CN109449912B - Neutral point grounding device and control method thereof - Google Patents
Neutral point grounding device and control method thereof Download PDFInfo
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- CN109449912B CN109449912B CN201811418747.3A CN201811418747A CN109449912B CN 109449912 B CN109449912 B CN 109449912B CN 201811418747 A CN201811418747 A CN 201811418747A CN 109449912 B CN109449912 B CN 109449912B
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- 230000007935 neutral effect Effects 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 20
- 230000001629 suppression Effects 0.000 claims abstract description 23
- 230000007704 transition Effects 0.000 abstract description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000001052 transient effect Effects 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/08—Limitation or suppression of earth fault currents, e.g. Petersen coil
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Abstract
The invention provides a neutral point grounding device and a control method thereof, wherein the neutral point grounding device comprises an arc suppression coil, a grounding coil and a grounding coil, wherein one end of the arc suppression coil is connected with a neutral point, and the other end of the arc suppression coil is grounded; the resistance unit is connected with the arc suppression coil in parallel and is used for providing a resistance capable of changing the resistance value; and the controller is used for controlling the resistance value of the resistance unit and the on-off of the resistance unit circuit. According to the neutral point grounding device and the control method thereof, the resistance value is the largest when the adjustable resistor is put into the neutral point grounding device at first, the circuit metallic grounding and medium-low resistance grounding faults with large occupation ratio can be judged, the fault current is small, and the personal safety is ensured; for the earth faults with few transition resistors as high resistance, no fault line is judged, the adjustable resistor is automatically adjusted to be the minimum, the fault characteristics are further increased, and the fault selection accuracy is improved.
Description
Technical Field
The invention relates to the technical field of power transmission and distribution, in particular to a neutral point grounding device and a control method thereof.
Background
The grounding mode of the neutral point of the power grid comprises the following steps: a non-grounded mode, a mode of grounding through an arc suppression coil, a low-resistance grounding and the like. Different grounding methods have their own advantages and disadvantages: the neutral point non-grounding mode allows the operation to be continued for 2 hours when the single phase is grounded, but when the grounding current exceeds a certain value, the electric arc cannot be self-extinguished, and the arc grounding overvoltage is easily generated; the neutral point can compensate larger capacitive current generated by a power grid in a mode of grounding through the arc suppression coil, but resonance overvoltage can be caused by inaccurate measurement and improper compensation of the capacitive current, and when the capacity of the arc suppression coil does not meet the requirement, upgrading and transformation are needed; the neutral point is grounded with large current in a low-resistance grounding mode, which is beneficial to fault line selection, but the tripping rate is high, and when the resistance value of the local resistor is selected too small, the grounding fault current is large, thereby bringing potential safety hazards to equipment, communication lines and personal safety.
In recent years, a grounding system in which parallel resistors are connected to arc suppression coils has been developed, taking advantage of the advantages of the arc suppression coils and the low-resistance grounding system. The parallel resistors of the arc suppression coil are fixed resistors, if the resistance value of the resistor is large, the sensitivity is low, and if the resistance value of the resistor is small, the fault current is large, so that the personal safety is not facilitated. In addition, the selection of the fault characteristic quantity is mainly based on the magnitude of the zero sequence current, and when the transition resistance is large, the fault line cannot be effectively judged only based on the magnitude of the zero sequence current.
Disclosure of Invention
The invention aims to provide a neutral point grounding device and a control method thereof, which improve the sensitivity, provide the safety and effectively judge a fault line.
The invention provides a neutral point grounding device, comprising:
one end of the arc suppression coil is connected with the neutral point, and the other end of the arc suppression coil is grounded;
the resistance unit is connected with the arc suppression coil in parallel and is used for providing a resistance capable of changing the resistance value;
and the controller is used for controlling the resistance value of the resistance unit and the on-off of the resistance unit circuit.
Further, the resistance unit includes: the controller is respectively connected with the switch and the adjustable resistor and is used for controlling the on-off of the switch and the resistance value of the adjustable resistor.
The invention also provides a control method of the neutral point grounding device, which comprises the following steps:
the controller controls the resistance unit to keep the circuit thereof in an open circuit state;
after the fault occurs and continues for a first time period, the controller controls the resistance unit to enable the circuit of the resistance unit to be communicated, and meanwhile, the resistance value of the resistance unit is adjusted to be maximum;
judging a fault line, if the fault line is successfully judged, controlling the resistance unit to enable the circuit of the resistance unit to keep an open circuit state by the controller, and if the fault line is not judged, adjusting the resistance value of the resistance unit to be minimum by the controller, and judging the fault line again;
and after the controller adjusts the resistance value of the resistance unit to be minimum and continues for a second time period, the controller controls the resistance unit to enable the circuit of the resistance unit to keep an open circuit state.
