CN113533900B - System and method for judging fault section of power distribution network cable hybrid line - Google Patents

System and method for judging fault section of power distribution network cable hybrid line Download PDF

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CN113533900B
CN113533900B CN202110747823.0A CN202110747823A CN113533900B CN 113533900 B CN113533900 B CN 113533900B CN 202110747823 A CN202110747823 A CN 202110747823A CN 113533900 B CN113533900 B CN 113533900B
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cable
traveling wave
section
line
fault
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CN113533900A (en
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崔建业
盛海华
钱建国
李振华
杜浩良
徐峰
郑燃
李跃辉
吴佳毅
潘武略
朱英伟
黄健
蒋红亮
林军
刘乃杰
吴雪峰
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Jinhua Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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Jinhua Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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    • 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
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Abstract

The invention provides a system and a method for judging a fault section of a cable hybrid line of a power distribution network. The method specifically comprises the steps of firstly collecting voltage signals and current signals at two ends of a cable hybrid line of the power distribution network, then obtaining corresponding power frequency voltage and power frequency current according to collected voltage signal data and current signal data, then obtaining forward current traveling wave differential quantity and reverse current traveling wave differential quantity according to the power frequency voltage and the power frequency current, then determining a fault section judgment function according to the forward current traveling wave differential quantity and the reverse current traveling wave differential quantity, then calculating a fault section judgment value, and finally comparing the fault section judgment value with a preset threshold value to obtain a specific fault section. The method is suitable for judging the fault section of the multi-section cable hybrid line, can avoid errors caused by direct measurement of the traveling wave, and improves the accuracy of judging the fault section.

Description

System and method for judging fault section of power distribution network cable hybrid line
Technical Field
The invention relates to the technical field of protection and control of a power system, in particular to a system and a method for judging a fault section of a power distribution network cable hybrid line.
Background
With the increase of urban load density, the improvement of power supply reliability requirements and the requirement of urban appearance beautification in China, the cable plays an important role in a power distribution network system by virtue of the advantages of high power transmission reliability and no occupation of urban space, and an overhead line-cable mixed line also becomes a main line of a power distribution network grid structure. Due to the inconsistency of the overhead line-cable impedance characteristics, the conventional fault location method is no longer applicable. The fault location principle of the existing overhead line-cable hybrid line mainly adopts a method of firstly judging a fault section and then locating faults in the section. However, as for the section determination method, currently, a traveling wave method is commonly used to perform fault section determination on a three-section cable hybrid line, specifically, a fault occurrence section is distinguished by measuring the time when a fault initial traveling wave reaches two ends of the line, but the section determination result of the method is easily affected by an initial traveling wave head, if the initial traveling wave head is not identified accurately, the section determination result is greatly deviated from the actual result, and the accuracy of fault section determination cannot be ensured. The traveling wave method also comprises the step of judging the fault area by taking the time difference of the arrival of the initial traveling wave at two ends when the connection point is in fault as an area judgment threshold, but the judgment mode is influenced by the asynchronization of clocks of the two monitoring points, so that the calculation result of the area judgment threshold is influenced, and the accuracy of the judgment result of the fault area is reduced. And the existing method for judging the fault section by adopting the traveling wave method is mostly only suitable for two-section cable mixed lines, is not suitable for the multi-section cable mixed lines and has great limitation on the application range.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a system and a method for judging a fault section of a cable hybrid line of a power distribution network.
The purpose of the invention is realized by the following technical scheme:
a fault section judgment method for a power distribution network cable hybrid line comprises the following steps:
the method comprises the following steps that firstly, a data acquisition module acquires voltage signals and current signals at two ends of a cable hybrid line of a power distribution network, and the data acquisition module transmits acquired voltage signal data and current signal data to a data analysis module;
acquiring power frequency voltage and power frequency current according to the acquired voltage signal data and current signal data by a data analysis module, and acquiring forward current traveling wave differential quantity and reverse current traveling wave differential quantity according to the power frequency voltage and the power frequency current;
and thirdly, determining a fault section judgment function by the data analysis module according to the forward current traveling wave differential quantity and the reverse current traveling wave differential quantity, calculating a fault section judgment value by the data analysis module through the fault section judgment function, comparing the fault section judgment value with a preset threshold value by the data analysis module, and acquiring a specific fault section through the comparison result by the data analysis module.
