CN106707083A - Substation direct current grounding detecting device - Google Patents

Substation direct current grounding detecting device Download PDF

Info

Publication number
CN106707083A
CN106707083A CN201611238547.0A CN201611238547A CN106707083A CN 106707083 A CN106707083 A CN 106707083A CN 201611238547 A CN201611238547 A CN 201611238547A CN 106707083 A CN106707083 A CN 106707083A
Authority
CN
China
Prior art keywords
module
direct current
voltmeter
air switch
transforming plant
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
CN201611238547.0A
Other languages
Chinese (zh)
Inventor
王江涛
崔宇
冉然
曹磊
孟睿铮
乔辉
芦佳硕
葛嫚
李德清
张罡帅
唐凡
伍艳
侯骁
张毅静
王达飞
秘吉喆
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
State Grid Corp of China SGCC
State Grid Hebei Electric Power Co Ltd
Baoding Power Supply Co of State Grid Hebei Electric Power Co Ltd
Original Assignee
State Grid Corp of China SGCC
State Grid Hebei Electric Power Co Ltd
Baoding Power Supply Co of State Grid Hebei Electric Power Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by State Grid Corp of China SGCC, State Grid Hebei Electric Power Co Ltd, Baoding Power Supply Co of State Grid Hebei Electric Power Co Ltd filed Critical State Grid Corp of China SGCC
Priority to CN201611238547.0A priority Critical patent/CN106707083A/en
Publication of CN106707083A publication Critical patent/CN106707083A/en
Pending legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/62Testing of transformers

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Testing Electric Properties And Detecting Electric Faults (AREA)

Abstract

The invention discloses a substation direct current grounding detecting device, and relates to the substation inspection and maintenance technology field. The substation direct current grounding detecting device comprises a case body; a direct current air switch, an input module, an output module, a voltmeter module, and a fixing device, which are disposed in the case body. The voltmeter module comprises a first voltmeter module and a second voltmeter module. The output end of the input module is connected with the input end of the first voltmeter module, and the output end of the first voltmeter module is connected with the direct current air switch. The direct current air switch is connected with the input end of the second voltmeter module, and the output end of the second voltmeter module is connected with the output module. The output module is connected with the fixing device, which comprises a binding post and a fastening bolt, and is used for fixed connection with a testing wire. By adopting the above mentioned structure, under a condition of not cutting off power of a protection device, various direct current grounding fault points are searched quickly. The substation direct current grounding detecting device has advantages of simple operation, portability, and abilities of improving accuracy and operation efficiency of operators, and guaranteeing safe operation of power grid.

