CN108152662A - A kind of cross interconnected box fault diagnosis method and system based on earth current - Google Patents

A kind of cross interconnected box fault diagnosis method and system based on earth current Download PDF

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Publication number
CN108152662A
CN108152662A CN201711194012.2A CN201711194012A CN108152662A CN 108152662 A CN108152662 A CN 108152662A CN 201711194012 A CN201711194012 A CN 201711194012A CN 108152662 A CN108152662 A CN 108152662A
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China
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current
cross
phase
box
fault
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柳骏
邹宏亮
李文辉
陈达
黄圣琦
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State Grid Corp of China SGCC
Taizhou Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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State Grid Corp of China SGCC
Taizhou Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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Priority to CN201711194012.2A priority Critical patent/CN108152662A/en
Publication of CN108152662A publication Critical patent/CN108152662A/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
    • G01R31/088—Aspects of digital computing

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  • Engineering & Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

The present invention is intended to provide a kind of cross interconnected box fault diagnosis method and system based on earth current, to solve the problems, such as that the Cable fault examination in prior art is of high cost.In order to realize the purpose, a kind of cross interconnected box fault diagnosis method based on earth current of the present invention, including：Obtain the test earth current of each split-phases of current cross interconnected case first and last end ABC；Obtain the reference ground electric current of cross interconnected case head end and end each split-phases of ABC when cross interconnected case is normal；Failure phase is determined with reference ground electric current according to test earth current.The invention also discloses corresponding systems.Following advantageous effects can be obtained by implementing the present invention：The test earth current of each split-phases of cross interconnected case first and last end ABC need to only be obtained, you can it is at low cost according to test earth current failure judgement phase, and the operating modes such as ground resistance are can effectively avoid on diagnostic accuracy influence, while avoid whole circuit.

Description

Fault diagnosis method and system for cross-connection box based on ground current
Technical Field
The invention relates to the technical field of power cable fault diagnosis and positioning, in particular to a fault diagnosis method and system for a cross-connection box based on grounding current.
Background
Along with the acceleration of the pace of urban construction in China, the demand on power load is sharply increased, more and more power cable lines are formed in urban overhead line reconstruction and underground power grid laying, the cable lines become longer and longer, and in order to effectively reduce the current of a sheath ring layer, the existing long cable lines all adopt a cross interconnection grounding system.
After such faults occur, the equivalent circuit of the circuit in the whole cross interconnection large section is changed, so that the current flowing to the earth ground through the metal sheath is abnormal, and if measures are not taken in time, serious accidents can be caused. For example, a 110kV single-core cable line administered by a certain power supply station fails after two years of operation, and the cable line is checked immediately, and it is found that the inner sheath protector of the cross interconnection box is broken down and burned out at 520m of the main corridor of the cable, and the fault point is broken down and the periphery is burned seriously.
The existing method for detecting the whole cable consumes a large amount of cost, the requirement for a signal acquisition device is high based on traveling wave method fault location, the signal processing difficulty is large, and the equipment consumption is still large when a plurality of points are tested in a segmented mode by a method based on sheath current.
The method and the system can effectively avoid the influence of working conditions such as grounding resistance on the diagnosis accuracy, and simultaneously avoid the whole line by only testing the circulating current grounding current on the grounding wires of the first and the tail ends of the cross interconnection box.
Disclosure of Invention
The invention aims to provide a fault diagnosis method and a fault diagnosis system for a cross-connection box based on grounding current, and aims to solve the problem of high cost of cable fault detection in the prior art.
In order to achieve the purpose, the invention provides a fault diagnosis method of a cross-connection box based on grounding current, which comprises the following steps:
obtaining test grounding currents of all split phases of ABC at the head end and the tail end of the current cross interconnection box;
acquiring reference grounding currents of ABC split phases at the head end and the tail end of a cross interconnection box when the cross interconnection box is normal;
and determining a fault phase according to the test grounding current and the reference grounding current.
