CN106340854A - Device for inhibiting direct current of AC transformer neutral point - Google Patents

Device for inhibiting direct current of AC transformer neutral point Download PDF

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Publication number
CN106340854A
CN106340854A CN201610801579.0A CN201610801579A CN106340854A CN 106340854 A CN106340854 A CN 106340854A CN 201610801579 A CN201610801579 A CN 201610801579A CN 106340854 A CN106340854 A CN 106340854A
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CN
China
Prior art keywords
current
neutral point
igbt
bypass protection
transformer neutral
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN201610801579.0A
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Chinese (zh)
Inventor
毛承雄
王丹
田杰
陆继明
雷子淦
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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Publication date
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Priority to CN201610801579.0A priority Critical patent/CN106340854A/en
Publication of CN106340854A publication Critical patent/CN106340854A/en
Pending legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00Emergency 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
    • H02H7/04Emergency 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 for transformers

Abstract

The invention provides a device for inhibiting a direct current of an AC transformer neutral point. The device comprises a block capacitor, a bypass protection circuit and a control circuit, wherein one end of the block capacitor is connected with the AC transformer neutral point, the other end of the block capacitor is in ground connection, the bypass protection circuit comprises n bypass protection units which are sequentially connected in parallel with two ends of the block capacitor, a positive input end of the control circuit is connected with the AC transformer neutral point, a negative input end of the control circuit is in ground connection, a control signal output end of the control circuit is connected with a control end of the bypass protection circuit, and an output end of the control circuit is used for connecting with an external AC system. A mechanical switch in the prior art has problems of short integral service life and poor performance caused by long closing time and the limited motion quantity, the device does not need the mechanical switch, and thereby service life and performance of the block device are improved.

