CN115166450A - Switch cabinet part partial discharge positioning method based on pulse current signal frequency spectrum - Google Patents
Switch cabinet part partial discharge positioning method based on pulse current signal frequency spectrum Download PDFInfo
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- CN115166450A CN115166450A CN202210984935.2A CN202210984935A CN115166450A CN 115166450 A CN115166450 A CN 115166450A CN 202210984935 A CN202210984935 A CN 202210984935A CN 115166450 A CN115166450 A CN 115166450A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
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Abstract
The invention discloses a switch cabinet part partial discharge positioning method based on a pulse current signal frequency spectrum, belonging to the technical field of partial discharge positioning. The method comprises the following steps of 1: carrying out partial discharge test and measurement on the switch cabinet, and establishing a test frequency mean value f of a pulse current signal ath And test equivalent bandwidth F wth Establishing a frequency spectrum characteristic quantity median database; step 2: detecting local discharge signals on site, collecting local discharge pulse current signals in the switch cabinet, and calculating the actually measured frequency mean value f ats And measured equivalent bandwidth F wts (ii) a And step 3: calculating Euclidean distance D between the partial discharge pulse current signal acquired in the step 2 and the data median value in the step 1 i And determining the partial discharge part according to the minimum distance principle. The method of the invention can be very largeThe accuracy of on-site partial discharge positioning is improved, equipment with defects is prevented from being put into operation, and the progress of electrical equipment tests and detection technology is greatly promoted.
Description
Technical Field
The invention relates to the technical field of partial discharge positioning, in particular to a switch cabinet part partial discharge positioning method based on a pulse current signal frequency spectrum.
Background
The high-voltage switch cabinet is used as an important electrical device in a power distribution network of a power system, and is mainly used for opening, closing, controlling and protecting the electrical device in the process of power generation, power transmission, power distribution and electric energy conversion of the power system. The components in the switch cabinet mainly comprise a circuit breaker, an isolating switch, a load switch, an operating mechanism, a mutual inductor, various protection devices and the like. In the production, transportation, installation and maintenance processes of the high-voltage switch cabinet, the defects of cracks, metal burrs, scattered metal impurities and the like are inevitable. As the switchgear operates for a long time, these defects lead to local field strengths at the insulating surface or inside being higher than the critical field strength of the insulating medium itself, thus causing partial discharges to occur. Meanwhile, the partial discharge phenomenon existing for a long time can also cause further deterioration of insulation and accelerate insulation failure. Therefore, strengthening the partial discharge detection and diagnosis positioning is an important prerequisite for ensuring the safe and reliable operation of the switch cabinet.
The high-voltage switch cabinet partial discharge detection and diagnosis positioning technology is a hot spot of domestic and foreign research. The generation of partial discharge is accompanied by various physical phenomena such as sound, electricity, light, heat, and the like, and various partial discharge detection methods have been developed by monitoring these physical quantities reflecting the discharge phenomenon. At home and abroad, the commonly used detection methods mainly comprise an ultrasonic method, an ultrahigh frequency method and a transient-state to ground voltage method, and the local discharge positioning is generally carried out by the amplitude in the methods. The methods are external detection methods, and due to the fact that the local discharge signal propagation process is complex and the field interference is complex, the positioning accuracy of the methods is low and the errors are large. In the case of good detection conditions, these methods can only be used to determine the switchgear cabinet on which the partial discharge is located, but not which component inside the switchgear cabinet the partial discharge is located. Inaccurate positioning and inaccurate guidance and maintenance decision. Therefore, accurate component-level positioning of partial discharges in switchgear cabinets is the focus of future research.
The existing switch cabinet partial discharge positioning method comprises the following steps:
(1) Partial discharge positioning method based on sound-electricity combination and sound-sound combination
The acoustic-acoustic combined time delay positioning method is characterized in that four or more ultrasonic sensor nodes are arranged in space, and the position of a discharge point is calculated according to the propagation speed of ultrasonic waves in the air and the signal time measured by each measuring point; according to the acoustic-electric combined time delay positioning method, one ultrasonic sensor node in the acoustic-electric combined positioning method is replaced by an ultrahigh frequency sensor or TEV sensor node and is used as a reference trigger node, and the position of a discharging point is calculated by the same method. However, the method has poor anti-interference capability and positioning is easy to deviate.
(2) Switch cabinet partial discharge positioning method based on earth electric wave principle
In the process that the ground electric wave is transmitted on the surface of the metal wall, a TEV signal is induced, a plurality of TEV sensors are adopted for detection, the strength of the TEV signal and the trigger time of a first TEV pulse are detected, and the partial discharge positioning of the switch cabinet can be realized according to the amplitude and the time delay. However, the ground electric wave signal is attenuated more quickly, and the frequency range of the measured signal and the field interference is overlapped, so the field application effect is not good.
