Device and method for detecting partial discharge of cable

Abstract

The invention provides a partial discharge detection device and method for a cable. The three-phase partial discharge detection device of the cable comprises an inversion module, a phase shift module, a switch module and a partial discharge detection module, the partial discharge detection module is connected with the first phase, the second phase and the third phase of the detected cable. The inversion module is used for generating a first phase PWM waveform based on the DC voltage; the phase shift module is used for performing phase adjustment on the first phase PWM waveform to obtain a second phase PWM waveform and a third phase PWM waveform; the switch module comprises a first phase switch, a second phase switch and a third phase switch; the PWM waveform is transmitted to the tested cable by controlling on and off of a switch in the switch module, so that oscillation wave voltage is generated on three phases of the tested cable. By means of the device, the partial discharge signals of the three-phase detected cable can be measured at the same time, and the partial discharge detection efficiency and accuracy of the cable are improved.

Description

Technical Field

[0001] The present application relates to the field of discharge detection, and in particular to a device and method for detecting partial discharge of a cable. Background Art

[0002] Partial discharge refers to the discharge between electrodes that does not penetrate due to defects in equipment or devices during the production process or other external reasons under the action of high electric field strength. Partial discharge detection of cables is one of the important methods to discover potential defects and hidden dangers of cables.

[0003] In the prior art, cables generally use oscillating waves to carry out partial discharge detection, and the test steps are to test the three phases of the cable independently, that is, test one phase first, and then test the other phase. On the one hand, such testing takes more time and requires a phase change process that consumes manpower; on the other hand, the normal operating state of the cable is that the three phases are energized at the same time, with a phase difference of 120°. There is a certain difference between the three-phase separate test and the actual working condition. The prior art partial discharge detection of cables has the problem of low detection efficiency and accuracy. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a partial discharge detection device and method, equipment and storage medium for a cable, which can simultaneously measure the three-phase partial discharge of the cable and improve the efficiency and accuracy of partial discharge detection of the cable.

[0005] To achieve the above objectives, the present application discloses the following technical solutions:

[0006] In a first aspect, the present application provides a partial discharge detection device for a cable, comprising: an inverter module, a phase shift module, a switch module, and a partial discharge detection module; the partial discharge detection module is respectively connected to a first phase of a cable under test, a second phase of the cable under test, and a third phase of the cable under test;

[0007] An inverter module, used for generating a first-phase pulse width modulation (PWM) waveform based on a DC voltage;

[0008] The phase shift module is used to adjust the phase of the first phase PWM waveform to obtain a second phase PWM waveform after phase adjustment and a third phase PWM waveform after phase adjustment;

[0009] The switch module comprises a first phase switch, a second phase switch and a third phase switch; the switch module is used to control the conduction and disconnection of the first phase switch, the second phase switch and the third phase switch respectively;

[0010] The first-phase switch is used to transmit the first-phase PWM waveform to the first phase of the cable under test through the first-phase switch when it is turned on, and is also used to generate an oscillating wave voltage in the first phase when it is turned off, so that the first phase generates a first voltage; the second-phase switch is used to transmit the second-phase PWM waveform to the second phase of the cable under test through the second-phase switch when it is turned on, so that the second phase generates a second voltage, and is also used to generate an oscillating wave voltage in the second phase when it is turned off; the third-phase switch is used to generate a third voltage in the third phase when it is turned on, so that the third-phase PWM waveform is transmitted to the third phase of the cable under test through the third-phase switch, and is also used to generate an oscillating wave voltage in the third phase when it is turned off;

[0011] The partial discharge detection module is used to detect the first voltage, the second voltage and the third voltage, and is also used to detect the partial discharge signal of the first phase after the first phase generates an oscillating wave voltage; detect the partial discharge signal of the second phase after the second phase generates an oscillating wave voltage; and detect the partial discharge signal of the third phase after the third phase generates an oscillating wave voltage.

[0012] Optionally, the phase shift module includes a first phase shift submodule and a second phase shift submodule;

[0013] The first phase shift submodule is used to adjust the phase of the first phase PWM waveform to obtain the second phase PWM waveform;

[0014] The second phase shift submodule is used to adjust the phase of the second phase WPM waveform to obtain the third phase PWM waveform.

[0015] Optionally, the first phase-shift submodule and the second phase-shift submodule are both composed of an adjustable potentiometer and a capacitor.

