CN102937687B - Method for distinguishing disconnection fault and grounding fault during grounding of neutral point through small resistor - Google Patents
Method for distinguishing disconnection fault and grounding fault during grounding of neutral point through small resistor Download PDFInfo
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- CN102937687B CN102937687B CN201210417797.6A CN201210417797A CN102937687B CN 102937687 B CN102937687 B CN 102937687B CN 201210417797 A CN201210417797 A CN 201210417797A CN 102937687 B CN102937687 B CN 102937687B
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- 230000001264 neutralization Effects 0.000 title claims abstract description 20
- 238000001514 detection method Methods 0.000 claims description 3
- 230000004069 differentiation Effects 0.000 claims description 3
- 238000003379 elimination reaction Methods 0.000 abstract 1
- 230000037242 Cmax Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000005611 electricity Effects 0.000 description 2
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Abstract
The invention discloses a method for distinguishing a disconnection fault and a grounding fault during grounding of a neutral point through a small resistor. When the neutral point of a transformer is grounded through the small resistor Ro, an automatic power distribution system is arranged on a transformer substation; the automatic power distribution system is provided with a zero sequence over-current protection module; a monitoring terminal is arranged on each of switches in a line; in the disconnection fault and the grounding fault, a three-phase current is unbalanced, and a three-phase voltage is unbalanced; in the disconnection fault, the three-phase voltage on a power side is normal, and the disconnection-phase voltage on the non power side is similar to zero; in the grounding fault, the grounding-phase voltage is similar to zero, and the non grounding-phase voltage is increased to linear voltage; and moreover, the switches through which the total zero sequence current flows and the switches through which the total zero sequence current does not flow are monitored, and the monitoring terminals of the switches transmit information to the automatic power distribution system DA, so that the type of the fault and the fault generation region can be determined. By utilizing the method, the disconnection fault and the grounding fault can be distinguished; correct beneficial information can be supplied for the elimination of the fault; and accident processing is facilitated.
Description
Technical field
The present invention relates to the differentiating method of main transformer neutral point disconnection fault and earth fault when low resistance grounding in 10KV system.
Background technology
Urban distribution network is after a large amount of use underground cable, how earth fault is eliminated during ground connection, a kind of method of domestic and international employing makes Neutral Point Through Low Resistance mode, see the technical journal " for electricity consumption " that urban electricity supply Professional Committee of CSEE sponsors, 3rd phase in 1997, Wang Yiyu work " Urban Distribution Network Neutral Grounding lecture ", calendar year 2001 the 1st phase Xue Jin, Chen Qinsheng work is " to France, the introduction that Germany and Britain's part electrical network are investigated ", but Neutral Point Through Low Resistance mode, single-phase short circuit is formed when a phase ground connection, therefore zero sequence excess current protective device to be installed, make switch trip, excision ground short circuit section, want ring network power supply to improve power supply reliability simultaneously, in addition, domesticly embark power distribution automation, install block switch on the line, circuit is divided into several section, monitor terminal installed by each switch, each terminal is installed and is connected into the wiring of zero sequence pass filter with three current transformers, or with zero sequence current mutual inductor, be used for detecting zero-sequence current, switch ends is equipped with threephase potential transformer, be used for measuring voltage switch accumulator used is charged, wire ground capacitance is distributed, represent by lumped capacitance, transformer station's installing electrical power distribution automatization system, realize power distribution automation function, Neutral Point Through Low Resistance mode, when there is disconnection fault, produce three-phase current unbalance, imbalance of three-phase voltage, when there is earth fault, also three-phase current unbalance can be produced, imbalance of three-phase voltage situation, how distinguish this two kinds of faults during fault, not yet there is solution.
Summary of the invention
In view of this, technical matters to be solved by this invention is: a kind of method of disconnection fault and earth fault when providing feature of the imbalance of three-phase voltage utilizing the feature of the three-phase current unbalance produced when broken string, earth fault and fault two ends to produce to distinguish the Neutral Point Through Low Resistance of disconnection fault and earth fault.
In order to achieve the above object, the present invention adopts following technical scheme to realize:
A differentiating method for disconnection fault and earth fault during Neutral Point Through Low Resistance, transformer neutral point is through small resistor R
oduring earthing mode, wherein: transformer station is equiped with electrical power distribution automatization system, described electrical power distribution automatization system has zero sequence excess current protection module, in circuit, each switch is all equipped with monitor terminal, described monitor terminal measures zero-sequence current, capacitive earth current, and monitor the switch that zero-sequence current flows through and the switch do not flow through, and information is sent to described electrical power distribution automatization system, when there is disconnection fault and earth fault, three-phase current unbalance, imbalance of three-phase voltage, during disconnection fault, mains side three-phase voltage is normal, but not mains side broken string phase voltage approximate zero, Earth Phase voltage approximate zero during earth fault, ungrounded phase voltage raises proximal line voltage, simultaneously, by monitoring the switch that total zero-sequence current flows through and the switch do not flow through, above-mentioned information is sent to electrical power distribution automatization system DA by monitoring switch terminal, can sentence and know which kind of fault and fault generation section.
