CN102890180A - Method for acquiring single-phase earth fault current of three-phase and three-core cable - Google Patents
Method for acquiring single-phase earth fault current of three-phase and three-core cable Download PDFInfo
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- CN102890180A CN102890180A CN2012104292207A CN201210429220A CN102890180A CN 102890180 A CN102890180 A CN 102890180A CN 2012104292207 A CN2012104292207 A CN 2012104292207A CN 201210429220 A CN201210429220 A CN 201210429220A CN 102890180 A CN102890180 A CN 102890180A
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Abstract
The invention discloses a method for acquiring a single-phase earth fault current of a three-phase three-core cable. The head end of a three-phase three-core cable shielding layer is serially connected with a zero-sequence current transformer, the three-phase three-core cable shielding layer is earthed through the zero-sequence current transformer and is used for acquiring the capacitance current without being influenced by a load imbalance current when the single-phase earth fault of the three-phase three-core cable is caused, so that the insulation property of the three-phase three-core cable can be well reflected; a voltage limiter is arranged on the far end of the three-phase three-core cable shielding layer, when the voltage of the three-phase three-core cable shielding layer raises to a limit value, the voltage limiter is of low impedance to guide current to the earth, the zero-sequence current transformer is not limited by the impedance, the number of turns of a primary side can be increased freely, so that the sensitivity of the protection of a low-current grounding and isolated neutral system is improved; and meanwhile, an iron core of the zero-sequence current transformer can adopt a cold-rolled particle oriented silicon steel sheet with high magnetic conduction property, so that high-frequency transient current when the earth fault is caused can be well reflected, the protection sensitivity is improved, and the strong popularization and application value is achieved.
Description
Technical field
The invention belongs to technical field of power systems, relate in particular to a kind of method that gathers three-phase triple cable single-phase earth fault current.
Background technology
At present; during three core power cable singlephase earth fault of domestic operation; for the protection of the fault current acquisition mode be: at cable end place installing cables type punching type ground current mutual inductor, the three-phase heart yearn of cable passes from current transformer, and there is following defective in this mode:
(1) owing to the restriction of acquisition mode, the electromagnetic type current transformer of employing is comprised of two lobe iron cores, and iron core is gapped, magnetic circuit reluctance is large, and excitation impedance is 1-3 Ω, obtain maximum sensitivity, need satisfy excitation impedance and equal to protect secondary impedance, the scene is difficult to accomplish this point;
When (2) or mutual inductor secondary load large when fault current was larger, current transformer core was saturated easily, and error is increased;
When (3) system normally moved, may there be the uneven situation of load current in three-phase, the out-of-balance current that current transformer is sensed when normally moving for escaping system, and the protection setting valve is higher, has reduced the sensitivity of protection.
Summary of the invention
The invention provides a kind of method that gathers three-phase triple cable single-phase earth fault current; when being intended to solve three core power cable singlephase earth fault of present domestic operation; for the protection of the fault current acquisition mode be: at cable end place installing cables type punching type current transformer; the three-phase heart yearn of cable passes from current transformer, and there is the problem that sensitivity is low, measuring error large, error increases, higher protection setting valve has reduced the sensitivity of protection in this fault current acquisition mode.
The object of the present invention is to provide a kind of method that gathers three-phase triple cable single-phase earth fault current, at three-phase triple cable screen layer head end serial connection zero sequence current mutual inductor, three-phase triple cable screen layer is by zero sequence current mutual inductor ground connection, and the capacitance current when gathering three-phase triple cable singlephase earth fault by zero sequence current mutual inductor, at the far-end of three-phase triple cable screen layer voltage limitator is set.
Further, the acquisition method of this fault current can be applicable to small current neutral grounding and isolated neutral system.
Further, when the voltage of three-phase triple cable screen layer was elevated to limit value, voltage limitator presented Low ESR, and electric current is imported the earth.
Further, zero sequence current mutual inductor is not limited by impedance, and primary side can increase arbitrarily the number of turn.
