CN116736039A - Comprehensive evaluation system for single-phase earth fault line selection of power distribution network - Google Patents
Comprehensive evaluation system for single-phase earth fault line selection of power distribution network Download PDFInfo
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Abstract
The application provides a comprehensive evaluation system for single-phase earth fault line selection of a power distribution network, which comprises a fault recorder, a data acquisition server and a fault analysis and information release server, wherein the fault recorder is connected with the data acquisition server; based on the rough set theory, carrying out criterion analysis on six existing line selection methods, determining an effective domain of the line selection methods, giving weight coefficients of the methods, selecting a correct line selection method, and carrying out accurate line selection on single-phase ground faults; the application applies the rough set algorithm to the low-current grounding system and determines the condition attribute of the line selection method based on the recording data, thereby further realizing multi-criterion fusion and improving the reliability of line selection.
Description
Technical Field
The application belongs to the technical field of power system ground faults, and particularly relates to accurate line selection for single-phase ground faults of a power distribution network.
Background
At present, domestic distribution lines have large coverage area, long lines and more branches, and the running environment is quite complex. With national policy guidance and urban development and construction, distribution network cabling continues to grow at a speed of approximately 10%, and the probability of faults is greatly increased. It is counted that 70% of the faults occurring in the distribution network system are caused directly or indirectly by single-phase earth faults and are accompanied by burning or breakdown of in-station equipment due to overvoltage. Therefore, diagnosis and analysis are urgently needed to be carried out on the running state of the power distribution network line, and accurate line selection is realized when single-phase earth faults occur, so that the fault removal time is shortened, the large-area power failure risk is reduced, and the service life of equipment in a station is prolonged.
At present, an independent low-current grounding line selection device is not additionally arranged in most substations, and the investment is huge if the device is comprehensively modified and additionally arranged. The existing station monitoring background refreshes and uploads the system data of the power distribution network by adopting a voltage and current deflection mechanism of 2 thousandths, but the system is mainly used for collecting system steady state information, the data sampling precision is not high, and a self-contained line selection functional module of the monitoring background also only uses a group ratio amplitude-phase method suitable for steady state line selection. When single-phase earth faults occur, the arc suppression coils work in an overcompensation state, the line selection accuracy is not high by utilizing a steady state, and zero sequence current signals in a plurality of stations are not connected into a monitoring background, and the capability of background calculation and data storage can not meet the line selection requirement of high field accuracy. In the prior art, in the field of small-current line selection, no line selection method can be effective for all fault types, and the method in the prior art is to simply fuse various fault characteristic quantities or give out the weight of the line selection method through expert subjective judgment, so that the method is not accurate and objective.
Disclosure of Invention
Aiming at the problems in the prior art, the application provides a comprehensive evaluation system for single-phase earth fault line selection of a power distribution network, provides fault characteristic quantities (condition attributes) under different line selection methods, fuses and judges a plurality of fault characteristic quantities, uses a rough set algorithm, determines the effective domain of each line selection method compared with the prior art by solving the problems through experience, provides a weight formula for line selection, judges whether the line selection method is correct or not, and has better improvement on the accuracy of line selection.
The technical scheme of the application is as follows:
the comprehensive evaluation system for single-phase earth fault line selection of the power distribution network comprises a fault recorder, a data acquisition server and a fault analysis and information release server;
the fault recorder takes zero sequence voltage value out-of-limit or single-phase voltage reduction out-of-limit as a fault recording starting index to record waves by a single-phase grounding fault triggering mechanism of the recorder; collecting recording data of fault wave recorders in all transformer substations, and obtaining sampling data of the fault wave recorders;
the method comprises the steps that sampling data of a fault recorder are transmitted to a data set acquisition server, the data set acquisition server extracts fault recording data conforming to a single-phase grounding fault triggering mechanism to obtain extracted data, and the extracted data are transmitted to a grounding information fault analysis and information release server for analysis after unidirectional isolation;
the fault analysis and information release server analyzes the extracted data based on a rough set algorithm to obtain different line selection methods, judges the correctness of single-phase grounding fault detection of a small-current grounding system of the power distribution network of the transformer substation, and compares weights of the different line selection methods to obtain a line selection result.
Preferably, the sampled data includes bus zero sequence voltage, phase voltage and zero sequence current.
The sampling data is transmitted to a data collection server based on the optical fiber network resource as a data channel.
The data collection server is provided with a pre-recorder data collection server, the data collection server and the pre-recorder data collection server conduct data interaction, the fault recorder accesses sampling data to a communication manager of an intra-station dispatching data network through an Ethernet port, the communication interaction is conducted with the pre-recorder data collection server, and the pre-recorder data collection server is used for caching the sampling data.
The fault analysis and information release server is configured with an independent server, the data collection server and the fault analysis and information release server adopt a data unidirectional transmission mechanism, and a unidirectional isolation and power system special firewall is configured, so that the security of a data network is ensured while the data transmission of remote signaling, remote measurement, fault wave recording and the like among the data collection server, the fault analysis and information release server is realized.
