Partial discharge detection device for suspended water drops in insulating oil

Abstract

The utility model relates to the technical field of electric power, and discloses a partial discharge detection device for suspended water drops in insulating oil, which comprises a voltage regulator arranged on one side of a corona-free transformer, one end of the other side of the corona-free transformer is connected with a protective resistor, the other end of the corona-free transformer is connected with the ground, and a combined capacitor and a discharge defect model are connected in parallel between the protective resistor and the ground; the combined capacitor comprises a second capacitor and a first capacitor which are sequentially connected in series, and voltmeters are arranged at two ends of the first capacitor; the high-potential electrode end of the discharge defect model is sleeved with a spherical shielding cover. The discharge defect model is also connected in parallel with a standard pulse generator and a detection reactor, and the grounding end of the detection reactor is connected with the digital partial discharge detection system. The spherical shielding cover is arranged at the top of the positive plate in the discharge defect model, so that point discharge at the high-potential top of the defect model caused by overhigh boosting of the voltage regulator is effectively prevented, and the discharge defect model is particularly suitable for detecting discharge characteristic rules in insulating oil under the sealing defect of main equipment in a high-altitude area.

Description

Technical Field

[0001] The utility model relates to the technical field of electric power, in particular to a partial discharge detection device for suspended water droplets in insulating oil. Background Art

[0002] As the main power transmission and transformation equipment, oil-immersed transformers are mainly used for voltage regulation and transformation. In the power grid, power transmission usually requires transformation between different voltage levels to meet the needs of different regions and equipment. By changing the voltage level, oil-immersed transformers can efficiently and safely transmit electrical energy from power plants to end-users.

[0003] In alpine and high-altitude areas such as Qinghai, the climate conditions are diverse, including alpine and plateau climates, as well as cold and dry climates. These climate conditions pose requirements for the insulation and heat dissipation of transformers. Especially, the large temperature difference between day and night leads to the accelerated aging of the insulation seals of main equipment such as transformers. At the same time, the solubility of suspended water droplets in the internal insulating oil will change with the temperature difference, resulting in the serious precipitation of micro-water into suspended water droplets. Under the action of high voltage, partial discharge occurs in the suspended water droplets in the insulating oil, further affecting the performance of the sealing products of the main power transmission and transformation equipment under special high-altitude environmental conditions and causing equipment damage.

[0004] In the existing literature "Ma Shouxiao. Research on the partial discharge characteristics and influencing factors of metal particles in insulating oil under flowing state [D]. Chongqing University, 2016.", while analyzing the typical oil duct structure of large power transformers, combined with the electric field distribution in the oil duct, a physical experimental model reflecting the typical oil duct structure was designed, and a mathematical simulation model of the flowing state of metal particles in insulating oil was constructed. Based on the theoretical analysis of the movement trajectory and distribution characteristics of metal particles in flowing oil, the PD characteristics, influencing factors and action mechanisms of metal particles in insulating oil under flowing state were studied.

[0005] The prior art also includes the detection by the pulse current method recommended by the IEC60270 standard. However, due to the deficiencies of existing equipment and detection and analysis methods, such as the excessive boost of the voltage regulator, which will cause tip discharge at the high potential top of the defect model and large inaccuracies in detection data, etc., these technical problems have not been fundamentally solved, and it is impossible to accurately detect the faults and analyze the characteristics of partial discharge of suspended water droplets in insulating oil. Summary of the Invention

[0006] In order to overcome or alleviate one or more of the above technical problems, the purpose of the utility model is to provide a partial discharge detection device for suspended water droplets in insulating oil, which is used for fault detection and characteristic analysis of partial discharge of suspended water droplets in the insulating oil of AC and DC main equipment in high-altitude areas.

