with the working voltage environment of the power transformer winding, the valve side winding of the converter transformer also bears the DC voltage, the AC-DC mixed voltage and the polarity reversal voltage when the power flow is reversed. As the main insulating medium of the converter transformer, the transformer oil and laminated cardboard have a large difference between the ratio of the dielectric constant of the oil and the cardboard (about 1:2) and the ratio of the resistivity (about 1:100), so in There is a big difference in the electric field distribution of the oil-paper composite insulation medium in the AC electric field distributed according to the dielectric constant and in the DC electric field distributed according to the resistivity. Based on the difference in electric field distribution, in order to take both into account, the corresponding insulation requirements for the valve side winding of the converter transformer are more stringent.

Because the uneven electric field will cause local electric field concentration, lead to partial discharge, and damage the insulation structure, the converter transformer will try to avoid uneven electric field during the design and installation process. However, in actual engineering, factors such as mechanical stress, processing technology, and equipment aging may cause sharp corners or edges of metal parts in the converter transformer, resulting in local electric field concentration. If the electric field exceeds the energy required to ionize the surrounding medium, partial discharges will occur at the insulation location, which will lead to equipment failure in severe cases. Therefore, the oil-paper insulation partial discharge test system is designed and invented, considering the influence of different voltage forms and different electric field forms on the partial discharge characteristics, which is in line with the operating conditions of oil-paper insulation in HVDC transmission systems.

At present, the test of partial discharge characteristics of oil-paper insulation is mainly carried out under AC voltage, and the partial discharge characteristics test of oil-impregnated paperboard (or oil paper, paperboard for short) under AC voltage cannot reflect the actual working environment. Partial discharge characteristics of impregnated paperboard.

Contents of the invention

In order to solve the problem in the background technology that testing oil-paper under AC voltage cannot reflect the partial discharge characteristics of oil-paper in the actual working environment, the present invention provides a device for testing the partial discharge characteristics of oil-paper insulation. The devices include:

A needle plate defect electrode model, which is used to measure the partial discharge of the oil-immersed cardboard sample placed between the needle electrode and the plate electrode of the needle plate defect electrode model;

The AC-DC composite voltage generating unit is used to provide AC power and DC power for measuring the partial discharge of the oil-immersed cardboard sample, wherein the DC power of the AC-DC composite voltage generating unit is connected to the plate electrode through the DC terminal protection resistor, and the AC power connected to needle electrodes;

The detection unit is used for collecting partial discharge signals of the oil-immersed cardboard and analyzing the characteristics of the partial discharge.

Preferably, the device further includes a display unit for displaying the analysis result of the partial discharge signal by the detection unit.

Preferably, neither the needle electrode nor the plate electrode of the needle-plate defect electrode model is grounded.

Preferably, the DC power supply and the AC power supply of the AC-DC composite voltage generating unit are grounded together.

Preferably, the measurement unit is a partial discharge instrument, the detection impedance inside the partial discharge instrument is connected to the coupling capacitor, and the coupling capacitor is connected in parallel with the AC power supply, so that the coupling capacitor and the detection impedance together form a complete The pulse loop detects the partial discharge signal on the side of the coupling capacitor through the detection impedance.

Preferably, a high-voltage probe is used to connect an oscilloscope to measure the AC voltage applied by the AC power source to the oil-soaked cardboard, and a resistor divider is connected between the DC receiving end of the oil-soaked cardboard and the ground to measure the DC voltage applied by the DC power source to the oil-soaked cardboard , wherein the resistor divider is connected in parallel with a filter capacitor, and the filter capacitor is used to filter out the ripple generated by the DC power supply.

Preferably, the AC power supply adopts a high-voltage harmonic power supply.

According to another aspect of the present invention, the present invention provides a method for testing the partial discharge characteristics of oil-paper insulation. The methods include:

Put the oil-soaked cardboard in the oil cup of the needle plate defect model, where one side of the cardboard is placed on the plate, and the other side is in contact with the tip of the needle plate;

Adjust the DC voltage output by the DC power supply to a preset voltage value, apply a DC voltage to the tested oil-soaked cardboard through the DC power supply, and gradually apply an AC voltage to the oil-soaked cardboard from zero through the AC power supply;

When the oil-impregnated paperboard produces a partial discharge signal for the first time, increase the preset DC voltage value and AC voltage value, and increase the preset DC voltage and AC voltage every time, within the preset sampling time Collect the partial discharge signal of the tested sample.

