CN111817281B - Switching control system and method for arc suppression coil parallel low-resistance grounding device - Google Patents
Switching control system and method for arc suppression coil parallel low-resistance grounding device Download PDFInfo
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- CN111817281B CN111817281B CN202010447543.3A CN202010447543A CN111817281B CN 111817281 B CN111817281 B CN 111817281B CN 202010447543 A CN202010447543 A CN 202010447543A CN 111817281 B CN111817281 B CN 111817281B
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- 238000000034 method Methods 0.000 title claims abstract description 19
- 230000007935 neutral effect Effects 0.000 claims abstract description 112
- 238000013016 damping Methods 0.000 claims abstract description 84
- 238000012544 monitoring process Methods 0.000 claims abstract description 36
- 239000003990 capacitor Substances 0.000 claims description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000002955 isolation Methods 0.000 description 3
- 230000009286 beneficial effect 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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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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Abstract
The invention discloses a switching control system of an arc suppression coil parallel low-resistance grounding device, which comprises: the device comprises a neutral point zero sequence voltage monitoring and analyzing module, a voltage transformer, a grounding transformer, an arc suppression coil, a low-resistance grounding resistor, a resistor fling-cut switch and a damping resistance control module; the neutral point of the grounding transformer is connected with the voltage transformer, the arc suppression coil and the resistor switching switch; and the neutral point zero sequence voltage monitoring and analyzing module is connected with the voltage transformer, the damping resistance control module and the resistor switching switch and is used for monitoring the neutral point voltage amplitude of the grounding transformer and analyzing the fault conditions of the grounding transformer and the outgoing line according to the neutral point voltage amplitude so as to control the operation of the resistor switching switch and the damping resistance control module. The invention also discloses a switching control method of the arc suppression coil parallel low-resistance grounding device, which greatly improves the power supply safety and reliability of the power distribution network and has the characteristics of simplicity, reliability and high feasibility.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a switching control system and method of an arc suppression coil parallel low-resistance grounding device.
Background
In the power system, the neutral grounding mode is selected according to the insulation level of the power grid equipment and the magnitude of the capacitance current. For a power distribution network mainly comprising an overhead line, a neutral point is grounded through an arc suppression coil; for an urban power distribution network mainly based on cable lines, the single-phase earth fault has large capacitance and current, and a mode that a neutral point is grounded through a small resistor is mostly adopted. However, the neutral point is grounded through an arc suppression coil, which brings certain difficulty to permanent fault line selection and is difficult to rapidly and accurately remove faults; the neutral point can not distinguish instantaneous earth faults from permanent earth faults in a small-resistance earthing mode, and line tripping is started for all single-phase earthing, so that the line tripping times are increased, and the power supply reliability is influenced.
Disclosure of Invention
The embodiment of the invention provides a switching control system and method of an arc suppression coil parallel low-resistance grounding device, which realize rapid and accurate fault isolation by adopting a grounding mode that a neutral point is connected with a low resistance in parallel through an arc suppression coil, greatly improve the power supply safety and reliability of a power distribution network, and have the characteristics of simplicity, reliability and high feasibility.
An embodiment of the present invention provides a system for controlling switching of an arc suppression coil parallel low-resistance grounding device, including: the device comprises a neutral point zero sequence voltage monitoring and analyzing module, a voltage transformer, a grounding transformer, an arc suppression coil, a low-resistance grounding resistor, a resistor fling-cut switch and a damping resistance control module;
the head end of the grounding transformer is connected to the three-phase system, and the tail end of the grounding transformer is grounded;
the neutral point of the grounding transformer is connected with the first end of the voltage transformer, the first end of the arc suppression coil and the first end of the resistor fling-cut switch; the second end of the voltage transformer is grounded;
the second end of the arc suppression coil is connected with the first end of the damping resistance control module, and the second end of the damping resistance control module is grounded; the second end of the resistor switching switch is connected with the first end of the low-resistance grounding resistor, and the second end of the low-resistance grounding resistor is grounded;
the neutral point zero sequence voltage monitoring and analyzing module is connected with the voltage transformer, the damping resistance control module and the resistor switching switch, and is used for monitoring the neutral point voltage amplitude of the grounding transformer and analyzing the fault conditions of the grounding transformer and the outgoing line according to the neutral point voltage amplitude so as to control the work of the resistor switching switch and the damping resistance control module;
the neutral point zero sequence voltage monitoring and analyzing module is used for acquiring a second voltage threshold value according to the following steps:
constructing a circuit model of zero sequence overcurrent protection of a fault line;
based on the circuit model, the second voltage threshold is obtained according to the following formula:
wherein R isgsetTransition resistance value, R, for zero sequence overcurrent protection toleranceoutThe equivalent impedance value, I, of the parallel connection of the arc suppression coil and the system to ground zero-sequence capacitor in the circuit modelsetSetting a current value for zero sequence overcurrent protection of the circuit, wherein Us is a system rated voltage value, L, of the circuit modelpIs the inductance of the arc suppression coil, C0For zero sequence capacitance, U, to ground of the system0setIs the second voltage threshold.