[0016] Optionally, the first-phase switch includes a first series switch and a first parallel switch, the second-phase switch includes a second series switch and a second parallel switch, and the third-phase switch includes a third series switch and a third parallel switch;

[0017] The first series switch is used to transmit the first phase PWM waveform to the first phase of the cable under test through the first series switch when it is turned on, so that the first phase of the cable under test generates a first voltage, and is disconnected when the first voltage reaches a preset amplitude;

[0018] The first parallel switch is used to be turned on within a preset time after the first series switch is turned off, so that the first phase generates an oscillating wave voltage;

[0019] The second series switch is used to transmit the second phase PWM waveform to the second phase of the cable under test through the second series switch when it is turned on, so that the second phase of the cable under test generates a second voltage, and is disconnected when the second voltage reaches a preset amplitude;

[0020] The second parallel switch is used to be turned on within a preset time after the second series switch is turned off, so that the second phase generates an oscillating wave voltage;

[0021] The third series switch is used to transmit the third-phase PWM waveform to the third phase of the cable under test through the third series switch when it is turned on, so that the third phase of the cable under test generates a third voltage, and is disconnected when the third voltage reaches a preset amplitude;

[0022] The third parallel switch is used to be turned on within a preset time after the third series switch is turned off, so that the first phase generates an oscillating wave voltage.

[0023] Optionally, the first series switch, the first parallel switch, the second series switch, the second parallel switch, the third series switch and the third parallel switch are all composed of bidirectional insulated gate bipolar transistor IGBT switches.

[0024] Optionally, the device further comprises: a rectifier module;

[0025] The rectifier module is used to obtain the AC voltage of the mains and convert the AC voltage of the mains into a DC voltage.

[0026] Optionally, the device further comprises a transformer module;

[0027] The transformer module is used to boost the first-phase PWM waveform to obtain a first-phase PWM boost waveform, so that the first-phase PWM boost waveform is transmitted to the first phase of the cable under test; boost the second-phase PWM waveform to obtain a second-phase PWM boost waveform, so that the second-phase PWM boost waveform is transmitted to the second phase of the cable under test; boost the third-phase PWM waveform to obtain a third-phase PWM boost waveform, so that the third-phase PWM boost waveform is transmitted to the third phase of the cable under test.

[0028] Optionally, the transformation ratio of the transformer module is 1:20.

[0029] In a second aspect, the present application provides a method for detecting partial discharge of a cable, the method being applied to any one of the devices provided in the first aspect, the method comprising:

[0030] generating a first phase pulse width modulation (PWM) waveform based on the DC voltage;

[0031] Performing phase adjustment on the first-phase PWM waveform to obtain a second-phase PWM waveform after phase adjustment and a third-phase PWM waveform after phase adjustment;

[0032] Controlling the first phase switch to be turned on so that the first phase PWM waveform is transmitted to the first phase of the cable under test through the first phase switch, and controlling the first phase switch to be turned off so that the first phase generates an oscillating wave voltage; controlling the second phase switch to be turned on so that the second phase PWM waveform is transmitted to the second phase of the cable under test through the second phase switch, and controlling the second phase switch to be turned off so that the second phase generates an oscillating wave voltage; controlling the third phase switch to be turned on so that the third phase PWM waveform is transmitted to the third phase of the cable under test through the third phase switch, and controlling the third phase switch to be turned off so that the third phase generates an oscillating wave voltage;

[0033] After the first phase generates an oscillating wave voltage, a partial discharge signal of the first phase is detected; after the second phase generates an oscillating wave voltage, a partial discharge signal of the second phase is detected; after the third phase generates an oscillating wave voltage, a partial discharge signal of the third phase is detected.

[0034] Optionally, the phase adjustment of the first-phase PWM waveform to obtain a second-phase PWM waveform after the phase adjustment and a third-phase PWM waveform after the phase adjustment includes:

[0035] Performing phase adjustment on the first-phase PWM waveform to obtain the second-phase PWM waveform;

[0036] The second-phase PWM waveform is phase-adjusted to obtain the third-phase PWM waveform.

[0037] The present application provides a three-phase partial discharge detection device and method for a cable. In a three-phase partial discharge detection device for a cable, the device includes an inverter module, a phase shift module, a switch module, and a partial discharge detection module; the partial discharge detection module is respectively connected to the first phase, the second phase, and the third phase of the cable under test. The inverter module is used to generate a first-phase PWM waveform according to a DC voltage; the phase shift module is used to adjust the phase of the first-phase PWM waveform to obtain a second-phase PWM waveform and a third-phase PWM waveform; the switch module includes a first-phase switch, a second-phase switch, and a third-phase switch; by controlling the conduction and disconnection of the switch in the switch module, the PWM waveform is transmitted to the cable under test, so that an oscillating wave voltage is generated on the three phases of the cable under test. Through the above device, it is possible to achieve the simultaneous measurement of the partial discharge signal of the three-phase cable under test, thereby improving the efficiency and accuracy of the cable's partial discharge detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 It is a structural schematic diagram of a three-phase partial discharge detection device for a cable provided in an embodiment of the present application;

[0040] Figure 2 A schematic structural diagram of another partial discharge detection device for a cable provided in an embodiment of the present application;