Preferably, the determining the fault phase according to the test ground current and the reference ground current includes: judging whether a cross interconnection wiring error fault exists or not; and if the fault of the cross interconnection wiring does not exist, judging that the phase, of which the head end and the tail end are not equal and the comparison result with the reference grounding current exceeds a set threshold value, in the test grounding current is the fault phase.
Preferably, the determining the fault phase according to the test ground current and the reference ground current includes: acquiring the unbalance degree of each phase separation according to the test grounding current, and acquiring the ratio of the test grounding current and the load current of each phase separation according to the test grounding current; and when the ratio exceeds a preset ratio threshold and the unbalance exceeds a preset balance threshold, judging that a fault occurs.
Preferably, when it is determined that a fault occurs, the i-phase of the cross-connect box is determined to have a ground fault when it satisfies the following formula:
(Ii2＞Ii1∩Ii2＞Ii2N)∪(Ii1＞Ii2∩Ii1＞Ii1N)，i∈{A,B,C}
wherein,
IA1the test grounding current of the phase separation of the head end A of the current cross interconnection box is represented;
IB1the test grounding current of the current cross-connection box head end B split phase is represented;
IC1the test grounding current of the current cross-connection box head end C split phase is represented;
IA2representing the test grounding current of the current cross-connection box tail end A split phase;
IB2representing the test grounding current of the current cross-connection box tail end B split phase;
IC2representing the test grounding current of the current cross-connection box tail end C split phase;
IA1Nthe reference grounding current of the phase A is shown when the head end of the cross interconnection box is normal;
IB1Nb phase-splitting reference grounding current which represents the head end of the cross interconnection box when the cross interconnection box is normal;
IC1Nthe reference grounding current of the C phase splitting is expressed when the head end of the cross interconnection box is normal;
IA2Nthe reference grounding current of the phase A is shown when the cross interconnection box is normal at the tail end of the cross interconnection box;
IB2Nb phase-splitting reference grounding current which represents the tail end of the cross interconnection box when the cross interconnection box is normal;
IC2Na reference ground current representing the C-phase split at the end of the cross-connect box when the cross-connect box is normal.
Preferably, the acquiring the fault location of the fault phase by the tester includes: and sending a ranging signal to the other end at the head end or the tail end of the cross interconnection box through the tester, and determining the fault position according to the ranging signal.
As another aspect of the present invention, a fault diagnosis system for a cross-connected box based on ground current includes:
the test grounding current acquisition module: obtaining test grounding currents of all split phases of ABC at the head end and the tail end of the current cross interconnection box;
a reference grounding current acquisition module: acquiring reference grounding currents of ABC split phases at the head end and the tail end of a cross interconnection box when the cross interconnection box is normal;
a fault phase determination module: and determining a fault phase according to the test grounding current and the reference grounding current.
Preferably, the determining the fault phase according to the test ground current and the reference ground current includes: judging whether a cross interconnection wiring error fault exists or not; and if the fault of the cross interconnection wiring does not exist, judging that the phase, of which the head end and the tail end are not equal and the comparison result with the reference grounding current exceeds a set threshold value, in the test grounding current is the fault phase.
Preferably, the determining the fault phase according to the test ground current and the reference ground current includes: acquiring the unbalance degree of each phase separation according to the test grounding current, and acquiring the ratio of the test grounding current and the load current of each phase separation according to the test grounding current; and when the ratio exceeds a preset ratio threshold and the unbalance exceeds a preset balance threshold, judging that a fault occurs.