As an improvement of the above scheme, the damping resistance control module comprises a damping resistance and a damping resistance short-circuit switch;
the damping resistor is connected between the second end of the arc suppression coil and the grounding grid, and the damping resistor short circuit switches are connected to the two ends of the damping resistor in parallel;
and the neutral point zero-sequence voltage monitoring and analyzing module is connected with the damping resistor short-circuit switch and used for controlling the switching-on and switching-off of the damping resistor short-circuit switch according to the fault condition.
Another embodiment of the present invention provides a method for controlling the switching of an arc suppression coil parallel low-resistance grounding device, which is applied to a neutral point zero-sequence voltage monitoring and analyzing module in the switching control system of the arc suppression coil parallel low-resistance grounding device, and the method includes:
receiving the neutral point voltage amplitude from the grounding transformer in real time;
judging whether the voltage amplitude of the neutral point exceeds a first voltage threshold value or not; if so, the three-phase system has a single-phase earth fault, and the damping resistance control module is controlled to be in short circuit, so that the arc suppression coil is put into a compensation state;
when the arc suppression coil is used for compensation and is kept for a first preset time, and then whether the voltage amplitude of the neutral point exceeds a second voltage threshold value is judged; if so, controlling a resistor switching switch to be in short circuit so as to switch in the low-resistance grounding resistor;
and when the low-resistance grounding resistor is put into the device and kept for a second preset time, judging that the voltage amplitude of the neutral point does not exceed the first voltage threshold value again, considering that the fault is cleared, disconnecting the damping resistance control module and putting the low-resistance grounding resistor in and out.
As an improvement of the foregoing solution, the determining whether the amplitude of the neutral point voltage exceeds a first voltage threshold further includes:
and when the voltage amplitude of the neutral point is judged not to exceed the first voltage threshold, the fault is considered to be eliminated, and the damping resistance control module is disconnected.
As an improvement of the foregoing solution, the determining whether the neutral point voltage amplitude exceeds a second voltage threshold further includes:
and when the neutral point voltage amplitude is judged not to exceed the second voltage threshold, keeping the damping resistance control module in short circuit, and continuously monitoring the neutral point voltage amplitude from the grounding transformer.
As an improvement of the above, the method further comprises:
after the low-resistance grounding resistor is put into use and the second preset time is kept, judging whether the voltage amplitude of the neutral point exceeds the first voltage threshold value again; and if so, keeping the damping resistance control module in short circuit, and switching on and off the low-resistance grounding resistor.
