CN110082636B - Power cable fault positioning method and system - Google Patents

Power cable fault positioning method and system Download PDF

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CN110082636B
CN110082636B CN201910374330.XA CN201910374330A CN110082636B CN 110082636 B CN110082636 B CN 110082636B CN 201910374330 A CN201910374330 A CN 201910374330A CN 110082636 B CN110082636 B CN 110082636B
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power cable
current
voltage
cable
head end
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CN110082636A (en
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朱博
魏新劳
聂洪岩
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Harbin University of Science and Technology
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Harbin University of Science and Technology
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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
    • G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing

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  • Locating Faults (AREA)

Abstract

The invention discloses a power cable fault positioning method and a system, wherein the method comprises the following steps: acquiring head end current, tail end current, head end voltage and tail end voltage of a power cable with a fault; calculating the line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable; calculating the line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage and the line wave impedance of the power cable; and calculating the distance from the fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient. The method and the system for positioning the power cable fault can calculate the distance from the fault point to the head end of the power cable more accurately, and improve the positioning precision of the fault point.

Description

Power cable fault positioning method and system
Technical Field
The invention relates to the technical field of fault detection, in particular to a power cable fault positioning method and system.
Background
Cross-linked polyethylene (XLPE) power cables have been widely used in power transmission and distribution networks of power systems at various voltage levels, become an important link for forming urban power supply and main grid due to the advantages of good insulating property, mechanical property, thermal property, power supply reliability and the like, and are continuously developed to the fields of high voltage and ultrahigh voltage. In the initial stage of operation (generally 1-5 years) of an XPLE cable line, the quality problems of cables, accessories or laying and installation are easy to generate faults; in the middle period of operation (5-25 years), the probability of the fault of the cable line is low, but the fault types of the cable are more, such as the cable insulation damage caused by external force damage, the cable accessory interface discharge, the cable insulation aging and the like, and the line fault is caused; at the end of commissioning (after 25 years), the probability of cable line failure due to aging of cable accessories or electrical and thermal aging of cable insulation is greatly increased. The operation experience of a large number of XLPE cables shows that cable line faults are important causes of power grid accidents. After the cable is put into use, the cable is influenced by not only electric field action, mechanical action and thermal action, but also environmental factors, and the cable insulation is easy to age under the combined action of the factors. Therefore, the insulation condition of the cable is monitored in real time, the reliability of power supply of a power grid is guaranteed, and the method has important significance for the development of the whole power system and national economy.
The single-core cable is adopted for the high-voltage long-distance power cable, and a hollow transformer can be regarded between a cable core and a metal sheath, wherein the cable core is equivalent to a primary winding of the transformer, and the metal sheath is equivalent to a secondary winding of the transformer. When alternating current passes through the cable core, an alternating magnetic field is generated around the cable core, the metal protective layer generates induced voltage when being in the alternating magnetic field, and when a loop is formed between the metal protective layer and the ground, induced current flows through the metal protective layer. The induced voltage in the metal sheath is proportional to the length of the cable, and when the current on the bus is large, a high value of voltage is induced on the metal sheath of the cable, so that the high value of voltage may cause damage to the insulation of the cable. Therefore, when the length of the power cable is more than 1000 meters, a metal sheath cross-connection mode is generally adopted, the connection mode is that the three-phase power cable is divided into a plurality of large sections, each large section of each phase is divided into three small sections with equal length, the metal sheaths are cross-connected at two middle sections of each phase by using coaxial cables, and the metal sheaths at two ends of each large section of each phase are connected respectively and then grounded. Fig. 1 is a schematic diagram of transposition wiring of a cable body of an XLPE cable under metal sheath cross-interconnection, and fig. 2 is a schematic diagram of transposition wiring of a cable body of an XLPE cable under metal sheath cross-interconnection. After the long-distance power cables are connected in such a way, the sum of the induced voltages of the cables of each phase is almost zero.
