CN116256599A - Calculation method and device for initial time point of fault arcing of distribution cable - Google Patents
Calculation method and device for initial time point of fault arcing of distribution cable Download PDFInfo
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- 238000009413 insulation Methods 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 3
- 229920003020 cross-linked polyethylene Polymers 0.000 description 3
- 239000004703 cross-linked polyethylene Substances 0.000 description 3
- 238000010891 electric arc Methods 0.000 description 3
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- 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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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- G—PHYSICS
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- 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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
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Abstract
The invention discloses a calculation method and a device of an initial arcing time point of a power distribution cable fault, wherein the method comprises the following steps: acquiring single-phase earth fault recording data of a distribution line, wherein the single-phase earth fault recording data comprises zero sequence voltage and zero sequence current data; judging the starting and ending time points of the fault through zero sequence voltage; extracting zero sequence current data between the starting time point and the ending time point of the fault, and carrying out band-pass filtering treatment; a1 section is arranged between two zero crossing points of the zero sequence current; taking the data between 2 zero crossing points as 1 arcing and arc extinguishing process, and marking as F (n); calculating waveform similarity coefficients rho (n) of each segment F (n) of the filtered zero sequence current data; and judging specific starting time according to the similarity coefficient rho (n). The invention can accurately judge the arcing time of the cable fault and provide reliable data for effectively evaluating and early warning the state of the cable.
Description
Technical Field
The invention relates to a calculation method and a calculation device for an initial arcing time point of a power distribution cable fault, and belongs to the technical field of power distribution network line fault monitoring.
Background
The power cables used in the 10-35 kV distribution network are all crosslinked polyethylene (XLPE) cables. In the insulation breakdown process of the crosslinked polyethylene medium, the branch discharge phenomenon particularly highlights that an electric field is formed on an interface after the cable is electrified, when the intensity of the electric field reaches a certain value, micro spark discharge is formed on two organic insulation interfaces, a small amount of carbonized particles are generated on the interfaces, and the carbon particles have a conductive function, so that the insulation performance of the organic insulation interfaces is weakened, the breakdown voltage of the interfaces is reduced, the formation of an electric arc between a cable conductor and the ground is caused, and the cable conductor finally develops into a ground fault. The degradation and defect development of the cable are statistical, the development speed is high or low, but most of the cable has a certain development period, and if relevant parameters such as the time and the intensity of arc discharge are accurately detected during the development period, data basis can be provided for effectively evaluating and early warning the state of the cable.
The patent application 201210425483.0, namely the high-resistance ground fault detection method based on zero-sequence current zero-crossing interruption discrimination, discloses a method for judging the occurrence of a high-resistance ground fault by the time that the sampling value of the zero-sequence current zero-crossing point is smaller than a threshold value, but does not describe the applicability of the arc ground fault.
The patent application number 202111580059.9, namely a submerged arc arcing time prediction method and a submerged arc arcing time prediction system, proposes that a submerged arc image is acquired, the submerged arc image is preprocessed, the arcing time is subjected to multiple fitting regression, an arcing time regression model is obtained, and an arcing time prediction method is carried out.
The patent application No. 202210885471.X, a method for identifying the type of ground fault by using a characteristic curve of zero-sequence current, provides a method for identifying the type of ground fault in a distribution line by constructing a trend function of the amplitude of zero-sequence current and using characteristic parameters of a curve fitting means, particularly identifying a tree line fault, but does not describe the type of ground fault in detail.
Disclosure of Invention
In order to solve the problems, the invention provides a calculation method and a device for the initial arcing time point of a power distribution cable fault, which can realize accurate calculation of arcing time of the fault so as to provide a basis for effectively evaluating the state of the cable.
The technical scheme adopted for solving the technical problems is as follows:
in a first aspect, the method for calculating the initial time point of fault arcing of a power distribution cable provided by the embodiment of the invention includes the following steps:
step 1, acquiring single-phase earth fault wave recording data of a distribution line, wherein the single-phase earth fault wave recording data comprise zero sequence voltage and zero sequence current data;
step 2, judging the starting and ending time points of the faults through zero sequence voltages;
step 3, extracting zero sequence current data between the starting time point and the ending time point of the fault, and carrying out band-pass filtering treatment;
step 4, 1 section is arranged between two zero-sequence current zero-crossing points; taking the data between 2 zero crossing points as 1 arcing and arc extinguishing process, and marking the data as F (n), wherein n is more than or equal to 1, and n represents the nth arcing and arc extinguishing process;
step 5, calculating waveform similarity coefficient ρ (n) of each segment F (n) of the filtered zero sequence current data with each other:
in the formula ,i01 、i 02 The zero sequence currents of the two adjacent sections of arcing and arc extinguishing processes are respectively, wherein the sampling starting point k=1 is the initial moment, k is a sampling sequence, and N is the data length;
and 6, judging specific starting time according to the similarity coefficient rho (n).