Compared with the prior art, the switching control system and method for the arc suppression coil parallel low-resistance grounding device disclosed by the embodiment of the invention have the following beneficial effects:
the switching control system for connecting the low-resistance grounding device in parallel through the arc suppression coil comprises a neutral point zero-sequence voltage monitoring and analyzing module, a voltage transformer, a grounding transformer, the arc suppression coil, a low-resistance grounding resistor, a resistor switching switch and a damping resistance control module; the head end of the grounding transformer is connected to the three-phase system, and the tail end of the grounding transformer is grounded; the neutral point of the grounding transformer is connected with the first end of the voltage transformer, the first end of the arc suppression coil and the first end of the resistor fling-cut switch; the second end of the voltage transformer is grounded; the second end of the arc suppression coil is connected with the first end of the damping resistance control module, and the second end of the damping resistance control module is grounded; the second end of the resistor switching switch is connected with the first end of the low-resistance grounding resistor, and the second end of the low-resistance grounding resistor is grounded; the neutral point zero sequence voltage monitoring and analyzing module is connected with the voltage transformer, the damping resistance control module and the resistor switching switch and used for monitoring the neutral point voltage amplitude of the grounding transformer and analyzing the fault conditions of the grounding transformer and outgoing lines according to the neutral point voltage amplitude so as to control the resistor switching switch and the damping resistance control module, so that the neutral point zero sequence voltage amplitude is utilized to simply and effectively realize the control of the parallel low-resistance grounding device of the arc suppression coil, the neutral point is adopted to realize the quick and accurate fault isolation through the parallel low-resistance grounding mode of the arc suppression coil, the power supply safety and reliability of the power distribution network are greatly improved, and the neutral point zero sequence voltage monitoring and analyzing module has the characteristics of simplicity, reliability and high feasibility.
Drawings
Fig. 1 is a schematic structural diagram of an operation and retreat control system of an arc suppression coil parallel low-resistance grounding device according to a first embodiment of the invention;
fig. 2 is a schematic flow chart of a method for controlling switching of an arc suppression coil parallel low-resistance grounding device according to a second embodiment of the present invention;
fig. 3 is a schematic structural diagram of a circuit model for zero-sequence overcurrent protection of a faulty line according to a second embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a schematic structural diagram of a trip control system of an arc suppression coil parallel low-resistance grounding device according to an embodiment of the present invention includes: the system comprises a neutral point zero sequence voltage monitoring and analyzing module 1, a voltage transformer 2, a grounding transformer 3, an arc suppression coil 4, a low-resistance grounding resistor 5, a resistor fling-cut switch 6 and a damping resistance control module 7;
the head end of the grounding transformer 3 is connected to the three-phase system 31, and the tail end is grounded;
the neutral point of the grounding transformer 3 is connected with the first end of the voltage transformer 2, the first end of the arc suppression coil 4 and the first end of the resistor fling-cut switch 6; the second end of the voltage transformer 2 is grounded;
the second end of the arc suppression coil 4 is connected with the first end of the damping resistance control module 7, and the second end of the damping resistance control module 7 is grounded; the second end of the resistor switching switch 6 is connected with the first end of the low-resistance grounding resistor 5, and the second end of the low-resistance grounding resistor 5 is grounded;
the neutral point zero sequence voltage monitoring and analyzing module 1 is connected with the voltage transformer 2, the damping resistance control module 7 and the resistor switching switch 6, and is used for monitoring the neutral point voltage amplitude of the grounding transformer 3 and analyzing the fault conditions of the grounding transformer 3 and the outgoing line according to the neutral point voltage amplitude so as to control the work of the resistor switching switch 6 and the damping resistance control module 7.
The neutral point zero sequence voltage monitoring and analyzing module 1 is configured to obtain a second voltage threshold according to the following steps:
constructing a circuit model of zero sequence overcurrent protection of a fault line;
based on the circuit model, the second voltage threshold is obtained according to the following formula:
wherein R isgsetTransition resistance value, R, for zero sequence overcurrent protection toleranceoutThe equivalent impedance value, I, of the parallel connection of the arc suppression coil and the system to ground zero-sequence capacitor in the circuit modelsetSetting a current value for zero sequence overcurrent protection of the circuit, wherein Us is a system rated voltage value, L, of the circuit modelpIs the inductance of the arc suppression coil, C0For zero sequence capacitance, U, to ground of the system0setIs the second voltage threshold.