[0007] The utility model provides the following technical solutions:

[0008] A partial discharge detection device for suspended water droplets in insulating oil, which includes a voltage regulator (1) arranged on one side of a corona-free transformer (2). One end of the other side of the corona-free transformer (2) is connected to a protective resistor (3), and the other end is connected to the ground (10). A combined capacitor and a discharge defect model (5) are connected in parallel between the protective resistor (3) and the ground (10); the combined capacitor includes a second capacitor (12) and a first capacitor (9) connected in series in sequence. A voltmeter (11) is arranged at both ends of the first capacitor (9); a spherical shielding cover (4) is sleeved outside the high-potential electrode end of the discharge defect model (5); a standard pulse generator (6) and a detection impedance (8) are also connected in parallel to the discharge defect model (5), and the ground end of the detection impedance (8) is connected to a digital partial discharge detection system (7).

[0009] According to some embodiments, the spherical shielding cover (4) is a conductive metal ball.

[0010] According to some embodiments, the discharge defect model (5) includes a housing, which is an octagonal prism-shaped sealed cavity. An oil inlet (501) and an oil outlet (507) are respectively arranged at the left and right ends of the housing. A circular upper electrode plate (504) and a corresponding lower electrode plate (508) are arranged inside the housing. The upper and lower electrode ends respectively pass through the upper and lower electrode plates and respectively pass out from the upper and lower surfaces of the housing. The upper electrode end is at a high potential, and the spherical shielding cover (4) is sleeved outside it; insulating baffles (503) are arranged on both sides of the top surface of the housing. A spring-type safety valve (502) is arranged on the top surface of the housing and outside one of the baffles (503). A detection tube is arranged on the right side of the other baffle (503). A threaded ball valve (506) and a shock-resistant pressure gauge (505) are arranged outside the detection tube. The threaded ball valve (506) is used to discharge the gas in the housing, and the shock-resistant pressure gauge (505) is used to display the pressure value in the housing.

[0011] According to some embodiments, both the upper and lower electrode plates are pure copper electrode plates that are parallel to each other, have smooth edges, and are in a disc shape.

[0012] According to some embodiments, the voltage regulator (1) is AC380V.

[0013] According to some embodiments, the detection impedance (8) is composed of an RC-type capacitor and a resistor connected in parallel.

[0014] According to some embodiments, the model of the digital partial discharge detection system (7) is 7GDJF-2007.

[0015] Compared with the prior art, the present utility model has the following beneficial effects:

[0016] The utility model is applicable to the detection of partial discharge of suspended water droplets in the insulating oil of AC and DC main equipment in high-altitude areas. A spherical shielding cover is arranged at the top of the positive electrode plate inside the discharge defect model of the detection device, effectively preventing tip discharge from occurring at the high-potential top of the defect model due to excessive boosting of the AC 380V voltage regulator.

[0017] The detection impedance is connected in parallel to the discharge defect model, so that a voltage drop Δu is generated when discharge occurs. The external voltage must provide an apparent discharge quantity q to accurately transmit the pulse signal into the digital partial discharge detection system, effectively preventing errors and omissions in the signal from resulting in inaccurate detection.

[0018] The utility model also provides an experimental process, method and data processing for detecting partial discharge of suspended water droplets in the insulating oil inside a transformer under flowing and large temperature difference conditions, further conducts research on the characteristic analysis and fault detection of the discharge of suspended water droplets, and supplements the research on the discharge mechanism in insulating oil containing suspended water droplets.

[0019] The inside of the discharge defect model is composed of pure copper electrode plates that are parallel to each other, have smooth edges and are in a disc shape, perfectly achieving the functions of insulation, cooling and arc extinction, and conforming to the internal structure of a transformer under the actual flowing state of the project. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of a partial discharge detection device for suspended water droplets in insulating oil provided by an embodiment of the utility model.

[0021] Figure 2 It is a schematic diagram of a discharge defect model provided by an embodiment of the utility model.

[0022] Figure 3 It is a flow chart of the experiment provided by an embodiment of the utility model.

[0023] Figure 4 It is a diagram of data processing for partial discharge of suspended water droplets in insulating oil provided by an embodiment of the utility model.

[0024] Figure 5 It is a diagram of data processing for partial discharge of other suspended water droplets in insulating oil provided by an embodiment of the utility model.

[0025] Figure 6 It is a data table of apparent discharge quantity obtained in the experiment provided by an embodiment of the utility model.