Preferably, the method further includes obtaining a phase-resolved partial discharge PRPD spectrum of the tested oil-impregnated paperboard according to the measured partial discharge quantities of the oil-impregnated paperboard at different voltage values and different development stages.

Preferably, the AC power supply is a high-voltage harmonic power supply. The AC power supply adopts a high-voltage harmonic source, which can output the superposition of multiple harmonics at the same time, and can separately control the voltage amplitude of each harmonic, so as to better simulate the actual working conditions in the DC transmission project.

Preferably, the ratio of the DC voltage to the AC voltage and the harmonic components of the AC voltage are changed to obtain the partial discharge characteristics of the oil-impregnated paperboard under different voltage forms.

Compared with the prior art, the technical solution provided by the present invention proposes a device and method for testing the partial discharge characteristics of oil-paper insulation. The technical solution makes the local The discharge process is closer to that of the actual transformer. In the partial discharge measurement device under the AC-DC composite voltage, the AC power supply can be a harmonic power supply. Different voltages can be obtained by changing the ratio of DC voltage to AC voltage and the harmonic components of AC voltage The partial discharge characteristics of the oil-impregnated paperboard under the form, and the oil cup of the needle plate defect model is used for the experiment, which is more similar to the situation of the field strength concentration point in the actual transformer due to the defect in the manufacturing process, so that it can be fully close to the actual working condition Under the premise of this method, the electrical properties of insulating paperboard materials under different AC and DC composite voltage types can be effectively analyzed.

Description of drawings

A more complete understanding of the exemplary embodiments of the present invention can be had by referring to the following drawings:

Fig. 1 is a structural diagram of a device for testing the partial discharge characteristics of oil-paper insulation according to a specific embodiment of the present invention;

Fig. 2 is the structural diagram of the pin plate defect electrode model of the device for testing the partial discharge characteristics of oil-paper insulation according to the specific embodiment of the present invention;

Fig. 3 is the flowchart of the method for testing the partial discharge characteristics of oil-paper insulation according to a specific embodiment of the present invention;

Fig. 4 is an embodiment of the PRPD spectrogram drawn by the method for testing the partial discharge characteristics of oil-paper insulation according to the specific embodiment of the present invention;

Fig. 5 is another embodiment of the PRPD spectrogram drawn by the method for testing the partial discharge characteristics of oil-paper insulation according to the specific embodiment of the present invention.

detailed description

Exemplary embodiments of the present invention will now be described with reference to the drawings; however, the present invention may be embodied in many different forms and are not limited to the embodiments described herein, which are provided for the purpose of exhaustively and completely disclosing the present invention. invention and fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings do not limit the present invention. In the figures, the same units/elements are given the same reference numerals.

Unless otherwise specified, the terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it can be understood that terms defined by commonly used dictionaries should be understood to have consistent meanings in the context of their related fields, and should not be understood as idealized or overly formal meanings.

Fig. 1 is a structural diagram of a device for testing partial discharge characteristics of oil-paper insulation according to a specific embodiment of the present invention. As shown in FIG. 1 , the device 100 includes a needle plate defect electrode model 101 , an AC and DC voltage generation unit 102 , a detection unit 103 and a display unit 104 .

Fig. 2 is a structure diagram of a pin plate defect electrode model of the device for testing the partial discharge characteristics of oil-paper insulation according to the specific embodiment of the present invention. As shown in FIG. 2 , the needle plate defect electrode model 101 includes a needle electrode 111 , a plate electrode 112 and an oil cup 113 . The pin plate defect model is designed to simulate the electric field concentration generated by sharp corners or edges of metal parts in the converter transformer in actual engineering.

A needle plate defect electrode model 101, which is used to measure the partial discharge of an oil-impregnated paperboard sample placed between the needle electrode 111 and the plate electrode 112 of the needle plate defect electrode model.

AC-DC composite voltage generation unit 102, which is used to provide AC power supply 121 and DC power supply 122 for measuring the partial discharge of the oil-soaked cardboard sample, wherein the DC power supply 122 of the AC-DC composite voltage generation unit 102 is connected to the DC terminal protection resistor 129 and The plate electrode 112 is connected, and the AC power source 121 is connected to the needle electrode 111 .

The detection unit 103 is used to collect the partial discharge signal of the oil-impregnated cardboard and analyze the partial discharge characteristics.

