CN103743997A - Low-voltage cable fault flaw detector - Google Patents

Low-voltage cable fault flaw detector Download PDF

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Publication number
CN103743997A
CN103743997A CN201310716474.1A CN201310716474A CN103743997A CN 103743997 A CN103743997 A CN 103743997A CN 201310716474 A CN201310716474 A CN 201310716474A CN 103743997 A CN103743997 A CN 103743997A
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CN
China
Prior art keywords
low
voltage
voltage cable
cable fault
defectoscope
Prior art date
Application number
CN201310716474.1A
Other languages
Chinese (zh)
Inventor
潘庆
刘秀雄
Original Assignee
柳州职业技术学院
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 柳州职业技术学院 filed Critical 柳州职业技术学院
Priority to CN201310716474.1A priority Critical patent/CN103743997A/en
Publication of CN103743997A publication Critical patent/CN103743997A/en

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Abstract

The invention relates to a low-voltage cable fault flaw detector comprising a voltage regulator, a boosting transformer, a rectifier diode, a filter capacitor, two rheostats and a galvanometer. After alternating-current power supply voltage regulation is carried out, boosting is carried out; rectification, filtering, and voltage stabilizing are carried out and then the currents are divided to the two rheostats; two testing terminals are connected and the galvanometer is connected between the two testing terminals. The two testing terminals are connected to a cable core; and the other end of the cable core is in a short circuit state so as to form a measurement bridge. According to the detector, the current entering the bridge is sufficient and constant, thereby ensuring the testing precision.

Description

A kind of low-voltage cable fault defectoscope

Technical field

The present invention relates to a kind of low-voltage cable fault defectoscope, belong to cable detection technical field.

Background technology

At present, the development of power cable has entered period of expansion at a high speed, has occurred the situation that high pressure, middle pressure, three kinds of grade power cables of low pressure are advanced side by side, and lays environment more complicated, and fault type is more and more, if find not in time to process, consequence is hardly imaginable.And the flaw detection of middle high-pressure electric power cable adopts traveling wave method at present, its principle of work is all to use " wave reflection method principle ", comparative maturity technically, and operation is also not very complicated, has also successfully got rid of most cable faults.

And because the insulating medium internal component of lv power cable is inhomogeneous, cause impedance mismatch, adopt " wave reflection method ", very large by pulse-echo error in practice, particularly low-voltage cable runs into the trouble spot that large area is made moist, cannot form effective reflection, often cause the situations such as pinpoint overlong time and road surface excavation area be excessive, affect greatly work efficiency.

Summary of the invention

The object of the invention is for above-mentioned the deficiencies in the prior art, a kind of fault defectoscope of low-voltage cable is provided.

Technical scheme of the present invention is as follows:

A kind of low-voltage cable fault defectoscope, adopt AC power, it is characterized in that comprising following circuit, first with pressure regulator, adjust voltage, then boost with transformer, with parallel filtering electric capacity after commutation diode cut-off inverse current, one end ground connection, the other end two variable resistors in parallel, each variable resistor connects a test side, connects a galvanometer between two test sides.

Preferred scheme, described variable resistor is variable rheostat.

Preferred scheme, shunt voltage table before boosting with transformer.

Preferred scheme, series current table before two variable resistors in parallel.

Preferred scheme, tandem tap before AC power enters circuit.

Beneficial effect is: this defectoscope, two test sides connect respectively a cable core, and two cable core other end short circuits, can form electric bridge, and to electric bridge, provide enough and constant electric current, when measuring low-voltage cable, can realize good measuring accuracy, unlike " wave reflection method ", can be subject to the impact of insulating medium, cannot to low-voltage cable, measure exactly.

Accompanying drawing explanation

Accompanying drawing 1 is bridge measurement schematic circuit schematic diagram of the present invention.

Accompanying drawing 2 is low-voltage cable fault defectoscope circuit diagram of the present invention.

Accompanying drawing 3 is low-voltage cable fault defectoscope working state circuit schematic diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, principle of the present invention and feature are described, example, only for explaining the present invention, is not intended to limit scope of the present invention.

For singlephase earth fault, the two-phase short circuit and ground fault of low-voltage cable, can adopt " bridge method " as main survey means, effective location is carried out in trouble spot.Because it is not subject to the impact (being the impact of velocity of wave) of insulating medium, whether its principle of work is to utilize the resistance ratio of core to carry out effective location, mate irrelevant with the impedance of low-voltage cable line fault point.

The principle of electric bridge is as accompanying drawing 1, and variable rheostat M is R at a point and first resistance lcable core be connected, variable rheostat N is R at b point and second resistance lcable core be connected, and the other end short circuit of two cables core.There is singlephase earth fault at c point in second cable wherein, second cable is divided into two sections at c o'clock, and resistance is respectively R xand R l-R x.Utilize direct supply DC to apply DC voltage at variable rheostat M with one end that variable rheostat N is connected, other end ground connection, adjusts the resistance of M and N, and the upper no current of galvanometer G connecting is passed through, Ze Yi road electric current after M through first cable core R lafter, by short circuit point, enter second cable core, pass through R l-R xafter at the earth point c of cable core, see through insulation course and enter the earth, get back to the negative pole of direct supply DC; Another road electric current, after N, enters second cable core, passes through resistance R xafter, at c place, see through insulation course and enter the earth, get back to the negative pole of direct supply DC, the summation R of insulation course and ground resistance grepresent.

Electric current I g by electric bridge galvanometer G is zero, so the resistance ratio of M and N equals 2R l-R xwith R xratio equate, can extrapolate R accordingly xwith R lratio, thereby estimate the position of Method of Cable Trouble Point.

First cable core and second cable core are exchanged, then measured once, the result drawing equates or approaches, illustrates that test result is correct.