The fault analysis and information release server analyzes the extracted data based on a rough set algorithm to obtain the calculated value of the condition attribute of each line selection method: the conditional attribute comprises fundamental zero sequence current average valueFundamental zero sequence current phase difference pho and transition resistance R 1 Harmonic wave and fundamental wave content ratio v, fifth harmonic wave content f and zero sequence current amplitude I 0 Zero sequence current phase difference I pho The energy function value of all lines before the fault, the energy function value of the fault line, the energy function value of the non-fault line, the voltage first half-wave amplitude U, the transient zero-sequence current direction L and the phase difference U of the voltages when the fault occurs pho Transition resistance R 2 Zero sequence voltage curve instantaneous slope K when fault occurs 1 Zero sequence voltage curve average slope K when fault occurs 2 。
Transition resistance R 1 Transition resistance R 2 。
The comprehensive evaluation of line selection specifically comprises the following steps:
s1, establishing a condition attribute definition table of a line selection method;
s2, calculating a calculated value of the condition attribute of each route selection method based on the extracted data;
s3, based on calculated values of condition attributes of the line selection methods, comparing a condition attribute definition table of the line selection methods to obtain coded values of the condition attributes of the line selection methods, and based on the coded values of the condition attributes, analyzing a group ratio amplitude-phase method, a harmonic ratio amplitude-phase method, a steady-state wavelet method, an energy method, a first half-wave method and a transient wavelet method through a rough set mathematical algorithm to obtain effective thresholds corresponding to the line selection methods.
The step S1 specifically comprises the following steps:
the line selection method comprises a group ratio amplitude-phase method, a harmonic ratio amplitude-phase method, a steady-state wavelet method, an energy method, a first half-wave method and a transient wavelet method for analysis;
the sample object of the line selection comprehensive evaluation is a line when a fault occurs, d1 in the decision attribute indicates that the fault line can be correctly selected, and d2 indicates that the fault line cannot be correctly selected.
The conditional attribute of the group ratio amplitude-phase method is fundamental wave zero sequence current average valueFundamental zero sequence current phase difference pho and transition resistance R 1 ；
The conditional attribute of the harmonic ratio amplitude-phase method is harmonic and fundamental wave content ratio v and fifth harmonic content f;
the condition attribute of the steady-state wavelet method is zero sequence current amplitude I 0 Zero sequence current phase difference I pho ；
The condition attributes of the energy method are all line energy function values q, fault line energy function values w and non-fault line energy function values e before fault;
the condition attribute of the first half-wave method is voltage first half-wave amplitude U, transient zero sequence current direction L and phase difference of voltage U when faults occur pho ；
The transient wavelet method has the condition attribute of transition resistance R 2 Zero sequence voltage curve instantaneous slope K when fault occurs 1 Zero sequence voltage curve average slope K when fault occurs 2 。
The conditional attribute definition table of the line selection method is table 1:
table 1 conditional attribute definition table of line selection method
The calculation formulas of the energy function value q of all lines before the fault, the energy function value w of the fault line and the energy function value e of the non-fault line are as follows:
q＝∫U′ 1 I′ 1 dt，w＝∫U′ 2 I′ 2 dt，e＝∫U′ 3 I′ 3 dt, U' 1 And I' 1 The zero sequence voltage and the zero sequence current of the line before the fault are respectively U' 2 And I' 2 The zero sequence voltages and currents of the fault line are respectively U' 3 And I' 3 Zero sequence voltages and currents, respectively, of non-faulty lines；
Zero sequence voltage curve instantaneous slope K when fault occurs 1 And zero sequence voltage curve average slope K when fault occurs 2 The calculation formula is thatU t Represents the zero sequence voltage, T at the T sampling moment when the fault occurs t A time point representing the t-th sampling time; t=1, 2 ln, n+1 sampling points in total.
The effective thresholds corresponding to the line selection methods are as follows:
the effective threshold of the amplitude-phase method is in the range ofph0 < 9 degrees;
the effective domain range of the harmonic ratio amplitude-phase method is that the ratio v of the fifth harmonic to the fundamental wave content is more than 0.1, and the fifth harmonic content f is more than 4kV;
the range of the effective threshold of the steady-state wavelet method is zero sequence current amplitude I 0 > 6A zero sequence current phase difference I pho Less than 10 degrees;
the range of the energy method effective threshold is that the energy function value q of all lines before failure is more than 0, the energy function value w of the failed line is less than 0, and the energy function value e of the non-failed line is more than 0;
the value of the effective domain of the first half-wave method is that the voltage first half-wave amplitude U=38.1 kv; when the first half-wave of the short-circuit current is opposite to the direction of the non-fault phase, the transient zero-sequence current direction L is taken to be-1, otherwise, is taken to be-1, and the phase voltage phase difference U is generated when the fault occurs pho Less than 10 degrees;
the range of the effective domain of the transient wavelet method is K 1 ＞10,K 2 ＞8。
Respectively assigning weight coefficients to the line selection methods based on the effective domain, wherein the weight coefficients represent the credibility of the corresponding line selection methods, and the weight coefficients are calculated through a weight formula;
w i ＝w i1 ×w i2 ×L w in
ω i the weight coefficient of the ith line selection method; omega ij Is the ith kindThe correlation coefficient of the method and the j-th condition attribute (fault feature quantity) is selected. In the course of line selection, the condition attribute (fault feature quantity) c ij And a threshold C of the effective threshold ij Comparing to obtain a line selection result; c (C) ij A threshold value representing the effective threshold of the condition attribute of each line selection method, when the condition attribute c ij Satisfy the corresponding effective threshold range omega ij =1, if not, take c ij /C ij The method comprises the steps of carrying out a first treatment on the surface of the In the course of selecting line, the condition attribute is compared with the threshold value of effective threshold, if ω is satisfied ij =1, which indicates correct line selection, if ω ij Not equal to 1, indicating a line selection failure.
