A method and system for detecting partial discharge of 10kV power distribution cable oscillating wave

Abstract

The embodiment of the application provides a kind of 10kV distribution cable oscillation wave partial discharge detection method and system, applied to cable detection technical field.The method is applied to detection system, obtains the control instruction carrying preset test voltage and detection mode, and detection mode is any one in single-phase detection, two-phase detection and three-phase detection;Response control instruction, determine the connection state of the high voltage relay corresponding to the detection mode, drive three-phase partial discharge detection unit to generate the detection data of the 10kV distribution cable to be tested based on the preset test voltage and the connection state of the high voltage relay;Filter the detection data collected by sampling module by computer, obtain partial discharge data and voltage signal;Determine the detection result based on partial discharge data and voltage signal.Can be independently selected according to test requirement detection mode, based on detection mode to mobilize the composition structure of detection system to realize detection, simplify cable detection process, and can detect cable three-phase simultaneously, improve cable detection efficiency.

Description

Technical Field

[0001] This application relates to the field of cable testing technology, specifically to a method and system for detecting partial discharge of oscillating waves in 10kV distribution cables. Background Technology

[0002] 10kV distribution cables are widely used, and ensuring their stable operation is of great significance to urban and industrial power distribution networks. Partial discharge detection technology is generally used to test the insulation of 10kV distribution cables.

[0003] Currently, the commonly used partial discharge detection technology for on-site inspection of 10kV distribution cables is the oscillating wave detection technology, which can effectively detect and locate partial discharge defects in 10kV distribution cables.

[0004] According to the testing procedures, conducting oscillating wave testing requires separate testing of the three phases of a 10kV distribution cable. First, one phase is tested, while the conductors and shielding of the other two non-tested phases are grounded. After testing that phase, the next phase is tested using the same method. During phase switching, the grounding at the cable end also needs to be replaced, making the entire process time-consuming, labor-intensive, and cumbersome. Furthermore, if partial discharge testing of all three phases is conducted simultaneously, directly connecting the high-voltage oscillating wave output to the three phases of the cable results in a highly complex transmission process of the partial discharge signal in the parallel cable, making defect location difficult. Therefore, the existing methods for testing 10kV distribution cables suffer from low testing efficiency. Summary of the Invention

[0005] In view of this, this application provides a method and system for detecting partial discharge of oscillating waves in 10kV distribution cables, which can simplify the detection process of 10kV distribution cables, meet the requirement of simultaneous detection of three phases of the cable, and improve the detection efficiency of 10kV distribution cables.

[0006] To solve the above problems, the technical solution provided in this application is as follows:

[0007] In a first aspect, embodiments of this application provide a method for detecting partial discharge of oscillating waves in a 10kV distribution cable. The detection method is applied to a detection system for partial discharge of oscillating waves in a 10kV distribution cable. The detection system includes a DC high-voltage module, an adjustable charging resistor module, a high-voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer. The three-phase partial discharge detection unit is connected to the three-phase conductors of the 10kV distribution cable under test. The detection method includes:

[0008] The computer-generated control command is obtained. The control command carries a preset test voltage and a detection mode of the 10kV distribution cable under test determined according to the test requirements. The detection mode is any one of single-phase detection, two-phase detection, and three-phase detection.

[0009] In response to the control command, the control module is driven to control the power amplifier circuit to generate a drive signal. The drive signal is used to control the DC high voltage module to start generating a negative polarity DC high voltage, indicate the connection status of the high voltage relay according to the detection mode, control the high voltage switch module to close, and drive the three-phase partial discharge detection unit to generate the detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high voltage relay.

[0010] The detection data is collected through the sampling module;

[0011] The computer filters the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test; the detection result of the 10kV distribution cable under test is determined based on the partial discharge data and voltage signal.

[0012] Preferably, determining the test result of the 10kV distribution cable under test based on the partial discharge data and voltage signal includes:

[0013] A partial discharge spectrum phase diagram is constructed based on the partial discharge data and voltage signal;

[0014] The detection results of the 10kV distribution cable under test are obtained by analyzing the partial discharge spectrum phase diagram according to the detection mode.

[0015] Preferably, if the detection mode is single-phase detection, the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes:

[0016] If a partial discharge pulse of a first amplitude is determined from the partial discharge spectrum phase diagram, then it is determined that the first detection phase has partial discharge.

[0017] Preferably, if the detection mode is two-phase detection, the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes:

[0018] During the detection period, the second amplitude corresponding to the partial discharge pulse present in the second detection phase and the third amplitude corresponding to the partial discharge pulse present in the third detection phase are obtained, and the second amplitude and the third amplitude are compared.

[0019] If the second amplitude is greater than the third amplitude, then it is determined that there is partial discharge in the second detection phase and no partial discharge in the third detection phase.

[0020] If the third amplitude is greater than the second amplitude, then it is determined that the third detection phase has partial discharge, while the second detection phase does not have partial discharge.

[0021] If at a first preset time the second amplitude is greater than the third amplitude, and at a second preset time the third amplitude is greater than the second amplitude, then it is determined that both the second detection phase and the third detection phase have partial discharge.

[0022] Wherein, the first preset time and the second preset time are times within the detection time period.

[0023] Preferably, if the detection mode is three-phase detection, the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes:

[0024] During the detection period, the fourth amplitude corresponding to the partial discharge pulse present in the fourth detection phase, the fifth amplitude corresponding to the partial discharge pulse present in the fifth detection phase, and the sixth amplitude corresponding to the partial discharge pulse present in the sixth detection phase are acquired, and the fourth amplitude, the fifth amplitude, and the sixth amplitude are compared.

[0025] If the fourth amplitude is greater than both the fifth and sixth amplitudes, then it is determined that the fourth detection phase has partial discharge, while the fifth and sixth detection phases do not have partial discharge.

[0026] If the fifth amplitude value is greater than both the fourth and sixth amplitude values, then it is determined that the fifth detection phase has partial discharge, while the fourth and sixth detection phases do not have partial discharge.

[0027] If the sixth amplitude value is greater than both the fourth and fifth amplitude values, then it is determined that the sixth detection phase has partial discharge, while the fourth and fifth detection phases do not have partial discharge.

[0028] If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, then it is determined that both the fourth detection phase and the fifth detection phase have partial discharge, and the sixth detection phase does not have partial discharge.

[0029] If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fourth detection phase and the sixth detection phase have partial discharge, and the fifth detection phase does not have partial discharge.

[0030] If at the third preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fifth detection phase and the sixth detection phase have partial discharge, and the fourth detection phase does not have partial discharge.

[0031] If at the fifth preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, at the sixth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the seventh preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that partial discharge exists in the fourth detection phase, the fifth detection phase, and the sixth detection phase.

[0032] The third preset time, the fourth preset time, the fifth preset time, the sixth preset time, and the seventh preset time are times within the detection time period.

[0033] Preferably, the connection end between the detection phase and the three-phase partial discharge detection unit is the starting end; the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes:

[0034] The pulse time difference at which the same partial discharge pulse is detected is determined based on the partial discharge pulse of the detected phase.

[0035] Based on the pulse time difference, the total length of the 10kV distribution cable under test, and the wave velocity, the distance between the partial discharge defect and the starting end is calculated, and the defect location result of the 10kV distribution cable under test is obtained.

[0036] Preferably, the step of filtering the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test includes:

[0037] The detection data is high-pass filtered to obtain the partial discharge data of the 10kV distribution cable under test;

[0038] The detection data is low-pass filtered to obtain the voltage signal of the 10kV distribution cable under test.

[0039] Preferably, the detection method further includes:

[0040] Obtain the first shutdown command generated by the computer;

[0041] In response to the first shutdown command, the control module is driven to control the power amplifier circuit to generate a first shutdown signal, which is used to shut down the DC high voltage module.

[0042] If the preset test voltage is less than a preset multiple of the rated phase voltage of the 10kV distribution cable under test, and the voltage signal of the 10kV distribution cable under test attenuates to a first preset voltage value; or, if the preset test voltage is greater than or equal to a preset multiple of the rated phase voltage of the 10kV distribution cable under test, and the voltage signal of the 10kV distribution cable under test attenuates to a second preset voltage value, then it is determined that the voltage signal reaches a negative peak value, and the second shutdown command generated by the computer is obtained.

[0043] In response to the second shutdown command, the control module is driven to control the power amplifier circuit to generate a second shutdown signal. The second shutdown signal is used to shut down the high-voltage switch module and disconnect the high-voltage relay corresponding to the detection mode.

[0044] Secondly, embodiments of this application provide a detection system for partial discharge of oscillating waves in a 10kV distribution cable. The detection system includes a DC high-voltage module, an adjustable charging resistor module, a high-voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer. The three-phase partial discharge detection unit is connected to the three-phase conductors of the 10kV distribution cable under test.

