CN116359674A - Active power distribution network fault positioning method and system based on fault transient signals - Google Patents
Active power distribution network fault positioning method and system based on fault transient signals Download PDFInfo
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Abstract
The invention discloses a fault transient signal-based active power distribution network fault positioning method and system, and belongs to the field of relay protection of power systems. The method comprises the steps of generating faults of an active power distribution network, immediately starting a fault line selection device, selecting a fault feeder line containing a distributed power supply, calculating transient pure fault components of zero-mode current of the fault feeder line at each reachable node through a distributed feeder line automation device installed at each reachable node；Extracting 2ms before failure and 5ms after failure data of zero-mode current transient pure fault components of all reachable nodes, and enhancing the amplitude of the zero-mode current transient pure fault components by using a Teager energy operator; calculating the energy duty ratio histogram of each processed reachable node zero-mode current transient pure fault component; and calculating the similarity of the energy duty ratio histograms of all adjacent reachable nodes, and carrying out fault location on the active power distribution network system according to the similarity. The fault positioning method is accurate and reliable.
Description
Technical Field
The invention relates to a fault transient signal-based active power distribution network fault positioning method and system, and belongs to the field of relay protection of power systems.
Background
Along with the connection of a large number of distributed power supplies with a power distribution network by adopting inverters and the like, the flexibility of the power distribution network is improved, and meanwhile, the operation control difficulty of the power distribution network is increased. A large number of distributed photovoltaics and distributed wind power are put into operation, so that power dispatching is required to be changed from traditional 'source follow-up' to 'source load interaction', and the plurality of distributed power sources are coordinated and controlled, and a power distribution network is required to be continuously upgraded and reformed through a technology so as to ensure the coordinated interaction of multiple elements of source-network storage. The distributed power supply is accessed on a large scale to bring more uncertainty and randomness to the power distribution network, the system operation mode is more complex, the traditional deterministic planning is difficult to adapt to the construction of a novel power system, and the power distribution network planning needs to be converted into multi-scene probabilistic planning. The distributed power supply single units are small in scale, large in quantity and short in construction period, so that the power distribution network is required to be developed, improved and technically upgraded in advance, the situation of distributed photovoltaic development is closely tracked, and management modes in aspects of grid-connected service, transaction settlement, operation and maintenance regulation and control are optimized.
The distributed power supply is connected into the power distribution network in a large quantity, the operation and monitoring of the power distribution network are inevitably influenced, indexes such as power quality and reliability are also changed, and in order to ensure the safety and reliability of the power grid, the fault detection problem and the fault removal problem of an active power distribution network system are required to be monitored in real time through the existing monitoring technology. When the distributed power supply fails, as long as the distributed power supply is not released in time, the influence of the distributed power supply on the system power quality always exists, the fluctuation power output of the distributed power supply can influence the power grid voltage to different degrees, if the failure is not timely removed, the distributed power supply generates an island effect when the power distribution network possibly develops into voltage loss after being influenced, the capability of being connected with the power grid is lost, and the power supply quality and the life safety of maintenance personnel can be influenced by the island of the local power grid. Therefore, fault feeder lines are timely and reasonably cut off, and the fault feeder lines become an indispensable factor for ensuring safety in an active power distribution network.
At present, the line selection technology is relatively mature, successful application is achieved in the actual field, the line selection device can accurately select the fault feeder line, line selection protection can also accurately act after certain delay, and students at home and abroad are working to solve the adaptability problem of high resistance and transient faults. However, the distribution network is mostly radial, has multiple branches, complex structure and easy topology, and many places of the distribution network have no measurable condition, and the distribution network has weak signal and larger attenuation compared with the transmission network, so that the accurate distance of the fault is difficult to locate even if the fault feeder line is determined. Many fault localization methods are only theoretically feasible or feasible in laboratory environments and are difficult to adapt to the severe operating environment of a real power distribution network. After the distributed active power distribution network has a ground fault, the rapid positioning and isolation of the fault has very important significance for improving the power supply reliability, and meanwhile, the method is an important requirement for the construction of the intelligent power distribution network.