Compared with the prior art, the application has the following beneficial effects:
the application discloses a comprehensive evaluation system for single-phase earth fault line selection of a power distribution network, which provides fault characteristic quantities (condition attributes) under different line selection methods, fuses and judges a plurality of fault characteristic quantities, uses a rough set algorithm to determine the effective domain of each line selection method compared with the prior art by solving the problem through experience, provides a weight formula of line selection, judges whether the line selection method is correct or not, and has better improvement on the accuracy of line selection.
The application uses the existing dispatching optical fiber network resource as a data link channel, carries out single-phase earth fault line selection by a comprehensive evaluation method, and gives a weight ratio; the technical scheme of the application has the capability of simultaneously monitoring the system states of the distribution network of at least 100 substations, and can bring the distribution network lines in the whole urban area into the monitoring range. According to the scheme, existing equipment resources in the station are effectively utilized, single-phase earth faults of the low-current grounding system of the distribution network of each transformer substation are monitored, centralized and unified management of grounding fault information can be achieved, dispatching operation maintenance personnel can conveniently master the operation condition of a line, and pre-fault assessment is carried out on hidden danger of the line fault in advance.
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Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:
FIG. 1 is a diagram of a comprehensive evaluation system for single-phase earth fault line selection of a power distribution network;
FIG. 2 is a flow chart of a comprehensive evaluation system for single-phase earth fault line selection of a power distribution network;
fig. 3 is a diagram of a configuration of a single record file.
Detailed Description
The following description of the embodiments of the present application will be made more apparent and fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the application are shown. All other embodiments, which can be made by one of ordinary skill in the art without undue burden on the person of ordinary skill in the art based on embodiments of the present application, are within the scope of the present application.
As shown in fig. 1, the comprehensive evaluation system for single-phase earth fault line selection of the power distribution network comprises a fault recorder, a data acquisition server and a fault analysis and information release server;
the fault recorder takes zero sequence voltage value out-of-limit or single-phase voltage reduction out-of-limit as a fault wave recording starting index to record waves by a single-phase grounding fault triggering mechanism of the recorder, and the wave sampling rate is 5kHz or 10kHz; and acquiring recording data of fault recorders in all transformer substations to obtain sampling data of the fault recorders, wherein the sampling data comprise bus zero sequence voltage, phase voltage and zero sequence current.
The method comprises the steps of transmitting sampled data of a fault recorder to a data set acquisition server, extracting fault recording data conforming to a single-phase grounding fault triggering mechanism by the data set acquisition server to obtain extracted data, and transmitting the extracted data to a grounding information fault analysis and information release server (grounding information server) for analysis after unidirectional isolation.
The fault analysis and information release server analyzes the extracted data based on a rough set algorithm to obtain different line selection methods, judges the correctness of single-phase grounding fault detection of the low-current grounding system of the power distribution network of the transformer substation, and performs weight comparison on the different line selection methods to obtain line selection results and provide line selection information for dispatching maintenance personnel.
The sampling data is transmitted to a data collection server based on the optical fiber network resource as a data channel.
The data collection server is provided with a pre-recorder data collection server, the data collection server and the pre-recorder data collection server conduct data interaction, the fault recorder accesses sampling data to a communication manager (switch) of an intra-station dispatching data network (optical fiber/dispatching data network) through an Ethernet port, the communication interaction is conducted with the pre-recorder data collection server, and the pre-recorder data collection server is used for caching the sampling data.
The fault analysis and information release server is configured with an independent server, and the fault analysis and information release server is arranged in three areas so as to facilitate the outward display release of the grounding information. The data collection server and the fault analysis and information release server adopt a data unidirectional transmission mechanism, and a unidirectional isolation and power system special firewall is configured, so that the security of a data network is ensured while the data transmission of remote signaling, remote measurement, fault wave recording and the like among the data collection server, the fault analysis and information release servers is realized.
The fault analysis and information release server analyzes the extracted data based on a rough set algorithm to obtain the calculated value of the condition attribute of each line selection method: the conditional attribute comprises fundamental zero sequence current average valueFundamental zero sequence current phase difference pho and transition resistance R 1 Harmonic wave and fundamental wave content ratio v, fifth harmonic wave content f and zero sequence current amplitude I 0 Zero sequence current phase difference I pho The energy function value of all lines before the fault, the energy function value of the fault line, the energy function value of the non-fault line, the voltage first half-wave amplitude U, the transient zero-sequence current direction L and the phase difference U of the voltages when the fault occurs pho Transition resistance R 2 Zero sequence voltage curve instantaneous slope K when fault occurs 1 Zero sequence voltage curve average slope K when fault occurs 2 。
Transition resistance R 1 Transition resistance R 2 。
The fault analysis and information release server analyzes the data information through a rough set algorithm, the rough set algorithm effectively analyzes and processes the data information such as inaccuracy, incompleteness and the like, and extracts effective information by searching a data relationship rule, and the effective information is processed in a simple way.
The rough set theory is analyzed by writing a decision table in columns, wherein the decision table is a two-dimensional table, each row represents one sample object, and each column represents sample attributes. The sample attribute is divided into a condition attribute and a decision attribute, the sample object refers to a line selected when a fault occurs, wherein the condition attribute refers to parameters affecting line selection accuracy in a specific method, namely a, b and c in the following table, and the decision attribute refers to judgment of a described object. Table 1 is an original decision table, wherein the domain U has 9 sample objects, the numbers of the sample objects are recorded as 1-8, a, b and c are all conditional attributes, and d is a decision attribute. It is further noted that not all conditional attributes are necessary, and that individual attributes do not affect the change of decision attributes after removal, then the attributes are referred to as redundant attributes and may be omitted. Reduction is defined as the minimum set of conditional attributes that do not contain redundant attributes and ensure that classification is correct. There may be multiple shortcuts to the decision table whose intersection is defined as core.
