Transformer oil-submerged pump high-frequency partial discharge monitoring device and method

Abstract

The invention provides a transformer oil-submerged pump high-frequency partial discharge monitoring device and method, and belongs to the technical field of transformer oil-submerged pump high-frequency partial discharge monitoring. In order to solve the technical problems of low efficiency and low accuracy of manual monitoring of the state of an oil-submerged pump in operation at present, a transformer body is connected with the oil-submerged pump through an oil-submerged pump oil outlet pipeline, and the oil-submerged pump is connected with cooling fins through the oil-submerged pump oil outlet pipeline; a first high-frequency current sensor is arranged on the outer side of the oil outlet pipeline of the oil-submerged pump, and a second high-frequency current sensor is arranged on the outer side of the oil outlet pipeline of the oil-submerged pump; an oil-submerged pump junction box is arranged on one side of the oil-submerged pump, an oil-submerged pump power supply winding is installed in the oil-submerged pump junction box, a voltage sensor and a third high-frequency current sensor are arranged on the oil-submerged pump power supply winding, and a fourth high-frequency current sensor is arranged on an oil-submerged pump ground wire; the signal processing unit is connected with the high-frequency current sensors through wires. The method is used for monitoring the high-frequency partial discharge state of the transformer oil-submerged pump.

Description

Technical Field

[0001] This invention provides a high-frequency partial discharge monitoring device and method for transformer submersible oil pumps, belonging to the technical field of high-frequency partial discharge monitoring for transformer submersible oil pumps. Background Technology

[0002] Large-capacity transformers typically use a strong oil circulation method for heat dissipation, and the submersible oil pump is an important cooling component for this strong oil circulation, providing the power source for the oil circulation. However, due to the lack of effective live detection methods, traditional vibration signal measurement methods are greatly affected by environmental interference, especially the vibration interference generated by the fan. Currently, the lack of or infrequent daily inspections of the submersible oil pump's operating status leads to frequent failures.

[0003] In actual operation, the transformer may experience inter-turn short-circuit discharge due to the power supply winding of the submersible pump. The characteristic gas generated may eventually lead to abnormal chromatograms of the transformer body due to long-term circulation of the oil circuit. The submersible pump impeller of the converter transformer may also rub against the casing, and the generated metal particles may cause local suspended discharge. Tests have shown that when partial discharge occurs, it is accompanied by high-frequency pulse current signals, ultrasonic signals, and ultra-high frequency electromagnetic signals. Conventional methods for monitoring partial discharge include high-frequency partial discharge monitoring, ultrasonic partial discharge monitoring, and ultra-high frequency partial discharge monitoring. Among them, ultra-high frequency electromagnetic signals are not suitable for monitoring submersible pumps in operation because the sensors usually need to be built into the pipeline due to the electromagnetic shielding of the pipeline metal. Ultrasonic signals are vibration signals and are easily affected by environmental interference, especially the vibration interference of fans near the submersible pump and the transformer body itself. High-frequency signals are electrical signals and can more accurately and directly reflect the internal discharge of the transformer than ultrasonic signals. Moreover, high-frequency signals are more stable.

[0004] Regarding the technology for monitoring the operating status of submersible oil pumps in substations, there is currently a remote fault monitoring scheme for oil pumps of traction transformers in EMU trains, which is disclosed in patent announcement number CN105804981B. This scheme monitors the offset of the stator and rotor in the X, Y, and Z directions by adding eight induction coils in the oil pump windings. However, this method requires adding coils to the submersible oil pump to change the original electromagnetic performance of the motor, and it cannot be applied to the monitoring of submersible oil pumps that are already in operation, so its universality is not strong.

