A method for distinguishing partial discharge and interference pulse current of switch cabinet

Abstract

The application relates to a switch cabinet partial discharge and interference pulse current discrimination method, different types of partial discharge defects and interference sources are sequentially arranged in a switch cabinet, and measured pulse current signal time domain waveforms are respectively obtained in a detection frequency band, the detection frequency band is divided into a plurality of frequency bands, energy proportions of the frequency bands are calculated, and a database is established; on-site partial discharge signal detection is carried out, partial discharge pulse current signal time domain waveforms in the switch cabinet are collected, and energy proportions of the frequency bands are obtained; the actually measured pulse current signal time domain waveforms are compared with the database based on a digital twin simulation waveform amplitude calculation method, and then partial discharge and interference sources can be discriminated; the anti-interference capability is high, partial discharge and interference signals can be accurately discriminated, and the influence of detection and calculation is small. By using the method, the precision of partial discharge detection can be greatly improved, and partial discharge and interference sources can be accurately discriminated.

Description

Technical Field

[0001] This invention relates to a method for distinguishing between partial discharge and interference pulse current in switchgear, belonging to the field of power distribution network technology. Background Technology

[0002] High-voltage switchgear is a crucial electrical device in power distribution networks. Its main function is to open, close, control, and protect electrical equipment during power generation, transmission, distribution, and energy conversion. The components within a switchgear primarily include circuit breakers, disconnect switches, load switches, operating mechanisms, instrument transformers, and various protective devices.

[0003] During the production, transportation, installation, and maintenance of high-voltage switchgear, defects such as cracks, metal burrs, and scattered metal impurities are unavoidable. With long-term operation, these defects cause the local electric field strength on or inside the insulation surface to exceed the critical electric field strength of the insulation medium itself, thus triggering partial discharge. Furthermore, the persistent partial discharge phenomenon can further degrade the insulation, accelerating insulation failure.

[0004] Partial discharge sensors are often in strong electromagnetic environments and are subject to interference and influence from a wide variety of electromagnetic signals, which limits the sensitivity and accuracy of partial discharge monitoring.

[0005] Currently, commonly used anti-interference methods both domestically and internationally mainly include hardware and software filtering techniques, polarity identification and differential balance detection circuits, phase windowing techniques, wavelet analysis, and adaptive filtering techniques. These methods largely rely on the differences in the time-domain or frequency-domain characteristics of the partial discharge signal and the interference signal to separate them.

[0006] The testing site is subject to complex electromagnetic interference, and the types, sources, intensities, time-frequency characteristics, and statistical characteristics of interference signals vary under different site conditions. Furthermore, the use of time- and frequency-domain windowing methods inevitably leads to the loss of partial discharge signal energy, reducing the signal-to-noise ratio and lacking flexibility in application. Summary of the Invention

[0007] The purpose of this invention is to provide a method for distinguishing between partial discharge and interference pulse current in switchgear, so as to solve the problems mentioned in the background art.

[0008] The technical solution of the present invention is as follows:

[0009] A method for distinguishing between partial discharge and interference pulse current in switchgear includes the following steps:

[0010] S1. Different types of partial discharge defects and interference sources are set up in the switch cabinet in sequence, and the time-domain waveforms of the measured pulse current signals are obtained in the detection frequency band. The detection frequency band is divided into several frequency bands, the energy ratio of each frequency band is calculated, and a database is established.

[0011] S2. Conduct partial discharge signal detection on site, collect the time-domain waveform of partial discharge pulse current signal in the switch cabinet, and obtain the energy ratio of each frequency band of the signal at multiple measurement points;

[0012] S3. By comparing the time-domain waveform of the actual measured pulse current signal with the database based on the digital twin simulation waveform amplitude calculation method, partial discharge and interference sources can be identified.

[0013] Preferably, the detection frequency band is 300kHz to 300MHz.

[0014] Preferably, the detection frequency band of 300kHz to 300MHz is divided into three segments: 300kHz to 3MHz, 3MHz to 30MHz, and 30MHz to 300MHz.

[0015] Preferably, the interference source includes a conducted interference source and a radiated interference source.