Description

A kind of device of suppression AC transformer neutral point direct current
Technical field
The invention belongs to field of power, it is specifically related to a kind of suppression AC transformer neutral point direct current Device.This device can suppress DC current pass through AC transformer neutral point flow into electrical network, thus improve AC transformer with And the safety and reliability of electrical network.
Background technology
With greatly developing of D.C. high voltage transmission (hvdc), when straight-flow system adopt one pole ground return circuit or bipolar not When symmetrical circuit mode is run, the DC current producing in the earth will flow into AC transformer neutral point and lead to AC transformer Produce D.C. magnetic biasing.D.C. magnetic biasing can make AC transformer produce vibration, noise aggravation, temperature raise, reactive power consumption and The harm such as harmonic wave increase, are likely to result in power system relay protection system malfunction with time-harmonic wave increase.Therefore with regard to AC transformation The research of the D.C. magnetic biasing problem that device neutral point flows into DC current and leads to is paid much attention to always.Suppression AC transformer at present D.C. magnetic biasing scheme is roughly divided into three classes.The first kind is inverse injection current method, and embodiment is in AC transformer neutral point Add controllable voltage source or current source and the earth between, by kinetic measurement DC current, provide reverse electric current in real time.But The program is larger due to quantities, builds price and maintenance cost is higher.Equations of The Second Kind is neutral point series connected resistance, embodiment It is to add set resistor between AC transformer neutral point and the earth, program principle is simple, low cost.But there is also substantially Shortcoming, for example, can produce impact to relay protection system, and when electric network composition changes, resistance needs again to adjust, and the program is only DC current can be reduced can not eliminate.3rd class is neutral point serial capacitors method, embodiment be in AC transformer neutral point and Capacitor (abbreviation block capacitor) is added, the program can ensure that neutral point is effectively grounded between the earth, but simultaneously need to Prevent when fault in ac transmission system, huge short circuit current flows through neutral point, high transient voltage meeting is produced on block capacitor Damage block capacitor, raise AC transformer neutral point point position simultaneously and may damage AC transformer.
Three classes suppress the method for DC current respectively to have pluses and minuses.Consider inhibition and cost and maintenance etc. because Element, the 3rd class is neutral point serial capacitors method applied range.
Hvdc one pole the earth ruuning situation, usually just occurs under its system debug, initial operating stage or failure condition, because The frequency that this occurs is not very high, therefore can not put into every the block capacitor of straight device under normal circumstances.When exchange is detected Transformer neutral point contains and automatically engages block capacitor during DC current, after input if AC system occur simultaneously asymmetric Fault, then capacitor protector action in straight device, isolate block capacitor.After pending fault current vanishes, bypass protection Device exits, and block capacitor puts into operation again.In order to quickly protect, typically adopt high-voltage and high-power power electronic derailing switch , as very first time bypass elements, as main and follow-up bypass elements, such low cost reliability is high for mechanical switch simultaneously for part.
In current Chinese big and medium-sized cities, the track traffic such as subway because transport capacity strong, quick on schedule the advantages of obtain Arrive development energetically, currently the subway transportation of the overwhelming majority all adopts DC traction two-side feeding mode.In subway circulation mistake Cheng Zhong, metro traction electric substation transports electric energy by overhead contact line along the line to subway, locomotive pass through pantograph (collector shoe) with Overhead contact line (conductor rail) sliding contact and obtain electric energy, then be back to metro traction via the walking rails contacting with locomotive Electric substation.Completely insulated due to being difficult between track and the earth, therefore traction load electric current is not all along electric current locomotive Walking rails return metro traction electric substation, and must some electric current insulate poor local leakage in rail and the earth Flow into the earth, form stray electrical current.With being continuously increased of city middle orbit traffic, stray electrical current also can constantly become big, also gets over Come more complicated.When this part stray electrical current flows into AC transformer neutral point, can lead to every straight device frequent movement, particularly When containing mechanical switch in straight device, life-span and the performance of mechanical switch can be substantially reduced.
Content of the invention
For the defect of prior art, it is an object of the invention to provide a kind of suppression AC transformer neutral point direct current electricity It is intended to mechanical switch reclosure time itself is long in solution prior art, action frequency is limited to lead to whole device to the device of stream Short life, the problem of poor performance.
The invention provides a kind of device of suppression AC transformer neutral point direct current, comprising: block capacitor, side Road protection circuit and control circuit;One end of described block capacitor connects to AC transformer neutral point, described capacitance The other end ground connection of device;Described bypass protection circuit includes n bypass protection unit, is connected in parallel on described block capacitor successively Two ends;The positive input terminal of described control circuit connects to described AC transformer neutral point, the negative input end of described control circuit Ground connection, the control signal outfan of described control circuit connects to the control end of described bypass protection circuit, described control circuit Outfan be used for connect outside AC system, wherein, n is the positive integer more than or equal to 1.
Wherein, AC transformer can effectively suppress to flow into AC transformer by neutral point through block capacitor ground connection DC current.
Further, described bypass protection unit includes: the first IGCT scr11, the second IGCT scr12And current limliting Reactance;One end of described current-limiting reactor connects to described AC transformer neutral point, the other end of described current-limiting reactor connect to Described first IGCT scr11Anode and described second IGCT scr12Negative electrode;Described first IGCT scr11Negative electrode With described second IGCT scr12Anode be all grounded;Described first IGCT scr11Control pole and described second IGCT scr12Control pole be connected to the control signal outfan of described control circuit.
