CN103487727B - A kind of high voltage power cable oversheath On-line Fault localization method - Google Patents

A kind of high voltage power cable oversheath On-line Fault localization method Download PDF

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CN103487727B
CN103487727B CN201310248193.8A CN201310248193A CN103487727B CN 103487727 B CN103487727 B CN 103487727B CN 201310248193 A CN201310248193 A CN 201310248193A CN 103487727 B CN103487727 B CN 103487727B
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cable
metal sheath
signal
frequency
phase
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CN103487727A (en
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罗致远
詹威鹏
陈腾彪
吴彦志
周庆坚
江克宜
邬韬
魏前虎
李高峰
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Shenzhen Power Supply Bureau Co Ltd
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Shenzhen Power Supply Bureau Co Ltd
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Abstract

A kind of high voltage power cable oversheath On-line Fault localization method, high-frequency square-wave signal sends from detecting unit, be transferred on metal electrode by concentric conductor, then crossing electric capacity effect is coupled on cable metal sheath, because cable metal sheath two-terminal-grounding state, so high-frequency pulse signal forms a loop by cable metal sheath and the earth, be enclosed within the High Frequency Current Sensor on cross interconnected line, as the sensing equipment of couples high frequency pulse signal, be coupled to high-frequency pulse signal, then be transferred in detecting unit by high-frequency coaxial cable and carry out collection analysis, data after analysis pass through wireless transmission line, be sent in background server, store, display.<pb pnum="1" />

Description

A kind of high voltage power cable oversheath On-line Fault localization method
Technical field
The invention belongs to the on-line monitoring technique field of power equipment, be specifically related to a kind of high voltage power cable oversheath On-line Fault localization method.
Background technology
110kV and above power cable are generally the design of single core, and in order to eliminate that induced voltage on cable metal sheath is too high, induction current that is that bring is excessive, cause cable jacket to generate heat serious phenomenon.When long range propagation, the general cross interconnected transposition form of threephase cable protective metal shell that adopts is implemented, and utilizes the phase 120 ° of three-phase offset or reduce induced voltage on sheath, avoids oversheath insulation breakdown, reduce ground loop flow valuve.Cable jacket is the protection of power cable outermost layer, is the protection of the ground floor of cable, is also the most easily by the position of outside destroy, so be very important to the malfunction monitoring of power cable oversheath, particularly for plow-in cable.Because a variety of causes oversheath suffers the direct earth point of damaged rear formation, cause the multipoint earth faults of cable, thus cause the electric current of protective metal shell to increase, electric cable heating directly causes cable load to reduce, also the aging of major insulation can be caused, can cause cable breakdown time serious, the present invention is a kind of method positioned in order to this type of fault of Timeliness coverage and to fault.
Retrieval finds, for power cable oversheath On-line Fault monitoring and localization method fewer, and for the monitoring of the major insulation of power cable and localization of fault many, in " for electricity consumption " magazine, some method of testings are given to single-core power cables oversheath fault in " high voltage single-core cable oversheath fault looks into survey and method for repairing and mending " of the 29th volume the 2nd phase, wherein also list several field failure localization method, as bridge balance method, constant current source firing process and pulse positioning method when three-phase has fault, these are all the ripe methods being applied to scene.But these methods are all off-line tests, are not suitable for on-line testing, search in other documents and mention method, spark experimental method, although step voltage method is live testing one method, is a kind of live testing instrument after all, needs personnel to operate.
Summary of the invention
In order to overcome the defect of above-mentioned prior art, the object of the present invention is to provide a kind of high voltage power cable oversheath On-line Fault localization method, solve a difficult problem of carrying out tuning on-line under the breakage of direct burial single core cable oversheath causes ground fault condition, without the need to the on-the-spot manual operation of complexity, only need Long-distance Control positioning system, software algorithm just can be utilized to orient the position of sheath breakage.
In order to achieve the above object, technical scheme of the present invention is:
A kind of high voltage power cable oversheath On-line Fault localization method, comprises the following steps:
Step one, a complete cross interconnected section of circuit is divided into three sections, every segment length is at 500 meters, every section has A, B, C tri-phase composition, its core 1 is all connected, section joint, every two ends cable cover(ing) 2 disconnects, and carry out the cross interconnected of out of phase in joint by cross interconnected line 7, cross interconnected line 7 is socketed with High Frequency Current Sensor 5, cross interconnected mode is: first paragraph A phase metal sheath layer is connected to B phase second segment metal sheath layer, first paragraph B phase metal sheath layer is connected to C phase second segment metal sheath layer, first paragraph C phase metal sheath layer is connected to A phase second segment metal sheath layer, second group of joint, carry out cross interconnected again, finally, three sections of cables realize the direct ground connection in two ends by the direct ground wire 8 at two ends, the metal electrode 4 being pasted onto cable cover(ing) 2 top layer is connected with detecting unit 9 by concentric conductor 3, High Frequency Current Sensor 5 is connected with detecting unit 9 by coaxial wire 6, wireless transmission between detecting unit 9 and background server 10,
Step 2, high-frequency square-wave signal sends from detecting unit 9, be transferred on metal electrode 4 by concentric conductor 3, by on electric capacity effect coupling cable protective metal shell 2, signal becomes high-frequency impulse type signal, because screen layer two ends are all ground states, so signal can transmit along cable toward two ends, the equiva lent impedance on signal amplitude and electrode both sides is inversely proportional to, now high-frequency electrical pulses flow sensor 5 is coupled to pulse signal, now signal is former ripple signal, when cable metal sheath 2 has breakage failure, because cable is plow-in cable, cable metal sheath 2 can be caused to contact with soil, cause micro-ground connection, equivalence can regard screen layer and the resistance be greatly connected as, the size of resistance embodies the order of severity of earth fault, it is not match point herein, so high-frequency signal can produce shunting herein, and have portion of energy to reflect, when high-frequency impulse amplitude is enough large, its reflection wave can be transferred to another one ground connection place by cross interconnected, now in High Frequency Current Sensor 5, be coupled out reflection wave signal, high-frequency impulse is in earth fault, produce reflection wave and circuit shunting ripple, former ripple and reflection wave all can be coupled in monitoring means 9 by high-frequency impulse sensor 5, the mistiming of former ripple and reflection wave is calculated in monitoring means 9, utilize dipulse time difference to extrapolate position of failure point,
Concrete method for calculating and locating, if pulse signal is v in the transmission speed of cable, the reflection wave mistiming of former ripple and trouble spot is △ t, and following formula just can calculate trouble spot to high-frequency impulse sensor distance x:
x = 1 2 v&Delta;t
The speed v of the ripple transmission in cable conductor can test out in advance, use the cable of a known length again, access a pulse in end, then do receiving end in end, test out the mistiming of former ripple and reflection wave, just can calculate efferent echo speed in the cable.
The present invention is first toward between the metal sheath layer and the earth at single core cable non_direct ground end connector place, and access period high-frequency pulse signal, according to power cable connected mode, signal can be propagated along cable metal sheath, and final sum the earth forms a loop.System, by the high-frequency pulse signal on High Frequency Current Sensor coupling circuit, utilizes the former ripple of signal and calculates location of fault in the reflection wave mistiming of trouble spot.
The present invention is first toward between the metal sheath layer and the earth at single core cable non_direct ground end connector place, and access period high-frequency pulse signal, according to power cable connected mode, signal can be propagated along cable metal sheath, and final sum the earth forms a loop.System, by the high-frequency pulse signal on High Frequency Current Sensor coupling circuit, utilizes the former ripple of signal and calculates location of fault in the reflection wave mistiming of trouble spot.
