CN108711841B - fault current limiting unit and method for direct current system - Google Patents
fault current limiting unit and method for direct current system Download PDFInfo
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- CN108711841B CN108711841B CN201810554283.2A CN201810554283A CN108711841B CN 108711841 B CN108711841 B CN 108711841B CN 201810554283 A CN201810554283 A CN 201810554283A CN 108711841 B CN108711841 B CN 108711841B
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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
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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Abstract
The invention provides fault current limiting units and methods for DC system, including insulation shell, insulation baffle, anode electrode, cathode electrode, main through hole, liquid metal and auxiliary discharge loop, wherein, the current forms the current main loop under normal working state when passing through the liquid metal at two sides of the insulation baffle and the main through hole, the auxiliary discharge loop is conducted to generate short pulse current and forms the current branch circuit when short circuit fault after overlapping with the fault current generated by the main loop.
Description
Technical Field
The invention belongs to the technical field of circuit control, and particularly relates to fault current limiting units and a method for a direct current system.
Background
With the rapid development of economy in China and the gradual modernization of the Ministry of Industrial transportation , the demand for the capacity of a direct current power supply system is increasing, the short-circuit capacity and the short-circuit current level of a direct current power grid are also increasing, and the breaking capacity of a medium-voltage direct current circuit breaker cannot meet the demand for the short-circuit capacity of the medium-voltage direct current power grid at present.
However, both the existing two current limiting units have the problem of rated through-current, and in order to ensure short current limiting response time, the aperture of a current limiting main through-current hole is kept small, and the aperture of the through-current hole is small, so that the rated through-current cannot be borne, therefore, the existing current limiting unit can only adopt a parallel high-speed mechanism to bear the through-current, and the current is limited by current transfer when fault current occurs.
Disclosure of Invention
In order to overcome the defects or shortcomings of the short-circuit current limiting technology, fault current limiting units and methods for a direct current system are provided.
The technical scheme includes that fault current limiting units for the direct current system comprise an insulating shell, an insulating partition plate, an anode electrode, a cathode electrode, a main through hole, liquid metal and an auxiliary discharge loop, wherein the anode electrode and the cathode electrode are symmetrically arranged on two side walls of the insulating shell and form a closed cavity with the insulating shell, the insulating partition plate is vertically arranged in the cavity, the main through hole for bearing long-time large-current rated through current is formed in the middle of the insulating partition plate, the liquid metal is filled in the cavity, and the auxiliary discharge loop is connected with the anode electrode and the cathode electrode in parallel.
And the current forms a current main loop under a normal working state when passing through the liquid metal on the two sides of the insulating partition plate and the main through hole. The auxiliary discharge loop is conducted to generate short-time pulse current and forms a current branch circuit during short-circuit fault after being superposed with fault current generated by the main loop.
Preferably, the auxiliary discharge loop comprises a thyristor, an inductor and a pre-charging capacitor, and the thyristor, the inductor and the pre-charging capacitor are sequentially connected in series.
Preferably, the main through-hole is a circular through-hole.
Preferably, the diameter of the main through hole is larger than or equal to 15 mm.
Preferably, the limiting unit further comprises a controller for identifying the fault current and triggering the auxiliary discharge circuit to conduct.
Preferably, the anode electrode and the cathode electrode are made of copper.
Preferably, the filling height of the liquid metal is higher than that of the main through hole in the insulating partition plate, and the whole cavity does not need to be filled.
Preferably, the liquid metal is gallium indium tin alloy.
The invention also provides methods for limiting current by using the fault current limiting unit, wherein when a direct current system works normally, the auxiliary discharge circuit is in a disconnected state, current passes through liquid metal on two sides of the insulating partition plate and passes through the main through hole, and the main circuit is conducted.
Preferably, when a system short-circuit fault occurs, the controller identifies a fault current and triggers the auxiliary discharge circuit to be conducted.
Compared with the prior art, the invention has the following beneficial effects:
(1) the fault current limiting unit provided by the invention is based on the traditional self-contraction liquid metal current limiting technical principle, and on the basis, the main through-flow hole with larger aperture is selected, so that the long-time large-current rated through-flow can be borne, the use of a high-speed mechanism is avoided, and the structure is simpler.
