A partial discharge monitoring and alarm system

Abstract

The invention discloses a partial discharge monitoring and alarm system, comprising: a signal input module for acquiring partial discharge signals; a signal acquisition module for filtering, amplifying and converting partial discharge signals; a signal processing module for analyzing, identifying and grading partial discharge signals, storing them in a database and giving an alarm reminder; a signal output module for outputting an alarm signal; a power supply module for supplying power; the signal processing module comprises: a wavelet analysis unit for acquiring the frequency and time domain characteristics of partial discharge signals; a partial discharge identification unit for identifying signals with partial discharge characteristics; a partial discharge grading unit for classifying and grading partial discharge signal waveforms; a database unit for calculating and storing the discharge amount of partial discharge signals; and a danger warning unit for acquiring the discharge charge of partial discharge signals and outputting an alarm signal.

Description

Technical Field

[0001] The invention relates to the technical field of partial discharge monitoring, and in particular to a partial discharge monitoring alarm system. Background Art

[0002] Partial discharge (PD) is the discharge of an incomplete bridge circuit in the space between two electrodes. It may occur in gas-filled cavities in solid insulating materials, bubbles in liquid insulating materials, or on the surface of electrodes in the air. It is the main cause of accidents caused by long-term aging of electrical insulating materials. During equipment operation, monitoring of partial discharge can issue an alarm for impending insulation damage accidents. It allows operators to take remedial measures during equipment downtime. Partial discharge usually occurs under normal operating conditions, gradually damaging the electrical insulation of the equipment until it cannot withstand the voltage and an accident occurs.

[0003] High-voltage equipment often generates strong electromagnetic induction noise to the system grounding. There are many induction sources for the system grounding, including mechanical, electrical switching, and transmission radio frequency waves. The frequency range of these noise signals is very close to PD partial discharge, so simple bandpass filters are not very effective in suppressing this type of noise; during the acquisition and analysis process, the removal of noise signals is not very effective, and there is no good calculation algorithm for the discharge amount and danger level of partial discharge to provide real-time alarm reminders. Summary of the invention

[0004] The present invention aims to provide a partial discharge monitoring and alarm system, comprising:

[0005] A signal input module, used for acquiring partial discharge signals;

[0006] Signal acquisition module, used for signal filtering, amplification and conversion processing of partial discharge;

[0007] Signal processing module, used to analyze, identify and classify partial discharge signals, store them in a database and issue alarm reminders;

[0008] A signal output module, used for outputting an alarm signal;

[0009] A power supply module, connected to the signal input module, the signal acquisition module, the signal processing module and the signal output module respectively and used for supplying power;

[0010] The signal processing module includes: a wavelet analysis unit for acquiring the frequency and time domain characteristics of the partial discharge signal; a partial discharge identification unit for identifying signals with partial discharge characteristics; a partial discharge classification unit for classifying and grading the waveforms of the partial discharge signal; a database unit for calculating and storing the discharge amount of the partial discharge signal; and a danger warning unit for acquiring the discharge charge of the partial discharge signal and outputting an alarm signal.

[0011] Preferably, the signal acquisition module includes: an acquisition input unit, an acquisition processing unit, an acquisition amplification unit, an acquisition conversion unit, an acquisition output unit, a surge protection unit and a signal verification unit; the acquisition input unit obtains the local discharge signal from the multiplexer, transmits it to the acquisition processing unit for signal filtering processing, and then transmits the amplified local discharge signal to the acquisition amplification unit for signal amplification processing, and then the acquisition conversion unit performs analog-to-digital conversion on the local discharge signal to convert the analog signal into a digital signal, and finally transmits it to the acquisition output unit, and the acquisition output unit outputs the local discharge signal to the signal processing module, the surge protection unit is connected to the acquisition input unit, and is used to perform surge protection on the acquisition input unit, and the verification unit is connected to the acquisition processing unit to verify whether there is an error in the acquisition processing unit.

[0012] Preferably, the wavelet analysis unit acquires the partial discharge signal, quantizes and decomposes it into a group of wavelet functions and transforms it into a signal matching the input signal to obtain a pulse signal similar to the partial discharge signal, while removing the noise signal.

[0013] Preferably, the partial discharge identification unit distinguishes features including: leading edge rise time, trailing edge fall time and pulse width.

[0014] Preferably, the acquisition and amplification unit includes: a linear amplifier and a temporary storage amplifier; the linear amplifier has a bandwidth of 250 MHz and is used to connect a current transformer; the temporary storage amplifier has a bandwidth of 2 GHz and a dynamic range of 60 dB.

[0015] Preferably, the sampling rate of the signal acquisition module is 100 MB / SEC.

[0016] Preferably, the signal acquisition module is triggered to operate when the rising edge of the power module voltage passes through the zero point.

[0017] The danger warning unit includes: an equipment danger calculation unit and an alarm unit; the equipment danger calculation unit obtains the discharge degree and activity trend of the partial discharge signal every 24 hours, and calculates the danger level of each monitored equipment, and the danger level is a measurement value of the condition and health of the high-voltage insulation of the equipment; the alarm unit obtains the calculated danger level value, and outputs an alarm signal after the calculated danger level value reaches a threshold.

[0018] The present invention collects signal data from distributed partial discharge sensors through a multiplexer, processes and digitizes analog signals, analyzes and processes the digitized signals using noise reduction and partial discharge identification algorithms, stores the signals in a database, and issues an alarm signal according to the degree of danger. The signal collection efficiency is high, noise signals can be effectively filtered out, the discharge amount of partial discharge signals can be accurately calculated, and alarms can be issued in a timely manner, and the present invention is suitable for analyzing the long-term trend of partial discharge activities. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the connection relationship of the present invention;

[0020] Figure 2 This is a schematic diagram of the connection relationship of the signal processing modules of the present invention;

[0021] Figure 3 This is a schematic diagram of the connection relationship of the signal acquisition module of the present invention;

[0022] Figure 4 It is a characteristic diagram of partial discharge waveform of the present invention;

[0023] Figure 5 It is a schematic diagram of partial discharge segment data of the present invention;

[0024] Figure 6 It is a schematic diagram of partial discharge pulse waveform parameter measurement in the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with the embodiments and drawings.

[0026] This embodiment provides a partial discharge monitoring and alarm system, including:

[0027] The signal input module is provided with two signal input channels, and the two channels can collect partial discharge data at the same time. The distributed partial discharge sensor collects signal data and transmits it through a multiplexer to obtain partial discharge signals;

[0028] The multiplexer is provided with 8 input terminals, and 16 multiplexers can be set up. A maximum of 128 sensors can be connected by daisy chain connection. A unique address is set for each multiplexer, and then the partial discharge signals are collected sequentially.

[0029] Signal acquisition module, used for signal filtering, amplification and conversion processing of partial discharge;

[0030] Signal processing module, used to analyze, identify and classify partial discharge signals, store them in a database and issue alarm reminders;

[0031] A signal output module, used for outputting an alarm signal;

[0032] A power supply module, connected to the signal input module, the signal acquisition module, the signal processing module and the signal output module respectively and used for supplying power;

[0033] The signal processing module includes: a wavelet analysis unit, which obtains the frequency and time domain characteristics of the partial discharge signal; a partial discharge identification unit, which is used to identify signals with partial discharge characteristics; a partial discharge classification unit, which is used to classify and classify the partial discharge signal waveform; a database unit, which calculates and stores the discharge amount of the partial discharge signal; and a danger warning unit, which obtains the discharge charge of the partial discharge signal and outputs an alarm signal.

[0034] In a further implementation manner of the present embodiment, the signal acquisition module includes: an acquisition input unit, an acquisition processing unit, an acquisition amplification unit, an acquisition conversion unit, an acquisition output unit, a surge protection unit and a signal verification unit; the acquisition input unit obtains the local discharge signal from the multiplexer, transmits it to the acquisition processing unit for signal filtering processing, and then transmits the amplified local discharge signal to the acquisition amplification unit for signal amplification processing, and then the acquisition conversion unit performs analog-to-digital conversion on the local discharge signal, converts the analog signal into a digital signal, and finally transmits it to the acquisition output unit, the acquisition output unit outputs the local discharge signal to the signal processing module, the surge protection unit is connected to the acquisition input unit, and is used to perform surge protection on the acquisition input unit, and the verification unit is connected to the acquisition processing unit to verify whether there is an error in the acquisition processing unit.

[0035] In a further implementation manner of this embodiment, the signal acquisition module collects data for each channel once every 30 minutes; when there are many channels and the noise level is high, the data processing time is long, and all channels cannot be collected within 30 minutes, and the next collection starts immediately after the last collection.

[0036] The signal acquisition module uses a sequential acquisition method to acquire the two ASM input signals A and B from the partial discharge channel in the following order:

[0037] Table 1 Data collection sequence

[0038]

[0039] The signal acquisition module samples the analog signal at full rate for 10 consecutive power cycles, which is 200ms for 50Hz and 166.67ms for 60Hz.

[0040] The sampling and digitization rate of the partial discharge analog signal of the acquisition conversion unit is: 100MSamples / sec, that is, 100M samples per second, the word length is 12 bits (binary), and the voltage resolution is 0.25mV.

[0041] In a further implementation of this embodiment, the wavelet analysis unit obtains the partial discharge signal, quantizes and decomposes it into a set of wavelet functions and transforms it into a signal that matches the input signal, thereby obtaining a pulse signal similar to the partial discharge signal and removing the noise signal.

[0042] In a further implementation manner of this embodiment, the partial discharge classification unit classifies and classifies the identified partial discharge signal data into the following categories:

[0043] a. Cable partial discharge: The partial discharge signal is transmitted along the cable for a certain distance and can be divided into 15 cable partial discharge segments. The partial discharge peak value exceeds 5mV and the discharge amount exceeds 100pC.

[0044] b. Partial discharge of high voltage electrical appliances

[0045] The local PD, very close to the PD sensor, is divided into 15 PD segments.

[0046] For each data segment, the following information is calculated and stored:

[0047] Segment data: 2000-point segment of unprocessed sampled data, including the detected partial discharge signal. The sampling period of these 2000 points is 20μs, 4μs before the PD peak and 16μs after the PD peak.

[0048] like Figure 5 As shown, in the partial discharge data,

[0049] Vertical axis: pulse amplitude unit: mV;

[0050] Horizontal axis: time unit μS relative to PD pulse;

[0051] Rising edge time: the time from the start of the PD pulse to the peak value, in nanoseconds nS;

[0052] Falling edge time: the time from the peak value to the end of the PD pulse, in nanoseconds nS;

[0053] Pulse width: The width of the PD pulse signal (pulse duration), in nanoseconds nS;

[0054] Peak value: the peak value of the PD signal, in mV;

[0055] Area: The integral value (area) of the PD signal duration, converted into pC of electricity;

[0056] Position within the power cycle: The precise position of the PD signal within the power cycle relative to the synchronous trigger point, recorded in nanoseconds (ns). The synchronous trigger point is the zero crossing point of the rising edge of the monitor power supply voltage.

[0057] For CT sensors, the following calculations are performed:

[0058]

[0059] In a further implementation manner of this embodiment, the partial discharge identification unit distinguishes features including: leading edge rise time, trailing edge fall time and pulse width.

[0060] In a further implementation of this embodiment, the acquisition and amplification unit includes: a linear amplifier and a temporary amplifier; the linear amplifier has a bandwidth of 250 MHz and is used to connect a current transformer; the temporary amplifier has a bandwidth of 2 GHz and a dynamic range of 60 dB.

[0061] In a further implementation of this embodiment, the database unit obtains the discharge amount of the partial discharge signal, reads and loads it every 24 hours, and the discharge amount is calculated by calculating the area of ​​the pulse and the transfer function (TF) of the transmitter to obtain the apparent charge q of each discharge.

[0062]

[0063] In a further implementation manner of this embodiment, the sampling rate of the signal acquisition module is 100 MB / SEC.

[0064] In a further implementation manner of this embodiment, when the rising edge of the power module voltage passes through the zero point, the signal acquisition module is triggered to operate, and the phase of the acquired partial discharge signal is synchronized with the voltage of the power module.

[0065] The danger warning unit includes: an equipment danger calculation unit and an alarm unit; the equipment danger calculation unit obtains the discharge degree and activity trend of the partial discharge signal every 24 hours, and calculates the danger level of each monitored equipment. The danger level is a measurement of the condition and health of the equipment's high-voltage insulation; the alarm unit obtains the calculated danger level value, and after the calculated danger level value reaches the threshold, it outputs an alarm signal by sounding an alarm and simultaneously sending an email to the system.

[0066] For thousands of devices that are continuously monitored, long-term trend analysis of PD activity shows that the criticality, or likelihood of failure, is a function not only of the PD signal size, but also of the PD signal trend over time.

[0067] In a further implementation of this embodiment, during the signal analysis process, each data point represents an unprocessed signal, including both noise and partial discharge signals, and is recorded as the maximum value of the analog signal. The maximum analog signal exceeds 10 power supply cycles, is compressed into one cycle, and is stored for each channel and data acquisition cycle; in this embodiment, 720 data points are stored, 360 positive data points and 360 negative data points.

[0068] When performing signal analysis, select data acquisition within 10 power supply cycles and select the cycle with the highest amplitude for detailed analysis and partial discharge detection.

[0069] The point data selected for analysis are 2 million (50Hz) / 1.67 million (60Hz), and these data and partial discharges are calculated and identified by the wavelet analysis unit and the partial discharge identification unit.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A partial discharge monitoring and alarm system, characterized in that: include: A signal input module, used for acquiring partial discharge signals; Signal acquisition module, used for signal filtering, amplification and conversion processing of partial discharge; Signal processing module, used to analyze, identify and classify partial discharge signals, store them in a database and issue alarm reminders; A signal output module, used for outputting an alarm signal; A power supply module, connected to the signal input module, the signal acquisition module, the signal processing module and the signal output module respectively and used for supplying power; The signal processing module includes: a wavelet analysis unit for obtaining the frequency and time domain characteristics of the partial discharge signal; a partial discharge identification unit for identifying signals with partial discharge characteristics; a partial discharge classification unit for classifying and classifying the waveforms of the partial discharge signal; a database unit for calculating and storing the discharge amount of the partial discharge signal; a danger warning unit for obtaining the discharge charge of the partial discharge signal and outputting an alarm signal; The partial discharge classification unit classifies and classifies the identified partial discharge signal data into the following categories: a. Cable partial discharge: the partial discharge signal is transmitted along the cable for a distance and is divided into 15 cable partial discharge sections. The partial discharge peak value exceeds 5mV and the discharge amount exceeds 100pC. b. Partial discharge of high voltage electrical appliances The local PD, very close to the PD sensor, is divided into 15 PD segments; For each data segment, the following information is calculated and stored: Segment data: 2000-point segments of unprocessed sampled data, including the detected partial discharge signal; the sampling period of these 2000 points is 20µs, 4µs before the PD peak and 16µs after the PD peak; The danger warning unit includes: an equipment danger calculation unit and an alarm unit; the equipment danger calculation unit periodically obtains the discharge degree and activity trend of the partial discharge signal, and calculates the danger level of each monitored equipment, wherein the danger level is a measured value of the condition and health of the high-voltage insulation of the equipment; the alarm unit obtains the calculated value of the danger level, and outputs an alarm signal after the calculated value of the danger level reaches a threshold value; The signal acquisition module comprises: an acquisition input unit, an acquisition processing unit, an acquisition amplification unit, an acquisition conversion unit and an acquisition output unit; the acquisition input unit acquires the partial discharge signal from the multiplexer, transmits it to the acquisition processing unit for signal filtering, then transmits the amplified partial discharge signal to the acquisition amplification unit for signal amplification, then the acquisition conversion unit performs analog-to-digital conversion on the partial discharge signal, converts the analog signal into a digital signal, and finally transmits it to the acquisition output unit, and the acquisition output unit outputs the partial discharge signal to the signal processing module; The signal acquisition module collects data for each channel every 30 minutes; when there are many channels and the noise level is high, the data processing time is long and all channels cannot be collected within 30 minutes. The next collection starts again immediately after the last collection. The signal acquisition module samples the analog signal at full rate for 10 consecutive power cycles, which is 200ms for 50Hz and 166.67ms for 60Hz. The wavelet analysis unit acquires the partial discharge signal, quantizes and decomposes it into a group of wavelet functions, and transforms it into a signal that matches the input partial discharge signal, thereby obtaining a pulse signal similar to the partial discharge signal and removing the noise signal; During the signal analysis process, each data point represents the unprocessed signal, including both noise and partial discharge signals, and is recorded as the maximum value of the analog signal; the maximum analog signal exceeds 10 power supply cycles, which is compressed into one cycle and stored in each channel and data acquisition cycle; it is stored as 720 data points, 360 positive data points and 360 negative data points; When performing signal analysis, select data acquisition within 10 power supply cycles and select the cycle with the highest amplitude for detailed analysis and partial discharge detection; The point data selected for analysis are 2 million at 50Hz / 1.67 million at 60Hz. These data and partial discharges are calculated and identified by the wavelet analysis unit and the partial discharge identification unit.

2. The partial discharge monitoring and alarm system according to claim 1, characterized in that: The local discharge identification unit distinguishes features including: leading edge rise time, trailing edge fall time and pulse width.

3. The partial discharge monitoring and alarm system according to claim 1, characterized in that: The acquisition and amplification unit includes: a linear amplifier and a temporary storage amplifier; the linear amplifier has a bandwidth of 250MHz and is used to connect a current transformer; the temporary storage amplifier has a bandwidth of 2GHz and a dynamic range of 60dB.

4. The partial discharge monitoring and alarm system according to claim 1, characterized in that: The sampling rate of the signal acquisition module is 100MB / SEC.

5. The partial discharge monitoring and alarm system according to claim 1, characterized in that: When the rising edge of the voltage of the power module passes through the zero point, the signal acquisition module is triggered to operate.

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