Description

A kind of transforming plant DC ground detection device
Technical field
The present invention relates to station technical field, more particularly to a kind of transforming plant DC ground detection device.
Background technology
In actual electric network running, DC system fault may cause the exception of protection, cause protection device malfunction or Tripping.In practical operation, search DC earthing and typically take the searching of drawing road, the method for branch process.It is straight by measurement first Stream voltage-to-ground determines the polarity of earth fault, the reason for coarse analysis failure occurs.Then reduced with " subnetting method " and check model Enclose, i.e., for the branch of double circuit power supply, such as direct current divides electric screen or small bus, and paired running side is converted to by split operation mode Formula, by direct current service entrance switch by all load switchings to same dc source, to judge that this sub-load whether there is Problem with grounding, by fault branch range shorter, finally checks that each branch has fault-free with " wink stops method " and " transfer load method ".This There is very big potential safety hazard in method, and flow is complicated, and time-consuming, and technical merit and the energy requirement to protecting personnel are higher. Especially DC earthing takes place frequently in thunderstorm weather, it is prone to short circuit grounding failure, searches protection device during DC earthing Power-off increase protection device malfunction or tripping risk, be unfavorable for the safe and stable operation of power network.
The content of the invention
The technical problem to be solved in the present invention is directed to above-mentioned the deficiencies in the prior art, there is provided a kind of transforming plant DC ground connection Detection means, quickly can search multiple spot failure point of DC grounding, simple to operate, carrying side in the case where protection device is not powered off Just, the accuracy rate and operating efficiency of operating personnel are improve, the safe operation of power network has been ensured.
In order to solve the above technical problems, the technical solution used in the present invention is:
A kind of transforming plant DC ground detection device, including:Casing and the direct current air switch positioned at box house, input mould Block, output module, voltmeter module and fixing device, voltmeter module include first voltage table module and second voltage table mould Block, the output end of input module is connected to the input of first voltage table module, and the output end of first voltage table module is connected to Direct current air switch, direct current air switch is connected to the input of second voltage table module, the output end of second voltage table module It is connected on output module, output module is connected to fixing device, and fixing device includes binding post and fastening bolt, for fastening Joint test line.
Used as further technical scheme, the casing top has folding handle, facilitates operating personnel to carry the dress Put.
Used as further technical scheme, the input module includes positive and negative two binding posts.
Used as further technical scheme, two binding posts of the input module are connected on direct current cabinet.
Used as further technical scheme, the output module includes positive and negative two binding posts.
Used as further technical scheme, described device also includes Special wire-clip, direct current wiring contact pin and wiring opening fork, Special wire-clip is reliably connected on lower mouth and direct current point electric screen binding post of air switch;It is straight that direct current wiring contact pin is used for device Bypass direct current is connected on terminal block when stream air switch is difficult wiring;Pitch for being connected on direct current cabinet upper terminal row, structure wiring opening Into electric power loop.
A kind of method used by transforming plant DC ground detection device, including:
Using " subnetting method " makes one section of DC bus-bar voltage normal work;
Attachment means, judge two numerical value of voltmeter module;
When the numerical value of two voltmeter modules is consistent, close direct current air switch, disconnects protection device power switch;
Each branch road load is moved into normal bus one by one, judges this branch road with the presence or absence of ground connection according to DC bus-bar voltage change Point.
It is using the beneficial effect produced by above-mentioned technical proposal:The present invention passes through a kind of transforming plant DC earthing detection Device, quickly can search multiple spot failure point of DC grounding in the case where protection device is not powered off, simple to operate, easy to carry, The accuracy rate and operating efficiency of operating personnel are improve, the safe operation of power network has been ensured.
Brief description of the drawings
Fig. 1 is transforming plant DC ground detection device figure of the invention;
Fig. 2 is handgrips schematic diagram of the invention;
Fig. 3 is structure line graph of the invention;
Fig. 4 is the method and step figure of one embodiment of the present of invention.
In figure:1st, casing;2nd, direct current air switch;3rd, first voltage table module;4th, second voltage table module;5th, handle; 6th, direct current wiring contact pin;7th, wiring opening fork;8th, input module;9th, output module;10th, Special wire-clip;11st, direct current cabinet;12nd, it is solid Determine device;121st, binding post;122nd, fastening bolt.
Specific embodiment
The present invention is further detailed explanation with reference to the accompanying drawings and detailed description.
As shown in figure 1, be a kind of embodiment of transforming plant DC ground detection device of the invention, including:
Direct current air switch 2, input module 8, output module 9, voltmeter module including casing 1 and inside casing 1 and Fixing device, voltmeter module includes first voltage table module 3 and second voltage table module 4, and the output end of input module 8 is connected The input of first voltage table module 3, the output end of first voltage table module 3 is connected to direct current air switch 2, direct current air Switch 2 is connected to the input of second voltage table module 4, and the output end of second voltage table module 4 is connected on output module 9, Output module 9 is connected to fixing device 12, and fixing device 12 includes binding post 121 and fastening bolt 122, for being fastenedly connected examination Test line.
As shown in Fig. 2 casing top has folding handle 5, operating personnel are facilitated to carry the device.Casing top is provided with Two relative plastic handles 5, handle 5 is connected by handle support with the top movable of casing 1, and when not using usually, handle 5 is flat The top of casing 1 is placed on, when carrying the device when to carry, two handles can be holded up and carried the device, two of which handle 5 The contact area with hand can be increased, disperse the pressure of opponent, while when one of handle 5 can also be prevented to break down, another Handle 5 can temporarily using once.The material of handle 5 is plastic material, low cost and quality is good, and use time is long and not rapid wear It is bad.
As shown in figure 3, the input module 8 includes positive and negative two binding posts 121, two binding posts 121 of input module 8 It is connected on direct current cabinet 11, the output module 9 also includes positive and negative two binding posts 121.
Described device also includes Special wire-clip 10, direct current wiring contact pin 6 and wiring opening fork 7, and Special wire-clip 10 is reliable to be connected It is connected on the lower mouth of air switch and direct current point electric screen binding post;Direct current wiring contact pin 6 is used for device direct current air switch not Bypass direct current is connected on terminal block during easy wiring;Wiring opening fork 7 is used to be connected on direct current cabinet upper terminal row, constitutes electric power loop.
One end of the Special wire-clip 10 is nut, 30-40mm of length;Nut profile is hexagonal prism, and deviates line ball The straight panel part certain angle of folder.This structure not only makes wire clamp be linked closely with the screw thread of conducting bolt to be integrally formed, be reliably connected On lower mouth and direct current point electric screen binding post of air switch, make electric current unimpeded, eliminate accident potential, and ensure that and apply Man-hour is time saving and energy saving, with stronger practicality.
Terminal block, means the terminal assemblies and the insulation division for fixing supporter for carrying multiple or multigroup mutually insulated Part.The effect of terminal block is exactly that will shield interior equipment to be connected with the circuit of screen external equipment, plays signal (Current Voltage) transmission Effect.Have terminal block so that wiring is attractive in appearance, it is easy to maintenance, it is mainly firm during connection between long distance is offline, construction and It is easy to maintenance.
Direct current wiring contact pin 6 is mainly with external connection, meets VCC and refers to that this connects positive source, and GND refers to ground connection(Electricity Source negative pole).
Voltmeter module includes first voltage table module 3 and second voltage table module 4, and input module 8 passes through first voltage Table module 3 is connected to direct current air switch 2, and direct current air switch 2 is connected on output module 9 by second voltage table module 4, Output module 9 is connected to fixing device 12, and fixing device 12 includes binding post 121 and fastening bolt 122, for being fastenedly connected examination Test line.
Direct current air switch 2 is used to be switched on or switched off dc source;Direct current input module 8 and direct current output module 9, use Code test line interface, for connecting DC loop line;3 and 4 is direct current input and output voltage table module, is shown in digital form Show input and output DC voltage, in the 2-in-1 two sections of DC voltages of monitoring of going forward of direct current air switch, prevent due to direct current both positive and negative polarity Reversed DC system fault when causing cyclization;The Special wire-clip 10 of independent development goes for being reliably connected in air switch On lower mouth and direct current point electric screen binding post;Bypass direct current is connected on when direct current wiring contact pin 6 is difficult wiring for device air switch In terminal block, wiring opening fork 7 is used to be connected on direct current cabinet upper terminal row, constitutes electric power loop.Can just be built by this instrument Vertical reliable bypass dc source, and suitable for the different direct current mode of connection of various transformer stations.
The present apparatus also includes Special test line, is placed on the Special test line storage area of transforming plant DC ground detection device, For operating personnel used when DC ground fault is detected.
A kind of method used by transforming plant DC ground detection device, methods described includes:
Using " subnetting method " makes one section of DC bus-bar voltage normal work;
Attachment means, judge two numerical value of voltmeter module;
When the numerical value of two voltmeter modules is consistent, close direct current air switch, disconnects protection device power switch;
Each branch road load is moved into normal bus one by one, judges this branch road with the presence or absence of ground connection according to DC bus-bar voltage change Point.
