Method and device for testing space charge change of DC cable voltage using simulated lightning impulse

Abstract

The present invention discloses a method and device for testing space charge changes in DC cable voltage simulated by lightning impulses, relating to the field of high voltage and electrical insulation testing of insulating materials. The method comprises obtaining a space charge distribution obtained after a first voltage source acts on a DC cable; the space charge distribution comprises: a space charge distribution at a first moment and a space charge distribution at a second moment; the space charge distribution at the first moment and the space charge distribution at the second moment are at the time of the rising edge or the falling edge of the same simulated lightning impulse voltage; and based on the space charge distribution at the first moment and the space charge distribution at the second moment, obtaining the space charge change at different moments when the simulated lightning impulse voltage is applied to the DC cable. The present invention is capable of measuring the space charge change at different moments when the simulated lightning impulse voltage is applied to the DC cable.

Description

Technical Field

[0001] The present invention relates to the technical field of high voltage and insulating material electrical insulation testing, and in particular to a method and device for testing space charge changes in DC cable voltage simulated by lightning impulse. Background Art

[0002] With the rapid development of my country's economy and the improvement of people's living standards, electricity demand has increased significantly, placing new demands on the construction and management of my country's power supply companies. High-voltage DC cables, with their high transmission capacity and low operating losses, are widely used in long-distance power transmission systems. XLPE is widely used in high-voltage DC cables due to its excellent insulation properties, high-temperature resistance, and ease of installation and manufacturing.

[0003] The safe operation of high-voltage direct current (HVDC) cable insulation is crucial for ensuring the long-term stable operation of power systems. With the continuous advancement of transmission technology, the voltage level of DC transmission is constantly increasing. This makes it easy for space charge to accumulate within the cable insulation. This accumulation of space charge causes electric field distortion within the cable insulation, significantly increasing the local field strength, inducing partial discharge, electrical treeing, and even causing insulation breakdown. Therefore, to ensure the safe and stable operation of HVDC cables, studying the behavior of space charge under different operating conditions has become a top priority.

[0004] During the actual operation of high-voltage DC cables, circuit breaker operation, lightning impulse transient overvoltage and other situations will cause the high-voltage DC cables to be subjected to pulse voltages, thus forming an operating condition under a DC superimposed pulse composite voltage. Under the DC superimposed pulse composite voltage, it is necessary to study the influence of voltage interaction on the charge transport process, which is of great significance for analyzing the initiation mechanism of electrical trees under composite voltage, suppressing the degradation of insulation electrical trees, and ensuring the safe and stable operation of high-voltage DC cables.

[0005] Currently, the electroacoustic pulse method is commonly used to measure the space charge of insulating media. The principle of this method is: a pulse source applies a high-voltage narrow pulse to the sample, causing the space charge in the medium to produce a small displacement, which is then transmitted to the piezoelectric sensor in the form of sound waves. After being converted into an electrical signal, the space charge density distribution characteristics can be obtained.

[0006] This method has been widely used to measure space charge in DC or AC electric fields, and the measurement of space charge in pulsed electric fields has also gradually attracted the attention of researchers. However, the measurement of space charge under DC superimposed pulse composite voltage has not made significant progress. This is mainly because multiple voltages are applied simultaneously to the specimen under composite voltage, and the multiple branches will interfere with each other. Ensuring electrical isolation between the multiple branches becomes a key factor in this measurement method. At the same time, lightning impulse voltage changes very rapidly. The rising and falling edges of simulated lightning impulse voltage have a width of nanoseconds. Therefore, accurately measuring the space charge distribution at different times along the pulse edge and calculating the change in space charge become key issues in this measurement method. Summary of the Invention

[0007] The purpose of the present invention is to provide a method and device for testing the space charge change of a DC cable voltage under a simulated lightning impulse, which measures the space charge change at different times when a simulated lightning impulse voltage is applied to the DC cable.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] In a first aspect, the present invention provides a method for testing the space charge change of a DC cable voltage by simulating a lightning impulse, comprising:

[0010] Obtaining a space charge distribution obtained after a first voltage source acts on the DC cable; the first voltage source includes a simulated lightning impulse voltage, a high-voltage polarized DC voltage, and a high-frequency high-voltage trigger pulse voltage;

[0011] The spatial charge distribution includes: a spatial charge distribution at a first moment and a spatial charge distribution at a second moment; the spatial charge distribution at the first moment and the spatial charge distribution at the second moment are at the same rising edge action time or falling edge action time of the simulated lightning impulse voltage;

