CN114113897A - Single-phase earth fault line selection method based on power distribution network monitoring terminal - Google Patents
Single-phase earth fault line selection method based on power distribution network monitoring terminal Download PDFInfo
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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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The invention discloses a single-phase earth fault line selection method based on a power distribution network monitoring terminal, which comprises the following steps of: firstly, a network model is built at the head end position of each line of the power distribution network based on the power distribution network monitoring terminals, and the positive direction of current is distributed to each power distribution network monitoring terminal to point to the tail end of the line from a bus; continuously acquiring zero-sequence voltage and zero-sequence current based on each power distribution network monitoring terminal, and calculating the mutation direction of the fault components of the zero-sequence voltage and the zero-sequence current; comparing the zero-sequence voltage mutation direction and the zero-sequence current mutation direction of the current power distribution network monitoring terminal, if the mutation directions are the same and are set as 1, the mutation directions are set as-1 in opposite directions, and transmitting the mutation data to the adjacent power distribution network monitoring terminal through optical fiber communication; and fourthly, comparing the mutation data of the current power distribution network monitoring terminal and the adjacent power distribution network monitoring terminal to realize fault line selection. The method has simple and quick realization process and does not need precise time synchronization.
Description
Technical Field
The invention relates to the technical field of electric power automation, in particular to a single-phase earth fault line selection method based on a power distribution network monitoring terminal.
Background
The power distribution network is used as a bridge for connecting a power system and a user, and the power utilization quality and safety of the power user are determined by the operational reliability of the power distribution network. With the continuous progress of the economic society, the power distribution network shows the development trend of scale enlargement and complicated topological structure. When a single-phase earth fault occurs in the power distribution network, fault line selection and positioning and what protection measures are adopted are not well solved, and the requirement for reliable operation of the power distribution network cannot be met.
For the single-phase earth fault of the low-current earth system, the main positioning technologies widely adopted at present include: firstly, impedance method; secondly, a signal injection method; thirdly, zero sequence current comparison method; fourthly, a traveling wave method and the like.
Currently, there are three main types in the practical application of the fault location technology of the 10kV grounding system: the first is the "failure indicator" method; the second method is the "S" signal injection method; the third method is based on the distribution network automation technology, and utilizes a relay protector and a grounding line selection device to quickly disconnect a fault section, so as to ensure that the power supply of a fault-free part is recovered to normal operation. The defect is that the accurate position of the fault point cannot be determined, only an approximate range can be determined, and therefore manual inspection is needed to find the fault point.
After fault line selection and positioning are carried out, the fault is processed by adopting what measures, the requirement of stable and reliable operation of the system can be met, and the problem is not well solved.
Disclosure of Invention
The invention aims to provide a single-phase earth fault line selection method based on a power distribution network monitoring terminal, which can solve the problem of removing the single-phase earth fault of a power distribution network by utilizing a protection method based on an optical fiber communication technology and greatly improve the reliability of system operation.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a single-phase earth fault line selection method based on a power distribution network monitoring terminal comprises the following steps:
step 1: constructing a network model at the head end position of each line of the power distribution network based on the power distribution network monitoring terminals, and distributing the positive direction of current for each power distribution network monitoring terminal to point to the tail end of the line from a bus;
step 2: continuously acquiring zero-sequence voltage and zero-sequence current based on each power distribution network monitoring terminal, and calculating the mutation direction of the fault components of the zero-sequence voltage and the zero-sequence current;
the method for automatically filtering the imbalance component in normal operation comprises the following steps: starting by the zero-sequence current exceeding a fixed value, and obtaining a zero-sequence current signal of one whole period before the fault by advancing three whole periods from the starting moment of the fault, wherein the zero-sequence current signal is i1...inN is the number of sampling points of one period, and then, starting from the starting moment of the fault, i is correspondingly subtracted from the zero sequence current of each period1...inAnd the unbalanced component in normal operation can be automatically filtered.