The transforming plant DC grounding monitoring device establishes a bypass direct current equivalent to for protection device in use Source.In substation field application, one section of DC bus-bar voltage is recovered normal first by " subnetting method ", there will be earth point All loops be directed on wherein one dc bus, each branch road load is moved one by one using transforming plant DC grounding monitoring device To normal bus, the change according to DC bus-bar voltage judges that this branch road whether there is problem with grounding.
Relay protection mainly uses element in power system to be short-circuited or electrical quantity (electric current, electricity during abnormal conditions Pressure, power, frequency etc.) change constitute the principle of relay protection action, also other physical quantitys, such as in oil tank of transformer therefore The a large amount of gas supervened during barrier and the increase of oil flow rate degree or increasing for oil pressure intensity.In most cases, not tube reaction Which kind of physical quantity, protective relaying device all includes measurement part (and definite value adjustment member), logical gate, executable portion.
Parameter (such as electric current, voltage, power-factor angle) in Operation of Electric Systems is in normal operation and failure situation There is significant difference.Protective relaying device is exactly, using the change of these parameters, electric power to be judged on the basis of reflection, detection The property and scope of the system failure, and then make corresponding reaction and treatment (such as sends warning signal or make circuit breaker trip Deng).
Protective relaying device is used to monitor the normal operation of power system, when protected power system component breaks down When, it should tripping operation life is quickly and accurately sent to the nearest breaker of disengaging fault element by the protective relaying device of the element Order, makes fault element be broken from power system in time, to reduce the damage to power system component in itself to greatest extent, drop The low influence powered to power system security.When the failure that system and equipment occur is enough to damage equipment or jeopardizes power grid security When, protective relaying device can to greatest extent reduce the damage to power system component in itself, reduce and power system security is supplied The influence of electricity.(such as:Single-phase earthing, light transformer, grave gas signal, transformer temperature rise are excessively high).
Protective relaying device can be also used for reacting the irregular working situation of electrical equipment, and according to irregular working feelings The difference of condition and equipment operation maintenance condition sends signal, points out person on duty to take measures rapidly, is allowed to recover normal as early as possible, or Automatically it is adjusted by device, or those are continued to run with can cause the electrical equipment of accident to be cut off.Reaction is abnormal The protective relaying device of working condition is allowed with certain deferred action.
Protective relaying device can be also used for realizing automation and the remote operation of power system, and it is industrial from Dynamic control.Such as:Automatic reclosing, alternate power autocast, remote control, remote measurement etc..
Loop is connected according to the mode of connection shown in Fig. 3, when D.C. voltmeter display numerical value is consistent, the direct current air that closes is opened Close 2, as protection device set up bypass dc source, be then turned off protection device power supply air switch, now protection device by DC earthing detection means is powered, and judges that this branch road whether there is earth point according to DC voltage change.
Use process:According to figure of turning on the electricity as shown in Figure 3, voltmeter module includes first voltage table module 3 and second Voltmeter module 4, input module 8 is connected to direct current air switch 2 by first voltage table module 3, and direct current air switch 2 passes through Second voltage table module 4 is connected on output module 9, and output module 9 is connected to fixing device 12, and fixing device 12 includes wiring Post 121 and fastening bolt 122, for being fastenedly connected test wire.
After turning on the electricity, one section of DC bus-bar voltage is recovered normal first by " subnetting method ", there will be earth point All loops are directed on wherein one dc bus, are moved to each branch road load one by one using transforming plant DC grounding monitoring device Normal bus, the change according to DC bus-bar voltage judges that this branch road whether there is problem with grounding.Using " subnetting method " makes one Section DC bus-bar voltage normal work;Loop is connected, two numerical value of voltmeter module are judged;When two numbers of voltmeter module When being worth consistent, close direct current air switch, disconnects protection device power switch;Each branch road load is moved into normal bus one by one, Judge that this branch road whether there is earth point according to DC bus-bar voltage change.Using the method, can one by one judge that each branch road is It is no to there is DC ground fault, the DC earthing defect elimination time is shortened, equipment availability is improve, ensure electric network reliability.
After adopting the above technical scheme, a kind of transforming plant DC ground detection device is provided, can be continuous in protection device Quick lookup multiple spot failure point of DC grounding, simple to operate, easy to carry in the case of electricity, improves the accuracy rate of operating personnel And operating efficiency, ensure the safe operation of power network.
Presently preferred embodiments of the present invention is the foregoing is only, is not intended to limit the invention, it is all in essence of the invention Any modification, equivalent and improvement made within god and principle etc., should be included within the scope of the present invention.

