CN117031357B - Method and device for positioning grounding defect of single-core cable metal sheath with single-end grounded - Google Patents

Method and device for positioning grounding defect of single-core cable metal sheath with single-end grounded Download PDF

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Publication number
CN117031357B
CN117031357B CN202311289922.4A CN202311289922A CN117031357B CN 117031357 B CN117031357 B CN 117031357B CN 202311289922 A CN202311289922 A CN 202311289922A CN 117031357 B CN117031357 B CN 117031357B
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metal sheath
core cable
phase
defect
current
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CN117031357A (en
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曹京荥
陈杰
孙蓉
谭笑
李陈莹
张伟
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Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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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
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • 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
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/58—Testing of lines, cables or conductors
    • 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

Abstract

The invention discloses a method and a device for positioning the grounding defect of a single-end grounded single-core cable metal sheath, comprising the following steps: acquiring a three-phase circulation current of the single-core cable metal sheath, and comparing the three-phase circulation current of the single-core cable metal sheath with the capacitance current of the single-core cable metal sheath to obtain a defect phase; injecting a first alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable; injecting a second alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable; and obtaining the distance between the defective phase defect point of the grounding end of the metal sheath of the single-core cable and the direct grounding point according to the effective value of the response current and the effective value of the response voltage.

Description

Method and device for positioning grounding defect of single-core cable metal sheath with single-end grounded
Technical Field
The invention belongs to the technical field of power transmission and transformation, and particularly relates to a method and a device for positioning a grounding defect of a single-end grounded single-core cable metal sheath.
Background
When the single-end grounding section of the single-core cable metal sheath is abnormally grounded, if the defects are not detected and eliminated in time, the problems of increased circulation of the cable metal sheath and heating of the cable are caused, and even the problems of electrochemical corrosion and perforation water inflow of the metal sheath are caused.
In order to solve the above problems, it is common practice to: the corresponding line is powered off, but the method has the defects of slow detection period, low efficiency and the like.
Disclosure of Invention
The invention aims to: in order to solve the problems of low detection period, low efficiency and the like in the prior art, the invention provides the method and the device for positioning the grounding defect of the single-core cable metal sheath, which can be used for positioning the grounding defect of the single-core cable metal sheath in a charged manner, and have the advantages of simplicity in operation, convenience in operation, high efficiency and the like.
The technical scheme is as follows: a method for positioning the ground defect of a single-end grounded single-core cable metal sheath comprises the following steps:
step 1: acquiring three-phase circulation of the single-core cable metal sheath, and sequentially comparing the three-phase circulation of the single-core cable metal sheath with the capacitance current of the single-core cable metal sheath to obtain a defect phase;
step 2: injecting a first alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable; injecting a second alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable;
step 3: and (3) obtaining a defective phase defective point resistance according to the response current effective value and the response voltage effective value obtained in the step (2), and obtaining the distance between the defective phase defective point of the grounding end of the metal sheath of the single-core cable and the direct grounding point by utilizing the proportional relation of the resistance and the length.
Further, in step 1, the single-core cable metal sheath capacitance current is calculated according to the following formula:
（1）
in the method, in the process of the invention,capacitive current for metal sheath of single-core cable, +.>Is the rated voltage of the metal sheath of the single-core cable,angular frequency of metal sheath for single-core cable, +.>Is the capacitance between the core of the single-core cable and the metal sheath.
Further, in step 1, the step of comparing the three-phase circulation current of the single-core cable metal sheath with the capacitance current of the single-core cable metal sheath sequentially to obtain a defect phase includes:
and comparing the three-phase circulation of the single-core cable metal sheath with the single-core cable metal sheath capacitance current in sequence, and judging that a certain phase with the circulation being more than or equal to 5 times of the single-core cable metal sheath capacitance current is a defective phase and other non-defective phases are normal phases.