[0016] Preferably, a Fourier transform is performed on the pulse current signal I(t) to obtain the spectral waveform I(jω) of the pulse current signal. The formula is as follows:

[0017]

[0018] Preferably, the energy of each frequency band of the pulse current spectrum waveform I(jω) is calculated using the following formula:

[0019]

[0020] In the formula, i represents the signal source number, i = 1, 2, ..., n; E represents the energy; ω2 and ω1 represent the upper and lower limits of the angular frequency, ω = 2πf.

[0021] Preferably, the total energy E of each experiment is obtained. th and energy E in each frequency band ath E bth E cth Then, by calculating the energy proportion η of each frequency band... ath η bth η cth Its formula is:

[0022]

[0023] Preferably, the database is viewed as a set of n vectors, each containing an element representing the energy proportion of each frequency band in the detection band, denoted by M.i The identifier, namely:

[0024] M i =(η athi ,η bthi ,η cthi ,...)

[0025] The measured pulse current waveform amplitudes at each measurement point of the switchgear are also considered as vectors. Each vector contains the energy proportion of each frequency band in the detection frequency band, denoted by S, i.e.:

[0026] S=(η ts1 η ts2 η ts3 ,...)

[0027] The point with the largest value is selected to determine its signal source type. The calculation method is as follows:

[0028] D i =η athi ·η ts1 +η bthi ·η ts2 +η cthi ·η ts3 +\\\,i=1,2…n (3).

[0029] The present invention has the following beneficial effects:

[0030] It has strong anti-interference capabilities and can accurately distinguish between partial discharge and interference signals;

[0031] It exhibits high robustness against interference and is less affected by detection and calculation.

[0032] This method can greatly improve the accuracy of partial discharge detection, accurately distinguishing between partial discharge and interference sources. After achieving interference suppression based on this method, the accuracy and efficiency of equipment insulation defect diagnosis and prediction, as well as maintenance, will be greatly improved, significantly enhancing the safety and reliability of switchgear. Attached Figure Description

[0033] Figure 1 This is an electrical connection diagram of the switch cabinet of the present invention;

[0034] Figure 2 This is the technical approach of the present invention;

[0035] Figure 3 This is a schematic diagram of the experiment of the present invention;

[0036] Figure 4 This is a database of the energy proportion of each frequency band of the partial discharge pulse current signal in the high-voltage switchgear of this invention.

[0037] The reference numerals in the figure are as follows:

[0038] 1. Busbar; 2. Circuit breaker; 3. Current transformer; 4. Surge arrester; 5. Live indicator; 6. Grounding switch; 7. High-voltage cable; 8. Coupling capacitor; 9. Pulse current coupling unit. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0040] The technical principle of this invention is as follows: when partial discharge or conducted interference or radiated interference occurs in the switchgear, when its pulse signal reaches the detection coupling device, its transfer function depends on the propagation path and coupling method; the energy ratio of each frequency band of the signal obtained by the coupling device is directly related to the type of discharge and interference; by using the measured energy ratio of each frequency band of the pulse signal and the energy ratio database of each frequency band to perform energy ratio correlation calculation, the partial discharge and interference source can be identified.

[0041] Example:

[0042] The electrical wiring diagrams for the internal components of the high-voltage switchgear are as follows: Figure 1 As shown, the high-voltage switchgear mainly consists of busbar 1, circuit breaker 2, current transformer 3, surge arrester 4, live indicator 5, grounding switch 6, and high-voltage cable 7. To couple partial discharge pulse signals, coupling capacitors 8 and pulse current coupling units 9 are arranged at the phase-connected holes of the switchgear.

[0043] Flowchart as follows Figure 2 As shown:

[0044] First, such as Figure 3 As shown, partial discharge tests were conducted on switchgear in the laboratory. Different types of partial discharge defects (partial discharge pulse sources), as well as conducted interference sources and radiated interference sources were set in the switchgear. Partial discharge tests were carried out on each type of signal. The time-domain waveform I(t) of the pulse current signal was measured, the energy ratio of each frequency band was calculated, and a database was established.