R gsize and the resistance in bridge irrelevant, but its size has determined to enter the size of electric current in bridge, the precision of impact test.

Enough and constant for guaranteeing the electric current entering in bridge, to guarantee the precision of test.In " constant current " this point, make an effort, no matter i.e. faulty insulator resistance height no matter, the electric current that can guarantee to enter in bridge is enough and constant for this reason.

So the circuit of the application's low-voltage cable defectoscope is as shown in Figure 2:

AC power AC, through K switch access, adopt pressure regulator TB to adjust voltage, and the transformer SB that adopts voltage table to measure output voltage, process no-load voltage ratio 200V/800V boosts, with commutation diode Z, ends inverse current, after parallel filtering capacitor C, to electric bridge, power, one end ground connection, the other end is measured output current with milliammeter, and the first via connects test side a after a variable rheostat M; Whether the second tunnel connects another test side b after a variable rheostat N, connects a galvanometer G between two test sides, in order to detect, have electric current to pass through electric bridge.

The circuit of duty is as shown in Figure 3:

A good core and a bad core are carried out to reliable short circuit, and the cross section of shorting stub should be not less than the sectional area of cable core, and the other end is connected respectively on test lead a and test lead b; At c point, there is singlephase earth fault in bad core.When if the heart yearn of three phase lines of cable all has fault, can be by the identical cable core of other areas the loop as bridging line.

By accompanying drawing 3, carry out electric bridge test connection, require each tie point firm.The test lead of all test use should be short and thick, and lead-in wire is used 50 square millimeters and above multiply annealed copper wire, and the terminal compression joint at two soldering and sealing, to reduce the error that in test, lead-in wire brings.

Regulate variable rheostat M and variable rheostat N, until the electric current I g of galvanometer G is zero.The all switches that disconnect double bridge, record resistance box reading.

Step-down, power failure, electric discharge, exchange two p-wires, by opposition method, carries out test operation one time again, records the reading of resistance box.

The data of positive and negative two kinds of connections being calculated by formula, averaged, is pre-determined bit length.

Compared with prior art, this bridge type low-voltage cable fault defectoscope, the electric current that can guarantee to enter electric bridge is enough and constant, thereby guarantees the precision of test, is not subject to the impact of insulating medium, utilizes the resistance ratio of core to carry out effective location, and result is accurate.

The present invention can summarize with other the concrete form without prejudice to spirit of the present invention or principal character.Therefore,, in the implication suitable with claims of the present invention and any change in scope, all should think to be included in the scope of claims.

Claims (5)

1. a low-voltage cable fault defectoscope, adopt AC power, it is characterized in that comprising following circuit, first with pressure regulator, adjust voltage, then boost with transformer, with parallel filtering electric capacity after commutation diode cut-off inverse current, one end ground connection, the other end two variable resistors in parallel, each variable resistor connects a test side, connects a galvanometer between two test sides.
2. low-voltage cable fault defectoscope according to claim 1, is characterized in that, described variable resistor is variable rheostat.
3. low-voltage cable fault defectoscope according to claim 1, is characterized in that, shunt voltage table before boosting with transformer.
4. low-voltage cable fault defectoscope according to claim 1, is characterized in that, series current table before two variable resistors in parallel.
5. low-voltage cable fault defectoscope according to claim 1, is characterized in that tandem tap before AC power enters circuit.
CN201310716474.1A 2013-12-23 2013-12-23 Low-voltage cable fault flaw detector CN103743997A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201310716474.1A CN103743997A (en) 2013-12-23 2013-12-23 Low-voltage cable fault flaw detector

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201310716474.1A CN103743997A (en) 2013-12-23 2013-12-23 Low-voltage cable fault flaw detector

Publications (1)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105891675A (en) * 2016-04-11 2016-08-24 中国石油大学(华东) Method of positioning insulated fault point of submersible oil cable in twice Wheatstone bridge method

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB484230A (en) * 1936-01-11 1938-05-03 Siemens Ag Improvements in and relating to circuit arrangements for electric testing or measuring appliances
JPS60108763A (en) * 1983-11-18 1985-06-14 Nippon Telegr & Teleph Corp <Ntt> Fault position measuring system for cable core
CN2214002Y (en) * 1994-11-24 1995-11-29 沈阳铁路分局沈阳给水电力段 Trouble surveying instrument of low-voltage power cable
CN102096023A (en) * 2010-12-17 2011-06-15 西安四方机电有限责任公司 Device and method for testing power cable fault
CN202649380U (en) * 2012-05-30 2013-01-02 上海电力学院 Digital cable insulation fault automatic locator

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB484230A (en) * 1936-01-11 1938-05-03 Siemens Ag Improvements in and relating to circuit arrangements for electric testing or measuring appliances
JPS60108763A (en) * 1983-11-18 1985-06-14 Nippon Telegr & Teleph Corp <Ntt> Fault position measuring system for cable core
CN2214002Y (en) * 1994-11-24 1995-11-29 沈阳铁路分局沈阳给水电力段 Trouble surveying instrument of low-voltage power cable
CN102096023A (en) * 2010-12-17 2011-06-15 西安四方机电有限责任公司 Device and method for testing power cable fault
CN202649380U (en) * 2012-05-30 2013-01-02 上海电力学院 Digital cable insulation fault automatic locator

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
董爱华 等: "煤矿井下动力电缆故障点检测的研究", 《煤炭科学技术》 *
邢海瀛 等: "基于倒置电桥法的电力电缆故障定位", 《电力自动化设备》 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105891675A (en) * 2016-04-11 2016-08-24 中国石油大学(华东) Method of positioning insulated fault point of submersible oil cable in twice Wheatstone bridge method

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Application publication date: 20140423

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