Further, when the effective value of the response voltage is obtained at the defect phase of the insulation end of the single-core cable metal sheath and is the effective value of the response voltage between the defect phase of the insulation end of the single-core cable metal sheath and the ground, the step 3 includes:
the following equations are combined:
（2）
where F1 is the frequency of the injected first AC coupled signal,f2 is the frequency of the injected second AC coupling signal for the impedance of the defective phase segment at frequency F1, +.>For the impedance of the defective phase segment at frequency F2, and (2)>For the distance between the defect point of the metal sheath grounding end of the single-core cable and the direct grounding point, < ->Resistance of metal sheath for single-core cable, +.>The length of the metal sheath of the single-core cable; />For the effective voltage value of the injected first ac-coupled signal,effective value of response voltage obtained for injection of the first ac coupling signal, < >>Effective value of response current for injection of the first ac coupling signal, < >>For the effective voltage value of the injected second ac-coupled signal,/or->Response voltage effective value obtained for injecting the second ac coupling signal, < >>A response current effective value obtained for injecting the second alternating-current coupling signal;
solving (2) to obtain the distance between the defective phase defect point of the metal sheath grounding end of the single-core cable and the direct grounding point。
Further, when the effective value of the response voltage is obtained at the defective phase of the insulating end of the single-core cable metal sheath and is the effective value of the response voltage between the defective phase and the normal phase of the insulating end of the single-core cable metal sheath, the step 3 includes:
the following equations are combined:
（3）
where F1 is the frequency of the injected first AC coupled signal,f2 is the frequency of the injected second AC coupling signal for the impedance of the defective phase segment at frequency F1, +.>For the impedance of the defective phase segment at frequency F2, and (2)>For the distance between the defect point of the metal sheath grounding end of the single-core cable and the direct grounding point, < ->Resistance of metal sheath for single-core cable, +.>The length of the metal sheath of the single-core cable; />Effective value of response voltage obtained for injection of the first ac coupling signal, < >>Effective value of response current for injection of the first ac coupling signal, < >>Response voltage effective value obtained for injecting the second ac coupling signal, < >>A response current effective value obtained for injecting the second alternating-current coupling signal;
solving (3) to obtain the distance between the defective phase defect point of the metal sheath grounding end of the single-core cable and the direct grounding point。
The invention discloses a single-end grounded single-core cable metal sheath grounding defect positioning device, which comprises: the device comprises an excitation source, a current measuring unit, a current clamp, a coupling clamp, a voltage measuring unit and a calculating unit;
the excitation source is connected with the coupling pliers and is used for injecting an alternating current coupling signal into the grounding end of the single-core cable metal sheath;
the current measuring unit is connected with the current clamp and is used for acquiring three-phase circulation of the metal sheath of the single-core cable and acquiring response current of a defective phase of the grounding end of the metal sheath of the single-core cable when the AC coupling signal is injected into the grounding end of the metal sheath of the single-core cable;
the voltage measurement unit is used for acquiring the response voltage of the defect phase of the insulating end of the metal sheath of the single-core cable when the grounding end of the metal sheath of the single-core cable is injected with an alternating current coupling signal;
the calculation unit is used for judging a defect phase according to the three-phase circulation of the single-core cable metal sheath, obtaining a defect point resistance of the defect phase according to the response current obtained by the current measurement unit and the response voltage obtained by the voltage measurement unit, and obtaining the distance between the defect point of the single-core cable metal sheath grounding end defect phase and the direct grounding point by utilizing the proportional relation of the resistance and the length.
Further, in the calculating unit, the determining the defective phase according to the three-phase circulation of the single-core cable metal sheath specifically includes:
and comparing the three-phase circulation of the single-core cable metal sheath with the single-core cable metal sheath capacitance current in sequence, and judging that a certain phase with the circulation being more than or equal to 5 times of the single-core cable metal sheath capacitance current is a defective phase and other non-defective phases are normal phases.
Further, the capacitance current of the metal sheath of the single-core cable is calculated according to the following formula:
（1）
in the method, in the process of the invention,capacitive current for metal sheath of single-core cable, +.>Is the rated voltage of the metal sheath of the single-core cable,angular frequency of metal sheath for single-core cable, +.>Is the capacitance between the core of the single-core cable and the metal sheath.
Further, when the response voltage of the defect phase of the insulating end of the single-core cable metal sheath obtained by the voltage measurement unit is the response voltage between the defect phase of the insulating end of the single-core cable metal sheath and the ground, in the calculation unit, the defect point resistance of the defect phase is obtained according to the response current obtained by the current measurement unit and the response voltage obtained by the voltage measurement unit, and then the distance between the defect point of the defect phase of the grounding end of the single-core cable metal sheath and the direct grounding point is obtained by utilizing the proportional relation between the resistance and the length, which specifically comprises:
the following equations are combined:
（2）
where F1 is the frequency of the injected first AC coupled signal,f2 is the frequency of the injected second AC coupling signal for the impedance of the defective phase segment at frequency F1, +.>For the impedance of the defective phase segment at frequency F2, and (2)>For the distance between the defect point of the metal sheath grounding end of the single-core cable and the direct grounding point, < ->Resistance of metal sheath for single-core cable, +.>The length of the metal sheath of the single-core cable; />For the effective voltage value of the injected first ac-coupled signal,effective value of response voltage obtained for injection of the first ac coupling signal, < >>Effective value of response current for injection of the first ac coupling signal, < >>To be injected intoEffective voltage value of two AC coupling signals, < >>Response voltage effective value obtained for injecting the second ac coupling signal, < >>A response current effective value obtained for injecting the second alternating-current coupling signal;
solving (2) to obtain the distance between the defective phase defect point of the metal sheath grounding end of the single-core cable and the direct grounding point。
Further, when the response voltage of the defect phase of the insulating end of the single-core cable metal sheath obtained by the voltage measurement unit is the response voltage between the defect phase and the normal phase of the insulating end of the single-core cable metal sheath, in the calculation unit, the defect point resistance of the defect phase is obtained according to the response current obtained by the current measurement unit and the response voltage obtained by the voltage measurement unit, and then the distance between the defect point of the defect phase of the grounding end of the single-core cable metal sheath and the direct grounding point is obtained by utilizing the proportional relation between the resistance and the length, which specifically comprises:
the following equations are combined:
（3）
where F1 is the frequency of the injected first AC coupled signal,f2 is the frequency of the injected second AC coupling signal for the impedance of the defective phase segment at frequency F1, +.>For the impedance of the defective phase segment at frequency F2, and (2)>Is a metal protector for single-core cableDistance between defective point of ground terminal and direct ground point, < >>Resistance of metal sheath for single-core cable, +.>The length of the metal sheath of the single-core cable; />Effective value of response voltage obtained for injection of the first ac coupling signal, < >>Effective value of response current for injection of the first ac coupling signal, < >>Response voltage effective value obtained for injecting the second ac coupling signal, < >>A response current effective value obtained for injecting the second alternating-current coupling signal;
solving (3) to obtain the distance between the defective phase defect point of the metal sheath grounding end of the single-core cable and the direct grounding point。
The beneficial effects are that: compared with the prior art, the invention has the following advantages:
(1) According to the method, the different-frequency alternating current signal is injected into the grounding end of the metal sheath of the single-core cable in a coupling way, the effective values of the different-frequency response voltage and the current of the defect phase are obtained, and the position of the defect section is calculated by applying the ohm law, the electromagnetic induction law and the relation between the resistance and the length, so that the grounding defect of the metal sheath of the single-core cable can be electrified and rapidly positioned, and the method has the advantages of simplicity and convenience in operation, high efficiency, good application prospect and the like;
(2) The device of the invention utilizes the coupling pliers to couple and inject different-frequency alternating current signals into the grounding end of the metal sheath of the single-core cable, obtains effective values of different-frequency response voltage and current of defect phases, and calculates the position of a defect section by utilizing ohm law, electromagnetic induction law and the relation between resistance and length, thereby realizing the purpose of quickly positioning the grounding defect of the metal sheath of the single-core cable with electricity.