[0045] The computer is connected to the control module and the sampling module respectively, and is used to generate control commands and send the control commands to the control module. The control commands carry a preset test voltage and the detection mode of the 10kV distribution cable under test determined according to the test requirements. The detection mode is any one of single-phase detection, two-phase detection and three-phase detection.

[0046] The control module is connected to the power amplifier circuit and is used to acquire and respond to the control command, and control the power amplifier circuit to generate a drive signal.

[0047] The power amplifier circuit is connected to the DC high voltage module, the adjustable charging resistor module, the high voltage switch module, and the three-phase partial discharge detection unit, respectively. It is used to send the drive signal to the DC high voltage module, the high voltage switch module, and the three-phase partial discharge detection unit. The drive signal is used to control the DC high voltage module to start generating negative polarity DC high voltage, indicate the connection status of the high voltage relay according to the detection mode, control the high voltage switch module to close, and drive the three-phase partial discharge detection unit to generate the detection data of the 10kV distribution cable under test.

[0048] The three-phase partial discharge detection unit is connected to the resonant inductor and the sampling module respectively, and is used to generate detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high voltage relay, and send the detection data to the sampling module.

[0049] The sampling module is used to collect the detection data and send the detection data to the computer;

[0050] The computer is also used to filter the detection data to obtain partial discharge data and voltage signals of the 10kV distribution cable under test; and to determine the detection result of the 10kV distribution cable under test based on the partial discharge data and voltage signals.

[0051] Preferably, the computer is used to determine the test result of the 10kV distribution cable under test based on the partial discharge data and voltage signal, including:

[0052] A partial discharge spectrum phase diagram is constructed based on the partial discharge data and voltage signal; the detection result of the 10kV distribution cable under test is obtained by analyzing the partial discharge spectrum phase diagram according to the detection mode.

[0053] Preferably, if the detection mode is single-phase detection, the computer is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0054] If a partial discharge pulse of a first amplitude is determined from the partial discharge spectrum phase diagram, then it is determined that the first detection phase has partial discharge.

[0055] Preferably, if the detection mode is two-phase detection, the computer is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0056] During the detection period, the second amplitude corresponding to the partial discharge pulse present in the second detection phase and the third amplitude corresponding to the partial discharge pulse present in the third detection phase are obtained, and the second amplitude and the third amplitude are compared.

[0057] If the second amplitude is greater than the third amplitude, then it is determined that there is partial discharge in the second detection phase and no partial discharge in the third detection phase.

[0058] If the third amplitude is greater than the second amplitude, then it is determined that the third detection phase has partial discharge, while the second detection phase does not have partial discharge.

[0059] If at a first preset time the second amplitude is greater than the third amplitude, and at a second preset time the third amplitude is greater than the second amplitude, then it is determined that both the second detection phase and the third detection phase have partial discharge.

[0060] Wherein, the first preset time and the second preset time are times within the detection time period.

[0061] Preferably, if the detection mode is three-phase detection, the computer is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0062] During the detection period, the fourth amplitude corresponding to the partial discharge pulse present in the fourth detection phase, the fifth amplitude corresponding to the partial discharge pulse present in the fifth detection phase, and the sixth amplitude corresponding to the partial discharge pulse present in the sixth detection phase are acquired, and the fourth amplitude, the fifth amplitude, and the sixth amplitude are compared.

[0063] If the fourth amplitude is greater than both the fifth and sixth amplitudes, then it is determined that the fourth detection phase has partial discharge, while the fifth and sixth detection phases do not have partial discharge.

[0064] If the fifth amplitude value is greater than both the fourth and sixth amplitude values, then it is determined that the fifth detection phase has partial discharge, while the fourth and sixth detection phases do not have partial discharge.

[0065] If the sixth amplitude value is greater than both the fourth and fifth amplitude values, then it is determined that the sixth detection phase has partial discharge, while the fourth and fifth detection phases do not have partial discharge.

[0066] If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, then it is determined that both the fourth detection phase and the fifth detection phase have partial discharge, and the sixth detection phase does not have partial discharge.

[0067] If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fourth detection phase and the sixth detection phase have partial discharge, and the fifth detection phase does not have partial discharge.

[0068] If at the third preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fifth detection phase and the sixth detection phase have partial discharge, and the fourth detection phase does not have partial discharge.

[0069] If at the fifth preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, at the sixth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the seventh preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that partial discharge exists in the fourth detection phase, the fifth detection phase, and the sixth detection phase.

[0070] The third preset time, the fourth preset time, the fifth preset time, the sixth preset time, and the seventh preset time are times within the detection time period.

[0071] Preferably, the connection end between the detection phase and the three-phase partial discharge detection unit is the starting end; the computer is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0072] The pulse time difference of the same partial discharge pulse detected is determined based on the partial discharge pulse of the detected phase; the distance between the partial discharge defect and the starting end is calculated based on the pulse time difference, the total length of the 10kV distribution cable under test, and the wave velocity, so as to obtain the defect location result of the 10kV distribution cable under test.

[0073] Preferably, the computer is used to filter the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test, including:

[0074] The detection data is subjected to high-pass filtering to obtain the partial discharge data of the 10kV distribution cable under test; the detection data is subjected to low-pass filtering to obtain the voltage signal of the 10kV distribution cable under test.

[0075] Preferably, the computer is further configured to generate a first shutdown command and send the first shutdown command to the control module;

[0076] The control module is also configured to acquire and respond to the first shutdown command, and control the power amplifier circuit to generate a first shutdown signal, the first shutdown signal being used to shut down the DC high voltage module;

[0077] The computer is further configured to determine when the voltage signal reaches a negative peak value and generate a second shutdown command if the preset test voltage is less than a preset multiple of the rated phase voltage of the 10kV distribution cable under test and the voltage signal of the 10kV distribution cable under test attenuates to a first preset voltage value, or if the preset test voltage is greater than or equal to a preset multiple of the rated phase voltage of the 10kV distribution cable under test and the voltage signal of the 10kV distribution cable under test attenuates to a second preset voltage value.

[0078] The control module is also used to acquire and respond to the second shutdown command, and control the power amplifier circuit to generate a second shutdown signal. The second shutdown signal is used to shut down the high-voltage switch module and the high-voltage relay corresponding to the disconnection detection mode.

[0079] Thirdly, this application provides a detection device for partial discharge of oscillating waves in 10kV power distribution cables, the device comprising: a processor, a memory, and a system bus;

[0080] The processor and the memory are connected via the system bus;

[0081] The memory is used to store one or more programs, the one or more programs including instructions, which, when executed by the processor, cause the processor to perform the 10kV distribution cable oscillating wave partial discharge detection method described in the first aspect above.

[0082] Fourthly, this application provides a computer-readable storage medium that stores instructions that, when executed on a device, cause the device to perform the 10kV distribution cable oscillation wave partial discharge detection method described in the first aspect.

[0083] Therefore, this application has the following beneficial effects:

[0084] This application provides a method for detecting partial discharge of oscillating waves in a 10kV distribution cable. The method is applied to a detection system, which includes a DC high-voltage module, an adjustable charging resistor module, a high-voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer. The three-phase partial discharge detection unit is connected to the three-phase conductors of the 10kV distribution cable under test. First, the computer-generated control command is acquired. This command carries a preset test voltage and the detection mode of the 10kV distribution cable under test, determined according to the test requirements. The detection mode can be any one of single-phase detection, two-phase detection, or three-phase detection. Second, the drive control module responds to the control command, controlling the power amplifier circuit to generate a drive signal. This drive signal is used to control the DC high-voltage module to start generating a negative polarity DC high voltage, indicate the connection status of the high-voltage relay according to the detection mode, control the high-voltage switch module to close, and drive the three-phase partial discharge detection unit to generate detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high-voltage relay. The detection data is collected by the sampling module, and finally, the computer filters the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test. The detection result of the 10kV distribution cable under test is determined based on the partial discharge data and voltage signal. In this way, the detection mode can be selected independently according to the testing requirements, and the composition structure of the detection system can be adjusted based on the detection mode to realize the detection, which simplifies the detection process of 10kV distribution cables and can meet the requirement of simultaneous detection of three phases of the cable, thus improving the detection efficiency of 10kV distribution cables.

[0085] This application also provides a system corresponding to the above method, which has the same beneficial effects as the above method. Attached Figure Description

[0086] Figure 1 This is a schematic diagram of the structure of a detection system for partial discharge of oscillating waves in a 10kV power distribution cable, provided in an embodiment of this application.