The leakage current of the cable consists of resistive current and capacitive current, when the XLPE cable is in good insulation condition, the capacitive current mainly flows through the cable insulation, the resistive current accounts for a very small proportion, the ratio of the resistive current to the capacitive current is generally 4-10 times, the phase angle is 90 degrees different, and the influence of the change of the resistive current flowing through the cable insulation on the effective value of the leakage current is small. However, when the insulation of the cable is defective or aged, the resistance current changes greatly, the resistance current has a great influence on the change of the leakage current, and the capacitance current does not change greatly. Therefore, the condition of cable insulation degradation can be accurately reflected by carrying out online monitoring on the resistive current flowing through the main insulation of the XLPE cable. For a long-distance power cable, there is an interconnection mode of metal sheath cross-interconnection, so that leakage current flowing through the cable insulation flows into the metal sheath through the cable insulation, and each small section of metal sheath of the phase cable is connected with each small section of metal sheath of other two-phase cables, so that the leakage current in the metal sheath is the sum of the leakage currents flowing through each small section of the three-phase cable, and the interconnection mode brings difficulty to the separation of resistive currents. Furthermore, a long-distance power cable has a voltage drop problem, and a voltage drop is formed on the resistance and residual inductance of a cable core due to a load current flowing through the cable, so that a large difference occurs between voltages to ground at two ends of the cable, and the difference also changes along with the change of the load current flowing through the cable. This all presents difficulties in determining the location of a fault in a long distance power cable.
At present, the methods for fault location mainly include an impedance method, a traveling wave method and a fault analysis method. The impedance method is to calculate the impedance of the whole loop by using the voltage and the current during the fault, calculate the distance from a fault point to a detection point by the functional relation between the line impedance and the line length, and can not eliminate the calculation error in principle because the cable is simplified into a centralized parameter model by the impedance method without considering the existence of distributed capacitance; the traveling wave method is to position the fault point by utilizing the relation between the time of traveling wave propagation of voltage or current generated by the fault point to a detection point and the wave speed when the fault occurs, a student detects a first traveling wave head by adopting a double-end traveling wave distance measurement method to position the fault point, but the traveling wave is seriously attenuated when being propagated in a long-distance cable, a traveling wave signal can not be detected at one end or two ends of the cable, and the long-distance cable has a plurality of sheath crossing interconnection points, so that the complex folding and reflection can occur in the traveling wave propagation process, and the first traveling wave and the reflected traveling wave of the fault point can not be distinguished; the fault analysis method is to calculate the position of the fault point according to the functional relation between the voltage and current recorded during the fault and the fault distance. Fault analysis methods can be generally divided into single-ended ranging and double-ended ranging methods. The single-end distance measurement method is greatly influenced by the impedance and the transition resistance of a line opposite-end system; the double-end distance measurement method has the advantages that the influence of transition resistance is eliminated, accurate fault location can be achieved on the premise that the accuracy of sampled data and line parameters are guaranteed, when the fault distance is calculated by the double-end distance measurement method, not only are double-end voltage and current values needed, but also primary parameter values of a cable need to be known, wave impedance and a propagation coefficient are calculated according to the primary parameter values, the fault distance can be calculated, when the cable breaks down, the primary parameter of the cable at the moment can not be calculated through a formula, accurate values of the wave impedance and the propagation coefficient can not be obtained, the calculated fault distance has large errors, and accurate fault positions can not be determined. Most of the existing distance measurement algorithms utilize a search iteration method to perform fault location, the distance measurement accuracy is influenced by the iteration times, the iteration step length and other factors, and a large amount of calculation is needed to obtain higher accuracy, so that the time consumption is too long, and the fault point position cannot be quickly found out.
In summary, a fault location method is urgently needed to judge the fault position when a long-distance power cable has a fault, repair and replace the fault cable in time, and has important significance for ensuring the safe operation of the power cable and the development of the whole power system and national economy.