Drawings
FIG. 1 is a schematic view of a single-core cable metal sheath with a single end grounded;
FIG. 2 is an equivalent circuit diagram of a single-core cable metal sheath with a single end grounded;
FIG. 3 is a schematic view of a device for positioning a ground fault of a single-core cable metal sheath with a single-end ground;
fig. 4 is a schematic diagram of a measurement connection of a ground fault locating device for a single-end grounded single-core cable metal sheath.
Detailed Description
As shown in fig. 1, one end of a single-core cable metal sheath 1 with one end grounded is connected into a direct grounding box 3 through a grounding lead 2 to realize direct grounding, the end is called a grounding end, and the direct grounding box 3 is connected into a grounding device through a common grounding lead; the other end of the single-core cable metal sheath 1 with the single end grounded is connected with the protection grounding box 4 to realize insulation to the ground, and the end is called an insulation end; the middle part of the single-core cable metal sheath 1 with the single end grounded is insulated and isolated from the external links through external insulation. Fig. 2 shows an equivalent circuit of a single-core cable metal sheath with one end grounded.
In any of the following embodiments, the ground defect of the single-end grounded single-core cable metal sheath 1 shown in fig. 1 and 2 is electrically positioned, so as to obtain the distance between the ground defect point of the ground terminal and the direct grounding box, which may be referred to as the distance between the ground defect point of the ground terminal and the direct grounding box. For convenience of presentation, the single-end grounded single-core cable metal sheath 1 is simply referred to as a single-core cable metal sheath, and in any of the following embodiments, the single-core cable metal sheath is referred to as a single-end grounded single-core cable metal sheath.
Examples
The embodiment discloses a method for live positioning of a ground defect of a single-core cable metal sheath with one end grounded, which mainly comprises the following steps:
step 1: acquiring a three-phase circulation current of the single-core cable metal sheath, and comparing the three-phase circulation current of the single-core cable metal sheath with the capacitance current of the single-core cable metal sheath to obtain a defect phase;
step 2: injecting a first alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable; injecting a second alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable;
step 3: and (3) calculating to obtain the distance between the defective phase defect point of the metal sheath grounding end of the single-core cable and the direct grounding point by using the ohm law and the relation between the resistance and the length according to the effective value of the response current and the effective value of the response voltage obtained in the step (2).
According to the embodiment, the different-frequency alternating current signals are injected into the coupling of the grounding end of the metal sheath of the single-core cable to obtain the response current and response voltage data under alternating current excitation of different frequencies of the defect phase, the distance between the defect point of the defect phase of the grounding end of the metal sheath of the single-core cable and the direct grounding point is obtained by calculating the relationship between ohm law, electromagnetic induction law and resistance and length, the grounding defect of the metal sheath of the single-core cable is electrified and rapidly positioned, and the problems that the circuit is required to be powered off and the detection period is long in the prior art are solved.
Examples
The embodiment discloses a method for live positioning of a ground defect of a single-core cable metal sheath with one end grounded, which mainly comprises the following steps:
step 1: obtaining the circulation of A phase, B phase and C phase of the metal sheath of the single-core cable;
step 2: calculating to obtain the capacitance current of the metal sheath of the single-core cable according to the formula (1):
（1）
in the method, in the process of the invention,capacitive current for metal sheath of single-core cable, +.>Is the rated voltage of the metal sheath of the single-core cable,angular frequency of metal sheath for single-core cable, +.>Is the capacitance between the core of the single-core cable and the metal sheath.