The rough set algorithm is applied to a low-current grounding system, and the effective domain (the effective threshold of the fault characteristic quantity) of the condition attribute of the line selection method is determined based on the recording data, so that multi-criterion fusion is further realized, and the reliability of line selection is improved. The line selection method comprises an intelligent group ratio amplitude-phase method, a harmonic ratio amplitude-phase method, a steady-state wavelet method, an energy method, a first half-wave method and a transient wavelet method
As shown in fig. 2, the line selection comprehensive evaluation specifically includes the following steps:
s1, establishing a condition attribute definition table of a line selection method;
the line selection method comprises a group ratio amplitude-phase method, a harmonic ratio amplitude-phase method, a steady-state wavelet method, an energy method, a first half-wave method and a transient wavelet method for analysis;
the sample object of the line selection comprehensive evaluation is a line when a fault occurs, d1 in the decision attribute indicates that the fault line can be correctly selected, and d2 indicates that the fault line cannot be correctly selected.
The conditional attribute of the group ratio amplitude-phase method is fundamental wave zero sequence current average valueFundamental zero sequence current phase difference pho and transition resistance R 1 ；
The conditional attribute of the harmonic ratio amplitude-phase method is harmonic and fundamental wave content ratio v and fifth harmonic content f;
the condition attribute of the steady-state wavelet method is zero sequence current amplitude I 0 Zero sequence current phase difference I pho ；
The condition attribute of the energy method is all line energy function values before failure, failure line energy function values and non-failure line energy function values;
the condition attribute of the first half-wave method is voltage first half-wave amplitude U, transient zero sequence current direction L and phase difference of voltage U when faults occur pho ；
The transient wavelet method has the condition attribute of transition resistance R 2 Zero sequence voltage curve instantaneous slope K when fault occurs 1 Zero sequence voltage curve average slope K when fault occurs 2 。
The conditional attribute definition table of the line selection method is table 1:
in the group ratio amplitude-phase method, (1) fundamental wave zero sequence current average value(the unit is A) the value is 0-5, and the code 1 corresponds to the value; the value of 5-10 corresponds to the code 2, and the value of 10-15 corresponds to the code 3; (2) The fundamental wave zero sequence current phase difference pho takes the value of 0 to 3 corresponding to codes 0,3 to 6 corresponding to codes 1,6 to 9 corresponding to codes 2, more than 9 corresponding to codes 3; (3) Transition resistance size R 1 (Ω): 0 corresponds to code 1, 30 corresponds to code 2, 120 corresponds to code 3.
In the harmonic ratio amplitude-phase method, (1) ratio q of fifth harmonic to fundamental wave content: corresponding to codes 0,0.05-0.1 of 0-0.05 and corresponding to codes 1, and corresponding to codes 2 of 0.1-0.15; (2) fifth harmonic content f: the codes 0-2 correspond to the codes 0, the codes 2-4 correspond to the codes 1 and the codes 2 above 4.
Steady stateIn the wavelet method, (1) zero sequence current amplitude I 0 : 0-3 corresponding codes 0, 3-6 corresponding codes 1, 6-9 corresponding codes 2; (2) Zero sequence current phase difference I pho : 20-30 corresponding codes 0, 10-20 corresponding codes 1, 0-10 corresponding codes 2, and the decision table has only one decision attribute, and the line selection method correctly corresponds to d 1 Error corresponds to d 2 。
Table 1 conditional attribute definition table of line selection method
The calculation formulas of the energy function value q of all lines before the fault, the energy function value w of the fault line and the energy function value e of the non-fault line are as follows:
q＝∫U′ 1 I′ 1 dt，w＝∫U′ 2 I′ 2 dt，e＝∫U′ 3 I′ 3 dt, U' 1 And I' 1 The zero sequence voltage and the zero sequence current of the line before the fault are respectively U' 2 And I' 2 The zero sequence voltages and currents of the fault line are respectively U' 3 And I' 3 Zero sequence voltage and current of a non-fault line respectively;
'line' refers to all lines that are recorded by the fault recorder. "Pre-failure" refers to before the time of failure.
Zero sequence voltage curve instantaneous slope K when fault occurs 1 And zero sequence voltage curve average slope K when fault occurs 2 The calculation formula is thatU t Represents the zero sequence voltage, T at the T sampling moment when the fault occurs t A time point representing the t-th sampling time; t=1, 2 ln, n+1 sampling points in total. .
