CN115453417A - High-voltage cable fault testing method - Google Patents
High-voltage cable fault testing method Download PDFInfo
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Abstract
The invention discloses a fault testing method for a high-voltage cable. The method is applied to a high-voltage cable fault test platform, and the platform comprises a wire core of a three-phase single-core cable, a first direct grounding box, a second direct grounding box and two cross interconnection grounding boxes; each single-core cable core comprises three equal cable metal protective layers; a wire core middle joint is arranged between the cable metal protective layers; the cable metal protective layers at different sections form three cable metal protective layer loops through two cross-connected grounding boxes; the first direct grounding box comprises at least three first alternating current transformers; the second direct grounding box comprises at least three second alternating current transformers; the method comprises the following steps: acquiring each first actual sheath grounding current on each cable metal sheath loop acquired by each first alternating current transformer and each second actual sheath grounding current of each cable metal sheath loop acquired by each second alternating current transformer; and determining the fault of the high-voltage cable according to the grounding current of each first actual sheath and the grounding current of each second actual sheath.
Description
Technical Field
The embodiment of the invention relates to the field of high-voltage transmission detection, in particular to a high-voltage cable fault testing method.
Background
With the increasing development speed of the power transmission and distribution grid year by year, the high-voltage cable has larger and larger operation scale in a power transmission system due to the advantages of meeting the transmission requirement of high-capacity electric energy, protecting urban appearances from being damaged and the like. Therefore, the running state of the cable can be known in time, and the normal running of the high-voltage cable is guaranteed, so that the safety and the stability of a power system are guaranteed.
The high-voltage cable generally refers to a single-core cable operating at a voltage level of 110kV or above, a circle of metal sheath is arranged on the outer layer of the main insulation of the high-voltage cable and serves as a shielding layer, when current flows through a cable core, due to the electromagnetic induction principle, induction voltage appears at two ends of the metal sheath, and the induction voltage at any point on the metal sheath is not larger than 50V. In engineering, the influence of the internal field intensity of the cable on the outside is usually isolated by adopting a metal sheath grounding mode, so that the aim of limiting the induced voltage of the metal sheath is fulfilled. For a power transmission system of a long-distance high-voltage cable with the length of more than 1500m, a cross-connection grounding mode is generally adopted. Statistical data shows that the most prone to faults in the high-voltage cable cross-connection grounding system are the connecting parts of intermediate joints, connecting boxes, terminals and the like of cables, at present, in the prior art, classification and positioning of different faults are achieved by monitoring the change of the current amplitude of coaxial cables of the cross-connection boxes, but the current at the coaxial cables is formed by overlapping currents of different sheath loops, and the current amplitude change is only relied on, so that the specific position where the same sheath loop breaks down is not enough to be positioned.
Or, in the prior art, the amplitude of the grounding current at the first end and the tail end of the metal sheath of the cable and the amplitude of the current of the coaxial cable of the cross interconnection box are directly measured, and ratio analysis and unbalance analysis are performed on the three-phase current of the grounding wire under the fault and normal conditions to identify the fault, but the method has excessive measured current number, needs more sensors, generally relates to a large amount of characteristic quantities or complex fault criteria to identify the fault of the cable, often influences the rapidity of cable fault identification, and is not beneficial to engineering application.
Disclosure of Invention
The invention provides a high-voltage cable fault testing method, which is used for realizing rapid identification of high-voltage cable faults and providing a new method for online monitoring of high-voltage cable line faults.
The embodiment of the invention provides a high-voltage cable fault testing method which is applied to a high-voltage cable fault testing platform, wherein the high-voltage cable fault testing platform comprises a wire core of a three-phase single-core cable, a first direct grounding box, a second direct grounding box and two cross interconnection grounding boxes; each wire core of the single-core cable comprises three equal sections of cable metal protective layers; a wire core intermediate joint is arranged between each two cable metal protective layers; the cable metal sheath loops of different sections form three cable metal sheath loops through the two cross-connected grounding boxes; the first direct grounding box comprises at least three first alternating current transformers; the second direct grounding box comprises at least three second alternating current transformers;
the high-voltage cable fault testing method comprises the following steps:
acquiring each first actual sheath grounding current on each cable metal sheath loop acquired by each first alternating current transformer and each second actual sheath grounding current of each cable metal sheath loop acquired by each second alternating current transformer;
and determining the fault of the high-voltage cable according to the grounding current of each first actual sheath and the grounding current of each second actual sheath.
Optionally, determining a fault of the high-voltage cable according to each of the first actual sheath ground currents and each of the second actual sheath ground currents includes: determining the fault classification of the high-voltage cable according to the first actual sheath grounding current and the second actual sheath grounding current:
determining a high-voltage cable fault classification according to each of the first actual sheath ground currents and each of the second actual sheath ground currents, comprising:
determining phase difference absolute values of the first actual sheath grounding currents and the second actual sheath grounding currents on different cable sheath loops;
determining phase ratio and amplitude ratio of each first actual sheath grounding current and each second actual sheath grounding current on the same cable sheath loop;
and determining the fault classification of the high-voltage cable according to the absolute value of the phase difference, the phase ratio and the amplitude ratio.
Optionally, the method further includes: obtaining the wire core line voltage of each phase of the single-core cable, the wire core length of each phase of the single-core cable and the wire core capacitance parameters of each phase of the single-core cable;
determining sheath leakage current on each cable metal sheath loop according to the wire core line voltage, the wire core length and the wire core capacitance parameters;
obtaining core line currents of each phase of the single-core cable and mutual inductance parameters of the core lines of each phase of the single-core cable to each cable metal protective layer;
determining a sheath ring current on each cable metal sheath loop according to the wire core current and the mutual inductance parameter;
and determining theoretical sheath grounding current on each cable metal sheath loop according to the sheath leakage current and the sheath ring current.
Optionally, determining a fault of the high-voltage cable according to each of the first actual sheath ground currents and each of the second actual sheath ground currents, further includes: and determining whether the high-voltage cable has a fault according to the first actual sheath grounding current, the second actual sheath grounding current and the theoretical sheath grounding current on each cable sheath loop.
Optionally, determining whether the high-voltage cable fails according to the first actual sheath ground currents, the second actual sheath ground currents and the theoretical sheath ground currents on the sheath loops includes:
and when the first actual sheath grounding current or the second actual sheath grounding current on each cable sheath loop is different from the theoretical sheath grounding current, determining that the high-voltage cable has a fault.
Optionally, the sheath leakage current on each cable metal sheath loop is determined according to the wire core line voltage, the wire core length and the wire core capacitance parameters, specifically:
I A1 ＝jwU A L A1 C A
wherein: u shape A The voltage vector of a core of the A-phase single-core cable is obtained; l A1 The length of the cable metal sheath A1; c A The core capacitance of the A-phase single-core cable is obtained; because the lengths of the cable metal protective layer A2 and the cable metal protective layer A3 are the same as the length of the cable metal protective layer A1, the sheath leakage currents of the cable metal protective layer A2 and the cable metal protective layer A3 are the same as the sheath leakage current of the cable metal protective layer A1;
I B1 ＝jwU B L B1 C B
wherein, U B The core voltage vector of the B-phase single-core cable is obtained; l B1 The length of the cable metal sheath B1; c B The core capacitance of the B-phase single-core cable is obtained; because the lengths of the cable metal protective layer B2 and the cable metal protective layer B3 are the same as the length of the cable metal protective layer B1, the sheath leakage currents of the cable metal protective layer B2 and the cable metal protective layer B3 are the same as the sheath leakage current of the cable metal protective layer B1;
I C1 ＝jwU C L C1 C C
wherein, U C The core voltage vector of the C-phase single-core cable is obtained; l C1 The length of the cable metal sheath C1; c C The core capacitance is the core capacitance of the C-phase single-core cable; because the lengths of the cable metal sheath C2 and the cable metal sheath C3 are the same as the length of the cable metal sheath C1, the sheath leakage currents of the cable metal sheath C2 and the cable metal sheath C3 are the same as the sheath leakage current of the cable metal sheath C1.
Optionally, the core capacitance parameters specifically include:
wherein epsilon r Is a relative dielectric constant, D C The diameter of a single-core cable core; δ is the thickness of the insulator.
Optionally, determining a sheath ring current on each of the cable metal sheath loops according to the core current and the mutual inductance parameter; the method specifically comprises the following steps:
wherein, U SCn (n =1,2,3) is the induced voltage of each section of cable metal sheath; z mAn 、Z mBn And Z mCn (n =1,2,3) is the equivalent impedance of each section of cable metal sheath; re and Rg are grounding resistors at two ends of the cross interconnection main section; i is m1 、I m2 And I m3 Sheath circulating currents flowing through the cable metal sheath loops A1-B2-C3, B1-C2-A3 and C1-A2-B3 respectively;
taking the induced voltage of the metal sheath of the A1 cable as an example; u shape SA1 ＝-jw(I A L AA +I B M AB +I C M AC )l A1 (ii) a The induced voltage of A1 cable metal sheath includes A looks single-phase cable to A1 section metal sheath induced voltage plus B looks and C looks single-core cable to the mutual voltage that produces of A1 section cable metal sheath, in the formula: i is A 、I B 、I C Core currents of the cable A, the cable B and the cable C are respectively indicated; LAA is A phase single core cable to cable metalMutual inductance coefficient of the protective layer A1; MAB and MAC are mutual inductance coefficients of the B-phase single-core cable and the C-phase single-core cable to the A1 cable metal sheath respectively; the method for calculating the induced voltage of the small sections of the other metal protective layers is similar to the induced voltage of the metal protective layer of the A1 cable.
Optionally, determining a theoretical sheath ground current on each of the cable metal sheath loops according to the sheath leakage current and the sheath loop current includes:
and the theoretical sheath grounding current on each cable metal sheath loop is the vector sum of the sheath leakage current and the sheath ring current.
Optionally, determining a theoretical sheath ground current on each of the cable metal sheath loops according to the sheath leakage current and the sheath loop current, specifically:
I 1a ＝(I LA1 +I LB2 +I LC3 )-(I LR1 +I RB2 +I RC3 )-I m1
I 1b ＝(I LB1 +I LC2 +I LA3 )-(I RB1 +I RC2 +I RA3 )-I m2
I 1c ＝(I LC1 +I LA2 +I LB3 )-(I RC1 +I RA2 +I RB3 )-I m3
I 2a ＝(I RB1 +I RC2 +I RA3 )-(I LB1 +I LC2 +I LA3 )+I m2
I 2b ＝(I RC1 +I RA2 +I RB3 )-(I LC1 +I LA2 +I LB3 )+I m3
I 1a ＝(I RA1 +I RB2 +I RC3 )-(I LA1 +I LB2 +I LC3 )+I m1
wherein: i is 1a And I 2c The theoretical sheath grounding current on the cable metal sheath loop A1-B2-C3 is reflected together; I.C. A 1b And I 2a The theoretical sheath grounding current on the cable metal sheath loop B1-C2-A3 is reflected together; i is 1c And I 2b Collectively reflect the cable metalTheoretical sheath grounding current on the sheath loop C1-A2-B3; i is m1 、I m2 And I m3 Sheath circulating currents flowing through the cable metal sheath loops A1-B2-C3, B1-C2-A3 and C1-A2-B3 respectively; i is LAn 、I LBn 、I LCn The current component which flows to the left correspondingly on each section of the cable metal sheath is the leakage current; i is RAn 、I RBn And I RCn The component of the leakage current which flows to the right correspondingly on each section of the cable metal sheath; here, the component flowing to the right on the A1 cable metal sheath is taken as an example;
wherein ZmLA1 and ZmRA1 are equivalent impedances of the left side and the right side of the A1 cable metal sheath respectively; zmLA1 forms Z with ZmRA1 mA1 I.e. the overall impedance of the A1 cable metal sheath; the corresponding right-going flow component on the other lengths of cable jacket is similar.
In the embodiment of the invention, based on a high-voltage cable fault test platform, each first actual sheath grounding current on each cable metal sheath loop acquired by each first alternating current transformer and each second actual sheath grounding current of each cable metal sheath loop acquired by each second alternating current transformer are acquired; and determining the high-voltage cable fault according to each first actual sheath grounding current and each second actual sheath grounding current, thereby realizing the rapid identification of the high-voltage cable fault and providing a new method for the online monitoring of the high-voltage cable line fault.
Drawings
Fig. 1 is a flowchart of a fault testing method for a high-voltage cable according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a high-voltage cable fault testing platform according to an embodiment of the present invention;
FIG. 3 is a flow chart of another method for testing faults of a high voltage cable according to an embodiment of the present invention;
fig. 4 is a flowchart of another method for testing a fault of a high-voltage cable according to an embodiment of the present invention;
FIG. 5 is an equivalent circuit diagram for testing the fault of the high-voltage cable provided by the embodiment of the invention;
fig. 6 is a schematic diagram of the sheath leakage current flowing direction of the section A1 of the cable metal sheath provided by the embodiment of the invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Fig. 1 is a flowchart of a fault testing method for a high-voltage cable according to an embodiment of the present invention; as shown in fig. 1, the method specifically includes the following steps:
s110, acquiring each first actual sheath grounding current on each cable metal sheath loop acquired by each first alternating current transformer and each second actual sheath grounding current of each cable metal sheath loop acquired by each second alternating current transformer.
The high-voltage cable fault testing method is applied to a high-voltage cable fault testing platform, and fig. 2 is a schematic structural diagram of the high-voltage cable fault testing platform provided by the embodiment of the invention; as shown in fig. 2, the high-voltage cable fault testing platform comprises cores (a phase, B phase and C phase) of a three-phase single-core cable, a first direct grounding box G1, a second direct grounding box G2 and two cross-interconnected grounding boxes J1 and J2; each single-core cable core (A phase, B phase and C phase) comprises three equal cable metal protective layers (A1, A2, A3, B1, B2, B3, C1, C2 and C3); wire core intermediate joints (JA 1, JA2, JB1, JC1 and JC 2) and terminal joints of JA0, JB0, JC0, JA3, JB3 and JC3 are arranged among the cable metal protective layers; the cable metal protective layers of different sections form three cable metals through two cross-connected grounding boxes J1 and J1Belongs to a protective layer loop A1-B2-C3; B1-C2-A3C1-A2-B3; the first direct grounding box G1 comprises at least three first alternating current transformers; the second direct grounding box G2 comprises at least three second alternating current transformers; in this embodiment, the first actual sheath grounding current I on each cable metal sheath loop collected by each first ac transformer is obtained 1a I 1b I 1c And each second actual sheath grounding current I of each cable metal sheath loop collected by each second AC transformer 2a I 2b I 2c (ii) a Wherein, I 1a And I 2c The operation conditions on the cable metal sheath loop A1-B2-C3 can be reflected together; i is 1b And I 2a The operation conditions on the cable metal sheath loop B1-C2-A3 can be reflected together; i is 1c And I 2b Can reflect the operation condition of the cable metal sheath loop C1-A2-B3 together.
And S120, determining the fault of the high-voltage cable according to the grounding current of each first actual sheath and the grounding current of each second actual sheath.
In this embodiment, the grounding current I is passed through each first actual passivation layer 1a I 1b I 1c And each second actual passivation layer grounding current I 2a I 2b I 2c It can be determined that the high voltage cable is faulty, it can be understood that if I is detected 1a And I 2c Is not the same, or when I 1a And I 2c Respectively connected with theoretical sheath grounding current I 1a’ And I 2c’ When the two circuits are different, the occurrence of faults on the cable metal sheath loop A1-B2-C3 is reflected; if when I 1b And I 2a Is not the same, or when I 1b And I 2a Respectively connected with theoretical sheath grounding current I 1b’ And I 2a’ When the two circuits are different, faults occur on the cable metal protective layer loop B1-C2-A3; if when I 1c And I 2b Is not the same, or when I 1c And I 2b Respectively connected with theoretical sheath grounding current I 1c’ And I 2b’ When the two circuits are different, faults occur on the cable metal protective layer loop C1-A2-B3; further, through each first actual sheath grounding current I 1a I 1b I 1c And each second actual passivation layer grounding current I 2a I 2b I 2c Different fault types of the high voltage cable may be determined, exemplary fault classifications include: the wire core intermediate joints (JA 1, JA2, JB1, JC1 and JC 2) and terminal joints (JA 0, JB0, JC0, JA3, JB3 and JC 3) are in short circuit or open circuit, or the cross-connection grounding box is in water inlet short circuit and the like, so that the grounding current I of each first actual protective layer passes through 1a I 1b I 1c And each second actual passivation layer grounding current I 2a I 2b I 2c The method and the device realize rapid identification of the high-voltage cable faults, provide a new method for online monitoring of the high-voltage cable line faults, and solve the problems that in the prior art, the cable faults are identified through complex fault criteria, which often influences the rapidity of cable fault identification and the like.
Optionally, on the basis of the foregoing embodiment, further refining the determination of the high-voltage cable fault, fig. 3 is a flowchart of another high-voltage cable fault testing method provided in the embodiment of the present invention, and as shown in fig. 3, the method includes:
s210, acquiring each first actual sheath grounding current on each cable metal sheath loop acquired by each first alternating current transformer and each second actual sheath grounding current of each cable metal sheath loop acquired by each second alternating current transformer.
S220, determining the absolute value of the phase difference between each first actual sheath grounding current and each second actual sheath grounding current on different cable sheath loops.
Wherein each first actual passivation layer grounding current I 1a I 1b I 1c And each second actual passivation layer grounding current I 2a I 2b I 2c In terms of amplitude and phase, can be expressed as: I.C. A 1a ＝x1∠y1；I 1b ＝x2∠y2；I 1c ＝x3∠y3；I 2c ＝x4∠y4；I 2a ＝x5∠y5；I 2b = x6 = y6; due to I 1a And I 2c The operation conditions on the cable metal sheath loop A1-B2-C3 can be reflected together; I.C. A 1b And I 2a The operation conditions on the cable metal sheath loop B1-C2-A3 can be reflected together; i is 1c And I 2b Can reflect the movement of the cable metal sheath loop C1-A2-B3 togetherDetermining the phase difference on the cable metal sheath loops A1-B2-C3 and B1-C2-A3 as t1= | y1-y2|; determining the phase difference between the cable metal sheath loops B1-C2-A3 and C1-A2-B3 as t2= | y2-y3|; and determining the phase difference on the cable metal sheath loops A1-B2-C3 and C1-A2-B3 as t3= | y1-y3|.
S230, determining the phase ratio and amplitude ratio of each first actual sheath grounding current and each second actual sheath grounding current on the same cable sheath loop.
Wherein, the amplitude ratio A1 and the phase ratio B1 on the same cable metal sheath return circuit A1-B2-C3 are:
the amplitude ratio a2 and the phase ratio B2 on the same metal cable sheath loop B1-C2-A3 are as follows:
the amplitude ratio A3 and the phase ratio B3 on the same metal cable sheath loop B1-C2-A3 are as follows:
s240, determining fault classification of the high-voltage cables according to the absolute value of the phase difference, the phase ratio and the amplitude ratio.
As shown in table 1 below, table 1 shows that different high-voltage cable fault classifications are determined according to the phase difference absolute value, the phase ratio and the amplitude ratio;
table 1: a fault classification table:
on the basis of the above embodiments, the present embodiment further determines different high-voltage cable fault classifications according to the phase difference absolute value, the phase ratio and the amplitude ratio, and realizes accurate fault type positioning on the basis of realizing rapid fault identification.
Optionally, on the basis of the foregoing embodiment, further details are provided, and fig. 4 is a flowchart of another high-voltage cable fault testing method provided in the embodiment of the present invention, as shown in fig. 4, the method includes the following steps:
s310, obtain each first actual sheath ground current on each cable metal sheath loop collected by each first ac transformer and each second actual sheath ground current on each cable metal sheath loop collected by each second ac transformer.
S320, obtaining the wire core line voltage of each phase of single-core cable, the wire core length of each phase of single-core cable and the wire core capacitance parameters of each phase of single-core cable.
S330, determining the sheath leakage current on each cable metal sheath loop according to the wire core line voltage, the wire core length and the wire core capacitance parameters.
Specifically, fig. 5 is an equivalent circuit diagram of a fault test of a high-voltage cable according to an embodiment of the present invention; as shown in fig. 5, the equivalent circuit diagram for fault testing includes three metal sheath loops after cross-interconnection: A1-B2-C3, B1-C2-A3 and C1-A2-B3; FIG. 6 is a schematic diagram illustrating the sheath leakage current flowing direction of a section A1 of the metal sheath of the cable provided by the embodiment of the present invention; as shown in FIGS. 5 and 6, sheath leakage current I of the A1 section of the cable metal sheath A1 Comprises the following steps:
I A1 ＝jwU A L A1 C A
wherein: u shape A The voltage vector of a core of the A-phase single-core cable is obtained; l A1 The length of the cable metal sheath A1; c A The core capacitance of the A-phase single-core cable is obtained; leakage current I of the protective layer flowing through the insulation impedance Zi A1 Will flow left and right on the cable metal sheath A1 with a component of I LA1 And I RA1 (ii) a Satisfy I A1 ＝I LA1 +I RA1 (ii) a ZmLA1 and ZmRA1 are equivalent impedances of the left and right sides of the cable metal sheath A1, respectively, and the sum of ZmLA1 and ZmRA1 is the overall impedance of the cable metal sheath A1.
Because the lengths of the cable metal sheath A2 and the cable metal sheath A3 are the same as the length of the cable metal sheath A1, the sheath leakage currents of the cable metal sheath A2 and the cable metal sheath A3 are the same as the sheath leakage current of the cable metal sheath A1.
Similarly, the leakage current flow direction of the metal sheath sections of other cables is similar to that of the sheath A1; sheath leakage current I of cable metal sheath B1 section B1 Is composed of
I B1 ＝jwU B L B1 C B
Wherein, U B The core voltage vector of the B-phase single-core cable is obtained; l B1 The length of the cable metal sheath B1; c B The core capacitance of the B-phase single-core cable is obtained; because the lengths of the cable metal protective layer B2 and the cable metal protective layer B3 are the same as the length of the cable metal protective layer B1, the sheath leakage currents of the cable metal protective layer B2 and the cable metal protective layer B3 are the same as the sheath leakage current of the cable metal protective layer B1;
similarly, the sheath leakage current I of the C1 section of the cable metal sheath C1 Comprises the following steps:
I C1 ＝jwU C L C1 C C
wherein, U C The core voltage vector of the C-phase single-core cable is obtained; l C1 The length of the cable metal sheath C1; c C The core capacitance is the core capacitance of the C-phase single-core cable; because the lengths of the cable metal sheath C2 and the cable metal sheath C3 are the same as the length of the cable metal sheath C1, the sheath leakage currents of the cable metal sheath C2 and the cable metal sheath C3 are the same as the sheath leakage current of the cable metal sheath C1.
Optionally, the core capacitance parameters specifically include:
wherein epsilon r Is a relative dielectric constant, D C The diameter of a single-core cable core; δ is the thickness of the insulating layer. It should be noted that each single core cable further includes an insulating layer between the core of the single core cable and the metal sheath of the cable (fig. 6 also illustrates the complete structure on the a-phase single core cable).
And S340, obtaining the wire core current of each phase of single-core cable and the mutual inductance parameter of the wire core of each phase of single-core cable to the metal sheath of each cable.
And S350, determining the sheath ring current on each cable metal sheath loop according to the core wire current and the mutual inductance parameter.
The sheath ring current is generated in the metal sheath by the induced voltage of each sheath through the electromagnetic induction principle; with continued reference to FIG. 5;
sheath loop current on each cable metal sheath loop; the method comprises the following specific steps:
wherein, U SCn (n =1,2,3) is the induced voltage of each section of cable metal sheath; z mAn 、Z mBn And Z mCn (n =1,2,3) is the equivalent impedance of each section of cable metal sheath; re and Rg are grounding resistors at two ends of the cross interconnection main section; i is m1 、I m2 And I m3 Sheath circulating currents flowing through the cable metal sheath loops A1-B2-C3, B1-C2-A3 and C1-A2-B3 respectively;
taking the induced voltage of the metal sheath of the A1 cable as an example; u shape SA1 ＝-jw(I A L AA +I B M AB +I C M AC )l A1 (ii) a The induced voltage of A1 cable metal sheath includes A looks single-phase cable to A1 section metal sheath induced voltage plus B looks and C looks single-core cable to the mutual voltage that produces of A1 section cable metal sheath, in the formula: i is A 、I B 、I C The core currents of the cable A, the cable B and the cable C are respectively; LAA is the mutual inductance coefficient of the A-phase single-core cable to the cable metal sheath A1; MAB and MAC are mutual inductance coefficients of the B-phase single-core cable and the C-phase single-core cable to the A1 cable metal sheath respectively; method for calculating induced voltage of other metal protective layer small segment and A1 circuitThe induced voltage of the cable metal sheath is similar.
S360, theoretical sheath grounding current on each cable metal sheath loop is determined according to the sheath leakage current and the sheath ring current.
Wherein, the theoretical protective layer grounding current is the current flowing through the metal protective layer loop; the theoretical sheath grounding current on each cable metal sheath loop is the vector sum of the sheath leakage current and the sheath ring current, and flows into the ground through the two-end direct grounding box. Specifically, the method comprises the following steps:
I 1a ＝(I LA1 +I LB2 +I LC3 )-(I LR1 +I RB2 +I RC3 )-I m1
I 1b ＝(I LB1 +I LC2 +I LA3 )-(I RB1 +I RC2 +I RA3 )-I m2
I 1c ＝(I LC1 +I LA2 +I LB3 )-(I RC1 +I RA2 +I RB3 )-I m3
I 2a ＝(I RB1 +I RC2 +I RA3 )-(I LB1 +I LC2 +I LA3 )+I m2
I 2b ＝(I RC1 +I RA2 +I RB3 )-(I LC1 +I LA2 +I LB3 )+I m3
I 1a ＝(I RA1 +I RB2 +I RC3 )-(I LA1 +I LB2 +I LC3 )+I m1
wherein: i is 1a And I 2c The theoretical sheath grounding current on the cable metal sheath loop A1-B2-C3 is reflected together; i is 1b And I 2a The theoretical sheath grounding current on the cable metal sheath loop B1-C2-A3 is reflected together; i is 1c And I 2b The theoretical sheath grounding current on the cable metal sheath loop C1-A2-B3 is reflected together; i is m1 、I m2 And I m3 Sheath circulating currents flowing through the cable metal sheath loops A1-B2-C3, B1-C2-A3 and C1-A2-B3 respectively; I.C. A LAn 、I LBn 、I LCn For leakage current in each section of cableThe current component which flows leftwards correspondingly on the protective layer; i is RAn 、I RBn And I RCn The component of the leakage current which flows to the right correspondingly on each section of the cable metal sheath; here, the component flowing to the right on the cable metal sheath A1 is taken as an example;
wherein ZmLA1 and ZmRA1 are equivalent impedances of the left side and the right side of the A1 cable metal sheath respectively; zmLA1 forms Z with ZmRA1 mA1， The impedance is the integral impedance of the A1 cable metal sheath; the corresponding right-going flow component on the other lengths of cable jacket is similar. Thus, the theoretical sheath grounding current I is determined by each parameter in the embodiment 1a’ I 1b’ I 1c’ I 2a’ I 2b’ I 2c’ 。
And S370, determining whether the high-voltage cable has faults according to the first actual sheath grounding current, the second actual sheath grounding current and the theoretical sheath grounding current on each cable sheath loop.
When the first actual sheath grounding current or the second actual sheath grounding current on each cable sheath loop is different from the theoretical sheath grounding current in one-to-one correspondence, the high-voltage cable can be determined to have a fault.
In this embodiment, based on the theoretical sheath ground currents determined by the parameters, when the first actual sheath ground currents and the second actual sheath ground currents on the sheath loops are different from the theoretical sheath ground currents corresponding to one another, it is determined that the high-voltage cable has a fault, and a new testing method is provided for realizing the high-voltage cable fault.
Claims (10)
1. A high-voltage cable fault testing method is characterized by being applied to a high-voltage cable fault testing platform, wherein the high-voltage cable fault testing platform comprises a wire core of a three-phase single-core cable, a first direct grounding box, a second direct grounding box and two cross-interconnected grounding boxes; each single-core cable core comprises three equal cable metal protective layers; a wire core middle joint is arranged between the cable metal protective layers; the cable metal sheath loops of different sections form three cable metal sheath loops through the two cross-connected grounding boxes; the first direct grounding box comprises at least three first alternating current transformers; the second direct grounding box comprises at least three second alternating current transformers;
the high-voltage cable fault testing method comprises the following steps:
acquiring each first actual sheath grounding current on each cable metal sheath loop acquired by each first alternating current transformer and each second actual sheath grounding current of each cable metal sheath loop acquired by each second alternating current transformer;
and determining the fault of the high-voltage cable according to the grounding current of each first actual sheath and the grounding current of each second actual sheath.
2. The method of claim 1, wherein determining a high voltage cable fault based on each of the first actual sheath ground currents and each of the second actual sheath ground currents comprises: determining the fault classification of the high-voltage cable according to the first actual sheath grounding current and the second actual sheath grounding current:
determining a high-voltage cable fault classification according to each of the first actual sheath ground currents and each of the second actual sheath ground currents, comprising:
determining phase difference absolute values of the first actual sheath grounding currents and the second actual sheath grounding currents on different cable sheath loops;
determining phase ratio and amplitude ratio of each first actual sheath grounding current and each second actual sheath grounding current on the same cable sheath loop;
and determining the fault classification of the high-voltage cable according to the absolute value of the phase difference, the phase ratio and the amplitude ratio.
3. The high voltage cable fault testing method of claim 1, further comprising: acquiring the wire core voltage of each phase of the single-core cable, the wire core length of each phase of the single-core cable and the wire core capacitance parameter of each phase of the single-core cable;
determining sheath leakage current on each cable metal sheath loop according to the wire core line voltage, the wire core length and the wire core capacitance parameters;
obtaining core line currents of each phase of the single-core cable and mutual inductance parameters of the core lines of each phase of the single-core cable to each cable metal protective layer;
determining a sheath ring current on each cable metal sheath loop according to the wire core current and the mutual inductance parameter;
and determining theoretical sheath grounding current on each cable metal sheath loop according to the sheath leakage current and the sheath ring current.
4. The method for testing faults of a high voltage cable according to claim 3, wherein a high voltage cable fault is determined based on each of said first actual sheath ground currents and each of said second actual sheath ground currents, further comprising: and determining whether the high-voltage cable has a fault according to the first actual sheath grounding current, the second actual sheath grounding current and the theoretical sheath grounding current on each cable sheath loop.
5. The method of claim 4, wherein determining whether a high voltage cable is faulty based on each of said first actual sheath ground currents, said second actual sheath ground currents, and each of said theoretical sheath ground currents on each of said sheath loops comprises:
and when the first actual sheath grounding current or the second actual sheath grounding current on each cable sheath loop is different from the theoretical sheath grounding current, determining that the high-voltage cable has a fault.
6. The method for testing the fault of the high-voltage cable according to claim 5, wherein the sheath leakage current on each cable metal sheath loop is determined according to the wire core line voltage, the wire core length and the wire core capacitance parameters, and specifically comprises the following steps:
I A1 ＝jwU A L A1 C A
wherein: u shape A The voltage vector of a core of the A-phase single-core cable is obtained; l A1 The length of the cable metal sheath A1; c A The core capacitance of the A-phase single core cable is obtained; because the lengths of the cable metal protective layer A2 and the cable metal protective layer A3 are the same as the length of the cable metal protective layer A1, the sheath leakage currents of the cable metal protective layer A2 and the cable metal protective layer A3 are the same as the sheath leakage current of the cable metal protective layer A1;
I B1 ＝jwU B L B1 C B
wherein, U B The core voltage vector of the B-phase single-core cable is obtained; l B1 The length of the cable metal sheath B1; c B The core capacitance of the B-phase single-core cable is obtained; because the lengths of the cable metal protective layer B2 and the cable metal protective layer B3 are the same as the length of the cable metal protective layer B1, the sheath leakage currents of the cable metal protective layer B2 and the cable metal protective layer B3 are the same as the sheath leakage current of the cable metal protective layer B1;
I C1 ＝jwU C L C1 C C
wherein, U C The core voltage vector of the C-phase single-core cable is obtained; l C1 The length of the cable metal sheath C1; c C The core capacitance is the core capacitance of the C-phase single-core cable; because the lengths of the cable metal sheath C2 and the cable metal sheath C3 are the same as the length of the cable metal sheath C1, the sheath leakage currents of the cable metal sheath C2 and the cable metal sheath C3 are the same as the sheath leakage current of the cable metal sheath C1.
7. The method for testing the fault of the high-voltage cable according to claim 6, wherein the core capacitance parameters are specifically:
wherein epsilon r Is a relative dielectric constant, D C The diameter of a single-core cable core; δ is the thickness of the insulator.