The method has the advantages that the capacity of processing local time-frequency information through short-time Fourier transform and the advantages that different time-frequency resolutions are obtained through changing the width and the height of a time window in the wavelet transform, and the characteristic extraction amount is basically not influenced by noise. Compared with wavelet transform, S transform can adjust the width of window function along with frequency change, thereby obtaining richer time-frequency information and stronger anti-noise capability. The S transform of the continuous timing signal x (t) is:
wherein S isx(τ, f) is the S transformation of x (t), τ is the position control parameter of the gaussian window on the time axis t, and f is the frequency; ω (τ -t, f) is a Gaussian window function;
assuming that the continuous time sequence signals y (t) and x (t) have the same amplitude and opposite polarity, i.e. y (t) — x (t), are substituted into S transformation S of y (t)y(tau, f) is obtained
This equation shows that the polarity of the S-transition is opposite for two time series of opposite polarity.
And step 3: comparing the zero sequence voltage mutation direction and the zero sequence current mutation direction of the current power distribution network monitoring terminal, if the mutation directions are the same and are set as 1, and if the mutation directions are opposite and are set as-1, transmitting the mutation data to the adjacent power distribution network monitoring terminal through optical fiber communication;
and 4, step 4: comparing the mutation data of the current and adjacent power distribution network monitoring terminals to realize fault line selection;
the method comprises the following steps of comparing mutation data of the current power distribution network monitoring terminal and the adjacent power distribution network monitoring terminal to realize fault line selection, and specifically taking the following measures: the automatic terminal device with the detection and transmission functions is installed at the head end of each line, after S transformation is carried out on zero sequence current of the line, the mutation signals of adjacent detection devices are compared by using an optical fiber communication technology, and data transmission among a plurality of devices is realized.
The zero-sequence current mutation directions of two or more adjacent FTUs (digital transmission units) (DTUs) are compared based on an optical fiber communication technology, the power distribution network protection and area protection control functions are supported, a power distribution network protection system based on optical fiber communication is further constructed, rapid and accurate fault location of a power distribution network is achieved, and the operation reliability of the power distribution network is effectively improved.
The invention has the beneficial effects that:
the method and the device can be suitable for the condition that the single-phase earth fault occurs during the operation of the power distribution network, can realize the processing of the single-phase earth fault occurring in the power distribution network, and effectively improve the operation reliability of the power distribution network.
And secondly, the optical fiber communication has the characteristics of large communication capacity, long transmission distance, electromagnetic interference resistance and good transmission quality. The optical fiber has small size and light weight, and is convenient to lay and transport.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a flow chart of a fault diagnosis technique of the present invention.
Fig. 2 is a schematic diagram of a transient equivalent circuit of a single-phase earth fault occurring when a neutral point of a power distribution network is not effectively grounded.
Fig. 3 is a simulation model of a single-phase earth fault occurring when a neutral point of a power distribution network is not effectively grounded.
Fig. 4 is a zero-sequence voltage waveform diagram and a waveform diagram after S conversion.
Fig. 5 is a waveform diagram of the zero sequence current of the first detection device and a waveform diagram after S transformation.
Fig. 6 is a zero sequence current waveform diagram and a waveform diagram after S transformation of the second detection device.