Further, zero sequence current mutual inductor is serially connected between three-phase triple cable screen layer and the earth, and the electric current that records is three-phase triple cable insulation current over the ground.
Further, the zero sequence current mutual inductor iron core can adopt the high cold rolling grain oriented silicon steel disc of magnetic property.
The method of collection three-phase triple cable single-phase earth fault current provided by the invention; at three-phase triple cable screen layer head end serial connection zero sequence current mutual inductor; three-phase triple cable screen layer is by zero sequence current mutual inductor ground connection; and the capacitance current when gathering three-phase triple cable singlephase earth fault by zero sequence current mutual inductor; be not subjected to load unbalanced current affects; can react well the insulating property of three-phase triple cable; far-end at three-phase triple cable screen layer arranges voltage limitator; when the voltage of three-phase triple cable screen layer is elevated to limit value; voltage limitator presents Low ESR; electric current is imported the earth; zero sequence current mutual inductor is not limited by impedance; primary side can increase arbitrarily the number of turn; improved the sensitivity of small current neutral grounding and isolated neutral system protection; the zero sequence current mutual inductor iron core can adopt the high cold rolling grain oriented silicon steel disc of magnetic property simultaneously; high frequency transient electric current in the time of can reacting better the earth fault generation; improved protection sensitivity; simple in structure; practical, have stronger propagation and employment and be worth.
Description of drawings
Fig. 1 is the principle schematic of the cable single-phase earthing fault current acquisition that provides of prior art;
Fig. 2 is the principle schematic of the cable single-phase earthing fault current acquisition that provides of the embodiment of the invention.
Among the figure: 1, punching type ground current mutual inductor; 2, cable shield; 3, zero sequence current mutual inductor; 4, voltage limitator.
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further described in detail.Should be appreciated that specific embodiment described herein only in order to explaining the present invention, and be not used in and limit invention.
Fig. 2 shows the principle of the cable single-phase earthing fault current acquisition that the embodiment of the invention provides.For convenience of explanation, only show part related to the present invention.
The object of the present invention is to provide a kind of method that gathers three-phase triple cable single-phase earth fault current, at three-phase triple cable screen layer 2 head ends serial connection zero sequence current mutual inductor 3, three-phase triple cable screen layer 2 is by zero sequence current mutual inductor 3 ground connection, and the capacitance current when gathering three-phase triple cable singlephase earth fault by zero sequence current mutual inductor 3, at the far-end of three-phase triple cable screen layer 2 voltage limitator 4 is set.
In embodiments of the present invention, the acquisition method of this fault current can be applicable to small current neutral grounding and isolated neutral system.
In embodiments of the present invention, when the voltage of three-phase triple cable screen layer 2 was elevated to limit value, voltage limitator 4 presented Low ESR, and electric current is imported the earth.
In embodiments of the present invention, zero sequence current mutual inductor 3 is not limited by impedance, and primary side can increase arbitrarily the number of turn, can improve the sensitivity of small current neutral grounding and isolated neutral system protection.
In embodiments of the present invention, zero sequence current mutual inductor 3 is serially connected between three-phase triple cable screen layer 2 and the earth, the electric current that records is three-phase triple cable insulation current over the ground, is not subjected to load unbalanced current affects, can react well the insulating property of three-phase triple cable.
In embodiments of the present invention, zero sequence current mutual inductor 3 iron cores can adopt the high cold rolling grain oriented silicon steel disc of magnetic property, and the high frequency transient electric current in the time of can reacting better the earth fault generation has improved protection sensitivity.
Below in conjunction with drawings and the specific embodiments application principle of the present invention is further described.
1. invention forms:
(1) in small current neutral grounding system, at three-phase triple cable screen layer 2 serial connection zero sequence current mutual inductors 3, the line capacitance electric current when gathering singlephase earth fault by zero sequence current mutual inductor 3.
(2) at the cable far-end voltage limitator 4 is set
2. ultimate principle
Take isolated neutral system as example, as shown in the figure, two three-phases, three core formula cable line L1 are arranged, L2 supposes that the damage of L2 circuit A phase cable insulation links to each other with screen layer, causes ground short circuit.