As a possible implementation manner of this embodiment, the starting point of the judgment of the zero sequence voltage uses 3 half waves and 5 cycles before the 1 st half wave as the starting point.
As a possible implementation manner of this embodiment, the zero sequence voltage determines the ending time point, ends 3 half waves, and ends the 3 rd half wave.
As one possible implementation manner of this embodiment, the band-pass filtering process is to filter the direct current, the power frequency and the high frequency data in the zero-sequence current data by using an FIR 9-order band-pass filter with a passband frequency of 150Hz to 4000 Hz.
As a possible implementation manner of this embodiment, the calculation process of the zero crossing point is as follows:
setting sampling values of 2 sampling points adjacent to zero crossing points as A0 and A1 respectively, wherein the situation that the sampling point is just zero crossing point is regarded as a special situation that one of the A0 and A1 is zero;
the zero crossing point is determined according to the time relation between the sampling point and the zero point:
wherein ,
the interval time between the zero crossing point and the 2 nd sampling point is the sampling interval time.
As a possible implementation manner of this embodiment, the determining a specific start time according to the similarity coefficient ρ (n) includes:
if the similarity coefficient ρ (n) is not less than 0.6, p (n) =1; if the similarity coefficient ρ (n) < 0.6, p (n) =0;
if p (n) =1 and p (n+1) =0 and p (n+2) =1, then F (n+1) is considered to be the arcing initial time point;
if p (n) =0 and p (n+1) =1 and p (n+2) =1, then F (n) is considered to be the arcing initial time point;
f (n+2) is considered to be the arcing initial time point if p (n) =1 and p (n+1) =1 and p (n+2) =0.
In a second aspect, an embodiment of the present invention provides a computing device for an initial point in time of fault arcing of a distribution cable, including:
the data acquisition module is used for acquiring single-phase earth fault wave recording data of the distribution line, wherein the single-phase earth fault wave recording data comprise zero sequence voltage and zero sequence current data;
the fault starting and stopping time point judging module is used for judging the starting and ending time points of the fault through the zero sequence voltage;
the band-pass filtering processing module is used for extracting zero sequence current data between the starting time point and the ending time point of the fault and carrying out band-pass filtering processing;
the arcing and arc extinguishing process determining module is used for determining 1 section between two zero crossing points of zero sequence current; taking the data between 2 zero crossing points as 1 arcing and arc extinguishing process, and marking the data as F (n), wherein n is more than or equal to 1, and n represents the nth arcing and arc extinguishing process;
the similarity coefficient calculation module is used for calculating waveform similarity coefficients rho (n) of each segment F (n) of the filtered zero-sequence current data with each other:
in the formula ,i01 、i 02 The zero sequence currents of the two adjacent sections of arcing and arc extinguishing processes are respectively, wherein the sampling starting point k=1 is the initial moment, k is a sampling sequence, and N is the data length;
and the starting time judging module is used for judging specific starting time according to the similarity coefficient rho (n).
As a possible implementation manner of this embodiment, the starting point of the zero sequence voltage is 3 half waves, and 5 cycles before the 1 st half wave are used as starting points; and the zero sequence voltage judging end time point is used for ending 3 half waves, and the 3 rd half wave is ended.
As one possible implementation manner of this embodiment, the band-pass filtering processing module filters the direct current, the power frequency and the high frequency data in the zero-sequence current data by using an FIR 9-order band-pass filter with a passband frequency of 150Hz to 4000 Hz.
As a possible implementation manner of this embodiment, the calculation process of the zero crossing point is as follows:
setting sampling values of 2 sampling points adjacent to zero crossing points as A0 and A1 respectively, wherein the situation that the sampling point is just zero crossing point is regarded as a special situation that one of the A0 and A1 is zero;
the zero crossing point is determined according to the time relation between the sampling point and the zero point:
wherein ,
the interval time between the zero crossing point and the 2 nd sampling point is the sampling interval time.
As a possible implementation manner of this embodiment, the start time determining module is specifically configured to:
if the similarity coefficient ρ (n) is not less than 0.6, p (n) =1; if the similarity coefficient ρ (n) < 0.6, p (n) =0;
if p (n) =1 and p (n+1) =0 and p (n+2) =1, then F (n+1) is considered to be the arcing initial time point;
if p (n) =0 and p (n+1) =1 and p (n+2) =1, then F (n) is considered to be the arcing initial time point;
f (n+2) is considered to be the arcing initial time point if p (n) =1 and p (n+1) =1 and p (n+2) =0.