[0026] In the figure:

[0027] 1. Voltage regulator; 2. Corona-free transformer; 3. Protection resistor; 4. Spherical shielding cover; 5. Discharge defect model; 6. Standard pulse generator; 7. Digital partial discharge detection system; 8. Detection impedance; 9. First capacitor; 10. Grounding; 11. Voltmeter; 12. Second capacitor; 13. Coaxial cable; 501. Oil inlet; 502. Safety valve; 503. Baffle; 504. Upper plate; 505. Shock-resistant pressure gauge; Threaded ball valve 506; Oil outlet 507; Lower plate 508. Detailed implementation mode

[0028] The present invention will be described in detail below in conjunction with embodiments and drawings. However, it should be understood that the embodiments and drawings are only used for exemplary description of the present invention, and cannot constitute any limitation to the protection scope of the present invention. All reasonable transformations and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0029] The present invention will be further described below in conjunction with the drawings.

[0030] Embodiment 1

[0031] Refer to Figure 1 , this embodiment provides a local discharge detection device for suspended water droplets in insulating oil, which is used for transformer fault detection and characteristic analysis. The device includes a voltage regulator 1 with AC380V, a corona-free transformer 2, a protection resistor 3, a spherical shielding cover 4, a discharge defect model 5, a detection impedance 8, a combined capacitor, a grounding 10, a voltmeter 11, a standard pulse generator 6, a coaxial cable 13, and a digital partial discharge detection system 7. The combined capacitor includes a first capacitor 9 and a second capacitor 12 connected in series, and the applied voltage value is obtained through the voltage across the first capacitor 9 measured by the voltmeter 11. The detection impedance 8 is specifically composed of an RC-type capacitor and a resistor connected in parallel.

[0032] The specific structure of this test device is described as follows:

[0033] A voltage regulator 1 with AC380V is connected to the left side of the corona-free transformer 2, one end of the right side is connected to the protection resistor 3 and the other end is connected to the grounding 10. A combined capacitor and a discharge defect model 5 are respectively connected in parallel between the protection resistor 3 and the grounding 10. The combined capacitor includes a second capacitor 12 and a first capacitor 9 connected in series, and the voltage across the first capacitor 9 is measured by the voltmeter 11; the spherical shielding cover 4 is a stainless steel sphere (to prevent tip discharge at high potential points) and is connected to the discharge defect model 5. The two poles of the discharge defect model 5 are connected to the standard pulse generator 6, and a detection impedance 8 is connected in parallel with the discharge defect model 5, and its grounding end is connected to a digital partial discharge detection system 7.

[0034] The upper and lower electrodes of the discharge defect model 5 are parallel to each other, with smooth edges and a disc-shaped pure copper electrode plate. Specifically, as Figure 2 , the housing of the discharge defect model 5 is an octagonal prism acrylic sealed cavity. Regarding the appearance shape of the housing, if the housing is rectangular, when the oil inlet 504 and the oil outlet 507 are feeding oil and discharging oil during the operation state, eddy currents will be generated around the four edges of the rectangle, resulting in unstable movement of the suspended water droplets inside the discharge defect model 5 and affecting partial discharge, while the octagonal prism will avoid this influence. The left and right ends of the housing are respectively provided with an oil inlet 501 and an oil outlet 507. Inside it, there are a circular upper electrode plate 504 and a corresponding lower electrode plate 508. The cavity between the upper and lower electrode plates is a hollow cavity. The upper and lower electrode ends respectively pass through the upper and lower electrode plates and respectively penetrate out from the upper and lower surfaces of the housing. The upper electrode end is at a high potential, and a spherical shielding cover 4 is sleeved outside it; on the left and right sides of the top surface of the housing, there are acrylic baffles 503. On the top surface of the housing, on the left side of the left baffle 503, there is a spring-type safety valve 502, and on the right side of the right baffle 503, there is a detection tube. An onepiece screw ball valve 506 and a shock-resistant pressure gauge 505 are provided outside the detection tube. The screw ball valve 506 is used for exhausting the inside of the housing, and the shock-resistant pressure gauge 505 is used for displaying the pressure value inside the housing.