Under the former acquisition mode (Fig. 1), the electric current by non-fault line cable-type punching type current transformer 1 center is respectively: I
B1, I
C1,-(I
B1+ I
C1), I
B1+ I
C1(with from bus bar side flow line trackside direction for just) ,-(I
B1+ I
C1) and I
B1+ I
C1Cancel each other, the electric current that passes through that last cable-type punching type current transformer 1 records is I
B1+ I
C1Electric current by faulty line cable-type punching type current transformer 1 center is respectively: I
B2, I
C2,-I
A2,-(I
B1+ I
C1), I
B1+ I
C1(with from bus bar side flow line trackside direction for just), I wherein
A2=I
B1+ I
C1+ I
B2+ I
C2, after offsetting, the electric current that passes through that final cable-type punching type current transformer 1 records is I
B1+ I
C1
Under the new acquisition mode (Fig. 2), the primary side current that flows through non-fault line zero sequence current mutual inductor 3 is I
B1+ I
C1, the electric current that flows through faulty line zero sequence current mutual inductor 3 is I
B1+ I
C1
In sum, during singlephase earth fault, the fault current that new acquisition mode collects collects to such an extent that fault current equates with former acquisition mode.Therefore can replace cable-type punching type current transformer 1 by the mode at screen layer serial connection zero sequence current mutual inductor 3, carry out the fault current collection.
Too high for fear of the screen layer induced voltage, damage screen layer and zero sequence current mutual inductor 3, at screen layer installing voltage limitator 4.Voltage limitator 4 is identical with the lightning arrester principle, and when screen layer voltage was elevated to limit value, voltage limitator 4 presented Low ESR, and electric current is imported the earth, reduces screen layer voltage.
3. the advantage of novel acquisition mode:
(1) current transformer is not limited by impedance, and primary side can increase arbitrarily the number of turn, can improve to small current neutral grounding system the sensitivity of protection.
(2) because be serially connected between screen layer and the earth, the electric current that records is cable insulation current over the ground, is not subjected to load unbalanced current affects, can well react the insulating property of cable.
(3) iron core can adopt cold rolling grain oriented silicon steel disc, can improve magnetic property, and the high frequency transient electric current in the time of reacting better the earth fault generation improves protection sensitivity.
The method of the collection three-phase triple cable single-phase earth fault current that the embodiment of the invention provides; at three-phase triple cable screen layer 2 head ends serial connection zero sequence current mutual inductor 3; three-phase triple cable screen layer 2 is by zero sequence current mutual inductor 3 ground connection; and the capacitance current when gathering three-phase triple cable singlephase earth fault by zero sequence current mutual inductor 3; be not subjected to load unbalanced current affects; can react well the insulating property of three-phase triple cable; far-end at three-phase triple cable screen layer 2 arranges voltage limitator 4; when the voltage of three-phase triple cable screen layer 2 is elevated to limit value; voltage limitator 4 presents Low ESR; electric current is imported the earth; zero sequence current mutual inductor 3 is not limited by impedance; primary side can increase arbitrarily the number of turn; improved the sensitivity of small current neutral grounding and isolated neutral system protection; zero sequence current mutual inductor 3 iron cores can adopt the high cold rolling grain oriented silicon steel disc of magnetic property simultaneously; high frequency transient electric current in the time of can reacting better the earth fault generation; improved protection sensitivity; simple in structure; practical, have stronger propagation and employment and be worth.
The above only is preferred embodiment of the present invention, not in order to limiting the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. method that gathers three-phase triple cable single-phase earth fault current, it is characterized in that, at three-phase triple cable screen layer head end serial connection zero sequence current mutual inductor, three-phase triple cable screen layer is by zero sequence current mutual inductor ground connection, and the capacitance current when gathering three-phase triple cable singlephase earth fault by zero sequence current mutual inductor, at the far-end of three-phase triple cable screen layer voltage limitator is set.
2. the method for claim 1 is characterized in that, the acquisition method of this fault current can be applicable to small current neutral grounding and isolated neutral system.