(2) The invention adopts the design idea of combining the auxiliary discharge loop and the main loop of the system, the auxiliary discharge loop can quickly generate high-rise-rate current pulse after being conducted, the pre-arc time of the arcing of the main through hole is greatly shortened after the fault current of the main loop is superposed, and the current-limiting response time is faster.
(3) The fault current limiting unit provided by the invention has the advantages of novel structure, no need of parallel current-carrying units, high response speed, high current limiting efficiency and easiness in implementation.
Drawings
FIG. 1 is a schematic of the topology of the fault current limiting unit of the present invention;
in the figure, 1 insulating housing; 2 insulating partition boards; 3 an anode electrode; 4 a cathode electrode; 5 a main through flow hole; 6 liquid metal; 7 auxiliary discharge circuit;
fig. 2 is a schematic diagram of a working process of the fault current limiting unit when the dc system provided by the present invention works normally;
fig. 3 is a schematic diagram of the working process of the fault current limiting unit when the short-circuit fault of the dc system provided by the present invention occurs.
Detailed Description
The invention is described in detail with reference to fig. 1-3 and the following embodiments, but not as a limitation of the invention, as shown in fig. 1, fault current limiting units for dc systems are provided, the limiting units mainly include an insulating housing 1, an insulating partition 2, an anode electrode 3, a cathode electrode 4, a main flow hole 5, a liquid metal 6 and an auxiliary discharge circuit 7, wherein the anode electrode 3 and the cathode electrode 4 are made of copper, the anode electrode 3 and the cathode electrode 4 are symmetrically disposed on two side walls of the insulating housing 1, and form a sealed cavity with the insulating housing 1, the insulating partition 2 is vertically disposed in the cavity, the main flow hole 5 for carrying a long-time large rated flow is disposed in the middle of the insulating partition 2, the main flow hole 5 is a circular through hole and has a larger aperture, the liquid metal 6 is partially filled in the cavity, the filling height of the liquid metal 6 is higher than the main flow hole 5 on the insulating partition 2, and the auxiliary discharge circuit 7 is not required to be filled with the whole cavity, the auxiliary discharge circuit 7 is connected in parallel with the anode electrode 3 and the cathode electrode 4, wherein the auxiliary discharge circuit is mainly composed of a thyristor, a pre-charging device, a pre-charging.
When the direct current system works normally, a current main loop under a normal working state is formed when current passes through the liquid metal 6 on the two sides of the insulating partition plate 2 and passes through the main through hole 5. When a system short-circuit fault occurs, the auxiliary discharge circuit 7 is quickly conducted to generate short-time pulse current and forms a current branch circuit during the short-circuit fault after being superposed with fault current generated by the main circuit.
In preferred embodiments, the diameter of the main through-flow aperture 5 is equal to or greater than 15 mm.
In this embodiment, since the main through-flow hole has a small aperture and cannot bear rated through-flow, the main through-flow hole 5 in the present invention has a large aperture, and can ensure to bear large-current rated through-flow for a long time. When the direct current system normally works, the liquid metal 6 on the two sides of the insulating partition plate 2 passes through the main through hole 5, and the current is conducted after passing through the main through hole and the liquid metal. In the example, experiments prove that the aperture is larger than or equal to 15mm and can bear long-time large-current rated through current when the rated through current is 1.8kA or below. More preferably, when the rated current is 1.8kA, the aperture equal to 15mm can bear the rated current with long-time large current. It should be noted that the aperture of the present invention is selected according to the rated current to be carried, and it is obvious to those skilled in the art that the aperture of the present invention can be selected according to the rated current to be carried without departing from the concept of the present invention, and these variations and modifications are all within the protection scope of the present invention.
In preferred embodiments, the fault current limiting unit further comprises a controller for identifying the fault current and triggering the auxiliary discharge loop 7 to conduct.