[0087] Figure 2 A schematic diagram of the circuit structure of the adjustable charging resistor module 2 provided in the embodiments of this application;

[0088] Figure 3 A schematic diagram of the circuit structure of the three-phase partial discharge detection unit 3 provided in the embodiments of this application;

[0089] Figure 4 A flowchart illustrating a method for detecting partial discharge of oscillating waves in a 10kV power distribution cable, provided in an embodiment of this application;

[0090] Figure 5 A schematic diagram of a single-phase testing process for a 10kV distribution cable is provided for an embodiment of this application;

[0091] Figure 6 A schematic diagram of a two-phase detection process for a 10kV distribution cable provided in this application embodiment;

[0092] Figure 7 A schematic diagram of a three-phase testing process for a 10kV distribution cable provided in an embodiment of this application;

[0093] Figure 8 A schematic diagram of an oscillation wave during a cable charging process is provided in an embodiment of this application;

[0094] Figure 9 This is a schematic diagram of the structure of a detection device for partial discharge of oscillating waves in a 10kV power distribution cable, provided in an embodiment of this application. Detailed Implementation

[0095] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0096] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0097] Currently, oscillating wave testing of the insulation of 10kV distribution cables requires separate testing of each of the three phases. First, one phase is tested, while the conductors and shielding of the other two non-tested phases are grounded. After testing that phase, the next phase is tested using the same method. During phase switching, the grounding at the cable end also needs to be replaced. The entire process is time-consuming, labor-intensive, and cumbersome. With the power grid companies' efforts to improve efficiency, some researchers have proposed simultaneously conducting partial discharge testing of all three phases of the cable, directly connecting the high-voltage output of the oscillating wave to the three phases. However, the transmission process of partial discharge signals in parallel cables is very complex, posing significant difficulties for defect location. Therefore, the existing methods for testing 10kV distribution cables suffer from cumbersome defect location and low testing efficiency.

[0098] This application provides a method and system for detecting partial discharge of oscillating waves in a 10kV distribution cable. The detection method is applied to a detection system, which includes a DC high-voltage module, an adjustable charging resistor module, a high-voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer; the three-phase partial discharge detection unit is connected to the three-phase conductors of the 10kV distribution cable under test. First, the computer-generated control command is acquired. This command carries a preset test voltage and the detection mode of the 10kV distribution cable under test, determined according to the test requirements. The detection mode can be any one of single-phase detection, two-phase detection, or three-phase detection. Second, the drive control module responds to the control command, controlling the power amplifier circuit to generate a drive signal. This drive signal is used to control the DC high-voltage module to start generating a negative polarity DC high voltage, indicate the connection status of the high-voltage relay according to the detection mode, control the high-voltage switch module to close, and drive the three-phase partial discharge detection unit to generate detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high-voltage relay. The detection data is collected by the sampling module, and finally, the computer filters the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test. The detection result of the 10kV distribution cable under test is determined based on the partial discharge data and voltage signal. In this way, the detection mode can be selected independently according to the testing requirements, and the composition structure of the detection system can be adjusted based on the detection mode to realize the detection, which simplifies the detection process of 10kV distribution cables and can meet the requirement of simultaneous detection of three phases of the cable, thus improving the detection efficiency of 10kV distribution cables.

[0099] To facilitate understanding of the technical solutions provided in the embodiments of this application, the following description, in conjunction with the accompanying drawings, illustrates a method and system for detecting partial discharge of oscillating waves in a 10kV distribution cable.

[0100] First, the detection system for partial discharge of oscillating waves in 10kV distribution cables will be explained.

[0101] See Figure 1 , Figure 1 This is a schematic diagram of the structure of a 10kV power distribution cable oscillation wave partial discharge detection system provided in an embodiment of this application.

[0102] The detection system includes a DC high-voltage module 1, an adjustable charging resistor module 2, a high-voltage switch module S, a resonant inductor L, a three-phase partial discharge detection unit 3, a power amplifier circuit 4, a control module 5, a sampling module 6, and a computer 7. The power amplifier circuit 4 is connected to the DC high-voltage module 1, the adjustable charging resistor module 2, the high-voltage switch module S, the three-phase partial discharge detection unit 3, and the control module 5. The adjustable charging resistor module 2 is also connected to the DC high-voltage module 1, the high-voltage switch module S, and the resonant inductor L. The resonant inductor L is also connected to the high-voltage switch module S and the three-phase partial discharge detection unit 3. The sampling module 6 is connected to the three-phase partial discharge detection unit 3 and the computer 7. The control module 5 is also connected to the computer 7. The DC high-voltage module 1, the high-voltage switch module 5, and the three-phase partial discharge detection unit 3 are all grounded. The DC high-voltage module 1 is used to connect to an external 220V AC power supply, generating a maximum DC high voltage of 30kV.

[0103] See Figure 2 , Figure 2 This is a schematic diagram of the circuit structure of the adjustable charging resistor module 2 provided in this embodiment. The adjustable charging resistor module 2 consists of high-voltage resistors R1-R4 and high-voltage relays J1-J3, where R1 = 1MΩ, R2 = R3 = R4 = 4MΩ, and the control circuit of the high-voltage relays J1-J3 is connected to the control module 5. The high-voltage relays J1-J3 can be high-voltage DC relays. During the charging process of the power distribution cable, the adjustable charging resistor module 2 can gradually reduce the resistance value according to the charging voltage level. The resistance value is dynamically adjusted by controlling the opening and closing states of the high-voltage relays J1-J3, thereby reducing charging time and improving charging efficiency.

[0104] The high-voltage switch module 5 is composed of multiple bidirectional IGBT circuits or multiple thyristors connected in series.

[0105] The resonant inductor L is composed of two high-voltage partial discharge-free air-core inductors connected in series, with one of the resonant inductors connected in parallel with the high-voltage relay J7. The inductance value L of each inductor can be 0.5H, and the DC resistance value RL of the inductor can be 12Ω. The DC resistance value of the inductor is the resistance value of the device itself. This application does not limit the inductance value or the DC resistance value of the inductor; the relevant data values ​​of the electronic device can be determined according to the actual situation.

[0106] See Figure 3 , Figure 3This is a schematic diagram of the circuit structure of the three-phase partial discharge detection unit 3 provided in this embodiment. The three-phase partial discharge detection unit 3 consists of high-voltage relays J4-J6, blocking inductors LA, LB, and LC, and partial discharge detection impedances for each phase. The three-phase outputs of the three-phase partial discharge detection unit 3 are respectively connected to the A, B, and C phase conductors of the 10kV distribution cable under test via high-voltage flexible cables. Other types of cables can also be used for connection, and this embodiment is not limited to this. High-voltage flexible cables are generally used in the field for ease of connection.

[0107] The control circuits of high-voltage relays J4-J6 are connected to control module 5. High-voltage relays J4-J6 can be gas-insulated high-voltage relays with a peak operating voltage of 35kV, a continuous current capability of 10A, and an operating time of 15ms.

[0108] The blocking inductors LA, LB, and LC are air-core partial discharge-free inductors with an inductance value of 1mH. The blocking inductors are used to block the high-frequency signals of partial discharge between phases, preventing signal coupling between phases. This facilitates the phase identification of partial discharge signals and improves the detection sensitivity of the partial discharge detection impedance. Otherwise, the corresponding signals cannot be extracted for analysis.

[0109] The partial discharge detection impedance is composed of an RC-type detection impedance, and its output is connected to the sampling module. By high-pass filtering the acquired signal, partial discharge data can be obtained; by low-pass filtering the acquired signal, the voltage signal on the 10kV distribution cable under test can be obtained.

[0110] The control module 5 is used to receive instructions from the computer 7, such as control instructions and shutdown instructions, and drive the power amplifier circuit 4 to generate corresponding drive signals to control the DC high voltage module 1, the adjustable charging resistor module 2, the high voltage switch module S, and the three-phase partial discharge detection unit 3.

[0111] See Figure 4 , Figure 4 This is a flowchart illustrating a method for detecting partial discharge of oscillating waves in a 10kV distribution cable, provided in an embodiment of this application. This detection method is applied to the aforementioned 10kV distribution cable partial discharge detection system and specifically includes steps S401-S404. The 10kV distribution cable under test is disconnected from the power grid after power de-energization and discharged. The three-phase output of the three-phase partial discharge detection unit 3 is connected to the three-phase conductors of the 10kV distribution cable under test via a high-voltage flexible cable. The end conductors of the 10kV distribution cable under test are suspended, and the shielding and armor layers of phases A, B, and C are grounded, maintaining sufficient electrical distance between the three-phase conductors.

[0112] Before the test begins, control module 5 controls the high-voltage switch module S to be in the off state, and the high-voltage relays J1-J7 to be in the off state. The test voltage Ut is set for this test, and the test mode for the 10kV distribution cable under test is selected according to the test requirements. The test mode can be any one of single-phase test, two-phase test, or three-phase test. The test voltage Ut is specified by standard; it must be a multiple of the rated phase voltage U0 of the 10kV distribution cable under test. For example, the rated phase voltage U0 of a commonly used 10kV distribution cable is 8.7kV. According to the oscillation wave test standard, the test voltage Ut can be set to 0.5U0, 0.7U0, 0.9U0, 1U0, or 1.5U0, etc., as required by actual needs.

