CN108594077B - Voltage sag fault source positioning method based on monitoring point observation intersection region - Google Patents

Voltage sag fault source positioning method based on monitoring point observation intersection region Download PDF

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CN108594077B
CN108594077B CN201810402879.0A CN201810402879A CN108594077B CN 108594077 B CN108594077 B CN 108594077B CN 201810402879 A CN201810402879 A CN 201810402879A CN 108594077 B CN108594077 B CN 108594077B
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fault
voltage sag
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monitoring
observation
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CN108594077A (en
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侯燕文
高运兴
田立军
张天豪
刘冲
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State Grid Corp of China SGCC
TaiAn Power Supply Co of State Grid Shandong Electric Power Co Ltd
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State Grid Corp of China SGCC
TaiAn Power Supply Co of State Grid Shandong Electric Power Co Ltd
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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
    • 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
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • 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

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Abstract

The invention discloses a voltage sag fault source positioning method based on monitoring point observation cross area, which comprises the following steps: respectively simulating and calculating voltage sag when faults occur in the power grid area, and determining a critical voltage sag value in a sag interval; determining monitoring points in a power grid area; connecting fault points of the same critical voltage sag value of the same monitoring point with each other to form a closed curve, forming a step observation area of the monitoring point, and obtaining step observation areas of all the monitoring points in the power grid area; step observation areas of similar faults of all monitoring points are crossed to form an observation cross area diagram of the power grid area; when voltage sag of the power grid area occurs, firstly, the fault type is determined, and according to the voltage sag of the monitoring point, the area where the fault is located is determined in the corresponding monitoring point observation cross area graph, so that fault positioning is completed. The method can realize fault location in a smaller range and has high identification accuracy.

Description

Voltage sag fault source positioning method based on monitoring point observation intersection region
Technical Field
The invention relates to the technical field of power grid fault positioning, in particular to a voltage sag fault source positioning method based on monitoring point observation of a cross region.
Background
The traditional method for locating the power grid fault is to judge whether the short-circuit fault is located at the upstream or the downstream of the monitoring device, such as a disturbance power method, a disturbance energy method, a real part current method and the like. Upstream refers to the power supply side of the monitoring device, and downstream refers to the non-power supply side of the monitoring device. The fault location is mainly used for overhauling and troubleshooting faults and is mainly applied to radial, trunk and chain connection modes of a low-voltage power distribution network. In the urban ring network power supply system with medium and high voltage levels, the power flow direction is uncertain, and the positioning method is not applicable any more without upstream and downstream saying.
Currently, fault location generally means that the position of a fault point is accurately identified, and the requirement is more severe than that of a traditional method, and some methods are as follows: a monte carlo position estimation method, a least square method fitting estimation function, an imaginary-real part separation method, a voltage sag data matching method, and the like are gradually proposed. The methods have large calculation amount, the monitoring equipment is required to have certain floating point operation capability or rapid data uploading capability, the upper computer is used for analyzing and calculating, and meanwhile, most of the methods need current measurement data.
The voltage sag monitoring system is a system independent from the power quality monitoring system, and aims to realize the following functions: the circuit current measurement function is removed, no voltage harmonic wave measurement exists, and the storage and operation capacity of the main control chip is reduced, so that the equipment cost is reduced; the voltage recording during the voltage sag period is focused, so that the voltage sag event and the influence can be further analyzed conveniently; and estimating the voltage sag occurrence area range, so as to facilitate statistics in the future.
Therefore, the Monte Carlo position estimation method, the least square method fitting estimation function, the virtual-real part separation method, the voltage sag data matching method and the like are separated from the hardware basis of voltage sag monitoring, and the practical application is difficult.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a voltage sag fault source positioning method based on monitoring point observation intersection areas. The operation is relatively simple.