The grounding transformer 3 is used to form a neutral point in a delta connection network, and the neutral point is connected to a device such as the arc suppression coil 4 and the low-resistance grounding resistor 5. And the arc suppression coil 4 is connected between the neutral point of the grounding transformer 3 and a grounding grid and is used for compensating the capacitive current of the power grid. The low-resistance grounding resistor 5 is connected in series with the resistor switching switch 6, then is connected in parallel with the arc suppression coil 4 and is connected between the neutral point of the grounding transformer 3 and the grounding grid. The resistor-switching switch 6 is used to switch on or off the connection between the low-resistance grounding resistor 5 and the neutral point of the grounding transformer 3. The neutral point zero sequence voltage monitoring and analyzing module 1 is used for monitoring the neutral point voltage amplitude of the grounding transformer 3, analyzing whether the grounding transformer 3 and the outgoing line have ground faults or not according to the neutral point voltage amplitude, and controlling the on-off of the resistor switching switch 6. The voltage transformer 2 is used to monitor the neutral point voltage amplitude of the grounding transformer 3 in real time during operation of the apparatus.
Preferably, referring to fig. 1, the damping resistance control module 7 includes a damping resistance 71 and a damping resistance short-circuit switch 72;
the damping resistor 71 is connected between the second end of the arc suppression coil 4 and the grounding grid, and the damping resistor short-circuit switch 72 is connected to two ends of the damping resistor 71 in parallel;
and the neutral point zero-sequence voltage monitoring and analyzing module 1 is connected with the damping resistor short-circuit switch 72 and used for controlling the opening and closing of the damping resistor short-circuit switch 72 according to the fault condition.
The damping resistor 71 is used for forming a damping function for the arc extinguishing coil 4, and the damping resistor short-circuit switch 72 is used for short-circuiting the damping resistor 71 to play a role in damping elimination.
The switching control system for the arc suppression coil parallel low-resistance grounding device provided by the embodiment of the invention comprises a neutral point zero-sequence voltage monitoring and analyzing module, a voltage transformer, a grounding transformer, an arc suppression coil, a low-resistance grounding resistor, a resistor switching switch and a damping resistance control module; the head end of the grounding transformer is connected to the three-phase system, and the tail end of the grounding transformer is grounded; the neutral point of the grounding transformer is connected with the first end of the voltage transformer, the first end of the arc suppression coil and the first end of the resistor fling-cut switch; the second end of the voltage transformer is grounded; the second end of the arc suppression coil is connected with the first end of the damping resistance control module, and the second end of the damping resistance control module is grounded; the second end of the resistor switching switch is connected with the first end of the low-resistance grounding resistor, and the second end of the low-resistance grounding resistor is grounded; the neutral point zero sequence voltage monitoring and analyzing module is connected with the voltage transformer, the damping resistance control module and the resistor switching switch and used for monitoring the neutral point voltage amplitude of the grounding transformer and analyzing the fault conditions of the grounding transformer and outgoing lines according to the neutral point voltage amplitude so as to control the resistor switching switch and the damping resistance control module, so that the neutral point zero sequence voltage amplitude is utilized to simply and effectively realize the control of the parallel low-resistance grounding device of the arc suppression coil, the neutral point is adopted to realize the quick and accurate fault isolation through the parallel low-resistance grounding mode of the arc suppression coil, the power supply safety and reliability of the power distribution network are greatly improved, and the neutral point zero sequence voltage monitoring and analyzing module has the characteristics of simplicity, reliability and high feasibility.
Referring to fig. 2, a schematic flow chart of a method for controlling switching of a parallel low-resistance grounding device of an arc suppression coil according to a second embodiment of the present invention is shown, where the method is applied to a neutral zero sequence voltage monitoring and analyzing module in a switching control system of a parallel low-resistance grounding device of an arc suppression coil according to the first embodiment, and the method includes steps S101 to S104.
And S101, receiving the neutral point voltage amplitude from the grounding transformer in real time.
S102, judging whether the voltage amplitude of the neutral point exceeds a first voltage threshold value or not; if so, the three-phase system has a single-phase earth fault, and the damping resistance control module is controlled to be in short circuit, so that the arc suppression coil is put into a compensation state.
In an alternative embodiment, when the neutral point voltage amplitude is judged not to exceed the first voltage threshold, the fault is considered to be eliminated, and the damping resistance control module is disconnected.
S103, when the arc suppression coil is used for compensation and is kept for a first preset time, and then the neutral point voltage amplitude is judged to exceed the first voltage threshold, whether the neutral point voltage amplitude exceeds a second voltage threshold is judged; and if so, controlling the resistor switching switch to be in short circuit so as to switch in the low-resistance grounding resistor.
In an optional embodiment, the determining whether the magnitude of the neutral point voltage exceeds a second voltage threshold further includes:
and when the neutral point voltage amplitude is judged not to exceed the second voltage threshold, keeping the damping resistance control module in short circuit, and continuously monitoring the neutral point voltage amplitude from the grounding transformer.
Preferably, referring to fig. 3, the schematic structural diagram of a circuit model for zero-sequence overcurrent protection of a fault line provided in the second embodiment of the present invention is shown, where the system voltage source Us and the transition resistor R aregsetAnd arc suppression coil LpSeries connected, system to ground zero sequence capacitance C0Are connected in parallel to the arc suppression coil LpTwo ends. Specifically, the second voltage threshold is obtained by the following steps:
constructing a circuit model of zero sequence overcurrent protection of a fault line;
based on the circuit model, the second voltage threshold is obtained according to the following formula:
wherein R isgsetTransition resistance value, R, for zero sequence overcurrent protection toleranceoutThe equivalent impedance value, I, of the parallel connection of the arc suppression coil and the system to ground zero-sequence capacitor in the circuit modelsetSetting a current value for zero sequence overcurrent protection of the circuit, wherein Us is a system rated voltage value, L, of the circuit modelpIs the inductance of the arc suppression coil, C0For zero-sequence capacitance to ground of the system, I0setIs the second voltage threshold.
And S104, when the low-resistance grounding resistor is put into the device and kept for a second preset time, and then the voltage amplitude of the neutral point is judged to be not greater than the first voltage threshold value again, the fault is considered to be cleared, the damping resistance control module is disconnected, and the low-resistance grounding resistor is put into and taken out.
In an alternative embodiment, after the low-resistance grounding resistor is switched on and kept for the second preset time, whether the neutral point voltage amplitude exceeds the first voltage threshold value is judged again; and if so, keeping the damping resistance control module in short circuit, and switching on and off the low-resistance grounding resistor.
In a specific embodiment, after the secondary signal of the voltage transformer is subjected to AD conversion, the neutral zero-sequence voltage monitoring and analyzing module judges whether the voltage amplitude of the neutral point exceeds a first voltage threshold, so that whether a single-phase ground fault occurs in a three-phase system can be judged in real time. When the voltage amplitude of the neutral point exceeds a first voltage threshold value, the single-phase earth fault is judged to occur, and the neutral point zero sequence voltage monitoring and analyzing module controls the damping resistor short-circuit switch to short-circuit the damping resistor, so that the arc suppression coil is put into a compensation state. When the voltage amplitude of the neutral point does not exceed the first voltage threshold value, no operation is executed when the single-phase earth fault is judged not to occur.
Further, the arc suppression coil is put into compensation for a first preset time period T0, wherein the first preset time period is preferably 5-10 s. Further, the neutral point voltage magnitude is continuously monitored during the first preset duration. Judging whether the voltage amplitude of the neutral point exceeds the first voltage threshold value again; if not, the grounding fault is extinguished after being compensated by the arc suppression coil, and the fault disappears.
The first voltage threshold is preferably the maximum zero sequence voltage value caused by the maximum unbalance of the three-phase system, and a certain margin is added, and the value is generally 15V.
Optionally, after the arc suppression coil is put into the compensation time T0, if the neutral point voltage amplitude still exceeds the first voltage threshold, further determining whether the neutral point voltage amplitude exceeds a second voltage threshold; if yes, the low-resistance switching switch is in short circuit, the low-resistance grounding resistor is switched in, and the short circuit state of the damping resistor is kept. And if not, keeping the short-circuit state of the damping resistor, and continuously monitoring the voltage amplitude of the neutral point.