1, three-phase current unbalance:
(1) disconnection fault three-phase current unbalance: due to a phase broken string, the mains side direction at broken string place, broken string phase current is little, all the other biphase currents are greater than phase current and approximately equal, non-power side to, broken string phase current approximate zero, all the other biphase currents are same as mains side directional current
(2) earth fault three-phase current unbalance: during a phase ground connection, mains side direction, ground connection place, Earth Phase single-phase short circuit, short-circuit current is large, about hundreds of to thousands of peace, and another two-phase is normal load electric current, non-power side to, Earth Phase is approximately zero due to short-circuit current, and another two-phase is still load current.
2, imbalance of three-phase voltage:
(1) disconnection fault imbalance of three-phase voltage: due to a phase broken string, the mains side direction at broken string place, three-phase all has normal voltage, non-power side to, broken string phase voltage approximate zero, another two-phase still has normal voltage.
(2) earth fault imbalance of three-phase voltage: during a phase ground connection, Earth Phase voltage approximate zero in ground connection section, but not Earth Phase voltage is increased to proximal line voltage.
3, fault section:
(1) disconnection fault section: when there is disconnection fault, three-phase current unbalance, detects the voltage of each switch, and information is sent to electrical power distribution automatization system, thus determines disconnection fault section.
(2) earth fault section: when there is earth fault, produce total zero-sequence current I
o ∑, I
o ∑flow through some switches, also do not flow through some switches, above-mentioned information is sent to electrical power distribution automatization system by the monitor terminal of switch, thus determines ground connection section.
4, the differentiation of disconnection fault and earth fault:
Detect voltage during fault, if mains side direction, fault place three-phase voltage is normal, non-power side, to a phase voltage approximate zero, is disconnection fault, if fault section one phase voltage approximate zero, another two phase voltage proximal line voltages are earth fault.
As shown from the above technical solution, the invention has the beneficial effects as follows:
Compared to existing technology, during Neutral Point Through Low Resistance, break down, disconnection fault or earth fault can be distinguished, providing correct advantageous information for eliminating fault, being convenient to accident treatment.Specifically, the present invention by being equiped with electrical power distribution automatization system in transformer station, and each switch is all equipped with monitor terminal in the line, differentiating method according to fault can distinguish earth fault and disconnection fault easily, and recognize rapidly the position that fault produces, be convenient to the promptly and accurately process of accident, avoid fault spread.
Accompanying drawing explanation
Electric current, V diagram when Fig. 1 is disconnection fault of the present invention.
Electric current, V diagram when Fig. 2 is earth fault of the present invention.
Fig. 3 is that disconnection fault of the present invention and earth fault distinguish schematic diagram.
Embodiment
In order to make those skilled in the art can further understand feature of the present invention and technology contents, refer to following detailed description for the present invention and accompanying drawing.
Refer to shown in Fig. 1, B is main-transformer, and O is main transformer neutral point, R
obe neutral point small resistor, CK is transformer station's outlet switch, and 1FK ~ 3FK is block switch on circuit, and LL is interconnection switch on circuit, and DA is the electrical power distribution automatization system be loaded in transformer station, as the 3rd section K
1when A phase in place breaks, mains side A phase current reduces, I
amin< I
f(I
ffor load current time normal), but not broken string is due to the increase of two-phase operation electric current, I
bmax≈ I
cmax> I
f, broken string place non-electrical source, because A phase breaks I
a≈ 0, and all the other two-phases are still I
bmax, I
cmax, like this, three-phase current unbalance, produces zero-sequence current I
o, can be used for starting and detect voltage, during a phase broken string, mains side three-phase voltage U
a, U
b, U
cnormally, the phase voltage U but not mains side breaks
a≈ 0, non-broken string phase voltage U
b, U
cbe still normal phase voltage, therefore imbalance of three-phase voltage.