[0113] S401: Obtain the control command generated by the computer, the control command carrying a preset test voltage and the detection mode of the 10kV distribution cable under test determined according to the test requirements.

[0114] The user can trigger the computer 7 to generate control commands, which carry the test voltage Ut and the detection mode. The detection mode is one of single-phase detection, two-phase detection, or multi-phase detection selected by the user based on the test requirements. The connection status of each component in the system is determined according to the detection mode so that the circuit connection of the measurement circuit meets the detection requirements of the detection mode.

[0115] It should be noted that the embodiments of this application are applied to 10kV distribution cables, but can also be applied to other types of distribution cables. The 10kV distribution cable is only an example and is not intended to limit the distribution cable.

[0116] For details on the specific implementation of the detection operations corresponding to the detection mode, please refer to the description below.

[0117] S402: In response to the control command, the control module is driven to control the power amplifier circuit to generate a drive signal. The drive signal is used to control the DC high voltage module to start generating a negative polarity DC high voltage, indicate the connection status of the high voltage relay according to the detection mode, control the high voltage switch module to close, and drive the three-phase partial discharge detection unit to generate the detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high voltage relay.

[0118] The control commands generated by computer 7 are used to drive control module 5 to control power amplifier circuit 4 to generate drive signals. These drive signals are used to implement the detection corresponding to the detection mode.

[0119] Specifically, the drive signal can be used to control the DC high-voltage module 1 to start and generate a negative DC high voltage. This DC high-voltage module 1 is a relatively mature product; it only requires a drive signal to generate a DC high voltage. DC high voltage includes negative and positive DC high voltage. Negative DC high voltage is generally used for testing power distribution cables because it is more effective at stimulating defects in the cables compared to positive DC high voltage.

[0120] The drive signal can also be used to control the connection status of high-voltage relays J1-J7 according to the detection mode, and to control the closure of high-voltage switch module S. Before the detection begins, it controls the high-voltage switch module S to close, and controls the opening and closing status of high-voltage relays J1-J7 according to the detection mode.

[0121] Before the test, DC high-voltage module 1 is activated, generating a negative polarity DC high voltage. The three-phase partial discharge detection unit 3 detects the voltage signal of the 10kV distribution cable under test. Based on the preset ratio of the test voltage to this voltage signal, it controls J1-J3 to close sequentially, charging the 10kV distribution cable under test. After charging is complete, it controls the high-voltage switch module S to close, and controls DC high-voltage module 1 to close. The 10kV distribution cable under test and the inductor form an LC-damped oscillating circuit, generating an oscillating wave. The oscillating wave voltage and partial discharge signal are collected. This oscillating wave voltage signal is used to excite partial discharge at the cable insulation defect.

[0122] The voltage signal on the 10kV distribution cable under test will directly affect the amplitude and frequency of the oscillation wave signal.

[0123] When the voltage signal decays to a negative peak value, the high-voltage switch module is disconnected, and J1-J3 are disconnected.

[0124] If it is a single-phase detection, the high-voltage relay J7 is disconnected, and the opening and closing states of J4-J6 are controlled according to the detected phase.

[0125] If there are two detections, the control relay J7 is closed, and the opening and closing states of J4-J6 are controlled according to the detection phase.

[0126] If it is a three-phase detection, the control relays J4-J7 will close.

[0127] The drive signal can also be used to drive the three-phase partial discharge detection unit 3 to generate test data for the 10kV distribution cable under test based on the preset test voltage and the connection status of the high-voltage relays J4-J7. After determining the detection mode and completing the connection of the corresponding high-voltage relays based on the detection mode, the detection of the 10kV distribution cable under test can be performed. The detection data obtained can be analyzed to determine the partial discharge quantity and defect location results.

[0128] S403: The detection data is collected through the sampling module.

[0129] When the high-voltage switch module S closes, it generates an oscillation wave, which is the detection data. The sampling module 6 collects the detection data from the three-phase partial discharge detection unit 3 and sends the detection data to the computer 7. The computer 7 analyzes the detection data and obtains the detection results.

[0130] S404: The computer filters the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test; the detection result of the 10kV distribution cable under test is determined based on the partial discharge data and voltage signal.

[0131] Computer 7 filters the acquired oscillation wave. In one possible implementation, the detection data is filtered to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test. This includes: performing high-pass filtering on the detection data to obtain the partial discharge data of the 10kV distribution cable under test; and performing low-pass filtering on the detection data to obtain the voltage signal of the 10kV distribution cable under test.

[0132] By performing high-pass filtering on the collected detection data, the partial discharge data of the 10kV distribution cable under test can be obtained; by performing low-pass filtering on the collected detection data, the voltage signal of the 10kV distribution cable under test can be obtained.

[0133] In one possible implementation, determining the test result of the 10kV distribution cable under test based on the partial discharge data and voltage signal includes: constructing a partial discharge spectrum phase diagram based on the partial discharge data and voltage signal; and analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the test result of the 10kV distribution cable under test.

[0134] When the voltage reaches a certain level, defects in the cable insulation layer may prevent it from withstanding the applied electric field strength, leading to partial discharge. Partial discharge data can include the amplitude, phase, and number of discharges.

[0135] Under the same defect conditions, the higher the cable voltage, the greater the intensity (amplitude) of partial discharge tends to be. Higher voltage means a greater electric field strength, and thus an increase in voltage signal will increase the likelihood of partial discharge activity.

[0136] The horizontal axis of a Phase Resolved Partial Discharge (PRPD) spectrum represents the phase angle, indicating different time points within an AC voltage cycle. These time points correspond to the voltage waveform of the voltage signal, and the distribution of partial discharge activity across different phases of the voltage waveform can be observed through the PRPD spectrum.

[0137] Analyzing the partial discharge spectrum phase diagram yields the detection results. These results include the partial discharge quantity and location information, enabling the determination of the presence, quantity, and location of partial discharge, thus completing the inspection of the 10kV distribution cable.

[0138] Based on the content of steps S401-S404 above, it can be seen that the detection system includes a DC high voltage module, an adjustable charging resistor module, a high voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer; the three-phase partial discharge detection unit is connected to the three-phase conductor cores of the 10kV distribution cable under test. First, the computer-generated control command is acquired. This command carries a preset test voltage and the detection mode of the 10kV distribution cable under test, determined according to the test requirements. The detection mode can be any one of single-phase, two-phase, or three-phase detection. Second, the drive control module responds to the control command, controlling the power amplifier circuit to generate a drive signal. This drive signal is used to control the DC high-voltage module to start generating a negative polarity DC high voltage, indicate the connection status of the high-voltage relay according to the detection mode, control the closure of the high-voltage switch module, and drive the three-phase partial discharge detection unit to generate detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high-voltage relay. The detection data is collected by the sampling module, and finally, the computer filters the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test. The detection result of the 10kV distribution cable under test is determined based on the partial discharge data and voltage signal. In this way, the detection mode can be selected independently according to the test requirements, saving testing time. The detection process for 10kV distribution cables is simplified by adjusting the composition of the detection system based on the detection mode. It can also meet the requirement of simultaneously detecting three phases of the cable, thereby improving the detection efficiency of 10kV distribution cables.

[0139] In another embodiment of this application, the procedures for single-phase detection, two-phase detection, and three-phase detection are described respectively.

[0140] See Figure 5 , Figure 5 This is a schematic diagram of a single-phase detection process for a 10kV distribution cable provided in an embodiment of this application. The detection mode is single-phase detection. In one possible implementation, the detection result of the 10kV distribution cable under test is obtained by analyzing the partial discharge spectrum phase diagram according to the detection mode, including: determining from the partial discharge spectrum phase diagram that a partial discharge pulse of a first amplitude exists in the first detection phase, then determining that a partial discharge exists in the first detection phase.

[0141] The circuit system is initialized, and the DC high-voltage module 1 is started to generate a negative polarity DC high voltage. When the voltage signal of the 10kV distribution cable under test reaches 0.3Ut, the control module 5 controls J1 to close; when the voltage signal of the 10kV distribution cable under test reaches 0.5Ut, the control module 5 controls J2 to close; when the voltage signal of the 10kV distribution cable under test reaches 0.8Ut, the control module 5 controls J3 to close; when the voltage signal of the 10kV distribution cable under test reaches Ut, the control module 5 controls the high-voltage switch module S to close and the DC high-voltage module 1 to close, generating an oscillation wave. The acquisition module 6 acquires the voltage of this oscillation wave and the partial discharge signal.

[0142] Once the voltage signal attenuation reaches a preset threshold, the moment when the voltage signal of the 10kV distribution cable under test reaches its negative peak value can be determined. Specifically, if Ut < 1.3U0, the voltage signal reaches its negative peak value when it attenuates to 0.1Ut. Control module 5 then controls the high-voltage switch module S to disconnect, and the corresponding high-voltage relay is also disconnected. If Ut ≥ 1.3U0, the voltage signal reaches its negative peak value when it attenuates to 0.05Ut. Control module 5 then controls the high-voltage switch module S to disconnect, and the corresponding high-voltage relay is also disconnected.