[0045] Second, partial discharge signal detection was carried out on site, and the time-domain waveform of the partial discharge pulse current signal in the switch cabinet was collected to obtain the energy ratio of each frequency band of the signal at multiple measurement points.

[0046] Third, by performing correlation calculations on the energy proportions of each frequency band between the actual measured waveform and the waveform in the database, partial discharge and interference sources can be identified.

[0047] Calculation of the energy proportion of each frequency band of the pulse current signal:

[0048] The energy of the pulse current signal I(t) in each frequency band is calculated using the following formula:

[0049]

[0050] Different types of signal sources were set up (signal source numbered i, i = 1, 2, ..., n), and the detection frequency band of 300kHz to 300MHz was divided into three segments: 300kHz to 3MHz, 3MHz to 30MHz, and 30MHz to 300MHz. Pulse current signals were obtained through experiments and detections to obtain the total energy E of each experiment. th and energy E in each frequency band ath E bth E cth Then, by calculating the energy proportion η of each frequency band... ath η bth η cth Its formula is:

[0051]

[0052] Establish a database of the energy proportions of partial discharge, conducted interference, and radiated interference, such as... Figure 4 As shown, the database is an n×3 matrix.

[0053] Acquisition of waveform parameters of pulse current signal in switchgear: Partial discharge signal is measured in the switchgear to obtain the time-domain waveform Its(t) of the measured pulse current signal. The energy proportion of each frequency band is calculated using formulas (1) and (2), yielding η. ts1 η ts2 η ts3 .

[0054] Determining the location of partial discharge based on digital twin simulation waveform amplitude correlation calculation method:

[0055] View the database as a set of n vectors, each containing 3 elements, and use M... i The identifier, namely:

[0056] M i =(η athi ,η bthi ,η cthi ), i = 1, 2, ..., n;

[0057] The measured amplitude of the switchgear pulse current waveform at each measurement point is also considered as a vector, with each vector containing 3 elements, denoted by S, i.e.:

[0058] S=(η ts1 η ts2 η ts3 )

[0059] S and Mi are calculated one by one using the amplitude correlation formula. The point with the largest correlation is selected as the signal source type, thus identifying partial discharge and interference sources. The calculation method is as follows:

[0060] D i =η athi ·η ts1 +η bthi ·η ts2 +η cthi ·η ts3 , i = 1, 2…n (3).

[0061] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for distinguishing between partial discharge and interference pulse current in switchgear, characterized in that: Includes the following steps: S1. Different types of partial discharge defects and interference sources are set up in the switch cabinet in sequence, and the time-domain waveforms of the measured pulse current signals are obtained in the detection frequency band. The detection frequency band is divided into several frequency bands, the energy ratio of each frequency band is calculated, and a database is established. S2. Conduct partial discharge signal detection on site, collect the time-domain waveform of partial discharge pulse current signal in the switch cabinet, and obtain the energy ratio of each frequency band of the signal at multiple measurement points; S3. By comparing the time-domain waveform of the actual measured pulse current signal with the database based on the digital twin simulation waveform amplitude calculation method, partial discharge and interference sources can be identified. The detection frequency band is 300kHz~300MHz; The detection frequency band of 300kHz~300MHz is divided into three segments: 300kHz~3MHz, 3MHz~30MHz and 30MHz~300MHz. The interference sources include conducted interference sources and radiated interference sources; The energy of the pulse current signal at each frequency band is calculated using the following formula: （1） In the formula, i represents the signal source number, i=1,2,...,n; E represents energy; ω 2 and ω 1 represents the upper and lower limits of angular frequency. ω =2π f ; The database is viewed as a set of n vectors, each containing an element representing the energy proportion of each frequency band in the detection band. M is used as the unit of measurement. i The identifier, namely: M i =(η athi ,or bthi ,or cthi ,...) The measured pulse current waveform amplitudes at each measurement point of the switchgear are also considered as vectors. Each vector contains the energy proportion of each frequency band in the detection frequency band, denoted by S, i.e.: S=(η ts1 ,or ts2 ,or ts3 ,...) The point with the largest value is selected to determine its signal source type. The calculation method is as follows: ,i=1,2…n(3)。

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