3. the method for claim 1 is characterized in that, when the voltage of three-phase triple cable screen layer was elevated to limit value, voltage limitator presented Low ESR, and electric current is imported the earth.
4. the method for claim 1 is characterized in that, zero sequence current mutual inductor is not limited by impedance, and primary side can increase arbitrarily the number of turn.
5. the method for claim 1 is characterized in that, zero sequence current mutual inductor is serially connected between three-phase triple cable screen layer and the earth, and the electric current that records is three-phase triple cable insulation current over the ground.
6. the method for claim 1 is characterized in that, the zero sequence current mutual inductor iron core can adopt the high cold rolling grain oriented silicon steel disc of magnetic property.
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| CN2012104292207A CN102890180A (en) | 2012-11-01 | 2012-11-01 | Method for acquiring single-phase earth fault current of three-phase and three-core cable |
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| CN2012104292207A CN102890180A (en) | 2012-11-01 | 2012-11-01 | Method for acquiring single-phase earth fault current of three-phase and three-core cable |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103500276A (en) * | 2013-09-29 | 2014-01-08 | 中国人民解放军海军工程大学 | Identification algorithm effectiveness judgment method for ground faults of ship intermediate voltage electric power system |
| CN104485212A (en) * | 2014-11-28 | 2015-04-01 | 辽宁拓新电力电子有限公司 | Low-excitation-impedance single-phase transformer |
| CN106093714A (en) * | 2016-08-26 | 2016-11-09 | 淄博博鸿电气有限公司 | The selection method of single-phase grounded malfunction in grounded system of low current circuit |
| CN110988598A (en) * | 2019-12-17 | 2020-04-10 | 国网河北省电力有限公司 | Petal type urban power grid ground fault positioning method based on zero sequence current association |
| CN111076872A (en) * | 2019-12-17 | 2020-04-28 | 天津大学 | Petal type urban power grid ground fault accurate positioning method based on multi-line zero-sequence current information |
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| CN202420692U (en) * | 2011-12-29 | 2012-09-05 | 李成 | Cable metal cover layer grounded current and cable temperature monitoring system |
| CN102914683A (en) * | 2012-11-01 | 2013-02-06 | 天津市电力公司 | Method for acquiring single-phase grounding current of three-phase single cable |
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2012
- 2012-11-01 CN CN2012104292207A patent/CN102890180A/en active Pending
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| CN101317096A (en) * | 2005-11-28 | 2008-12-03 | 雷诺股份公司 | Out-of-line measurement of a current flowing through a load |
| CN101793936A (en) * | 2010-02-11 | 2010-08-04 | 河南省电力公司商丘供电公司 | Insulation state online monitoring method for condenser type bushings |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103500276A (en) * | 2013-09-29 | 2014-01-08 | 中国人民解放军海军工程大学 | Identification algorithm effectiveness judgment method for ground faults of ship intermediate voltage electric power system |
| CN103500276B (en) * | 2013-09-29 | 2015-04-22 | 中国人民解放军海军工程大学 | Identification algorithm effectiveness judgment method for ground faults of ship intermediate voltage electric power system |
| CN104485212A (en) * | 2014-11-28 | 2015-04-01 | 辽宁拓新电力电子有限公司 | Low-excitation-impedance single-phase transformer |
| CN106093714A (en) * | 2016-08-26 | 2016-11-09 | 淄博博鸿电气有限公司 | The selection method of single-phase grounded malfunction in grounded system of low current circuit |
| CN110988598A (en) * | 2019-12-17 | 2020-04-10 | 国网河北省电力有限公司 | Petal type urban power grid ground fault positioning method based on zero sequence current association |
| CN111076872A (en) * | 2019-12-17 | 2020-04-28 | 天津大学 | Petal type urban power grid ground fault accurate positioning method based on multi-line zero-sequence current information |
| CN110988598B (en) * | 2019-12-17 | 2021-01-26 | 国网河北省电力有限公司 | Petal type urban power grid ground fault positioning method based on zero sequence current association |
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