The technical scheme of the embodiment of the invention has the following beneficial effects:
according to the technical scheme, the fault wave recording data of the distribution cable are obtained, the fault starting time and the arcing time are accurately analyzed and calculated through the zero sequence voltage and the zero sequence current, and the accurate arcing time of the fault is obtained. The invention can accurately judge the arcing time of the cable fault and provide reliable data for effectively evaluating and early warning the state of the cable.
Drawings
FIG. 1 is a flowchart illustrating a method of calculating an initial point in time for arcing of a power distribution cable fault, according to an exemplary embodiment;
FIG. 2 is a schematic diagram of a computing device showing an initial point in time of arcing of a distribution cable fault, according to an example embodiment;
fig. 3 is a schematic diagram showing a relationship between a sampling point and a zero point in recorded data according to an exemplary embodiment.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
in order to clearly illustrate the technical features of the present solution, the present invention will be described in detail below with reference to the following detailed description and the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different structures of the invention. In order to simplify the present disclosure, components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and processes are omitted so as to not unnecessarily obscure the present invention.
As shown in fig. 1, the method for calculating the initial time point of fault arcing of a power distribution cable provided by the embodiment of the invention includes the following steps:
and step 1, acquiring single-phase earth fault wave recording data of the distribution line, wherein the single-phase earth fault wave recording data comprise zero sequence voltage and zero sequence current data.
And 2, judging the starting and ending time points of the faults through the zero sequence voltage. The starting time point of the zero sequence voltage is judged by using 3 half waves and 5 cycles before the 1 st half wave as starting points; and the zero sequence voltage judging end time point is used for ending 3 half waves, and the 3 rd half wave is ended.
And 3, extracting zero sequence current data between the starting time point and the ending time point of the fault, and carrying out band-pass filtering treatment. The band-pass filtering treatment is to filter direct current, power frequency and high frequency data in zero-sequence current data by adopting an FIR 9-order band-pass filter with the passband frequency of 150Hz to 4000Hz, and the maximum energy part of the electric arc is reserved.
Step 4, 1 section is arranged between two zero-sequence current zero-crossing points; and taking the data between 2 zero crossing points as 1 arcing and arc extinguishing processes, and marking the data as F (n), wherein n is more than or equal to 1, and n represents the nth arcing and arc extinguishing process.
The zero crossing point is calculated as follows:
as shown in fig. 3, the sampling values of 2 sampling points adjacent to the zero crossing point are set to be A0 and A1 respectively, and the zero crossing point is determined according to the time relation between the sampling point and the zero point:
wherein ,
between zero crossing and the 2 nd sampling pointInterval time, T is the sampling interval time.
Where t=tl0+tr0, TL0 is the time interval from the sampling point A0 to the zero crossing point, TR0 is the time interval from the sampling point A1 to the zero crossing point, the sampling point is negative below the zero axis, and positive above the zero axis.
If there is a case where the sampling point is exactly zero crossing, it is regarded as a special case where one of A0, A1 is zero.
Step 5, calculating waveform similarity coefficient ρ (n) of each segment F (n) of the filtered zero sequence current data with each other:
in the formula ,i01 、i 02 The zero sequence currents of the two adjacent sections of arcing and arc extinguishing processes are respectively, wherein the sampling starting point k=1 is the initial moment, k is a sampling sequence, and N is the data length;
the similarity coefficient ρ (n) reflects two fixed waveforms i 01 (k) And i 02 (k) Of which the value belongs to [0,1 ]]Interval. When the two signal waveforms are completely similar, ρ (n) takes a maximum of 1; when not similar, 0 is assumed.
And 6, judging specific starting time according to the similarity coefficient rho (n).
The step of judging the specific starting time according to the similarity coefficient ρ (n) comprises the following steps:
if the similarity coefficient ρ (n) is not less than 0.6, p (n) =1; if the similarity coefficient ρ (n) < 0.6, note that p (n) =0, p (n) is a number obtained by rounding up the similarity coefficient ρ (n);
if p (n) =1 and p (n+1) =0 and p (n+2) =1, then F (n+1) is considered to be the arcing initial time point;
if p (n) =0 and p (n+1) =1 and p (n+2) =1, then F (n) is considered to be the arcing initial time point;
f (n+2) is considered to be the arcing initial time point if p (n) =1 and p (n+1) =1 and p (n+2) =0.