Step 3: circulating currents of A phase, B phase and C phase of the metal sheath of the single-core cable and capacitive currents of the metal sheath of the single-core cable respectivelyComparing, determining that the circulating current is greater than or equal to the capacitance current of the metal sheath of the single-core cable>A phase 5 times larger than that of the other phases is a defective phase, and other non-defective phases are normal phases;
step 4: injecting frequency into the grounding end of the metal sheath of the single-core cable to beThe effective voltage value is +.>Acquiring a response voltage effective value +.>The metal sheath of the single-core cable is groundedObtaining a response current effective value +.>The method comprises the steps of carrying out a first treatment on the surface of the Injecting frequency into the grounding end of the metal sheath of the single-core cable to be +.>The effective voltage value is +.>Obtaining effective value of response voltage between defect and ground of insulating end of metal sheath of single-core cable +.>Obtaining a response current effective value +.>；
Step 5: according to the characteristic that the resistance in the impedance does not change along with the frequency, the following equation is established by applying ohm's law and the relation between the resistance and the length:
（2）
in the method, in the process of the invention,for the impedance of the defective phase segment at frequency F1, and (2)>For the impedance of the defective phase segment at frequency F2,for the distance between the defect point of the metal sheath grounding end of the single-core cable and the direct grounding point, < ->Resistance of metal sheath for single-core cable, +.>The length of the metal sheath of the single-core cable;
step 6: solving the equation established in the step 5 to obtain the distance between the defect phase defect point of the metal sheath grounding end of the single-core cable and the direct grounding point。
According to the embodiment, the different-frequency alternating current signals are injected into the coupling of the grounding end of the metal sheath of the single-core cable to obtain the response current and response voltage data under alternating current excitation of different frequencies of the defect phase, the distance between the defect point of the defect phase of the grounding end of the metal sheath of the single-core cable and the direct grounding point is obtained by calculating the relationship between ohm law, electromagnetic induction law and resistance and length, the grounding defect of the metal sheath of the single-core cable is electrified and rapidly positioned, and the problems that the circuit is required to be powered off and the detection period is long in the prior art are solved.
Examples
The embodiment discloses a method for live positioning of a ground defect of a single-core cable metal sheath with one end grounded, which mainly comprises the following steps:
step 1: obtaining the circulation of A phase, B phase and C phase of the metal sheath of the single-core cable;
step 2: calculating to obtain the capacitance current of the metal sheath of the single-core cable according to the formula (1):
（1）
in the method, in the process of the invention,capacitive current for metal sheath of single-core cable, +.>Is the rated voltage of the metal sheath of the single-core cable,angular frequency of metal sheath for single-core cable, +.>Is the capacitance between the core of the single-core cable and the metal sheath.
Step 3: circulating currents of A phase, B phase and C phase of the metal sheath of the single-core cable and capacitive currents of the metal sheath of the single-core cable respectivelyComparing, determining that the circulating current is greater than or equal to the capacitance current of the metal sheath of the single-core cable>A phase 5 times larger than that of the other phases is a defective phase, and other non-defective phases are normal phases;
step 4: injecting frequency into the grounding end of the metal sheath of the single-core cable to beThe effective voltage value is +.>Acquiring effective value of response voltage between defect phase and normal phase of insulating end of metal sheath of single-core cableObtaining a response current effective value +.>The method comprises the steps of carrying out a first treatment on the surface of the Injecting frequency into the grounding end of the metal sheath of the single-core cable to be +.>The effective voltage value is +.>Obtaining effective value +.about.of response voltage between defect phase and normal phase of insulating end of metal sheath of single-core cable>Metal sheath joint for single core cableObtaining effective value of response current at defective phase of ground terminal>；
Step 5: according to the characteristic that the resistance in the impedance does not change along with the frequency, the following equation is established by applying ohm's law and the relation between the resistance and the length:（3）
in the method, in the process of the invention,for the impedance of the defective phase segment at frequency F1, and (2)>For the impedance of the defective phase segment at frequency F2,for the distance between the defect point of the metal sheath grounding end of the single-core cable and the direct grounding point, < ->Resistance of metal sheath for single-core cable, +.>The length of the metal sheath of the single-core cable;
step 6: solving the equation established in the step 5 to obtain the distance between the defect phase defect point of the metal sheath grounding end of the single-core cable and the direct grounding point。
According to the embodiment, the different-frequency alternating current signals are injected into the coupling of the grounding end of the metal sheath of the single-core cable to obtain the response current and response voltage data under alternating current excitation of different frequencies of the defect phase, the distance between the defect point of the defect phase of the grounding end of the metal sheath of the single-core cable and the direct grounding point is obtained by calculating the relationship between ohm law, electromagnetic induction law and resistance and length, the grounding defect of the metal sheath of the single-core cable is electrified and rapidly positioned, and the problems that the circuit is required to be powered off and the detection period is long in the prior art are solved.