[0012] Obtaining, based on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment, a change in the spatial charge at different moments when the simulated lightning impulse voltage is applied to the DC cable;

[0013] The process of obtaining the space charge distribution is:

[0014] Obtain a first curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on a DC cable, and obtain the rising edge action time of the simulated lightning impulse voltage according to the first curve; obtain a rising edge PEA original signal according to the rising edge action time of the simulated lightning impulse voltage; the rising edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on a DC cable; wherein the rising edge action time of the simulated lightning impulse voltage is used to control each of the high-frequency, high-voltage trigger pulse voltages to correspond to the rising edge of each of the simulated lightning impulse voltages;

[0015] Obtain a second curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on the DC cable, and obtain the falling edge action time of the simulated lightning impulse voltage according to the second curve; obtain a falling edge PEA original signal according to the falling edge action time of the simulated lightning impulse voltage; the falling edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on the DC cable; wherein the falling edge action time of the simulated lightning impulse voltage is used to control each pulse cluster to correspond to the falling edge of each simulated lightning impulse voltage; the pulse cluster includes three high-frequency, high-voltage trigger pulse voltages;

[0016] Signal recovery is performed on the rising edge PEA original signal or the falling edge PEA original signal to obtain spatial charge distribution.

[0017] Optionally, obtaining, based on the space charge distribution at the first moment and the space charge distribution at the second moment, a space charge variation at different moments when the simulated lightning impulse voltage is applied to the DC cable, specifically includes:

[0018] Performing signal recovery on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment respectively to obtain a spatial charge distribution curve at the first moment and a spatial charge distribution curve at the second moment;

[0019] The difference between the spatial charge density parameters at the same position of the spatial charge distribution curve at the first moment and the spatial charge distribution curve at the second moment is calculated to obtain the spatial charge variation at different moments when the simulated lightning impulse voltage is applied to the DC cable.

[0020] In a second aspect, the present invention provides a device for testing the voltage and space charge variation of a DC cable by simulating a lightning impulse, comprising: a computer, a lightning impulse simulation module, a high-voltage polarization DC module, and a high-frequency and high-voltage trigger module;

[0021] The simulated lightning impulse module is used to generate a simulated lightning impulse voltage; the high-voltage polarized DC module is used to generate a high-voltage polarized DC voltage; the high-frequency and high-voltage trigger module is used to generate a high-frequency and high-voltage trigger voltage;

[0022] The computer is used to:

[0023] Obtaining a space charge distribution obtained after a first voltage source acts on the DC cable; the first voltage source includes a simulated lightning impulse voltage, a high-voltage polarized DC voltage, and a high-frequency high-voltage trigger pulse voltage;

[0024] The spatial charge distribution includes: a spatial charge distribution at a first moment and a spatial charge distribution at a second moment; the spatial charge distribution at the first moment and the spatial charge distribution at the second moment are at the same rising edge action time or falling edge action time of the simulated lightning impulse voltage;

[0025] Obtaining, based on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment, a change in the spatial charge at different moments when the simulated lightning impulse voltage is applied to the DC cable;

[0026] The process of obtaining the space charge distribution is:

[0027] Obtain a first curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on a DC cable, and obtain the rising edge action time of the simulated lightning impulse voltage according to the first curve; obtain a rising edge PEA original signal according to the rising edge action time of the simulated lightning impulse voltage; the rising edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on a DC cable; wherein the rising edge action time of the simulated lightning impulse voltage is used to control each of the high-frequency, high-voltage trigger pulse voltages to correspond to the rising edge of each of the simulated lightning impulse voltages;

[0028] Obtain a second curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on the DC cable, and obtain the falling edge action time of the simulated lightning impulse voltage according to the second curve; obtain a falling edge PEA original signal according to the falling edge action time of the simulated lightning impulse voltage; the falling edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on the DC cable; wherein the falling edge action time of the simulated lightning impulse voltage is used to control each pulse cluster to correspond to the falling edge of each simulated lightning impulse voltage; the pulse cluster includes three high-frequency, high-voltage trigger pulse voltages;

[0029] Signal recovery is performed on the rising edge PEA original signal or the falling edge PEA original signal to obtain spatial charge distribution.

[0030] Optionally, the lightning impulse simulation module includes:

[0031] A simulated lightning impulse power supply, a first capacitor and a first resistor are connected in series in sequence; the first capacitor is used to isolate the high-voltage polarized DC voltage, and the first resistor is used to protect the circuit.