Preferably, when it is determined that a fault occurs, the i-phase of the cross-connect box is determined to have a ground fault when it satisfies the following formula:
(Ii2＞Ii1∩Ii2＞Ii2N)∪(Ii1＞Ii2∩Ii1＞Ii1N)，i∈{A,B,C}
wherein,
IA1the test grounding current of the phase separation of the head end A of the current cross interconnection box is represented;
IB1the test grounding current of the current cross-connection box head end B split phase is represented;
IC1the test grounding current of the current cross-connection box head end C split phase is represented;
IA2indicates the currentTesting grounding current of a phase separation at the tail end A of the cross interconnection box;
IB2representing the test grounding current of the current cross-connection box tail end B split phase;
IC2representing the test grounding current of the current cross-connection box tail end C split phase;
IA1Nthe reference grounding current of the phase A is shown when the head end of the cross interconnection box is normal;
IB1Nb phase-splitting reference grounding current which represents the head end of the cross interconnection box when the cross interconnection box is normal;
IC1Nthe reference grounding current of the C phase splitting is expressed when the head end of the cross interconnection box is normal;
IA2Nthe reference grounding current of the phase A is shown when the cross interconnection box is normal at the tail end of the cross interconnection box;
IB2Nb phase-splitting reference grounding current which represents the tail end of the cross interconnection box when the cross interconnection box is normal;
IC2Na reference ground current representing the C-phase split at the end of the cross-connect box when the cross-connect box is normal.
Preferably, the acquiring the fault location of the fault phase by the tester includes: and sending a ranging signal to the other end at the head end or the tail end of the cross interconnection box through the tester, and determining the fault position according to the ranging signal.
The implementation of the invention can achieve the following beneficial technical effects: according to the invention, the fault phase can be judged according to the test grounding current only by acquiring the test grounding current of each phase division ABC at the head end and the tail end of the cross interconnection box, the cost is low, the influence of working conditions such as grounding resistance on the diagnosis accuracy can be effectively avoided, and the whole line is avoided.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a system connection diagram of the present invention;
FIG. 3 is a main section cross-connect cable simulation model;
FIG. 4 shows an equivalent circuit for calculating sheath induced current.
Detailed Description
To facilitate understanding of those skilled in the art, the present invention will be further described with reference to specific examples:
example 1:
the invention provides a fault diagnosis method for a cross-connection box based on grounding current, which comprises the following steps of:
step S1: obtaining test grounding currents of all split phases of ABC at the head end and the tail end of the current cross interconnection box;
step S2, acquiring reference grounding currents of ABC phases when the head end and the tail end of the cross interconnection box are normal;
step S3: and determining a fault phase according to the test grounding current and the reference grounding current.
According to the invention, the fault phase can be judged according to the test grounding current only by acquiring the test grounding current of each phase division ABC at the head end and the tail end of the cross interconnection box, so that the influence of working conditions such as grounding resistance on the diagnosis accuracy can be effectively avoided, and the whole line is avoided.
The principles of the present invention are further explained below:
for the high-voltage cable, the metal sheath adopts a continuous cross interconnection grounding mode, namely, the two sides of the cable joint connect the sheath to the ground through cross interconnection. When the single-core cable is laid in parallel in a horizontal straight line, the ABC-BC mode is assumedA cross-connect, a main section cross-connect cable simulation model is shown in FIG. 3. In fig. 3, thick solid lines indicate the core of the cable, and thin solid lines indicate the shielding layer and the ground line. The cross-connect cable shown in fig. 3 has 9 segments, and the first segment of A, B, C phases has Y equivalent admittances respectivelyA1，YB1，YC1(ii) a A. B, C middle phase, equivalent admittance is YA2、YB2、YC2(ii) a A. B, C phase end, equivalent admittance being YA3、YB3、YC3。IA1、IB1、IC1A, B, C three-phase ground line currents at the cable head end, respectively. I isA2、IB2、IC2The three phases of A, B and C are grounding wire currents at the tail end of the cable respectively.
In the operation process of the cable, the core wire and the metal shielding layer can be considered as a primary winding and a secondary winding of the transformer, the load current of the core wire generates an alternating magnetic field, a part of magnetic force lines are necessarily crosslinked with the metal shielding layer, and induced electromotive force is generated in the shielding layer and is related to the parameters of the cable, the current of the core wire and other factors. The equivalent circuit for sheath induced current calculation is shown in FIG. 4.