Claims (7)

1. a kind of transforming plant DC ground detection device, it is characterised in that:Including casing(1)With positioned at casing(1)Internal is straight Stream air switch(2), input module(8), output module(9), voltmeter module and fixing device(12), voltmeter module includes First voltage table module(3)With second voltage table module(4), input module(8)Output end be connected to first voltage table module (3)Input, first voltage table module(3)Output end be connected to direct current air switch(2), direct current air switch(2)Even It is connected to second voltage table module(4)Input, second voltage table module(4)Output end be connected to output module(9)On, it is defeated Go out module(9)It is connected to fixing device(12), fixing device(12)Including binding post(121)And fastening bolt(122), for tight It is solidly connected test wire.
2. a kind of transforming plant DC ground detection device according to claim 1, it is characterised in that the casing top has Folding handle(5), facilitate operating personnel to carry the device.
3. a kind of transforming plant DC ground detection device according to claim 1, it is characterised in that the input module bag Include positive and negative two binding posts(121).
4. a kind of transforming plant DC ground detection device according to claim 3, it is characterised in that the input module Two binding posts(121)It is connected to direct current cabinet(11)On.
5. a kind of transforming plant DC ground detection device according to claim 1, it is characterised in that the output module bag Include positive and negative two binding posts(121).
6. a kind of transforming plant DC ground detection device according to claim 1, it is characterised in that described device also includes Special wire-clip(10), direct current wiring contact pin(6)Pitched with wiring opening(7), Special wire-clip(10)It is reliably connected in air switch On lower mouth and direct current point electric screen binding post;Direct current wiring contact pin(6)By side when being difficult wiring for device direct current air switch Road direct current is connected on terminal block;Pitch wiring opening(7)For being connected on direct current cabinet upper terminal row, electric power loop is constituted.
7. the method used by a kind of transforming plant DC ground detection device as claimed in claim 1, it is characterised in that the side Method includes:
Using " subnetting method " makes one section of DC bus-bar voltage normal work;
Attachment means, judge two numerical value of voltmeter module;
When the numerical value of two voltmeter modules is consistent, close direct current air switch, disconnects protection device power switch;
Each branch road load is moved into normal bus one by one, judges this branch road with the presence or absence of ground connection according to DC bus-bar voltage change Point.
CN201611238547.0A 2016-12-28 2016-12-28 Substation direct current grounding detecting device Pending CN106707083A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201611238547.0A CN106707083A (en) 2016-12-28 2016-12-28 Substation direct current grounding detecting device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201611238547.0A CN106707083A (en) 2016-12-28 2016-12-28 Substation direct current grounding detecting device

Publications (1)

Publication Number Publication Date
CN106707083A true CN106707083A (en) 2017-05-24

Family

ID=58903012

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201611238547.0A Pending CN106707083A (en) 2016-12-28 2016-12-28 Substation direct current grounding detecting device

Country Status (1)

Country Link
CN (1) CN106707083A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113113907A (en) * 2021-04-08 2021-07-13 国网福建省电力有限公司 Direct current grounding fault positioning method based on source-load conversion technology