[0032] Optionally, the high-voltage polarized DC module includes:

[0033] A high-voltage polarized DC power supply, a second capacitor and a second resistor; the high-voltage polarized DC power supply and the second resistor are connected in series; the second resistor and the second capacitor are connected in parallel, the second capacitor is used to isolate the simulated lightning impulse voltage, and the second resistor is used to protect the circuit.

[0034] Optionally, the high-frequency and high-voltage trigger module includes:

[0035] A high-frequency, high-voltage trigger power supply, a third resistor and a third capacitor; the high-voltage trigger power supply is connected in series with the third capacitor, and the third capacitor and the third resistor are connected in parallel; the third capacitor is used to protect the high-frequency, high-voltage trigger power supply, and the third resistor is used to prevent pulse signal reflection.

[0036] Optionally, the simulated lightning impulse power supply includes: a first signal generator and a standard lightning voltage generating device;

[0037] The first signal generator is used to control the standard lightning voltage generating device to generate the simulated lightning impulse voltage.

[0038] Optionally, it further includes: a second signal generator;

[0039] The second signal generator is connected to the first signal generator and the high-frequency and high-voltage trigger power supply respectively;

[0040] The second signal generator is configured to generate a pulse cluster short square wave signal according to a first set frequency or a second set frequency; the first set frequency is the self-triggering frequency of the second signal generator; and the second set frequency is the triggering frequency of the first signal generator;

[0041] The high-frequency and high-voltage trigger power supply is used to output the rising edge action time of the simulated lightning impulse voltage and the falling edge action time of the simulated lightning impulse voltage according to the pulse cluster short square wave signal.

[0042] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0043] The present invention provides a method and device for testing space charge changes in a DC cable voltage simulated by a lightning impulse. The method comprises: obtaining a space charge distribution obtained after a first voltage source acts on the DC cable; the first voltage source comprises a simulated lightning impulse voltage, a high-voltage polarized DC voltage, and a high-frequency, high-voltage trigger pulse voltage; the space charge distribution comprises a space charge distribution at a first moment and a space charge distribution at a second moment; the space charge distribution at the first moment and the space charge distribution at the second moment are at the time of the rising edge or the falling edge of the same simulated lightning impulse voltage; and based on the space charge distribution at the first moment and the space charge distribution at the second moment, obtaining the space charge change at different moments when the simulated lightning impulse voltage is applied to the DC cable. The present invention is capable of measuring the space charge change at different moments when the simulated lightning impulse voltage is applied to the DC cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 This is a structural diagram of a device for testing the voltage and space charge variation of a DC cable simulating lightning impulses provided in the first embodiment of the present invention;

[0046] Figure 2 A schematic diagram of a space charge test electrode unit model provided in Example 1 of the present invention;

[0047] Figure 3 A schematic diagram of a trigger voltage delay control circuit model provided in Example 1 of the present invention;

[0048] Figure 4 A flow chart of a method for testing space charge changes in DC cable voltage simulated by lightning impulses provided in the second embodiment of the present invention;

[0049] Figure 5 A curve diagram of the simulated lightning impulse voltage provided in the second embodiment of the present invention;

[0050] Figure 6 This is a voltage curve diagram of a method for testing the space charge change of DC cable voltage during a simulated lightning impulse provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] The purpose of the present invention is to provide a method and device for testing space charge changes in DC cable voltage under simulated lightning impulse, which can measure the space charge changes at different times when the simulated lightning impulse voltage is applied to the DC cable.

[0053] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] Figure 1 This is a structural diagram of a device for testing the voltage and space charge changes of a DC cable simulating lightning impulses provided in the first embodiment of the present invention.

[0055] like Figure 1 As shown, the first embodiment of the present invention provides a device for testing the voltage and space charge change of a DC cable by simulating lightning impulse, comprising: a computer, a lightning impulse simulation module, a high-voltage polarized DC module, and a high-frequency and high-voltage trigger module.

[0056] The simulated lightning impulse module is used to generate a simulated lightning impulse voltage; the high-voltage polarized DC module is used to generate a high-voltage polarized DC voltage; and the high-frequency and high-voltage trigger module is used to generate a high-frequency and high-voltage trigger voltage.

[0057] The computer is used to:

[0058] Obtain a space charge distribution obtained after a first voltage source acts on a DC cable; the first voltage source includes a simulated lightning impulse voltage, a high-voltage polarized DC voltage, and a high-frequency, high-voltage trigger pulse voltage.

[0059] The spatial charge distribution includes: a spatial charge distribution at a first moment and a spatial charge distribution at a second moment; the spatial charge distribution at the first moment and the spatial charge distribution at the second moment are at the rising edge action time or the falling edge action time of the same simulated lightning impulse voltage.

[0060] According to the spatial charge distribution at the first moment and the spatial charge distribution at the second moment, a change in spatial charge at different moments when the simulated lightning impulse voltage is applied to the DC cable is obtained.

[0061] The process of obtaining the space charge distribution is:

[0062] Obtain a first curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on a DC cable, and obtain the rising edge action time of the simulated lightning impulse voltage according to the first curve; obtain a rising edge PEA original signal according to the rising edge action time of the simulated lightning impulse voltage; the rising edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage and the multiple high-frequency and high-voltage trigger pulse voltages act on the DC cable; wherein the rising edge action time of the simulated lightning impulse voltage is used to control each of the high-frequency and high-voltage trigger pulse voltages to correspond to the rising edge of each of the simulated lightning impulse voltages.

[0063] A second curve is obtained after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on the DC cable, and the falling edge action time of the simulated lightning impulse voltage is obtained according to the second curve; a falling edge PEA original signal is obtained according to the falling edge action time of the simulated lightning impulse voltage; the falling edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage and the high-frequency and high-voltage trigger pulse voltages act on the DC cable; wherein the falling edge action time of the simulated lightning impulse voltage is used to control each pulse cluster to correspond to the falling edge of each simulated lightning impulse voltage; the pulse cluster includes three high-frequency and high-voltage trigger pulse voltages.

[0064] Signal recovery is performed on the rising edge PEA original signal or the falling edge PEA original signal to obtain spatial charge distribution.

[0065] Specifically, the device for testing space charge changes in DC cable voltage caused by simulating lightning impulses provided in the first embodiment further includes a space charge testing module.

[0066] The space charge test module includes an upper electrode, a sample, a lower electrode, and a piezoelectric sensor. The sample is placed between the upper and lower electrodes. The upper electrode is connected to the lightning impulse simulation module, the high-voltage polarization DC module, and the high-frequency and high-voltage trigger module. The piezoelectric sensor is a PVDF piezoelectric sensor.

[0067] Figure 2 This is a schematic diagram of the space charge test electrode unit model provided in Example 1 of the present invention.

[0068] like Figure 2As shown, the electrode unit structure for space charge testing under composite voltage consists of an upper electrode and a lower electrode, with the sample placed between the electrodes. Due to the continuous application of the pulse voltage, the upper electrode will discharge, resulting in an inability to continuously increase the voltage, affecting the test results. Silicone rubber must be coated on the surface of the electrode and the sample and allowed to cure at room temperature to ensure that the composite voltage is stably applied to the sample. The composite voltage includes: simulated lightning impulse voltage, high-voltage polarization DC voltage, and high-frequency high-voltage trigger voltage.

[0069] The epoxy resin ring is primarily used to secure the silicone rubber's shape, preventing the liquid silicone rubber from flowing outside the XLPE specimen, which could cause unevenness and affect test results. SC layer (semi-conductive layer): During testing, a semi-conductive layer is typically placed between the upper electrode and the specimen's upper surface to improve the acoustic impedance matching of the contact surface. This semi-conductive layer should have a certain curvature along its surface to prevent edge discharges when applying high-voltage polarized DC voltage and simulated lightning impulse voltage.

[0070] Specifically, the lightning impulse simulation module includes:

[0071] A simulated lightning impulse power supply, a first capacitor C1 and a first resistor R1 are connected in series in sequence; the first capacitor C1 is used to isolate the high-voltage polarized DC voltage, and the first resistor R1 is used to protect the circuit.

[0072] The simulated lightning impulse voltage module is a high-pass filter circuit, which couples the simulated lightning impulse voltage to the sample through the first capacitor C1 and isolates the DC voltage to ensure that the simulated lightning impulse voltage is not interfered by the DC voltage.

[0073] Specifically, the high-voltage polarized DC module includes:

[0074] A high-voltage polarized DC power supply, a second capacitor C2, and a second resistor R2; the high-voltage polarized DC power supply and the second resistor R2 are connected in series; the second resistor R2 and the second capacitor C2 are connected in parallel, the second capacitor C2 is used to isolate the simulated lightning impulse voltage, and the second resistor R2 is used to protect the circuit.

[0075] The cutoff frequency f=1 / 2πRC of the high-voltage polarized DC module is much greater than the frequency of the simulated lightning impulse voltage, ensuring that the DC voltage effectively acts on the sample while ensuring that the low-frequency simulated lightning impulse voltage does not interfere with the high-voltage polarized DC power supply.