After the low-resistance grounding resistor is put into the circuit breaker, keeping the low-resistance grounding resistor in the put-in state for a second preset time period T1, judging whether the voltage amplitude of the neutral point exceeds the first voltage threshold value again, if not, indicating that the fault line has already been removed by tripping the circuit breaker, withdrawing the damping resistor short-circuit switch to put in and withdraw the damping resistor, and disconnecting the resistor switching switch to put in and withdraw the low-resistance grounding resistor. And if the voltage still exceeds the first voltage threshold, keeping the short-circuit state of the damping resistor, and disconnecting the resistor switching switch to switch on or off the low-resistance grounding resistor.
In the method for controlling the switching of the arc suppression coil parallel low-resistance grounding device provided by the second embodiment of the invention, the neutral point voltage amplitude from the grounding transformer is received in real time, whether the neutral point voltage amplitude exceeds the first voltage threshold is judged, if yes, a single-phase grounding fault occurs in the three-phase system, the damping resistance control module is controlled to be in a short circuit state, the arc suppression coil is switched into a compensation state, when the arc suppression coil is switched into compensation and kept for a first preset time period, and then the neutral point voltage amplitude is judged to exceed the first voltage threshold, whether the neutral point voltage amplitude exceeds the second voltage threshold is judged, if yes, the resistor switching switch is controlled to be in a short circuit state to switch the low-resistance grounding resistor, and when the low-resistance grounding resistor is switched into and kept for a second preset time period, and then the neutral point voltage amplitude is judged again not to exceed the first voltage threshold, and then considering that the fault is cleared, disconnecting the damping resistance control module and switching on and off the low-resistance grounding resistor, so that the control of the arc suppression coil parallel low-resistance grounding device is simply and effectively realized by utilizing the zero-sequence voltage amplitude of the neutral point, the fault is quickly and accurately isolated by adopting a grounding mode that the neutral point is connected with the low resistance through the arc suppression coil in parallel, the power supply safety and reliability of the power distribution network are greatly improved, and the method has the characteristics of simplicity, reliability and high feasibility.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (6)
1. The utility model provides an arc suppression coil connects low resistance earthing device's switching control system which characterized in that includes: the device comprises a neutral point zero sequence voltage monitoring and analyzing module, a voltage transformer, a grounding transformer, an arc suppression coil, a low-resistance grounding resistor, a resistor fling-cut switch and a damping resistance control module;
the head end of the grounding transformer is connected to the three-phase system, and the tail end of the grounding transformer is grounded;
the neutral point of the grounding transformer is connected with the first end of the voltage transformer, the first end of the arc suppression coil and the first end of the resistor fling-cut switch; the second end of the voltage transformer is grounded;
the second end of the arc suppression coil is connected with the first end of the damping resistance control module, and the second end of the damping resistance control module is grounded; the second end of the resistor switching switch is connected with the first end of the low-resistance grounding resistor, and the second end of the low-resistance grounding resistor is grounded;
the neutral point zero sequence voltage monitoring and analyzing module is connected with the voltage transformer, the damping resistance control module and the resistor switching switch, and is used for monitoring the neutral point voltage amplitude of the grounding transformer and analyzing the fault conditions of the grounding transformer and the outgoing line according to the neutral point voltage amplitude so as to control the work of the resistor switching switch and the damping resistance control module;
the analyzing the fault conditions of the grounding transformer and the outgoing line according to the voltage amplitude of the neutral point so as to control the work of the resistor switching switch and the damping resistance control module comprises the following steps:
receiving the neutral point voltage amplitude from the grounding transformer in real time;
judging whether the voltage amplitude of the neutral point exceeds a first voltage threshold value or not; if so, the three-phase system has a single-phase earth fault, and the damping resistance control module is controlled to be in short circuit, so that the arc suppression coil is put into a compensation state;
when the arc suppression coil is used for compensation and is kept for a first preset time, and then whether the voltage amplitude of the neutral point exceeds a second voltage threshold value is judged; if so, controlling a resistor switching switch to be in short circuit so as to switch in the low-resistance grounding resistor;
when the low-resistance grounding resistor is put into the device and kept for a second preset time, and then the voltage amplitude of the neutral point is judged to be not greater than the first voltage threshold value again, the fault is considered to be cleared, the damping resistance control module is disconnected, and the low-resistance grounding resistor is put into and taken out;
wherein the second voltage threshold is obtained by:
constructing a circuit model of zero sequence overcurrent protection of a fault line;
based on the circuit model, the second voltage threshold is obtained according to the following formula:
wherein R isgsetTransition resistance value, R, for zero sequence overcurrent protection toleranceoutThe equivalent impedance value, I, of the parallel connection of the arc suppression coil and the system to ground zero-sequence capacitor in the circuit modelsetSetting a current value for zero sequence overcurrent protection of the circuit, wherein Us is a system rated voltage value, L, of the circuit modelpIs the inductance of the arc suppression coil, C0For zero sequence capacitance, U, to ground of the system0setIs the second voltage threshold.