As shown in fig. 2, a computing device for an initial point in time of fault arcing of a distribution cable according to an embodiment of the present invention includes:
the data acquisition module is used for acquiring single-phase earth fault wave recording data of the distribution line, wherein the single-phase earth fault wave recording data comprise zero sequence voltage and zero sequence current data;
the fault starting and stopping time point judging module is used for judging the starting and ending time points of the fault through the zero sequence voltage;
the band-pass filtering processing module is used for extracting zero sequence current data between the starting time point and the ending time point of the fault and carrying out band-pass filtering processing;
the arcing and arc extinguishing process determining module is used for determining 1 section between two zero crossing points of zero sequence current; taking the data between 2 zero crossing points as 1 arcing and arc extinguishing process, and marking the data as F (n), wherein n is more than or equal to 1, and n represents the nth arcing and arc extinguishing process;
the similarity coefficient calculation module is used for calculating waveform similarity coefficients rho (n) of each segment F (n) of the filtered zero-sequence current data with each other:
in the formula ,i01 、i 02 The zero sequence currents of the two adjacent sections of arcing and arc extinguishing processes are respectively, wherein the sampling starting point k=1 is the initial moment, k is a sampling sequence, and N is the data length;
and the starting time judging module is used for judging specific starting time according to the similarity coefficient rho (n).
As a possible implementation manner of this embodiment, the starting point of the zero sequence voltage is 3 half waves, and 5 cycles before the 1 st half wave are used as starting points; and the zero sequence voltage judging end time point is used for ending 3 half waves, and the 3 rd half wave is ended.
As a possible implementation manner of this embodiment, the band-pass filtering processing module filters dc, power frequency and high frequency data in the zero-sequence current data by using an FIR 9-order band-pass filter with passband frequency of 150Hz to 4000Hz, and retains the maximum energy portion of the arc.
As a possible implementation manner of this embodiment, the calculation process of the zero crossing point is as follows:
as shown in fig. 3, the sampling values of 2 sampling points adjacent to the zero crossing point are set to be A0 and A1 respectively, and the zero crossing point is determined according to the time relation between the sampling point and the zero point:
wherein ,
the interval time between the zero crossing point and the 2 nd sampling point is the sampling interval time.
If there is a case where the sampling point is exactly zero crossing, it is regarded as a special case where one of A0, A1 is zero.
The similarity coefficient ρ (n) reflects two fixed waveforms i 01 (k) And i 02 (k) Of which the value belongs to [0,1 ]]Interval. When the two signal waveforms are completely similar, ρ (n) takes a maximum of 1; when not similar, 0 is assumed.
As a possible implementation manner of this embodiment, the start time determining module is specifically configured to:
if the similarity coefficient ρ (n) is not less than 0.6, p (n) =1; if the similarity coefficient ρ (n) < 0.6, p (n) =0;
if p (n) =1 and p (n+1) =0 and p (n+2) =1, then F (n+1) is considered to be the arcing initial time point;
if p (n) =0 and p (n+1) =1 and p (n+2) =1, then F (n) is considered to be the arcing initial time point;
f (n+2) is considered to be the arcing initial time point if p (n) =1 and p (n+1) =1 and p (n+2) =0.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.
Claims (10)
1. The calculation method of the initial point in time of the fault arcing of the distribution cable is characterized by comprising the following steps:
step 1, acquiring single-phase earth fault wave recording data of a distribution line, wherein the single-phase earth fault wave recording data comprise zero sequence voltage and zero sequence current data;
step 2, judging the starting and ending time points of the faults through zero sequence voltages;
step 3, extracting zero sequence current data between the starting time point and the ending time point of the fault, and carrying out band-pass filtering treatment;
step 4, 1 section is arranged between two zero-sequence current zero-crossing points; taking the data between 2 zero crossing points as 1 arcing and arc extinguishing process, and marking the data as F (n), wherein n is more than or equal to 1, and n represents the nth arcing and arc extinguishing process;
step 5, calculating waveform similarity coefficient ρ (n) of each segment F (n) of the filtered zero sequence current data with each other:
in the formula ,i01 、i 02 The zero sequence currents of the two adjacent sections of arcing and arc extinguishing processes are respectively, wherein the sampling starting point k=1 is the initial moment, k is a sampling sequence, and N is the data length;
and 6, judging specific starting time according to the similarity coefficient rho (n).
2. The method for calculating the initial point of arcing for power distribution cable faults according to claim 1, wherein the initial point of zero sequence voltage judgment uses 3 half waves and 5 cycles before the 1 st half wave as the initial point.