Disclosure of Invention
The invention aims to provide a method and a system for positioning the fault of a power cable by measuring the voltage and current signals of the head end and the tail end of the cable, which have the advantage of improving the positioning accuracy of a cable fault point.
In order to achieve the purpose, the invention provides the following scheme:
a power cable fault location method, comprising:
acquiring head end current, tail end current, head end voltage and tail end voltage of a power cable with a fault;
calculating line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable;
calculating the line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage and the line wave impedance of the power cable;
and calculating the distance from the fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient.
Optionally, calculating the line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable specifically includes:
calculating the line wave impedance Z according to the following formulac：
Figure BDA0002051138700000041
In the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000042
is the head-end current of the power cable,
Figure BDA0002051138700000043
is the end current of the power cable,
Figure BDA0002051138700000044
is the head end voltage of the power cable,
Figure BDA0002051138700000045
is the terminal voltage of the power cable.
Optionally, the calculating a line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage, and the line wave impedance of the power cable specifically includes:
the line propagation coefficient γ is calculated according to the following formula:
Figure BDA0002051138700000046
in the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000047
is the head-end current of the power cable,
Figure BDA0002051138700000048
is the end current of the power cable,
Figure BDA0002051138700000049
is the head end voltage of the power cable,
Figure BDA00020511387000000410
for the end voltage of the power cable,/, of the total length of the power cable
Figure BDA00020511387000000411
ZcIs the line wave impedance.
Optionally, the calculating a distance from a fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient specifically includes:
calculating the distance y from the fault point to the head end of the power cable according to the following formula:
Figure BDA00020511387000000412
in the formula (I), the compound is shown in the specification,
Figure BDA00020511387000000413
is the head-end current of the power cable,
Figure BDA00020511387000000414
is the end current of the power cable,
Figure BDA00020511387000000415
is head end power of the power cableThe pressure is applied to the inner wall of the cylinder,
Figure BDA00020511387000000416
for the end voltage of the power cable,/, of the total length of the power cable
Figure BDA00020511387000000417
The invention also provides a power cable fault positioning system, comprising:
the data acquisition module is used for acquiring head end current, tail end current, head end voltage and tail end voltage of the power cable with faults;
the line wave impedance calculation module is used for calculating the line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable;
the line propagation coefficient calculation module is used for calculating the line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage and the line wave impedance of the power cable;
and the fault positioning module is used for calculating the distance from a fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient.
Optionally, the line wave impedance calculating module specifically includes:
a line wave impedance calculating unit for calculating the line wave impedance Z according to the following formulac：
Figure BDA0002051138700000051
In the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000052
is the head-end current of the power cable,
Figure BDA0002051138700000053
is the end current of the power cable,
Figure BDA0002051138700000054
is the head end voltage of the power cable,
Figure BDA0002051138700000055
is the terminal voltage of the power cable.
Optionally, the line propagation coefficient calculating module specifically includes:
a line propagation coefficient calculation unit for calculating the line propagation coefficient γ according to the following formula:
Figure BDA0002051138700000056
in the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000057
is the head-end current of the power cable,
Figure BDA0002051138700000058
is the end current of the power cable,
Figure BDA0002051138700000059
is the head end voltage of the power cable,
Figure BDA00020511387000000510
for the end voltage of the power cable,/, of the total length of the power cable
Figure BDA00020511387000000511
ZcIs the line wave impedance.