In this embodiment, when the dc system is operating normally, the thyristor in the auxiliary discharge circuit 7 is in an off state, and the liquid metal 6 on both sides of the insulating partition plate 2 passes through the main through hole 5, so that the main circuit current is conducted. When a system short-circuit fault occurs, fault current is identified through a controller, a thyristor of an auxiliary discharge loop is triggered to be rapidly conducted, LC oscillation of the auxiliary discharge loop generates short-time pulse current with instantaneous high rising rate, fault current of a main loop is overlapped, large current higher than the rising rate of the fault current passes through a main through hole 5, arc striking is rapidly contracted to establish reverse arc voltage to limit short-circuit current, and then the rapid response and efficient current limiting of a fault current limiting unit when the short-circuit fault occurs are achieved by utilizing a liquid metal magnetic contraction principle.
In preferred embodiments, the liquid metal 6 is gallium indium tin alloy, which is liquid at room temperature.
The invention also provides methods for limiting current by using the fault current limiting unit, which are used for implementing different operations under the two conditions of normal operation and short-circuit fault of the direct current system.
When the direct current system normally works, the auxiliary discharge loop 7 is in a disconnected state, the liquid metal 6 on two sides of the insulating partition plate 2 passes through the main through hole 5, at the moment, all current flows through the main through hole, and the main loop is conducted. The main through-flow hole 5 has a large aperture, and the on-state resistance is small after liquid metal is filled, so that the loss generated by the fault current limiting unit is small when the system normally runs.
When a system short-circuit fault occurs, fault current is identified through the controller and the auxiliary discharge loop 7 is triggered to be conducted. The thyristor of the auxiliary discharge loop 7 is rapidly conducted, LC oscillation of the auxiliary discharge loop generates short-time pulse current with high rising rate, fault current of the main loop is superposed, large current higher than the rising rate of the fault current passes through the main through hole 5, arc striking is rapidly contracted to establish reverse arc voltage, and then the short-circuit current is limited by the arc voltage, so that rapid and efficient current limiting is realized.
According to the liquid metal magnetic shrinkage principle, the method can reduce the pre-arc time of the liquid metal magnetic shrinkage arcing of the main through hole, the main through hole can quickly strike an arc, and reverse arc voltage can be quickly established after the arc is struck, so that the fault current of the system is inhibited, and the effect of quickly limiting the current is achieved.
In the invention, the pre-arc time of the fault current limiting unit can be determined by the aperture of the main through hole and the pre-charging capacitance value, the capacitance charging voltage and the inductance value of the auxiliary discharging loop, and the arc voltage of the fault current limiting unit can be controlled by the aperture of the main through hole. Therefore, in the specific implementation of the invention, the aperture of the main through hole, the capacitance value of the capacitor to be precharged, the charging voltage of the capacitor, the inductance value and the like can be respectively selected according to different actual requirements, so that the fault current limiting unit can effectively inhibit the system fault current according to different conditions, and the beneficial effect of fast and efficient current limiting is achieved.
The above description is only a preferred embodiment of the present invention and should not be interpreted as limiting the scope of the present invention, it should be noted that those skilled in the art can make various changes and modifications without departing from the spirit of the present invention, and these changes and modifications should fall within the protection scope of the present invention.
Claims (10)
1, A fault current limiting unit for a DC system,
the limiting unit comprises an insulating shell (1), an insulating partition plate (2), anode electrodes (3), cathode electrodes (4), a main through flow hole (5), liquid metal (6) and an auxiliary discharge loop (7);
the high-power high-voltage power supply comprises anode electrodes (3) and cathode electrodes (4), wherein the anode electrodes (3) and the cathode electrodes (4) are symmetrically arranged on two side walls of an insulating shell (1) and form a closed cavity with the insulating shell (1), insulating partition plates (2) are vertically arranged in the cavity, main through holes (5) used for bearing long-time high-current rated through flow are formed in the middle of each insulating partition plate (2), liquid metal (6) is partially filled in the cavity, and an auxiliary discharge loop (7) is connected with the anode electrodes (3) and the cathode electrodes (4) in parallel;
when the current passes through the liquid metal (6) on the two sides of the insulating partition plate (2) and the main through hole (5), a current main loop under a normal working state is formed; the auxiliary discharge loop (7) is conducted to generate short-time pulse current and is superposed with fault current generated by the main loop, large current higher than the rise rate of the fault current is generated to pass through the main through hole (5), and the large current is rapidly contracted to initiate arc to establish reverse arc voltage, so that a current branch circuit during short-circuit fault is formed.