Detailed Description
As shown in fig. 1, a single-phase earth fault line selection method based on a power distribution network monitoring terminal information integration technology includes the following steps:
step S01: constructing a network model at the head end position of each line of the power distribution network based on the power distribution network monitoring terminals, distributing the positive direction of current for each power distribution network monitoring terminal from a bus to the tail end of the line, constructing the network model based on the positions of the power distribution network monitoring terminals in each line of the power distribution network, and distributing the positive direction of current for each power distribution network monitoring terminal;
step S02: continuously acquiring zero-sequence voltage and zero-sequence current based on each power distribution network monitoring terminal, calculating the sudden change direction of the fault component of the zero-sequence voltage and the zero-sequence current based on each power distribution network monitoring terminal, continuously acquiring the zero-sequence current, and calculating the sudden change direction of the fault component of the zero-sequence current;
opening Matlab, introducing zero sequence current of the line, and carrying out S transformation on the oscillogram;
step S03: comparing the zero-sequence voltage mutation direction and the zero-sequence current mutation direction of the current power distribution network monitoring terminal, if the mutation directions are the same and set as 1, the mutation directions are set as-1 in opposite directions, sending the mutation data to the adjacent power distribution network monitoring terminal through optical fiber communication, comparing the current positive current direction and the mutation directions of the power distribution network monitoring terminal to obtain current mutation data, and sending fault request current mutation data to the upstream and downstream power distribution network monitoring terminals when the current positive current direction and the current mutation directions are inconsistent;
after S transformation is carried out, the zero sequence current mutation direction is compared through the information transmitted by the optical fiber signals, and the step S04 is carried out;
step S04: and comparing the sudden change data of the current power distribution network monitoring terminal and the adjacent power distribution network monitoring terminal to realize fault line selection.
First embodiment, as shown in fig. 2, fig. 2 is a schematic diagram of a transient equivalent circuit of a single-phase earth fault occurring when a neutral point of a power distribution network is not effectively grounded.
In fig. 2, the line four is a fault line, and a detection device is installed at the head end of each line. Respectively, detection devices one, two, three and four.
According to the method, the ATP-EMTP software is utilized to simulate the single-phase earth fault of the non-effective earth of the neutral point of the power distribution network to diagnose and verify the fault.
For the single-phase earth fault caused by the non-effective earthing of the neutral point of the power distribution network, the single-phase earth fault route selection method based on the power distribution network monitoring terminal information integration technology can be adopted, and the single-phase earth fault route positioning can be completed after the current detection devices are installed at the head ends of all the lines in a circuit such as the circuit shown in figure 2.
The specific implementation steps are shown in fig. 1.
Step 1: constructing a network model at the head end position of each line of the power distribution network based on the power distribution network monitoring terminals, distributing the positive direction of current for each power distribution network monitoring terminal from a bus to the tail end of the line, constructing the network model based on the positions of the power distribution network monitoring terminals in each line of the power distribution network, distributing the positive direction of current for each power distribution network monitoring terminal, and entering the step 2;
step 2: continuously acquiring zero-sequence voltage and zero-sequence current based on each power distribution network monitoring terminal, calculating the sudden change direction of the fault component of the zero-sequence voltage and the zero-sequence current based on each power distribution network monitoring terminal, continuously acquiring the zero-sequence current, and calculating the sudden change direction of the fault component of the zero-sequence current;
opening Matlab, introducing zero sequence current of the line, and carrying out S transformation on the oscillogram;
and step 3: comparing the zero-sequence voltage mutation direction and the zero-sequence current mutation direction of the current power distribution network monitoring terminal, if the mutation directions are the same and set as 1, the mutation directions are set as-1 in opposite directions, sending the mutation data to the adjacent power distribution network monitoring terminal through optical fiber communication, comparing the current positive current direction and the mutation directions of the power distribution network monitoring terminal to obtain current mutation data, and sending fault request current mutation data to the upstream and downstream power distribution network monitoring terminals when the current positive current direction and the current mutation directions are inconsistent;
after S transformation is carried out, the information transmitted through the optical fiber signal is compared with the direction of the zero sequence current mutation, and the step 4 is carried out;
and 4, step 4: and comparing the sudden change data of the current power distribution network monitoring terminal and the adjacent power distribution network monitoring terminal to realize fault line selection.