In practical application, the fault locating method for the power distribution network is numerous, but for a distributed active power distribution network system, the existing fault locating technical effect is not ideal, so that further research is necessary for the problem.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a fault positioning method and system for an active power distribution network based on a fault transient signal so as to realize accurate fault positioning of a distributed active power distribution network.
In order to solve the technical problems, the invention provides an active power distribution network fault positioning method based on a fault transient signal, which specifically comprises the following steps:
step1: the active power distribution network fails, the fault line selection device is started immediately, and a fault feeder line containing a distributed power supply is selected;
step2: calculating transient pure fault components of zero mode current of fault feeder lines at each reachable node;
step3: extracting 2ms before the fault of the zero-mode current transient state pure fault component of each reachable node, and 5ms data after the fault, enhancing the amplitude of the zero-mode current transient state pure fault component by using a Teager energy operator, and inhibiting interference clutter;
step4: calculating the energy duty ratio histogram of each processed reachable node zero-mode current transient pure fault component;
step5: and calculating the similarity of the energy duty ratio histograms of all adjacent reachable nodes, and carrying out fault location on the active power distribution network system according to the similarity.
Further, in Step1:
step1.1: active bus zero sequence voltage instantaneous value
Is greater than->
The fault line selection device is started immediately, wherein +.>
The value of (2) is set according to the local distribution network, and the +.>
Representing the rated voltage of the bus;
step1.2: the transient phase current mutation direction is detected through the distributed feeder automation devices installed at all reachable nodes, any two-phase mutation directions of sound branches are the same, and the fault phase of the fault branch is opposite to the mutation directions of other phases, so that a fault feeder is selected.
Further, in Step2:
step2.1: subtracting the first power frequency period before the fault from the first power frequency period after the fault of the wave recording data of the zero-mode current and subtracting the steady-state power frequency period after the fault from the first power frequency period after the fault, thereby obtaining transient pure fault components of the zero-mode current of the fault feeder line at each reachable node;
step2.2: the transient pure fault components are calculated as follows:
where j represents reachable nodes, n represents the number of reachable nodes,
is a zero-mode current transient pure fault component; />
Sampling value of the first power frequency period after zero-mode current failure; />
Sampling value of the first power frequency period before zero-mode current failure; />
The sampling value of the tenth power frequency period after zero-mode current fault is obtained, and the duration of the transient process of the power distribution network is 3-4 power frequency periods.
Further, in Step3:
step3.1: extracting 2ms before the fault of the zero-mode current transient state pure fault component of each reachable node, and 5ms data after the fault, enhancing the amplitude of the zero-mode current transient state pure fault component by using a Teager energy operator, and inhibiting interference clutter;
step3.2: comparing steady state zero mode current of upstream and downstream measuring points of fault point, generally comprising
I.e. the steady-state amplitude of the zero-mode current upstream of the fault point is greater than the steady-state amplitude of the zero-mode current downstream of the fault point.
Further, in Step4:
step4.1: calculating the energy duty ratio histogram of each processed reachable node zero-mode current transient pure fault component;
step4.2: histogram correlation coefficient calculation formula:
wherein:
the value range of the correlation coefficient is [0,1], when the correlation coefficient is 0, the two histograms are completely uncorrelated, and when the correlation coefficient is 1, the two histograms are completely correlated;
further, in Step5:
step5.1: calculating the similarity of the energy duty ratio histograms of all adjacent reachable nodes, and carrying out fault location on the active power distribution network system according to the similarity;
step5.2: if the energy factor histogram similarity of the adjacent measuring points is larger than the threshold value, outputting a last segment as a fault segment; otherwise, if the energy factor histogram similarity of the adjacent measuring points is larger than the threshold value, the section corresponding to the energy factor histogram similarity of the adjacent measuring points is not larger than the threshold value is a fault section.
Another aspect of the present invention provides an active power distribution network fault location system based on a fault transient signal, including:
and a data acquisition module: the method is used for collecting the zero sequence voltage of a bus and the zero sequence current of each feeder line in the active power distribution network;
and a numerical value calculation module: the method is used for calculating a fault line selection device starting signal; the method comprises the steps of calculating the amplitude of a zero-mode current transient pure fault component after the Teager energy operator is reinforced; calculating and obtaining zero sequence current of each feeder line and zero mode current transient pure fault components of each feeder line;
the logic judgment module is used for: the method is used for judging whether the zero sequence voltage instantaneous value of the bus is larger than the starting threshold value of the fault line selection device; and the method is used for judging whether the similarity value of the energy factor histogram meets the threshold value of the fault section.
Further, the data acquisition module specifically includes:
a data acquisition unit: the system is used for collecting bus zero sequence voltage signals and feeder zero sequence current signals from a measured unit in real time from a sensor and other measuring equipment;
an analog-to-digital conversion unit: for converting the acquired analog quantity signal into a digital quantity signal.
Further, the numerical calculation module specifically includes:
a signal calculation unit: the system is used for constructing a fault line selection device starting signal and a whole system processing signal for the collected bus zero sequence voltage;
an energy operator calculation unit: the method is used for calculating the amplitude of the zero-mode current transient pure fault component after the Teager energy operator is reinforced, and suppressing interference clutter;
transient pure fault component calculation unit: and calculating and obtaining zero sequence current of each feeder line and zero mode current transient pure fault components of each feeder line.
Further, the logic judging module specifically includes:
bus zero sequence voltage judging unit: judging bus zero sequence voltage instantaneous value
Whether or not is greater than->
If not, continuing to execute the judgment, and if so, starting the fault line selection device;
fault section positioning judgment unit: and the energy factor histogram similarity value is used for judging whether the energy factor histogram similarity value meets the threshold value of the fault section, and each section of the fault feeder line is sequentially judged, so that the fault section is judged.
The beneficial effects of the invention are as follows:
1. the invention effectively overcomes the influence of the problems of most of the active power distribution networks, such as radial shape, more branches, complex structure, easy topology change and the like, utilizes the transient state information after the occurrence of the faults to complete the positioning of fault sections, calculates the transient state pure fault components of zero-mode current of the fault feeder line, extracts the characteristic quantity thereof, realizes the correct line selection of the faults, can quickly isolate the faults and recover the power supply of the non-fault area.
2. According to the invention, the amplitude of the transient pure fault component of the zero-mode current is enhanced through the Teager energy operator, the interference clutter is restrained, and the problems that the signal of a small-current grounding system is weak, the attenuation in a power distribution network system is large and the like are solved.
3. The invention overcomes the defect that the active power distribution network is difficult to meet the requirements of mass communication and accurate time synchronization.
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In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without the inventive task for a person skilled in the art.
FIG. 1 is a flow chart of a fault location algorithm of the present invention;
fig. 2 is a simplified topological diagram of an active power distribution network model built in embodiment 1 of the present invention;
FIG. 3 is a structural parameter diagram of overhead line according to embodiment 1 of the present invention;
FIG. 4 is a fault upstream energy factor histogram of embodiment 1 of the present invention;
FIG. 5 is a histogram of energy factors downstream of a fault in accordance with embodiment 1 of the present invention;
FIG. 6 is a simplified topology diagram of an active distribution network cable hybrid model built in accordance with embodiment 2 of the present invention;
FIG. 7 is a structural parameter diagram of a three-core cable according to embodiment 2 of the present invention;
FIG. 8 is a fault upstream energy factor histogram of embodiment 2 of the present invention;
fig. 9 is a fault downstream energy factor histogram of embodiment 2 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by a person skilled in the art without any inventive effort, are intended to be within the scope of the present invention based on the embodiments of the present invention.
Example 1
The invention aims to provide a fault transient signal-based active power distribution network fault positioning method and system, which aim to solve the problems of inaccurate and unreliable fault route selection of the existing power distribution network.
The fault location is realized by the following fault location system:
the data acquisition module comprises: the data acquisition unit is used for acquiring bus zero sequence voltage signals and feeder zero sequence current signals from the measured unit in real time from the sensor and other measuring equipment; and the analog-to-digital conversion unit is used for converting the acquired analog quantity signal into a digital quantity signal.
The numerical calculation module includes: the signal calculation unit is used for constructing a fault line selection device starting signal and a whole system processing signal for the collected bus zero sequence voltage; the energy operator calculation unit is used for calculating the amplitude of the zero-mode current transient pure fault component after the Teager energy operator is reinforced and inhibiting interference clutter; and the transient pure fault component calculation unit is used for calculating and obtaining the zero sequence current of each feeder line and the transient pure fault component of the zero mode current of each feeder line.
The logic judgment module comprises: bus zero sequence voltage judging unit for judging bus zero sequence voltage instantaneous value
Whether or not is greater than->
If not, continuing to execute the judgment, and if so, starting the fault line selection device; the fault section positioning judging unit is used for judging whether the similarity value of the energy factor histogram meets the fault section threshold value or not, and sequentially judging each section of the fault feeder line so as to judge the fault section.
In the embodiment, a distribution line model is firstly built on a PSCAD, a simulation system is shown in fig. 2, the system has 6 feeder lines which are all overhead lines, and a line L 1 5 measuring points are distributed on the surface and respectively marked as measuring points A, B, C, D and E, and the distance between adjacent measuring points is 3Kilometers, set faults occur between the stations D, E, the fault type is single-phase earth faults, and the overhead line towers and stripline arrangements are shown in fig. 3.
The fault location is carried out according to the fault location method of the active power distribution network as shown in fig. 1, and the specific steps include:
step1: active power distribution network fault and active bus zero sequence voltage instantaneous value
Is greater than->
Wherein
The value is 0.15, and the feeder line L 1 The fault line selection device with zero sequence current is started immediately, and a fault feeder line containing a distributed power supply is selected as L 1 ；
Step2: and calculating transient pure fault components of zero-mode current of the fault feeder line at each reachable node through distributed feeder line automation devices installed at each reachable node, namely measuring points A, B, C, D and E, wherein the distance between adjacent measuring points is 3 km. Subtracting a steady-state power frequency period after the fault from a first power frequency period after the fault by using the wave recording data of the zero-mode current, thereby obtaining transient pure fault components of the zero-mode current of the fault feeder line at each reachable node, wherein the transient pure fault components have the following calculation formula:
where j represents reachable nodes, n represents the number of reachable nodes,
is a zero-mode current transient pure fault component; />
Sampling value of the first power frequency period after zero-mode current failure; />
Sampling value of the first power frequency period before zero-mode current failure; />
The sampling value of the tenth power frequency period after zero-mode current fault is obtained, and the duration of the transient process of the power distribution network is 3-4 power frequency periods.
Step3: 2ms before each reachable node zero-mode current transient state pure fault component is extracted, 5ms data after the fault is detected, the amplitude of the zero-mode current transient state pure fault component is enhanced by using a Teager energy operator, and interference clutter is restrained. From the operation result, the original waveform can extract a high-frequency new wave signal after high-pass filtering, and the signal amplitude and characteristics are obviously enhanced after Teager energy operator calculation is performed on the Gao Pinxin wave signal;
step4: calculating the energy duty ratio histogram of each zero-mode current transient pure fault component of each reachable node after processing, wherein the fault upstream histogram is shown in fig. 4, and the fault downstream measuring point histogram is shown in fig. 5;
step5: and calculating the similarity of the energy duty ratio histograms of all adjacent reachable nodes, and carrying out fault location on the active power distribution network system according to the similarity. If the energy factor histogram similarity of the adjacent measuring points is greater than 0.6, outputting a last segment as a fault segment; otherwise, if the energy factor histogram similarity of the adjacent measuring points is larger than 0.6, d mn The section less than or equal to 0.6 is a fault section. For the fault condition, establishing a fault section discriminant d= [ d ] AB d BC d CD d DE ]，d DE -0.3866, the resulting negative value indicates opposite polarity within the segment, according to the discriminant: d DE |=0.3866<0.6, so the section DE is a fault section, which accords with the theoretical result;
example 2
In this embodiment, the same system and method as in embodiment 1 are used for fault location. In the embodiment, a distribution line model is firstly built on a PSCAD, a simulation system is shown in fig. 6, a system feeder is a cable mixed feeder, and a neutral point is grounded through a Z-shaped grounding transformer and an arc suppression coil. The arc suppression coil adopts overcompensation. The cable model selects a three-phase single-core cable, the sectional view of the cable model is shown in fig. 7, 5 measuring points are distributed on a line L1 and respectively marked as measuring points A, B, C, D and E, the distance between adjacent measuring points is 3 km, and faults are arranged between the measuring points C, D.
The method comprises the following specific steps:
step1: active distribution network faults, and the system detects feeder L containing distributed power supply 1 The fault line selection device is started immediately when zero sequence current exists, and a fault feeder line containing a distributed power supply is selected as L 1 ；
Step2: and calculating transient pure fault components of zero-mode current of the fault feeder line at each reachable node through distributed feeder line automation devices installed at each reachable node, namely measuring points A, B, C, D and E, wherein the distance between adjacent measuring points is 3 km. Subtracting a steady-state power frequency period after the fault from a first power frequency period after the fault by using the wave recording data of the zero-mode current, thereby obtaining transient pure fault components of the zero-mode current of the fault feeder line at each reachable node, wherein the transient pure fault components have the following calculation formula:
where j represents reachable nodes, n represents the number of reachable nodes,
is a zero-mode current transient pure fault component; />
Sampling value of the first power frequency period after zero-mode current failure; />
Sampling value of the first power frequency period before zero-mode current failure; />
For the tenth power frequency period sampling value after zero-mode current fault, the duration of the transient process of the general power distribution network is 3-4 power frequency cycles.
Step3: 2ms before each reachable node zero-mode current transient state pure fault component is extracted, 5ms data after the fault is detected, the amplitude of the zero-mode current transient state pure fault component is enhanced by using a Teager energy operator, and interference clutter is restrained. From the operation result, the original waveform can extract a high-frequency new wave signal after high-pass filtering, and after the Teager energy operator calculation is performed on the Gao Pinxin wave signal, the signal amplitude and the characteristics are obviously enhanced, and the characteristic quantity of the fault transient signal is extracted.
Step4: the energy duty ratio histogram of each processed reachable node zero-mode current transient pure fault component is calculated, the fault upstream histogram is shown in fig. 8, and the fault downstream measuring point histogram is shown in fig. 9.
Step5: and calculating the similarity of the energy duty ratio histograms of all adjacent reachable nodes, calculating the similarity coefficient of the adjacent reachable nodes and the energy duty ratio histograms, and carrying out fault location on the active power distribution network system according to criteria. If the energy factor histogram similarity of the adjacent measuring points is greater than 0.6, outputting a last segment as a fault segment; otherwise, if the energy factor histogram similarity of the adjacent measuring points is larger than 0.6, d mn The section less than or equal to 0.6 is a fault section. For the fault condition, establishing a fault section discriminant d= [ d ] AB d BC d CD d DE ]According to the energy factor histogram correlation method, determining d CD =[1.0000 1.0000 -0.0745 0.9831]So section C, D is a failed section, conforming to the theoretical result.
The foregoing embodiments may be partially modified in numerous ways by those skilled in the art without departing from the principles and spirit of the invention, the scope of which is defined in the claims and not by the foregoing embodiments, and all such implementations are within the scope of the invention.
Claims (8)
1. A fault transient signal-based active power distribution network fault positioning method is characterized by comprising the following steps of:
step1: the active power distribution network fails, the fault line selection device is started immediately, and a fault feeder line containing a distributed power supply is selected;
step2: calculating transient pure fault components of zero mode current of fault feeder lines at each reachable node;
step3: extracting 2ms before the fault of the zero-mode current transient state pure fault component of each reachable node, and 5ms data after the fault, enhancing the amplitude of the zero-mode current transient state pure fault component by using a Teager energy operator, and inhibiting interference clutter;
step4: calculating the energy duty ratio histogram of each processed reachable node zero-mode current transient pure fault component;
step5: and calculating the similarity of the energy duty ratio histograms of all adjacent reachable nodes, and carrying out fault location on the active power distribution network system according to the similarity.
2. The fault location method for an active power distribution network based on a fault transient signal according to claim 1, wherein the fault location method comprises the following steps: in Step1, the zero sequence voltage instantaneous value of the active bus is used for
Is larger than the starting threshold value of the fault line selection device>
，
To set parameters +.>
The fault line selection device is started immediately for the rated voltage of the bus; the transient phase current mutation direction is detected, the directions of any two phase mutation amounts of sound branches are the same, and the directions of fault phases and other phase mutation amounts of fault branches are opposite, so that a fault feeder line is selected.
3. The fault location method for an active power distribution network based on a fault transient signal according to claim 1, wherein the fault location method comprises the following steps: the transient pure fault component in Step2 is calculated as follows:
where j represents reachable nodes, n represents the number of reachable nodes,
is a zero-mode current transient pure fault component; />
Sampling value of the first power frequency period after zero-mode current failure; />
Sampling value of the first power frequency period before zero-mode current failure;
and the sampling value is the tenth power frequency period sampling value after zero-mode current failure.
4. The fault location method for an active power distribution network based on a fault transient signal according to claim 1, wherein the fault location method comprises the following steps: in Step5, calculating the energy ratio histogram similarity of each adjacent reachable node, and if the energy factor histogram similarity of the adjacent measuring points is greater than a threshold value, outputting a final segment as a fault segment; otherwise, if the energy factor histogram similarity of the adjacent measuring points is larger than the threshold value, the section corresponding to the energy factor histogram similarity of the adjacent measuring points is not larger than the threshold value is a fault section.
5. An active power distribution network fault location system based on fault transient signals is characterized by comprising:
and a data acquisition module: the method is used for collecting the zero sequence voltage of a bus and the zero sequence current of each feeder line in the active power distribution network;
and a numerical value calculation module: the method is used for calculating a fault line selection device starting signal; the method comprises the steps of calculating the amplitude of a zero-mode current transient pure fault component after the Teager energy operator is reinforced; calculating and obtaining zero sequence current of each feeder line and zero mode current transient pure fault components of each feeder line;
the logic judgment module is used for: the method is used for judging whether the zero sequence voltage instantaneous value of the bus is larger than the starting threshold value of the fault line selection device; and the method is used for judging whether the similarity value of the energy factor histogram meets the threshold value of the fault section.
6. The fault location system of an active power distribution network based on a fault transient signal of claim 5, wherein the data acquisition module specifically comprises:
a data acquisition unit: the system is used for collecting bus zero sequence voltage signals and feeder zero sequence current signals from a measured unit in real time from a sensor and other measuring equipment;
an analog-to-digital conversion unit: for converting the acquired analog quantity signal into a digital quantity signal.
7. The fault location system of an active power distribution network based on a fault transient signal according to claim 5, wherein the numerical calculation module specifically comprises:
a signal calculation unit: the system is used for constructing a fault line selection device starting signal and a whole system processing signal for the collected bus zero sequence voltage;
an energy operator calculation unit: the method is used for calculating the amplitude of the zero-mode current transient pure fault component after the Teager energy operator is reinforced, and suppressing interference clutter;
transient pure fault component calculation unit: and calculating and obtaining zero sequence current of each feeder line and zero mode current transient pure fault components of each feeder line.
8. The fault location system of an active power distribution network based on a fault transient signal according to claim 5, wherein the logic determination module specifically comprises:
bus zero sequence voltage judging unit: judging bus zero sequence voltage instantaneous value
Whether or not is greater than->
If not, continuing to execute the judgment, and if so, starting the fault line selection device;
fault section positioning judgment unit: and the energy factor histogram similarity value is used for judging whether the energy factor histogram similarity value meets the threshold value of the fault section, and each section of the fault feeder line is sequentially judged, so that the fault section is judged.
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