Examples
As shown in fig. 3, this embodiment discloses a ground fault live positioning device for a single-core cable metal sheath with a single-end ground, which mainly includes: the live locator 5, the current clamp 6, the coupling clamp 7 and the voltage measuring unit 8. The live line locator 5 of the present embodiment includes an excitation source 51, a current measurement unit 52, an excitation voltage measurement unit 53, and a measurement control unit 54; the excitation source 51 is connected with the coupling clamp 7 and is used for injecting an alternating current coupling signal into the grounding end of the single-core cable metal sheath; the current measuring unit 52 is connected with the current clamp 6, and is used for obtaining alternating current induction current injected into the grounding end of the metal sheath of the single-core cable and obtaining response current of a defect phase of the grounding end of the metal sheath of the single-core cable when alternating current coupling signals are injected into the grounding end of the metal sheath of the single-core cable; the excitation voltage measuring unit 53 is connected between the excitation source 51 and the coupling clamp 7 and is used for acquiring alternating current induction voltage injected into the grounding end of the metal sheath of the single-core cable; excitation source 51, excitation voltage measurement unit 53, and current measurement unit 52 are all connected to measurement control unit 54, and measurement control unit 54 is configured to control the frequency and effective voltage value of excitation source 51. Fig. 4 shows a schematic diagram of a test connection.
The using steps of the electrified positioning device of the embodiment include:
step 1: the current clamp 6 is arranged on a grounding lead 2 of which the grounding end is connected with a direct grounding box 3, and a current measuring unit 52 in the electrified positioning instrument 5 acquires the three-phase circulation of the single-core cable metal sheath;
step 2: comparing the three-phase circulation with the single-core cable metal sheath capacitance current calculated in advance to obtain a defect phase;
step 3: the coupling clamp 7 is arranged on a common grounding lead connected with the grounding device through the direct grounding box 2, the current clamp 6 is arranged on a grounding lead connected with the direct grounding box 3 through a defective phase of the grounding end of the metal sheath of the single-core cable, and the voltage measuring unit 8 is arranged between a defective phase copper bar of the insulating end of the metal sheath of the single-core cable and the ground;
step 4: injecting a frequency different from the power frequency into the metal sheath joint end of the single-core cable by using an excitation source 51The effective voltage value is +.>Is used to obtain a response current effective value by means of the current measuring unit 52, the voltage measuring unit 8>And response voltage effective value +.>The method comprises the steps of carrying out a first treatment on the surface of the Injecting a frequency different from the power frequency into the metal sheath end of the single-core cable by using the excitation source 51>The effective voltage value is +.>Is used to obtain a response current effective value by means of the current measuring unit 52, the voltage measuring unit 8>And response voltage effective value +.>；
Step 5: according to the characteristic that the resistance in the impedance does not change along with the frequency, constructing a simultaneous equation to calculate and obtain the resistance of the defect point, and calculating to obtain the defect phase defect point of the grounding end of the metal sheath of the single-core cable from the direct grounding point by utilizing the proportional relation of the resistance and the lengthIs a position of (c). The method comprises the following steps:
（2）
in the method, in the process of the invention,for the impedance of the defective phase segment at frequency F1, and (2)>For the impedance of the defective phase segment at frequency F2,for the distance between the defect point of the metal sheath grounding end of the single-core cable and the direct grounding point, < ->Resistance of metal sheath for single-core cable, +.>Is the length of the metal sheath of the single-core cable.
According to the embodiment, the different-frequency alternating current signals are injected into the coupling of the grounding end of the metal sheath of the single-core cable to obtain the response current and response voltage data under alternating current excitation of different frequencies of the defect phase, the distance between the defect point of the defect phase of the grounding end of the metal sheath of the single-core cable and the direct grounding point is obtained by calculating the relationship between ohm law, electromagnetic induction law and resistance and length, the grounding defect of the metal sheath of the single-core cable is electrified and rapidly positioned, and the problems that the circuit is required to be powered off and the detection period is long in the prior art are solved.
Examples
As shown in fig. 3, this embodiment discloses a ground fault live positioning device for a single-core cable metal sheath with a single-end ground, which mainly includes: the live locator 5, the current clamp 6, the coupling clamp 7 and the voltage measuring unit 8. The live line locator 5 of the present embodiment includes an excitation source 51, a current measurement unit 52, an excitation voltage measurement unit 53, and a measurement control unit 54; the excitation source 51 is connected with the coupling clamp 7 and is used for injecting an alternating current coupling signal into the grounding end of the single-core cable metal sheath; the current measuring unit 52 is connected with the current clamp 6, and is used for obtaining alternating current induction current injected into the grounding end of the metal sheath of the single-core cable and obtaining response current of a defect phase of the grounding end of the metal sheath of the single-core cable when alternating current coupling signals are injected into the grounding end of the metal sheath of the single-core cable; the excitation voltage measuring unit 53 is connected between the excitation source 51 and the coupling clamp 7 and is used for acquiring alternating current induction voltage injected into the grounding end of the metal sheath of the single-core cable; excitation source 51, excitation voltage measurement unit 53, and current measurement unit 52 are all connected to measurement control unit 54, and measurement control unit 54 is configured to control the frequency and effective voltage value of excitation source 51. Fig. 4 shows a schematic diagram of a test connection. The current measurement accuracy of the current measurement unit of this embodiment is not lower than 1A, the measurement accuracy of the excitation voltage measurement unit is not lower than 1V, and the measurement accuracy of the voltage measurement unit is not lower than 1V.