[0143] If the test phase is phase A, then control J4 is disconnected; if the test phase is phase B, then control J5 is disconnected; if the test phase is phase C, then control J6 is disconnected.

[0144] When conducting oscillation wave testing, disconnect J1-J3. Close the corresponding high-voltage relays to perform the test. In single-phase testing mode, control module 5 controls high-voltage relay J7 to open via power amplifier circuit 4. If testing phase A, control high-voltage relay J4 to close, and high-voltage relays J5 and J6 to open. If testing phase B, control high-voltage relay J5 to close, and high-voltage relays J4 and J6 to open. If testing phase C, control high-voltage relay J6 to close, and high-voltage relays J4 and J5 to open.

[0145] The connection end between the detection phase and the three-phase partial discharge detection unit is the starting end (i.e., the test end). In one possible implementation, the detection result of the 10kV distribution cable under test is obtained by analyzing the partial discharge spectrum phase diagram according to the detection mode, including: determining the pulse time difference of the same partial discharge pulse being detected based on the partial discharge pulse of the detection phase; calculating the distance between the partial discharge defect and the starting end based on the pulse time difference, the total length of the 10kV distribution cable under test, and the wave velocity, and obtaining the defect location result of the 10kV distribution cable under test.

[0146] The test results include defect location results, which are analyzed and calculated based on the partial discharge signal of the test phase. The distance l between the partial discharge defect location and the test end is also included. PD The calculation is shown in the following formula (1):

[0147] l PD =l-Δt·v / 2 (1)

[0148] Where l is the total length of the cable, Δt is the pulse time difference between the detection of the same partial discharge signal, and v is the wave velocity. The pulse time difference Δt is calculated from adjacent partial discharge pulses of the first amplitude V1, after repeated detection of the first amplitude V1 partial discharge pulse.

[0149] The single-phase testing described above eliminates the need to switch between testing phases one by one, and also eliminates the need to replace the grounding at the end of the 10kV distribution cable under test during the phase switching process. Each phase can be tested one by one by switching the high-voltage relay, which is simple, time-saving, and improves testing efficiency.

[0150] See Figure 6 , Figure 6 This document provides a schematic diagram of a two-phase detection process for a 10kV distribution cable according to an embodiment of this application. The detection mode is two-phase detection, and the detection phases include a second detection phase and a third detection phase. In one possible implementation, the detection result of the 10kV distribution cable under test is obtained by analyzing the partial discharge spectrum phase diagram according to the detection mode, including: acquiring the second amplitude corresponding to the partial discharge pulse present in the second detection phase and the third amplitude corresponding to the partial discharge pulse present in the third detection phase during the detection time period, and comparing the second amplitude and the third amplitude.

[0151] If the second amplitude is greater than the third amplitude, it is determined that there is partial discharge in the second detection phase and no partial discharge in the third detection phase; if the third amplitude is greater than the second amplitude, it is determined that there is partial discharge in the third detection phase and no partial discharge in the second detection phase.

[0152] If at the first preset time point there is a second amplitude greater than the third amplitude, and at the second preset time point there is a third amplitude greater than the second amplitude, then it is determined that both the second detection phase and the third detection phase have partial discharge; wherein, the first preset time point and the second preset time point are times within the detection time period.

[0153] The specific steps for initializing the circuit system and for voltage signal attenuation can be found in the description of single-phase testing. Once the voltage signal of the 10kV distribution cable under test reaches its negative peak value, control module 5 controls the high-voltage switch module S to disconnect, thus disconnecting the high-voltage relay corresponding to the test.

[0154] If the test phases are A and B, then control J4 and J5 are disconnected; if the test phases are A and C, then control J4 and J6 are disconnected; if the test phases are B and C, then control J5 and J6 are disconnected.

[0155] When conducting oscillation wave testing, disconnect J1-J3. Close the corresponding high-voltage relay for testing. In two-phase testing mode, control module 5 controls high-voltage relay J7 to close via power amplifier circuit 4. If testing is performed on phases A and B, high-voltage relays J4 and J5 are closed, and high-voltage relay J6 is open. If testing is performed on phases A and C, high-voltage relays J4 and J6 are closed, and high-voltage relay J5 is open. If testing is performed on phases B and C, high-voltage relays J5 and J6 are closed, and high-voltage relay J4 is open.

[0156] During the detection period, the second amplitude V2 corresponding to the partial discharge pulse present in the second detection phase and the third amplitude V3 corresponding to the partial discharge pulse present in the third detection phase are obtained from the partial discharge spectrum phase diagram, and the second amplitude V2 and the third amplitude V3 are compared. The second and third detection phases can be any combination of phase A and phase B, phase A and phase C, or phase B and phase C.

[0157] If a partial discharge pulse exists in the second detection phase at a first preset time t1, corresponding to a pulse with a second amplitude V2, and the third detection phase does not have a pulse exceeding the noise background at time t1, or has a pulse with a third amplitude V3, where the second amplitude V2 is greater than the third amplitude V3, then it is considered that a partial discharge exists in the detection phase with the pulse of the second amplitude V2. Here, the first preset time t1 can be any time within the detection time period.

[0158] Throughout the entire detection period, the second amplitude V2 was greater than the third amplitude V3, indicating that partial discharge existed in the second detection phase but not in the third detection phase.

[0159] The location of the partial discharge defect in the second detection phase is determined according to the above formula (1).

[0160] Correspondingly, if the third detection phase has a partial discharge pulse at time t1, and the pulse has a third amplitude V3; and the second detection phase does not have a pulse exceeding the noise background at time t1, or has a pulse with a third amplitude V2, and the third amplitude V3 is greater than the second amplitude V2, then the third detection phase is considered to have partial discharge.

[0161] If the third amplitude V3 is greater than the second amplitude V2 throughout the entire detection period, it is determined that partial discharge exists in the third detection phase, while partial discharge does not exist in the second detection phase.

[0162] The location of the partial discharge defect in the third detection phase is determined according to the above formula (1).

[0163] In scenarios where both detection phases have partial discharge defects, the generation time of the partial discharge pulses in different phases is generally different. It is only necessary to determine which phase has a larger discharge pulse amplitude at a certain moment.

[0164] If at the first preset time t1, the second detection phase has a pulse signal with a second amplitude V2, and the third detection phase has no pulse signal or the pulse signal has a third amplitude V3, where the second amplitude V2 is greater than the third amplitude V3, and at the second preset time t2, the third detection phase has a pulse signal with a third amplitude V3, and the second detection phase has no pulse signal or the pulse signal has a second amplitude V2, where the third amplitude V3 is greater than the second amplitude V2, then it can be determined that both the second and third detection phases have partial discharge. The pulse signal corresponding to the detection is generated by the partial discharge defect phase in the detection phase. The location of the partial discharge defect in each phase is calculated based on formula (1).

[0165] Wherein, the first preset time t1 and the second preset time t2 are the times within the detection time period.

[0166] See Figure 7 , Figure 7 This is a schematic diagram of a three-phase testing process for a 10kV distribution cable, provided as an embodiment of this application. The testing mode is three-phase testing, and the tested phases include a fourth, fifth, and sixth testing phase.

[0167] In one possible implementation, the detection results of the 10kV distribution cable under test are obtained by analyzing the partial discharge spectrum phase diagram according to the detection mode, including: during the detection time period, acquiring the fourth amplitude corresponding to the partial discharge pulse of the fourth detection phase, the fifth amplitude corresponding to the partial discharge pulse of the fifth detection phase, and the sixth amplitude corresponding to the partial discharge pulse of the sixth detection phase, and comparing the fourth amplitude, the fifth amplitude, and the sixth amplitude.

[0168] If the fourth amplitude is greater than both the fifth and sixth amplitudes, then it is determined that partial discharge exists in the fourth detection phase, while partial discharge does not exist in the fifth and sixth detection phases; if the fifth amplitude is greater than both the fourth and sixth amplitudes, then it is determined that partial discharge exists in the fifth detection phase, while partial discharge does not exist in the fourth and sixth detection phases; if the sixth amplitude is greater than both the fourth and fifth amplitudes, then it is determined that partial discharge exists in the sixth detection phase, while partial discharge does not exist in the fourth and fifth detection phases.

[0169] If at the third preset time there is a fourth amplitude greater than the fifth and sixth amplitudes, and at the fourth preset time there is a fifth amplitude greater than the fourth and sixth amplitudes, then it is determined that partial discharge exists in both the fourth and fifth detection phases, and that partial discharge does not exist in the sixth detection phase.

[0170] If at the third preset time there is a fourth amplitude greater than the fifth and sixth amplitudes, and at the fourth preset time there is a sixth amplitude greater than the fourth and fifth amplitudes, then it is determined that partial discharge exists in both the fourth and sixth detection phases, and that partial discharge does not exist in the fifth detection phase.

