CN114791546A - System and method for detecting fault position in power distribution system - Google Patents
System and method for detecting fault position in power distribution system Download PDFInfo
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- CN114791546A CN114791546A CN202210455212.3A CN202210455212A CN114791546A CN 114791546 A CN114791546 A CN 114791546A CN 202210455212 A CN202210455212 A CN 202210455212A CN 114791546 A CN114791546 A CN 114791546A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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Abstract
The invention discloses a system and a method for detecting fault positions in a power distribution system. The fault monitoring unit monitors the occurrence of line faults, determines a fault line through the line selection module after the occurrence of the faults to finish fault rough selection, and the distance measurement module acquires fault positioning signals.
Description
Technical Field
The invention belongs to the field of power systems, and particularly relates to a system and a method for detecting a fault position in a power distribution system.
Background
The power distribution system is the last stage of the power system to deliver the electric energy to the user, and the reliability of the power distribution system has a direct influence on the use experience of the user. The safe operation and the power supply reliability of the power distribution system are particularly important and are also important attention objects of the power department. According to incomplete statistics, more than 80% of faults transmitted by a power distribution system are single-phase earth faults, while the earth mode of a medium-voltage and low-voltage power distribution network in China mainly comprises neutral point ungrounded faults and neutral point arc suppression coils grounded, when the single-phase earth faults occur, the fault current of a loop formed by the system is small, the system also becomes a low-current earth system, the system can operate with the faults for a period of time, although the system can operate with the faults for a short time, overvoltage can be caused when the faults are not removed for a long time, breakdown of the fault points can be caused, the fault range can be enlarged, and the like, so that equipment damage is further caused, and the personal safety is endangered. When a single-phase fault occurs in the low-current grounding system, the fault current is low, and the low-current grounding fault is difficult to quickly and accurately position due to the fact that the number of nodes in the power distribution network is large and the line structure is complex.
Disclosure of Invention
The invention provides a system for detecting fault positions in a power distribution system, aiming at the problem that a low-current ground fault is difficult to quickly and accurately position. The system for detecting the fault position in the power distribution system comprises a control center, a communication network, a fault monitoring unit and a fault positioning unit, wherein the fault positioning unit comprises a line selection module and a distance measurement module, the fault monitoring unit is arranged on a bus, the fault positioning unit is arranged on a feeder and is close to the connection position of the bus and the feeder, and the control center is in communication connection with the fault monitoring unit and the fault positioning unit through the communication network.
Optionally, the fault monitoring unit monitors three-phase currents of the system, and determines that the system has a fault when determining that zero-sequence current and negative-sequence current exist according to the three-phase currents.
Optionally, the fault monitoring unit sends a fault warning to the control center when determining that the system sends a fault, and the control center sends a fault positioning instruction to all the fault positioning units based on the received fault warning.
Optionally, the fault location unit determines a fault line through the line selection module based on the fault location instruction, acquires a fault location signal through the ranging module corresponding to the fault line, and sends the fault location signal to a control center to determine a fault location.
A method for detecting a location of a fault in an electrical distribution system is also provided. The method is applied to a system for detecting the fault position in a power distribution system, and comprises the following steps:
s1: monitoring three-phase current of a bus, and determining that a single-phase earth fault occurs in the system when zero-sequence current and negative-sequence current exist according to the three-phase current;
s2: when the single-phase earth fault occurs, detecting three-phase voltage on the feeder line, performing line selection operation on the feeder line, and determining a fault line;
s3: and injecting detection waves into the fault line, simultaneously acquiring echo signals, and positioning the fault according to the acquired echo signals.
Optionally, the line selection operation specifically includes: and determining that the line corresponding to the phase with the voltage drop to zero to the ground is a fault line according to the three-phase voltage.
Optionally, the fault location according to the acquired echo signal specifically includes: and starting to collect echo signals while injecting detection waves, carrying out signal processing on the collected echo signals, determining the time t corresponding to the time from injecting the detection waves to receiving the echo signals, and calculating the position of the fault according to the time t and the reference wave velocity v.