The using steps of the electrified positioning device of the embodiment include:
step 1: the current clamp 6 is arranged on a grounding lead 2 of which the grounding end is connected with a direct grounding box 3, and a current measuring unit 52 in the electrified positioning instrument 5 acquires the three-phase circulation of the single-core cable metal sheath; the specific operation comprises the following steps:
(1) The current clamp 6 is arranged on an A-phase grounding lead of which the grounding end is connected with the direct grounding box 3, so as to obtain an A-phase circulation current IA of the single-core cable metal sheath;
(2) The current clamp 6 is arranged on a B-phase grounding lead wire of which the grounding end is connected with the direct grounding box 3, so as to obtain a B-phase circulation IB of the single-core cable metal sheath;
(3) The current clamp 6 is arranged on a C-phase grounding lead of the single-core cable metal sheath, the grounding end of which is connected with the direct grounding box 3, so as to obtain a C-phase circulation current IC of the single-core cable metal sheath;
step 2: comparing the three-phase circulation with the single-core cable metal sheath capacitance current calculated in advance to obtain a defect phase; the specific operation comprises the following steps:
calculating to obtain the capacitance current of the metal sheath of the single-core cable according to the formula (1):
（1）
in the method, in the process of the invention,capacitive current for metal sheath of single-core cable, +.>Is the rated voltage of the metal sheath of the single-core cable,angular frequency of metal sheath for single-core cable, +.>Is the capacitance between the core of the single-core cable and the metal sheath.
The A phase circulation IA, B phase circulation IB and C phase circulation IC are respectively connected with the three-phase capacitance current of the metal sheathComparing, determining that the circulating current is greater than or equal to the capacitance current of the metal sheath of the single-core cable>A phase 5 times larger than that of the other phases is a defective phase, and other non-defective phases are normal phases;
step 3: the coupling clamp 7 is arranged on a common grounding lead connected with the grounding device through the direct grounding box 2, the current clamp 6 is arranged on a defective phase of the metal sheath grounding end of the single-core cable and a grounding lead connected with the direct grounding box 3, and the voltage measuring unit 8 is arranged between a defective phase copper bar of the insulating end of the metal sheath of the single-core cable and a normal phase copper bar of the insulating end of the metal sheath of the single-core cable;
step 4: injecting a frequency different from the power frequency into the metal sheath joint end of the single-core cable by using an excitation source 51The effective voltage value is +.>Is measured by means of a current measuring unit 52, voltageThe unit 8 gets the response current effective value +.>And response voltage effective value +.>The method comprises the steps of carrying out a first treatment on the surface of the Injecting a frequency different from the power frequency into the metal sheath end of the single-core cable by using the excitation source 51>The effective voltage value is +.>Is used to obtain a response current effective value by means of the current measuring unit 52, the voltage measuring unit 8>And response voltage effective value +.>The method comprises the steps of carrying out a first treatment on the surface of the Excitation source 51 may inject ac coupled signals including, but not limited to, forward wave, square wave, triangular wave signals, excitation frequencies in the range of 5-1000Hz;
step 5: according to the characteristic that the resistance in the impedance does not change along with the frequency, constructing a simultaneous equation to calculate and obtain the resistance of the defect point, and calculating to obtain the defect phase defect point of the grounding end of the metal sheath of the single-core cable from the direct grounding point by utilizing the proportional relation of the resistance and the lengthIs a position of (c). The method comprises the following steps:
（3）
in the method, in the process of the invention,for the impedance of the defective phase segment at frequency F1, and (2)>For the impedance of the defective phase segment at frequency F2,for the distance between the defect point of the metal sheath grounding end of the single-core cable and the direct grounding point, < ->Resistance of metal sheath for single-core cable, +.>The length of the metal sheath of the single-core cable;
the device disclosed in embodiment 5 is used for defect positioning of a certain cross-high-speed rail single-core cable line adopting a metal sheath single-end grounding mode, and the specific operation comprises the following steps:
step 1: the current clamp 6 is arranged on an A-phase grounding lead of which the grounding end is connected with the direct grounding box 3, so as to obtain an A-phase circulation current IA=3.1A of the single-core cable metal sheath; the current clamp 6 is arranged on a B-phase grounding lead of the single-core cable metal sheath, the grounding end of which is connected with the direct grounding box 3, so as to obtain B-phase circulation ib=3.7A of the single-core cable metal sheath; installing a current clamp 6 on a C-phase grounding lead of a single-core cable metal sheath, wherein the C-phase grounding lead is connected with a direct grounding box 3, so as to obtain C-phase circulation current IC=200A of the single-core cable metal sheath;
step 2: the three-phase circulation current and the single-core cable metal sheath capacitance current calculated in advance are divided into three phases) Comparing, the C phase circulation IC=200A is more than 5 times of the three-phase capacitance current of the metal sheath, so the C phase is a defect phase of the metal sheath joint end of the single-core cable; phase A and phase B are matched with normal phases of the grounding end of the metal sheath of the single-core cable;
step 3: the coupling clamp 7 is arranged on a common grounding lead connected with the grounding device through the direct grounding box 2, the current clamp 6 is arranged on a grounding lead connected with the direct grounding box 3 through a C phase of the grounding end of the metal sheath of the single-core cable, and the voltage measuring unit 8 is arranged between a C phase copper bar and a B phase copper bar of the insulating end of the metal sheath of the single-core cable;