[0171] If at the third preset time, the fifth amplitude is greater than the fourth and sixth amplitudes, and at the fourth preset time, the sixth amplitude is greater than the fourth and fifth amplitudes, then it is determined that partial discharge exists in both the fifth and sixth detection phases, and that partial discharge does not exist in the fourth detection phase.

[0172] If at the fifth preset time, the fourth amplitude is greater than the fifth and sixth amplitudes; at the sixth preset time, the fifth amplitude is greater than the fourth and sixth amplitudes; and at the seventh preset time, the sixth amplitude is greater than the fourth and fifth amplitudes, then it is determined that partial discharge exists in the fourth detection phase, the fifth detection phase, and the sixth detection phase.

[0173] The specific steps for initializing the circuit system and for voltage signal attenuation can be found in the description of single-phase testing. Once the voltage signal of the 10kV distribution cable under test reaches its negative peak value, control module 5 controls high-voltage switch module S to disconnect, and controls the high-voltage relay corresponding to the test to disconnect. The test phases are phases A, B, and C, and control J4-J6 to disconnect.

[0174] When conducting oscillation wave testing, disconnect J1-J3. Close the corresponding high-voltage relays to perform the test. If the test mode is three-phase testing, then control module 5 controls high-voltage relay J7 to close via power amplifier circuit 4; and controls high-voltage relays J4-J6 to close as well.

[0175] During the detection period, the fourth amplitude V4 corresponding to the partial discharge pulse present in the fourth detection phase, the fifth amplitude V5 corresponding to the partial discharge pulse present in the fifth detection phase, and the sixth amplitude V6 corresponding to the partial discharge pulse present in the sixth detection phase are obtained from the partial discharge spectrum phase diagram, and the fourth amplitude V4, the fifth amplitude V5, and the sixth amplitude V6 are compared.

[0176] If any one of the fourth amplitude value V4, the fifth amplitude value V5, and the sixth amplitude value V6 is greater than the other two amplitude values ​​during the detection time period, then the detection phase corresponding to that amplitude value has partial discharge, while the detection phases corresponding to the other two amplitude values ​​do not have partial discharge.

[0177] If at the third preset time t3, the fourth detection phase has a pulse signal with a fourth amplitude V4, the fifth detection phase has no pulse signal or the pulse signal has a fifth amplitude V5, the sixth detection phase has no pulse signal or the pulse signal has a sixth amplitude V6, and the fourth amplitude V4 is greater than the fifth amplitude V5, and the fourth amplitude V4 is greater than the sixth amplitude V6; if at the fourth preset time t4, the fifth detection phase has a pulse signal with a fifth amplitude V5, the fourth detection phase has no pulse signal or the pulse signal has a fourth amplitude V4, the sixth detection phase has no pulse signal or the pulse signal has a sixth amplitude V6, and the fifth amplitude V5 is greater than the fourth amplitude V4, and the fifth amplitude V5 is greater than the sixth amplitude V6; then it is determined that partial discharge exists in the fourth and fifth test phases, and no partial discharge exists in the sixth test phase.

[0178] Similarly, it is possible that partial discharge exists in the fourth and sixth test phases but not in the fifth test phase; or that partial discharge exists in the fifth and sixth test phases but not in the fourth test phase.

[0179] If at the fifth preset time t5, the fourth detection phase has a pulse signal with a fourth amplitude V4, the fifth detection phase has no pulse signal or the pulse signal is the fifth amplitude V5, the sixth detection phase has no pulse signal or the pulse signal is the sixth amplitude V6, the fourth amplitude V4 is greater than the fifth amplitude V5, and the fourth amplitude V4 is greater than the sixth amplitude V6; if at the sixth preset time t6, the fifth detection phase has a pulse signal with a fifth amplitude V5, the fourth detection phase has no pulse signal or the pulse signal is the fourth amplitude V4, and the sixth detection phase has no pulse signal or the pulse signal is the sixth amplitude V6. The pulse signal has a sixth amplitude V6, the fifth amplitude V5 is greater than the fourth amplitude V4, and the fifth amplitude V5 is greater than the sixth amplitude V6; at the seventh preset time t7, the sixth detection phase has a pulse signal with a sixth amplitude V6, the fourth detection phase has no pulse signal or the pulse signal is the fourth amplitude V4, the fifth detection phase has no pulse signal or the pulse signal is the fifth amplitude V5, the sixth amplitude V6 is greater than the fourth amplitude V4, and the sixth amplitude V6 is greater than the fifth amplitude V5; then it is determined that partial discharge exists in the fourth test phase, the fifth test phase, and the sixth detection phase.

[0180] Among them, the third preset time t3, the fourth preset time t4, the fifth preset time t5, the sixth preset time t6, and the seventh preset time t7 are the times within the detection time period.

[0181] The location of the partial discharge defect in the detection phase with partial discharge is located according to the above formula (1).

[0182] Thus, the adjustable high-voltage relay can avoid phase switching operations, saving time and labor costs; the detection system supports simultaneous detection of two phases or simultaneous detection of all three phases, saving measurement time, overcoming the problem that existing technologies cannot simultaneously locate defects in three phases, and improving detection efficiency.

[0183] In another embodiment of this application, the specific steps for attenuating the aforementioned voltage signal are described.

[0184] If the voltage signal of the 10kV distribution cable under test reaches Ut, the computer 7 will generate a first shutdown command. In response to the first shutdown command, the drive control module 5 will control the power amplifier circuit 4 to generate a first shutdown signal. The first shutdown signal is used to shut down the DC high voltage module 1.

[0185] If the preset test voltage Ut is less than a preset multiple of the rated phase voltage U0 of the 10kV distribution cable under test, and the voltage signal of the 10kV distribution cable under test decays to the first preset voltage value; or, if the preset test voltage Ut is greater than or equal to a preset multiple of the rated phase voltage U0 of the 10kV distribution cable under test, and the voltage signal of the 10kV distribution cable under test decays to the second preset voltage value, then the moment when the voltage signal reaches the negative peak value is determined. After the voltage signal reaches the negative peak value, a second shutdown command generated by computer 7 is obtained; in response to the second shutdown command, the drive control module 5 controls the power amplifier circuit 4 to generate a second shutdown signal, which is used to shut down the high-voltage switch module S and disconnect the high-voltage relay corresponding to the detection mode.

[0186] The preset multiple of the rated phase voltage U0 of the 10kV distribution cable under test can be 1.3 times, that is, to determine the relationship between Ut and 1.3U0; the first preset voltage value can be 0.1Ut, and the second preset voltage value can be 0.05Ut. This application embodiment does not limit this, and can be selected according to actual needs.

[0187] See Figure 8 , Figure 8 This is a schematic diagram of an oscillation wave during a cable charging process, provided as an embodiment of this application.

[0188] In the three different detection modes mentioned above, after reaching the negative peak value, the high-voltage switch module S and the corresponding high-voltage relay are disconnected.

[0189] At the negative peak of the voltage, the current is 0, so the high-voltage switch module S can be disconnected.

[0190] In this embodiment, a negative DC voltage is used to charge the 10kV distribution cable under test. The high-voltage switch module S is switched off at the negative peak, preventing the stored electrical energy in the cable from being released and allowing the cable to maintain the negative voltage. Furthermore, this voltage level has been determined (less than 0.1Ut or 0.05Ut), indicating a low voltage value that will not affect the switch.

[0191] During the next voltage boost test (e.g., 0.5U0 needs to be tested once, then 0.7U0 needs to be tested three times, then 1U0 needs to be tested three times, etc.), the cable can be charged through the negative polarity DC high voltage module 1 on the basis of the existing voltage of the cable itself. The cable itself also has a voltage of the same polarity, so there is no need to start charging from 0, which can improve charging efficiency and save energy.

[0192] The foregoing embodiments of this application provide a method for detecting partial discharge of oscillating waves in a 10kV distribution cable. Next, we will describe a detection system for partial discharge of oscillating waves in a 10kV distribution cable, also provided in this application, used to perform the aforementioned... Figure 4 The method is shown below. The function of the 10kV distribution cable oscillating wave partial discharge detection system will be explained next. A schematic diagram of the structure of the 10kV distribution cable oscillating wave partial discharge detection system is shown below. Figure 1 As shown, it includes a DC high voltage module 1, an adjustable charging resistor module 2, a high voltage switch module S, a resonant inductor L, a three-phase partial discharge detection unit 3, a power amplifier circuit 4, a control module 5, a sampling module 6, and a computer 7.

[0193] in,

[0194] The three-phase partial discharge detection unit 3 is connected to the three-phase conductor core of the 10kV distribution cable under test;

[0195] The computer 7 is connected to the control module 5 and the sampling module 6 respectively, and is used to generate control commands and send the control commands to the control module 5. The control commands carry a preset test voltage and the detection mode of the 10kV distribution cable under test determined according to the test requirements. The detection mode is any one of single-phase detection, two-phase detection and three-phase detection.