[0005] Another patent, CN112065705A, discloses a fault monitoring scheme for a forced oil circulation transformer submersible pump. By adding an oil sampling port near the submersible pump, the content of characteristic gases in the oil sample from the submersible pump and the oil sample from the transformer body are compared, thereby realizing the fault identification of the submersible pump. However, this method requires modification of the original pipeline, which consumes a lot of manpower. Moreover, due to the proximity to the submersible pump and the high oil pressure, it is difficult to take oil samples from the vicinity of the submersible pump, making it impractical.

[0006] Currently, there is a lack of effective detection methods for submersible pump failures. Traditional detection methods mainly rely on manual inspections. The detection items include: (1) measuring whether the amplitude of vibration signals is abnormal, but this is greatly affected by environmental interference, especially the vibration interference generated by the fan, which is difficult to eliminate; (2) whether the three-phase current imbalance exceeds the standard, but this is affected by spatial leakage magnetic field interference, making it difficult to detect effective signals in advance, and it is easy to miss the detection; (3) body oil chromatography detection, but it takes a certain amount of time for the chromatographic abnormality of the submersible pump failure to spread to the body chromatographic abnormality, which has a lag and can easily lead to further development of the failure. Since the early partial discharge and inter-turn short circuit fault characteristic signals of the submersible pump are weak and intermittent, and are affected by environmental interference, it is difficult to detect them in time using the above-mentioned conventional manual detection methods. It is urgent to develop an effective condition monitoring scheme for submersible pumps in operation. Summary of the Invention

[0007] To address the technical problems existing in the background art, the present invention adopts the following technical solution: providing a transformer submersible oil pump high-frequency partial discharge monitoring device, including a transformer body, a submersible oil pump, a heat sink, and a signal processing unit. The transformer body is connected to the submersible oil pump through the oil outlet pipe of the submersible oil pump. The submersible oil pump is connected to the lower part of the heat sink through the oil inlet pipe of the submersible oil pump. The upper part of the heat sink is connected to the transformer body through a pipe for strong oil circulation heat dissipation.

[0008] A first high-frequency current sensor is installed on the outside of the oil outlet pipeline of the submersible pump, and a second high-frequency current sensor is installed on the outside of the oil inlet pipeline of the submersible pump. The first high-frequency current sensor and the second high-frequency current sensor are used to monitor the high-frequency pulse current on the corresponding pipelines.

[0009] A submersible pump junction box is provided on one side of the submersible pump. The submersible pump power supply winding and the submersible pump ground wire are installed inside the submersible pump junction box. A voltage sensor and a third high-frequency current sensor are provided on the submersible pump power supply winding. A fourth high-frequency current sensor is provided on the submersible pump ground wire. The voltage sensor is used to monitor the phase of the power frequency voltage on the submersible pump power supply winding. The third high-frequency current sensor is used to monitor the high-frequency current on the submersible pump power supply winding. The fourth high-frequency current sensor is used to monitor the high-frequency current on the submersible pump ground wire.

[0010] The signal processing unit is connected to the first high-frequency current sensor, the second high-frequency current sensor, the third high-frequency current sensor, and the fourth high-frequency current sensor via wires. The signal processing unit is used to filter out low-frequency current signals that cause interference in the monitoring data and retain high-frequency current signals.

[0011] The signal output terminal of the signal processing unit is connected to the microcontroller chip via a wire. The microcontroller chip is also connected to the voltage sensor via a wire. The microcontroller chip is used to store monitoring data and evaluate the status of the submersible pump.

[0012] A monitoring method for a high-frequency partial discharge monitoring device for a transformer submersible oil pump includes the following monitoring steps:

[0013] Step 1: Monitor the high-frequency current in the pipeline:

[0014] When the submersible pump is running normally, the first high-frequency current sensor and the second high-frequency current sensor monitor the high-frequency current data of the submersible pump's inlet and outlet oil pipelines respectively. The monitoring data is sent to the signal processing unit for processing to obtain the high-frequency current component. The processed signal is then sent to the microcontroller chip to calculate the difference between the two to obtain the high-frequency current partial discharge signal in the pipeline generated by the submersible pump.