Optionally, the fault location module specifically includes:
a fault location unit for calculating the distance y from the fault point to the head end of the power cable according to the following formula:
Figure BDA00020511387000000512
in the formula (I), the compound is shown in the specification,
Figure BDA00020511387000000513
is the head-end current of the power cable,
Figure BDA00020511387000000514
is the end current of the power cable,
Figure BDA00020511387000000515
is the head end voltage of the power cable,
Figure BDA00020511387000000516
for the end voltage of the power cable,/, of the total length of the power cable
Figure BDA0002051138700000061
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a power cable fault positioning method and a power cable fault positioning system, wherein the head end current, the tail end current, the head end voltage and the tail end voltage of a power cable with a fault are obtained through measurement, and the line wave impedance and the line propagation coefficient can be calculated; when power grid harmonic waves, frequency fluctuation, synchronous errors and voltage errors caused by different ground potentials exist, the method is less influenced, and the position of a fault point can be accurately calculated; in addition, the long-distance power cable fault location method based on the double-end voltage and current synchronous sampling method is suitable for the evaluation of the insulation condition of the long-distance power cable in any connection mode and in any high-voltage grade, no matter whether the metal sheaths are interconnected in a cross mode or not, and is also suitable for the short-distance cable.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic diagram of transposition-free connection of a cable body of an XLPE cable under cross-connection of metal sheaths in the background art of the invention;
FIG. 2 is a schematic diagram of transposition wiring of a cable body of an XLPE cable under cross-connection of metal sheaths in the background art of the invention;
FIG. 3 is a flow chart of a power cable fault location method in an embodiment of the present invention;
FIG. 4 is an AC steady-state distributed equivalent circuit diagram of a single-phase cable according to an embodiment of the present invention;
FIG. 5 is a block diagram of a power cable fault location system in an embodiment of the present invention;
fig. 6 is a schematic diagram of a power cable fault locating device according to an embodiment of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method and a system for positioning the fault of a power cable by measuring the voltage and current signals of the head end and the tail end of the cable, which have the advantage of improving the positioning accuracy of a cable fault point.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example (b):
fig. 3 is a flowchart of a power cable fault location method according to an embodiment of the present invention, and as shown in fig. 3, a power cable fault location method includes:
step 101: and acquiring head end current, tail end current, head end voltage and tail end voltage of the power cable with the fault.
Step 102: the line wave impedance of the power cable is calculated from the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable.
Calculating the line wave impedance Z according to the following formulac：
Figure BDA0002051138700000071
In the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000072
is the head-end current of the power cable,
Figure BDA0002051138700000073
is the end current of the power cable,
Figure BDA0002051138700000074
is the voltage at the head end of the power cable,
Figure BDA0002051138700000075
is the end voltage of the power cable.
Step 103: and calculating the line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage and the line wave impedance of the power cable.
The line propagation coefficient γ is calculated according to the following formula:
Figure BDA0002051138700000076
in the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000077
is the head-end current of the power cable,
Figure BDA0002051138700000078
is the end current of the power cable,
Figure BDA0002051138700000079
is the voltage at the head end of the power cable,
Figure BDA00020511387000000710
for the end voltage of the power cable, l being the total length of the power cable
Figure BDA00020511387000000711
ZcIs the line wave impedance.
Step 104: and calculating the distance from the fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient.
The distance y from the fault point to the head end of the power cable is calculated according to the following formula:
Figure BDA0002051138700000081
in the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000082
is the head-end current of the power cable,
Figure BDA0002051138700000083
is the end current of the power cable,
Figure BDA0002051138700000084
is the voltage at the head end of the power cable,
Figure BDA0002051138700000085
for the end voltage of the power cable, l being the total length of the power cable
Figure BDA0002051138700000086
The derivation of the distance from the fault point to the head end of the power cable is as follows:
for the long-distance cable, the problem of cross interconnection exists, although the metal protective layer of the three-phase cable is cross-interconnected at each subsection, the conductive wire core of the three-phase cable is not cross-interconnected, and the resistive current and the capacitive current flowing through the main insulation of the three-phase cable flow to the metal protective layer of the cable through the conductive wire core of the cable and the main insulation of the cable; therefore, the current flowing through the conductive wire cores at the two ends of the cable is measured, and the current flowing through the main insulation of the three-phase cable is equal to the current flowing into the conductive wire core at the head end of each phase of cable minus the current flowing into the conductive wire core at the tail end of the same phase of cable according to the current continuity principle and considering the passivity of the cable. When half of the sum of the voltage phasors applied to the two terminals of each phase of cable is taken as a reference voltage to calculate the insulation resistance of the cable, the result is not influenced by the change of load current flowing through the cable. For the problem of voltage drop of the cable, any phase of the three-phase power cable can be analyzed, and an alternating current steady-state distributed equivalent circuit of the single-phase cable is shown in fig. 4. As shown in figure 4 of the drawings,
Figure BDA0002051138700000087
and
Figure BDA0002051138700000088
respectively the head end current and the tail end current flowing through the phase cable core;
Figure BDA0002051138700000089
and
Figure BDA00020511387000000810
voltages of the head end current and the tail end current of the phase cable respectively; r0The equivalent resistance per unit length of the cable core is omega/m; g0The equivalent conductance is the equivalent conductance per unit length of the main insulation of the cable, S/m; l is0The equivalent inductance is H/m of the unit length of the cable core; c0Equivalent capacitance of main insulation of the cable in unit length, F/m; z0The equivalent impedance is the unit length of the cable core; y is0Is the equivalent admittance per unit length of the cable core.
Assuming that the total length of the cable is 2l, the angular frequency is omega, at any point x in the length of the cable, a micro-segment dx is taken, and the voltage and the current at the point x are
Figure BDA00020511387000000811
And
Figure BDA00020511387000000812
the voltage and current at the point x + dx is
Figure BDA00020511387000000813
And
Figure BDA00020511387000000814
for point x:
according to kirchhoff's current law, the following can be obtained:
Figure BDA00020511387000000815
according to kirchhoff's voltage law, the following can be obtained:
Figure BDA0002051138700000091
the formulas (1) and (2) are obtained in a combined manner:
Figure BDA0002051138700000092
let the propagation coefficient of the cable be gamma and the wave impedance be ZcThen, then
Figure BDA0002051138700000093
The formula (4) can be substituted for the formula (3):
Figure BDA0002051138700000094
assuming that the current, voltage at the cable head end is a known quantity, solution (5) can be found:
Figure BDA0002051138700000095
the formula (6) can be rewritten as
Figure BDA0002051138700000096
When x is 2l, the voltage and current of the cable end, which are represented by the cable end voltage and current, are obtained as follows:
Figure BDA0002051138700000097
therefore, the voltage difference of the head end and the tail end of the cable expressed by the voltage and the current of the head end of the cable, namely the voltage of the cable is reduced to
Figure BDA0002051138700000101
Similarly, assuming that the current and voltage at the end of the cable are known, equation (5) is solved and rewritten by a hyperbolic function to obtain:
Figure BDA0002051138700000102
when x is 0, the voltage and current at the cable head end, which are represented by the cable head end voltage and current, can be obtained as:
Figure BDA0002051138700000103
the voltage difference between the first end and the last end of the cable can be obtained as follows:
Figure BDA0002051138700000104
subtracting the equation (12) from the equation (9) to obtain:
Figure BDA0002051138700000105
from equation (8), it can be obtained that the difference between the first and last terminals expressed by the cable first terminal voltage and current is:
Figure BDA0002051138700000106
similarly, from equation (11), it can be obtained that the difference between the first and second ends of the current represented by the terminal voltage and the current of the cable is:
Figure BDA0002051138700000107
the difference between formula (14) and formula (15) is adjusted to obtain:
Figure BDA0002051138700000108
multiplying formula (13) by (16) gives:
Figure BDA0002051138700000111
as can be seen from the formula (17), the wave impedance Z of the cablecCan be calculated by the measured values of the head and tail end voltage and the current.
By substituting formula (17) into formula (13), it is possible to obtain:
Figure BDA0002051138700000112
as can be seen from equation (18), the propagation coefficient γ of the cable can also be calculated from the measured values of the head and tail voltages and the current.