[0035] The insulating oil and the suspended water droplets reach the upper electrode plate 504 and the lower electrode plate 508 from the oil inlet 501. The top of the upper electrode plate 504 is connected to the spherical shielding cover 4. The suspended water droplets generate partial discharge between the upper and lower electrode plates. The generated apparent discharge quantity is detected by the detection impedance 8 connected in parallel with the discharge defect model 5, and then transmitted to the digital partial discharge detection system 7. Finally, the insulating oil and the suspended water droplets flow out from the oil outlet 507.

[0036] The upper part of the discharge defect model 5 is provided with an acrylic baffle 503 to prevent the spring-type safety valve 502, the onepiece screw ball valve 506, and the shock-resistant pressure gauge 505 on the upper part of the housing from carrying residual charges under high pressure, which may affect the test data and the safety of the test personnel.

[0037] Connected in parallel with the detection impedance 8 and the standard pulse generator 6; the detection impedance 8 generates a voltage drop Δu when the discharge defect model 5 discharges. The external voltage must provide an apparent discharge quantity q, which is detected by the detection impedance 8 and is connected to the digital partial discharge detection system 7 through the coaxial cable 13.

[0038] A spherical shielding cover 4 is arranged on the top of the positive electrode plate inside the discharge defect model 5, effectively preventing the AC380V voltage regulator 1 from boosting too high and causing tip discharge at the high-potential top of the discharge defect model 5;

[0039] The detection impedance 8 is connected in parallel to the discharge defect model 5, such that a voltage drop Δu is generated during discharge. The external voltage must provide an apparent discharge quantity q so that the pulse signal can be accurately transmitted into the digital partial discharge detection system 7, effectively preventing errors and omissions in the signal that may lead to inaccurate detection.

[0040] Inside the discharge defect model are parallel, smooth-edged, disc-shaped pure copper plates, which perfectly achieve the functions of insulation, cooling, and arc extinction, and conform to the internal structure of a transformer under actual engineering flow conditions.

[0041] The digital partial discharge detection system 7 uses the existing GDJF-2007 digital partial discharge detection system.

[0042] The partial discharge detection device for suspended water droplets in insulating oil provided in this embodiment has the following prominent features:

[0043] 1. Since the spherical shielding cover 4 shields the tip discharge at the high potential of the upper electrode end, a voltage drop Δu is generated inside the discharge defect model during discharge. The external voltage must provide an apparent discharge quantity q, which is accurately detected by the detection impedance, so the data detection is more accurate.

[0044] 2. An acrylic baffle is provided above the discharge defect model to prevent the spring safety valve 502, one-piece threaded ball valve 506, and shock-resistant pressure gauge 505 above the defect model from carrying residual charges under high voltage, which may affect the test data and the safety of the test personnel.

[0045] Such as Figure 3 , the test method of this test device includes the following steps:

[0046] S1: First, perform the airtightness detection of the discharge defect model 5;

[0047] S2: Ground the metal devices of the spring safety valve 502, one-piece threaded ball valve 506, and shock-resistant pressure gauge 505 in the discharge defect model 5, except for the high potential.

[0048] S3: Then place the standard pulse generator 6 between the positive and negative plates of the discharge defect model 5 and perform partial discharge pulse calibration (50 pC) with the digital partial discharge detection system 7;

[0049] S4: Start the test, and use a corrosion-resistant and high-temperature-resistant magnetic pump and a high-power stainless steel electric heating rod to control the flow rate of the oil and suspended water droplets in the transformer and the temperature of the oil, and boost the voltage at different flow rates and temperatures;

[0050] S5: Observe the movement law of the suspended water droplets and detect the partial discharge situation inside the discharge defect model 5 in one cycle. Measure the high-voltage terminal voltage of the first capacitor 9 through the voltmeter 11, and sample and save the apparent discharge quantity data in the digital partial discharge detection system 7;

[0051] S6: Sample multiple times, that is, execute S3 - S5 in a loop according to a certain number of times to obtain multiple sets of apparent discharge quantity data;

[0052] S7: Extract the apparent discharge quantity data and convert it into an Excel table;

[0053] S8: Perform preprocessing on the apparent discharge quantity data for the median value and maximum value to obtain waveform apparent discharge quantity data;

[0054] S9: Import the preprocessed apparent discharge quantity data into data analysis software such as Matlab software, and use built - in functions such as signal entropy, skewness, kurtosis, peak - to - peak value, standard deviation, root mean square value, and correlation coefficient to further analyze the characteristics of the data, and finally find the partial discharge pattern.