Refer to shown in Fig. 2, symbol B, O, R
o, CK, 1FK ~ 3FK, LL and DA illustrate with Fig. 1, as the 3rd section K
2during place's A phase ground connection, form single-phase short circuit, produce single-phase short circuit current
another biphase current I
b, I
cfor load current, three-phase current unbalance produces zero-sequence current I
o, each switch of a phase ground connection produces capacitance current again, over the ground as I
01, I
01.1~ I
01.3, I
01.c, total capacitance electric current I
c, these two kinds of electric currents produce again total zero-sequence current
non-electrical source, due to the short circuit of A phase, A phase current becomes I
a≈ 0, and another two-phase I
b, I
cbe still load current, during a phase ground connection, imbalance of three-phase voltage, Earth Phase U
a≈ 0, ungrounded phase voltage is increased to proximal line voltage, U
b=1.63 ~ 1.73U
x(U
xfor phase voltage), U
c=2.8 ~ 1.73U
x.
Refer to shown in Fig. 3, symbol B, O, R
o, CK, 1FK ~ 3FK, LL and DA illustrate with Fig. 1, as the 3rd section K
1or K
2when place breaks down, as disconnection fault, electric current, voltage are as numeral in square frame; As earth fault, electric current, voltage are without numeral in square frame, the differentiation of disconnection fault and earth fault is the both sides voltage of fault section, during disconnection fault, mains side three-phase voltage is normal, but not mains side broken string phase voltage approximate zero, Earth Phase voltage approximate zero during earth fault, ungrounded phase voltage raises proximal line voltage.
Embodiment:
If circuit the 3rd section breaks down, as K
1a phase in place breaks, and mains side (2FK, 1FK, CK) A phase current reduces, I
amin< I
f(I
ffor load current), but not broken string is due to two-phase operation, electric current increases, I
bmax≈ I
cmax> I
f, non-electrical source (3FK, LL), because A phase breaks I
a≈ 0, and all the other two-phases are still I
bmax, I
cmax, like this, three-phase current unbalance, produces zero-sequence current I
o, during a phase broken string, mains side three-phase voltage U
a, U
b, U
cnormally, non-electrical source broken string phase voltage U
a≈ 0, non-broken string phase voltage U
b, U
cbe still normal phase voltage, therefore imbalance of three-phase voltage.Above-mentioned information is sent to electrical power distribution automatization system DA by monitoring switch terminal, can sentence the section knowing that disconnection fault and fault occur, in order to detect voltage, and the I that also can produce with three-phase current unbalance
o, start detection voltage, as K
2during place's A phase ground connection, form single-phase short circuit, single-phase short circuit current
can reach hundreds of to thousands of peace, another biphase current I
b, I
cfor load current, three-phase current unbalance produces zero-sequence current I
o, each Switch Controller ground of phase ground connection produces capacitance current, as I
01, I
01.1~ I
01.3, I
01.c, total capacitance electric current I
c, above two kinds of electric currents produce again total zero-sequence current
non-electrical source, due to the short circuit of A phase, A phase current becomes I
a≈ 0, and another two-phase I
b, I
cbe still load current, during a phase ground connection, imbalance of three-phase voltage, Earth Phase U
a≈ 0, ungrounded phase voltage raises proximal line voltage, U
b=1.63 ~ 1.73U
x, U
c=2.8 ~ 1.73U
x.Total zero-sequence current I
o ∑flow through CK, 1FK, 2FK, R
o, do not flow through 3FK, LL, above-mentioned information is sent to electrical power distribution automatization system DA by monitoring switch terminal, can sentence and know earth fault and fault generation section, during Neutral Point Through Low Resistance, zero sequence excess current protective device is housed, work as I
o ∑>=I
0.dztime, action in zero sequence excess current protection 0.6S, makes outlet switch CK trip, cutting off ground current, in order to detect voltage in 0.6S, also directly can use I
o ∑start and detect voltage.
Break down when causing three-phase current unbalance, detect voltage to distinguish broken string or earth fault, if detect, mains side three-phase voltage is normal, non-electrical source one phase voltage approximate zero, this fault is disconnection fault, if a phase voltage approximate zero detected, another two phase voltages raise proximal line voltage, and this fault is earth fault.
But the foregoing is only better possible embodiments of the present invention, and be not used to limit to the scope of the claims of the present invention, therefore the equivalent structure change that all utilizations instructions of the present invention and accompanying drawing content are done, all in like manner within the scope of the present invention.