Preferably, the device further includes a display unit 104, which is used for displaying the analysis result of the partial discharge signal by the detection unit.

Preferably, neither the needle electrode nor the plate electrode of the needle-plate defect electrode model is grounded.

Preferably, the DC power supply and the AC power supply of the AC-DC composite voltage generating unit are grounded together.

Preferably, the detection unit 103 is a partial discharge instrument, the detection impedance inside the partial discharge instrument is connected to the coupling capacitor, and the coupling capacitor 126 is connected in parallel with the AC power supply 121, so that the coupling capacitor 126 is connected to the detection impedance on the AC side 131 and 131 together form a complete pulse loop, and the partial discharge signal is detected on the side of the coupling capacitor 126 through the detection impedance 131 .

Preferably, a high-voltage probe 125 is used to connect an oscilloscope 124 to measure the AC voltage applied by the AC power source 121 to the oil-soaked cardboard, and a resistor divider 128 is connected between the DC receiving end of the oil-soaked cardboard and the ground to measure the effect of the DC power source on the oil-soaked cardboard. The applied DC voltage, wherein the resistor divider 126 is connected in parallel with a filter capacitor 127, and the filter capacitor 127 is used to filter out the ripple generated by the DC power supply 122. When the device detects the discharge pulse, it records the DC voltage and AC voltage at both ends of the needle plate defect electrode model, and analyzes the detection unit 103 to obtain the partial discharge characteristics of the oil-immersed cardboard sample under the AC-DC composite voltage.

Preferably, the AC power supply adopts a high-voltage harmonic power supply.

According to another aspect of the present invention, the present invention provides a method for testing the partial discharge characteristics of oil-paper insulation.

Fig. 3 is a flowchart of a method for testing partial discharge characteristics of oil-paper insulation according to a specific embodiment of the present invention. As shown in FIG. 3 , the method 300 starts from step 301 .

In step 301, the oil-soaked cardboard is placed in the oil cup of the needle plate defect model, wherein one side of the cardboard is placed on the plate, and the other side is in contact with the tip of the needle plate.

The way to deal with oil-impregnated cardboard is to remove the water from the cardboard, place it in a vacuum oven, and dry it in a vacuum atmosphere at 120°C for 48 hours to remove the moisture absorbed by the cardboard and reduce the interference of moisture on aging. Through the pressure difference between the vacuum and the atmospheric pressure, the transformer oil is pumped into the vacuum oven through the hose, and injected into the oil cup where the insulating cardboard is located, soaked for more than 100 hours, so that the cardboard is fully immersed in oil, and then soaked in the treated oil The cardboard is placed in the oil cup of the needle board defect model in Figure 2, the cardboard is placed on the board electrode, and the tip of the needle electrode is close to the cardboard.

In step 302, adjust the DC voltage output by the DC power supply to a preset voltage value, apply a DC voltage to the tested oil-impregnated paperboard through the DC power supply, and gradually apply an AC voltage to the oil-impregnated paperboard through the AC power supply from zero.

In step 303, when it is measured that the oil-soaked paperboard produces a partial discharge signal for the first time, the preset DC voltage value and the AC voltage value are increased, and when the preset DC voltage and the AC voltage are increased each time, the preset The partial discharge signal of the tested sample is collected within the sampling time.

Preferably, the method further includes obtaining a phase-resolved partial discharge PRPD spectrum of the tested oil-impregnated paperboard according to the measured partial discharge quantities of the oil-impregnated paperboard at different voltage values and different development stages.

The partial discharge signal is detected by the partial discharge meter through the AC side coupling capacitance of the AC and DC voltage generation unit 102 . The applied AC and DC voltages gradually increase from 0. According to the ratio of 1 to 1 between the AC voltage and the DC voltage, step up the voltage in the order of DC first and then AC, and measure the partial discharge inception voltage of the oil-immersed cardboard sample. After the partial discharge occurs, the AC and DC voltage boost gradient is maintained, and the accumulated discharge within 300s is collected.

After testing, the partial discharge inception voltage of the oil-impregnated paperboard is about 14kV, and the PRPD spectrum accumulated for 300s under the AC-DC composite voltage in the initial discharge is shown in Figure 4.

Fig. 4 is an example of a PRPD (Phase Resolved Plus Sequence) spectrogram drawn by the method for testing the partial discharge characteristics of oil-paper insulation according to the specific embodiment of the present invention. It can be seen from the figure that the partial discharge is distributed in the positive and negative half cycles of the AC voltage.