2. The system for controlling the switching on and off of the arc suppression coil parallel low-resistance grounding device according to claim 1, wherein the damping resistance control module comprises a damping resistance and a damping resistance short-circuit switch;
the damping resistor is connected between the second end of the arc suppression coil and the grounding grid, and the damping resistor short circuit switches are connected to the two ends of the damping resistor in parallel;
and the neutral point zero-sequence voltage monitoring and analyzing module is connected with the damping resistor short-circuit switch and used for controlling the switching-on and switching-off of the damping resistor short-circuit switch according to the fault condition.
3. A method for controlling the switching of a parallel low-resistance grounding device of an arc suppression coil, which is suitable for a neutral point zero-sequence voltage monitoring and analyzing module in a switching control system of the parallel low-resistance grounding device of the arc suppression coil according to claims 1 to 2, and comprises the following steps:
receiving the neutral point voltage amplitude from the grounding transformer in real time;
judging whether the voltage amplitude of the neutral point exceeds a first voltage threshold value or not; if so, the three-phase system has a single-phase earth fault, and the damping resistance control module is controlled to be in short circuit, so that the arc suppression coil is put into a compensation state;
when the arc suppression coil is used for compensation and is kept for a first preset time, and then whether the voltage amplitude of the neutral point exceeds a second voltage threshold value is judged; if so, controlling a resistor switching switch to be in short circuit so as to switch in the low-resistance grounding resistor;
when the low-resistance grounding resistor is put into the device and kept for a second preset time, and then the voltage amplitude of the neutral point is judged to be not greater than the first voltage threshold value again, the fault is considered to be cleared, the damping resistance control module is disconnected, and the low-resistance grounding resistor is put into and taken out;
wherein the second voltage threshold is obtained by:
constructing a circuit model of zero sequence overcurrent protection of a fault line;
based on the circuit model, the second voltage threshold is obtained according to the following formula:
wherein R isgsetTransition resistance value, Ro, for zero sequence overcurrent protection toleranceutThe equivalent impedance value, I, of the parallel connection of the arc suppression coil and the system to ground zero-sequence capacitor in the circuit modelsetSetting a current value for zero sequence overcurrent protection of the circuit, wherein Us is a system rated voltage value, L, of the circuit modelpIs the inductance of the arc suppression coil, C0For zero sequence capacitance, U, to ground of the system0setIs the second voltage threshold.
4. A method for controlling the operation and the retreat of an arc suppression coil parallel low-resistance grounding device according to claim 3, wherein the determining whether the magnitude of the neutral point voltage exceeds a first voltage threshold value further comprises:
and when the voltage amplitude of the neutral point is judged not to exceed the first voltage threshold, the fault is considered to be eliminated, and the damping resistance control module is disconnected.
5. A method for controlling the operation and the retreat of an arc suppression coil parallel low-resistance grounding device according to claim 3, wherein the determining whether the magnitude of the neutral point voltage exceeds a second voltage threshold value further includes:
and when the neutral point voltage amplitude is judged not to exceed the second voltage threshold, keeping the damping resistance control module in short circuit, and continuously monitoring the neutral point voltage amplitude from the grounding transformer.
6. A method for controlling the operation and retreat of an arc suppression coil parallel low-resistance grounding device according to claim 3, further comprising:
after the low-resistance grounding resistor is put into use and the second preset time is kept, judging whether the voltage amplitude of the neutral point exceeds the first voltage threshold value again; and if so, keeping the damping resistance control module in short circuit, and switching on and off the low-resistance grounding resistor.
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