If the cable length is l, the loop voltage equation in FIG. 4 is expressed by the formula
In the formula 1, Es1、Es2、Es3Induction potentials of unit length on the three-phase metal sheath respectively; r1、R2Grounding resistors at two ends of a cable metal sheath; reRepresents a resistance to ground; r is the resistance of the cable metal sheath; x11、X22、X33Self-inductance resistance of a cable metal sheath; x12、X13、X21、X23、X31、X32Is the mutual inductance between the metal sheaths. In the present invention, 1 in the subscript represents a phase A; 2 represents a B phase, and 3 represents a C phase; such as X12Represents a phase A metalMutual inductance between the sheath and the B-phase metal sheath.
Let RA＝R+R1+R2+Re，RB＝R1+R2+ReIn 1 withs1r、Is2r、Is3rRepresenting the real part of sheath induced current, denoted by Is1f、Is2f、Is3fRepresenting the imaginary part of sheath induced current, in Us1r、Us2r、Us3rRepresenting the real part of the sheath voltage, in Us1f、Us2f、Us3fAnd expressing the imaginary part of the sheath voltage to obtain a matrix equation for calculating the induced current of the cable sheath.
The grounding current of the cable metal sheath consists of three parts
IGND＝Ig+Ic+Is(3)
Wherein: i isgIs leakage current; i iscIs a capacitive current; i issIs an induced current.
Wherein the capacitance current I of the cable per meter lengthc2 pi fUC, where U is the voltage to ground of the cable, f is the supply frequency, and C is the capacitance per meter length of cable.
According to the formulas (1) to (3), the magnitude of the sheath induced current is related to the parameters of the cable, the contact resistance R of the shielding layer and the ground, the operating voltage U and the like. Assuming that the cable operating voltage, the cable segment length, and so on remain the same, the capacitive current remains the same. Once the cable is damaged by external force and one or more points are grounded, the grounding current I on the metal sheath is monitoredGNDAnd the condition of cable faults can be found in time. If the cross interconnection wiring is wrong in construction or operation maintenance, larger grounding current can be generated in the metal sheath loop. By measuring the value of the earth current, cross-interconnections are first excludedA line error.
As a preferred embodiment of the above-described method for diagnosing a fault of a cross-connect box based on a ground current: the determining the fault phase according to the test ground current and the reference ground current comprises: judging whether a cross interconnection wiring error fault exists or not; and if the fault of the cross interconnection wiring does not exist, judging that the phase, of which the head end and the tail end are not equal and the comparison result with the reference grounding current exceeds a set threshold value, in the test grounding current is the fault phase. The set threshold may be a comparison threshold of dividing the test ground current by the reference ground current, and may be set as required, such as 1.2, 1, etc., where the set threshold may be a difference between the test ground current and the reference ground current, and the set threshold is a maximum value of the induced current magnitude change calculated according to equations (1) to (3) when the cable operating voltage is increased or decreased by 10% and the cable segment length is increased or decreased by 10%.
As a preferred embodiment of the above-described method for diagnosing a fault of a cross-connect box based on a ground current: the determining the fault phase according to the test ground current and the reference ground current comprises: acquiring the unbalance degree of each phase separation according to the test grounding current, and acquiring the ratio of the test grounding current and the load current of each phase separation according to the test grounding current; and when the ratio exceeds a preset ratio threshold and the unbalance exceeds a preset balance threshold, judging that a fault occurs. The ratio threshold and the balance threshold may be set as desired, such as the ratio threshold is set to 0.5 and the balance threshold is set to 1.
When different faults occur in the cross interconnection box, the grounding current of the fault phase at the head end and the tail end of the cross interconnection box changes obviously, and aiming at the electric insulation faults including various single-phase, two-phase grounding, disconnection or short-circuit faults, when the cable external insulation has the grounding fault, the grounding current value of a certain phase at the same measuring point is far larger than that of other two phases, and the phase splitting of the phase changes obviously, so that the phase external insulation with overlarge grounding current deviation can be judged to have the fault. When the cross interconnection box system is normal, the reference grounding current of the head and the tail ends is IA1N、IB1N、IC1N、IA2N、IB2N、IC2N(ii) a The test grounding current of the head and the tail end is IA1、IB1、IC1、IA2、IB2、IC2Calculating the degree of unbalance of each phase, i.e. IA1/IA2、IB1/IB2、IC1/IC2While using the ground current and load current I of each phaseLRatio of (I) to (b)A1/IL、IA2/IL、IB1/IL、IB2/IL、IC1/IL、IC2/ILIf a certain ratio exceeds 0.5 and changes significantly, and if the imbalance value exceeds 1 and changes significantly, the cable fails.