[0041] Figure 3 is a structural schematic diagram of a first phase shift submodule provided in an embodiment of the present application;

[0042] Figure 4 is a structural schematic diagram of a switch module provided in an embodiment of the present application;

[0043] Figure 5 It is a structural schematic diagram of another cable partial discharge detection device provided by the present application;

[0044] Figure 6 It is a flow chart of a method for detecting partial discharge of a cable provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] To facilitate understanding of the technical solution provided by the present application, a partial discharge detection device for a cable provided by the present application will be described below in conjunction with the accompanying drawings. Figure 1 , which is a schematic diagram of the structure of a partial discharge detection device for a cable provided in an embodiment of the present application, such as Figure 1 As shown, the partial discharge detection device 100 includes: an inverter module 101, a phase shift module 102, a switch module 103 and a partial discharge detection module 104. The partial discharge detection module 104 is respectively connected to the first phase of the measured cable, the second phase of the measured cable and the third phase of the measured cable.

[0047] The inverter module 101 is used to generate a first-phase pulse width modulation (PWM) waveform based on a DC voltage.

[0048] In the embodiment of the present application, the DC voltage refers to the voltage used to generate a pulse width modulation (PWM) waveform. The present application does not limit the specific size of the DC voltage. As an example, the DC voltage may be 310V.

[0049] The present application does not limit the specific structure of the inverter module. As an example, the inverter module may include a single-phase bridge circuit, and the single-phase bridge circuit may be based on a DC voltage and the sequence of switches in the single-phase bridge circuit may be controlled to obtain a first-phase pulse width modulation PWM waveform. It is understood that the first-phase pulse width modulation PWM waveform is a frequency-adjustable PWM waveform.

[0050] The phase shift module 102 is used to perform phase adjustment on the first-phase PWM waveform to obtain a second-phase PWM waveform after phase adjustment and a third-phase PWM waveform after phase adjustment.

[0051] In an embodiment of the present application, the phase shift module 102 can receive the first phase PWM waveform sent by the inverter module 101. After obtaining the first phase PWM waveform, the first phase PWM waveform can be phase adjusted to obtain a second phase PWM waveform after phase adjustment and a third phase PWM waveform after phase adjustment.

[0052] It can be understood that the phase difference between the first phase PWM waveform, the second phase PWM waveform and the third phase PWM waveform in the embodiment of the present application is 120°, which is closer to the actual working condition of the cable and can better detect the partial discharge of the cable. That is, the first phase PWM waveform is used to transmit to the first phase of the cable under test, the second phase PWM waveform is used to transmit to the second phase of the cable under test, and the third phase PWM waveform is used to transmit to the third phase of the cable under test.

[0053] The present application does not limit the specific structure of the phase shift module 102 . As an example, the phase shift module includes a first phase shift submodule 1021 and a second phase shift submodule 1022 .

[0054] The first phase shift submodule 1021 is used to adjust the phase of the first phase PWM waveform to obtain a second phase PWM waveform.

[0055] The second phase shift submodule 1022 is used to adjust the phase of the second phase PWM waveform to obtain a third phase PWM waveform.

[0056] like Figure 2 As shown, Figure 2It is a structural schematic diagram of another partial discharge detection device for a cable provided in an embodiment of the present application. The present application can first adjust the phase of the first phase PWM waveform through the first phase shift submodule to obtain the second phase PWM waveform. After obtaining the second phase PWM waveform, the second phase PWM waveform is adjusted in phase through the second phase shift submodule to obtain the third phase PWM waveform. By adjusting in batches, the PWM waveform can be adjusted in phase by 120° each time, so as to quickly and accurately obtain the required second phase PWM waveform and third phase PWM waveform.

[0057] The present application does not limit the specific structure of the first phase-shifting submodule and the second phase-shifting submodule. As an example, the first phase-shifting submodule and the second phase-shifting submodule are both composed of an adjustable potentiometer and a capacitor. Figure 3 As shown, Figure 3 A schematic diagram of the structure of a first phase shift submodule provided in an embodiment of the present application. The first phase shift submodule includes two adjustable potentiometers and two capacitors, wherein V1 refers to the input port voltage and V2 refers to the output port voltage. It can be understood that the structure of the second phase shift submodule is the same as that of the first phase shift submodule, and will not be repeated here.

[0058] Specifically, the phase offset of the first phase shift submodule in the present application can be calculated according to the following formula:

[0059]

[0060] in, Represents the phase shift, ω represents the angular frequency of the PWM waveform, Ra represents the resistance value of the adjustable potentiometer, and C represents the capacitance value of the capacitor.