[0015] Step 2: Monitor the high-frequency current of the power supply winding:

[0016] During normal operation of the submersible pump, the third high-frequency current sensor is controlled to monitor the high-frequency current of the power supply winding in the submersible pump power supply winding, and the monitoring data is sent to the signal processing unit for processing to obtain the high-frequency current partial discharge signal in the power supply winding of the submersible pump generated by the submersible pump.

[0017] Step 3: Monitor the high-frequency current of the submersible pump ground wire:

[0018] During normal operation of the submersible pump, the fourth high-frequency current sensor is controlled to monitor the high-frequency current of the submersible pump ground wire and the monitoring data is sent to the signal processing unit for processing to obtain the high-frequency current partial discharge signal in the submersible pump ground wire generated by the submersible pump.

[0019] Step 4: Assess the partial discharge status of the submersible pump:

[0020] Based on the high-frequency current partial discharge signals obtained in steps 1, 2, and 3, and combined with the winding voltage power frequency reference phase monitored by the voltage sensor, the microcontroller chip statistically analyzes the maximum amplitude z of all high-frequency partial discharge signals within a 10-second period, the relative standard deviation p of the phase of all high-frequency partial discharge signals in the 0°-180° range, and the relative standard deviation q of the phase of all high-frequency partial discharge signals in the 180°-360° range, and then calculates:

[0021] The formula for calculating the high-frequency partial discharge factor c of the pipeline is:

[0022] (1);

[0023] The formula for calculating the high-frequency partial discharge factor d of the power supply winding is:

[0024] (2);

[0025] The high-frequency partial discharge factor f of the ground wire is calculated using the following formula:

[0026] (3);

[0027] The partial discharge assessment coefficient v for submersible pumps is calculated using the following formula:

[0028] (4);

[0029] Finally, the current operating status of the submersible pump is evaluated and calculated using the following formula:

[0030] (5).

[0031] The beneficial effects of this invention compared to the prior art are as follows: This invention provides a high-frequency partial discharge monitoring device and method for transformer submersible oil pumps. By monitoring the high-frequency partial discharge pulse current signals of the oil pump inlet and outlet pipelines, power supply windings, and ground wire, and evaluating them from two dimensions—the amplitude of the high-frequency signal within the cycle and the degree of phase dispersion—it can realize real-time perception of typical faults such as partial discharge and inter-turn short circuits inside the submersible oil pump, filling the technical gap in the effective monitoring of submersible oil pumps. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings:

[0033] Figure 1 This is a schematic diagram of the high-frequency partial discharge monitoring device for transformer submersible oil pumps according to the present invention;

[0034] Figure 2 This is a flowchart of the steps in the high-frequency partial discharge monitoring method for transformer submersible oil pumps of the present invention.

[0035] The meanings of the numbers in the diagram are as follows:

[0036] 1 is the transformer body, 2 is the submersible pump, 3 is the heat sink, 4 is the submersible pump outlet pipe, 5 is the submersible pump inlet pipe, 6 is the voltage sensor, 7 is the first high-frequency current sensor, 8 is the second high-frequency current sensor, 9 is the third high-frequency current sensor, 10 is the signal processing unit, 11 is the microcontroller chip, 12 is the submersible pump junction box, 13 is the submersible pump power supply winding, 14 is the submersible pump ground wire, and 15 is the fourth high-frequency current sensor. Detailed Implementation

[0037] like Figure 1 As shown, this invention provides a high-frequency partial discharge monitoring device for a transformer submersible oil pump, comprising: a transformer body 1, a submersible oil pump 2, a heat sink 3, a submersible oil pump outlet pipe 4, a submersible oil pump inlet pipe 5, a voltage sensor 6, a first high-frequency current sensor 7, a second high-frequency current sensor 8, a third high-frequency current sensor 9, a signal processing unit 10, a microcontroller chip 11, a submersible oil pump junction box 12, a submersible oil pump power supply winding 13, a submersible oil pump ground wire 14, and a fourth high-frequency current sensor 15, wherein:

[0038] The transformer body 1 is connected to the submersible pump 2 through the submersible pump outlet pipe 4. The submersible pump 2 is connected to the lower part of the heat sink 3 through the submersible pump inlet pipe 5. The upper part of the heat sink 3 is connected to the transformer body 1 through a pipe, thereby realizing the transformer's strong oil circulation heat dissipation.