Optionally, the signal processing comprises:
s31, performing wavelet transformation on the echo signal by taking the measuring wave as a wavelet basis function to obtain the echo signal S
s＝d 1 +d 2 +d 3 +d 4 +d 5 +a 5 ；
Wherein d is 1 -d 5 For the decomposed 5 signal components, a 5 Is the residual component;
s32, calculating the kurtosis value of each signal component, and adopting 2-5 signal components with the largest kurtosis value to reconstruct into a plurality of reconstructed signals;
and S33, calculating the kurtosis value of each reconstructed signal, and taking the reconstructed signal with the maximum kurtosis value as an echo reconstructed signal.
Optionally, the kurtosis value calculation formula is:
where μ is the mean of the discrete signal x, n is the number of samples within the signal x, x i The sample value of the ith sample point in the signal x.
Optionally, the detection wave is characterized by
h(t)＝Ψ 3 (t)，
Where Ψ (t) is a Meyer wavelet.
Compared with the prior art, the invention has the beneficial effects that:
(1) the fault detection is carried out on the line based on the zero sequence current and the negative sequence current of the bus, so that the fault condition can be rapidly monitored; meanwhile, the fault positioning unit is started only when the fault monitoring unit monitors a fault, so that the energy consumption can be reduced, and the service life of the detection device can be prolonged;
(2) after a fault occurs, a fault line is quickly determined based on three-phase grounding voltage on a feeder line, and the fault range can be roughed in time;
(3) aiming at the determined fault line, a fault positioning signal is obtained by adopting a detection wave injection method, and the fault positioning signal is analyzed by a wavelet analysis method based on a kurtosis value, so that the accuracy of fault positioning is improved.
Drawings
FIG. 1 is a system diagram of the present invention for detecting the location of a fault in an electrical distribution system;
FIG. 2 is a block diagram of a fault locating unit;
FIG. 3 is a schematic diagram of a ranging module for fault line detection;
FIG. 4 is a waveform diagram of Meyer wavelet;
fig. 5 is a schematic diagram of wavelet decomposition according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The first embodiment:
FIG. 1 is a system diagram of the present invention for detecting the location of a fault in an electrical distribution system. Fig. 2 is a block diagram of a fault location unit.
The utility model provides a system for be arranged in detecting distribution system trouble position, includes control center, communication network, trouble monitoring unit and trouble positioning unit, trouble positioning unit includes route selection module and range finding module, trouble monitoring unit sets up on the bus, trouble positioning unit sets up on the feeder and is close to bus and feeder junction, control center pass through communication network respectively with trouble monitoring unit with trouble positioning unit communication connection.
In the 6-66kV power supply and distribution network of China, the operation mode of a low-current grounding system is adopted. When single-phase grounding occurs to the system, only the distribution of zero sequence voltage and current of the system is changed, and other obvious fault characteristics are not provided. When in normal operation, the three-phase earth capacitances are equal, and the three-phase voltages are balanced and symmetrical; after the single-phase earth fault occurs, the voltage of the fault relative to the earth is reduced to zero, and the voltage of the non-fault relative to the earth is increased to be the line voltage.
Preferably, the fault monitoring unit monitors three-phase currents of the system, and determines that the system has a fault when determining that zero-sequence current and negative-sequence current exist according to the three-phase currents.
Preferably, the fault monitoring unit sends a fault warning to the control center when determining that the system sends a fault, and the control center sends a fault positioning instruction to all the fault positioning units based on the received fault warning. The fault positioning unit starts the line selection module and the distance measurement module based on the received fault positioning instruction, so that the power consumption can be reduced, and the service life of the monitoring module is prolonged.