Assuming that the power cable has a short-circuit fault at the point F, the distance between the fault point and the head end of the cable is y, and a functional relation formula of the fault point can be obtained according to the cable equivalent circuit under a steady state, such as a formula (7) and a formula (10).
The voltage of a fault point can be calculated by using the voltage and the current of the cable head end according to the formula (7)
Figure BDA0002051138700000113
Comprises the following steps:
Figure BDA0002051138700000114
meanwhile, according to the formula (10), the voltage of the fault point can be calculated by using the terminal voltage and the current of the cable as follows:
Figure BDA0002051138700000115
wherein R isFFor the transition resistance, the transition resistance can be eliminated according to the principle that voltages at the same point are equal in combination of a vertical type (19) and a formula (20), and the distance y between a fault point and the head end of the cable is solved as follows:
Figure BDA0002051138700000116
the distance from the fault point to the head end can be calculated by the formula (21), when the cable insulation has a fault, the unit length equivalent conductance and the unit length equivalent capacitance of the cable insulation can change, and then the values of the wave impedance Zc and the propagation coefficient gamma can also change according to the calculation formula of the cable size, which causes an error in the calculation by the formula (21). The method provided by the invention can calculate the values of the wave impedance Zc and the propagation coefficient gamma according to the functional relation by measuring the voltage and current signals of the head end and the tail end of the cable in real time, but not obtain the two values according to a calculation formula of the cable size, so that the obtained fault position is more accurate. By substituting equations (17) and (18) into equation (21), the distance y from the fault point to the cable head end can be obtained:
Figure BDA0002051138700000121
from equation (22), it can be seen that the fault distance can be calculated only if the voltage across the cable, the current transient, and the cable length are known. It can also be found that the method of the present invention is applicable to both long-distance cables and short-distance voltages, regardless of the presence of cross-connections, by synchronously sampling the instantaneous values of the voltage and current at both ends.
According to the invention, the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable with faults are obtained through measurement, the line wave impedance and the line propagation coefficient can be calculated, and the line wave impedance and the line propagation coefficient are not calculated by adopting a calculation formula (4) of cable parameters (including the diameter of the cable, the thickness of each layer of the cable and the like), so that errors caused by the line wave impedance and the line propagation coefficient calculated through manual calculation according to the diameter of the cable and the thickness of each layer of the cable are avoided, the line wave impedance and the line propagation coefficient are obtained through calculation of the voltage and the current of the head end and the tail end of the cable, the distance from a fault point to the head end of the power cable can be calculated more.
Fig. 5 is a block diagram of a power cable fault location system according to an embodiment of the present invention. As shown in fig. 5, a power cable fault location system includes:
and the data acquisition module 1 is used for acquiring head end current, tail end current, head end voltage and tail end voltage of the power cable with faults.
And the line wave impedance calculation module 2 is used for calculating the line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable.
The line wave impedance calculation module 2 comprises a lineA wave impedance calculating unit for calculating line wave impedance Z according to the following formulac：
Figure BDA0002051138700000122
In the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000123
is the head-end current of the power cable,
Figure BDA0002051138700000124
is the end current of the power cable,
Figure BDA0002051138700000125
is the voltage at the head end of the power cable,
Figure BDA0002051138700000126
is the end voltage of the power cable.
And the line propagation coefficient calculation module 3 is used for calculating the line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage and the line wave impedance of the power cable.
The line propagation coefficient calculation block 3 includes a line propagation coefficient calculation unit for calculating a line propagation coefficient γ according to the following formula:
Figure BDA0002051138700000131
in the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000132
is the head-end current of the power cable,
Figure BDA0002051138700000133
is the end current of the power cable,
Figure BDA0002051138700000134
as electricityThe voltage at the head end of the cable,
Figure BDA0002051138700000135
for the end voltage of the power cable, l being the total length of the power cable
Figure BDA0002051138700000136
ZcIs the line wave impedance.