A voltage sag fault source positioning method based on monitoring point observation cross areas comprises the following steps:
respectively simulating and calculating voltage sag when three-phase short circuit, single-phase grounding, two-phase short circuit and two-phase short circuit grounding faults occur in a power grid region, determining the step length of the voltage sag depth, dividing the voltage sag depth by the length, and then determining the critical voltage sag value of a sag interval;
determining monitoring points in a power grid area, and finding out critical fault points which can be observed when critical voltage sag values of sag intervals of the monitoring points occur according to each monitoring point;
connecting fault points of the same critical voltage sag value of the same monitoring point with each other to form a closed curve, forming a step observation area of the monitoring point, and obtaining step observation areas of all the monitoring points in the power grid area;
step observation areas of similar faults of all monitoring points are crossed to form four observation cross area graphs of the power grid area corresponding to three-phase short circuit, single-phase grounding, two-phase short circuit and two-phase short circuit grounding faults;
when the voltage sag of the power grid area occurs, firstly determining the fault type, determining the area where the fault is located in the observation cross area diagram of the corresponding monitoring point according to the voltage sag of the monitoring point, completing fault positioning,
according to a further preferable technical scheme, when the critical voltage sag value of the sag interval is determined, the set percentage of the rated voltage is taken as a step length, the voltage sag depth is divided into a plurality of corresponding intervals, and the end value of each interval is the critical voltage sag value of each sag interval.
In a further preferred technical scheme, end values of intervals in the intervals are taken as positions of fault points, voltage sag conditions at the monitoring points when the fault points of all lines have short-circuit faults are calculated, and when the fault point a has a short-circuit fault, so that the voltage sag of the monitoring point m is smaller than a critical voltage sag value, and the next fault point b adjacent to the fault point a has a short-circuit fault, so that the voltage sag of the monitoring point m is larger than the critical voltage sag value, the fault point a is a critical fault point.
In a further preferred technical scheme, the voltage sag of the monitoring point caused by the short circuit of the fault point is calculated according to a three-sequence impedance matrix of the power grid.
Further preferred technical solution, regarding a three-sequence impedance matrix:
if the fault point is a bus node, the three-sequence impedance matrix is unchanged, if the fault point is on the line, the fault point f is used as a newly added node of the power grid, the corresponding node impedance matrix is added by one step, and the fault position parameter lambda is used for expressing as follows:
Figure BDA0001646144720000021
in the formula IjfRepresents the distance, l, from the line starting point j to the fault point fjkIndicating the length of the line j-k, j and k representing the bus number at both ends of the line, i.e. the head and tail ends of the line, respectively. The fault parameter λ is used to characterize the fault occurrence position, so that the node impedance of the fault point f can be obtained as a function of the fault parameter λ, as shown in the following formula:
Figure BDA0001646144720000022
Figure BDA0001646144720000023
in the formula, ZmfIs the mutual impedance between monitoring point m and fault point f, ZmjIs the mutual impedance between the monitoring point m and the starting point j of the line, ZmkIs the mutual impedance between the monitoring point m and the line end point k, ZjjIs the self-impedance of the starting point j of the line, ZjkIs the mutual impedance between the starting point j of the line and the end point k of the line, ZkkFor the self-impedance of the line terminal k, n is 1,2, and 0 indicates the positive, negative, and zero sequence components when an asymmetric fault occurs. And finishing the node impedance matrix after the fault according to the mutual impedance and the self impedance of the fault point.
In a further preferred technical scheme, the calculation of the voltage sag value of the monitoring point caused by the short-circuit fault at the fault point is divided into two conditions: the fault line comprises a symmetrical fault and an asymmetrical fault, wherein the symmetrical fault refers to a three-phase short circuit fault, and the asymmetrical fault refers to a single-phase ground fault, a two-phase short circuit fault and a two-phase short circuit ground fault.