S2, calculating a calculated value of the condition attribute of each route selection method based on the extracted data;
s3, based on the calculated value of the condition attribute of each line selection method, comparing the condition attribute definition table of the line selection method to obtain the code value of the condition attribute of each line selection method,
based on the coding values of the condition attributes, analyzing a group ratio amplitude-phase method, a harmonic ratio amplitude-phase method, a steady-state wavelet method, an energy method, a first half-wave method and a transient wavelet method by a rough set mathematical algorithm to obtain effective thresholds corresponding to each line selection method;
TABLE 2 method 1 population ratio amplitude-phase method
From the four groups of samples obtained in Table 2, when d is d1, the effective threshold of the amplitude-phase method is obtained, and the fundamental wave zero sequence current average value is obtainedThe code value of the fundamental wave zero sequence current phase difference pho is 2,2 and 2, and the code value of the fundamental wave zero sequence current phase difference pho is 3,2 and 1; based on the rough set mathematical algorithm, the effective threshold of the amplitude-versus-phase method is: fundamental zero sequence current average->The code of fundamental zero-sequence current phase difference pho is less than 3, the condition attribute definition table of the corresponding line selection method is corresponding to the effective threshold range of the specific amplitude-phase method is +.>ph0 < 9 degrees;
TABLE 3 method 2 harmonic ratio amplitude-phase method
The harmonic ratio amplitude-phase method effective domain is obtained from table 3: the coding of the ratio v of the fifth harmonic wave to the fundamental wave is more than 1, the coding of the fifth harmonic wave content f is more than 2, and after the conversion of a condition attribute definition table according to a line selection method, the range of the effective domain of the harmonic wave ratio amplitude-phase method is more than 0.1, and the fifth harmonic wave content f is more than 4 kilovolts;
table 4 method 3 steady state wavelet method
The effective domain of the steady state wavelet method is obtained from Table 4 as zero sequence current amplitude I 0 Code of (1), zero sequence current phase difference I pho After conversion of the conditional attribute definition table according to the line selection method, the range of the effective threshold of the steady-state wavelet method is I 0 ＞6A，I pho Less than 10 degrees;
TABLE 5 method 4 energy method
The effective domain of the energy method is that the energy function value calculated by the energy method is only two, more than 0 or less than 0, so that the obtained fault characteristic quantity only needs to be compared with 0. Therefore, after conversion according to the condition attribute definition table of the line selection method, the range of the energy method effective threshold is that the energy function value q of all lines before failure is more than 0, the energy function value w of the failed line is less than 0, and the energy function value e of the non-failed line
Greater than 0. TABLE 6 method 5 first half wave method
The value of the effective domain of the first half-wave method is obtained from table 6, namely the voltage first half-wave amplitude u=38.1 kv; when the first half wave of the short-circuit current is not the faultThe directions of the barrier phases are opposite, the transient zero sequence current direction L is taken to be-1, otherwise, 1 is taken, and the phase voltage phase difference U is generated when a fault occurs pho Less than 10 degrees;
table 7 method 6 transient wavelet method
The range of the effective domain of the transient wavelet method from Table 7 is K 1 ＞10,K 2 ＞8。
In order to realize multi-criterion fusion, respectively endowing the six line selection methods with weight coefficients on the basis of an effective domain, wherein the weight coefficients represent the credibility of the corresponding line selection methods, and the weight coefficients are calculated through a weight formula;
w i ＝w i1 ×w i2 ×L w in
ω i the weight coefficient of the ith line selection method; omega ij The correlation coefficient of the i-th selection method and the j-th condition attribute (fault feature quantity) is used. In the course of line selection, the condition attribute (fault feature quantity) c ij And a threshold C of the effective threshold ij Comparing to obtain a line selection result; c (C) ij A threshold value representing the effective threshold of the condition attribute of each line selection method, when the condition attribute c ij Satisfy the corresponding effective threshold range omega ij =1, if not, take c ij /C ij The method comprises the steps of carrying out a first treatment on the surface of the In the course of selecting line, the condition attribute is compared with the threshold value of effective threshold, if ω is satisfied ij =1, which indicates correct line selection, if ω ij Not equal to 1, indicating a line selection failure, the line selection result in this embodiment is table 8.
Table 8 line selection result table
| Line selection method | Group ratio amplitude-phase method | Harmonic ratio amplitude-phase method | Steady state wavelet method | Energy method | First half wave method | Transient wavelet method |
| Line selection result | Correct and correct | Errors | Errors | Correct and correct | Correct and correct | Correct and correct |
And (3) comparing weights of different line selection methods, performing high-accuracy single-phase earth fault line selection, and finally displaying a line selection result on a power distribution network system monitoring interface in real time and pushing the line selection result to operation and maintenance management personnel in the form of alarm information (SOE).
The 66kV transformer substation 86 seat in the power supply jurisdiction of the embodiment is provided with a transformer substation 62 seat of a fault recorder, the fault recorder is a transformer substation 15 seat of a Linux system, and is provided with a transformer substation 56 seat of zero sequence CT, so that a transformer substation 13 seat of an access system is met. In this example, 994 10kV distribution lines are permanently grounded 138 times in 2020 and 55 times in 2021. The transformer substation meeting the access system is permanently grounded 21 times in 2020 and 10 times in 2021.
The fault recorder is arranged in the inspection station, and as the 10kV system in the transformer substation is brought into the fault wave recording monitoring range in the plan, the bus zero-sequence voltage, the phase voltage and the zero-sequence current signals are connected into the fault recorder, the independent zero-sequence current transformer is preferentially used for directly collecting the zero-sequence current signals, and the phase current transformer is adopted for synthesizing the zero-sequence current signals. And (3) taking zero sequence voltage value out-of-limit or single-phase voltage reduction out-of-limit as a fault wave recording starting index to record waves by a single-phase grounding fault trigger mechanism of the wave recorder, wherein the wave sampling rate is 5kHz or 10kHz.
At present, a pre-recorder data acquisition server is arranged in the two areas, and the wave recording data of each in-station recorder is firstly sent to the server. And a data collection server is arranged in the second area, and the newly arranged data collection server performs data interaction with a data collection server of a prepositioned wave recorder arranged in the second area of the existing mountain high power. The wave recorder is accessed into an intra-station dispatching data (optical fiber) network communication manager or switch through an Ethernet port, performs communication interaction with a pre-wave recorder data acquisition server, and sends data to the mountain high-power pre-wave recorder data acquisition server; the data acquisition server of the pre-recorder forwards the data to a newly-arranged data set acquisition server, and the newly-arranged data set acquisition server extracts fault recording data which accords with a single-phase grounding fault triggering mechanism.