Further, described control circuit includes: breaking circuit and open circuit;Described breaking circuit is used for controlling side Road protection location terminates protection act, and described circuit of opening is used for controlling bypass protection unit to start protection act.
Further, described bypass protection unit includes: the first transistor igbt11, transistor seconds igbt12, current limliting Reactance and discharge resistance;One end of described current-limiting reactor connects to described AC transformer neutral point, described current-limiting reactor another One end connects to described the first transistor igbt11Drain electrode, described the first transistor igbt11Source electrode connect to described second Transistor igbt12Source electrode, described transistor seconds igbt12Grounded drain, described the first transistor igbt11Grid and Described transistor seconds igbt12Grid be all connected with outside control signal;One end of described discharge resistance connects to described One transistor igbt11Drain electrode, the other end of described discharge resistance connects to described transistor seconds igbt12Drain electrode.
Further, described discharge resistance is nonlinear resistance, and the material of described discharge resistance is zno or sic.
By the contemplated above technical scheme of the present invention, compared with prior art, because apparatus of the present invention save machinery Switch (mechanical switch reclosure time itself is long, and action frequency is limited), can obtain raising every straight device lifetime and performance Beneficial effect;Can also solve the problems, such as greatly to run, by hvdc one pole, the transformer neutral point DC magnetic biasing causing simultaneously.
Brief description
Fig. 1 is that the structure of the device of suppression AC transformer neutral point direct current that first embodiment of the invention provides is shown It is intended to;
Fig. 2 is that the device kind of the suppression AC transformer neutral point direct current that first embodiment of the invention provides controls electricity The structural representation on road;
Fig. 3 is that the structure of the device of suppression AC transformer neutral point direct current that second embodiment of the invention provides is shown It is intended to.
Specific embodiment
In order that the objects, technical solutions and advantages of the present invention become more apparent, below in conjunction with drawings and Examples, right The present invention is further elaborated.It should be appreciated that specific embodiment described herein is only in order to explain the present invention, and It is not used in the restriction present invention.
The present invention proposes a kind of new AC transformer neutral point every Nogata case, had both adapted to hvdc one pole the earth and has run Situation, it is also possible to adapt to this new situation, can more effectively protect AC transformer.Needle of the present invention to there being subway etc., hand in a large number by track The higher new isolation of a set of feasibility that the urban area (leading to every straight device frequent movement) of logical (stray electrical current is many) proposes Device, thus reduce the harm that AC transformer neutral point causes because of D.C. magnetic biasing.This device is protected by block capacitor, bypass Shield unit and control circuit are constituted, and propose two kinds of different topological structure for capacitor bypass protection location.Two kinds of knots Structure respectively has pluses and minuses, should select more suitably topological structure according to practical situation in different occasions.
Present invention is generally directed to be the area design that there is a large amount of track traffic (stray electrical current is many) such as subway in city A kind of new AC transformer neutral point DC current inhibitor proposing, can suppress to be handed over by the inflow that straight-flow system produces The DC current of convertor transformer neutral point, thus eliminate the D.C. magnetic biasing harm that AC transformer is caused.Be particularly suitable for by In Stray current values larger and complicated thus leading to AC transformer neutral point every straight device needs frequently QA area, Such as track traffic developed regions.This device may be equally applied to AC transformer neutral point isolation due to D.C. high voltage transmission with And the DC current problem that earth magnetism etc. causes.
The scheme of the suppression AC transformer neutral point direct current magnetic bias that the present invention adopts is neutral point serial capacitors method, additional side Road protection circuit, thus protect block capacitor by transient state high-voltage breakdown and AC transformer neutral point potential will be avoided to raise After threaten its safe operation.Bypass protector selects following two structures.
The first structure: the bidirectional thyristor solid-state switch being made up of current-limiting reactor and inverse-impedance type IGCT (scr) and control System (for triggering and cutoff thyristor) processed is constituted.Breaking circuit can be exactly simple electronic AC switch, work as major loop Be returned to normal condition need scr turn off enter block DC current state when, because major loop there may be DC current, Scr can not automatically shut down, therefore needs to assist breaking circuit.Close alternating-current switch when control system sends signal to breaking circuit, Remove scr trigger pulse, at this moment alternating current DC current that may be present with major loop is superimposed and can produce zero crossing electricity simultaneously Stream.When current zero-crossing point, scr can automatically shut down, and scr closes control system of having no progeny and sends signal disconnection exchange to breaking circuit Switch, scr turn off process completes.This breaking circuit desired volume is little, and low cost is simple and reliable, life-span length, can frequently move Make.
Second structure: the switch being made up of current-limiting reactor, discharge resistance and insulated gate bipolar tran sistor (igbt) Constitute with control circuit (triggering and shutoff igbt).Because igbt belongs to full control power electronic devices, therefore only need to compare stream Enter the DC current values of AC transformer neutral point and the size of DC current setting valve, to control igbt gate voltage to be open-minded Voltage or turn off voltage, thus control effective shutoff of igbt with open-minded.
Comparatively speaking, when using the first structure, the ducting capacity of bypass protection circuit is higher, and cost is lower, but Because scr cannot directly turn off the control breaking circuit it is therefore desirable to extra;When using second structure, can every straight device Control property is higher, but due to igbt self-characteristic, bypass protection circuit conducting electric current ability is not so good as the first structure, and cost is relatively simultaneously The first structure is higher.
The present invention is described in more detail below in conjunction with the accompanying drawings.The present invention proposes in a kind of new AC transformer Property point direct current current-limiting device, specific topological structure has two kinds of Fig. 1 and Fig. 3.