Further preferred solution, regarding symmetric faults:
according to the superposition principle, the voltage of each position after the fault occurs can be obtained by superposing the normal component and the fault component;
off-diagonal element Z in the nodal impedance matrixjiRepresents the mutual impedance, and the value represents the voltage U at the j node when the i node injects unit current and the rest nodes do not inject currentjUnit current I at node IiThe ratio of (a) to (b),therefore, the fault component Δ U of the monitoring point mmfThe following formula:
ΔUmf＝IfZmf
in the formula IfIndicating fault current, ZmfRepresenting the mutual impedance between the monitoring point m and the fault point f;
diagonal element Z of the nodal impedance matrixiiThe self-impedance is represented, and the value of the self-impedance indicates the voltage U at the i node when the i node injects unit current and the other nodes do not inject currentiAnd the current I at the I nodeiRatio of (A) to (B), IfCan be represented by the following formula:
Figure BDA0001646144720000031
in the formula (I), the compound is shown in the specification,
Figure BDA0001646144720000032
is the voltage per unit value z before voltage sag occurs at node ffIs the fault resistance at node f. Metallic short-circuit fault zfWhen 0, then there is formula:
Figure BDA0001646144720000033
if all the values in the formula are per unit values, the voltage per unit value of the monitoring point m before the fault occurs is approximated
Figure BDA0001646144720000034
Then there are:
Figure BDA0001646144720000035
Umand when the three-phase short-circuit fault occurs at the fault point f, the voltage sag amplitude at any monitoring point m is shown.
A further preferred solution, regarding asymmetric faults:
under the condition that the power grid has asymmetric faults, a system equivalent network is divided into a positive sequence network, a negative sequence network and a zero sequence network by adopting a symmetric component method, and each sequence network is calculated by adopting a superposition principle. The following analyses all used phase A as the reference phase;
the three-phase voltage at the monitoring point m during the single-phase earth fault is as follows:
Figure BDA0001646144720000041
wherein α ═ ej120°；
The three-phase voltage at the monitoring point m during the BC phase-to-phase short circuit fault is as follows:
Figure BDA0001646144720000042
when the BC is connected with the ground and has a fault, the three-phase voltage at the monitoring point m is as follows:
Figure BDA0001646144720000043
and the lowest three-phase root mean square value at the monitoring point m is the voltage sag amplitude.
In a further preferred technical scheme, the step observation areas of similar faults of all monitoring points are crossed specifically as follows:
the monitoring points have different ladder observation areas according to different fault types, namely a three-phase short circuit ladder observation area, a single-phase grounding ladder observation area, a two-phase short circuit ladder observation area and a two-phase short circuit grounding ladder observation area;
the stepped observation areas of the same type of faults of different monitoring points are intersected, so that the power grid is divided into a plurality of small areas, two intersection points exist if the areas are intersected, and only one intersection point exists if the areas are tangent.
According to a further preferable technical scheme, when the fault type is determined, for a single-phase earth fault, the amplitude of one phase voltage is lower than the mean value, and the amplitudes of the other two phases are higher than the mean value; for two-phase short-circuit ground faults and two-end short-circuit faults, the amplitude values of two phases of voltages are lower than the average value, the amplitude value of the other phase of voltages is higher than the average value, and the two-phase short-circuit ground fault is determined by the larger voltage zero-sequence component; and for the three-phase fault, the three-phase voltage amplitude values are all subjected to temporary drop with similar amplitude.
Further, according to a preferred technical scheme, the determining of the area where the fault is located specifically includes: when voltage sag is caused by short-circuit fault, different monitoring points detect different voltage sag depths, the fault point of the voltage sag is judged to be positioned in the step monitoring area according to the sag depths, and then the area where the fault is positioned is finally determined by the observation intersection areas of the different monitoring points.
In a further preferred technical scheme, the voltage sag fault source positioning method based on monitoring point observation in the cross area is used for determining the position of a fault source causing voltage sag in positioning in a ring-type multi-power supply network.
Compared with the prior art, the invention has the beneficial effects that:
the invention can complete the positioning of the fault source only by utilizing the voltage data of the voltage sag monitoring system, can conveniently complete the positioning of the fault area on the hardware platform of the voltage sag monitoring system, and has lower cost of the voltage sag monitoring terminal equipment compared with other DTUs, RTUs or electric energy quality measurement terminals, thereby saving the cost.