Fig. 3 is a schematic diagram of the ranging module detecting a faulty line. The fault positioning unit further comprises a processing module and a communication module, the processing module is in signal connection with the line selection module, the distance measurement module and the communication module respectively, and the processing module receives and processes signals collected by the line selection module to determine a fault line. The distance measurement module comprises an injection module and a receiving module, the injection module is used for receiving a control instruction of the processing module so as to inject detection waves into corresponding lines, the receiving module synchronously starts to acquire echo signals when the detection waves are injected into the injection module according to the control instruction, and the echo signals are fault positioning signals representing fault positioning information. The processing module sends the echo signals received by the receiving module to the control center through the communication module, and the control center processes and analyzes the echo signals to determine the fault position.
Preferably, the fault location unit determines a fault line through the line selection module based on the fault location instruction, acquires a fault location signal through the ranging module corresponding to the fault line, and sends the fault location signal to a control center to determine a fault location.
The second embodiment:
a method for detecting the position of a fault in a power distribution system is provided, which is applied to a system for detecting the position of the fault in the power distribution system, and comprises the following steps:
s1: monitoring three-phase current of a bus, and determining that a single-phase earth fault occurs in the system when zero-sequence current and negative-sequence current exist according to the three-phase current;
s2: when the single-phase earth fault occurs, detecting three-phase voltage on the feeder line, performing line selection operation on the feeder line, and determining a fault line;
s3: and injecting detection waves into the fault line, simultaneously acquiring echo signals, and positioning the fault according to the acquired echo signals.
Preferably, the line selection operation specifically includes: and determining the line corresponding to the phase with the voltage drop to zero as a fault line according to the three-phase voltage.
Preferably, the fault location according to the acquired echo signal specifically includes: and starting to collect echo signals while injecting detection waves, carrying out signal processing on the collected echo signals, determining the time t corresponding to the time from injecting the detection waves to receiving the echo signals, and calculating the position of the fault according to the time t and the reference wave velocity v.
The method comprises the following steps that traveling wave velocity in a line of the power distribution network is related to various factors, when the power distribution system is normal, a test line with a known distance L is tested through a ranging module, test time t0 required by transmission of test waves in the line with a set distance is obtained, and the wave velocity of the test line is calculated according to the known distance L and the test time t 0; according to the characteristics of the power distribution system, a plurality of test lines are selected in a targeted manner, and the test process is repeated to obtain a plurality of test wave speeds. And averaging the plurality of test wave speeds to serve as a reference wave speed v of the power distribution system.
Preferably, the signal processing includes:
s31, performing wavelet transformation on the echo signal by taking the measuring wave as a wavelet basis function to obtain the echo signal S
s＝d 1 +d 2 +d 3 +d 4 +d 5 +a 5 ；
Wherein d is 1 -d 5 For the decomposed 5 signal components, a 5 Is the residual component;
s32, calculating the kurtosis value of each signal component, and reconstructing the signal components with the maximum kurtosis value into a plurality of reconstructed signals by adopting 2-5 signal components;
and S33, calculating the kurtosis value of each reconstructed signal, and taking the reconstructed signal with the maximum kurtosis value as an echo reconstructed signal.
Preferably, the detection wave is h (t) ═ Ψ 3 (t), where Ψ (t) is a Meyer wavelet.
Fig. 4 is a waveform diagram of a Meyer wavelet. Fig. 5 is a schematic diagram of wavelet decomposition according to the present invention. The wavelet function and the scale function of the Meyer wavelet are defined in the frequency domain, and have tightly-supported orthogonality. Therefore, Meyer wavelet is used as basic wavelet to construct detection wave h (t) ═ Ψ 3 And (t) injecting the detection wave into the fault line to be used as an excitation signal for signal detection, and simultaneously using the detection wave as a wavelet basis function for wavelet change processing of the received echo signal.
The kurtosis is a dimensionless parameter for describing the kurtosis of a waveform, is particularly sensitive to an impact signal, and is used for detecting the pulse signal.
Preferably, the kurtosis value K of each signal component is calculated by adopting a kurtosis value calculation formula of discrete signals; the kurtosis value of the signal x is calculated as:
where μ is the mean of the discrete signal x, n is the number of samples within the signal x, x i The sample value of the ith sample point in the signal x.