Accompanying drawing explanation
Fig. 1 is single core cable cross interconnected situation lower jacket fault location system figure.
Fig. 2 is A phase power cable metal sheath earth fault tuning on-line stream of pulses schematic diagram.
Fig. 3 is power cable metal sheath localization of fault equivalent diagram.
Fig. 4 is power cable metal sheath localization of fault computing method.
Fig. 5 is power cable metal sheath fault location system raw data display interface.
Fig. 6 is power cable metal sheath earth fault tuning on-line system diagram.
Embodiment
Below in conjunction with accompanying drawing, work of the present invention is described in detail.
A kind of high voltage power cable oversheath On-line Fault localization method, comprises the following steps:
Step one, with reference to Fig. 1, a complete cross interconnected section of circuit is divided into three sections, every segment length is at 500 meters, every section has A, B, C tri-phase composition, its core 1 is all connected, section joint, every two ends cable cover(ing) 2 disconnects, and carry out the cross interconnected of out of phase in joint by cross interconnected line 7, cross interconnected line 7 is socketed with High Frequency Current Sensor 5, cross interconnected mode is: first paragraph A phase metal sheath layer is connected to B phase second segment metal sheath layer, first paragraph B phase metal sheath layer is connected to C phase second segment metal sheath layer, first paragraph C phase metal sheath layer is connected to A phase second segment metal sheath layer, second group of joint, carry out cross interconnected again, finally, three sections of cables realize the direct ground connection in two ends by the direct ground wire 8 at two ends, the metal electrode 4 being pasted onto cable cover(ing) 2 top layer is connected with detecting unit 9 by concentric conductor 3, High Frequency Current Sensor 5 is connected with detecting unit 9 by coaxial wire 6, wireless transmission between detecting unit 9 and background server 10,
Step 2, with reference to Fig. 2, high-frequency square-wave signal sends from detecting unit 9, be transferred on metal electrode 4 by concentric conductor 3, by on electric capacity effect coupling cable protective metal shell 2, signal becomes high-frequency impulse type signal, because screen layer two ends are all ground states, so signal can transmit along cable toward two ends, the equiva lent impedance on signal amplitude and electrode both sides is inversely proportional to, now high-frequency electrical pulses flow sensor 5 is coupled to pulse signal, now signal is former ripple signal, when cable metal sheath 2 has breakage failure, because cable is plow-in cable, cable metal sheath 2 can be caused to contact with soil, cause micro-ground connection, equivalence can regard screen layer and the resistance be greatly connected as, the size of resistance embodies the order of severity of earth fault, it is not match point herein, so high-frequency signal can produce shunting herein, and have portion of energy to reflect, when high-frequency impulse width is enough worth enough large, its reflection wave can be transferred to another one ground connection place by cross interconnected, now in High Frequency Current Sensor 5, be coupled out reflection wave signal, concrete location algorithm is exactly realize mistiming of apply pulse, specific implementation is illustrated in fig. 3 shown below: high-frequency impulse is in earth fault, produce reflection wave and circuit shunting ripple, former ripple and reflection wave all can be coupled in monitoring means 9 by high-frequency impulse sensor 5, the mistiming of former ripple and reflection wave is calculated in monitoring means 9, utilize dipulse time difference to extrapolate position of failure point.
Concrete method for calculating and locating, as shown in Figure 4, if pulse signal is v in the transmission speed of cable, the reflection wave mistiming of former ripple and trouble spot is △ t, and following formula just can calculate trouble spot to high-frequency impulse sensor distance x:
x = 1 2 v&Delta;t
Because the speed v of the ripple transmission in cable conductor can test out in advance, test mode is fairly simple, with the cable of a known length, a pulse is accessed in end, then receiving end is done in end, test out the mistiming of former ripple and reflection wave, just can calculate efferent echo speed in the cable.
Need explanation two point: the locator meams first accessing signal electrode 4 liang of end cables is identical, will cause and determine distance, but the uncertain reflection wave being that section of cable and causing, judge at that section about trouble spot, fairly simple, only need to test current value and direct ground current value on the cross interconnected line of adjacent two sections; Secondly all may reflect at the discontinuous place of circuit, comprise cross interconnected section of junction and two-terminal-grounding place part, reflection is herein all fixing known reflection, cable is done first time test time, just find this reflection, and note down, when long-term on-line operation, if find that there is new reflection spot, should be that cable jacket fault causes.
High-frequency square-wave signal sends from detecting unit 9, be transferred on metal electrode 4 by concentric conductor 3, then crossing electric capacity effect is coupled on cable metal sheath 2, because cable metal sheath two-terminal-grounding state, so high-frequency pulse signal forms a loop by cable metal sheath 2 and the earth, be enclosed within the High Frequency Current Sensor 5 on cross interconnected line 7, as the sensing equipment of couples high frequency pulse signal, be coupled to high-frequency pulse signal, then be transferred in detecting unit 9 by high-frequency coaxial cable 6 and carry out collection analysis, data after analysis pass through wireless transmission line, be sent in background server 10, store, display.
Laboratory proofing:
Testing laboratory of the present invention checking, at use for laboratory three 500 meters 50-3 model coaxial wire simulation power cables, set up into the structure of Fig. 2, in first paragraph and second segment intersection the surface of electrode paste at cable, the screen layer between two ends is connected with plain conductor, the core part sky of every section connects, and High Frequency Current Sensor is stuck on the connecting line of first paragraph and second segment, and two ends are at different local access the earth.Connect detecting unit and the background data server part of positioning system, first square-wave signal is input on electrode, gather the signal of High Frequency Current Sensor simultaneously, native system sampling rate is 100MS/s, can gather complete pulse waveform, comprises former ripple and reflection wave, gather display as shown in Figure 5, whole continuous sampling length is 20ms, and the raw data of sampling shows, and former ripple and reflection wave can show in time domain viewing area.A 1K Ω resistance is connected over the ground at 315 of second segment meters of during test, analogue ground fault, after operational system carries out gathering and analyze, waveform as shown in Figure 6, setting velocity of wave is that v=169m/us is calculated by tester, software can measure former ripple and reflection wave time △ t=3.72us, and can to calculate range sensor position, trouble spot be thus 315.485 meters, match with the defect preset, show that system precision in test is comparatively accurate, due to on-line operation power cable environment more complicated, so system must add some jamproof means, comprise: hardware filtering, the means such as software filtering and wavelet filtering, the various disturbing factor of filtering Site Detection.