[0061] It is understandable that the resistance value of the adjustable potentiometer in the present application can be flexibly adjusted to meet the angular frequency range of different PWM waveforms. As an example, the resistance value of the adjustable potentiometer needs to satisfy the following equation at different angular frequencies:

[0062]

[0063] It is understandable that in order to generate an oscillating wave voltage for the cable under test, the angular frequency of the PWM waveform needs to be the same as the resonant frequency of the cable under test. The present application can first obtain the resonant frequency of the cable under test to determine the angular frequency of the PWM waveform.

[0064] The present application does not limit the specific method of obtaining the resonant frequency of the cable under test. As an example, the present application can output a PWM signal with a fixed amplitude of 30-500Hz and a step frequency of 0.5Hz through an inverter module, and measure the high voltage amplitude of the first phase, second phase or third phase of the cable under test, and record the frequency when the voltage is the highest. This frequency is the resonant frequency of the cable under test.

[0065] The switch module 103 includes a first phase switch 1031 , a second phase switch 1032 and a third phase switch 1033 ; the switch module is used to control the on and off of the first phase switch 1031 , the second phase switch 1032 and the third phase switch 1033 .

[0066] The first phase switch 1031 is used to transmit the first phase PWM waveform to the first phase of the cable under test through the first phase switch 1031 when it is turned on, so that the first phase generates a first voltage, and is also used to generate an oscillating wave voltage in the first phase when it is turned off.

[0067] The second phase switch 1032 is used to transmit the second phase PWM waveform to the second phase of the cable under test through the second phase switch 1032 when it is turned on, so that the second phase generates a second voltage, and is also used to generate an oscillating wave voltage in the second phase when it is turned off.

[0068] The third phase switch 1033 is used to transmit the third phase PWM waveform to the third phase of the cable under test through the third phase switch 1033 when it is turned on, so that the third phase generates a third voltage, and is also used to generate an oscillating wave voltage when it is turned off.

[0069] In the embodiment of the present application, by controlling the conduction of the first phase switch 1031, the second phase switch 1032 and the third phase switch 1033, a sine wave with a gradually increasing amplitude is generated on the first phase, the second phase and the third phase of the cable under test, and the phase difference of each phase is 120°, which is closer to the actual working state of the cable.

[0070] In the embodiment of the present application, the first phase switch 1031, the second phase switch 1032 and the third phase switch 1033 may also be controlled to be disconnected so that the first phase, the second phase and the third phase of the tested cable generate an oscillating wave voltage.

[0071] The partial discharge detection module 104 is used to detect the first voltage, the second voltage and the third voltage, and is also used to detect the partial discharge signal of the first phase after the oscillating wave voltage is generated in the first phase; detect the partial discharge signal of the second phase after the oscillating wave voltage is generated in the second phase; and detect the partial discharge signal of the third phase after the oscillating wave voltage is generated in the third phase.

[0072] It is understandable that the first voltage, the second voltage and the third voltage refer to the target voltages that are expected to be applied to the tested cable, for example, they may be 0.5U, 0.7U, 1U, etc. By real-time monitoring and feedback of the voltage on the tested cable, the pulse width of the PWM waveform is adjusted to gradually increase the voltage. When the monitored and fed-back voltage on the cable reaches the target value, the pulse width of the PWM is no longer increased.

[0073] In the embodiment of the present application, after the first phase, the second phase and the third phase of the tested cable generate an oscillating wave voltage, the partial discharge signal can be detected by the partial discharge detection module.

[0074] The present application does not limit the specific structure of the partial discharge detection module, which is well known to those skilled in the art and will not be described in detail here.

[0075] Through the above device, the disconnection and connection of each switch in the switch module can be flexibly controlled to generate an oscillating wave voltage in the first phase, second phase and third phase of the cable under test, thereby realizing the simultaneous measurement of the partial discharge signal of the three-phase cable under test, thereby improving the efficiency and accuracy of the cable partial discharge detection.

[0076] The present application does not limit the specific structures of the first phase switch, the second phase switch and the third phase switch. As a possible implementation method, the first phase switch includes a first series switch and a first parallel switch, the second phase switch includes a second series switch and a second parallel switch, and the third phase switch includes a third series switch and a third parallel switch.

[0077] The first series switch is used to transmit the first phase PWM waveform to the first phase of the cable under test through the first series switch when it is turned on, so that the first phase of the cable under test generates a first voltage, and is disconnected when the first voltage reaches a preset amplitude.

[0078] The first parallel switch is used to be turned on within a preset time after the first series switch is turned off, so that the first phase generates an oscillating wave voltage.

[0079] The second series switch is used to transmit the second phase PWM waveform to the second phase of the cable under test through the second series switch when it is turned on, so that the second phase of the cable under test generates a second voltage, and is disconnected when the second voltage reaches a preset amplitude.

[0080] The second parallel switch is used to be turned on within a preset time after the second series switch is turned off, so that the second phase generates an oscillating wave voltage.