3. The method for calculating the initial point in time of arcing of a power distribution cable fault according to claim 1, wherein the zero sequence voltage determination end point in time ends 3 half waves, and the 3 rd half wave ends.
4. A method for calculating a fault arcing initiation time point of a distribution cable according to claim 3, wherein the band-pass filtering is to filter direct current, power frequency and high frequency data in zero-sequence current data by using an FIR 9-order band-pass filter with a passband frequency of 150Hz to 4000 Hz.
5. The method for calculating the initial point in time of arcing of a power distribution cable fault according to claim 1, wherein the zero crossing point is calculated as follows:
setting sampling values of 2 sampling points adjacent to zero crossing points as A0 and A1 respectively, wherein the situation that the sampling point is just zero crossing point is regarded as a special situation that one of the A0 and A1 is zero;
the zero crossing point is determined according to the time relation between the sampling point and the zero point:
wherein ,
the interval time between the zero crossing point and the 2 nd sampling point is the sampling interval time.
6. The method for calculating a fault arcing initiation point of a distribution cable according to any of claims 1-5, wherein the determining a specific start time according to the similarity coefficient ρ (n) comprises:
if the similarity coefficient ρ (n) is not less than 0.6, p (n) =1; if the similarity coefficient ρ (n) < 0.6, p (n) =0;
if p (n) =1 and p (n+1) =0 and p (n+2) =1, then F (n+1) is considered to be the arcing initial time point;
if p (n) =0 and p (n+1) =1 and p (n+2) =1, then F (n) is considered to be the arcing initial time point;
f (n+2) is considered to be the arcing initial time point if p (n) =1 and p (n+1) =1 and p (n+2) =0.
7. A computing device for an initial point in time of arcing of a power distribution cable fault, comprising:
the data acquisition module is used for acquiring single-phase earth fault wave recording data of the distribution line, wherein the single-phase earth fault wave recording data comprise zero sequence voltage and zero sequence current data;
the fault starting and stopping time point judging module is used for judging the starting and ending time points of the fault through the zero sequence voltage;
the band-pass filtering processing module is used for extracting zero sequence current data between the starting time point and the ending time point of the fault and carrying out band-pass filtering processing;
the arcing and arc extinguishing process determining module is used for determining 1 section between two zero crossing points of zero sequence current; taking the data between 2 zero crossing points as 1 arcing and arc extinguishing process, and marking the data as F (n), wherein n is more than or equal to 1, and n represents the nth arcing and arc extinguishing process;
the similarity coefficient calculation module is used for calculating waveform similarity coefficients rho (n) of each segment F (n) of the filtered zero-sequence current data with each other:
in the formula ,i01 、i 02 The zero sequence currents of the two adjacent sections of arcing and arc extinguishing processes are respectively, wherein the sampling starting point k=1 is the initial moment, k is a sampling sequence, and N is the data length;
and the starting time judging module is used for judging specific starting time according to the similarity coefficient rho (n).
8. The computing device for the initial point in time of arcing of a power distribution cable fault according to claim 7, wherein the initial point in time of determination of the zero sequence voltage uses 3 half waves, 5 cycles before the 1 st half wave as the initial point; and the zero sequence voltage judging end time point is used for ending 3 half waves, and the 3 rd half wave is ended.
9. The apparatus according to claim 7, wherein the band-pass filter processing module filters direct current, power frequency and high frequency data in the zero-sequence current data by using an FIR 9-order band-pass filter with passband frequency of 150Hz to 4000 Hz.
10. The apparatus for calculating a fault arcing initiation point of a distribution cable according to any of the claims 7-9, wherein the start time determination module is specifically configured to:
if the similarity coefficient ρ (n) is not less than 0.6, p (n) =1; if the similarity coefficient ρ (n) < 0.6, p (n) =0;
if p (n) =1 and p (n+1) =0 and p (n+2) =1, then F (n+1) is considered to be the arcing initial time point;
if p (n) =0 and p (n+1) =1 and p (n+2) =1, then F (n) is considered to be the arcing initial time point;
f (n+2) is considered to be the arcing initial time point if p (n) =1 and p (n+1) =1 and p (n+2) =0.
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| CN117996702A (en) * | 2024-04-03 | 2024-05-07 | 山东交通学院 | Arc grounding fault protection method, system and storage medium for power distribution network |
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| CN117996702A (en) * | 2024-04-03 | 2024-05-07 | 山东交通学院 | Arc grounding fault protection method, system and storage medium for power distribution network |
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