[0196] The control module 5 is connected to the power amplifier circuit 4 and is used to acquire and respond to the control command, and control the power amplifier circuit 4 to generate a drive signal.

[0197] The power amplifier circuit 4 is connected to the DC high voltage module 1, the adjustable charging resistor module 2, the high voltage switch module S, and the three-phase partial discharge detection unit 3, respectively. It is used to send the drive signal to the DC high voltage module 1, the high voltage switch module S, and the three-phase partial discharge detection unit 3. The drive signal is used to control the DC high voltage module 1 to start generating negative polarity DC high voltage, indicate the connection status of the high voltage relay according to the detection mode, control the high voltage switch module S to close, and drive the three-phase partial discharge detection unit 3 to generate the detection data of the 10kV distribution cable under test.

[0198] The three-phase partial discharge detection unit 3 is connected to the resonant inductor L and the sampling module 6 respectively, and is used to generate detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high voltage relay, and send the detection data to the sampling module 6.

[0199] The sampling module 6 is used to collect the detection data and send the detection data to the computer 7;

[0200] The computer 7 is further configured to filter the detection data to obtain partial discharge data and voltage signals of the 10kV distribution cable under test; and to determine the detection result of the 10kV distribution cable under test based on the partial discharge data and voltage signals.

[0201] Preferably, the computer 7 is used to determine the test result of the 10kV distribution cable under test based on the partial discharge data and voltage signal, including:

[0202] A partial discharge spectrum phase diagram is constructed based on the partial discharge data and voltage signal; the detection result of the 10kV distribution cable under test is obtained by analyzing the partial discharge spectrum phase diagram according to the detection mode.

[0203] Preferably, if the detection mode is single-phase detection, the computer 7 is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0204] If a partial discharge pulse of a first amplitude is determined from the partial discharge spectrum phase diagram, then it is determined that the first detection phase has partial discharge.

[0205] Preferably, if the detection mode is two-phase detection, the computer 7 is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0206] During the detection period, the second amplitude corresponding to the partial discharge pulse present in the second detection phase and the third amplitude corresponding to the partial discharge pulse present in the third detection phase are obtained, and the second amplitude and the third amplitude are compared.

[0207] If the second amplitude is greater than the third amplitude, then it is determined that there is partial discharge in the second detection phase and no partial discharge in the third detection phase.

[0208] If the third amplitude is greater than the second amplitude, then it is determined that the third detection phase has partial discharge, while the second detection phase does not have partial discharge.

[0209] If at a first preset time the second amplitude is greater than the third amplitude, and at a second preset time the third amplitude is greater than the second amplitude, then it is determined that both the second detection phase and the third detection phase have partial discharge.

[0210] Wherein, the first preset time and the second preset time are times within the detection time period.

[0211] Preferably, if the detection mode is three-phase detection, the computer 7 is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0212] During the detection period, the fourth amplitude corresponding to the partial discharge pulse present in the fourth detection phase, the fifth amplitude corresponding to the partial discharge pulse present in the fifth detection phase, and the sixth amplitude corresponding to the partial discharge pulse present in the sixth detection phase are acquired, and the fourth amplitude, the fifth amplitude, and the sixth amplitude are compared.

[0213] If the fourth amplitude is greater than both the fifth and sixth amplitudes, then it is determined that the fourth detection phase has partial discharge, while the fifth and sixth detection phases do not have partial discharge.

[0214] If the fifth amplitude value is greater than both the fourth and sixth amplitude values, then it is determined that the fifth detection phase has partial discharge, while the fourth and sixth detection phases do not have partial discharge.

[0215] If the sixth amplitude value is greater than both the fourth and fifth amplitude values, then it is determined that the sixth detection phase has partial discharge, while the fourth and fifth detection phases do not have partial discharge.

[0216] If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, then it is determined that both the fourth detection phase and the fifth detection phase have partial discharge, and the sixth detection phase does not have partial discharge.

[0217] If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fourth detection phase and the sixth detection phase have partial discharge, and the fifth detection phase does not have partial discharge.

[0218] If at the third preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fifth detection phase and the sixth detection phase have partial discharge, and the fourth detection phase does not have partial discharge.

[0219] If at the fifth preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, at the sixth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the seventh preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that partial discharge exists in the fourth detection phase, the fifth detection phase, and the sixth detection phase.

[0220] The third preset time, the fourth preset time, the fifth preset time, the sixth preset time, and the seventh preset time are times within the detection time period.

[0221] Preferably, the connection end between the detection phase and the three-phase partial discharge detection unit 3 is the starting end; the computer 7 is used to analyze the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test, including:

[0222] The pulse time difference of the same partial discharge pulse detected is determined based on the partial discharge pulse of the detected phase; the distance between the partial discharge defect and the starting end is calculated based on the pulse time difference, the total length of the 10kV distribution cable under test, and the wave velocity, so as to obtain the defect location result of the 10kV distribution cable under test.

[0223] Preferably, the computer 7 is used to filter the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test, including:

[0224] The detection data is subjected to high-pass filtering to obtain the partial discharge data of the 10kV distribution cable under test; the detection data is subjected to low-pass filtering to obtain the voltage signal of the 10kV distribution cable under test.

[0225] Preferably, the computer 7 is further configured to generate a first shutdown command and send the first shutdown command to the control module 5;

[0226] The control module 5 is further configured to acquire and respond to the first shutdown command, and control the power amplifier circuit 4 to generate a first shutdown signal, the first shutdown signal being used to shut down the DC high voltage module 1;

[0227] The computer 7 is further configured to determine when the voltage signal reaches a negative peak value and generate a second shutdown command if the preset test voltage is less than a preset multiple of the rated phase voltage of the 10kV distribution cable under test and the voltage signal of the 10kV distribution cable under test attenuates to a first preset voltage value, or if the preset test voltage is greater than or equal to a preset multiple of the rated phase voltage of the 10kV distribution cable under test and the voltage signal of the 10kV distribution cable under test attenuates to a second preset voltage value;

[0228] The control module 5 is also used to acquire and respond to the second shutdown command, and control the power amplifier circuit 4 to generate a second shutdown signal. The second shutdown signal is used to shut down the high-voltage switch module S and the high-voltage relay corresponding to the disconnection detection mode.

[0229] This application provides a detection system for partial discharge of oscillating waves in a 10kV distribution cable. The detection system includes a DC high-voltage module, an adjustable charging resistor module, a high-voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer. The three-phase partial discharge detection unit is connected to the three-phase conductors of the 10kV distribution cable under test.

[0230] The computer is connected to both the control module and the sampling module to generate control commands and send them to the control module. The control commands carry a preset test voltage and the detection mode of the 10kV distribution cable under test, determined according to the test requirements. The detection mode can be any one of single-phase, two-phase, or three-phase detection. The control module is connected to a power amplifier circuit to acquire and respond to the control commands, controlling the power amplifier circuit to generate drive signals. The power amplifier circuit is connected to the DC high-voltage module, the adjustable charging resistor module, the high-voltage switch module, and the three-phase partial discharge detection unit. It sends drive signals to these modules, controlling the DC high-voltage module to generate a negative polarity DC high voltage, indicating the connection status of the high-voltage relay according to the detection mode, controlling the high-voltage switch module to close, and driving the three-phase partial discharge detection unit to generate detection data for the 10kV distribution cable under test. The three-phase partial discharge detection unit is connected to the resonant inductor and the sampling module to generate detection data for the 10kV distribution cable under test based on the preset test voltage and the connection status of the high-voltage relay, and sends the detection data to the sampling module. The sampling module collects test data and sends it to the computer. The computer also filters the test data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test. Based on the partial discharge data and voltage signal, the test result of the 10kV distribution cable under test is determined. In this way, the test mode can be selected autonomously according to the test requirements, and the test system's components can be adjusted based on the test mode to achieve the test. This simplifies the test process for 10kV distribution cables and can meet the requirement of simultaneously testing three phases of the cable, thus improving the test efficiency of 10kV distribution cables.

[0231] Based on the method embodiment provided above, this application embodiment provides a detection device for partial discharge of oscillating waves in 10kV distribution cables. (See also...) Figure 9 The device includes: a processor, a memory, and a system bus;

[0232] The processor and the memory are connected via the system bus;

[0233] The memory is used to store one or more programs, the one or more programs including instructions, which, when executed by the processor, cause the processor to perform the detection method for partial discharge of oscillating waves in 10kV distribution cables as described in any of the above embodiments.

[0234] Based on the above-described method embodiments, this application provides a computer-readable storage medium storing instructions. When the instructions are executed on a device, the device performs the 10kV distribution cable oscillating partial discharge detection method described in any of the above embodiments.