[0039] The first high-frequency current sensor 7 is installed on the outside of the oil outlet pipe 4 of the submersible pump, and the second high-frequency current sensor 8 is installed on the outside of the oil inlet pipe 5 of the submersible pump. They are used to monitor the high-frequency pulse current on the pipe. The third high-frequency current sensor 9 and the fourth high-frequency current sensor 15 are respectively installed on the submersible pump power supply winding 13 and the submersible pump ground wire 14 inside the submersible pump junction box 12. They are used to monitor the high-frequency current on the power supply winding. Since the submersible pump junction box 12 is usually a sealed metal box, it can shield external electromagnetic interference.

[0040] The signal processing unit 10 is connected to the first high-frequency current sensor 7, the second high-frequency current sensor 8, the third high-frequency current sensor 9, and the fourth high-frequency current sensor 15 to filter out low-frequency current interference and retain high-frequency current signals of 3MHz-30MHz.

[0041] Voltage sensor 6 is installed on the submersible pump power supply winding 13 inside the submersible pump junction box 12 to monitor the winding voltage phase and provide a power frequency reference phase. That is, when a high-frequency pulse signal appears, the winding voltage phase corresponding to it is the high-frequency partial discharge signal phase.

[0042] The microcontroller chip 11 is connected to the signal processing unit 10 and the voltage sensor 6 respectively, and is used to store monitoring data and evaluate the status of the submersible pump 2.

[0043] like Figure 2 As shown, based on the above-mentioned monitoring device, the present invention also provides a method for monitoring high-frequency partial discharge of a transformer submersible oil pump, comprising the following monitoring steps:

[0044] Step 1: High-frequency current monitoring of pipelines:

[0045] When the submersible pump is running normally, the first high-frequency current sensor 7 and the second high-frequency current sensor 8 monitor the high-frequency current in the inlet and outlet oil pipelines of the submersible pump, respectively. After passing through the signal processing unit, the high-frequency current component is obtained. The microcontroller chip 11 calculates the difference between the two to obtain the high-frequency current partial discharge signal in the pipeline generated by the submersible pump 2.

[0046] Step 2: High-frequency current monitoring of the power supply winding:

[0047] The third high-frequency current sensor 9 monitors the high-frequency current of the power supply winding. After passing through the signal processing unit 10, it obtains the high-frequency current partial discharge signal in the power supply winding generated by the submersible pump 2.

[0048] Step 3: High-frequency current monitoring of the ground wire:

[0049] The fourth high-frequency current sensor 15 monitors the high-frequency current of the ground wire, and after passing through the signal processing unit 10, it obtains the high-frequency current partial discharge signal in the ground wire winding generated by the submersible pump 2.

[0050] Step 4: Submersible pump partial discharge assessment:

[0051] Combining the winding voltage power frequency reference phase monitored by voltage sensor 6, with a period of 10 seconds, the microcontroller chip 11 statistically analyzes the maximum amplitude z of all high-frequency partial discharge signals within the period, the relative standard deviation p of the phase of all high-frequency partial discharge signals in the 0°-180° range, and the relative standard deviation q of the phase of all high-frequency partial discharge signals in the 180°-360° range. Based on formulas (1), (2), and (3), the high-frequency partial discharge coefficient c of the pipeline, the high-frequency partial discharge coefficient d of the power supply winding, and the high-frequency partial discharge coefficient f of the ground wire are calculated respectively.