Fig. 1 (the first structure) breaker in middle k1 is AC transformer neutral-point solid ground disconnecting link, every straight device 1 by every straight (bypass protection unit is by bidirectional thyristor scr for capacitor c1, n group bypass protection unit in parallel11、scr12In parallel and current limliting is electric Anti- composition, when alternating current is in positive axis, alternating current is through scr11……scrn1Flow into the earth, when alternating current is in negative half During axle, alternating current is through scr12……scrn2Flow into the earth) and control system composition.The external limit of breaking circuit of control system Stream reactance is connected with AC system.Current-limiting reactor has two effects: one is to limit electric current fast lifting, when bypass protection unit is led Logical moment, current-limiting reactor limits di/dt, thus protection circuit device damages because suffering from instantaneous overcurrent or reduces the life-span;Two It is when in circuit, current value is excessive, the current-limiting reactor in bypass protection unit can play current balance function, thus protection circuit device Part.Bypass protection unit (providing it to turn on and off signal by control system) is mainly in block capacitor c1 excessively stream or overvoltage Shi Weiqi provides protection, prevents block capacitor from leading to because of transient state high pressure damage.
In parallel using n group bypass protection unit, can effectively reduce the electric current flowing through each protection location, thus reducing guarantor The requirement of shield device, practicability is higher simultaneously effectively to reduce installation cost.
Fig. 2 shows the structure of control system, including opening signal and breaking circuit two parts.In figure port 1 and port 2 It is connected to the two ends of block capacitor, port 3 connects door (g) pole of all scr.Breaking circuit is through current-limiting reactor and AC system Connect, so that protection turns off scr after terminating.
For bypass protection unit in the further description embodiment of the present invention, in conjunction with Fig. 1 and Fig. 2 in detail its work is described in detail Principle is as follows: when bypass protection unit starting protection act, opens signal output trigger pulse to scr in control system11、 scr12……scrn1、scrn2Gate pole makes all scr conducting, and fault current flows into the earth through bypass protection unit, thus protection every Straight capacitor.When bypass protection unit stops protection act, the breaking circuit in control system sends two kinds of signals and has been used for Become shutoff action.The first signal makes to open its output trigger pulse of signal interruption;Second signal makes alternating-current switch close, from And AC system is incorporated to protection device, and then all scr of rapid shutoff (i.e. bypass protection unit stops protection act).
Fig. 3 (second structure) breaker in middle k1 is AC transformer neutral-point solid ground disconnecting link, every straight device 2 by every straight (bypass protection unit is bipolar with the positive and negative insulation gate pole connecting by discharge resistance for capacitor c1, n group bypass protection unit in parallel Transistor npn npn igbt11、igbt12In series with current-limiting reactor, the positive and negative igbt connecting11、igbt12Electric current and electricity can be realized It is fully controllable that pressure flows to, and improves reliability and the safety of device) and control system composition.Bypass protection unit and current limliting electricity Anti- effect is identical with the first structure.Discharge resistance should select nonlinear resistance, and material typically selects zno or sic, Main Function Be prevent igbt be switched on or off moment generation overvoltage and lead to the damage of igbt, that is, control igbt both end voltage be less than Its maximum voltage value that can bear.Because igbt belongs to full control power electronic devices, so control circuit can directly control it Effectively open and turn off, so need not its breaking circuit individually designed.
For bypass protection unit in the further description embodiment of the present invention, in conjunction with Fig. 3 in detail its operation principle is described in detail As follows: when bypass protection unit starting protection act, control signal will be opened signal (high level) and export to igbt11、 igbt12……igbtn1、igbtn2Gate pole makes all igbt conductings, and fault current flows into the earth through bypass protection unit, thus protecting Shield block capacitor.When bypass protection unit stops protection act, control signal exports cut-off signals (low level) to institute Igbt gate pole is had to make igbt turn off (i.e. bypass protection unit stops protection act).
In embodiments of the present invention, the working condition a total of 4 of the device of suppression AC transformer neutral point direct current Kind: (1) unfaulty conditions (2) fault-free but DC current exceedes state of value of adjusting (3) malfunction (4) inspecting state.Specifically Including:
(1) when AC transformer is in unfaulty conditions, switch k1 closure, block capacitor c1 and bypass protection unit It is in non-operating state, AC transformer neutral-point solid ground, AC transformer and power system normally run.
(2) when AC transformer is in fault-free but DC current exceed adjust state of value when, switch k1 turn off, every directly electricity Container puts into operation, and control circuit controls bypass protection unit to be in non-operating state, and AC transformer neutral point is through every directly electricity Receptacle ground, suppression flows into the DC current of AC transformer by neutral point.
(3) when AC transformer is in malfunction, protection system detects overcurrent or overvoltage, and switch k1 closes Disconnected, control system controls bypass protection unit to be in running status simultaneously, and now block capacitor is shorted, and fault current is through side Road protection location flows into the earth, thus protecting block capacitor.After pending fault current vanishes, powered by control system, make side Road protection location stops protection act, further according to real-time detection result, plant running state is adjusted to state (1) or state (2).
(4) when AC transformer is in inspecting state, switch k1 closure, AC transformer neutral-point solid ground.Every Straight capacitor and bypass protection unit are in non-operating state, after the completion for the treatment of block capacitor electric discharge, device are overhauled.
The present invention is directed to AC transformer neutral point direct current magnetic bias problem and proposes new topological structure.Because device saves Removed mechanical switch, should every straight device can frequently quickly action, life-span and the performance every straight device can be improved simultaneously.
As it will be easily appreciated by one skilled in the art that the foregoing is only presently preferred embodiments of the present invention, not in order to Limit the present invention, all any modification, equivalent and improvement made within the spirit and principles in the present invention etc., all should comprise Within protection scope of the present invention.