And the fault positioning module 4 is used for calculating the distance from the fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient.
The fault localization module 4 comprises a fault localization unit for calculating the distance y from the fault point to the head end of the power cable according to the following formula:
Figure BDA0002051138700000137
in the formula (I), the compound is shown in the specification,
Figure BDA0002051138700000138
is the head-end current of the power cable,
Figure BDA0002051138700000139
is the end current of the power cable,
Figure BDA00020511387000001310
is the voltage at the head end of the power cable,
Figure BDA00020511387000001311
for the end voltage of the power cable, l being the total length of the power cable
Figure BDA00020511387000001312
Fig. 6 is a schematic diagram of a power cable fault location device according to an embodiment of the present invention. As shown in fig. 6, a power cable fault location system includes:
the first voltage transformer 201 is arranged at the head end of the power cable, and the first voltage transformer 201 is used for measuring the voltage at the head end of the power cable with a fault.
A second voltage transformer 202, the second voltage transformer 202 being arranged at the end of the power cable for measuring the faulty power cable end voltage.
The first current transformer 203, the first current transformer 203 is arranged at the head end of the power cable for measuring the head end current of the power cable with fault.
A second current transformer 204, the second current transformer 204 being arranged at the end of the power cable for measuring a faulty power cable end current.
The first microprocessor 205 is configured to control the first voltage transformer 201 to collect the head end voltage and control the first current transformer 203 to collect the head end current.
And a second microprocessor 206 for controlling the second voltage transformer 202 to collect the terminal voltage and controlling the second current transformer 204 to collect the terminal current.
A first data transmission module 207, the first data transmission module 207 being connected to the first microprocessor 205 for transmitting the head end voltage and head end current data.
And a second data transmitting module 208, wherein the second data transmitting module 208 is connected with the second microprocessor 206 and is used for transmitting the terminal voltage and terminal current data.
The main control system comprises a data receiving module 209 and an upper computer 210; the data receiving module 209 is configured to receive the head-end voltage and head-end current data sent by the first data sending module 207, and receive the tail-end voltage and tail-end current data sent by the second data sending module 208; the upper computer 210 is used for calculating the line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable; the upper computer 210 is further configured to calculate a line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage, and the line wave impedance of the power cable; the upper computer 210 is further configured to calculate a distance from the fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient. The calculation method of the upper computer is the same as the power cable fault positioning method.
The input end of the first signal acquisition module 211 is respectively connected with the first voltage transformer 201 and the first current transformer 203, and the output end of the first signal acquisition module 211 is connected with the first microprocessor 205; the first signal acquisition module 211 is configured to acquire a head end voltage and a head end current, and is configured to convert the acquired head end voltage and head end current signals into digital signals.
The input end of the second signal acquisition module 212 is connected with the second voltage transformer 202 and the second current transformer 204 respectively, and the output end of the second signal acquisition module 212 is connected with the second microprocessor 206; the second signal collecting module 212 is used for collecting the terminal voltage and the terminal current, and for converting the collected terminal voltage and terminal current signals into digital signals.
The first GPS receiving module 213, the first GPS receiving module 213 is connected to the first microprocessor 205, and is configured to receive time information sent by a satellite, and send a synchronous second pulse signal to the first microprocessor 205, where the first microprocessor 205 controls the first signal collecting module 211 to collect a head-end voltage and a head-end current according to the first synchronous second pulse signal.
The second GPS receiving module 214, the second GPS receiving module 214 is connected to the second microprocessor 206, and is configured to receive the time information sent by the satellite and send the synchronous pulse-per-second signal to the second microprocessor 206, and the second microprocessor 206 controls the second signal collecting module 212 to collect the terminal voltage and the terminal current according to the synchronous pulse-per-second signal.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In summary, this summary should not be construed to limit the present invention.