[0081] The third series switch is used to transmit the third phase PWM waveform to the third phase of the cable under test through the third series switch when it is turned on, so that the third phase of the cable under test generates a third voltage, and is disconnected when the third voltage reaches a preset amplitude.

[0082] The third parallel switch is used to be turned on within a preset time after the third series switch is turned off, so that the first phase generates an oscillating wave voltage.

[0083] The present application does not limit the specific duration of the preset time. As an example, the preset time may be 1 μs.

[0084] It can be understood that the present application can open each series switch to generate a voltage in the first phase, the second phase and the third phase of the cable under test, and disconnect the series switch when the voltage reaches a preset threshold, and open the parallel switch, so that the first phase, the second phase and the third phase of the cable under test can generate an oscillating wave voltage, thereby exciting the local discharge defect in the cable under test to generate a local discharge signal, thereby detecting the local discharge signal.

[0085] The present application does not limit the specific structure of each series switch and parallel switch. As an example, the first series switch, the first parallel switch, the second series switch, the second parallel switch, the third series switch and the third parallel switch are all composed of bidirectional insulated gate bipolar transistor IGBT switches. Figure 4 As shown, Figure 4 A schematic diagram of the structure of a switch module provided in an embodiment of the present application. It is understood that in the embodiment of the present application, the first series switch may include: a first switch S1 and a second switch S2, and the first parallel switch may include: a third switch S3 and a fourth switch S4. The second series switch may include: a fifth switch S5 and a sixth switch S6; the second parallel switch may include: a seventh switch S7 and an eighth switch S8. The third series switch may include: a ninth switch S9 and a tenth switch S10; the third parallel switch may include: an eleventh switch S11 and a twelfth switch S12.

[0086] It can be understood that the present application can first control S1, S2, S5, S6, S9, S10 to be turned on, and control S3, S4, S7, S8, S11, S12 to be turned off, then the PWM waveform output by the inverter module will cause a sine wave with a gradually increasing amplitude to be generated on the cable under test, so that a corresponding voltage is generated on the cable under test. After the voltage reaches a preset amplitude, S1, S2, S5, S6, S9, S10 can be controlled to be turned off, and S3, S4, S7, S8, S11, S12 can be controlled to be turned on, so that the first phase, the second phase, and the third phase of the cable under test can generate an oscillating wave voltage, so that the cable under test can excite the local discharge defect in the cable to generate a local discharge signal, thereby detecting the local discharge signal.

[0087] The present application does not limit the detection order of the partial discharge signals of the first phase, the second phase and the third phase, and the detection order can be determined according to actual needs. As a method, the partial discharge signal of the first phase can be detected first, then the partial discharge signal of the second phase, and finally the partial discharge signal of the third phase. For example, when the voltage amplitude on the first phase reaches the preset amplitude, S1 and S2 are controlled to be turned off, and S3 and S4 are controlled to be turned on after 1μs. At this time, an oscillating wave voltage is generated on the first phase, and the partial discharge signal of the first phase can be detected by the partial discharge detection module.

[0088] After controlling S1 and S2 to turn off, after detecting that the voltage amplitude on the second phase reaches the preset amplitude, controlling S5 and S6 to turn off, and controlling S7 and S8 to turn on after 1μs. At this time, an oscillating wave voltage is generated on the second phase. While controlling S5 and S6 to turn off, the three-phase partial discharge detection module stops sampling, and resumes sampling after 3μs, so that the partial discharge signal of the second phase can be detected.

[0089] After controlling S5 and S6 to turn off, after detecting the high voltage amplitude on the C phase of the third phase, controlling S9 and S10 to turn off, and controlling S11 and S12 to turn on after 1μs. At this time, an oscillating wave voltage is generated on the third phase. While controlling S9 and S10 to turn off, the three-phase partial discharge detection module stops sampling, and resumes sampling after 3μs, so that the partial discharge signal of the third phase can be detected.

[0090] As a possible implementation, Figure 5 As shown, Figure 5 1 is a schematic structural diagram of another cable partial discharge detection device provided in the present application. The cable partial discharge detection device also includes a rectifier module 106 .

[0091] The rectifier module 106 is used to obtain the AC voltage of the mains and convert the AC voltage of the mains into a DC voltage.

[0092] It is understandable that the embodiment of the present application can convert the AC voltage of the mains into a DC voltage through a rectifier module, which is more convenient for the use of the partial discharge detection device of the cable. The present application does not limit the specific value of the AC voltage of the mains. As an example, the AC voltage of the mains is 220V.

[0093] As a possible implementation, Figure 5 As shown, a partial discharge detection device for a cable provided in the present application further includes a transformer module 107 and a resonant inductor module 108 .