The fault information and information release server is arranged in the three areas so as to facilitate the outward display release of the grounding information. The data collection server and the release information server adopt a data unidirectional transmission mechanism, and a unidirectional isolation and a special firewall for an electric power system are required to be configured, so that the security of a data network is ensured while the data transmission of two-zone and three-zone remote signaling, remote measurement, fault wave recording and the like is realized. The server obtains remote signaling data containing primary system information and fault alarm information (wave recording occurrence), wave recording data containing information such as bus phase voltage, zero sequence current and the like of the power distribution network, comprehensively processes the data, then utilizes a built-in line selection algorithm to perform high-accuracy single-phase earth fault line selection, and finally presents a line selection result on a monitoring interface of the power distribution network system in real time and pushes the line selection result to operation and maintenance management staff in the form of alarm information (SOE).
In the embodiment, the in-station fault recorder is used as a data source, the zero sequence voltage value out-of-limit or the single-phase voltage reduction out-of-limit is used as a fault recording starting index, and the single-phase grounding fault trigger mechanism of the recorder is used for recording waves, wherein the waveform sampling rate is 5kHz or 10kHz. To verify the line selection availability of the fault log file, the following two tests were performed.
The embodiment adopts a 380V physical simulation platform waveform file test, and the 380V physical simulation platform simulates a 10.5kV power distribution network system by using an AC380V, and is used for researching and testing interphase short circuit, single-phase grounding, ferromagnetic resonance and series resonance under different grounding modes of neutral points of the power distribution network system. The platform is provided with 1 section of bus and 4 outgoing lines, wherein the line 1 and the line 2 are respectively divided into 3 sections, and single-phase grounding fault points can be respectively arranged. The platform is provided with an arc suppression coil, and can simulate the single-phase earth faults of a neutral point ungrounded system or a metallic transition resistance with different resistance values, high resistance and arc light in the arc suppression coil ungrounded system of the power distribution network. And collecting waveforms before and after the fault moment of the platform system in the single-phase earth fault test. The recorder has 96 analog signal input channels, the sampling rate is 12.8kHz, the recording time length is 2.34s, and the size of a single fault recording file is 6.2M. The neutral point is grounded by an arc suppression coil, and metallic, 7.5 omega, 15 omega, 30 omega, 60 omega, 120 omega, 180 omega, 240 omega and 300 omega (corresponding to a 10.5kV system, namely metallic, 207 omega, 414 omega, 828 omega, 1656 omega, 3312 omega, 4968 omega, 6631 omega and 8289 omega) single-phase grounding fault tests are carried out on the platform during test, and each type of single-phase grounding fault test is carried out twice. The test set line 1 is used as a single-phase earth fault line, and metallic, 30Ω and 120Ω resistance single-phase earth fault recorder waveforms are selected as examples for fault analysis. The configuration of the single record file is shown in fig. 3, wherein the dat file is a waveform data file.
Because the original wave recording file is large, all channel waveforms are checked, a general combtrade 99 waveform checking tool is used for opening, and after the metallic single-phase grounding fault is opened, the wave recording time length and each channel is recorded to the waveform during the metallic single-phase grounding fault test are seen.
The method is characterized in that effective data extraction is directly carried out on an original waveform file by using wave recording inversion software, and after extraction, waveforms of 5 cycles (100 ms) before the fault moment and 9 cycles (180 ms) after the fault moment are intercepted, wherein the sampling rate of the waveforms is still 12.8kHz.
Through wave recording inversion analysis, a single-phase earth fault line, metallic, 30Ω and 120Ω resistance single-phase earth faults are identified, and six analysis methods are used, namely an intelligent group ratio amplitude-phase method, a harmonic ratio amplitude-phase method, a steady-state wavelet method, an energy method, a first half-wave method and a transient wavelet method. Each line selection method has the range of the respective effective domain, and different line selection results are respectively obtained to accurately select the fault line (line I)
In the embodiment, a single-phase grounding fault occurs in a 220kV clean positive transformer 66kV system, and a fault line is a clean double-A line.
The on-site recorder has 160 analog signal input channels, the sampling rate is 4kHz, the recording time length is about 7.68s, and the size of a single fault recording file is about 6M. Because the original wave recording file is larger, all channel waveforms are opened and checked by using a combtrade 99 waveform checking tool, and wave recording time length and wave recording waveforms of all channels before and after single-phase grounding faults occur are obtained.
And correcting waveform inversion software configuration files according to the data acquired by the corresponding wave recording channel, directly extracting effective data from the original waveform files by utilizing the wave recording inversion software, and after the effective data are extracted, retaining the phase voltage, zero sequence voltage and each outgoing line zero sequence current waveform of the original waveform 66kV system, and also intercepting waveforms of 5 cycles (100 ms) before the fault moment and 9 cycles (180 ms) after the fault moment, wherein the sampling rate is unchanged.
Through wave recording inversion analysis, a single-phase grounding fault line can be identified as a 66kV net double-A line, and in the inversion analysis process, the wave form sampling rate is 6kHz after analysis processing by using a line selection method and the weights of the methods are the same.
Through the test of the single-phase ground fault wave recording file of the 380V physical simulation platform wave recorder and the actual inversion of the wave file of the on-site wave recorder, the scheme can be seen to correctly select the single-phase ground fault line and give the weights of various line selection methods.