The above description is only exemplary of the present invention and should not be taken as limiting, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The system for detecting the fault position in the power distribution system is characterized by comprising a control center, a communication network, a fault monitoring unit and a fault positioning unit, wherein the fault positioning unit comprises a line selection module and a distance measurement module, the fault monitoring unit is arranged on a bus, the fault positioning unit is arranged on a feeder and is close to the joint of the bus and the feeder, and the control center is in communication connection with the fault monitoring unit and the fault positioning unit through the communication network respectively.
2. The system for detecting a location of a fault in an electrical distribution system of claim 1 wherein the fault monitoring unit monitors three phase currents of the system and determines that the system is faulty if it is determined from the three phase currents that zero sequence current and negative sequence current are present.
3. The system of claim 2, wherein the fault monitoring unit sends a fault warning to the control center when the system determines that a fault has been sent, and the control center sends fault locating instructions to all of the fault locating units based on the fault warning received.
4. The system of claim 3, wherein the fault locating unit determines a fault line through the line selection module based on the fault locating command, acquires a fault locating signal through the ranging module corresponding to the fault line, and sends the fault locating signal to a control center to determine a fault location.
5. A method for detecting the location of a fault in an electrical distribution system, for use in a system for detecting the location of a fault in an electrical distribution system according to any of claims 1 to 4,
s1: monitoring three-phase current of a bus, and determining that the system has a single-phase earth fault when determining that zero sequence current and negative sequence current exist according to the three-phase current;
s2: when the single-phase earth fault occurs, detecting three-phase voltage on the feeder line, performing line selection operation on the feeder line, and determining a fault line;
s3: and injecting detection waves into the fault line, simultaneously acquiring echo signals, and positioning the fault according to the acquired echo signals.
6. The positioning method according to claim 5, wherein the line selection operation specifically includes: and determining the line corresponding to the phase with the voltage dropped to zero as a fault line according to the three-phase voltage.
7. Method for detecting the location of a fault in an electrical distribution system according to claim 6, characterized in that the fault is localized according to the collected echo signals, in particular: and starting to collect echo signals while injecting detection waves, carrying out signal processing on the collected echo signals, determining the time t corresponding to the time from injecting the detection waves to receiving the echo signals, and calculating the position of the fault according to the time t and the reference wave velocity v.
8. The method of claim 7, wherein the signal processing comprises:
s31, performing wavelet transformation on the echo signal by taking the measuring wave as a wavelet basis function to obtain the echo signal S
s＝d 1 +d 2 +d 3 +d 4 +d 5 +a 5 ；
Wherein d is 1 -d 5 For the decomposed 5 signal components, a 5 Is the residual component;
s32, calculating the kurtosis value of each signal component, and adopting 2-5 signal components with the largest kurtosis value to reconstruct the kurtosis value into a plurality of reconstructed signals;
and S33, calculating the kurtosis value of each reconstructed signal, and taking the reconstructed signal with the maximum kurtosis value as an echo reconstructed signal.
9. A method for detecting a location of a fault in an electrical distribution system as claimed in claim 8, wherein said kurtosis value is calculated by:
where μ is the mean of the discrete signal x, n is the number of samples within the signal x, x i The sample value of the ith sample point in the signal x.
10. The method of claim 9, wherein the detection wave is a wave of radiation
h(t)＝Ψ 3 (t)，
Where Ψ (t) is a Meyer wavelet.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116381418A (en) * | 2023-06-05 | 2023-07-04 | 国网天津市电力公司电力科学研究院 | Power grid line fault positioning method and system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116381418A (en) * | 2023-06-05 | 2023-07-04 | 国网天津市电力公司电力科学研究院 | Power grid line fault positioning method and system |
| CN116381418B (en) * | 2023-06-05 | 2023-10-03 | 国网天津市电力公司电力科学研究院 | Power grid line fault positioning method and system |
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