As a preferred embodiment of the above-described method for diagnosing a fault of a cross-connect box based on a ground current: when a fault is judged to occur, when the i-split phase of the cross-connection box meets the formula (4), the i-split phase is judged to have a ground fault:
(Ii2＞Ii1∩Ii2＞Ii2N)∪(Ii1＞Ii2∩Ii1＞Ii1N)，i∈{A,B,C} (4)
wherein,
IA1the test grounding current of the phase separation of the head end A of the current cross interconnection box is represented;
IB1the test grounding current of the current cross-connection box head end B split phase is represented;
IC1the test grounding current of the current cross-connection box head end C split phase is represented;
IA2representing the test grounding current of the current cross-connection box tail end A split phase;
IB2representing the test grounding current of the current cross-connection box tail end B split phase;
IC2indicating a current intersectionThe test grounding current of the phase C at the tail end of the interconnection box is split;
IA1Nthe reference grounding current of the phase A is shown when the head end of the cross interconnection box is normal;
IB1Nb phase-splitting reference grounding current which represents the head end of the cross interconnection box when the cross interconnection box is normal;
IC1Nthe reference grounding current of the C phase splitting is expressed when the head end of the cross interconnection box is normal;
IA2Nthe reference grounding current of the phase A is shown when the cross interconnection box is normal at the tail end of the cross interconnection box;
IB2Nb phase-splitting reference grounding current which represents the tail end of the cross interconnection box when the cross interconnection box is normal;
IC2Na reference ground current representing the C-phase split at the end of the cross-connect box when the cross-connect box is normal.
As a preferred embodiment of the above-described method for diagnosing a fault of a cross-connect box based on a ground current: the obtaining of the fault position of the fault phase by the tester comprises: and sending a ranging signal to the other end at the head end or the tail end of the cross interconnection box through the tester, and determining the fault position according to the ranging signal.
Example 2:
a fault diagnosis system for a cross-connect box based on ground current, as shown in fig. 2, comprising:
the test grounding current acquisition module: obtaining test grounding currents of all split phases of ABC at the head end and the tail end of the current cross interconnection box;
a reference grounding current acquisition module: acquiring reference grounding currents of ABC split phases at the head end and the tail end of a cross interconnection box when the cross interconnection box is normal;
a fault phase determination module: and determining a fault phase according to the test grounding current and the reference grounding current.
As a preferred embodiment of the above fault diagnosis system for a cross-connected box based on ground current: the determining the fault phase according to the test ground current and the reference ground current comprises: judging whether a cross interconnection wiring error fault exists or not; and if the fault of the cross interconnection wiring does not exist, judging that the phase, of which the head end and the tail end are not equal and the comparison result with the reference grounding current exceeds a set threshold value, in the test grounding current is the fault phase.
As a preferred embodiment of the above fault diagnosis system for a cross-connected box based on ground current: the determining the fault phase according to the test ground current and the reference ground current comprises: acquiring the unbalance degree of each phase separation according to the test grounding current, and acquiring the ratio of the test grounding current and the load current of each phase separation according to the test grounding current; and when the ratio exceeds a preset ratio threshold and the unbalance exceeds a preset balance threshold, judging that a fault occurs.