[0235] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0236] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0237] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting partial discharge of oscillating waves in a 10kV distribution cable, characterized in that, The detection method is applied to a detection system for partial discharge of oscillating waves in 10kV distribution cables. The detection system includes a DC high-voltage module, an adjustable charging resistor module, a high-voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer. The three-phase partial discharge detection unit is connected to the three-phase conductors of the 10kV distribution cable under test. The detection method includes: The computer-generated control command is obtained. The control command carries a preset test voltage and a detection mode of the 10kV distribution cable under test determined according to the test requirements. The detection mode is any one of single-phase detection, two-phase detection, and three-phase detection. In response to the control command, the control module is driven to control the power amplifier circuit to generate a drive signal. The drive signal is used to control the DC high voltage module to start generating a negative polarity DC high voltage, indicate the connection status of the high voltage relay according to the detection mode, control the high voltage switch module to close, and drive the three-phase partial discharge detection unit to generate the detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high voltage relay. The detection data is collected through the sampling module; The computer filters the detection data to obtain partial discharge data and voltage signals of the 10kV distribution cable under test; the detection result of the 10kV distribution cable under test is determined based on the partial discharge data and voltage signals; wherein, determining the detection result of the 10kV distribution cable under test based on the partial discharge data and voltage signals includes: constructing a partial discharge spectrum phase diagram based on the partial discharge data and voltage signals; analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test; Wherein, if the detection mode is two-phase detection, the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes: During the detection period, the second amplitude corresponding to the partial discharge pulse present in the second detection phase and the third amplitude corresponding to the partial discharge pulse present in the third detection phase are obtained, and the second amplitude and the third amplitude are compared. If the second amplitude is greater than the third amplitude, then it is determined that there is partial discharge in the second detection phase and no partial discharge in the third detection phase. If the third amplitude is greater than the second amplitude, then it is determined that the third detection phase has partial discharge, while the second detection phase does not have partial discharge. If at a first preset time the second amplitude is greater than the third amplitude, and at a second preset time the third amplitude is greater than the second amplitude, then it is determined that both the second detection phase and the third detection phase have partial discharge; wherein, the first preset time and the second preset time are times within the detection time period.

2. The detection method according to claim 1, characterized in that, If the detection mode is single-phase detection, the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes: If a partial discharge pulse of a first amplitude is determined from the partial discharge spectrum phase diagram, then it is determined that the first detection phase has partial discharge.

3. The detection method according to claim 1, characterized in that, If the detection mode is three-phase detection, the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes: During the detection period, the fourth amplitude corresponding to the partial discharge pulse present in the fourth detection phase, the fifth amplitude corresponding to the partial discharge pulse present in the fifth detection phase, and the sixth amplitude corresponding to the partial discharge pulse present in the sixth detection phase are acquired, and the fourth amplitude, the fifth amplitude, and the sixth amplitude are compared. If the fourth amplitude is greater than both the fifth and sixth amplitudes, then it is determined that the fourth detection phase has partial discharge, while the fifth and sixth detection phases do not have partial discharge. If the fifth amplitude is greater than both the fourth and sixth amplitudes, then it is determined that the fifth detection phase has partial discharge, while the fourth and sixth detection phases do not have partial discharge. If the sixth amplitude value is greater than both the fourth and fifth amplitude values, then it is determined that the sixth detection phase has partial discharge, while the fourth and fifth detection phases do not have partial discharge. If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, then it is determined that both the fourth detection phase and the fifth detection phase have partial discharge, and the sixth detection phase does not have partial discharge. If at the third preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fourth detection phase and the sixth detection phase have partial discharge, and the fifth detection phase does not have partial discharge. If at the third preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the fourth preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that both the fifth detection phase and the sixth detection phase have partial discharge, and the fourth detection phase does not have partial discharge. If at the fifth preset time the fourth amplitude is greater than the fifth amplitude and the sixth amplitude, at the sixth preset time the fifth amplitude is greater than the fourth amplitude and the sixth amplitude, and at the seventh preset time the sixth amplitude is greater than the fourth amplitude and the fifth amplitude, then it is determined that partial discharge exists in the fourth detection phase, the fifth detection phase, and the sixth detection phase. The third preset time, the fourth preset time, the fifth preset time, the sixth preset time, and the seventh preset time are times within the detection time period.

4. The detection method according to any one of claims 1-3, characterized in that, The connection point between the detection phase and the three-phase partial discharge detection unit is the starting point; the step of analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes: The pulse time difference at which the same partial discharge pulse is detected is determined based on the partial discharge pulse of the detected phase. Based on the pulse time difference, the total length of the 10kV distribution cable under test, and the wave velocity, the distance between the partial discharge defect and the starting end is calculated, and the defect location result of the 10kV distribution cable under test is obtained.

5. The detection method according to claim 1, characterized in that, The filtering of the detection data to obtain the partial discharge data and voltage signal of the 10kV distribution cable under test includes: The detection data is high-pass filtered to obtain the partial discharge data of the 10kV distribution cable under test; The detection data is low-pass filtered to obtain the voltage signal of the 10kV distribution cable under test.

6. The detection method according to claim 1, characterized in that, The detection method further includes: Obtain the first shutdown command generated by the computer; In response to the first shutdown command, the control module is driven to control the power amplifier circuit to generate a first shutdown signal, which is used to shut down the DC high voltage module. If the preset test voltage is less than a preset multiple of the rated phase voltage of the 10kV distribution cable under test, and the voltage signal of the 10kV distribution cable under test attenuates to a first preset voltage value; or, if the preset test voltage is greater than or equal to a preset multiple of the rated phase voltage of the 10kV distribution cable under test, and the voltage signal of the 10kV distribution cable under test attenuates to a second preset voltage value, then it is determined that the voltage signal reaches a negative peak value, and the second shutdown command generated by the computer is obtained. In response to the second shutdown command, the control module is driven to control the power amplifier circuit to generate a second shutdown signal. The second shutdown signal is used to shut down the high-voltage switch module and disconnect the high-voltage relay corresponding to the detection mode.

7. A detection system for partial discharge of oscillating waves in 10kV distribution cables, characterized in that, The detection system includes a DC high-voltage module, an adjustable charging resistor module, a high-voltage switch module, a resonant inductor, a three-phase partial discharge detection unit, a power amplifier circuit, a control module, a sampling module, and a computer; the three-phase partial discharge detection unit is connected to the three-phase conductors of the 10kV distribution cable under test. The computer is connected to the control module and the sampling module respectively, and is used to generate control commands and send the control commands to the control module. The control commands carry a preset test voltage and the detection mode of the 10kV distribution cable under test determined according to the test requirements. The detection mode is any one of single-phase detection, two-phase detection and three-phase detection. The control module is connected to the power amplifier circuit and is used to acquire and respond to the control command, and control the power amplifier circuit to generate a drive signal. The power amplifier circuit is connected to the DC high voltage module, the adjustable charging resistor module, the high voltage switch module, and the three-phase partial discharge detection unit, respectively. It is used to send the drive signal to the DC high voltage module, the high voltage switch module, and the three-phase partial discharge detection unit. The drive signal is used to control the DC high voltage module to start generating negative polarity DC high voltage, indicate the connection status of the high voltage relay according to the detection mode, control the high voltage switch module to close, and drive the three-phase partial discharge detection unit to generate the detection data of the 10kV distribution cable under test. The three-phase partial discharge detection unit is connected to the resonant inductor and the sampling module respectively, and is used to generate detection data of the 10kV distribution cable under test based on the preset test voltage and the connection status of the high voltage relay, and send the detection data to the sampling module. The sampling module is used to collect the detection data and send the detection data to the computer; The computer is further configured to filter the detection data to obtain partial discharge data and voltage signals of the 10kV distribution cable under test; and to determine the detection result of the 10kV distribution cable under test based on the partial discharge data and voltage signals. Specifically, determining the detection result of the 10kV distribution cable under test based on the partial discharge data and voltage signals includes: constructing a partial discharge spectrum phase diagram based on the partial discharge data and voltage signals; analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test; wherein, if the detection mode is two-phase detection, analyzing the partial discharge spectrum phase diagram according to the detection mode to obtain the detection result of the 10kV distribution cable under test includes: acquiring the first... The second amplitude corresponding to the partial discharge pulse in the second detection phase and the third amplitude corresponding to the partial discharge pulse in the third detection phase are compared. If the second amplitude is greater than the third amplitude, it is determined that partial discharge exists in the second detection phase and partial discharge does not exist in the third detection phase. If the third amplitude is greater than the second amplitude, it is determined that partial discharge exists in the third detection phase and partial discharge does not exist in the second detection phase. If the second amplitude is greater than the third amplitude at a first preset time and the third amplitude is greater than the second amplitude at a second preset time, it is determined that partial discharge exists in both the second and third detection phases. Wherein, the first preset time and the second preset time are times within the detection time period.

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