The method comprises the steps of taking an in-station recorder as a data source, taking the existing dispatching optical fiber network resource as a data link channel, carrying out single-phase grounding fault line selection by a comprehensive evaluation method on the basis, and giving a weight ratio. The technical scheme of the application has the capability of simultaneously monitoring the system states of the distribution network of at least 100 substations, and can bring the distribution network lines in the whole urban area into the monitoring range. According to the scheme, existing equipment resources in the station are effectively utilized, single-phase earth faults of the low-current grounding system of the distribution network of each transformer substation are monitored, centralized and unified management of grounding fault information can be achieved, dispatching operation maintenance personnel can conveniently master the operation condition of a line, and pre-fault assessment is carried out on hidden danger of the line fault in advance.
Thus far, the technical solution of the present application has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present application is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present application, and such modifications and substitutions will fall within the scope of the present application.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the application may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be construed as reflecting the intention that: i.e., the claimed application requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this application.
Those skilled in the art will appreciate that the modules or units or groups of devices in the examples disclosed herein may be arranged in a device as described in this embodiment, or alternatively may be located in one or more devices different from the devices in this example. The modules in the foregoing examples may be combined into one module or may be further divided into a plurality of sub-modules.
Those skilled in the art will appreciate that the modules in the apparatus of the embodiments may be adaptively changed and disposed in one or more apparatuses different from the embodiments. The modules or units or groups of embodiments may be combined into one module or unit or group, and furthermore they may be divided into a plurality of sub-modules or sub-units or groups. Any combination of all features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or units of any method or apparatus so disclosed, may be used in combination, except insofar as at least some of such features and/or processes or units are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.
Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.
Furthermore, some of the embodiments are described herein as methods or combinations of method elements that may be implemented by a processor of a computer system or by other means of performing the functions. Thus, a processor with the necessary instructions for implementing the described method or method element forms a means for implementing the method or method element. Furthermore, the elements of the apparatus embodiments described herein are examples of the following apparatus: the apparatus is for carrying out the functions performed by the elements for carrying out the objects of the application.
The various techniques described herein may be implemented in connection with hardware or software or, alternatively, with a combination of both. Thus, the methods and apparatus of the present application, or certain aspects or portions of the methods and apparatus of the present application, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium, wherein, when the program is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the application.
In the case of program code execution on programmable computers, the computing device will generally include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. Wherein the memory is configured to store program code; the processor is configured to perform the method of the application in accordance with instructions in said program code stored in the memory.
By way of example, and not limitation, computer readable media comprise computer storage media and communication media. Computer-readable media include computer storage media and communication media. Computer storage media stores information such as computer readable instructions, data structures, program modules, or other data. Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. Combinations of any of the above are also included within the scope of computer readable media.
As used herein, unless otherwise specified the use of the ordinal terms "first," "second," "third," etc., to describe a general object merely denote different instances of like objects, and are not intended to imply that the objects so described must have a given order, either temporally, spatially, in ranking, or in any other manner.
While the application has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of the above description, will appreciate that other embodiments are contemplated within the scope of the application as described herein. Furthermore, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. The disclosure of the present application is intended to be illustrative, but not limiting, of the scope of the application, which is defined by the appended claims.
Claims (10)
1. The comprehensive evaluation system for single-phase earth fault line selection of the power distribution network is characterized by comprising a fault recorder, a data acquisition server and a fault analysis and information release server;
the fault recorder takes zero sequence voltage value out-of-limit or single-phase voltage reduction out-of-limit as a fault recording starting index to record waves by a single-phase grounding fault triggering mechanism of the recorder; collecting recording data of fault wave recorders in all transformer substations, and obtaining sampling data of the fault wave recorders;
the method comprises the steps that sampling data of a fault recorder are transmitted to a data set acquisition server, the data set acquisition server extracts fault recording data conforming to a single-phase grounding fault triggering mechanism to obtain extracted data, and the extracted data are transmitted to a grounding information fault analysis and information release server for analysis after unidirectional isolation;
the fault analysis and information release server analyzes the extracted data based on a rough set algorithm, judges the accuracy of single-phase grounding fault detection of a small-current grounding system of the power distribution network of the transformer substation, and compares weights of different line selection methods to obtain a line selection result.
2. The power distribution network single-phase earth fault line selection comprehensive assessment system according to claim 1, wherein the sampled data comprises bus zero sequence voltage, phase voltage and zero sequence current.
3. The comprehensive evaluation system for single-phase earth fault line selection of a power distribution network according to claim 1, wherein the sampled data is transmitted to a data collection server based on optical network resources as a data channel.
4. The comprehensive evaluation system for single-phase earth fault line selection of the power distribution network according to claim 3, wherein the data collection server is provided with a pre-recorder data collection server, the data collection server performs data interaction with the pre-recorder data collection server, the fault recorder accesses sampling data to a communication manager of an intra-station dispatching data network through an Ethernet port, performs communication interaction with the pre-recorder data collection server, and the pre-recorder data collection server is used for caching the sampling data.
5. The comprehensive evaluation system for single-phase earth fault line selection of power distribution network according to claim 3, wherein the fault analysis and information release server is configured with an independent server, the data collection server and the fault analysis and information release server adopt a data unidirectional transmission mechanism, and a unidirectional isolation and power system special firewall is configured.