As a preferred embodiment of the above fault diagnosis system for a cross-connected box based on ground current: when a fault is judged to occur, when the i-split phase of the cross-connection box meets the formula (4), the i-split phase is judged to have a ground fault:
(Ii2＞Ii1∩Ii2＞Ii2N)∪(Ii1＞Ii2∩Ii1＞Ii1N)，i∈{A,B,C} (4)
wherein,
IA1the test grounding current of the phase separation of the head end A of the current cross interconnection box is represented;
IB1the test grounding current of the current cross-connection box head end B split phase is represented;
IC1the test grounding current of the current cross-connection box head end C split phase is represented;
IA2represents the current transactionThe tail end A of the fork interconnection box is split-phase and is used for testing grounding current;
IB2representing the test grounding current of the current cross-connection box tail end B split phase;
IC2representing the test grounding current of the current cross-connection box tail end C split phase;
IA1Nthe reference grounding current of the phase A is shown when the head end of the cross interconnection box is normal;
IB1Nb phase-splitting reference grounding current which represents the head end of the cross interconnection box when the cross interconnection box is normal;
IC1Nthe reference grounding current of the C phase splitting is expressed when the head end of the cross interconnection box is normal;
IA2Nthe reference grounding current of the phase A is shown when the cross interconnection box is normal at the tail end of the cross interconnection box;
IB2Nb phase-splitting reference grounding current which represents the tail end of the cross interconnection box when the cross interconnection box is normal;
IC2Na reference ground current representing the C-phase split at the end of the cross-connect box when the cross-connect box is normal.
As a preferred embodiment of the above fault diagnosis system for a cross-connected box based on ground current: the obtaining of the fault position of the fault phase by the tester comprises: and sending a ranging signal to the other end at the head end or the tail end of the cross interconnection box through the tester, and determining the fault position according to the ranging signal.
The above description is only an embodiment of the present invention, but the technical features of the present invention are not limited thereto, and any changes or modifications within the technical field of the present invention by those skilled in the art are covered by the claims of the present invention.

Claims (10)

1. A fault diagnosis method for a cross-connection box based on ground current is characterized by comprising the following steps:
obtaining test grounding currents of all split phases of ABC at the head end and the tail end of the current cross interconnection box;
acquiring reference grounding currents of ABC split phases at the head end and the tail end of a cross interconnection box when the cross interconnection box is normal;
and determining a fault phase according to the test grounding current and the reference grounding current.
2. The ground current based cross-connect box fault diagnosis method of claim 1, wherein said determining a fault phase from test ground current and reference ground current comprises: judging whether a cross interconnection wiring error fault exists or not; and if the fault of the cross interconnection wiring does not exist, judging that the phase, of which the head end and the tail end are not equal and the comparison result with the reference grounding current exceeds a set threshold value, in the test grounding current is the fault phase.
3. The ground current based cross-connect box fault diagnosis method of claim 1, wherein said determining a fault phase from test ground current and reference ground current comprises: acquiring the unbalance degree of each phase separation according to the test grounding current, and acquiring the ratio of the test grounding current and the load current of each phase separation according to the test grounding current; and when the ratio exceeds a preset ratio threshold and the unbalance exceeds a preset balance threshold, judging that a fault occurs.
4. The fault diagnosis method of the cross-connection box based on the ground current as claimed in claim 3, wherein when the fault is determined to occur, when the i-phase of the cross-connection box satisfies the following formula, the i-phase is determined to have the ground fault:
(Ii2＞Ii1∩Ii2＞Ii2N)∪(Ii1＞Ii2∩Ii1＞Ii1N)，i∈{A,B,C}
wherein,
IA1the test grounding current of the phase separation of the head end A of the current cross interconnection box is represented;
IB1the test grounding current of the current cross-connection box head end B split phase is represented;
IC1the test grounding current of the current cross-connection box head end C split phase is represented;
IA2representing the test grounding current of the current cross-connection box tail end A split phase;
IB2test for representing current cross-interconnect box terminal B-split phaseGrounding current;
IC2representing the test grounding current of the current cross-connection box tail end C split phase;
IA1Nthe reference grounding current of the phase A is shown when the head end of the cross interconnection box is normal;
IB1Nb phase-splitting reference grounding current which represents the head end of the cross interconnection box when the cross interconnection box is normal;
IC1Nthe reference grounding current of the C phase splitting is expressed when the head end of the cross interconnection box is normal;
IA2Nthe reference grounding current of the phase A is shown when the cross interconnection box is normal at the tail end of the cross interconnection box;
IB2Nb phase-splitting reference grounding current which represents the tail end of the cross interconnection box when the cross interconnection box is normal;
IC2Na reference ground current representing the C-phase split at the end of the cross-connect box when the cross-connect box is normal.
