CN114675124A - Four-end line fault double-end distance measurement method and system - Google Patents

Four-end line fault double-end distance measurement method and system Download PDF

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Publication number
CN114675124A
CN114675124A CN202210167516.XA CN202210167516A CN114675124A CN 114675124 A CN114675124 A CN 114675124A CN 202210167516 A CN202210167516 A CN 202210167516A CN 114675124 A CN114675124 A CN 114675124A
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China
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branch
fault
point
junction
line
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Inventor
余洪
吴通华
姚刚
戴魏
孙良凯
纪浩然
梁臣
杨平怡
洪丰
江源
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Nari Technology Co Ltd
NARI Nanjing Control System Co Ltd
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Nari Technology Co Ltd
NARI Nanjing Control System Co Ltd
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Priority to CN202210167516.XA priority Critical patent/CN114675124A/en
Publication of CN114675124A publication Critical patent/CN114675124A/en
Priority to PCT/CN2022/131273 priority patent/WO2023160020A1/en
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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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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Locating Faults (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The invention discloses a four-end line fault double-end distance measurement method and a system, wherein the method comprises the steps of identifying all junction points of four-end lines and calculating the line distance length between adjacent junction points; responding to a line protection tripping signal, and respectively calculating virtual voltage and virtual current of each junction; calculating virtual voltage converted to a corresponding intersection point based on analog quantity information and branch parameter information of each line protection installation position, and positioning an area where a fault point is located; and based on the line distance length of each region, a fault point is positioned by using a double-end distance measurement algorithm. The invention does not need to add extra line parameter setting, is easy to realize in the existing line protection, and can realize accurate distance measurement under various fault conditions.

Description

Four-end line fault double-end distance measurement method and system
Technical Field
The invention belongs to the field of relay protection of power systems, and particularly relates to a four-end line fault and two-end distance measurement method and system.
Background
At present, the fault location algorithm applied to the power transmission line mainly comprises: single-ended ranging algorithms and double-ended ranging algorithms. For a single-end fault location algorithm, generally, a metal fault can be accurately located only by a line at one end, the fault location result is inaccurate due to the existence of a shunt branch at the other two ends, and the multi-end line cannot accurately or even cannot be located when a high-resistance ground fault occurs. The traditional double-end distance measurement algorithm is only suitable for a double-end system. For a T-connection line (three-terminal system), a two-terminal ranging algorithm based on a T-point virtual voltage is only suitable for the three-terminal system with only one junction, and when the number of the junctions is more than one, the existing T-connection line two-terminal ranging method cannot be suitable; for four-end lines, because there is more than one junction (as shown in fig. 1), the existing T-connection line double-end ranging method cannot be applied, so that a four-end line fault ranging algorithm is provided, which mainly comprises a traveling wave method and a wave impedance method, and has the problems of large calculation amount or complex principle and the like, thereby causing difficult engineering.
Disclosure of Invention
Aiming at the problems, the invention provides a four-end line fault and two-end distance measurement method and a system, which automatically identify the junction points in different areas and calculate the line distance length between the junction points; dividing the four-terminal system circuit into at most five areas, and respectively calculating virtual voltage and virtual current of two intersection points; and the fault point is positioned in which area, and the fault point is positioned by using a double-end ranging algorithm, so that accurate ranging can be realized under various fault conditions.
In order to achieve the technical purpose and achieve the technical effects, the invention is realized by the following technical scheme:
in a first aspect, the present invention provides a double-end distance measurement method for a four-end line fault, including:
identifying all junction points of the four-end line, and calculating the line distance length between adjacent junction points;
responding to a line protection tripping signal, and respectively calculating virtual voltage and virtual current of each junction;
calculating virtual voltage converted to a corresponding intersection point based on analog quantity information and branch parameter information of each line protection installation position, and positioning an area where a fault point is located;
and based on the line distance length of each region, a fault point is positioned by using a double-end distance measurement algorithm.
Optionally, the method for identifying an intersection includes:
dividing the four-end line into 5 areas, the number of the junction points is 2, and the four areas are respectively marked as first junction points T1And a second intersection point T2；
Responding to a signal that no fault exists in the four-end line and the load current of any junction meets a preset requirement, and calculating virtual compensation voltage converted to the same junction by each branch;
screening out the branch with the minimum absolute value of the difference between the virtual compensation voltages corresponding to the branch where the host is located, and determining that the two branches share the first intersection point T1The other two branches share the second junction point T2。
Optionally, the calculation formula of the virtual compensation voltage is as follows:
Figure BDA0003516200250000021
wherein the content of the first and second substances,
Figure BDA0003516200250000022
the positive sequence virtual compensation voltage is converted for the branch n to the same junction point, where n is 1,2,3,4,
Figure BDA0003516200250000023
the positive sequence voltage at the installation is protected for branch n,
Figure BDA0003516200250000024
for protection of the positive-sequence current, Z, at the installation for branch n1_nIs the positive sequence impedance of the full length of the n lines of the branch.
Alternatively, when branch 1 and branch 2 share the first junction point T1Branch 3 and branch 4 share a second junction T2The method for calculating the line distance length between the two junction points comprises the following steps:
calculate the first junction point T1Current of
Figure BDA0003516200250000025
And a second junction point T2Current of
Figure BDA0003516200250000026
Calculating the ratio of the line positive sequence impedance between the two junctions to the positive sequence impedance of branch 1
Figure BDA0003516200250000027
And calculating the line distance length between the two junction points based on the ratio and the line distance length of the branch 1.
Optionally, the method for locating the area where the fault point is located includes:
responding to the line protection tripping signal, and calculating virtual compensation voltage converted by each branch circuit to a junction point corresponding to the branch circuit;
respectively calculate
Figure BDA0003516200250000028
Comparing the calculated result with a preset threshold value, and according to the ratioThe comparison results are used to determine the fault region, wherein,
Figure BDA0003516200250000029
respectively corresponding to the A phase, the B phase and the C phase of the circuit,
Figure BDA00035162002500000210
convert branch 1 to first junction point T1The virtual compensation voltage of each phase is calculated,
Figure BDA00035162002500000211
convert to the first junction point T for branch 21The virtual compensation voltage of each phase is calculated,
Figure BDA00035162002500000212
convert branch 3 to a second junction point T2The virtual compensation voltage of each phase is calculated,
Figure BDA00035162002500000213
convert to the second junction point T for the branch 42Virtual compensation voltages for each phase.
Optionally, the determining a fault region according to the determination result specifically includes:
when in use
Figure BDA00035162002500000214
And is
Figure BDA00035162002500000215
Then, the fault is positioned between two junction points;
when in use
Figure BDA00035162002500000216
And is provided with
Figure BDA00035162002500000217
If so, the fault point is in the branch 1 or the branch 2;
when in use
Figure BDA00035162002500000218
And is
Figure BDA00035162002500000219
The point of failure is either leg 3 or leg 4;
when in use
Figure BDA00035162002500000220
And is
Figure BDA00035162002500000221
The fault point is in branch 1 or branch 2;
when in use
Figure BDA00035162002500000222
And is
Figure BDA00035162002500000223
The point of failure is either leg 3 or leg 4.
Alternatively, if the localized fault is in leg 1 or leg 2;
First using the second junction point T2Calculating a first junction point T by the compensated virtual voltage of the point1Compensated virtual voltage of
Figure BDA0003516200250000031
Figure BDA0003516200250000032
Wherein
Figure BDA0003516200250000033
Is a second junction point T2The phase current of the point fault phase is,
Figure BDA0003516200250000034
and
Figure BDA0003516200250000035
the fault phase currents measured at the protective installation positions of the branch 3 and the branch 4 respectively;
Figure BDA0003516200250000036
is a second junction point T2Zero sequence current
Figure BDA0003516200250000037
Z1_1、Z0_1Respectively positive sequence impedance and zero sequence impedance of the whole line length of the branch circuit 1;
if it is
Figure BDA0003516200250000038
The failure point is in zone 1;
if it is
Figure BDA0003516200250000039
The failure point is in zone 2.
Alternatively, if the localized fault is in leg 3 or leg 4;
first using a first junction point T1The compensated virtual voltage of (2) calculates a second junction point T2Compensated virtual voltage of a point
Figure BDA00035162002500000310
Figure BDA00035162002500000311
Wherein
Figure BDA00035162002500000312
Is a first junction point T1The phase current of the fault is determined,
Figure BDA00035162002500000313
and
Figure BDA00035162002500000314
fault phase currents measured at the protective installation positions of the branch 1 and the branch 2 respectively;
Figure BDA00035162002500000315
is a first junction point T1Zero sequence current
Figure BDA00035162002500000316
Z1_1、Z0_1Positive and zero sequence impedances, respectively, of the full line length of branch 1；
If it is
Figure BDA00035162002500000317
The point of failure is in leg 3;
if it is
Figure BDA00035162002500000318
The point of failure is at leg 4.
Alternatively, when branch 1 and branch 2 share the first junction point T1Branch 3 and branch 4 share a second junction T2(ii) a First junction point T1And a second junction point T2The area between is the line 5;
when the branch n has a fault and is an asymmetric fault, calculating a fault location per unit value by adopting the following formula:
Figure BDA00035162002500000319
Wherein:
Figure BDA00035162002500000320
is the negative sequence current at the head end of the branch n,
Figure BDA00035162002500000321
is the negative-sequence current at the n-terminal end of the branch,
Figure BDA00035162002500000322
is the negative sequence voltage at the head end of the branch n,
Figure BDA00035162002500000323
is a negative sequence voltage, Z, at the n-terminal end of the branch2_nIs the branch n negative sequence impedance.
When the branch n has a fault and is a symmetric fault, calculating a fault location per unit value by adopting the following formula:
Figure BDA00035162002500000324
wherein:
Figure BDA00035162002500000325
is the positive sequence current at the head end of the branch n,
Figure BDA00035162002500000326
is the positive sequence current at the n-terminal end of the branch,
Figure BDA00035162002500000327
is the positive sequence voltage at the head end of the branch n,
Figure BDA0003516200250000041
is a positive sequence voltage, Z, at the n-terminal end of the branch1_nIs a branch n positive sequence impedance;
based on Lf＝k*lnCalculating the fault location point,/nThe total length of the n lines of the branch.
In a second aspect, the present invention provides a four-terminal line fault two-terminal ranging system, including a storage medium and a processor;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of the first aspects.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a four-end line fault double-end distance measurement method and a system, which automatically identify junction points in different areas and calculate the line distance length between the junction points; dividing the four-end system circuit into at most five areas, and respectively calculating virtual voltage and virtual current of two junction points; the method has the advantages that the fault point is positioned in which area, and the fault point is positioned by using a double-end distance measurement algorithm, so that accurate distance measurement under various fault conditions can be realized, additional line parameter setting is not required, and the method is easy to realize in the conventional line protection.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a four terminal line segment;
FIG. 2 is a flow chart of junction identification according to an embodiment of the present invention;
fig. 3 is a flowchart illustrating a fault selection process according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.
The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.
Example 1
The embodiment of the invention provides a four-end line fault double-end distance measurement method, which comprises the following steps:
identifying all junction points of the four-end line, and calculating the line distance length between adjacent junction points;
responding to a line protection tripping signal, and respectively calculating virtual voltage and virtual current of each junction;
calculating virtual voltage converted to a corresponding intersection point based on analog quantity information and branch parameter information of each line protection installation position, and positioning an area where a fault point is located;
And based on the line distance length of each region, a fault point is positioned by using a double-end distance measurement algorithm.
In a specific implementation manner of the embodiment of the present invention, as shown in fig. 2, the method for identifying an intersection includes:
as shown in fig. 1, the four-port line is divided into 5 regions, and the number of the junctions is 2, which are respectively marked as the first junctions T1And a second intersection point T2(ii) a The corresponding region of branch 1 is M-T1Referred to as zone 1; the corresponding region of the branch 2 is P-T1Referred to as zone 2; the corresponding region of the branch 3 is N-T2Referred to as zone 3; zone corresponding to branch 4Is Q-T2Referred to as zone 4; t is1And T2The area in between is called zone 5;
in response to a signal that none of the four terminals (M, P, Q, N) is faulty and that any of the junction loads meet a predetermined requirement, e.g., a load current at either end is greater than 0.1In，InRated current), calculating each branch to convert to the same junction point T (first junction point T)1Or a second junction point T2) The virtual compensation voltage of (a);
screening out the branch with the minimum absolute value of the difference between the virtual compensation voltages corresponding to the branch where the host is located, and determining that the two branches share the first intersection point T1The other two branches share the second junction point T2。
In a specific implementation process of the embodiment of the present invention, a calculation formula of the virtual compensation voltage is as follows:
Figure BDA0003516200250000051
Wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003516200250000052
the positive sequence virtual compensation voltage is converted for the branch n to the same junction point, where n is 1,2,3,4,
Figure BDA0003516200250000053
the positive sequence voltage at the installation is protected for branch n,
Figure BDA0003516200250000054
protection of positive-sequence current, Z, at installation for branch n1_nIs the positive sequence impedance of the full length of the n lines of the branch.
The line protection installed on the default branch 1 is a host, the line protection installed on the default branch 2, the default branch 3 and the default branch 4 is a slave, and the intersection point closest to the default branch 1 is defaulted to be a first intersection point T1Respectively calculate
Figure BDA0003516200250000055
Figure BDA0003516200250000056
Identifying a common first junction point T by screening the minimum principle of the median values of the three1The line (e.g.:
Figure BDA0003516200250000057
the smallest of the three, branch 2 and branch 1 share the first junction point T1) In addition, the two end systems share the same T2And (4) point.
In a specific implementation manner of the embodiment of the present invention, when the branch 1 and the branch 2 share the first junction point T1Branch 3 and branch 4 share a second junction T2The method for calculating the line distance length between the two junction points comprises the following steps:
calculate the first junction point T1Current of
Figure BDA0003516200250000058
And a second junction point T2Current of
Figure BDA0003516200250000059
Calculating the ratio of the line positive sequence impedance between the two junctions to the positive sequence impedance of branch 1
Figure BDA00035162002500000510
And calculating the line distance length between the two junction points based on the ratio and the line distance length of the branch 1.
In a specific implementation manner of the embodiment of the present invention, as shown in fig. 3, the method for locating the area where the fault point is located includes:
responding to a line protection tripping signal, namely entering a fault selection logic after line protection tripping, and calculating virtual compensation voltage of each line converted to a junction point corresponding to each line;
respectively calculate
Figure BDA0003516200250000061
Comparing the calculation result with a preset threshold value, and determining a fault region according to the comparison result, wherein,
Figure BDA0003516200250000062
respectively corresponding to the A phase, the B phase and the C phase of the circuit,
Figure BDA0003516200250000063
convert branch 1 to first junction point T1The virtual compensation voltage of each phase is calculated,
Figure BDA0003516200250000064
convert the branch 2 to the first junction point T1The virtual compensation voltage of each phase is calculated,
Figure BDA0003516200250000065
convert branch 3 to a second junction point T2The virtual compensation voltage of each phase is calculated,
Figure BDA0003516200250000066
convert the branch 4 to a second junction point T2Virtual compensation voltages for each phase.
Wherein, the determining the fault area according to the judgment result specifically includes:
when in use
Figure BDA0003516200250000067
And is
Figure BDA0003516200250000068
When the fault is located between two junctions (i.e., region 5);
when in use
Figure BDA0003516200250000069
And is
Figure BDA00035162002500000610
When the fault point is in the branch 1 (namely, the area 1) or the branch 2 (namely, the area 2);
when in use
Figure BDA00035162002500000611
And is
Figure BDA00035162002500000612
The point of failure is either branch 3 (i.e., zone 3) or branch 4 (i.e., zone 4);
when in use
Figure BDA00035162002500000613
And is
Figure BDA00035162002500000614
The fault point is in branch 1 or branch 2;
When in use
Figure BDA00035162002500000615
And is
Figure BDA00035162002500000616
The point of failure is either leg 3 or leg 4.
If the positioning fault is in branch 1 or branch 2;
first using the second junction point T2Calculating a first junction point T by the compensated virtual voltage of the point1Compensated virtual voltage of
Figure BDA00035162002500000617
Figure BDA00035162002500000618
Wherein
Figure BDA00035162002500000619
As a second junction point T2The phase current of the point fault phase is,
Figure BDA00035162002500000620
and
Figure BDA00035162002500000621
the fault phase currents measured at the protective installation positions of the branch 3 and the branch 4 respectively;
Figure BDA00035162002500000622
is a second junction point T2Zero sequence current
Figure BDA00035162002500000623
Z1_1、Z0_1Respectively positive sequence impedance and zero sequence impedance of the whole line length of the branch circuit 1;
if it is
Figure BDA00035162002500000624
The failure point is in zone 1;
if it is
Figure BDA00035162002500000625
The failure point is in zone 2.
If the localization fault is in leg 3 or leg 4;
first using a first junction point T1The compensated virtual voltage of (2) calculates a second junction point T2Compensated virtual voltage of a point
Figure BDA0003516200250000071
Figure BDA0003516200250000072
Wherein
Figure BDA0003516200250000073
Is a first junction point T1The phase current of the fault phase is,
Figure BDA0003516200250000074
and
Figure BDA0003516200250000075
fault phase currents measured at the protection installation positions of the branch 1 and the branch 2 are respectively measured;
Figure BDA0003516200250000076
is a first junction point T1Zero sequence current
Figure BDA0003516200250000077
Z1_1、Z0_1Respectively positive sequence impedance and zero sequence impedance of the whole line length of the branch circuit 1;
if it is
Figure BDA0003516200250000078
The point of failure is in leg 3;
if it is
Figure BDA0003516200250000079
The point of failure is at leg 4.
In a specific implementation manner of the embodiment of the present invention, the locating a fault point by using a double-end ranging algorithm specifically includes the following steps:
taking the branch n as an example of the fault and when the fault is an asymmetric fault, calculating a fault location per unit value by using the following formula:
Figure BDA00035162002500000710
Wherein:
Figure BDA00035162002500000711
is the negative sequence current at the head end of the branch n,
Figure BDA00035162002500000712
is the negative-sequence current at the n-terminal end of the branch,
Figure BDA00035162002500000713
is the negative sequence voltage at the head end of the branch n,
Figure BDA00035162002500000714
is a negative sequence voltage, Z, at the n-terminal end of the branch2_nIs the branch n negative sequence impedance.
Taking the branch n as an example, and when the fault occurs symmetrically, the per unit value of the fault location is calculated by the following formula:
Figure BDA00035162002500000715
wherein:
Figure BDA00035162002500000716
is the positive sequence current at the head end of the branch n,
Figure BDA00035162002500000717
is the positive sequence current at the n-terminal end of the branch,
Figure BDA00035162002500000718
is the positive sequence voltage at the head end of the branch n,
Figure BDA00035162002500000719
is a positive sequence voltage, Z, at the n-terminal end of the branch1_nIs the branch n positive sequence impedance.
Based on Lf＝k*lnAnd calculating a fault positioning point to complete double-end fault distance measurement.
Example 2
Based on the same inventive concept as embodiment 1, the embodiment of the invention provides a four-terminal line fault double-terminal ranging system, which comprises a storage medium and a processor;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any of embodiment 1.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. A four-terminal line fault double-terminal distance measurement method is characterized by comprising the following steps:
identifying all junction points of the four-end line, and calculating the line distance length between adjacent junction points;
responding to a line protection tripping signal, and respectively calculating virtual voltage and virtual current of each junction;
calculating virtual voltage converted to a corresponding intersection point based on analog quantity information and branch parameter information of each line protection installation position, and positioning an area where a fault point is located;
and based on the line distance length of each region, a fault point is positioned by using a double-end distance measurement algorithm.
2. The quadripole line fault double-ended distance measurement method according to claim 1, wherein the method of identifying the junction comprises:
dividing four-end lines into 5 regions, with the number of junction points being 2, respectively recording as first junction points T1And a second junction point T2；
Responding to a signal that no fault exists in the four-end line and the load current of any junction meets a preset requirement, and calculating virtual compensation voltage converted from each branch to the same junction;
screening out the branch with the minimum absolute value of the difference between the virtual compensation voltages corresponding to the branch where the host is located, and determining that the two branches share the first intersection point T 1The other two branches share the second junction point T2。
3. The double-ended ranging method for four-terminal line faults according to claim 2, wherein: the calculation formula of the virtual compensation voltage is as follows:
Figure FDA0003516200240000011
wherein the content of the first and second substances,
Figure FDA0003516200240000012
positive sequence for converting a branch n to the same junctionThe virtual offset voltage, n, 1,2,3,4,
Figure FDA0003516200240000013
the positive sequence voltage at the installation is protected for branch n,
Figure FDA0003516200240000014
for protection of the positive-sequence current, Z, at the installation for branch n1_nIs the positive sequence impedance of the full length of the n lines of the branch.
4. The four-terminal line fault two-terminal ranging method of claim 2, wherein: when branch 1 and branch 2 share the first junction point T1Branch 3 and branch 4 share a second junction T2The method for calculating the line distance length between the two junction points comprises the following steps:
calculate the first junction point T1Current of
Figure FDA0003516200240000015
And a second junction point T2Current of (2)
Figure FDA0003516200240000016
Calculating the ratio of the line positive sequence impedance between the two junctions to the positive sequence impedance of branch 1
Figure FDA0003516200240000017
And calculating the line distance length between the two junction points based on the ratio and the line distance length of the branch 1.
5. The four-terminal line fault two-terminal ranging method of claim 4, wherein: the method for positioning the area where the fault point is located comprises the following steps:
Responding to the line protection tripping signal, and calculating virtual compensation voltage converted by each branch circuit to a junction point corresponding to the branch circuit;
are respectively provided withCalculation-
Figure FDA0003516200240000018
Comparing the calculation result with a preset threshold value, and determining a fault region according to the comparison result, wherein,
Figure FDA0003516200240000021
b. c corresponding to phase A, phase B and phase C of the circuit respectively,
Figure FDA0003516200240000022
convert branch 1 to first junction point T1The virtual compensation voltage of each phase is calculated,
Figure FDA0003516200240000023
convert the branch 2 to the first junction point T1The virtual compensation voltage of each phase is calculated,
Figure FDA0003516200240000024
convert branch 3 to a second junction point T2The virtual compensation voltage of each phase is calculated,
Figure FDA0003516200240000025
convert the branch 4 to a second junction point T2Virtual compensation voltages for each phase.
6. The four-terminal line fault two-terminal ranging method of claim 5, wherein: the determining the fault area according to the judgment result specifically includes:
when in use
Figure FDA0003516200240000026
And is
Figure FDA0003516200240000027
Then, the fault is positioned between two junction points;
when in use
Figure FDA0003516200240000028
And is
Figure FDA0003516200240000029
If so, the fault point is in the branch 1 or the branch 2;
when in use
Figure FDA00035162002400000210
And is
Figure FDA00035162002400000211
The fault point is in branch 3 or branch 4;
when in use
Figure FDA00035162002400000212
And is
Figure FDA00035162002400000213
The fault point is in branch 1 or branch 2;
when in use
Figure FDA00035162002400000214
And is
Figure FDA00035162002400000215
The point of failure is either leg 3 or leg 4.
7. The four-terminal line fault two-terminal ranging method of claim 6, wherein: if the positioning fault is in branch 1 or branch 2;
First using the second junction point T2Calculating a first junction point T by the compensation virtual voltage of the point1Compensated virtual voltage of
Figure FDA00035162002400000216
Figure FDA00035162002400000217
Wherein
Figure FDA00035162002400000218
As a second junction point T2The phase current of the point fault phase is,
Figure FDA00035162002400000219
and
Figure FDA00035162002400000220
fault phase currents measured at the protection installation sites for branch 3 and branch 4, respectively;
Figure FDA00035162002400000221
is a second junction point T2Zero sequence current
Figure FDA00035162002400000222
Z1_1、Z0_1Respectively positive sequence impedance and zero sequence impedance of the whole line length of the branch circuit 1;
if it is
Figure FDA00035162002400000223
The failure point is in zone 1;
if it is
Figure FDA00035162002400000224
The failure point is in zone 2.
8. The four-terminal line fault two-terminal ranging method of claim 6, wherein: if the localization fault is in leg 3 or leg 4;
first using a first junction point T1The compensated virtual voltage of (2) calculates a second junction point T2Compensated virtual voltage of a point
Figure FDA00035162002400000225
Figure FDA00035162002400000226
Wherein
Figure FDA00035162002400000227
Is a first junction point T1The phase current of the fault is determined,
Figure FDA00035162002400000228
and
Figure FDA00035162002400000229
fault phase currents measured at the protective installation positions of the branch 1 and the branch 2 respectively;
Figure FDA00035162002400000230
is a first junction point T1Zero sequence current
Figure FDA0003516200240000031
Z1_1、Z0_1Respectively positive sequence impedance and zero sequence impedance of the whole line length of the branch circuit 1;
if it is
Figure FDA0003516200240000032
The point of failure is in leg 3;
if it is
Figure FDA0003516200240000033
The point of failure is at leg 4.
9. The four-terminal line fault two-terminal ranging method of claim 6, wherein: when branch 1 and branch 2 share the first junction point T1Branch 3 and branch 4 share a second junction T 2(ii) a First junction point T1And a second junction point T2The area between is the line 5;
when the branch n has a fault and is an asymmetric fault, calculating a fault location per unit value by adopting the following formula:
Figure FDA0003516200240000034
wherein:
Figure FDA0003516200240000035
is the negative sequence current at the head end of the branch n,
Figure FDA0003516200240000036
is the negative-sequence current at the n-terminal end of the branch,
Figure FDA0003516200240000037
is the negative sequence voltage at the head end of the branch n,
Figure FDA0003516200240000038
is a negative sequence voltage, Z, at the n-terminal end of the branch2_nIs the branch n negative sequence impedance.
When the branch n has a fault and is a symmetric fault, calculating a fault location per unit value by adopting the following formula:
Figure FDA0003516200240000039
wherein:
Figure FDA00035162002400000310
is the positive sequence current at the head end of the branch n,
Figure FDA00035162002400000311
is the positive sequence current at the n-terminal end of the branch,
Figure FDA00035162002400000312
is the positive sequence voltage at the head end of the branch n,
Figure FDA00035162002400000313
is a positive sequence voltage, Z, at the n-terminal end of the branch1_nIs a branch n positive sequence impedance;
based on Lf＝k*lnCalculating the fault location point,/nThe total length of the n lines of the branch.
10. A four-terminal line fault two-terminal ranging system is characterized by comprising a storage medium and a processor;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 9.
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