[0055] The apparent discharge quantity data in step S9 is imported into Matlab, and using built - in functions such as signal entropy, skewness, kurtosis, peak - to - peak value, standard deviation, root mean square value, and correlation coefficient, the discharge pattern of phase - discharge quantity under different flow rates and temperatures is further analyzed in one cycle, getting rid of the traditional method of only looking at the two - dimensional pattern of phase - discharge quantity to analyze discharge characteristics.

[0056] The characteristic analysis includes the analysis of characteristics such as signal entropy, skewness, kurtosis, peak - to - peak value, standard deviation, root mean square value, and correlation coefficient under test parameters such as the flow rate, temperature, and pressure of the oil and suspended water droplets in different transformers.

[0057] Through this test method, the characteristics and patterns of partial discharge of transformer oil containing suspended water droplets can be analyzed to supplement the discharge theory in transformer oil containing suspended water droplets.

[0058] Example 2

[0059] In this example, through the test device provided in Example 1, the characteristics and pattern test of partial discharge of transformer oil containing suspended water droplets is carried out, and the test steps are as follows:

[0060] First, conduct the airtightness detection of the overall test equipment; ground the metal devices of the spring - type safety valve 502, one - piece threaded ball valve 506, and shock - proof pressure gauge 505 in the discharge defect model 5;

[0061] Then place the standard pulse generator 6 between the positive and negative plates of the discharge defect model 5 and calibrate the partial discharge pulse (50 pC) with the digital partial discharge detection system 7;

[0062] Start the test, boost the pressure at different flow rates and temperatures; observe the movement law of suspended water droplets and detect the partial discharge situation inside the defect model 5 in one cycle. Measure the high-voltage terminal voltage through a combined capacitor, and save the apparent discharge quantity data after sampling in the digital partial discharge detection system 7; sample multiple times to obtain multiple groups of apparent discharge quantity data;

[0063] After extraction, convert it into an Excel table, as Figure 6 shown. The data in the first vertical column of the table are 360 phases in one cycle, and the subsequent vertical columns are the discharge quantities corresponding to 360 phases in one cycle; the unit of the discharge quantity is pC; the first horizontal row is different voltage values, with the unit kV, showing the apparent discharge quantities at different voltages in one cycle; preprocess the apparent discharge quantity data for the median and maximum values; import the apparent discharge quantity data into Matlab, and use the built-in functions of signal entropy, skewness, kurtosis, peak-to-peak value, standard deviation, root mean square value, and correlation coefficient to further analyze the characteristics of the data, and finally find the partial discharge law.

[0064] 2. At a temperature of 50°, an AC voltage of 31.1 kV, and a noise of 1.6 pC, explore the partial discharge characteristics of the positive and negative half-cycles at different flow rates. The test charts are as Figure 4 and Figure 5 shown. According to Figure 4 and Figure 5 the following test results and discharge laws are obtained as follows:

[0065] Test results: The signal entropy represents the complexity of the overall data, similar to the trend of the standard deviation. Both are not obvious in the positive and negative half-cycles at low flow rates. The greater the flow rate, the more complex the partial discharge in the positive half-cycle. However, generally speaking, the lower the flow rate, the more complex the partial discharge; starting from the skewness and kurtosis, the overall curve deviates to the left of 90° and 270°. The greater the flow rate, the greater the stretching degree of the tail, and there are more discrete values, indicating that the data is more unstable; the peak-to-peak value (maximum value) and the root mean square value (overall) both represent the volatility and discreteness of the signal. It can be seen from the low flow rate that the volatility of the positive half-cycle is much smaller than that of the negative half-axis. As the flow rate increases, the discreteness of the positive half-cycle dominates, indicating that as the flow rate increases, the partial discharge in the positive half-cycle gradually becomes unstable; the standard deviation represents the degree of discreteness. At low flow rates, the difference between the positive and negative half-cycles is not large, and the discharge is relatively stable. However, as the flow rate increases, the partial discharge in the positive half-cycle is significantly more serious; the closer the correlation coefficient is to 1, the more linearly correlated the positive and negative half-cycles are. At low flow rates, the partial discharge distribution of the positive and negative half-cycles is more symmetric than at high flow rates, indicating that at low flow rates, the discreteness of the partial discharge of the positive and negative half-cycles is low.

[0066] Discharge law: When the flow rate is small, the difference in partial discharge between the positive and negative half-cycles is not obvious, the discharge is relatively stable, the discreteness is low, but the partial discharge is more serious than when the flow rate is large; the larger the flow rate, the more complex the partial discharge in the positive half-cycle compared to the negative half-cycle, the discreteness in the positive half-cycle dominates, and there are more discrete values in the discharge amount, and the discharge is more unstable.

[0067] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A device for detecting partial discharge of suspended water droplets in insulating oil, comprising a voltage regulator (1) arranged on one side of a corona-free transformer (2), one end of the other side of the corona-free transformer (2) being connected to a protective resistor (3) and the other end being connected to a ground (10), characterized in that: A combined capacitor and a discharge defect model (5) are connected in parallel between the protection resistor (3) and the ground (10); the combined capacitor comprises a second capacitor (12) and a first capacitor (9) connected in series in sequence, and a voltmeter (11) is provided at both ends of the first capacitor (9); a spherical shielding cover (4) is provided on the high potential electrode end of the discharge defect model (5); the discharge defect model (5) is also connected in parallel with a standard pulse generator (6) and a detection group impedance (8), and the ground end of the detection group impedance (8) is connected to a digital partial discharge detection system (7).

2. The device for detecting partial discharge of suspended water droplets in insulating oil according to claim 1, characterized in that: The spherical shielding cover (4) is a conductive metal ball.

3. The device for detecting partial discharge of suspended water droplets in insulating oil according to claim 2, characterized in that: The discharge defect model (5) comprises a shell, which is an octagonal sealed cavity, wherein the left and right ends of the shell are respectively provided with an oil inlet (501) and an oil outlet (507), wherein a circular upper electrode plate (504) and a corresponding lower electrode plate (508) are arranged inside the shell, wherein the upper and lower electrode ends respectively pass through the upper and lower electrode plates and respectively pass out from the upper and lower surfaces inside the shell, wherein the upper electrode end is of high potential and the outer cover thereof is provided with the spherical shielding cover (4); baffles (503) for insulation are arranged on the left and right sides of the top surface of the shell, a spring-type safety valve (502) is arranged on the top surface of the shell and located outside the baffle (503) on one side, and a detection tube is arranged on the right side of the baffle (503) on the other side, wherein a threaded ball valve (506) and a shockproof pressure gauge (505) are arranged outwardly of the detection tube, wherein the threaded ball valve (506) is used to discharge the gas in the shell, and the shockproof pressure gauge (505) is used to display the pressure value in the shell.

4. The device for detecting partial discharge of suspended water droplets in insulating oil according to claim 3, characterized in that: The upper and lower pole plates are both parallel to each other, have smooth edges, and are pancake-shaped pure copper pole plates.

5. The device for detecting partial discharge of suspended water droplets in insulating oil according to claim 1, characterized in that: The voltage regulator (1) is AC380V.

6. The device for detecting partial discharge of suspended water droplets in insulating oil according to claim 1, characterized in that: The detection impedance (8) is formed by connecting an RC type capacitor and a resistor in parallel.

7. The device for detecting partial discharge of suspended water droplets in insulating oil according to any one of claims 1 to 6, characterized in that: The model of the digital partial discharge detection system (7) is 7GDJF-2007.

Images