(3) High-voltage switch cabinet typical partial discharge defect positioning based on ultrahigh frequency method
2 ultrahigh frequency sensors are respectively placed at 2 different positions, ultrahigh frequency signals generated by partial discharge are transmitted to the sensors through the shortest air path, electromagnetic wave signals are converted into electric signals, and waveform information of the electric signals is displayed on a display screen of an oscilloscope. The time difference can be obtained by comparing oscilloscope display screens, and the linear distance difference between the local discharge source and the 2 sensors, namely the distance from the discharge source to the vertical bisector of the 2 sensors, can be calculated according to the time difference and the known quantity wave speed. The position of the partial discharge source can be determined by placing the sensor at different positions for multiple measurements. But the gap of the cabinet body of the existing switch cabinet is small, and the ultrahigh frequency signal is difficult to transmit, so the positioning precision is low.
With the increasing emphasis on the partial discharge detection and positioning workgroups, the related sensing, acquisition and analysis technologies are greatly developed. The technology of detecting the partial discharge pulse current of the switch cabinet is a detection method emerging in recent years, in the method, a pulse signal is transmitted through a coupling capacitor connected to a high-voltage bus, and the pulse current signal is received by a sensor connected to a grounding end of the coupling capacitor. The coupling capacitors and the partial discharge sensors arranged in each cabinet can be used for detecting one by one, and the switch cabinet with the partial discharge defects can be judged through the signal amplitude. In addition, based on the influence of the switch cabinet components on the propagation characteristics of the pulse current signals, the components where the partial discharge defects are located can be determined by analyzing the frequency spectrum characteristics of the pulse current signals.
In summary, the existing switch cabinet local discharge positioning technology adopts a time domain positioning method to perform positioning according to the amplitude and time delay of a time domain waveform, but the method has extremely high requirements on the resolution of a measuring instrument, and due to the existence of interference, misjudgment and missed judgment are likely to be caused to the information such as the amplitude of the waveform, the arrival time of a first wave, and the positioning accuracy is reduced. Therefore, a switch cabinet part partial discharge positioning method based on a pulse current signal frequency spectrum is needed to perform positioning analysis on the switch cabinet partial discharge in a frequency domain angle.
Disclosure of Invention
The invention aims to provide a switch cabinet part partial discharge positioning method based on a pulse current signal frequency spectrum, which is characterized by comprising the following steps of:
step 1: carrying out partial discharge test and measurement on the switch cabinet, and establishing a test frequency mean value f of a pulse current signal ath And test equivalent bandwidth F wth Calculating the data median of partial discharge of each component, and establishing a frequency spectrum characteristic quantity median database;
and 2, step: detecting local discharge signals on site, collecting local discharge pulse current signals in the switch cabinet, and calculating the actually measured frequency mean value f ats And measured equivalent bandwidth F wts ；
And 3, step 3: calculating Euclidean distance D between the partial discharge pulse current signal acquired in the step 2 and the data median value in the step 1 i And determining the partial discharge part according to the minimum distance principle.
The step 1 specifically comprises the following substeps:
step 11: a coupling capacitor is connected in parallel in the switch cabinet, and the grounding end of the coupling capacitor is connected with a pulse current coupling unit to couple pulse current signals; respectively carrying out a partial discharge test on each component in the switch cabinet, and measuring a pulse current signal time domain waveform I (t);
step 12: performing Fourier transform on the pulse current signal time domain waveform I (t) in the step 11 to obtain a pulse current signal frequency spectrum waveform I (j omega);
step 13: extracting a test frequency mean value f through a pulse current signal frequency spectrum waveform I (j omega) ath And test equivalent bandwidth F wth And performing multiple tests at the same position, calculating the median value of the data, and establishing a median database of spectral characteristic quantity。
The step 3 is specifically as follows:
forming a frequency spectrum characteristic quantity median database into n vectors M i A set of constructs; the vector M i Comprises the following steps:
M i ＝(f athmi ,F wthmi )，i＝1,2,…,n；
wherein, f athmi Is the mean value of the test frequency of the ith component, F wthmi The experimental equivalent bandwidth for the ith component;
the measured frequency mean value f ats And the measured equivalent bandwidth F wts Form a vector S, i.e.:
S＝(f ats ,F wts )
calculating S and M one by one through an Euclidean distance formula i Has a Euclidean distance D between i Selecting a part with the minimum Euclidean distance as a partial discharge part; the Euclidean distance D i The calculation method comprises the following steps:
the invention has the beneficial effects that:
1. the method can greatly improve the precision of on-site partial discharge positioning, avoid the equipment from being put into operation with defects, and greatly promote the progress of electrical equipment testing and detection technology; the positioning result can be accurate to a certain component in the switch cabinet, and the robustness is higher;
2. after the accurate positioning is realized based on the method, the accuracy and the working efficiency of equipment insulation defect diagnosis prediction and operation and maintenance are greatly improved, and the safety and the reliability of the switch cabinet are greatly improved;
3. the invention reduces the probability of insulation failure of the high-voltage switch cabinet of 10 kV-35 kV, and has obvious direct and indirect economic benefits.