[0094] The resonant inductor module 108 includes a first resonant inductor, a second resonant inductor and a third resonant inductor (not shown in the figure); the first resonant inductor is connected to the first phase through a local detection module; the second resonant inductor is connected to the second phase through a local detection module; the third resonant inductor is connected to the third phase through a local detection module; the transformer module 107 is used to boost the first-phase PWM waveform to obtain a first-phase PWM boost waveform, so that the first-phase PWM boost waveform is transmitted to the first phase of the cable under test and the first resonant inductor; boost the second-phase PWM waveform to obtain a second-phase PWM boost waveform, so that the second-phase PWM boost waveform is transmitted to the second phase of the cable under test and the second resonant inductor; boost the third-phase PWM waveform to obtain a third-phase PWM boost waveform, so that the third-phase PWM boost waveform is transmitted to the third phase of the cable under test and the third resonant inductor.

[0095] In the embodiment of the present application, the transformer module 107 can be connected to the switch module 103. The transformer module can also include three parts, which respectively boost the first phase PWM waveform, the second phase PWM waveform and the third phase PWM waveform, so as to transmit the boosted PWM waveform to the second phase, the second phase and the third phase of the tested cable respectively. It can be understood that the present application boosts the PWM waveform through the transformer module, so that the voltage on the tested cable can be a high voltage, the partial discharge information of the cable can be better detected, and the feasibility of partial discharge detection of the cable can be improved.

[0096] The present application does not limit the specific structure of the resonant inductor module 108. As an example, the resonant inductor module can use a coil winding with an iron core and be cast with epoxy, so that the resonant inductor has no partial discharge within a voltage of 30kV. By setting the resonant inductor, the partial discharge information of the cable can be better detected, and the feasibility of partial discharge detection of the cable can be improved.

[0097] The present application does not limit the transformation ratio of the transformer module, and the transformation ratio can be set according to actual conditions. As an example, the transformation ratio of the transformer module is 1:20. By flexibly setting the transformation ratio of the transformer module, the partial discharge information of the cable can be better detected, and the feasibility of partial discharge detection of the cable can be improved.

[0098] See also Figure 6 , Figure 6 This is a flow chart of a partial discharge detection method for a cable provided in an embodiment of the present application. The method is applied to any partial discharge detection device for a cable provided in the above embodiments, and the method includes S101-S104.

[0099] S101: Generate a first-phase pulse width modulation (PWM) waveform based on a DC voltage.

[0100] S102: performing phase adjustment on the first-phase PWM waveform to obtain a second-phase PWM waveform after phase adjustment and a third-phase PWM waveform after phase adjustment.

[0101] S103: Control the first phase switch to be turned on so that the first phase PWM waveform is transmitted to the first phase of the measured cable through the first phase switch, so that the first phase generates a first voltage, and control the first phase switch to be turned off so that the first phase generates an oscillating wave voltage; control the second phase switch to be turned on so that the second phase PWM waveform is transmitted to the second phase of the measured cable through the second phase switch, so that the second phase generates a second voltage, and control the second phase switch to be turned off so that the second phase generates an oscillating wave voltage; control the third phase switch to be turned on so that the third phase PWM waveform is transmitted to the third phase of the measured cable through the third phase switch, so that the third phase generates a third voltage, and control the third phase switch to be turned off so that the third phase generates an oscillating wave voltage.

[0102] S104: Detect the first voltage, the second voltage and the third voltage; after the first phase generates an oscillating wave voltage, detect the local discharge signal of the first phase; after the second phase generates an oscillating wave voltage, detect the local discharge signal of the second phase; after the third phase generates an oscillating wave voltage, detect the local discharge signal of the third phase.

[0103] Through the above method, the three-phase partial discharge of the cable can be measured simultaneously, thereby improving the efficiency and accuracy of partial discharge detection of the cable.

[0104] As a possible implementation method, before detecting the cable under test, the present application can disconnect the cable under test from the power grid after a power outage and discharge it, connect the local discharge detection module of the local discharge detection device to the first phase, the second phase, and the third phase of the cable under test, and ground the shielding layer and armor of the cable under test. The other end of the cable under test maintains a safe testing distance from the surrounding devices and the first phase, the second phase, and the third phase and is left suspended without connection. The shielding layer and armor at the other end are also grounded to improve the safety of local discharge detection.

[0105] As a possible implementation method, step S102 performs phase adjustment on the first-phase PWM waveform to obtain a second-phase PWM waveform after phase adjustment and a third-phase PWM waveform after phase adjustment, including: performing phase adjustment on the first-phase PWM waveform to obtain the second-phase PWM waveform; performing phase adjustment on the second-phase PWM waveform to obtain the third-phase PWM waveform.

[0106] As a possible implementation, when the first phase switch includes a first series switch and a first parallel switch, the second phase switch includes a second series switch and a second parallel switch, and the third phase switch includes a third series switch and a third parallel switch,

[0107] Step S103: controlling the first phase switch to be turned on so that the first phase PWM waveform is transmitted to the first phase of the measured cable through the first phase switch so that the first phase generates a first voltage, and controlling the first phase switch to be turned off so that the first phase generates an oscillating wave voltage; controlling the second phase switch to be turned on so that the second phase PWM waveform is transmitted to the second phase of the measured cable through the second phase switch so that the second phase generates a second voltage, and controlling the second phase switch to be turned off so that the second phase generates an oscillating wave voltage; controlling the third phase switch to be turned on so that the third phase PWM waveform is transmitted to the third phase of the measured cable through the third phase switch so that the third phase generates a third voltage, and controlling the third phase switch to be turned off so that the third phase generates an oscillating wave voltage, comprising the following steps:

[0108] A1: Control the first series switch to be turned on, so that the first-phase PWM waveform is transmitted to the first phase of the cable under test through the first series switch, so that the first phase of the cable under test generates a first voltage; and control the first series switch to be turned off when the first voltage reaches a preset amplitude.

[0109] A2: Control the first parallel switch to be turned on within a preset time after the first series switch is turned off, so that the first phase generates an oscillating wave voltage.

[0110] A3: Control the second series switch to be turned on, so that the second-phase PWM waveform is transmitted to the second phase of the cable under test through the second series switch, so that the second phase of the cable under test generates a second voltage; and control the second series switch to be turned off when the second voltage reaches a preset amplitude;

[0111] A4: Control the second parallel switch to be turned on within a preset time after the second series switch is turned off, so that the second phase generates an oscillating wave voltage.

[0112] A5: Control the third series switch to be turned on, so that the third-phase PWM waveform is transmitted to the third phase of the cable under test through the third series switch, so that the third phase of the cable under test generates a third voltage; and control the third series switch to be turned off when the third voltage reaches a preset amplitude;

[0113] A6: Control the third parallel-series switch to be turned on within a preset time after the third series switch is turned off, so that the third phase generates an oscillating wave voltage.

[0114] As a possible implementation, before step S101, the cable partial discharge detection method provided by the present application further includes: acquiring a mains AC voltage, and converting the mains AC voltage into a DC voltage.

[0115] As a possible implementation method, a partial discharge detection method for a cable provided in the present application also includes: boosting the first-phase PWM waveform to obtain a first-phase PWM boost waveform, so that the first-phase PWM boost waveform is transmitted to the first phase of the cable under test; boosting the second-phase PWM waveform to obtain a second-phase PWM boost waveform, so that the second-phase PWM boost waveform is transmitted to the second phase of the cable under test; boosting the third-phase PWM waveform to obtain a third-phase PWM boost waveform, so that the third-phase PWM boost waveform is transmitted to the third phase of the cable under test.

[0116] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0117] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0118] Specific examples are used herein to illustrate the principles and implementation methods of the present application, and the description of the above embodiments is only used to help understand the method and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A partial discharge detection device for a cable, characterized in that: The device comprises an inverter module, a phase shift module, a switch module, and a partial discharge detection module; the partial discharge detection module is respectively connected to the first phase of the tested cable, the second phase of the tested cable, and the third phase of the tested cable; An inverter module, used for generating a first-phase pulse width modulation (PWM) waveform based on a DC voltage; The phase shift module is used to adjust the phase of the first phase PWM waveform to obtain a second phase PWM waveform after phase adjustment and a third phase PWM waveform after phase adjustment; The switch module comprises a first phase switch, a second phase switch and a third phase switch; the switch module is used to control the conduction and disconnection of the first phase switch, the second phase switch and the third phase switch respectively; The first-phase switch is used to transmit the first-phase PWM waveform to the first phase of the cable under test through the first-phase switch when it is turned on, so that the first phase generates a first voltage, and is also used to generate an oscillating wave voltage in the first phase when it is turned off; the second-phase switch is used to transmit the second-phase PWM waveform to the second phase of the cable under test through the second-phase switch when it is turned on, so that the second phase generates a second voltage, and is also used to generate an oscillating wave voltage in the second phase when it is turned off; the third-phase switch is used to transmit the third-phase PWM waveform to the third phase of the cable under test through the third-phase switch when it is turned on, so that the third phase generates a third voltage, and is also used to generate an oscillating wave voltage in the third phase when it is turned off; The partial discharge detection module is used to detect the first voltage, the second voltage and the third voltage, and is also used to detect the partial discharge signal of the first phase after the first phase generates an oscillating wave voltage; detect the partial discharge signal of the second phase after the second phase generates an oscillating wave voltage; and detect the partial discharge signal of the third phase after the third phase generates an oscillating wave voltage.

2. The device according to claim 1, characterized in that The phase shift module includes a first phase shift submodule and a second phase shift submodule; The first phase shift submodule is used to adjust the phase of the first phase PWM waveform to obtain the second phase PWM waveform; The second phase shift submodule is used to adjust the phase of the second phase WPM waveform to obtain the third phase PWM waveform.