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6084755A (en) * 1998-10-08 2000-07-04 Schweitzer Engineering Laboratories, Inc. Protective relay-based monitoring system of DC power within an electric power substation
CN102636721A (en) * 2012-04-18 2012-08-15 孟州市电力公司 Ground fault detector for power transmission line
CN203339793U (en) * 2013-06-17 2013-12-11 国家电网公司 An apparatus for switching double DC power supplies in parallel
CN203811729U (en) * 2014-02-17 2014-09-03 中国南方电网有限责任公司超高压输电公司梧州局 Device for monitoring DC power supply of relay protection test power supply panel
CN106019049A (en) * 2016-05-19 2016-10-12 国网新疆电力公司伊犁供电公司 Auxiliary device for DC grounding search of transformer station
CN206281932U (en) * 2016-12-28 2017-06-27 国家电网公司 A kind of transforming plant DC ground detection device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6084755A (en) * 1998-10-08 2000-07-04 Schweitzer Engineering Laboratories, Inc. Protective relay-based monitoring system of DC power within an electric power substation
CN102636721A (en) * 2012-04-18 2012-08-15 孟州市电力公司 Ground fault detector for power transmission line
CN203339793U (en) * 2013-06-17 2013-12-11 国家电网公司 An apparatus for switching double DC power supplies in parallel
CN203811729U (en) * 2014-02-17 2014-09-03 中国南方电网有限责任公司超高压输电公司梧州局 Device for monitoring DC power supply of relay protection test power supply panel
CN106019049A (en) * 2016-05-19 2016-10-12 国网新疆电力公司伊犁供电公司 Auxiliary device for DC grounding search of transformer station
CN206281932U (en) * 2016-12-28 2017-06-27 国家电网公司 A kind of transforming plant DC ground detection device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113113907A (en) * 2021-04-08 2021-07-13 国网福建省电力有限公司 Direct current grounding fault positioning method based on source-load conversion technology
CN113113907B (en) * 2021-04-08 2022-08-05 国网福建省电力有限公司 Direct current grounding fault positioning method based on source-load conversion technology

Similar Documents

Publication Publication Date Title
CN103454498A (en) Insulation detection method of electric vehicle power battery pack
CN103116107A (en) High voltage direct current power source insulation monitoring device
CN103792505A (en) Ground fault simulation device for electric power direct current system
CN100495047C (en) Apparatus and method for measuring direct current branch insulation resistance utilizing unbalanced bridge
CN205792453U (en) A kind of distributed photovoltaic system online insulation against ground safety monitoring assembly
CN103675606B (en) Bridge-type DC Line Fault monitoring alarm
CN206281932U (en) A kind of transforming plant DC ground detection device
CN106093586B (en) Insulation resistance detection system and detection method for photovoltaic combiner box direct current system
CN204375298U (en) Demarcation switch Simulated training device
CN106018967A (en) On-line ground insulating security monitoring device for distributed photovoltaic system
CN203237059U (en) Static/dynamic online insulation monitoring device for high voltage power supply system of electric locomotive
CN203543694U (en) High voltage power distribution control device
CN108279360B (en) Single-phase earth fault line monitoring system
CN106707083A (en) Substation direct current grounding detecting device
CN210690728U (en) Direct current grounding test box
CN205210232U (en) Low pressure intelligence fault detector
GB2586343A (en) Power electronic converter with a ground fault detection unit that shares a common ground with both DC ports and AC ports
CN204166086U (en) A kind of multifunctional low-voltage line fault searches instrument
CN207067306U (en) For searching the servicing unit of DC system grounding point failure
CN206281921U (en) The positioner of failure in cabinet control loop
CN202522537U (en) Insulating tool edge planar defect on-site detection device
CN201662602U (en) Insulated on-line detection instrument of neutral point grounding high-voltage electric power system
CN2722265Y (en) DC grounding on-line tester
CN107561406A (en) It is a kind of based on fault line selection method for single-phase-to-ground fault of the multiterminal than width phase comparing method
CN203178394U (en) Direct current source system insulation monitoring device employing eccentric bridge technology

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination