CN106771843B - Fault traveling wave distance measurement method for single-core power cable - Google Patents
Fault traveling wave distance measurement method for single-core power cable Download PDFInfo
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- CN106771843B CN106771843B CN201510808586.9A CN201510808586A CN106771843B CN 106771843 B CN106771843 B CN 106771843B CN 201510808586 A CN201510808586 A CN 201510808586A CN 106771843 B CN106771843 B CN 106771843B
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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
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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
- G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention relates to a fault traveling wave distance measurement method of a single-core power cable, which comprises the following steps: connecting a traveling wave distance measuring device to the single-core power cable; eliminating wave impedance change generated by cross interconnection of intermediate connectors of the single-core power cable; and fault location is carried out on the single-core power cable through the traveling wave location device. The invention inserts the metal protective layer at the cross interconnection position of the middle joint of the single-core power cable into the capacitor or directly grounds the metal protective layer, can basically eliminate the change of wave impedance at the position and eliminate the refraction and reflection of the traveling wave signal at the position, thereby leading the fault traveling wave signal to be capable of being transmitted in full line when the fault traveling wave distance measurement is carried out, and realizing the full-line fault traveling wave distance measurement of the single-core power cable.
Description
Technical Field
The invention relates to the technical field of power equipment detection, in particular to a fault traveling wave distance measurement method for a single-core power cable.
Background
With the technical progress and the improvement of the power supply quality requirement, the proportion of the power cable in the power grid is larger and larger, and the power cable gradually replaces an overhead line in some urban areas and develops to a high voltage grade. With the increase of the number of cables and the extension of the operation time, the occurrence of cable faults is more frequent. How to accurately and rapidly judge the position of the fault point of the power cable is a precondition guarantee for timely repairing the power cable and improving the power supply reliability.
The fault point positioning of the power cable generally needs three steps of fault diagnosis, fault location and accurate positioning. Wherein, the fault diagnosis can be carried out by a high-voltage test; pinpointing typically employs acoustic or other frequency sensing techniques. Fault location, also called fault rough measurement, is to apply a test signal to a faulty cable core using a suitable instrument at one or both ends of the cable, or to measure and analyze fault information on line, to preliminarily determine the distance from a fault point to a certain end, and to provide range information for accurate positioning. The fault location method of the power cable is various, generally divided into a traveling wave method and an impedance method, and further divided into off-line location and on-line location according to the running state of the cable. In order to accurately find the fault point of the power cable as soon as possible and reduce the engineering quantity and the power failure time of ground excavation and the like, the fault traveling wave distance measurement technology is widely applied.
The traveling wave method utilizes high voltage to carry out electric breakdown on cable faults, and the distance between a fault point and a test point can be calculated by measuring the time from the fault point to the test point of electric pulses which are broken down and discharged at the fault point. The fault traveling wave distance measurement is not affected by factors such as fault point transition resistance, line structure and the like, and the distance measurement precision is high, so that the fault traveling wave distance measurement is more widely applied.
Generally, a power cable and a control communication cable of 35kV or below are in a three-core or multi-core (low-voltage power cable or four-core or five-core cable with neutral wire, protective wire and the like added), and the external synthetic magnetic field of the cable core wire is weak, and a magnetic protective material can be used. The shielding protective layer of the cable intermediate joint is usually directly connected and is not grounded, and the wave impedance change of the intermediate joint is very small, so that the wave impedance of the cable overall length is basically unchanged, the refraction and reflection of the intermediate joint on fault location traveling wave signals are very weak, and the identification and judgment of the signals are not influenced. The travelling wave distance measurement method is widely applied to power cables with more than three cores and control communication cables, and develops on-line distance measurement or a cable early warning technology by using weak discharge signals when the cables to be damaged run.
For manufacturing and construction reasons, single-core power cables, especially power cables of 110kV or more, are generally used for power cables of 35kV and above. For a longer single-core power cable, in order to avoid breakdown of an insulating outer protection layer, the related regulations require a longer power cable line, the cable is divided into 3 times of sections, the metal protection layers are in cross interconnection at each intermediate joint, and the metal protection layers are grounded through the protector, so that the induction voltage of the metal protection layers is not more than 50V, and overvoltage hazards are reduced. According to analysis, after metal sheaths at the middle joint of the single-core power cable are crossed and interconnected, theoretically, an electric field of an insulating layer of the cable is equivalent to an electric field of external air in series, and wave impedance of the cable is greatly changed at the middle joint. Therefore, the traveling wave signals are seriously refracted and reflected at the cross interconnection position of the middle joint of the single-core power cable, so that the traditional traveling wave distance measurement technology is seriously misjudged and cannot be smoothly realized. The field practical experience shows that from the test point, the traveling wave distance meter can judge that the fault point position is the first intermediate joint at the fault point behind the first intermediate joint of the single-core power cable with the cross-interconnected intermediate joints, and the traveling wave distance measurement method is difficult to be practically applied to the single-core power cable practically and comprises an on-line method and an off-line method.
Disclosure of Invention
Based on the problems, the invention provides a fault traveling wave distance measurement method for a single-core power cable, which is characterized in that a metal protective layer at the cross interconnection position of an intermediate joint of the single-core power cable is connected into a capacitor or directly grounded, so that the change of wave impedance at the position can be basically eliminated, and the refraction and reflection of a traveling wave signal at the position can be eliminated, so that the fault traveling wave signal can be transmitted in a whole line when fault traveling wave distance measurement is carried out, and the whole-line fault traveling wave distance measurement of the single-core power cable is realized.
In order to achieve the above object, the present invention provides a fault traveling wave ranging method for a single-core power cable, comprising:
connecting a traveling wave distance measuring device to the single-core power cable;
eliminating wave impedance change generated by cross interconnection of intermediate connectors of the single-core power cable;
and fault location is carried out on the single-core power cable through the traveling wave location device.
The elimination of the wave impedance change caused by the cross interconnection of the intermediate connectors of the single-core power cable specifically includes:
the metal sheath of the middle joint of the single-core power cable is directly grounded, and the metal sheath at the middle joint of the single-core power cable is grounded through a first capacitor or a second capacitor is connected in series between two sections of metal sheaths of the same phase of the middle joint of the single-core power cable.
Wherein, the metal sheath direct ground connection of single core power cable intermediate head specifically includes:
and the sheath protector is grounded in a short circuit mode, and the metal sheath of the middle joint of the single-core power cable is directly grounded.
Wherein, will the metal sheath of single core power cable intermediate head department specifically includes through first condenser ground connection: the first capacitor is connected in series between the metal sheath of the single-core power cable middle joint and the ground, and the first capacitor and the sheath protector are connected in parallel and grounded.
Wherein, through traveling wave range unit is right single core power cable carries out fault detection, specifically includes:
performing fault point breakdown on the single-core power cable under high voltage;
the single-core power cable generates a fault high-frequency pulse traveling wave signal;
collecting the high-frequency pulse traveling wave signal;
and detecting the position information of the fault point according to the high-frequency pulse traveling wave signal.
The fault traveling wave distance measurement method of the single-core power cable is based on the principle of traveling wave distance measurement, a metal sheath at the cross interconnection position of the middle joint of the single-core power cable is connected into a capacitor or is directly grounded, an electric field between the metal sheath and the ground caused by the cross interconnection of the middle joint of the short-circuit cable can basically eliminate the change of wave impedance at the position and eliminate the refraction and reflection of a traveling wave signal at the position, so that the fault traveling wave signal can be transmitted in a whole line when the fault traveling wave distance measurement is carried out, and the whole-line fault traveling wave distance measurement of the single-core power cable is realized.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
fig. 1 shows a flow chart of the fault traveling wave ranging method of the single-core power cable of the invention.
Fig. 2 shows a schematic connection diagram of the capacitor of the first embodiment of the fault travelling wave ranging method of the present invention.
Fig. 3 shows a schematic connection diagram of the capacitor of a second embodiment of the fault travelling wave ranging method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. 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.
Fig. 1 shows a flow chart of the fault traveling wave ranging method of the single-core power cable of the invention.
Referring to fig. 1, the fault traveling wave distance measurement method of the single-core power cable of the invention specifically comprises the following steps:
s1, connecting the traveling wave distance measuring device to the single-core power cable;
s2, eliminating wave impedance change generated by cross interconnection of the intermediate joint of the single-core power cable;
and S3, fault location is carried out on the single-core power cable through the traveling wave location device.
In the embodiment of the present invention, the traveling wave distance measuring device may use a single-ended or double-ended, online or offline, one or more pulses, a dc pulse, an ac sine wave, or a mixed waveform voltage, which is not limited herein.
In addition, step S2, eliminating a wave impedance change caused by cross-connection of the intermediate joint of the single-core power cable specifically includes:
the metal sheath of the middle joint of the single-core power cable is directly grounded, and the metal sheath at the middle joint of the single-core power cable is grounded through a first capacitor or a second capacitor is connected in series between two sections of metal sheaths of the same phase of the middle joint of the single-core power cable.
In the method, the metal sheath of the middle joint of the single-core power cable is directly or indirectly grounded, an electric field between the metal sheath and the ground caused by the cross interconnection of the middle joint of the cable can be short-circuited, the change of wave impedance at the position can be basically eliminated, and the refraction and reflection of the traveling wave signal at the position can be eliminated, so that the fault traveling wave signal can be transmitted in a full line when fault traveling wave ranging is carried out.
The fault traveling wave ranging method of the present invention is described in detail below by specific embodiments.
Fig. 2 shows a schematic connection diagram of the capacitor of the first embodiment of the fault travelling wave ranging method of the present invention.
In one embodiment, as shown in fig. 2, the metal sheaths of the intermediate joint of the single core power cable are respectively connected to one end of the sheath protector 20 through the cross-connect lines 10, the other end of the sheath protector 20 is grounded, and the capacitor 30 is connected in parallel to the sheath protector 20.
In the above embodiment, the capacitance of the capacitor 30 is selected such that the impedance is close to 0 for a travelling wave signal; for power frequency induction voltage or test frequency voltage, such as oscillating wave or variable frequency test power supply, the impedance is relatively large so as to avoid influencing the normal operation or test state of the cable.
In particular, at the cable wave impedance Zc50 omega, power frequency f050Hz and the lowest frequency f of the travelling wavewUnder the condition of 10kHz, the capacity of the capacitor is selected as follows:
impedance to travelling wave frequency being small, i.e.
E.g. take 0.05ZcI.e. 2.5 omega, then the capacitor
For line frequency impedance, capacitor impedance
Maximum capacitance current, calculated as maximum induced voltage 50V
The impedance of the capacitor to the cable fault traveling wave signal is small, and the impedance to the power frequency signal is large, so that the wave impedance air part of the intermediate joint is short-circuited, the wave impedance change is small, and the fault traveling wave signal hardly undergoes refraction and reflection and smoothly passes through the intermediate joint.
Fig. 3 shows a schematic connection diagram of the capacitor of a second embodiment of the fault travelling wave ranging method of the present invention.
In another embodiment, as shown in fig. 3, the metal sheath of the middle joint of the single core power cable is connected in series to the capacitor 40 through the cross-connecting line 10, and then the capacitor 40 is connected to one end of the sheath protector 20, and the other end of the sheath protector 20 is grounded.
In the above embodiment, the same applies to the cable wave impedance Zc50 omega, power frequency f050Hz and the lowest frequency f of the travelling wavewUnder the condition of 10kHz, the capacity of the capacitor is selected as follows:
impedance to travelling wave frequency being small, i.e.
E.g. take 0.1ZcI.e. 5 omega, then the capacitor
For line frequency impedance, capacitor impedance
Maximum capacitance current, calculated as maximum induced voltage 50V
Based on the above, the capacitor in this embodiment has a small impedance for the cable fault traveling wave signal and a large impedance for the power frequency signal, so that the wave impedance of the cross interconnection of the intermediate connectors is short-circuited, the change of the wave impedance is small, and the fault traveling wave signal can pass through smoothly.
In another embodiment of the present invention, in step S2, eliminating the wave impedance variation generated by the cross-connection of the middle connectors of the single-core power cable may be: and directly grounding the metal sheath of the middle joint of the single-core power cable.
In this embodiment, the direct grounding of the metal sheath is equivalent to physically connecting the metal sheath directly to the ground, which is more favorable for the traveling wave transmission, but the direct grounding of the metal sheath affects the current of the grounding return line when the cable operates normally, so the scheme of this embodiment is suitable for performing fault traveling wave ranging during the power failure test.
In addition, step S3 of the present invention may be, in one embodiment:
performing fault point breakdown on the single-core power cable under high voltage;
the single-core power cable generates a fault high-frequency pulse traveling wave signal;
collecting the high-frequency pulse traveling wave signal;
and detecting the position information of the fault point according to the high-frequency pulse traveling wave signal.
However, the traveling wave ranging method of step S3 of the present invention is not limited to the above-described embodiment, and any specific procedure applicable to the traveling wave ranging method of the present invention is applicable to the present invention.
The fault traveling wave distance measurement method is based on the principle of traveling wave distance measurement, and basically eliminates the wave impedance change of the cable at the position of the cable by grounding or connecting a capacitor at the cross interconnection position of the metal sheath of the single-core power cable and short-circuiting the electric field between the metal sheath and the ground caused by the cross interconnection of the intermediate joint of the cable, thereby avoiding the refraction and reflection of the fault traveling wave signal, enabling the fault traveling wave signal of the cable to smoothly pass through the intermediate joint, and further realizing the off-line or on-line traveling wave distance measurement of the fault of the single-core power cable.
Although the present invention has been described in detail with reference to examples, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (2)
1. A fault traveling wave distance measurement method of a single-core power cable is characterized by comprising the following steps:
connecting a traveling wave distance measuring device to the single-core power cable;
eliminating wave impedance change generated by cross interconnection of intermediate connectors of the single-core power cable;
fault location is carried out on the single-core power cable through the traveling wave location device;
the elimination of the wave impedance change caused by the cross interconnection of the intermediate connectors of the single-core power cable specifically includes:
the metal sheath of the middle joint of the single-core power cable is directly grounded, the metal sheath at the middle joint of the single-core power cable is grounded through a first capacitor, or a second capacitor is connected in series between two sections of metal sheaths of the same phase of the middle joint of the single-core power cable;
the metal sheath direct ground connection of single core power cable intermediate head specifically includes:
short-circuit grounding the sheath protector, and directly grounding the metal sheath of the middle joint of the single-core power cable;
will the metal sheath of single core power cable intermediate head department specifically includes through first condenser ground connection: the first capacitor is connected in series between the metal sheath of the single-core power cable middle joint and the ground, and the first capacitor and the sheath protector are connected in parallel and grounded.
2. The traveling wave fault location method according to claim 1, wherein the fault detection of the single-core power cable by the traveling wave location device specifically comprises:
performing fault point breakdown on the single-core power cable under high voltage;
the single-core power cable generates a fault high-frequency pulse traveling wave signal;
collecting the high-frequency pulse traveling wave signal;
and detecting the position information of the fault point according to the high-frequency pulse traveling wave signal.
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| CN108896874B (en) * | 2018-07-10 | 2019-09-24 | 中国矿业大学 | A kind of fault positioning method for transmission line of end connection short-term road |
| CN110895299A (en) * | 2018-09-12 | 2020-03-20 | 中国石油化工股份有限公司 | Power cable ranging identification method |
| CN110275125B (en) * | 2019-06-18 | 2022-11-25 | 中国电力科学研究院有限公司 | System and method for calibrating dynamic characteristics of impulse current measuring device |
| CN112363008A (en) * | 2020-09-17 | 2021-02-12 | 广州长川科技有限公司 | Cable fault and running state comprehensive monitoring method and system |
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