The subsequent traveling wave calculation is carried out by collecting voltage signals and current signals at two ends of a cable hybrid line of the power distribution network instead of directly measuring the initial fault traveling wave, so that the error caused by the measurement of the traveling wave is reduced, and the accuracy of the subsequent fault section judgment is improved. And the fault section can be judged through the voltage signal and the current signal at the two ends of the line, the influence of the line structure is avoided, and the method is suitable for two-section and multi-section cable mixed lines.
Furthermore, the first section of the power distribution network cable hybrid line is an overhead line, the middle section of the power distribution network cable hybrid line is a cable line, and the last section of the power distribution network cable hybrid line is an overhead line.
Further, the calculation formula of the forward current traveling wave differential quantity obtained according to the power frequency voltage and the power frequency current in the step two is as follows:
Figure BDA0003144954780000031
wherein: d 1 Forward current traveling wave differential momentum;
Figure BDA0003144954780000032
is a forward current traveling wave flowing out of a connection point C of a first section overhead line and a middle section cable line;
Figure BDA0003144954780000033
is a forward current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line; e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cabling.
Further, the calculation formula of the difference of the traveling wave of the reverse current obtained according to the power frequency voltage and the power frequency current in the step two is as follows:
Figure BDA0003144954780000034
wherein: d 2 Traveling wave differential momentum is reverse current;
Figure BDA0003144954780000035
is a reverse current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line;
Figure BDA0003144954780000036
is a reverse current traveling wave flowing out of a connection point C of the first section of overhead line and the middle section of cable line; e is the natural constantCounting; gamma ray cable Is the transmission constant of the cable run; l is a radical of an alcohol CT Is the length of the cabling.
Further, in the second step, the power frequency voltage and the power frequency current are obtained by performing Fourier change on the collected voltage signal data and current signal data.
Further, the formula for calculating the fault section determination value in step three is as follows:
Figure BDA0003144954780000037
wherein: p is a fault section determination value, D 1 Traveling wave differential momentum for forward current, D 2 Traveling wave differential momentum for reverse current.
Further, in the third step, the preset threshold includes a first preset threshold and a second preset threshold, and an expression of the first preset threshold is as follows:
Figure BDA0003144954780000041
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cable run;
the expression of the second preset threshold is as follows:
Figure BDA0003144954780000042
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cabling.
Further, the determination criteria of the fault section are specifically: when the judgment value of the fault section is smaller than a first preset threshold value, the fault occurs in a head-end overhead line area; when the fault section judgment value is equal to a first preset threshold value, a fault occurs at the connecting point of the first section of overhead line and the cable line; when the fault section judgment value is larger than a first preset threshold value and smaller than a second preset threshold value, a fault occurs in a cable line area; when the fault section judgment value is equal to a second preset threshold value, the fault occurs at the connecting point of the cable line and the tail end overhead line; and when the fault section judgment value is greater than a second preset threshold value, the fault occurs in the tail end overhead line area.
The fault section is judged by presetting the threshold value, and the fault section can be judged only by comparing with the preset threshold value, so that the calculation is simple, the calculation amount is reduced, and the accuracy of the fault section judgment result can be ensured.
The utility model provides a trouble district section decision-making system based on distribution network cable hybrid line, includes data acquisition module and data analysis module, data acquisition module and data analysis module are connected, data acquisition module is used for gathering the voltage signal data and the current signal data of the both ends of cable hybrid line, data analysis module is used for carrying out the trouble district section and judges.
The invention has the beneficial effects that:
the traveling wave measurement is not directly carried out, the current signals and the voltage signals at the two ends of the line are measured, and then the current traveling waves in the head and tail end directions of all the sections of the line are obtained through a transmission line equation and a current traveling wave calculation formula. And by measuring the current signals and the voltage signals at the two ends of the line and applying the current signals and the voltage signals to the calculation of the traveling wave, the error caused by directly measuring the traveling wave can be avoided, and the accuracy of the judgment result of the fault section is improved.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a schematic diagram of an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a cable hybrid MN according to an embodiment of the present invention;
wherein: 1. data acquisition module, 2, data analysis module.
Detailed Description
The invention is further described below with reference to the figures and examples.
Example (b):
a fault section judgment method for a power distribution network cable hybrid line comprises the following steps:
the method comprises the following steps that firstly, a data acquisition module 1 acquires voltage signals and current signals at two ends of a cable hybrid line of a power distribution network, and the data acquisition module 1 transmits acquired voltage signal data and current signal data to a data analysis module 2;
step two, the data analysis module 2 acquires power frequency voltage and power frequency current according to the acquired voltage signal data and current signal data, and then acquires forward current traveling wave differential quantity and reverse current traveling wave differential quantity according to the power frequency voltage and the power frequency current;
step three, the data analysis module 2 determines a fault section judgment function according to the forward current traveling wave differential momentum and the reverse current traveling wave differential momentum, the data analysis module 2 calculates a fault section judgment value through the fault section judgment function, the data analysis module 2 compares the fault section judgment value with a preset threshold value, and the data analysis module 2 obtains a specific fault section through the comparison result.