Claims (2)

1. A power cable fault location method is characterized by comprising the following steps:
acquiring head end current, tail end current, head end voltage and tail end voltage of a power cable with a fault;
calculating the line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable, and specifically comprises the following steps:
calculating the line wave impedance Z according to the following formulac：
Figure FDA0002819710880000011
In the formula (I), the compound is shown in the specification,
Figure FDA0002819710880000012
is the head-end current of the power cable,
Figure FDA0002819710880000013
is the end current of the power cable,
Figure FDA0002819710880000014
is the head end voltage of the power cable,
Figure FDA0002819710880000015
is the terminal voltage of the power cable;
calculating the line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage and the line wave impedance of the power cable, and specifically comprising the following steps:
the line propagation coefficient γ is calculated according to the following formula:
Figure FDA0002819710880000016
in the formula (I), the compound is shown in the specification,
Figure FDA0002819710880000017
is the head-end current of the power cable,
Figure FDA0002819710880000018
is the end current of the power cable,
Figure FDA0002819710880000019
is the head end voltage of the power cable,
Figure FDA00028197108800000110
for the end voltage of the power cable,/, of the total length of the power cable
Figure FDA00028197108800000111
ZcIs the line wave impedance;
calculating the distance from the fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient, and specifically comprising:
calculating the distance y from the fault point to the head end of the power cable according to the following formula:
Figure FDA00028197108800000112
in the formula (I), the compound is shown in the specification,
Figure FDA00028197108800000113
is the head-end current of the power cable,
Figure FDA00028197108800000114
is the end current of the power cable,
Figure FDA00028197108800000115
is the head end voltage of the power cable,
Figure FDA00028197108800000116
for the end voltage of the power cable,/, of the total length of the power cable
Figure FDA00028197108800000117
2. A power cable fault location system, comprising:
the data acquisition module is used for acquiring head end current, tail end current, head end voltage and tail end voltage of the power cable with faults;
the line wave impedance calculation module is used for calculating the line wave impedance of the power cable according to the head end current, the tail end current, the head end voltage and the tail end voltage of the power cable;
the line wave impedance calculation module specifically includes:
a line wave impedance calculating unit for calculating the line wave impedance Z according to the following formulac：
Figure FDA0002819710880000021
In the formula (I), the compound is shown in the specification,
Figure FDA0002819710880000022
is the head-end current of the power cable,
Figure FDA0002819710880000023
is the end current of the power cable,
Figure FDA0002819710880000024
is the head end voltage of the power cable,
Figure FDA0002819710880000025
is the terminal voltage of the power cable;
the line propagation coefficient calculation module is used for calculating the line propagation coefficient of the power cable according to the head end current, the tail end current, the head end voltage, the tail end voltage and the line wave impedance of the power cable;
the line propagation coefficient calculation module specifically includes:
a line propagation coefficient calculation unit for calculating the line propagation coefficient γ according to the following formula:
Figure FDA0002819710880000026
in the formula (I), the compound is shown in the specification,
Figure FDA0002819710880000027
is the head-end current of the power cable,
Figure FDA0002819710880000028
is the end current of the power cable,
Figure FDA0002819710880000029
is the head end voltage of the power cable,
Figure FDA00028197108800000210
for the end voltage of the power cable,/, of the total length of the power cable
Figure FDA00028197108800000211
ZcIs the line wave impedance;
the fault positioning module is used for calculating the distance from a fault point to the head end of the power cable according to the line wave impedance and the line propagation coefficient;
the fault location module specifically comprises:
a fault location unit for calculating the distance y from the fault point to the head end of the power cable according to the following formula:
Figure FDA00028197108800000212
in the formula (I), the compound is shown in the specification,
Figure FDA00028197108800000213
is the head-end current of the power cable,
Figure FDA00028197108800000214
is the end current of the power cable,
Figure FDA00028197108800000215
is the head end voltage of the power cable,
Figure FDA00028197108800000216
for the end voltage of the power cable,/, of the total length of the power cable
Figure FDA00028197108800000217
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