The invention only calculates the step observation area of each monitoring point at the initial stage of the voltage sag monitoring system, and if the power grid is not expanded, the structure is not greatly changed, and the step observation area of the monitoring point is not changed. In practical application, the fault positioning calculation amount is small, the upper computer or the monitoring terminal can instantly complete the fault positioning calculation, and the method has the characteristics of easiness in realization and high positioning speed.
The invention can position the fault source in a smaller range, has higher accuracy, is convenient for counting the time, the position and the depth of the voltage sag, and is beneficial to the management of the voltage sag fault source and the adoption of corresponding protective measures for sensitive loads.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a schematic flow diagram of a voltage sag fault source positioning method for observing a cross region based on monitoring points;
FIG. 2 shows a monitoring point m1Schematic diagram of a step observation region.
FIG. 3 shows a monitoring point m2Schematic diagram of a step observation region.
Fig. 4 is a schematic view of fault location using observation intersection regions of monitoring points.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Term interpretation section:
and (4) fault point: and (4) the virtual power grid short-circuit fault position in the simulation calculation.
Observable region (Monitor Reach Area, MRA): the method refers to a fault point area which can be observed by a monitoring point when a system has a short-circuit fault and causes a voltage sag at the monitoring point m. In other words, a short-circuit fault at any one of the MRA of monitoring point m will cause a voltage sag at node m.
Monitor Step Reach Area (MSRA): and further distinguishing the observable area, and dividing the observable area according to the voltage dip depth range of the monitoring point m caused by the fault to form an area division graph similar to the contour line of a hill in geography. If the step length is 10% of the voltage sag causing the monitoring point m, the observation area is further divided into 9 areas of 90% -80%, 80% -70%, 70% -60%, 60% -50%, 50% -40%, 40% -30%, 30% -20%, 20% -10% and less than 10%.
Monitoring the cross area by monitoring points: the step observation areas of 2 or more than 2 monitoring points are mutually intersected and cut into small-range areas.
As introduced in the background art, in order to solve the above technical problems, the present application provides a voltage sag fault source positioning method based on monitoring point observation of a cross region.
The main principle of the invention is as follows: in the monitoring range of the voltage sag monitoring point, short-circuit faults at different distances can cause voltage sags of the monitoring point in different degrees, and similarly to a group of concentric circles taking the monitoring point as the center of a circle, according to the size of the voltage sag degree of the monitoring point caused by the short-circuit fault, the observation areas of the monitoring point are layered and are called step observation areas. When a fault occurs, voltage dips of different degrees can be monitored by adjacent different monitoring points, two groups of concentric circle-shaped stepped observation areas are crossed with each other, only one of the crossed points is the fault point if the two areas are tangent, the two crossed points are obtained if the two areas are crossed, the fault points can be obtained by checking the two crossed points one by one, and the workload is greatly reduced. Therefore, the invention can carry out simple and accurate fault location.
The method can realize the positioning estimation of the sag source of the voltage sag caused by the short-circuit fault in the urban power grid, divide the observation area of the voltage sag monitoring point into the step observation area, and utilize the step observation area of different monitoring points to perform cross positioning. The method can complete the positioning of the fault source only by utilizing the voltage data of the voltage sag monitoring system, accords with the hardware basis of the current voltage sag monitoring system, and has the characteristics of easy realization and high algorithm calculation speed. The fault source can be positioned in a small range, so that the statistics of time, position and depth of voltage sag is facilitated, and the management of the voltage sag fault source and the adoption of corresponding measures for sensitive loads are facilitated.