[0076] Specifically, the high-frequency and high-voltage trigger module includes:

[0077] A high-frequency, high-voltage trigger power supply, a third resistor R3, and a third capacitor C3; the high-voltage trigger power supply is connected in series with the third capacitor C3, and the third capacitor C3 and the third resistor R3 are connected in parallel; the third capacitor C3 is used to protect the high-frequency, high-voltage trigger power supply, and the third resistor R3 is used to prevent pulse signal reflection.

[0078] The third capacitor C3 of the high-frequency, high-voltage trigger module exhibits high impedance for the simulated lightning impulse voltage, but low impedance for the high-frequency, high-voltage trigger voltage. This protects the high-frequency, high-voltage trigger power supply while ensuring that both the high-frequency, high-voltage trigger voltage and the simulated lightning impulse voltage are applied to the specimen simultaneously. The third resistor R3 is 50 ohms.

[0079] Specifically, the simulated lightning impulse power supply includes: a first signal generator and a standard lightning voltage generating device.

[0080] The first signal generator is used to control the standard lightning voltage generator to generate the simulated lightning impulse voltage. The high-frequency, high-voltage trigger module is designed based on a 16-stage Marx circuit of an avalanche transistor. It achieves a high-frequency, high-voltage trigger voltage output with a frequency of 500kHz, a half-width pulse of 15ns, and a pulse amplitude of 1.5kV. It can accurately trigger different positions on the rising or falling edge of the simulated lightning impulse voltage. The trigger voltage delay control circuit synchronizes the phase of the high-frequency, high-voltage trigger voltage with the simulated lightning impulse voltage, and the trigger delay time can be arbitrarily set.

[0081] Figure 3 This is a schematic diagram of a trigger voltage delay control circuit model provided in Example 1 of the present invention.

[0082] like Figure 3 As shown, the simulated lightning impulse voltage consists of a first signal generator controlling a standard lightning voltage generator. To ensure synchronization between the simulated lightning impulse voltage and the high-frequency, high-voltage trigger voltage, the output signal of the first signal generator serves as the external input signal for the high-frequency, high-voltage trigger voltage. At this time, the second signal generator selects the burst trigger mode, outputting a cluster of short square wave signals corresponding to the starting position of the rising or falling edge of the simulated lightning impulse voltage, thereby achieving phase synchronization. This cluster of short square wave signals triggers the Marx circuit, which outputs a high-frequency, high-voltage trigger voltage that acts on the specimen, achieving multiple, continuous triggering at a fixed phase. The number of square waves in the cluster of short square wave signals is adjusted by setting the number of cycles, thereby adjusting the number of triggers at a fixed phase. The high-frequency, high-voltage trigger voltage acting on the specimen causes the internal space charge of the specimen to vibrate, generating an acoustic wave signal. The piezoelectric sensor receives the acoustic wave signal and converts it into an electrical signal.

[0083] Specifically, the device for testing the space charge change of DC cable voltage during a simulated lightning impulse provided in the first embodiment further includes an amplifier and an oscilloscope.

[0084] The amplifier is connected to the piezoelectric sensor and is used to amplify and process the electrical signal.

[0085] The oscilloscope is connected to the amplifier and is used to receive the electrical signal and display the space charge.

[0086] Specifically, the device for testing the space charge change of a DC cable voltage caused by a simulated lightning impulse provided in the first embodiment further includes: a second signal generator.

[0087] The second signal generator is connected to the first signal generator and the high-frequency and high-voltage trigger power supply respectively.

[0088] The second signal generator is used to generate a pulse cluster short square wave signal according to a first set frequency or a second set frequency; the first set frequency is the self-triggering frequency of the second signal generator; the second set frequency is the triggering frequency of the first signal generator.

[0089] The high-frequency and high-voltage trigger power supply is used to output the rising edge action time of the simulated lightning impulse voltage and the falling edge action time of the simulated lightning impulse voltage according to the pulse cluster short square wave signal.

[0090] Figure 4 This is a flow chart of a method for testing space charge changes in DC cable voltage during simulated lightning strikes, provided in the second embodiment of the present invention.

[0091] like Figure 4 As shown, a method for testing space charge changes in DC cable voltage during a simulated lightning impulse is provided in the second embodiment of the present invention, comprising:

[0092] Step 100: Obtain a space charge distribution obtained after a first voltage source acts on a DC cable; the first voltage source includes a simulated lightning impulse voltage, a high-voltage polarized DC voltage, and a high-frequency, high-voltage trigger pulse voltage. The space charge distribution includes a space charge distribution at a first moment and a space charge distribution at a second moment; the space charge distribution at the first moment and the space charge distribution at the second moment are at the same time of the rising edge or falling edge of the simulated lightning impulse voltage.

[0093] Step 200: Obtaining space charge variations at different times when a simulated lightning impulse voltage is applied to a DC cable based on the space charge distribution at the first time and the space charge distribution at the second time.

[0094] The process of obtaining the space charge distribution is:

[0095] Obtain a first curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on a DC cable, and obtain the rising edge action time of the simulated lightning impulse voltage according to the first curve; obtain a rising edge PEA original signal according to the rising edge action time of the simulated lightning impulse voltage; the rising edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage and the multiple high-frequency and high-voltage trigger pulse voltages act on the DC cable; wherein the rising edge action time of the simulated lightning impulse voltage is used to control each of the high-frequency and high-voltage trigger pulse voltages to correspond to the rising edge of each of the simulated lightning impulse voltages.

[0096] A second curve is obtained after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on the DC cable, and the falling edge action time of the simulated lightning impulse voltage is obtained according to the second curve; a falling edge PEA original signal is obtained according to the falling edge action time of the simulated lightning impulse voltage; the falling edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage and the high-frequency and high-voltage trigger pulse voltages act on the DC cable; wherein the falling edge action time of the simulated lightning impulse voltage is used to control each pulse cluster to correspond to the falling edge of each simulated lightning impulse voltage; the pulse cluster includes three high-frequency and high-voltage trigger pulse voltages.

[0097] Signal recovery is performed on the rising edge PEA original signal or the falling edge PEA original signal to obtain spatial charge distribution.

[0098] Specifically, obtaining the space charge variation at different times when the simulated lightning impulse voltage is applied to the DC cable according to the space charge distribution at the first moment and the space charge distribution at the second moment specifically includes:

[0099] Signal recovery is performed on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment respectively to obtain a spatial charge distribution curve at the first moment and a spatial charge distribution curve at the second moment.

[0100] The difference between the spatial charge density parameters at the same position of the spatial charge distribution curve at the first moment and the spatial charge distribution curve at the second moment is calculated to obtain the spatial charge variation at different moments when the simulated lightning impulse voltage is applied to the DC cable.

[0101] Figure 5 This is a curve diagram of the simulated lightning impulse voltage provided in the second embodiment of the present invention.

[0102] like Figure 5As shown in Figure 1, the polarity of the simulated lightning impulse voltage may be the same as or opposite to the polarity of the high-voltage polarized DC voltage. For the simulated lightning impulse voltage of the two polarities, the rising edge measurement method is the same. Figure 5 (a) is the same polarity curve of the simulated lightning impulse voltage; Figure 5 (b) is the reverse polarity curve of the simulated lightning impulse voltage.

[0103] like Figure 5 As shown in (a), due to the 1.2μs rise time of the simulated lightning impulse voltage and the minimum 2μs interval between applied high-frequency, high-voltage trigger voltages, it is impossible to apply more than one high-frequency, high-voltage trigger voltage to excite the PEA signal during a single rising edge. However, due to the requirements of the PEA space charge detection method and the signal-to-noise ratio, at least 50 or more original PEA signals must be acquired before the signal-to-noise ratio can be increased to the required level using averaging.

[0104] like Figure 5 As shown in (b), the simulated lightning impulse voltage's falling edge duration is 1.2μs, while the applied high-frequency, high-voltage trigger voltage has a minimum trigger interval of 2μs. Therefore, it's impossible to apply more than one high-frequency, high-voltage trigger voltage on a single falling edge to excite the PEA signal. However, due to the requirements of the PEA space charge detection method and the signal-to-noise ratio, at least 50 or more raw PEA signals must be acquired before the signal-to-noise ratio can be increased to the required level using averaging.

[0105] Figure 6 This is a voltage curve diagram of a method for testing the space charge change of DC cable voltage during a simulated lightning impulse provided in the second embodiment of the present invention.

[0106] like Figure 6 As shown, a signal trigger synchronization signal for the simulated lightning impulse voltage is obtained. This is the pulse signal output by a standard lightning impulse power supply at the moment the simulated lightning impulse voltage is applied. This pulse signal is connected to a second signal generator. A delay between 0 and 1.2 μs is set based on the rising edge moment to be measured, and the number of repetitive pulses of the high-frequency, high-voltage trigger voltage in single-burst mode is set to 1. This allows the nanosecond pulse trigger parameters to be set, with t1 being the first rising edge moment and t2 being the second rising edge moment.

[0107] Setting the oscilloscope's average number of acquisitions to n (≥50) allows for n signal acquisitions. After applying n lightning impulse voltages, a set of PEA measurement signals is obtained.

[0108] The simulated lightning impulse voltage has a falling edge time of 50μs. Using the rising edge method, space charge measurements can be performed at any time along the falling edge over n cycles. Furthermore, to shorten the time required for a single measurement, multiple triggers can be performed on a single falling edge. For example, after setting an appropriate trigger delay, the number of repetitive pulses of the high-frequency, high-voltage trigger voltage in single-burst mode can be set to 3. In this case, a space charge measurement can be performed within 4μs on a simulated lightning impulse voltage falling edge. Fifty sets of PEA raw signals can be obtained at 17 lightning impulse voltages, yielding a single set of PEA measurement signals. T3 represents the first moment along the falling edge, and T4 represents the second moment along the falling edge.

[0109] The present invention provides a method and device for testing the space charge change of a DC cable voltage by simulating a lightning impulse, which has the following beneficial effects:

[0110] 1. The present invention obtains the spatial charge variation at different moments when the simulated lightning impulse voltage is applied to the DC cable through the spatial charge distribution at the first moment and the spatial charge distribution at the second moment.

[0111] 2. Electrical isolation between each branch is achieved through the lightning impulse simulation module, high-voltage polarized DC module and high-frequency high-voltage trigger module. While avoiding mutual interference between the various voltage sources, it ensures that the simulated lightning impulse voltage, high-voltage polarized DC voltage and high-frequency high-voltage trigger voltage are stably applied to the cable insulation sample.

[0112] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0113] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for testing the space charge change of DC cable voltage by simulating lightning impulse, characterized in that: include: Obtaining a space charge distribution obtained after the first voltage source acts on the DC cable; The first voltage source includes a simulated lightning impulse voltage, a high-voltage polarized DC voltage, and a high-frequency high-voltage trigger pulse voltage; The spatial charge distribution includes: a spatial charge distribution at a first moment and a spatial charge distribution at a second moment; the spatial charge distribution at the first moment and the spatial charge distribution at the second moment are at the same rising edge action time or falling edge action time of the simulated lightning impulse voltage; Obtaining, based on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment, a change in the spatial charge at different moments when the simulated lightning impulse voltage is applied to the DC cable; The process of obtaining the space charge distribution is: Obtain a first curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on a DC cable, and obtain the rising edge action time of the simulated lightning impulse voltage according to the first curve; obtain a rising edge PEA original signal according to the rising edge action time of the simulated lightning impulse voltage; the rising edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on a DC cable; wherein the rising edge action time of the simulated lightning impulse voltage is used to control each of the high-frequency, high-voltage trigger pulse voltages to correspond to the rising edge of each of the simulated lightning impulse voltages; Obtain a second curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on the DC cable, and obtain the falling edge action time of the simulated lightning impulse voltage according to the second curve; obtain a falling edge PEA original signal according to the falling edge action time of the simulated lightning impulse voltage; the falling edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on the DC cable; wherein the falling edge action time of the simulated lightning impulse voltage is used to control each pulse cluster to correspond to the falling edge of each simulated lightning impulse voltage; the pulse cluster includes three high-frequency, high-voltage trigger pulse voltages; Signal recovery is performed on the rising edge PEA original signal or the falling edge PEA original signal to obtain spatial charge distribution.

2. The method for testing the space charge change of DC cable voltage under simulated lightning impulse according to claim 1, characterized in that: The obtaining, based on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment, a spatial charge variation when the simulated lightning impulse voltage is applied to the DC cable at different moments specifically includes: Performing signal recovery on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment respectively to obtain a spatial charge distribution curve at the first moment and a spatial charge distribution curve at the second moment; The difference between the spatial charge density parameters at the same position of the spatial charge distribution curve at the first moment and the spatial charge distribution curve at the second moment is calculated to obtain the spatial charge variation at different moments when the simulated lightning impulse voltage is applied to the DC cable.

3. A device for testing the voltage and space charge change of a DC cable by simulating lightning impulse, characterized in that: include: Computer, lightning impulse simulation module, high-voltage polarization DC module and high-frequency high-voltage trigger module; The simulated lightning impulse module is used to generate a simulated lightning impulse voltage; the high-voltage polarized DC module is used to generate a high-voltage polarized DC voltage; the high-frequency and high-voltage trigger module is used to generate a high-frequency and high-voltage trigger voltage; The computer is used to: Obtaining a space charge distribution obtained after a first voltage source acts on the DC cable; the first voltage source includes a simulated lightning impulse voltage, a high-voltage polarized DC voltage, and a high-frequency high-voltage trigger pulse voltage; The spatial charge distribution includes: a spatial charge distribution at a first moment and a spatial charge distribution at a second moment; the spatial charge distribution at the first moment and the spatial charge distribution at the second moment are at the same rising edge action time or falling edge action time of the simulated lightning impulse voltage; Obtaining, based on the spatial charge distribution at the first moment and the spatial charge distribution at the second moment, a change in the spatial charge at different moments when the simulated lightning impulse voltage is applied to the DC cable; The process of obtaining the space charge distribution is: Obtain a first curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on a DC cable, and obtain the rising edge action time of the simulated lightning impulse voltage according to the first curve; obtain a rising edge PEA original signal according to the rising edge action time of the simulated lightning impulse voltage; the rising edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on a DC cable; wherein the rising edge action time of the simulated lightning impulse voltage is used to control each of the high-frequency, high-voltage trigger pulse voltages to correspond to the rising edge of each of the simulated lightning impulse voltages; Obtain a second curve after multiple simulated lightning impulse voltages and the high-voltage polarized DC voltage act on the DC cable, and obtain the falling edge action time of the simulated lightning impulse voltage according to the second curve; obtain a falling edge PEA original signal according to the falling edge action time of the simulated lightning impulse voltage; the falling edge PEA original signal is a signal obtained after multiple simulated lightning impulse voltages, the high-voltage polarized DC voltage, and multiple high-frequency, high-voltage trigger pulse voltages act on the DC cable; wherein the falling edge action time of the simulated lightning impulse voltage is used to control each pulse cluster to correspond to the falling edge of each simulated lightning impulse voltage; the pulse cluster includes three high-frequency, high-voltage trigger pulse voltages; Signal recovery is performed on the rising edge PEA original signal or the falling edge PEA original signal to obtain spatial charge distribution.

4. The device for testing the voltage and space charge change of a DC cable simulating a lightning impulse according to claim 3, characterized in that: The simulated lightning impulse module comprises: a simulated lightning impulse power supply, a first capacitor and a first resistor connected in series in sequence; The first capacitor is used to isolate the high-voltage polarized DC voltage, and the first resistor is used to protect the circuit.

5. The device for testing the voltage and space charge change of a DC cable simulating lightning impulse according to claim 3, characterized in that: The high-voltage polarized DC module includes: a high-voltage polarized DC power supply, a second capacitor and a second resistor; The high-voltage polarized DC power supply and the second resistor are connected in series; the second resistor and the second capacitor are connected in parallel, the second capacitor is used to isolate the simulated lightning impulse voltage, and the second resistor is used to protect the circuit.

6. The device for testing the voltage and space charge change of a DC cable simulating lightning impulse according to claim 3, characterized in that: The high-frequency and high-voltage trigger module includes: a high-frequency and high-voltage trigger power supply, a third resistor and a third capacitor; The high-voltage trigger power supply is connected in series with the third capacitor, and the third capacitor and the third resistor are connected in parallel; the third capacitor is used to protect the high-frequency high-voltage trigger power supply, and the third resistor is used to prevent pulse signal reflection.

7. The device for testing the voltage and space charge change of a DC cable simulating lightning impulse according to claim 4, characterized in that: The simulated lightning impulse power supply includes: a first signal generator and a standard lightning voltage generating device; The first signal generator is used to control the standard lightning voltage generating device to generate the simulated lightning impulse voltage.

8. The device for testing the voltage and space charge change of a DC cable simulating lightning impulse according to claim 7, characterized in that: Also includes: a second signal generator; The second signal generator is connected to the first signal generator and the high-frequency and high-voltage trigger power supply respectively; The second signal generator is used to generate a pulse cluster short square wave signal according to a first set frequency or a second set frequency; the first set frequency is the self-triggering frequency of the second signal generator; the second set frequency is the triggering frequency of the first signal generator; The high-frequency and high-voltage trigger power supply is used to output the rising edge action time of the simulated lightning impulse voltage and the falling edge action time of the simulated lightning impulse voltage according to the pulse cluster short square wave signal.

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