With the increase of AC-DC composite voltage, the amount of partial discharge increases, and the discharge of oil-paper insulation continues to develop. The PRPD spectrum accumulated under AC-DC composite voltage for 300s in the development stage is shown in Figure 5.

Fig. 5 is another embodiment of the PRPD spectrogram drawn by the method for testing the partial discharge characteristics of oil-paper insulation according to the specific embodiment of the present invention. It can be seen from the figure that the phase distribution range of the partial discharge in the positive and negative half cycles of the AC voltage increases, and the peak value of the negative half cycle goes out to the area with a large partial discharge.

Preferably, the AC power supply is a high-voltage harmonic power supply.

Preferably, the ratio of the DC voltage to the AC voltage and the harmonic components of the AC voltage are changed to obtain the partial discharge characteristics of the oil-impregnated paperboard under different voltage forms.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise therein. All references to "a/the/the [means, component, etc.]" are to be construed openly as at least one instance of said means, component, etc., unless expressly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Claims (11)

1. A device for testing the partial discharge characteristics of oil-paper insulation, characterized in that the device comprises: A needle plate defect electrode model, which is used to measure the partial discharge of the oil-immersed cardboard sample placed between the needle electrode and the plate electrode of the needle plate defect electrode model; The AC-DC composite voltage generating unit is used to provide AC power and DC power for measuring the partial discharge of the oil-immersed cardboard sample, wherein the DC power of the AC-DC composite voltage generating unit is connected to the plate electrode through the DC terminal protection resistor, and the AC power connected to needle electrodes; The detection unit is used for collecting partial discharge signals of the oil-immersed cardboard and analyzing the characteristics of the partial discharge. 2. The device according to claim 1, characterized in that the device further comprises: a display unit, which is used for displaying the result of analyzing the partial discharge signal by the detection unit. 3. The device according to claim 1, characterized in that neither the needle electrode nor the plate electrode of the needle-plate defect electrode model is grounded. 4. The device according to claim 1, wherein the DC power supply and the AC power supply of the AC-DC composite voltage generating unit adopt a common ground mode. 5. The device according to claim 1, wherein the detection unit is a partial discharge instrument, the detection impedance inside the partial discharge instrument is connected to a coupling capacitor, and the coupling capacitor is connected in parallel with an AC power supply, so that The coupling capacitor and the detection impedance form a complete pulse loop on the AC side, and the partial discharge signal is detected on the coupling capacitor side through the detection impedance. 6. The device according to any one of claims 1 to 5, characterized in that a high-voltage probe is used to connect an oscilloscope to measure the AC voltage applied by the AC power supply to the oil-soaked cardboard, and between the DC receiving end of the oil-soaked cardboard and the ground A resistor divider is connected to measure the DC voltage applied by the DC power supply to the oil-soaked cardboard, wherein the resistor divider is connected in parallel with a filter capacitor, and the filter capacitor is used to filter out the ripple generated by the DC power supply. 7. The device according to claim 1, characterized in that the AC power source is a high-voltage harmonic power source. 8. A method for testing the partial discharge characteristics of oil-paper insulation, characterized in that the method comprises: Put the oil-soaked cardboard in the oil cup of the needle plate defect model, where one side of the cardboard is placed on the plate, and the other side is in contact with the tip of the needle plate; Adjust the DC voltage output by the DC power supply to a preset voltage value, apply a DC voltage to the tested oil-soaked cardboard through the DC power supply, and gradually apply an AC voltage to the oil-soaked cardboard from zero through the AC power supply; When the oil-soaked cardboard produces partial discharge signals for the first time, increase the preset DC voltage value and AC voltage value, and increase the preset DC voltage and AC voltage every time, within the preset sampling time Collect the partial discharge signal of the tested sample. 9. The method according to claim 8, characterized in that, the method also includes obtaining the phase resolution of the oil-impregnated paperboard under test according to the partial discharge of the oil-impregnated paperboard measured at different voltage values and different development stages. Partial discharge PRPD spectrum. 10. The method according to claim 8, wherein the AC power source is a high voltage harmonic power source. 11. The method according to claim 8, characterized in that the partial discharge characteristics of the oil-impregnated paperboard under different voltage forms are obtained by changing the ratio of the DC voltage to the AC voltage and the harmonic component of the AC voltage.