step 4: injecting a frequency different from the power frequency into the metal sheath joint end of the single-core cable by using an excitation source 51The effective voltage value is +.>Is used to obtain a response current effective value by means of the current measuring unit 52, the voltage measuring unit 8>And response voltage effective value +.>The method comprises the steps of carrying out a first treatment on the surface of the Injecting a frequency different from the power frequency into the metal sheath end of the single-core cable by using the excitation source 51>The effective voltage value is +.>Is used to obtain the effective value of the response current by means of the current measuring unit 52, the voltage measuring unit 8>And response voltage effective value +.>。
Step 5: according to the characteristic that the resistance in the impedance does not change along with the frequency, constructing a simultaneous equation to calculate and obtain the resistance of the defect point, and calculating to obtain the C-phase defect point of the grounding end of the metal sheath of the single-core cable from the direct grounding point by utilizing the proportional relation of the resistance and the lengthIs a position of (c). The method comprises the following steps:
（4）/>
=325 m denotes the position of the C-phase defect point of the metal sheath ground of the single-core cable at 325m from the direct ground point.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims (4)

1. A method for positioning the ground defect of a single-core cable metal sheath with one end grounded is characterized by comprising the following steps: the method comprises the following steps:
step 1: acquiring the three-phase circulation of the single-core cable metal sheath, sequentially comparing the three-phase circulation of the single-core cable metal sheath with the capacitance current of the single-core cable metal sheath to obtain a defect phase, and comprising the following steps:
sequentially comparing the three-phase circulation of the single-core cable metal sheath with the single-core cable metal sheath capacitance current, and judging that a certain phase with the circulation being more than or equal to 5 times of the single-core cable metal sheath capacitance current is a defective phase and other non-defective phases are normal phases;
step 2: injecting a first alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable; injecting a second alternating current coupling signal into the metal sheath grounding end of the single-core cable, acquiring a response voltage effective value at the defect phase of the metal sheath insulating end of the single-core cable, and acquiring a response current effective value at the defect phase of the metal sheath grounding end of the single-core cable;
step 3: obtaining a defective phase defective point resistance according to the response current effective value and the response voltage effective value obtained in the step 2, and obtaining the distance between the defective phase defective point of the grounding end of the metal sheath of the single-core cable and the direct grounding point by utilizing the proportional relation of the resistance and the length, wherein the method comprises the following steps:
when the effective value of the response voltage is obtained at the defect phase of the insulating end of the single-core cable metal sheath and is the effective value of the response voltage between the defect phase and the ground of the insulating end of the single-core cable metal sheath:
the following equations are combined:
wherein F1 is the frequency of the injected first AC coupling signal, ZF1 is the impedance of the defect phase section at the frequency F1, F2 is the frequency of the injected second AC coupling signal, ZF2 is the impedance of the defect phase section at the frequency F2, LX is the distance between the defect phase defect point of the grounding end of the single-core cable metal sheath and the direct grounding point, R0 is the resistance of the single-core cable metal sheath, and L0 is the length of the single-core cable metal sheath; UF11 is the effective voltage value of the injected first AC coupling signal, UF12 is the effective value of the response voltage obtained by injecting the first AC coupling signal, IF1 is the effective value of the response current obtained by injecting the first AC coupling signal, UF21 is the effective voltage value of the injected second AC coupling signal, UF22 is the effective value of the response voltage obtained by injecting the second AC coupling signal, and IF2 is the effective value of the response current obtained by injecting the second AC coupling signal;
solving the problem (2) to obtain the distance LX between the defect phase defect point of the grounding end of the metal sheath of the single-core cable and the direct grounding point;
when the effective value of the response voltage is obtained at the defect phase of the insulation end of the single-core cable metal sheath and is the effective value of the response voltage between the defect phase and the normal phase of the insulation end of the single-core cable metal sheath:
the following equations are combined:
wherein F1 is the frequency of the injected first AC coupling signal and F2 is the frequency of the injected second AC coupling signal; ZF1 is the impedance of the defect phase section at the frequency F1, ZF2 is the impedance of the defect phase section at the frequency F2, LX is the distance between the defect point of the defect phase at the grounding end of the metal sheath of the single-core cable and the direct grounding point, R0 is the resistance of the metal sheath of the single-core cable, and L0 is the length of the metal sheath of the single-core cable; UF12 is the effective value of the response voltage obtained by injecting the first AC coupling signal, IF1 is the effective value of the response current obtained by injecting the first AC coupling signal, UF22 is the effective value of the response voltage obtained by injecting the second AC coupling signal, and IF2 is the effective value of the response current obtained by injecting the second AC coupling signal;
solving (3) to obtain the distance LX between the defect phase defect point of the single-core cable metal sheath grounding end and the direct grounding point.
2. The method for positioning the ground fault of the single-ended grounded metal sheath of the single-ended cable according to claim 1, wherein the method comprises the following steps: in step 1, the capacitance current of the metal sheath of the single-core cable is calculated according to the following formula:
IE0＝U0×ω×C (1)
wherein IE0 is the capacitance current of the metal sheath of the single-core cable, U0 is the rated voltage of the metal sheath of the single-core cable, ω is the angular frequency of the metal sheath of the single-core cable, and C is the capacitance between the core of the single-core cable and the metal sheath.
