Partial discharge transient volt-ampere signal joint detection method and device

Abstract

The invention relates to a partial discharge transient volt-ampere signal joint detection method and device. The method comprises the following steps: collecting a transient voltage signal and a pulse current signal on a cable shielding layer; performing signal processing on the transient voltage signal and the pulse current signal, and extracting characteristic parameters, wherein the characteristic parameters comprise voltage waveform polarity, current waveform polarity, voltage waveform duration, current waveform duration, waveform similarity coefficient and time difference of occurrence of voltage and current waveforms; and identifying whether partial discharge pulses are generated on the cable shielding layer according to the extracted characteristic parameters. According to the invention, the partial discharge signal can be effectively detected.

Description

Technical Field

[0001] The invention relates to the technical field of partial discharge detection in distribution networks, and in particular to a method and device for combined detection of transient volt-ampere signals of partial discharge. Background Art

[0002] When the insulation of electrical equipment is damaged or defective, partial discharge will occur. Therefore, effective detection of partial discharge signals is of great significance for evaluating the insulation condition of electrical equipment and maintaining the stable operation of electrical equipment. However, the on-site detection environment is very complex. Electrical equipment is often affected by strong electromagnetic fields such as communications. The measured partial discharge signals often contain various interferences, and even the real partial discharge signals will be submerged. Therefore, effectively suppressing the background noise of partial discharge signals is a key step in obtaining pure partial discharge signals. Narrowband interference and white noise are common types of interference in on-site monitoring. Most anti-interference methods are also mainly aimed at suppressing these two types of noise. Among them, the Fourier transform threshold denoising method is mainly aimed at suppressing narrowband interference, and the empirical mode decomposition denoising method and the wavelet transform threshold denoising method are mainly aimed at suppressing white noise. Although these algorithms can suppress interference, the signal waveform after removing the interference is severely distorted and important information is lost. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method and device for joint detection of partial discharge transient volt-ampere signals, which can effectively detect partial discharge signals.

[0004] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for joint detection of transient volt-ampere signals of partial discharge, comprising the following steps:

[0005] Collect transient voltage signals and pulse current signals on the cable shielding layer;

[0006] Extracting characteristic parameters after performing signal processing on the transient voltage signal and the pulse current signal respectively, wherein the characteristic parameters include voltage waveform polarity, current waveform polarity, voltage waveform duration, current waveform duration, waveform similarity coefficient, and time difference between voltage and current waveforms;

[0007] Whether partial discharge pulses are generated on the cable shielding layer is identified based on the extracted characteristic parameters.

[0008] Further, the step of identifying whether a partial discharge pulse is generated on the cable shielding layer according to the extracted characteristic parameters includes:

[0009] Calculating the waveform similarity of the transient voltage signal and the pulse current signal according to the waveform similarity coefficient;

[0010] If the polarity of the voltage waveform is the same as that of the current waveform, and the waveform similarity is greater than the similarity threshold, and the duration of the voltage waveform and the duration of the current waveform are both less than the duration threshold, and the time difference between the voltage and current waveforms is less than the time difference threshold, then it is determined that a partial discharge pulse has been generated on the cable shielding layer, otherwise it is determined to be an interference signal.

[0011] Furthermore, it also includes:

[0012] If it is determined to be an interference signal, the method returns to the step of collecting the transient voltage signal and the pulse current signal on the cable shielding layer.

[0013] Furthermore, the corresponding signal processing of the transient voltage signal and the pulse current signal is performed by filtering and amplifying the transient voltage signal and the pulse current signal and converting them into digital signals.

[0014] The present invention also provides a partial discharge transient volt-ampere signal joint detection device, comprising:

[0015] case;

[0016] Voltage signal probe, used to detect transient voltage signals on the cable shielding layer;

[0017] Current signal probe, used to detect pulse current signal on cable shielding layer;

[0018] The circuit board assembly is placed in the shell and is used to extract characteristic parameters after processing the transient voltage signal and the pulse current signal respectively, and to identify whether a partial discharge pulse is generated on the cable shielding layer according to the extracted characteristic parameters.

[0019] Furthermore, the circuit board assembly includes:

[0020] A first filtering and amplifying circuit, used for filtering and then amplifying the transient voltage signal;

[0021] A second filtering and amplifying circuit, used for filtering and then amplifying the pulse current signal;

[0022] An analog-to-digital conversion circuit, used for performing analog-to-digital conversion on the amplified transient voltage signal and the pulse current signal to obtain transient voltage data and pulse current data;

[0023] The core processing unit is used to extract the characteristics of the transient voltage data and the pulse current data to obtain characteristic parameters, and then determine whether the obtained characteristic parameters meet the set conditions. If so, it is considered that a partial discharge pulse is generated on the cable shielding layer.

[0024] Furthermore, the characteristic parameters include voltage waveform polarity, current waveform polarity, voltage waveform duration, current waveform duration, waveform similarity coefficient, and time difference between voltage and current waveforms.

[0025] Furthermore, the determining whether the obtained characteristic parameters meet the set conditions, if so, it is considered that a partial discharge pulse is generated on the cable shielding layer, includes:

[0026] Calculating the waveform similarity of the transient voltage signal and the pulse current signal according to the waveform similarity coefficient;

[0027] If the polarity of the voltage waveform is the same as that of the current waveform, and the waveform similarity is greater than the similarity threshold, and the voltage waveform duration and the current waveform duration are both less than the duration threshold, and the time difference between the voltage and current waveforms is less than the time difference threshold, it is determined that a partial discharge pulse has been generated on the cable shielding layer.

[0028] Furthermore, the first filtering and amplifying circuit includes a first capacitor, a first resistor, a second capacitor, a first amplifier, a first diode, and a second resistor; the first end of the first capacitor is connected to the voltage signal probe, the second end of the first capacitor is connected to the first end of the first resistor, the second end of the first resistor is respectively connected to the first end of the second capacitor and the positive input end of the first amplifier, the negative input end of the first amplifier is respectively connected to the first end of the second resistor and the output end of the first diode, the second end of the second resistor is connected to the power supply VCC, and the second end of the second capacitor and the input end of the first diode are grounded.

[0029] Furthermore, the second filtering and amplifying circuit includes a third capacitor, a third resistor, a fourth capacitor, a second amplifier, a second diode, and a fourth resistor; the first end of the third capacitor is connected to the current signal probe, the second end of the third capacitor is connected to the first end of the third resistor, the second end of the third resistor is respectively connected to the first end of the fourth capacitor and the positive input end of the second amplifier, the negative input end of the second amplifier is respectively connected to the first end of the fourth resistor and the output end of the second diode, the second end of the fourth resistor is connected to the power supply VCC, and the second end of the fourth capacitor and the input end of the second diode are grounded.

[0030] Beneficial Effects

[0031] Due to the adoption of the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention utilizes the characteristic that the partial discharge signal generated inside the cable and other equipment will simultaneously generate a transient voltage signal and a pulse current signal to identify the partial discharge pulse and interference. Compared with the existing traditional partial discharge anti-interference method, the signals compared with each other originate from the same signal, so the signal correlation is greater and the anti-interference ability is stronger; the signal acquisition and processing of the present invention can be realized by low-power circuits, so that the overall power consumption of the device is extremely low, and disposable lithium batteries can be used for about 10 years of normal operation, which is particularly suitable for use in environments where energy is difficult to obtain, such as distribution cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of a first embodiment of the present invention;

[0033] Figure 2 is a device structure diagram of a second embodiment of the present invention;

[0034] Figure 3 is a circuit diagram of a second embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0036] The internal partial discharge signal of cables and other equipment generally generates both transient ground voltage signal and discharge pulse current signal, while external interference generally only generates one of the signals. The transient ground voltage signal and the discharge pulse current signal appear almost simultaneously, with a time difference of less than a very small period of time, such as 1 microsecond; the transient ground voltage signal and the discharge pulse current signal each last for a very short time, such as 2 microseconds; the first jump direction of the transient ground voltage signal and the discharge pulse current signal is the same, both are rising or falling edges; the envelope similarity of the transient ground voltage signal and the discharge pulse current signal waveform is relatively high, both are quasi-exponential decay waveforms; based on the above situations and differences, the transient volt-ampere joint detection and identification based on the transient ground voltage signal and the discharge pulse current signal can distinguish the partial discharge signal of cables and other equipment from the interference model, and then accurately identify the partial discharge signal of cables and other equipment, thereby improving the detection reliability of partial discharge.

[0037] The first embodiment of the present invention relates to a method for joint detection of partial discharge transient volt-ampere signals, such as Figure 1 As shown, the following steps are included:

[0038] Collect transient voltage signals and pulse current signals on the cable shielding layer;

[0039] Extracting characteristic parameters after performing signal processing on the transient voltage signal and the pulse current signal respectively, wherein the characteristic parameters include voltage waveform polarity, current waveform polarity, voltage waveform duration, current waveform duration, waveform similarity coefficient, and time difference between the voltage and current waveforms;

[0040] Whether partial discharge pulses are generated on the cable shielding layer is identified based on the extracted characteristic parameters.

[0041] Each step is further described below.

[0042] Step 1: Under normal circumstances, the system obtains the voltage and current pulse signals generated by the discharge through the transient voltage signal conditioning circuit and the high-frequency CT signal circuit, and sends the signals to the high-speed A / D for analog-to-digital conversion after amplification and filtering. The analog-to-digital conversion rate is higher than 500Msps.

[0043] Step 2: Extract the data 5 microseconds before the sampling point as the research object, perform feature extraction on the two waveform data collected, and extract their waveform polarity Pa, waveform similarity coefficient S, waveform duration Tc, waveform appearance time difference Td and other parameters respectively.

[0044] Step three, compare the features of the two extracted transient signals respectively, and adopt the one-vote veto principle: when the polarity VPa of the transient ground voltage waveform and the polarity of the current pulse CPa are the same; the similarity of the transient ground voltage waveform and the current pulse is greater than 0.9; the duration VTc of the transient ground voltage waveform and the duration CTc of the current pulse are both less than 2 microseconds (us); the difference between the appearance time of the transient ground voltage waveform and the appearance time of the current pulse is less than 1 microsecond, if all these conditions are met, the pulse is determined to be a partial discharge pulse, and the maximum amplitude of the two signals is recorded as the partial discharge signal amplitude of the corresponding channel, otherwise it is determined to be an interference signal and abandoned.

[0045] Step 4: If it is judged to be a partial discharge pulse, 5 microseconds of data are collected continuously again and then the processing of steps 2 and 3 is performed. If it is judged to be an interference signal, the processing of steps 2 and 3 is performed again during the next collection.

[0046] The second embodiment of the present invention relates to a partial discharge transient volt-ampere signal joint detection device, such as Figure 2 As shown, it includes a housing 1, a transient voltage signal probe 2, a high-frequency pulse current probe 3, a circuit board assembly 4, a battery 5, and a wireless communication antenna 6.

[0047] Among them, Figure 3As shown, the transient ground voltage signal probe (TEVP), C1, R1, C2, R2, D1 and U1A constitute a transient ground voltage signal acquisition, amplification and processing circuit. When a partial discharge occurs inside the cable, a transient ground voltage signal will be generated on the cable shielding layer. After the probe is coupled to the signal, it is processed by the filter circuit composed of C1, R1 and C2 and sent to the positive pole of the U1A amplifier for tracking amplification to achieve impedance conversion. The amplified signal is sent to the high-speed A / D sampling circuit for further amplification and analog-to-digital conversion.

[0048] High-frequency current pulse probe (HFCT), C3, R3, C4, R4, D2 and U1B constitute a current pulse signal acquisition, amplification and processing circuit. When a partial discharge occurs in the cable, a corresponding pulse current will flow through the cable shielding layer. After the HFCT probe detects the signal, it is processed by the filter circuit composed of C3, R3 and C4 and sent to the positive pole of the U1B amplifier for tracking amplification. The amplified signal is sent to the high-speed A / D sampling circuit for analog-to-digital conversion.

[0049] Rt is a thermistor. After internal conversion inside the core processing unit, the temperature value can be calculated based on the resistance value of the thermistor.

[0050] The core processing unit extracts the data 5 microseconds before the sampling point as the research object, calculates the characteristics of the two waveform data collected, and extracts their waveform polarity Pa, waveform similarity coefficient S, waveform duration Tc, waveform appearance time difference Td and other parameters.

[0051] The core processing unit compares these characteristic parameters. When the polarity VPa of the transient voltage waveform is the same as the polarity of the current pulse CPa; the similarity between the transient voltage waveform and the current pulse is greater than 0.9; the duration VTc of the transient voltage waveform and the duration CTc of the current pulse are both less than 2 microseconds (us); the difference between the appearance time of the transient voltage waveform and the appearance time of the current pulse is less than 1 microsecond, if all these conditions are met, the pulse is determined to be a partial discharge pulse, and the maximum amplitude of the two signals is recorded as the partial discharge signal amplitude of the corresponding channel, otherwise it is determined to be an interference signal and abandoned. The specific steps are as follows:

[0052] Step 1: Under normal circumstances, the sensor obtains the voltage and current pulse signals generated by the discharge through the transient voltage signal conditioning circuit and the high-frequency CT signal circuit, respectively, and sends the signals to the high-speed A / D for analog-to-digital conversion after amplification and filtering. The analog-to-digital conversion rate is higher than 500Msps.

[0053] Step 2, extract the data 5 microseconds before the sampling point as the research object, extract the features of the two waveform data collected, and extract their waveform polarity Pa, waveform similarity coefficient S, waveform duration Tc, waveform appearance time difference Td and other parameters respectively.

[0054] Step 3, compare the features of the two extracted transient signals respectively, and adopt the one-vote veto principle: when the polarity VPa of the transient ground voltage waveform and the polarity of the current pulse CPa are the same; the similarity of the transient ground voltage waveform and the current pulse is greater than 0.9; the duration VTc of the transient ground voltage waveform and the duration CTc of the current pulse are both less than 2 microseconds (us); the difference between the appearance time of the transient ground voltage waveform and the appearance time of the current pulse is less than 1 microsecond, if all these conditions are met, the pulse is determined to be a partial discharge pulse, and the maximum amplitude of the two signals is recorded as the partial discharge signal amplitude of the corresponding channel, otherwise it is determined to be an interference signal and abandoned.

[0055] Step 4: If it is judged to be a partial discharge pulse, the data is collected continuously for 5 microseconds again and then the processing of steps 2 and 3 is performed. If it is judged to be an interference signal, the processing of steps 2 and 3 is performed again during the next collection.

Claims

1. A method for joint detection of transient voltammetric signals of partial discharge, characterized in that: The following steps are involved: Collect transient voltage signals and pulse current signals on the cable shielding layer; Extracting characteristic parameters after performing signal processing on the transient voltage signal and the pulse current signal respectively, wherein the characteristic parameters include voltage waveform polarity, current waveform polarity, voltage waveform duration, current waveform duration, waveform similarity coefficient, and time difference between voltage and current waveforms; Whether partial discharge pulses are generated on the cable shielding layer is identified based on the extracted characteristic parameters.

2. The method according to claim 1, characterized in that The step of identifying whether a partial discharge pulse is generated on the cable shielding layer according to the extracted characteristic parameters comprises: The waveform similarity of the transient voltage signal and the pulse current signal is calculated according to the waveform similarity coefficient; if the voltage waveform polarity is the same as the current waveform polarity, and the waveform similarity is greater than the similarity threshold, and the voltage waveform duration and the current waveform duration are both less than the duration threshold, and the time difference between the voltage and current waveforms is less than the time difference threshold, then it is determined that a partial discharge pulse is generated on the cable shielding layer, otherwise it is determined to be an interference signal.

3. The method according to claim 2, characterized in that Also includes: If it is determined to be an interference signal, the method returns to the step of collecting the transient voltage signal and the pulse current signal on the cable shielding layer.

4. The method according to claim 1, characterized in that: The corresponding signal processing is performed on the transient voltage signal and the pulse current signal respectively, by filtering and amplifying the transient voltage signal and the pulse current signal respectively and then converting them into digital signals.

5. A combined detection device for partial discharge transient volt-ampere signals, characterized in that: include: case; Voltage signal probe, used to detect transient voltage signals on the cable shielding layer; Current signal probe, used to detect pulse current signal on cable shielding layer; The circuit board assembly is placed in the shell and is used to extract characteristic parameters after processing the transient voltage signal and the pulse current signal respectively, and to identify whether a partial discharge pulse is generated on the cable shielding layer according to the extracted characteristic parameters.

6. The device according to claim 5, characterized in that The circuit board assembly comprises: A first filtering and amplifying circuit, used for filtering and then amplifying the transient voltage signal; A second filtering and amplifying circuit, used for filtering and then amplifying the pulse current signal; An analog-to-digital conversion circuit, used for performing analog-to-digital conversion on the amplified transient voltage signal and the pulse current signal to obtain transient voltage data and pulse current data; The core processing unit is used to extract the characteristics of the transient voltage data and the pulse current data to obtain characteristic parameters, and then determine whether the obtained characteristic parameters meet the set conditions. If so, it is considered that a partial discharge pulse is generated on the cable shielding layer.

7. The device according to claim 6, characterized in that The characteristic parameters include voltage waveform polarity, current waveform polarity, voltage waveform duration, current waveform duration, waveform similarity coefficient, and time difference between voltage and current waveforms.

8. The device according to claim 7, characterized in that The step of judging whether the obtained characteristic parameters meet the set conditions, and if so, considering that a partial discharge pulse is generated on the cable shielding layer, includes: The waveform similarity of the transient voltage signal and the pulse current signal is calculated according to the waveform similarity coefficient; if the voltage waveform polarity is the same as the current waveform polarity, and the waveform similarity is greater than the similarity threshold, and the voltage waveform duration and the current waveform duration are both less than the duration threshold, and the time difference between the voltage and current waveforms is less than the time difference threshold, it is determined that a partial discharge pulse is generated on the cable shielding layer.

9. The device according to claim 6, characterized in that The first filtering and amplifying circuit includes a first capacitor, a first resistor, a second capacitor, a first amplifier, a first diode, and a second resistor; the first end of the first capacitor is connected to the voltage signal probe, the second end of the first capacitor is connected to the first end of the first resistor, the second end of the first resistor is respectively connected to the first end of the second capacitor and the positive input end of the first amplifier, the negative input end of the first amplifier is respectively connected to the first end of the second resistor and the output end of the first diode, the second end of the second resistor is connected to the power supply VCC, and the second end of the second capacitor and the input end of the first diode are grounded.

10. The device according to claim 6, characterized in that The second filtering and amplifying circuit includes a third capacitor, a third resistor, a fourth capacitor, a second amplifier, a second diode, and a fourth resistor; the first end of the third capacitor is connected to the current signal probe, the second end of the third capacitor is connected to the first end of the third resistor, the second end of the third resistor is respectively connected to the first end of the fourth capacitor and the positive input end of the second amplifier, the negative input end of the second amplifier is respectively connected to the first end of the fourth resistor and the output end of the second diode, the second end of the fourth resistor is connected to the power supply VCC, and the second end of the fourth capacitor and the input end of the second diode are grounded.

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