Claims (2)

1. a high voltage power cable oversheath On-line Fault localization method, is characterized in that, comprise the following steps:
Step one, a complete cross interconnected section of circuit is divided into three sections, every segment length is at 500 meters, every section all by A, B, C tri-phase composition, its core (1) is all connected, section joint cable metal sheath, every two ends (2) disconnect, and carry out the cross interconnected of out of phase in joint by cross interconnected line (7), cross interconnected line (7) is socketed with high-frequency electrical pulses flow sensor (5), cross interconnected mode is: first paragraph A phase metal sheath layer is connected to B phase second segment metal sheath layer, first paragraph B phase metal sheath layer is connected to C phase second segment metal sheath layer, first paragraph C phase metal sheath layer is connected to A phase second segment metal sheath layer, second group of joint, carry out cross interconnected again, finally, three sections of cables realize the direct ground connection in two ends by the direct ground wire (8) at two ends, the metal electrode (4) being pasted onto cable metal sheath (2) top layer is connected with detecting unit (9) by concentric conductor (3), high-frequency electrical pulses flow sensor (5) is connected with detecting unit (9) by coaxial wire (6), wireless transmission between detecting unit (9) and background server (10),
Step 2, high-frequency square-wave signal sends from detecting unit (9), be transferred on metal electrode (4) by concentric conductor (3), by on electric capacity effect coupling cable protective metal shell (2), signal becomes high-frequency impulse type signal, because screen layer two ends are all ground states, so signal can transmit along cable toward two ends, the equiva lent impedance on signal amplitude and electrode both sides is inversely proportional to, now high-frequency electrical pulses flow sensor (5) is coupled to pulse signal, now signal is former ripple signal, when cable metal sheath (2) has breakage failure, because cable is plow-in cable, cable metal sheath (2) can be caused to contact with soil, cause micro-ground connection, the resistance that screen layer is connected with the earth is regarded in equivalence as, the size of resistance embodies the order of severity of earth fault, it is not match point herein, so high-frequency signal can produce shunting herein, and have portion of energy to reflect, when high-frequency impulse amplitude is enough large, its reflection wave can be transferred to another one ground connection place by cross interconnected, now in high-frequency electrical pulses flow sensor (5), be coupled out reflection wave signal, high-frequency impulse is in earth fault, produce reflection wave and circuit shunting ripple, former ripple and reflection wave all can be coupled in detecting unit (9) by high-frequency electrical pulses flow sensor (5), the mistiming of former ripple and reflection wave is calculated in detecting unit (9), utilize dipulse time difference to extrapolate position of failure point.
2. a kind of high voltage power cable oversheath On-line Fault localization method according to claim 1, it is characterized in that, utilize dipulse time difference to extrapolate position of failure point, concrete method for calculating and locating is as follows: pulse signal is v in the transmission speed of cable, the reflection wave mistiming of former ripple and trouble spot is △ t, calculates trouble spot as follows to high-frequency impulse sensor distance x:
x = 1 2 v &Delta; t
With the cable of a known length, access a pulse in end, then using this end as receiving end, test out the mistiming of former ripple and reflection wave, calculating pulse signal in the transmission speed of cable is v.
CN201310248193.8A 2013-06-21 2013-06-21 A kind of high voltage power cable oversheath On-line Fault localization method Active CN103487727B (en)

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