3. The utility model provides a single-end grounded single-core cable metal sheath's ground fault positioner which characterized in that: comprising the following steps: the device comprises an excitation source, a current measuring unit, a current clamp, a coupling clamp, a voltage measuring unit and a calculating unit;
the excitation source is connected with the coupling pliers and is used for injecting an alternating current coupling signal into the grounding end of the single-core cable metal sheath;
the current measuring unit is connected with the current clamp and is used for acquiring three-phase circulation of the metal sheath of the single-core cable and acquiring response current of a defective phase of the grounding end of the metal sheath of the single-core cable when the AC coupling signal is injected into the grounding end of the metal sheath of the single-core cable;
the voltage measurement unit is used for acquiring the response voltage of the defect phase of the insulating end of the metal sheath of the single-core cable when the grounding end of the metal sheath of the single-core cable is injected with an alternating current coupling signal;
the calculating unit is used for judging a defect phase according to the three-phase circulation of the single-core cable metal sheath, obtaining a defect point resistance of the defect phase according to the response current obtained by the current measuring unit and the response voltage obtained by the voltage measuring unit, and obtaining the distance between the defect point of the single-core cable metal sheath grounding end defect phase and the direct grounding point by utilizing the proportional relation of the resistance and the length;
in the calculating unit, the method for judging the defect phase according to the three-phase circulation of the single-core cable metal sheath specifically comprises the following steps:
sequentially comparing the three-phase circulation of the single-core cable metal sheath with the single-core cable metal sheath capacitance current, and judging that a certain phase with the circulation being more than or equal to 5 times of the single-core cable metal sheath capacitance current is a defective phase and other non-defective phases are normal phases;
when the response voltage of the defect phase of the insulating end of the single-core cable metal sheath obtained by the voltage measuring unit is the response voltage between the defect phase of the insulating end of the single-core cable metal sheath and the ground, in the calculating unit, the defect point resistance of the defect phase is obtained according to the response current obtained by the current measuring unit and the response voltage obtained by the voltage measuring unit, and then the distance between the defect point of the defect phase of the grounding end of the single-core cable metal sheath and the direct grounding point is obtained by utilizing the proportional relation between the resistance and the length, and the method specifically comprises the following steps:
the following equations are combined:
wherein F1 is the frequency of the injected first AC coupling signal, ZF1 is the impedance of the defect phase section at the frequency F1, F2 is the frequency of the injected second AC coupling signal, ZF2 is the impedance of the defect phase section at the frequency F2, LX is the distance between the defect phase defect point of the grounding end of the single-core cable metal sheath and the direct grounding point, R0 is the resistance of the single-core cable metal sheath, and L0 is the length of the single-core cable metal sheath; UF11 is the effective voltage value of the injected first AC coupling signal, UF12 is the effective value of the response voltage obtained by injecting the first AC coupling signal, IF1 is the effective value of the response current obtained by injecting the first AC coupling signal, UF21 is the effective voltage value of the injected second AC coupling signal, UF22 is the effective value of the response voltage obtained by injecting the second AC coupling signal, and IF2 is the effective value of the response current obtained by injecting the second AC coupling signal;
solving the problem (2) to obtain the distance LX between the defect phase defect point of the grounding end of the metal sheath of the single-core cable and the direct grounding point;
when the response voltage of the defect phase of the insulating end of the single-core cable metal sheath obtained by the voltage measuring unit is the response voltage between the defect phase and the normal phase of the insulating end of the single-core cable metal sheath, in the calculating unit, the defect point resistance of the defect phase is obtained according to the response current obtained by the current measuring unit and the response voltage obtained by the voltage measuring unit, and then the distance between the defect point of the defect phase of the grounding end of the single-core cable metal sheath and the direct grounding point is obtained by utilizing the proportional relation between the resistance and the length, and the method specifically comprises the following steps:
the following equations are combined:
wherein F1 is the frequency of the injected first AC coupling signal and F2 is the frequency of the injected second AC coupling signal; ZF1 is the impedance of the defect phase section at the frequency F1, ZF2 is the impedance of the defect phase section at the frequency F2, LX is the distance between the defect point of the defect phase at the grounding end of the metal sheath of the single-core cable and the direct grounding point, R0 is the resistance of the metal sheath of the single-core cable, and L0 is the length of the metal sheath of the single-core cable; UF12 is the effective value of the response voltage obtained by injecting the first AC coupling signal, IF1 is the effective value of the response current obtained by injecting the first AC coupling signal, UF22 is the effective value of the response voltage obtained by injecting the second AC coupling signal, and IF2 is the effective value of the response current obtained by injecting the second AC coupling signal;
solving (3) to obtain the distance LX between the defect phase defect point of the single-core cable metal sheath grounding end and the direct grounding point.
4. A single-ended grounded single-core cable metallic sheath ground fault locating device according to claim 3, wherein: the capacitance current of the metal sheath of the single-core cable is calculated according to the following formula:
IE0＝U0×ω×C (1)
wherein IE0 is the capacitance current of the metal sheath of the single-core cable, U0 is the rated voltage of the metal sheath of the single-core cable, ω is the angular frequency of the metal sheath of the single-core cable, and C is the capacitance between the core of the single-core cable and the metal sheath.
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