6. The comprehensive evaluation system for single-phase earth fault line selection of a power distribution network according to claim 3, wherein,
the fault analysis and information release server analyzes the extracted data based on a rough set algorithm to obtain the calculated value of the condition attribute of each line selection method; the conditional attribute comprises fundamental zero sequence current average valueFundamental zero sequence current phase difference pho and transition resistance R 1 Harmonic wave and fundamental wave content ratio v, fifth harmonic wave content f and zero sequence current amplitude I 0 Zero sequence current phase difference I pho All line energy function values before failure, the energy function value of the failure line, the energy function value of the non-failure line, the first half-wave amplitude U of voltage and temporaryPhase zero sequence current direction L and phase voltage phase difference U when fault occurs pho Transition resistance R 2 Zero sequence voltage curve instantaneous slope K when fault occurs 1 Zero sequence voltage curve average slope K when fault occurs 2 ；
Transition resistance R 1 Transition resistance R 2 。
7. The comprehensive evaluation system for single-phase earth fault line selection of a power distribution network according to claim 1, wherein,
the comprehensive evaluation of line selection specifically comprises the following steps:
s1, establishing a condition attribute definition table of a line selection method;
s2, calculating a calculated value of the condition attribute of each route selection method based on the extracted data;
s3, based on calculated values of condition attributes of the line selection methods, comparing a condition attribute definition table of the line selection methods to obtain coded values of the condition attributes of the line selection methods, and based on the coded values of the condition attributes, analyzing a group ratio amplitude-phase method, a harmonic ratio amplitude-phase method, a steady-state wavelet method, an energy method, a first half-wave method and a transient wavelet method through a rough set algorithm to obtain effective thresholds corresponding to the line selection methods.
8. The comprehensive evaluation system for single-phase earth fault line selection of a power distribution network according to claim 7, wherein,
the step S1 specifically comprises the following steps:
the sample object of the line selection comprehensive evaluation is a line when a fault occurs, d1 in the decision attribute represents correctly selecting the fault line, and d2 represents incorrectly selecting the fault line;
the conditional attribute of the group ratio amplitude-phase method is fundamental wave zero sequence current average valueFundamental zero sequence current phase difference pho and transition resistance R 1 ；
The conditional attribute of the harmonic ratio amplitude-phase method is harmonic and fundamental wave content ratio v and fifth harmonic content f;
the condition attribute of the steady-state wavelet method is zero sequence current amplitude I 0 Zero sequence current phase difference I pho ；
The condition attributes of the energy method are all line energy function values q, fault line energy function values w and non-fault line energy function values e before fault;
the condition attribute of the first half-wave method is voltage first half-wave amplitude U, transient zero sequence current direction L and phase difference of voltage U when faults occur pho ；
The transient wavelet method has the condition attribute of transition resistance R 2 Zero sequence voltage curve instantaneous slope K when fault occurs 1 Zero sequence voltage curve average slope K when fault occurs 2 ；
The calculation formulas of the energy function value q of all lines before the fault, the energy function value w of the fault line and the energy function value e of the non-fault line are as follows:
q＝∫U′ 1 I′ 1 dt，w＝∫U' 2 I' 2 dt，e＝∫U′ 3 I′ 3 dt, U' 1 And I' 1 The zero sequence voltage and the zero sequence current of the line before the fault are respectively U' 2 And I' 2 The zero sequence voltages and currents of the fault line are respectively U' 3 And I' 3 Zero sequence voltage and current of a non-fault line respectively;
zero sequence voltage curve instantaneous slope K when fault occurs 1 And zero sequence voltage curve average slope K when fault occurs 2 The calculation formula is thatU t Represents the zero sequence voltage, T at the T sampling moment when the fault occurs t A time point representing the t-th sampling time; t=1, 2 ln, n+1 sampling points in total.
9. The comprehensive evaluation system for single-phase earth fault line selection of a power distribution network according to claim 7, wherein,
the effective thresholds corresponding to the line selection methods are as follows:
the effective threshold of the amplitude-phase method is in the range ofph0 < 9 degrees;
the range of the effective domain of the harmonic ratio amplitude-phase method is that the ratio v of the content of fifth harmonic waves and fundamental waves is more than 0.1, and the content f of fifth harmonic waves is more than 4kv;
the range of the effective threshold of the steady-state wavelet method is zero sequence current amplitude I 0 > 6A zero sequence current phase difference I pho Less than 10 degrees;
the range of the energy method effective threshold is that the energy function value q of all lines before failure is more than 0, the energy function value w of the failed line is less than 0, and the energy function value e of the non-failed line is more than 0;
the value of the effective domain of the first half-wave method is that the voltage first half-wave amplitude U=38.1 kv; when the first half-wave of the short-circuit current is opposite to the direction of the non-fault phase, the transient zero-sequence current direction L is taken to be-1, otherwise, is taken to be-1, and the phase voltage phase difference U is generated when the fault occurs pho ＜10；
The range of the effective domain of the transient wavelet method is K 1 ＞10，K 2 ＞8。
10. The comprehensive evaluation system for single-phase earth fault line selection of the power distribution network according to claim 9, wherein weight coefficients are respectively assigned to the line selection methods based on an effective domain, the weight coefficients represent the credibility of the corresponding line selection methods, and the weight coefficients are calculated through a weight formula;
w i ＝w i1 ×w i2 ×Lw in
ω i the weight coefficient of the ith line selection method; omega ij A correlation coefficient between the ith selection method and the jth conditional attribute; in the process of selecting the line, the condition attribute c ij And a threshold C of the effective threshold ij Comparing to obtain a line selection result; c (C) ij A threshold value representing the effective threshold of the condition attribute of each line selection method, when the condition attribute c ij Satisfy the corresponding effective threshold range omega ij =1, if not, ω is taken ij ＝c ij /C ij The method comprises the steps of carrying out a first treatment on the surface of the In the process of selecting linesIf omega is satisfied ij =1, which indicates correct line selection, if ω ij Not equal to 1, the line selection fails.
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