3. The device according to claim 2, characterized in that The first phase-shifting submodule and the second phase-shifting submodule are both composed of an adjustable potentiometer and a capacitor.

4. The device according to claim 1, characterized in that The first-phase switch includes a first series switch and a first parallel switch, the second-phase switch includes a second series switch and a second parallel switch, and the third-phase switch includes a third series switch and a third parallel switch; The first series switch is used to transmit the first phase PWM waveform to the first phase of the cable under test through the first series switch when it is turned on, so that the first phase of the cable under test generates the first voltage, and is disconnected when the first voltage reaches a preset amplitude; The first parallel switch is used to be turned on within a preset time after the first series switch is turned off, so that the first phase generates an oscillating wave voltage; The second series switch is used to transmit the second phase PWM waveform to the second phase of the cable under test through the second series switch when it is turned on, so that the second phase of the cable under test generates the second voltage, and is disconnected when the second voltage reaches a preset amplitude; The second parallel switch is used to be turned on within a preset time after the second series switch is turned off, so that the second phase generates an oscillating wave voltage; The third series switch is used to transmit the third-phase PWM waveform to the third phase of the cable under test through the third series switch when it is turned on, so that the third phase of the cable under test generates the third voltage, and is disconnected when the third voltage reaches a preset amplitude; The third parallel switch is used to be turned on within a preset time after the third series switch is turned off, so that the first phase generates an oscillating wave voltage.

5. The device according to claim 4, characterized in that The first series switch, the first parallel switch, the second series switch, the second parallel switch, the third series switch and the third parallel switch are all composed of bidirectional insulated gate bipolar transistor IGBT switches.

6. The device according to claim 1, characterized in that The device also includes: a rectifier module; The rectifier module is used to obtain the AC voltage of the mains and convert the AC voltage of the mains into a DC voltage.

7. The device according to claim 1, characterized in that The device also includes a transformer module and a resonant inductor module; The resonant inductor module includes a first resonant inductor, a second resonant inductor and a third resonant inductor; the first resonant inductor is connected to the first phase through the local detection module; the second resonant inductor is connected to the second phase through the local detection module; the third resonant inductor is connected to the third phase through the local detection module; The transformer module is used to boost the first-phase PWM waveform to obtain a first-phase PWM boost waveform, so that the first-phase PWM boost waveform is transmitted to the first phase of the cable under test and the first resonant inductor; boost the second-phase PWM waveform to obtain a second-phase PWM boost waveform, so that the second-phase PWM boost waveform is transmitted to the second phase of the cable under test and the second resonant inductor; boost the third-phase PWM waveform to obtain a third-phase PWM boost waveform, so that the third-phase PWM boost waveform is transmitted to the third phase of the cable under test and the third resonant inductor.

8. The device according to claim 7, characterized in that The transformer module has a transformation ratio of 1:

20.

9. A method for detecting partial discharge of a cable, characterized in that: The method is applied to the device according to any one of claims 1 to 8, and the method comprises: generating a first phase pulse width modulation (PWM) waveform based on the DC voltage; Performing phase adjustment on the first-phase PWM waveform to obtain a second-phase PWM waveform after phase adjustment and a third-phase PWM waveform after phase adjustment; Controlling the first phase switch to be turned on so that the first phase PWM waveform is transmitted to the first phase of the cable under test through the first phase switch, so that the first phase generates a first voltage, and controlling the first phase switch to be turned off so that the first phase generates an oscillating wave voltage; controlling the second phase switch to be turned on so that the second phase PWM waveform is transmitted to the second phase of the cable under test through the second phase switch, so that the second phase generates a second voltage, and controlling the second phase switch to be turned off so that the second phase generates an oscillating wave voltage; controlling the third phase switch to be turned on so that the third phase PWM waveform is transmitted to the third phase of the cable under test through the third phase switch, so that the third phase generates a third voltage, and controlling the third phase switch to be turned off so that the third phase generates an oscillating wave voltage; Detect the first voltage, the second voltage and the third voltage; after the first phase generates an oscillating wave voltage, detect the partial discharge signal of the first phase; after the second phase generates an oscillating wave voltage, detect the partial discharge signal of the second phase; after the third phase generates an oscillating wave voltage, detect the partial discharge signal of the third phase.

10. The method according to claim 9, characterized in that The phase adjustment of the first-phase PWM waveform to obtain a second-phase PWM waveform after the phase adjustment and a third-phase PWM waveform after the phase adjustment includes: The first-phase PWM waveform is phase-adjusted to obtain the second-phase PWM waveform; the second-phase PWM waveform is phase-adjusted to obtain the third-phase PWM waveform.

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