Drawings
FIG. 1 is a diagram of electrical connections in a high voltage switchgear based on a method for locating partial discharge of a switchgear component based on a pulsed current signal spectrum according to the present invention;
fig. 2 is a flowchart of a method for positioning partial discharge of a switch cabinet component based on a pulse current signal frequency spectrum according to the present invention.
Detailed Description
The invention provides a method for positioning partial discharge of a switch cabinet component based on a pulse current signal frequency spectrum, and the invention is further explained by combining the attached drawings and the specific embodiment.
When a certain component in the switch cabinet generates partial discharge and a pulse current signal reaches the detection coupling device, the transfer function of the pulse current signal depends on the impedance characteristics of lines and components in a propagation path; the spectral characteristics of the signal obtained by the coupling device are directly related to the partial discharge position; the frequency spectrum characteristic of the local discharge pulse current signal can be used for mapping the part where the local discharge is located.
The electrical connection diagram of the internal components of the high-voltage switchgear is shown in fig. 1. The high-voltage switch cabinet mainly comprises a high-voltage busbar 1, a circuit breaker 2, a current transformer 3, a lightning arrester 4, an electrified display device 5, a grounding disconnecting link 6 and a high-voltage cable 7. In order to couple the partial discharge pulse signal, a coupling capacitor 8 and a pulse current coupling unit 9 are arranged inside the switchgear cabinet.
In order to realize accurate positioning of the partial discharge of the switch cabinet, the invention provides a flow chart of a switch cabinet partial discharge positioning method based on the frequency spectrum characteristics of a pulse current signal, which is shown in fig. 2. The implementation steps comprise: firstly, the partial discharge test and measurement of the switch cabinet are carried out in a laboratory, and the frequency average value (f) of a pulse current signal is established ath ) Equivalent bandwidth (F) wth ) And calculating a data median value of partial discharge of each component; secondly, develop the partial discharge signal detection at the scene, gather the partial discharge pulse current signal in the cubical switchboard, calculate the frequency spectrum parameter, include: frequency mean value (f) ats ) Equivalent bandwidth (F) wts ) (ii) a Thirdly, calculating Euclidean distance between the sampling parameters and the median value of the standard samples of the database, and determining a part where partial discharge is located according to a minimum distance principle. The method comprises the following specific steps:
(1) Establishing a local discharge pulse current spectrum parameter database of a high-voltage switch cabinet component
Partial discharge test and pulse current signal time domain waveform acquisition of each component of the switch cabinet; and manufacturing partial discharge defects on all parts of the switch cabinet according to the actual partial discharge case of the switch cabinet. The switch cabinet is internally connected with a coupling capacitor in parallel, and the grounding end of the switch cabinet is connected with a coupling unit for coupling the pulse current signal. And respectively carrying out a partial discharge test on each component in the switch cabinet, and measuring the time domain waveform I (t) of the pulse current signal.
Fourier transformation and frequency spectrum parameter calculation of the pulse current signal; the pulse current signal I (t) is fourier transformed to obtain a spectrum waveform I (j ω) of the pulse current signal. The fourier transform equation is:
the characteristic quantity of the pulse current signal frequency domain waveform I (j ω) is represented by the mean value and the dispersion of the spectrum waveform, and these two characteristic quantities are referred to as: mean value of frequency (f) a ) Equivalent bandwidth (F) w ). Guiding | I (j ω) & gtnon 2 And (4) calculating the mean value and standard deviation of the probability density to obtain the frequency domain characteristic parameters. Mean value of frequency (f) a ) Equivalent bandwidth (F) w ) Are respectively defined as:
in the formula (2): e p Is the energy of the signal or signals,
ω＝2πf；f a is the frequency average of the signal; f w Is the equivalent bandwidth of the signal.
A pulse current signal frequency spectrum parameter median database; partial discharge sources are respectively arranged on each component (component number i, i =1,2, \ 8230;, n) of the switch cabinet, pulse current signals are obtained through tests and detection, and the frequency mean value (f) of the pulse current signals is extracted athi ) Equivalent bandwidth (F) wthi ) Characteristic parameters, performing k times of experiments at the same position, and extracting frequency characteristicsCharacterizing parameters and calculating the data median (f) athmi 、F wthmi ) The formula is as follows:
and establishing a frequency spectrum characteristic quantity database. As shown in table 1, the database is an n × 2 matrix.