Claims (5)

1. a kind of device of suppression AC transformer neutral point direct current is it is characterised in that include: block capacitor, bypass Protection circuit and control circuit;
One end of described block capacitor connects to AC transformer neutral point, the other end ground connection of described block capacitor;
Described bypass protection circuit includes n bypass protection unit, is connected in parallel on the two ends of described block capacitor successively;
The positive input terminal of described control circuit connects to described AC transformer neutral point, the negative input termination of described control circuit Ground, the control signal outfan of described control circuit connects to the control end of described bypass protection circuit, described control circuit Outfan is used for connecting the AC system of outside.
2. device as claimed in claim 1 is it is characterised in that described bypass protection unit includes: the first IGCT scr11, the Two IGCT scr12And current-limiting reactor;
One end of described current-limiting reactor connects to described AC transformer neutral point, and the other end of described current-limiting reactor connects to institute State the first IGCT scr11Anode and described second IGCT scr12Negative electrode;Described first IGCT scr11Negative electrode and Described second IGCT scr12Anode be all grounded;Described first IGCT scr11Control pole and described second IGCT scr12Control pole be connected to the control signal outfan of described control circuit.
3. device as claimed in claim 1 or 2 is it is characterised in that described control circuit includes: breaking circuit and open electricity Road;Described breaking circuit is used for controlling bypass protection unit to terminate protection act, and described circuit of opening is used for controlling bypass protection Unit starts protection act.
4. device as claimed in claim 1 is it is characterised in that described bypass protection unit includes: the first transistor igbt11、 Transistor seconds igbt12, current-limiting reactor and discharge resistance;
One end of described current-limiting reactor connects to described AC transformer neutral point, and the other end of described current-limiting reactor connects to institute State the first transistor igbt11Drain electrode, described the first transistor igbt11Source electrode connect to described transistor seconds igbt12's Source electrode, described transistor seconds igbt12Grounded drain, described the first transistor igbt11Grid and described transistor seconds igbt12Grid be all connected with outside control signal;
One end of described discharge resistance connects to described the first transistor igbt11Drain electrode, the other end of described discharge resistance is even It is connected to described transistor seconds igbt12Drain electrode.
5. device as claimed in claim 4 it is characterised in that described discharge resistance be nonlinear resistance, described discharge resistance Material be zno or sic.
CN201610801579.0A 2016-09-05 2016-09-05 Device for inhibiting direct current of AC transformer neutral point Pending CN106340854A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107147095A (en) * 2017-05-25 2017-09-08 华中科技大学 A kind of direct current and spuious harmonic current of suppressing is into the device of transformer neutral point
CN108711829A (en) * 2018-07-26 2018-10-26 沈阳工业大学 A kind of DC magnetic biasing suppression device and method with duplicate protection
CN111342449A (en) * 2020-03-07 2020-06-26 西南交通大学 Subway contact net surfing combination hybrid direct current circuit breaker
CN111404117A (en) * 2020-05-12 2020-07-10 广东电网有限责任公司惠州供电局 DC blocking device and control method thereof
CN111416332A (en) * 2020-03-16 2020-07-14 南方电网科学研究院有限责任公司 Suppression device for direct current