Claims (3)
1. the differentiating method of disconnection fault and earth fault during Neutral Point Through Low Resistance, transformer neutral point is through small resistor R
oduring earthing mode, it is characterized in that: transformer station is equiped with electrical power distribution automatization system, described electrical power distribution automatization system has zero sequence excess current protection module, in circuit, each switch is all equipped with monitor terminal, described monitor terminal measures zero-sequence current, capacitive earth current, and monitor the switch that zero-sequence current flows through and the switch do not flow through, and information is sent to described electrical power distribution automatization system, when there is disconnection fault and earth fault, three-phase current unbalance, imbalance of three-phase voltage, during disconnection fault, mains side three-phase voltage is normal, but not mains side broken string phase voltage approximate zero, Earth Phase voltage approximate zero during earth fault, ungrounded phase voltage raises proximal line voltage, simultaneously, by monitoring the switch that total zero-sequence current flows through and the switch do not flow through, above-mentioned information is sent to electrical power distribution automatization system DA by monitoring switch terminal, when there is disconnection fault, broken string phase mains side electric current < load current, and another biphase current > load current, non-electrical source, broken string phase current approximate zero, when there is earth fault, mains side Earth Phase forms single-phase short circuit current, another biphase current is load current, thus generation zero-sequence current, and wire creates total capacitance electric current over the ground, two kinds of electric currents form total zero-sequence current, when total zero-sequence current reaches certain value, the action of zero sequence overcurrent protection, outlet switch is tripped, this just can sentence and know which kind of fault and fault generation section.
2. the differentiating method of disconnection fault and earth fault during Neutral Point Through Low Resistance according to claim 1; it is characterized in that: detecting voltage needs the time; if when disconnection fault and earth fault do not make zero sequence excess current protection act; grace time is had to can be used to detect voltage; if promptly detection voltage will be completed, detection voltage can be started with three-phase current unbalance.
3. the differentiating method of disconnection fault and earth fault during Neutral Point Through Low Resistance according to claim 1, it is characterized in that: the differentiation of disconnection fault and earth fault, both can be used in electrical power distribution automatization system, also can be used in the common 10KV system without power distribution automation.
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| CN201210417797.6A CN102937687B (en) | 2012-10-26 | 2012-10-26 | Method for distinguishing disconnection fault and grounding fault during grounding of neutral point through small resistor |
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| CN201210417797.6A CN102937687B (en) | 2012-10-26 | 2012-10-26 | Method for distinguishing disconnection fault and grounding fault during grounding of neutral point through small resistor |
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| CN103972872A (en) * | 2014-04-16 | 2014-08-06 | 江苏汉天星配电自动化科技有限公司 | Fault handling method of main lines and branch lines in 10KV distribution automation line |
| CN103969548A (en) * | 2014-04-16 | 2014-08-06 | 江苏汉天星配电自动化科技有限公司 | Grounding line selecting and ground fault section positioning method for arc suppression coil |
| CN106093683B (en) * | 2016-06-29 | 2019-03-12 | 河南平芝高压开关有限公司 | Heater broken wire detection system and wire break detection method |
| CN106711965B (en) * | 2016-12-08 | 2019-03-26 | 南京南瑞继保电气有限公司 | A kind of transmission line of electricity broken string method of discrimination based on semaphore transmitting |
| CN107910857B (en) * | 2017-12-18 | 2019-04-16 | 李晓明 | A kind of heavy current grounding system zero-sequence protection method and system |
| CN109921405A (en) * | 2019-04-24 | 2019-06-21 | 南京泰润电力工程有限公司 | A kind of earthing method of medium voltage network neutral point |
| CN110794335A (en) * | 2019-12-05 | 2020-02-14 | 国网江苏省电力有限公司南通供电分公司 | Single-phase grounding detection system based on waveform difference and detection method thereof |
| CN111579927B (en) * | 2020-05-22 | 2022-03-29 | 南京南瑞继保电气有限公司 | Disconnection protection judgment method and device suitable for single-side power transmission line |
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| CN1397807A (en) * | 2002-08-16 | 2003-02-19 | 华中科技大学 | Method for positioning grounding failure region of feed line in low-current grounding system |
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| CN101534001B (en) * | 2008-03-11 | 2011-11-23 | 杨万钟 | Method for detecting distribution network short circuit fault and restoring power supply in non-broken-down section |
| CN101701998A (en) * | 2009-11-19 | 2010-05-05 | 山东泰开自动化有限公司 | Novel faulty line selection method in low current faulty grounding system |
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| CN1397807A (en) * | 2002-08-16 | 2003-02-19 | 华中科技大学 | Method for positioning grounding failure region of feed line in low-current grounding system |
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| Title |
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| 小电流接地系统单相断线加接地故障的分析;张慧芬等;《全国电网中性点接地方式与接地技术研讨会论文》;20050517;第117-119页 * |
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