Further, the method for judging the fault line comprises the following steps: the fault line is the line with the largest increment of the active component or the active component of the zero-sequence current of each line.
Further, the first time period is 3-7 s.
Further, the first period of time is 5 s.
Further, the second period of time is 2 s.
According to the neutral point grounding device and the control method thereof, the resistance value is the largest when the adjustable resistor is put into the neutral point grounding device at first, the circuit metallic grounding and medium-low resistance grounding faults with large occupation ratio can be judged, the fault current is small, and the personal safety is ensured; for the earth faults with few transition resistors as high resistance, no fault line is judged, the adjustable resistor is automatically adjusted to be the minimum, the fault characteristics are further increased, and the fault selection accuracy is improved.
Drawings
FIG. 1 is a schematic diagram of a neutral grounding arrangement according to the present invention;
fig. 2 is a flowchart of a control method of the neutral grounding apparatus of the present invention.
In the figure, 1 is a neutral point, 2 is an arc suppression coil, 3 is an adjustable resistor, 4 is a switch, and 5 is a controller.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
A neutral grounding apparatus, as shown in fig. 1, comprising:
one end of the arc suppression coil 2 is connected with the neutral point 1, and the other end of the arc suppression coil is grounded;
the resistance unit is connected with the arc suppression coil 2 in parallel and is used for providing a resistance capable of changing the resistance value;
and the controller 5 is used for controlling the resistance value of the resistance unit and the on-off of the circuit of the resistance unit.
In an optional implementation manner of this embodiment, the resistance unit includes: the controller 5 is respectively connected with the switch 4 and the adjustable resistor 3 and is used for controlling the on-off of the switch 4 and the resistance value of the adjustable resistor 5. Of course, the resistance unit may have other structures.
A method for controlling the neutral point grounding apparatus according to any one of the above embodiments, as shown in fig. 2, includes the steps of:
the controller 5 controls the resistance unit to keep the circuit thereof in an open state;
after the fault occurs and continues for a first time period, the controller 5 controls the resistance unit to enable the circuit of the resistance unit to be communicated, and meanwhile, the resistance value of the resistance unit is adjusted to be maximum;
judging a fault line, if the fault line is successfully judged, controlling the resistance unit to keep the circuit thereof in an open circuit state by the controller 5, and if the fault line is not judged, adjusting the resistance value of the resistance unit to be minimum by the controller 5, and judging the fault line again;
after the controller 5 adjusts the resistance value of the resistance unit to the minimum value and continues for a second time period, the controller 5 controls the resistance unit to keep the circuit thereof in the off state.
In an optional implementation manner of this embodiment, the method for determining the faulty line includes: the fault line is the line with the largest increment of the active component or the active component of the zero-sequence current of each line.
In an optional implementation manner of this embodiment, the first time period is 3 to 7 seconds, and preferably, the first time period is 5 seconds.
In an optional implementation manner of this embodiment, the second time period is 2 s.
Taking a 10kV power distribution network as an example, a control method of a neutral point grounding device is described as follows:
when the system has single-phase earth fault, the arc suppression coil is adjusted to a compensation state, the resistance unit is not connected in the initial stage of the fault, the arc suppression coil compensates the capacitive current to be below 10A, if the fault is transient fault, the fault arc can be automatically extinguished, and the self-recovery probability of the transient fault is improved. After a period of 3-7 s (which can be set to 5s and adjusted by the operation condition), if the zero sequence voltage exists continuously, the fault still exists, and at this time, the resistance unit is put into use (the resistance value is set to be the maximum value of 150 Ω). By collecting the zero sequence current of each line, the active component of the zero sequence current or the maximum increment of the active component after the resistance unit is put into the line is judged as a fault line, and then the fault line is cut off by protection action. If the fault line selection is accurate, the resistor is operated for 2s and then quit operation; and if the line is not correctly selected, the resistance is automatically adjusted to the minimum value of 45 omega, and the operation is quitted after 2 seconds no matter whether the line is correctly selected or not.
Therefore, after a fault occurs, the capacitance current is compensated through the grounding of the arc suppression coil, most transient single-phase grounding faults can be eliminated, for permanent faults, the resistance unit with the maximum resistance value is added, larger resistive current is generated, the line selection accuracy is improved, and most permanent faults can be judged; if few high-resistance faults are not judged correctly, the resistance value of the resistance unit is adjusted to 45 omega, fault characteristics are increased, and the accuracy of line selection is improved. Through the series of measures, the line selection accuracy is greatly improved, and the danger of personal electric shock is further prevented.
The scope of the invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (7)
1. A neutral grounding apparatus, comprising:
one end of the arc suppression coil is connected with the neutral point, and the other end of the arc suppression coil is grounded;
the resistance unit is connected with the arc suppression coil in parallel and is used for providing a resistance capable of changing the resistance value;
the controller is used for controlling the resistance unit to enable the circuit of the resistance unit to keep an open circuit state, controlling the resistance unit to enable the circuit of the resistance unit to be communicated after a fault occurs and lasts for a first time period, and meanwhile adjusting the resistance value of the resistance unit to be maximum; judging a fault line, if the fault line is successfully judged, controlling the resistance unit to enable the circuit of the resistance unit to keep an open circuit state, if the fault line is not judged, adjusting the resistance value of the resistance unit to be minimum, and judging the fault line again; and after the resistance value of the resistance unit is adjusted to be minimum and continues for a second time period, controlling the resistance unit to enable the circuit of the resistance unit to keep an open circuit state.
2. The neutral grounding apparatus of claim 1, wherein the resistance unit comprises: the controller is respectively connected with the switch and the adjustable resistor and is used for controlling the on-off of the switch and the resistance value of the adjustable resistor.
3. The method of controlling a neutral grounding apparatus according to claim 1 or 2, comprising the steps of:
the controller controls the resistance unit to keep the circuit thereof in an open circuit state;
after the fault occurs and continues for a first time period, the controller controls the resistance unit to enable the circuit of the resistance unit to be communicated, and meanwhile, the resistance value of the resistance unit is adjusted to be maximum;
judging a fault line, if the fault line is successfully judged, controlling the resistance unit to enable the circuit of the resistance unit to keep an open circuit state by the controller, and if the fault line is not judged, adjusting the resistance value of the resistance unit to be minimum by the controller, and judging the fault line again;
and after the controller adjusts the resistance value of the resistance unit to be minimum and continues for a second time period, the controller controls the resistance unit to enable the circuit of the resistance unit to keep an open circuit state.
4. A control method of a neutral point grounding apparatus according to claim 3, wherein the method of judging the faulty wire is: the fault line is the line with the largest increment of the active component or the active component of the zero-sequence current of each line.
5. A control method of a neutral grounding apparatus according to claim 3, wherein the first period of time is 3 to 7 seconds.
6. The method of controlling a neutral grounding apparatus according to claim 5, wherein the first period of time is 5 s.
7. A control method of a neutral grounding apparatus according to claim 3, wherein the second period of time is 2 s.
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| CN201811418747.3A CN109449912B (en) | 2018-11-26 | 2018-11-26 | Neutral point grounding device and control method thereof |
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| CN201811418747.3A CN109449912B (en) | 2018-11-26 | 2018-11-26 | Neutral point grounding device and control method thereof |
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| CN109449912B true CN109449912B (en) | 2022-03-04 |
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| CN112103934A (en) * | 2020-08-19 | 2020-12-18 | 许继电气股份有限公司 | Resistor switching device and method in low-current line selection parallel connection |
| CN112986862B (en) * | 2021-04-27 | 2024-04-09 | 重庆大学 | Power distribution network fault indicator sensitivity improving method based on neutral point resistance control |
| CN114280415A (en) * | 2021-12-14 | 2022-04-05 | 国网江苏省电力有限公司常州供电分公司 | Power distribution network ground fault processing method based on parallel resistors of arc suppression coils |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101378192A (en) * | 2007-08-31 | 2009-03-04 | 中冶赛迪工程技术股份有限公司 | Resistance-grounded system |
| CN103560501A (en) * | 2013-11-19 | 2014-02-05 | 上海翱辰电气科技有限公司 | Controlled type small-resistor arc extinction device and method |
| CN104092206A (en) * | 2014-06-20 | 2014-10-08 | 国家电网公司 | Power distribution network grounding self-adaptive control system and method |
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| US8035938B2 (en) * | 2005-01-31 | 2011-10-11 | Georgia Tech Research Corporation | Active current surge limiters |
| US8514530B2 (en) * | 2011-04-28 | 2013-08-20 | Freescale Semiconductor, Inc. | Load control and protection system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101378192A (en) * | 2007-08-31 | 2009-03-04 | 中冶赛迪工程技术股份有限公司 | Resistance-grounded system |
| CN103560501A (en) * | 2013-11-19 | 2014-02-05 | 上海翱辰电气科技有限公司 | Controlled type small-resistor arc extinction device and method |
| CN104092206A (en) * | 2014-06-20 | 2014-10-08 | 国家电网公司 | Power distribution network grounding self-adaptive control system and method |
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