TABLE 1 high-tension switch cabinet partial discharge pulse current signal frequency spectrum characteristic quantity median database
(2) Measurement and calculation of frequency spectrum parameters of pulse current signals of switch cabinet
Time domain waveform I for measuring partial discharge pulse current signal in switch cabinet ats (t) of (d). Based on the time domain waveform, two frequency domain characteristic quantities of the pulse current signal are calculated. The calculation formula is as shown in formula (2). The actually measured pulse current frequency domain characteristic quantity of the switch cabinet is obtained through calculation and is respectively as follows: center frequency (f) ats ) Equivalent bandwidth (F) wts )。
(3) Part for determining partial discharge based on minimum Euclidean distance principle
The database is viewed as a set of n vectors, each vector containing 2 elements, with M i Identification, namely:
M i ＝(f athmi ,F wthmi )，i＝1,2,…,n
the actually measured pulse current spectrum characteristic quantity of the switch cabinet is also taken as a vector and expressed by S, namely:
S＝(f ats ,F wts )
calculating S and M one by one through an Euclidean distance formula i The Euclidean distance between the two points is selected as the positioning result, and the point with the minimum Euclidean distance is selected as the positioning result. The euclidean distance is calculated as follows:
in addition, the invention has high positioning precision and can accurately judge the part where the partial discharge defect is positioned; and the positioning calculation has high robustness and is less influenced by detection and calculation.
Claims (3)
1. The method for positioning the partial discharge of the switch cabinet component based on the pulse current signal frequency spectrum is characterized by comprising the following steps of:
step 1: performing partial discharge test and measurement of the switch cabinet, and establishing a test frequency mean value f of a pulse current signal ath And test equivalent bandwidth F wth Calculating the data median of partial discharge of each component, and establishing a frequency spectrum characteristic quantity median database;
and 2, step: detecting local discharge signals on site, collecting local discharge pulse current signals in the switch cabinet, and calculating the actually measured frequency mean value f ats And the measured equivalent bandwidth F wts ；
And step 3: calculating Euclidean distance D between the partial discharge pulse current signal acquired in the step 2 and the data median value in the step 1 i And determining the partial discharge part according to the minimum distance principle.
2. The method for locating partial discharge of a switch cabinet component based on a pulse current signal frequency spectrum according to claim 1, wherein the step 1 specifically comprises the following sub-steps:
step 11: a coupling capacitor is connected in parallel in the switch cabinet, and the grounding end of the coupling capacitor is connected with a pulse current coupling unit to couple pulse current signals; respectively carrying out a partial discharge test on each component in the switch cabinet, and measuring a pulse current signal time domain waveform I (t);
step 12: performing Fourier transform on the pulse current signal time domain waveform I (t) in the step 11 to obtain a pulse current signal frequency spectrum waveform I (j omega);
step 13: extracting a test frequency mean value f through a pulse current signal frequency spectrum waveform I (j omega) ath And test equivalent bandwidth F wth And performing multiple trials at the same locationAnd (4) checking, calculating a data median value, and establishing a frequency spectrum characteristic quantity median value database.
3. The method for positioning partial discharge of a switch cabinet component based on a pulse current signal frequency spectrum according to claim 1, wherein the step 3 is as follows:
forming a frequency spectrum characteristic quantity median database into n vectors M i A set of constructs; the vector M i Comprises the following steps:
M i ＝(f athmi ,F wthmi )，i＝1,2,…,n；
wherein f is athmi Is the mean value of the test frequency of the ith component, F wthmi The experimental equivalent bandwidth for the ith component;
the measured frequency mean value f ats And measured equivalent bandwidth F wts Form a vector S, i.e.:
S＝(f ats ,F wts )
calculating S and M one by one through an Euclidean distance formula i Has a Euclidean distance D between i Selecting a part with the minimum Euclidean distance as a partial discharge part; the Euclidean distance D i The calculation method comprises the following steps:
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| CN116482560A (en) * | 2023-06-21 | 2023-07-25 | 中国华能集团清洁能源技术研究院有限公司 | Battery fault detection method and device, electronic equipment and storage medium |
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| CN116482560A (en) * | 2023-06-21 | 2023-07-25 | 中国华能集团清洁能源技术研究院有限公司 | Battery fault detection method and device, electronic equipment and storage medium |
| CN116482560B (en) * | 2023-06-21 | 2023-09-12 | 中国华能集团清洁能源技术研究院有限公司 | Battery fault detection method and device, electronic equipment and storage medium |
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