8. The method of claim 7, wherein the sheath loop current on each of the cable metal sheath loops is determined according to the core current and the mutual inductance parameter; the method specifically comprises the following steps:
wherein, U SCn (n =1,2,3) is the induced voltage of each section of cable metal sheath; z mAn 、Z mBn And Z mCn (n =1,2,3) is the equivalent impedance of each section of cable metal sheath; re and Rg are grounding resistors at two ends of the cross interconnection main section; i is m1 、I m2 And I m3 Sheath circulating currents flowing through the cable metal sheath loops A1-B2-C3, B1-C2-A3 and C1-A2-B3 respectively;
taking the induced voltage of the metal sheath of the A1 cable as an example; u shape SA1 ＝-jw(I A L AA +I B M AB +I C M AC )l A1 (ii) a The induced voltage of the A1 cable metal sheath comprises A phase single-phase cable to A1 section metalSheath induced voltage adds the mutual inductance generated voltage of B looks and C looks single core cable to A1 section cable metal sheath, in the formula: i is A 、I B 、I C The core currents of the cable A, the cable B and the cable C are respectively; LAA is the mutual inductance coefficient of the A-phase single-core cable to the cable metal sheath A1; MAB and MAC are mutual inductance coefficients of the B-phase single-core cable and the C-phase single-core cable to the A1 cable metal sheath respectively; the method for calculating the induced voltage of the small sections of the other metal protective layers is similar to the induced voltage of the metal protective layer of the A1 cable.
9. The method of claim 8, wherein determining a theoretical sheath ground current on each of said cable metal sheath loops based on said sheath leakage current and said sheath loop current comprises:
and the theoretical sheath grounding current on each cable metal sheath loop is the vector sum of the sheath leakage current and the sheath ring current.
10. The method according to claim 9, wherein the determining a theoretical sheath ground current on each of the sheath loops according to the sheath leakage current and the sheath loop current comprises:
I 1a ＝(I LA1 +I LB2 +I LC3 )-(I LR1 +I RB2 +I RC3 )-I m1
I 1b ＝(I LB1 +I LC2 +I LA3 )-(I RB1 +I RC2 +I RA3 )-I m2
I 1c ＝(I LC1 +I LA2 +I LB3 )-(I RC1 +I RA2 +I RB3 )-I m3
I 2a ＝(I RB1 +I RC2 +I RA3 )-(I LB1 +I LC2 +I LA3 )+I m2
I 2b ＝(I RC1 +I RA2 +I RB3 )-(I LC1 +I LA2 +I LB3 )+I m3
I 1a ＝(I RA1 +I RB2 +I RC3 )-(I LA1 +I LB2 +I LC3 )+I m1
wherein: i is 1a And I 2c The theoretical sheath grounding current on the cable metal sheath loop A1-B2-C3 is reflected together; i is 1b And I 2a The theoretical sheath grounding current on the cable metal sheath loop B1-C2-A3 is reflected together; i is 1c And I 2b The theoretical sheath grounding current on the cable metal sheath loop C1-A2-B3 is reflected together; i is m1 、I m2 And I m3 Sheath circulating currents flowing through the cable metal sheath loops A1-B2-C3, B1-C2-A3 and C1-A2-B3 respectively; i is LAn 、I LBn 、I LCn The current component which flows to the left correspondingly on each section of the cable metal sheath is the leakage current; i is RAn 、I RBn And I RCn The component of the leakage current which flows to the right correspondingly on each section of the cable metal sheath; here, the component flowing to the right on the A1 cable metal sheath is taken as an example;
wherein ZmLA1 and ZmRA1 are respectively equivalent impedance of the left side and the right side of the A1 cable metal sheath; zmLA1 forms Z with ZmRA1 mA1 The impedance is the integral impedance of the A1 cable metal sheath; the corresponding right-going flow component on the other lengths of cable jacket is similar.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111983381A (en) * | 2020-08-10 | 2020-11-24 | 国网江苏省电力有限公司电力科学研究院 | Power cable line cross interconnection box fault positioning method and device |
| CN115825534A (en) * | 2023-02-23 | 2023-03-21 | 国网江苏省电力有限公司电力科学研究院 | Phase calibration cable sheath layer circulating current monitoring method and system |
| CN116299050A (en) * | 2023-05-17 | 2023-06-23 | 广东电网有限责任公司汕尾供电局 | Method, system, equipment and storage medium for detecting faults of protective layer |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111983381A (en) * | 2020-08-10 | 2020-11-24 | 国网江苏省电力有限公司电力科学研究院 | Power cable line cross interconnection box fault positioning method and device |
| CN111983381B (en) * | 2020-08-10 | 2023-07-21 | 国网江苏省电力有限公司电力科学研究院 | Fault positioning method and device for power cable line cross-connection box |
| CN115825534A (en) * | 2023-02-23 | 2023-03-21 | 国网江苏省电力有限公司电力科学研究院 | Phase calibration cable sheath layer circulating current monitoring method and system |
| CN116299050A (en) * | 2023-05-17 | 2023-06-23 | 广东电网有限责任公司汕尾供电局 | Method, system, equipment and storage medium for detecting faults of protective layer |
| CN116299050B (en) * | 2023-05-17 | 2023-08-11 | 广东电网有限责任公司汕尾供电局 | Method, system, equipment and storage medium for detecting faults of protective layer |
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