[0052] (1);

[0053] (2);

[0054] (3);

[0055] Then, the partial discharge assessment coefficient v of the submersible pump is calculated according to formula (4):

[0056] (4);

[0057] Finally, the current operating status of the submersible pump is calculated using formula (5):

[0058] (5).

[0059] The relative deviation is calculated as shown in formula (6):

[0060] (6);

[0061] in: This represents the average phase value of the high-frequency partial discharge signal within the phase range of 0°-180° or 180°-360° over 10 seconds. Let n be the phase of a certain high-frequency partial discharge signal, and n be the number of high-frequency partial discharge signals in the phase interval of 0°-180° or 180°-360° within 10 seconds.

[0062] According to the enterprise standard Q / GDW11400-2015 Field Application Guidelines for High-Frequency Partial Discharge Live Detection Technology of Power Equipment, when partial discharge occurs in power equipment, a pulse current with a frequency of 3MHz-30MHz is usually generated on its grounding down conductor or other ground potential connection line. The high-frequency pulse signal flowing through the grounding down conductor or other ground potential connection line is detected by a high-frequency current sensor to realize the live detection of partial discharge in power equipment.

[0063] Therefore, when partial discharge exists inside the transformer submersible pump, the generated high-frequency pulse current propagates through three paths: one is through the submersible pump's metal pipes, the second is through the submersible pump's power supply winding, and the third is through the ground wire connected to the submersible pump's metal pipe casing. This invention monitors the difference in high-frequency pulse current signals between the submersible pump's inlet and outlet pipes, eliminates high-frequency current signals propagated from the heat sink or the pump body, and obtains high-frequency current signals generated only inside the submersible pump. At the same time, by monitoring the high-frequency current signals of the power supply winding and the ground wire inside the metal box, it obtains high-frequency current signals propagating through the power supply winding and the ground wire, thereby realizing high-frequency partial discharge monitoring of the transformer submersible pump.

[0064] According to the enterprise standard Q / GDW11400-2015, "Guidelines for Field Application of High-Frequency Partial Discharge Detection Technology for Power Equipment", the typical high-frequency partial discharge spectrum characteristics are shown in Table 1 below.

[0065] Table 1. Typical High-Frequency Partial Discharge Spectrum Characteristics

[0066]

[0067] The phase distribution characteristics of the power frequency (half power frequency) spectrum indicate that the reference phase value of the high-frequency current pulse signal is concentrated in the power frequency (half power frequency) range, rather than being uniformly distributed. Therefore, this invention monitors and evaluates the operating status of the submersible pump through two dimensions: the maximum amplitude of the high-frequency partial discharge signal and the relative standard deviation of the phase, i.e., the degree of dispersion.

[0068] Furthermore, according to the enterprise standard Q / GDW11304.5-2015 Technical Specifications for Live-Line Testing Instruments for Power Equipment and Technical Specifications for Live-Line Testing Instruments for Partial Discharge Using High Frequency Method, the performance of the high-frequency current sensor must meet the parameters in Table 2 below.

[0069] Table 2 Parameter Requirements for High-Frequency Partial Discharge Sensors

[0070]