2. The fault current limiting unit according to claim 1,
the auxiliary discharge loop (7) comprises a thyristor, an inductor and a pre-charge capacitor, wherein the thyristor and the inductor are connected with each other
The inductor and the pre-charging capacitor are sequentially connected in series.
3. The fault current limiting unit according to claim 1,
the main through hole (5) is a circular through hole.
4. Fault current limiting unit according to claim 3,
the diameter of the main through hole (5) is larger than or equal to 15 mm.
5. The fault current limiting unit according to claim 1,
the limiting unit further comprises an controller for identifying a fault current and triggering the auxiliary discharge circuit (7) to conduct.
6. The fault current limiting unit according to claim 1,
the anode electrode (3) and the cathode electrode (4) are made of copper.
7. The fault current limiting unit according to claim 1,
the filling height of the liquid metal (6) is higher than that of the main through flow hole (5) in the insulating partition plate (2), and the whole cavity does not need to be filled.
8. The fault current limiting unit according to claim 1,
the liquid metal (6) is gallium indium tin alloy.
9, a method for limiting a current using the fault current limiting unit of any of claims 1 to 8 , the method comprising:
when the direct current system works normally, the auxiliary discharge loop (7) is in a disconnected state, current passes through the liquid metal (6) on the two sides of the insulating partition plate (2) and the main through hole (5), and the main loop is conducted; when a system short-circuit fault occurs, the auxiliary discharge loop (7) is rapidly conducted and generates short-time pulse current with high rising rate, fault current of the main loop is superposed, large current higher than the rising rate of the fault current passes through the main through hole (5), arc striking is rapidly contracted to establish reverse arc voltage, and then the arc voltage is utilized to limit the short-circuit current, so that rapid and efficient current limiting is realized.
10. The method of limiting current according to claim 9,
when a system short-circuit fault occurs, fault current is identified through the controller, and the auxiliary discharging loop (7) is triggered to be conducted.
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| CN201810554283.2A CN108711841B (en) | 2018-05-31 | 2018-05-31 | fault current limiting unit and method for direct current system |
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| CN201810554283.2A CN108711841B (en) | 2018-05-31 | 2018-05-31 | fault current limiting unit and method for direct current system |
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| CN109995006B (en) * | 2019-03-07 | 2020-01-31 | 西安交通大学 | liquid metal fault current limiter and its current limiting method |
| CN112531633B (en) * | 2020-11-24 | 2023-03-17 | 武汉船用电力推进装置研究所（中国船舶重工集团公司第七一二研究所） | Forced commutation loop and method of direct current breaker |
| CN112786327B (en) * | 2021-01-28 | 2022-02-18 | 西南交通大学 | Composite energy dissipation device |
| CN114944642B (en) * | 2022-06-09 | 2023-05-30 | 西南交通大学 | Compound energy consumption device based on liquid metal |
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| GB8803786D0 (en) * | 1988-02-18 | 1988-03-16 | Secr Defence | Electrical switch & electromagnetic projectile launcher incorporating switch |
| CN101741074B (en) * | 2008-11-12 | 2012-11-14 | 苏俊连 | Ship electricity fault current restrictor |
| CN202067716U (en) * | 2011-05-12 | 2011-12-07 | 东北大学 | Double-fluid circuit breaker capable of realizing remote control by using electromagnet |
| CN106026059B (en) * | 2016-06-29 | 2018-06-29 | 西安交通大学 | A kind of liquid metal current-limiting apparatus and method based on insulation barrier |
| CN107248729B (en) * | 2017-06-30 | 2019-01-04 | 国网陕西省电力公司电力科学研究院 | A kind of liquid metal current-limiting apparatus and method |
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