The head section of the power distribution network cable hybrid line is an overhead line, the middle section of the power distribution network cable hybrid line is a cable line, and the tail section of the power distribution network cable hybrid line is an overhead line.
In the second step, the calculation formula of the forward current traveling wave differential quantity obtained according to the power frequency voltage and the power frequency current is as follows:
Figure BDA0003144954780000061
wherein: d 1 Forward current traveling wave differential momentum;
Figure BDA0003144954780000062
is a forward current traveling wave flowing out of a connection point C of a first section overhead line and a middle section cable line;
Figure BDA0003144954780000063
is a forward current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line; e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cabling.
In the second step, the calculation formula of the reverse current traveling wave differential quantity obtained according to the power frequency voltage and the power frequency current is as follows:
Figure BDA0003144954780000064
wherein: d 2 Traveling wave differential momentum for reverse current;
Figure BDA0003144954780000065
is a reverse current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line;
Figure BDA0003144954780000066
is a reverse current traveling wave flowing out of a connection point C of the first section of overhead line and the middle section of cable line; e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cabling.
And in the second step, the power frequency voltage and the power frequency current are obtained by carrying out Fourier change on the collected voltage signal data and current signal data.
The formula for calculating the fault section judgment value in the third step is as follows:
Figure BDA0003144954780000071
wherein: p is a fault section determination value, D 1 Is a forward current traveling wave differential momentum, D 2 Traveling wave differential momentum for reverse current.
In the third step, the preset threshold includes a first preset threshold and a second preset threshold, and the expression of the first preset threshold is as follows:
Figure BDA0003144954780000072
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is a radical of an alcohol CT Is the length of the cable run;
the expression of the second preset threshold is as follows:
Figure BDA0003144954780000073
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cabling.
The judgment basis of the fault section is specifically as follows: when the judgment value of the fault section is smaller than a first preset threshold value, the fault occurs in a head-end overhead line area; when the fault section judgment value is equal to a first preset threshold value, a fault occurs at the connecting point of the first section of overhead line and the cable line; when the fault section judgment value is larger than a first preset threshold value and smaller than a second preset threshold value, a fault occurs in a cable line area; when the fault section judgment value is equal to a second preset threshold value, the fault occurs at the connecting point of the cable line and the tail end overhead line; and when the fault section judgment value is larger than a second preset threshold value, the fault occurs in the tail end overhead line area.
A fault section judgment system based on a power distribution network cable hybrid line is shown in fig. 2 and comprises a data acquisition module 1 and a data analysis module 2, wherein the data acquisition module 1 is connected with the data analysis module 2, the data acquisition module 1 is used for acquiring voltage signal data and current signal data at two ends of the cable hybrid line, and the data analysis module 2 is used for judging a fault section.
As shown in fig. 3, a three-segment cable hybrid line MN composed of an overhead line MC, an overhead line TN, and a cable CT is taken as an example.
Because any point voltage and current on each single line can be decomposed into superposition of forward traveling waves and reverse traveling waves, the overhead line MC, the overhead line TN and the cable CT are respectively calculated, forward current traveling waves and reverse current traveling waves of the head end and the tail end of each section of line can be written according to a transmission equation of a power transmission line, and the forward current traveling waves and the reverse current traveling waves of the head end and the tail end of each section of line are obtained according to the following formula:
Figure BDA0003144954780000081
wherein:
Figure BDA0003144954780000082
is a forward current traveling wave flowing into the C end of the MC section of the overhead line,
Figure BDA0003144954780000083
in order to flow into the C-terminal reverse current traveling wave of the MC section of the overhead line,
Figure BDA0003144954780000084
is a forward current traveling wave flowing out of the C end of the MC section of the overhead line,
Figure BDA0003144954780000085
in order to flow out of the C-end reverse current traveling wave of the MC section of the overhead line,
Figure BDA0003144954780000086
is a forward current traveling wave at the end M of the MC section of the overhead line,
Figure BDA0003144954780000087
the reverse current traveling wave is the reverse current traveling wave of the M end of the MC section of the overhead line;
Figure BDA0003144954780000091
is the power frequency current flowing into the C end of the MC end of the overhead line,
Figure BDA0003144954780000092
is the power frequency current flowing out of the C end of the MC end of the overhead line;
Figure BDA0003144954780000093
for a T-terminal forward current traveling wave flowing into the overhead line TN section,
Figure BDA0003144954780000094
in order to flow into the T-side reverse current traveling wave of the overhead line TN section,
Figure BDA0003144954780000095
in order to flow out of the forward current traveling wave at the T-end of the TN section of the overhead line,
Figure BDA0003144954780000096
in order to flow out of the T-end reverse current traveling wave of the overhead line TN section,
Figure BDA0003144954780000097
is a forward current traveling wave at the N-terminal of the overhead line TN section,
Figure BDA0003144954780000098
the reverse current traveling wave is the reverse current traveling wave of the N end of the TN section of the overhead line;
Figure BDA0003144954780000099
for the power frequency current flowing into the T terminal of the overhead line TN terminal,
Figure BDA00031449547800000910
the power frequency current flows out of a T end of a TN end of the overhead line;
L MC line length, L, for the MC section of the overhead line CT Is the line length, L, of the CT section of the cable line TN The line length of a TN section of the overhead line; gamma ray line Is the transmission constant, gamma, of an overhead line cable Is the transmission constant of the cabling.
The current traveling waves in the head and tail end directions of each section of line can be obtained by the above formula, and the specific calculation formula is as follows:
Figure BDA00031449547800000911
wherein:
Figure BDA0003144954780000101
is a forward current traveling wave flowing into the C end of the MC section of the overhead line,
Figure BDA0003144954780000102
in order to flow into the C-end reverse current traveling wave of the MC section of the overhead line,
Figure BDA0003144954780000103
is a forward current traveling wave flowing out of the C end of the MC section of the overhead line,
Figure BDA0003144954780000104
in order to flow out of the C-end reverse current traveling wave of the MC section of the overhead line,
Figure BDA0003144954780000105
is a forward current traveling wave at the end M of the MC section of the overhead line,
Figure BDA0003144954780000106
the reverse current traveling wave is the reverse current traveling wave of the M end of the MC section of the overhead line;
Figure BDA0003144954780000107
is the power frequency current flowing into the C end of the MC end of the overhead line,
Figure BDA0003144954780000108
is the power frequency current flowing out of the C end of the MC end of the overhead line,
Figure BDA0003144954780000109
is the power frequency voltage of the C end of the MC section of the overhead line,
Figure BDA00031449547800001010
the power frequency voltage of the T end of the TN section of the overhead line;
Figure BDA00031449547800001011
for a T-terminal forward current traveling wave flowing into the overhead line TN section,
Figure BDA00031449547800001012
in order to flow into the T-side reverse current traveling wave of the overhead line TN section,
Figure BDA00031449547800001013
in order to flow out of the forward current traveling wave at the T-end of the TN section of the overhead line,
Figure BDA00031449547800001014
in order to flow out of the T-end reverse current traveling wave of the overhead line TN section,
Figure BDA00031449547800001015
is a forward current traveling wave at the N end of the TN section of the overhead line,
Figure BDA00031449547800001016
the reverse current traveling wave is the reverse current traveling wave of the N end of the TN section of the overhead line;
Figure BDA00031449547800001017
for the power frequency current flowing into the T end of the TN end of the overhead line,
Figure BDA00031449547800001018
the power frequency current flows out of a T end of a TN end of the overhead line;
Z line is the wave impedance of an overhead line, Z cable Is the wave impedance of the cable run.
By solving the two formulas, the forward traveling wave differential quantity D for judging the fault section can be obtained 1 Sum reverse traveling wave differential D 2 Respectively as follows:
Figure BDA00031449547800001019
wherein: d 1 Is the forward traveling wave differential momentum, D 2 Is reversedThe difference momentum of the traveling wave is moved forward,
Figure BDA0003144954780000111
is a forward current traveling wave flowing out of the C end of the MC section of the overhead line,
Figure BDA0003144954780000112
in order to flow out of the C-end reverse current traveling wave of the MC section of the overhead line,
Figure BDA0003144954780000113
in order to flow out of the forward current traveling wave at the T-end of the TN section of the overhead line,
Figure BDA0003144954780000114
for the purpose of flowing out a T-end reverse current traveling wave, L, of a TN section of an overhead line CT Line length, gamma, of CT section of cable line cable Is the transmission constant of the cabling.
When the fault point F occurs in the overhead line MC section, since the forward traveling wave of the N-terminal obtained based on the measured value of the voltage and current on the N-side and the long-line equation under the influence of the fault point F is equal to the actual value, but the forward traveling wave of the C-terminal obtained based on the measured value of the voltage and current on the M-side and the long-line equation does not match the actual value, the actual forward traveling wave of the C-terminal after the fault needs to be calculated. After the actual forward current traveling wave of the C end is obtained through the calculation formula of the two directional current traveling waves, the forward current traveling wave differential quantity is calculated according to the actual forward current traveling wave of the C end and the forward current traveling wave of the N end, and the forward traveling wave differential quantity D can be obtained 1 Comprises the following steps:
Figure BDA0003144954780000115
wherein: d 1 Is the forward traveling wave differential of the cable hybrid line MN,
Figure BDA0003144954780000116
is the power frequency current at the fault point F, gamma line Is the transmission constant, gamma, of an overhead line cable Is the transmission constant of the cable line, L CT Is the line length, L, of the CT section of the cable line FC Distance, Z, from fault point F to C end of MC section of overhead line line Is the wave impedance of an overhead line, Z cable Is the wave impedance of the cable line.
The same can deduce the reverse traveling wave differential momentum D 2 Comprises the following steps:
Figure BDA0003144954780000117
wherein: d 2 Mixes the reverse traveling wave differential momentum of the line MN for the cable,
Figure BDA0003144954780000121
is the power frequency current at the fault point F, gamma line Is the transmission constant, L, of the overhead line CT Is the line length, L, of the CT section of the cable line FC Distance, Z, from fault point F to C end of MC section of overhead line line Is the wave impedance of an overhead line, Z cable Is the wave impedance of the cable run.
So by D 1 And D 2 The available fault section decision function P is:
Figure BDA0003144954780000122
using the property of absolute values for the above formula
Figure BDA0003144954780000123
Can obtain
Figure BDA0003144954780000124
And is
Figure BDA0003144954780000125
Then
Figure BDA0003144954780000126
From this it can be derived
Figure BDA0003144954780000131
The judgment function has the following numerical characteristics under the condition that the fault point F is in the section of the overhead line MC:
Figure BDA0003144954780000132
similarly, when the fault point is in the cable CT section, the forward traveling wave D is aligned 1 And a reverse traveling wave D 2 And (3) calculating:
Figure BDA0003144954780000133
from this it can be derived
Figure BDA0003144954780000134
It is shown that in the case of a fault F in the section of the cable CT, the decision function has the following numerical characteristics:
Figure BDA0003144954780000135
similarly, when the fault point F is in the overhead line TN section, the forward traveling wave D is aligned 1 And a reverse traveling wave D 2 And (3) calculating:
Figure BDA0003144954780000136
thus, it is possible to provide
Figure BDA0003144954780000141
The judgment function has the following numerical characteristics under the condition that the fault point F is in the overhead line TN section:
Figure BDA0003144954780000142
the above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.

Claims (6)

1. A fault section judgment method for a power distribution network cable hybrid line is characterized by comprising the following steps:
the method comprises the following steps that firstly, a data acquisition module (1) acquires voltage signals and current signals at two ends of a cable hybrid line of a power distribution network, and the data acquisition module (1) transmits acquired voltage signal data and current signal data to a data analysis module (2);
step two, the data analysis module (2) acquires power frequency voltage and power frequency current according to the acquired voltage signal data and current signal data, and then acquires forward current traveling wave differential quantity and reverse current traveling wave differential quantity according to the power frequency voltage and the power frequency current;
step three, the data analysis module (2) determines a fault section judgment function according to the forward current traveling wave differential momentum and the reverse current traveling wave differential momentum, the data analysis module (2) calculates a fault section judgment value through the fault section judgment function, the data analysis module (2) compares the fault section judgment value with a preset threshold value, and the data analysis module (2) obtains a specific fault section through a comparison result;
in the second step, the calculation formula of the forward current traveling wave differential quantity obtained according to the power frequency voltage and the power frequency current is as follows:
Figure FDA0003769593960000011
wherein: d 1 Forward current traveling wave differential momentum;
Figure FDA0003769593960000012
is a forward current traveling wave flowing out of a connection point C of a first section overhead line and a middle section cable line;
Figure FDA0003769593960000013
is a forward current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line; e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cable run;
in the second step, the calculation formula of the reverse current traveling wave differential quantity obtained according to the power frequency voltage and the power frequency current is as follows:
Figure FDA0003769593960000021
wherein: d 2 Traveling wave differential momentum is reverse current;
Figure FDA0003769593960000022
is a reverse current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line;
Figure FDA0003769593960000023
is a reverse current traveling wave flowing out of a connection point C of the first section of overhead line and the middle section of cable line; e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cable run;
in the third step, the preset threshold includes a first preset threshold and a second preset threshold, and the expression of the first preset threshold is as follows:
Figure FDA0003769593960000024
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cable run;
the expression of the second preset threshold is as follows:
Figure FDA0003769593960000025
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cabling.
2. The method for determining the fault section based on the power distribution network cable hybrid line according to claim 1, wherein a first section of the power distribution network cable hybrid line is an overhead line, a middle section of the power distribution network cable hybrid line is a cable line, and an end section of the power distribution network cable hybrid line is an overhead line.
3. The method for determining the fault section of the power distribution network cable hybrid line according to claim 1, wherein in the second step, the power frequency voltage and the power frequency current are obtained by performing fourier transform on the collected voltage signal data and current signal data.
4. The method for determining the fault section based on the power distribution network cable hybrid line according to claim 1, wherein the formula for calculating the fault section determination value in step three is as follows:
Figure FDA0003769593960000031
wherein: p is a fault section judgment value, D 1 Is a forward current traveling wave differential momentum, D 2 Traveling wave differential momentum for reverse current.
5. The method for determining the fault section based on the power distribution network cable hybrid line according to claim 1, wherein the fault section is determined according to the following specific steps: when the fault section judgment value is smaller than a first preset threshold value, a fault occurs in a head-end overhead line area; when the fault section judgment value is equal to a first preset threshold value, a fault occurs at the connecting point of the first section of overhead line and the cable line; when the fault section judgment value is larger than a first preset threshold value and smaller than a second preset threshold value, a fault occurs in a cable line area; when the fault section judgment value is equal to a second preset threshold value, the fault occurs at the connecting point of the cable line and the tail end overhead line; and when the fault section judgment value is larger than a second preset threshold value, the fault occurs in the tail end overhead line area.
6. A fault section judgment system based on a power distribution network cable hybrid line is characterized in that,
the cable fault section judgment system comprises a data acquisition module (1) and a data analysis module (2), wherein the data acquisition module (1) is connected with the data analysis module (2), the data acquisition module (1) is used for acquiring voltage signal data and current signal data at two ends of a cable hybrid line, and the data analysis module (2) is used for judging a fault section;
when the data analysis module (2) judges a fault section, acquiring power frequency voltage and power frequency current according to the acquired voltage signal data and current signal data, and acquiring forward current traveling wave differential momentum and reverse current traveling wave differential momentum according to the power frequency voltage and the power frequency current; the data analysis module (2) determines a fault section judgment function according to the forward current traveling wave differential quantity and the reverse current traveling wave differential quantity, the data analysis module (2) calculates a fault section judgment value through the fault section judgment function, the data analysis module (2) compares the fault section judgment value with a preset threshold value, and the data analysis module (2) obtains a specific fault section through a comparison result;
the data analysis module (2) obtains a calculation formula of the forward current traveling wave differential quantity according to the power frequency voltage and the power frequency current, and the calculation formula is as follows:
Figure FDA0003769593960000044
wherein: d 1 Forward current traveling wave differential momentum;
Figure FDA0003769593960000045
is a forward current traveling wave flowing out of a connection point C of a first section overhead line and a middle section cable line;
Figure FDA0003769593960000046
is a forward current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line; e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is a radical of an alcohol CT Is the length of the cable run;
the data analysis module (2) obtains the calculation formula of the difference quantity of the reverse current traveling wave according to the power frequency voltage and the power frequency current as follows:
Figure FDA0003769593960000041
wherein: d 2 Traveling wave differential momentum is reverse current;
Figure FDA0003769593960000042
is a reverse current traveling wave flowing out of a connection point T of the tail section overhead line and the middle section cable line;
Figure FDA0003769593960000043
is a reverse current traveling wave flowing out of a connection point C of the first section of overhead line and the middle section of cable line; e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is a radical of an alcohol CT Is the length of the cable run;
the preset threshold comprises a first preset threshold and a second preset threshold, and the expression of the first preset threshold is as follows:
Figure FDA0003769593960000051
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cable run;
the expression of the second preset threshold is as follows:
Figure FDA0003769593960000052
wherein: e is a natural constant; gamma ray cable Is the transmission constant of the cable run; l is CT Is the length of the cabling.
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