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-frequency partial discharge monitoring device for a transformer submersible oil pump, comprising a transformer body (1), a submersible oil pump (2), a heat sink (3), and a signal processing unit (10), characterized in that: The transformer body (1) is connected to the submersible pump (2) through the oil outlet pipe (4), the submersible pump (2) is connected to the lower part of the heat sink (3) through the oil inlet pipe (5), and the upper part of the heat sink (3) is connected to the transformer body (1) through a pipe to perform strong oil circulation heat dissipation. A first high-frequency current sensor (7) is installed on the outside of the oil outlet pipeline (4) of the submersible pump, and a second high-frequency current sensor (8) is installed on the outside of the oil inlet pipeline (5) of the submersible pump. The first high-frequency current sensor (7) and the second high-frequency current sensor (8) are used to monitor the high-frequency pulse current on the corresponding pipelines. A submersible pump junction box (12) is provided on one side of the submersible pump (2). A submersible pump power supply winding (13) and a submersible pump ground wire (14) are installed inside the submersible pump junction box (12). A voltage sensor (6) and a third high-frequency current sensor (9) are provided on the submersible pump power supply winding (13). A fourth high-frequency current sensor (15) is provided on the submersible pump ground wire (14). The voltage sensor (6) is used to monitor the phase of the power frequency voltage on the submersible pump power supply winding (13). The third high-frequency current sensor (9) is used to monitor the high-frequency current on the submersible pump power supply winding (13). The fourth high-frequency current sensor (15) is used to monitor the high-frequency current on the submersible pump ground wire (14). The signal processing unit (10) is connected to the first high-frequency current sensor (7), the second high-frequency current sensor (8), the third high-frequency current sensor (9), and the fourth high-frequency current sensor (15) respectively via wires. The signal processing unit (10) is used to filter out low-frequency current signals that interfere with the monitoring data and retain high-frequency current signals. The signal output terminal of the signal processing unit (10) is connected to the microcontroller chip (11) via a wire. The microcontroller chip (11) is also connected to the voltage sensor (6) via a wire. The microcontroller chip (11) is used to store monitoring data and evaluate the status of the submersible pump.

2. The monitoring method of the high-frequency partial discharge monitoring device for a transformer submersible oil pump according to claim 1, characterized in that: The monitoring steps include the following: Step 1: Monitor the high-frequency current in the pipeline: When the submersible pump is running normally, the first high-frequency current sensor (7) and the second high-frequency current sensor (8) are controlled to monitor the high-frequency current data of the submersible pump inlet and outlet oil pipelines respectively. The monitoring data is sent to the signal processing unit (10) for processing to obtain the high-frequency current component. The processed signal is then sent to the microcontroller chip (11) to calculate the difference between the two and obtain the high-frequency current partial discharge signal in the pipeline generated by the submersible pump (2). Step 2: Monitor the high-frequency current of the power supply winding: When the submersible pump is running normally, the third high-frequency current sensor (9) is controlled to monitor the high-frequency current of the power supply winding (13) of the submersible pump, and the monitoring data is sent to the signal processing unit (10) for processing to obtain the high-frequency current partial discharge signal of the power supply winding (13) of the submersible pump generated by the submersible pump (2). Step 3: Monitor the high-frequency current of the submersible pump ground wire (14): When the submersible pump (2) is running normally, the fourth high-frequency current sensor (15) is controlled to monitor the high-frequency current of the submersible pump ground wire (14), and the monitoring data is sent to the signal processing unit (10) for processing to obtain the high-frequency current partial discharge signal in the submersible pump ground wire (14) generated by the submersible pump (2). Step 4: Assess the partial discharge status of the submersible pump: Based on the high-frequency current partial discharge signals obtained in steps 1, 2, and 3, and combined with the winding voltage power frequency reference phase monitored by the voltage sensor (6), the microcontroller chip (11) statistically analyzes the maximum amplitude z of all high-frequency partial discharge signals within a 10-second period, the relative standard deviation p of the phase of all high-frequency partial discharge signals in the 0°-180° range, and the relative standard deviation q of the phase of all high-frequency partial discharge signals in the 180°-360° range, and then calculates: The formula for calculating the high-frequency partial discharge factor c of the pipeline is: （1）； The formula for calculating the high-frequency partial discharge factor d of the power supply winding is: （2）； The high-frequency partial discharge factor f of the ground wire is calculated using the following formula: （3）； The partial discharge assessment coefficient v for submersible pumps is calculated using the following formula: （4）； Finally, the current operating status of the submersible pump is evaluated and calculated using the following formula: （5）。

Images