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Publication number Priority date Publication date Assignee Title
CN200976492Y (en) * 2006-11-24 2007-11-14 华中科技大学 Ground transformer neutral point DC current suppression device
CN102823121A (en) * 2010-02-03 2012-12-12 Abb技术有限公司 Switching module to limit and/or break the current of an electric power line
DE202013102112U1 (en) * 2013-05-15 2013-06-18 Georgiy M. Mustafa Device for earth fault current suppression in three-phase networks
CN103368168A (en) * 2013-07-24 2013-10-23 国家电网公司 Automatic switching transformer direct-current magnetic bias inhibiting device and control method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN200976492Y (en) * 2006-11-24 2007-11-14 华中科技大学 Ground transformer neutral point DC current suppression device
CN102823121A (en) * 2010-02-03 2012-12-12 Abb技术有限公司 Switching module to limit and/or break the current of an electric power line
DE202013102112U1 (en) * 2013-05-15 2013-06-18 Georgiy M. Mustafa Device for earth fault current suppression in three-phase networks
CN103368168A (en) * 2013-07-24 2013-10-23 国家电网公司 Automatic switching transformer direct-current magnetic bias inhibiting device and control method thereof

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107147095A (en) * 2017-05-25 2017-09-08 华中科技大学 A kind of direct current and spuious harmonic current of suppressing is into the device of transformer neutral point
CN108711829A (en) * 2018-07-26 2018-10-26 沈阳工业大学 A kind of DC magnetic biasing suppression device and method with duplicate protection
CN108711829B (en) * 2018-07-26 2023-10-27 沈阳工业大学 Direct-current magnetic bias suppression device and method with double protection
CN111342449A (en) * 2020-03-07 2020-06-26 西南交通大学 Subway contact net surfing combination hybrid direct current circuit breaker
CN111342449B (en) * 2020-03-07 2022-08-19 西南交通大学 Subway contact net surfing combination hybrid direct current circuit breaker
CN111416332A (en) * 2020-03-16 2020-07-14 南方电网科学研究院有限责任公司 Suppression device for direct current
CN111404117A (en) * 2020-05-12 2020-07-10 广东电网有限责任公司惠州供电局 DC blocking device and control method thereof

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Application publication date: 20170118