According to the above experimental procedure, the experimental results were as follows:
in fig. 4, the upper part is a zero sequence voltage waveform diagram, and the lower part is a mutation direction after S conversion;
in fig. 5, the upper part is a zero sequence current waveform diagram of the first detection device, and the lower part is a mutation direction after S transformation;
in fig. 6, the upper part is a zero sequence current waveform diagram of the second detection device, and the lower part is a mutation direction after S transformation;
the zero sequence voltage and the direction of the sudden change are shown in fig. 4. The direction of the sudden change of the zero-sequence current detected by the first detection device of the line four can be determined to be opposite to the direction of the sudden change of the zero-sequence voltage, as shown in fig. 5, namely the data of the detection device 1 is-1, and the direction of the sudden change of the zero-sequence current detected by the second detection device is the same as the direction of the sudden change of the zero-sequence voltage, as shown in fig. 6, namely the data of the second detection device, the data of the third detection device and the data of the fourth detection device are +1, and the direction of the sudden change of the zero-sequence current and the direction of the zero-sequence current of the adjacent detection devices are compared through optical fiber signals to complete fault line selection.
The above disclosure is only for the specific embodiment of the present patent, but the present patent is not limited thereto, and it should be understood that the modifications made by those skilled in the art without departing from the principle of the present invention shall fall within the protection scope of the present invention.
Claims (4)
1. A single-phase earth fault line selection method based on a power distribution network monitoring terminal is characterized by comprising the following steps:
s01, constructing a network model at the head end position of each line of the power distribution network based on the power distribution network monitoring terminals, and distributing the positive direction of current for each power distribution network monitoring terminal to point from the bus to the tail end of the line;
s02, continuously collecting zero-sequence voltage and zero-sequence current based on each power distribution network monitoring terminal, and calculating the sudden change direction of the fault components of the zero-sequence voltage and the zero-sequence current;
s03, comparing the zero-sequence voltage mutation direction and the zero-sequence current mutation direction of the current power distribution network monitoring terminal, if the mutation directions are the same and set as 1, the mutation directions are set as-1 in opposite directions, and sending the mutation data to the adjacent power distribution network monitoring terminal through optical fiber communication;
and S04, comparing the data based on the sudden change of the current and the adjacent power distribution network monitoring terminals to realize fault line selection.
2. The single-phase earth fault line selection method based on the power distribution network monitoring terminal as claimed in claim 1, wherein step S02 includes filtering out unbalanced components in normal operation, and the method is as follows: starting by the zero-sequence current exceeding a fixed value, and obtaining a zero-sequence current signal of one whole period before the fault by advancing three whole periods from the starting moment of the fault, wherein the zero-sequence current signal is i1...inN is the number of sampling points of one period, and then, starting from the starting moment of the fault, i is correspondingly subtracted from the zero sequence current of each period1...inAnd the unbalanced component in normal operation can be automatically filtered.
3. The single-phase earth fault line selection method based on the power distribution network monitoring terminal as claimed in claim 1 or 2, wherein the step S02 includes S transformation, and S transformation of the continuous timing signal x (t) is:
wherein S isx(τ, f) is the S transformation of x (t), τ is the position control parameter of the gaussian window on the time axis t, and f is the frequency; ω (τ -t, f) is a Gaussian window function;
assuming that the continuous time sequence signals y (t) and x (t) have the same amplitude and opposite polarity, i.e. y (t) — x (t), are substituted into S transformation S of y (t)y(tau, f) is obtained
This equation shows that the polarity of the S-transition is opposite for two time series of opposite polarity.
4. The single-phase earth fault line selection method based on the power distribution network monitoring terminal as claimed in claim 3, wherein in step S04, the fault line selection is implemented by comparing the current and adjacent abrupt change data of the power distribution network monitoring terminal, an automatic terminal device with detection and signaling functions is installed at the head end of each line, and after S transformation of the zero sequence current of the line, the abrupt change signals of the adjacent detection devices are compared by using optical fiber communication technology, so as to implement mutual data transmission among a plurality of devices.
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- 2021-11-29 CN CN202111433167.3A patent/CN114113897A/en active Pending
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| CN101587159A (en) * | 2009-06-22 | 2009-11-25 | 昆明理工大学 | Power distribution network outgoing feeder fault route selecting method by S transform amplitude detection |
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