As shown in fig. 1, a method for positioning a voltage sag fault source based on monitoring point observation of a cross region is characterized by comprising the following steps:
(1) respectively simulating and calculating voltage sag conditions when three-phase short circuit, single-phase grounding, two-phase short circuit and two-phase short circuit grounding faults occur in a power grid region, and finding out critical fault points which can be observed when critical voltage sag values of a sag interval occur at a monitoring point m;
(2) connecting critical fault points under the same condition into a closed curve to form a monitoring point step observation area;
(3) obtaining the step observation areas of other monitoring points in the power grid area according to the same method;
(4) step observation areas of similar faults of all monitoring points are crossed to form four observation cross area graphs of the power grid corresponding to the four faults;
(5) when voltage sag occurs, determining the fault type, observing the area of the fault in the cross area graph at the corresponding monitoring point according to the voltage sag of the monitoring point, and completing fault positioning;
specifically, in step (1), the critical voltage sag value of each sag interval is specifically:
if the voltage sag depth is divided into 9 intervals of 90% -80%, 80% -70%, 70% -60%, 60% -50%, 50% -40%, 40% -30%, 30% -20%, 20% -10%, 10% or less by taking 10% of the rated voltage as a step length, the critical voltage sag value of each sag interval is respectively as follows: 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%.
In step (1), the critical failure points are specifically:
and (3) equally dividing each line into 9 sections, taking the end point of each section as the position of a fault point, adding 2 bus end points, and totally 10 fault points of each line. And calculating the voltage sag condition of the monitoring point when the fault points of all the lines have short-circuit faults, wherein if the voltage sag of the monitoring point m is smaller than the critical voltage sag value due to the short-circuit fault of a certain fault point a and the voltage sag of the monitoring point m is larger than the critical voltage sag value due to the short-circuit fault of the next adjacent fault point b, the fault point a is the critical fault point.
The voltage sag of the monitoring point caused by the short circuit of the fault point can be calculated according to the three-sequence impedance matrix of the power grid. And if the fault point is a bus node, the three-sequence impedance matrix is unchanged. If the fault point is on the line, the fault point f can be used as a newly added node of the power grid, the corresponding node impedance matrix is added by one step, and the fault position parameter lambda is used for expressing as follows:
Figure BDA0001646144720000071
in the formula IjfRepresents the distance, l, from the line starting point j to the fault point fjkIndicating the length of the line j-k, j and k representing the bus number at both ends of the line, i.e. the head and tail ends of the line, respectively. The fault parameter λ is used to characterize the fault occurrence position, so that the node impedance of the fault point f can be obtained as a function of the fault parameter λ, as shown in the following formula:
Figure BDA0001646144720000072
Figure BDA0001646144720000073
in the formula, ZmfIs the mutual impedance between monitoring point m and fault point f, ZmjIs the mutual impedance between the monitoring point m and the starting point j of the line, ZmkIs the mutual impedance between the monitoring point m and the line end point k, ZjjIs the self-impedance of the starting point j of the line, ZjkIs the mutual impedance between the starting point j of the line and the end point k of the line, ZkkFor the self-impedance of the line terminal k, n is 1,2, and 0 indicates the positive, negative, and zero sequence components when an asymmetric fault occurs. And finishing the node impedance matrix after the fault according to the mutual impedance and the self impedance of the fault point.
The calculation of the voltage sag value of the monitoring point caused by the short-circuit fault at the fault point can be divided into two conditions: symmetric faults and asymmetric faults. The symmetrical fault refers to a three-phase short circuit fault, and the asymmetrical fault refers to a single-phase ground fault, a two-phase short circuit fault and a two-phase short circuit ground fault.
1) Symmetrical fault
According to the superposition principle, the voltage of each position after the fault occurs can be obtained by superposing the normal component and the fault component.
Off-diagonal element Z in the nodal impedance matrixjiRepresents the mutual impedance, and the value represents the voltage U at the j node when the i node injects unit current and the rest nodes do not inject currentjUnit current I at node IiThe ratio of (a) to (b). Therefore, the fault component Δ U of the monitoring point mmfThe following formula:
ΔUmf＝IfZmf
in the formula IfIndicating fault current, ZmfRepresenting the mutual impedance between the monitoring point m and the fault point f.
Diagonal element Z of the nodal impedance matrixiiThe self-impedance is represented, and the value of the self-impedance indicates the voltage U at the i node when the i node injects unit current and the other nodes do not inject currentiAnd the current I at the I nodeiThe ratio of (a) to (b). I isfCan be represented by the following formula:
Figure BDA0001646144720000081
in the formula (I), the compound is shown in the specification,
Figure BDA0001646144720000082
is the voltage per unit value z before voltage sag occurs at node ffIs the fault resistance at node f. Metallic short-circuit fault zfWhen 0, then there is formula:
Figure BDA0001646144720000083
if all the values in the formula are per unit values, the voltage per unit value of the monitoring point m before the fault occurs is approximated
Figure BDA0001646144720000084
Then there are:
Figure BDA0001646144720000085
Umand when the three-phase short-circuit fault occurs at the fault point f, the voltage sag amplitude at any monitoring point m is shown.
2) Asymmetric fault
Under the condition that the power grid has asymmetric faults, the system equivalent network can be divided into a positive sequence network, a negative sequence network and a zero sequence network by adopting a symmetric component method, and each sequence network is calculated by adopting a superposition principle. The following analysis is based on phase A.
The three-phase voltage at the monitoring point m during the single-phase earth fault is as follows:
Figure BDA0001646144720000091
wherein α ═ ej120°。
The three-phase voltage at the monitoring point m during the BC phase-to-phase short circuit fault is as follows:
Figure BDA0001646144720000092
when the BC is connected with the ground and has a fault, the three-phase voltage at the monitoring point m is as follows:
Figure BDA0001646144720000093
and the lowest root mean square value in the three phases at the monitoring point m is the voltage sag amplitude.
In step (2), the critical failure points under the same conditions are specifically:
the critical fault points in the same condition are fault points which can enable the same monitoring point to generate the same critical voltage sag value, for example, all the fault positions which can enable the monitoring point m to generate 60% voltage sag are all the critical fault points in the condition.
In the step (2), the step observation area of the monitoring point is specifically as follows:
after connecting the critical fault points of the same condition by using curves, a multilayer closed curve surrounding the monitoring point m is formed, and the step length of the 10% sag range is used as a step length, so that 9 layers are total. Similar to the contour map of a hill in geography, a monitoring point step observation area is defined.
In step (3), the remaining other monitoring points are specifically:
more than one voltage sag monitoring point in the range of the power grid is needed. All monitoring points should be made to have their stepped observation zones.
In step (4), the step observation areas of similar faults of all monitoring points are crossed specifically as follows:
the monitoring points have different ladder observation areas according to different fault types, namely a three-phase short circuit ladder observation area, a single-phase grounding ladder observation area, a two-phase short circuit ladder observation area and a two-phase short circuit grounding ladder observation area.
The stepped observation areas of the same type of faults of different monitoring points are crossed, so that the power grid is divided into a plurality of small areas. FIG. 2 and FIG. 3 are monitoring points m1And m2The three-phase short-circuit fault step observation area. If they intersect, there are two points of intersection, and if they are tangent, there is only one point of intersection. By way of illustration, we tentatively explain one of the two intersections in the case of phase intersection. A portion of the intersection of the stepped observation regions of the two monitoring points is shown in fig. 4. The other three types of fault are similar to the other three types of fault, wherein the range of the stepped observation region of the two-phase short circuit fault is the smallest.
In the step (5), the determining of the fault type specifically includes:
for single-phase earth faults, the amplitude of one phase voltage is lower than the mean value, and the amplitudes of the other two phases are higher than the mean value; for two-phase short-circuit ground faults and two-end short-circuit faults, the amplitude values of two phases of voltages are lower than the average value, the amplitude value of the other phase of voltages is higher than the average value, and the two-phase short-circuit ground fault is determined by the larger voltage zero-sequence component; and for the three-phase fault, the three-phase voltage amplitude values are all subjected to temporary drop with similar amplitude.
In the step (5), the determining of the area where the fault is located specifically includes:
when voltage sag is caused by short-circuit fault, different monitoring points detect different voltage sag depths, the fault point of the voltage sag is judged to be positioned in the step monitoring area according to the sag depths, and then the area where the fault is positioned is finally determined by the observation intersection areas of the different monitoring points.
As shown in FIG. 4, a three-phase short-circuit fault occurs at the position of the fault flag, resulting in a monitoring point m1A 48% voltage sag occurs, monitoring point m2If a voltage sag of 23% occurs, the fault should be m1In the 50% -40% step observation area, m2And in 20% -30% of the step observation areas, the two intersection points are crossed to obtain two intersection points, the shadow area in the graph is one of the intersection points, the other intersection point is symmetrical with the shadow area about the crossed chord, and the two intersection points are subjected to fault troubleshooting respectively to complete the positioning of the area where the fault is located.
Compared with the traditional upstream and downstream positioning method, the method can position the fault source causing the voltage sag in the loop type multi-power supply network;
the method can only use the monitoring equipment of the voltage sag to carry out fault location, and does not need to call voltage and current data of a DTU, an RTU or other measurement systems. The operation is relatively simple.
The voltage sag monitoring terminal only extracts voltage sag data in a fault period, the data redundancy is low, the transmission processing is convenient, and the cost for realizing fault positioning is low.
The method can realize fault location in a smaller range, has high identification accuracy, is convenient for counting time, position and depth of voltage sag, and is beneficial to the management of a fault source.
Although the specific embodiments of the present invention have been described above with reference to the accompanying drawings, but not limiting the scope of the present invention, various modifications or variations that can be made by those skilled in the art without inventive effort are still within the scope of the present invention, for example, the dividing step of the step observation area in the process of the present invention is 10%, the number of fault points is 10 per line, the number of monitoring points is 2, and simple modifications including these optional values are still within the scope of the present invention. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. A voltage sag fault source positioning method based on monitoring point observation cross region is characterized by comprising the following steps:
respectively simulating and calculating voltage sag when three-phase short circuit, single-phase grounding, two-phase short circuit and two-phase short circuit grounding faults occur in a power grid region, determining the step length of the voltage sag depth, dividing the voltage sag depth by the step length, and then determining the critical voltage sag value of a sag interval;
determining monitoring points in a power grid area, and finding out critical fault points which can be observed when critical voltage sag values of sag intervals of the monitoring points occur according to each monitoring point;
connecting fault points of the same critical voltage sag value of the same monitoring point with each other to form a closed curve, forming a step observation area of the monitoring point, and obtaining step observation areas of all the monitoring points in the power grid area;
step observation areas of similar faults of all monitoring points are crossed to form four observation cross area graphs of the power grid area corresponding to three-phase short circuit, single-phase grounding, two-phase short circuit and two-phase short circuit grounding faults;
when voltage sag of the power grid area occurs, firstly, the fault type is determined, and according to the voltage sag of the monitoring point, the area where the fault is located is determined in the corresponding monitoring point observation cross area graph, so that fault positioning is completed.
2. The method as claimed in claim 1, wherein when determining the critical voltage sag value of the sag interval, dividing the voltage sag depth into a plurality of corresponding intervals by using the set percentage of the rated voltage as the step length, wherein the end value of each interval is the critical voltage sag value of each sag interval.
3. The method as claimed in claim 2, wherein the end values of the sections in the sections are taken as the positions of the fault points, the voltage sag condition at the monitoring points when the fault points of all the lines have short-circuit faults is calculated, and when the voltage sag of the monitoring point m is smaller than the critical voltage sag value due to the short-circuit fault at the fault point a and the voltage sag of the monitoring point m is larger than the critical voltage sag value due to the short-circuit fault at the next adjacent fault point b, the fault point a is the critical fault point.
4. The method for positioning the voltage sag fault source based on the monitoring point observation intersection region as claimed in claim 2, wherein the voltage sag of the monitoring point caused by the short circuit of the fault point is calculated according to a three-sequence impedance matrix of a power grid.
5. The method for locating the voltage sag fault source based on the monitoring point observation intersection area as claimed in claim 4, wherein, regarding the three-sequence impedance matrix:
if the fault point is a bus node, the three-sequence impedance matrix is unchanged, if the fault point is on the line, the fault point f is used as a newly added node of the power grid, the corresponding node impedance matrix is added by one step, and the fault position parameter lambda is used for expressing as follows:
Figure FDA0002380172660000011
in the formula IjfRepresents the distance, l, from the line starting point j to the fault point fjkThe lengths of the lines j-k are represented, j and k respectively represent bus numbers at two ends of the lines, namely the head end and the tail end of the lines, and the fault occurrence position is represented by a fault parameter lambda, so that a function of the node impedance of a fault point f and the fault parameter lambda can be obtained, and the function is shown as the following formula:
Figure FDA0002380172660000021
Figure FDA0002380172660000022
in the formula, ZmfIs the mutual impedance between monitoring point m and fault point f, ZmjIs the mutual impedance between the monitoring point m and the starting point j of the line, ZmkIs the mutual impedance between the monitoring point m and the line end point k, ZjjIs the self-impedance of the starting point j of the line, ZjkIs the mutual impedance between the starting point j of the line and the end point k of the line, ZkkAnd (3) the self-impedance of the line terminal point k is n equal to 1,2, and 0 represents positive sequence, negative sequence and zero sequence components when the asymmetric fault occurs, and the node impedance matrix after the fault can be completed according to the mutual impedance and the self-impedance of the fault point.
6. The method for positioning voltage sag fault sources based on monitoring point observation intersection areas as claimed in claim 1, wherein the calculation of the voltage sag values of the monitoring points caused by the short-circuit fault of the fault points is divided into two cases: the fault line comprises a symmetrical fault and an asymmetrical fault, wherein the symmetrical fault refers to a three-phase short circuit fault, and the asymmetrical fault refers to a single-phase ground fault, a two-phase short circuit fault and a two-phase short circuit ground fault.
7. The method for positioning the voltage sag fault source based on the monitoring point observation intersection region as claimed in claim 1, wherein the step observation region intersection of the same type of faults of all the monitoring points is specifically as follows:
the monitoring points have different ladder observation areas according to different fault types, namely a three-phase short circuit ladder observation area, a single-phase grounding ladder observation area, a two-phase short circuit ladder observation area and a two-phase short circuit grounding ladder observation area;
the stepped observation areas of the same type of faults of different monitoring points are intersected, so that the power grid is divided into a plurality of small areas, two intersection points exist if the areas are intersected, and only one intersection point exists if the areas are tangent.
8. The method for positioning the voltage sag fault source based on the monitoring point observation intersection region as claimed in claim 1, wherein when the fault type is determined, for a single-phase ground fault, the amplitude of one phase voltage is lower than the mean value, and the amplitudes of the other two phases are higher than the mean value; for two-phase short-circuit ground faults and two-end short-circuit faults, the amplitude values of two phases of voltages are lower than the average value, the amplitude value of the other phase of voltages is higher than the average value, and the two-phase short-circuit ground fault is determined by the larger voltage zero-sequence component; and for the three-phase fault, the three-phase voltage amplitude values are all subjected to temporary drop with similar amplitude.
9. The method for positioning the voltage sag fault source based on the monitoring point observation intersection region as claimed in claim 1, wherein the step of determining the region where the fault is located specifically comprises the steps of: when voltage sag is caused by short-circuit fault, different monitoring points detect different voltage sag depths, the fault point of the voltage sag is judged to be positioned in the step monitoring area according to the sag depths, and then the area where the fault is positioned is finally determined by the observation intersection areas of the different monitoring points.
10. The method for locating the voltage sag fault source based on the monitoring point observation cross area as claimed in any one of claims 1 to 9, wherein the method for locating the voltage sag fault source based on the monitoring point observation cross area is used for determining the location of locating the fault source causing the voltage sag in a ring-type multi-power supply network.
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