5. The method for fault diagnosis of cross-connect box based on ground current as claimed in claim 1, wherein said obtaining fault location of fault phase by tester comprises: and sending a ranging signal to the other end at the head end or the tail end of the cross interconnection box through the tester, and determining the fault position according to the ranging signal.
6. A cross-connection box fault diagnosis system based on ground current is characterized by comprising:
the test grounding current acquisition module: obtaining test grounding currents of all split phases of ABC at the head end and the tail end of the current cross interconnection box;
a reference grounding current acquisition module: acquiring reference grounding currents of ABC split phases at the head end and the tail end of a cross interconnection box when the cross interconnection box is normal;
a fault phase determination module: and determining a fault phase according to the test grounding current and the reference grounding current.
7. The ground current based cross-connect box fault diagnosis system of claim 6, wherein said determining a fault phase from the test ground current and the reference ground current comprises: judging whether a cross interconnection wiring error fault exists or not; and if the fault of the cross interconnection wiring does not exist, judging that the phase, of which the head end and the tail end are not equal and the comparison result with the reference grounding current exceeds a set threshold value, in the test grounding current is the fault phase.
8. The ground current based cross-connect box fault diagnosis system of claim 6, wherein said determining a fault phase from the test ground current and the reference ground current comprises: acquiring the unbalance degree of each phase separation according to the test grounding current, and acquiring the ratio of the test grounding current and the load current of each phase separation according to the test grounding current; and when the ratio exceeds a preset ratio threshold and the unbalance exceeds a preset balance threshold, judging that a fault occurs.
9. The ground current-based cross-connect box fault diagnosis system of claim 8, wherein when a fault is determined to occur, when an i-phase of the cross-connect box satisfies the following formula, the i-phase is determined to have a ground fault:
(Ii2＞Ii1∩Ii2＞Ii2N)∪(Ii1＞Ii2∩Ii1＞Ii1N)，i∈{A,B,C}
wherein,
IA1the test grounding current of the phase separation of the head end A of the current cross interconnection box is represented;
IB1the test grounding current of the current cross-connection box head end B split phase is represented;
IC1the test grounding current of the current cross-connection box head end C split phase is represented;
IA2representing the test grounding current of the current cross-connection box tail end A split phase;
IB2representing the test grounding current of the current cross-connection box tail end B split phase;
IC2representing the test grounding current of the current cross-connection box tail end C split phase;
IA1Nthe reference grounding current of the phase A is shown when the head end of the cross interconnection box is normal;
IB1Nb phase-splitting reference grounding current which represents the head end of the cross interconnection box when the cross interconnection box is normal;
IC1Nthe reference grounding current of the C phase splitting is expressed when the head end of the cross interconnection box is normal;
IA2Nthe reference grounding current of the phase A is shown when the cross interconnection box is normal at the tail end of the cross interconnection box;
IB2Nb phase-splitting reference grounding current which represents the tail end of the cross interconnection box when the cross interconnection box is normal;
IC2Na reference ground current representing the C-phase split at the end of the cross-connect box when the cross-connect box is normal.
10. The system of claim 6, wherein the obtaining of the fault location of the fault phase by the tester comprises: and sending a ranging signal to the other end at the head end or the tail end of the cross interconnection box through the tester, and determining the fault position according to the ranging signal.
CN201711194012.2A 2017-11-24 2017-11-24 A kind of cross interconnected box fault diagnosis method and system based on earth current Pending CN108152662A (en)

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