CN106443293A - Direct current ground fault online detection and alarm device - Google Patents

Direct current ground fault online detection and alarm device Download PDF

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Publication number
CN106443293A
CN106443293A CN201610667961.7A CN201610667961A CN106443293A CN 106443293 A CN106443293 A CN 106443293A CN 201610667961 A CN201610667961 A CN 201610667961A CN 106443293 A CN106443293 A CN 106443293A
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CN
China
Prior art keywords
alarm
circuit
ground fault
microprocessor
line checking
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
CN201610667961.7A
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Chinese (zh)
Inventor
王昭雷
马兰
许磊
张会贤
张炜琦
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
Maintenance Branch of State Grid Hebei Electric Power Co Ltd
Original Assignee
State Grid Corp of China SGCC
Maintenance Branch 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, Maintenance Branch of State Grid Hebei Electric Power Co Ltd filed Critical State Grid Corp of China SGCC
Priority to CN201610667961.7A priority Critical patent/CN106443293A/en
Publication of CN106443293A publication Critical patent/CN106443293A/en
Pending legal-status Critical Current

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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

Abstract

The present invention discloses a direct current ground fault online detection and alarm device, belonging to the fault detection field. The device comprise a leakage current detection module, an A/D conversion circuit, a microprocessor, an alarm threshold value control module, an audio frequency and sound control circuit and a sound-light alarm circuit. The input end of the leakage current detection module is installed at the direct current power incoming terminal of the load, the output end of the leakage current detection module is accessed to the microprocessor through the A/D conversion circuit, the microprocessor is in both-way connection with the alarm threshold value control module, and the output end of the microprocessor is accessed to the input end of the sound-light alarm circuit through the audio frequency and sound control circuit. According to the invention, the direct current ground fault online detection and alarm device can accurately locate the ground fault branches and the ground faults in the condition that a device is not powered out.

Description

A kind of DC ground fault on-line checking and alarm device
Technical field
The present invention relates to a kind of DC ground fault on-line checking and alarm device, belong to field of fault detection.
Background technology
Straight-flow system is one of power plant, transformer station and communication base station important component part, be one complicated many Branching networks, it is advertiser, protective relaying device, control device and emergency lighting equipment in power system and communication system There is provided working power Deng important load.The working condition quality of straight-flow system will directly affect the peace of power system and communication system Entirely, functions reliably and efficiently run.DC ground fault is the modal fault of straight-flow system, is likely to result in control loop and relay is protected The malfunction of protection unit, tripping, burn out relay tip and fusing insurance etc., thus causing serious accident.Special for power plant It is hydroelectric power plant, because power house environment humidity leads to straight-flow system insulation against ground situation not so good, DC loop cable distribution is wide, first device Part is many, and trouble point is more difficult to search.After straight-flow system insulation declines, by the safe operation of impact gen-set control system.
Tradition searches the method that DC ground fault is " drawing road to find segment processing ", that is,:Follow operating portion after first signal Point, first indoor section carries out to straight-flow system drawing that road is found, the step of segment processing progressively determines which bar branch road connects behind outdoor Fault point methods found out by the artificial solution line of earth fault.Relay protection may be caused to fill because of direct current dead electricity when drawing ring current in short-term Put or automaton causes malfunction to trip due to the problem of interference free performance or failure criterion, detected using drawing direct current branch method The harm that trouble point is brought is very serious.Therefore the comprehensive letter of transmission of electricity [2001] 238 is sent out by National Electricity Co.《The unmanned value in hydroelectric power plant Some regulations of class》7.6.1 pointing out in bar:Forbid to take, in equipment runs, the method cutting DC load, search and process straight Stream earth fault.When with the test insulation of 500V megger, weak electrical loop is all exited, with anti-tamper.This method can not Trouble point is accurately positioned, fixes a breakdown and waste time and energy, make Field Force feel to have no way of doing it when searching DC earthing, Difficult.
In addition the shortcoming using bridge balance principle for the old-fashioned insulation monitoring and warning device is can not really to reflect the exhausted of dc bus Edge, can only reflect the uneven situation of positive and negative bus insulation resistance, and the grounding monitor relay in earthing detection loop makes mother The insulation resistance of line is limited in the level of 30k Ω.
In recent years, the method also branch road lookup being pressed using clamp on amperemeter.Because clamp on amperemeter detection sensitivity not Height is it is difficult to detect the earth fault of milliampere level.
And by the way of outside injection low frequency signal, then because the alternating component of injection can be by the storage of DC power system Battery and being affected by secondary circuit distribution capacity, does not progressively recommend.
Content of the invention
The technical problem to be solved there is provided electrical equipment during one kind enables to run and do not have a power failure and can The DC ground fault on-line checking being accurately positioned and alarm device.
The present invention adopts the following technical scheme that:
A kind of DC ground fault on-line checking and alarm device, it includes leakage current test module, A/D change-over circuit, Wei Chu Reason device, alarm threshold value control module, audio frequency and sound control circuit and sound light alarming circuit;Described leakage current test module defeated Enter the DC source end of incoming cables that end is arranged on load, the outfan of described leakage current test module connects through described A/D change-over circuit Enter microprocessor, described microprocessor is bi-directionally connected with alarm threshold value control module, the outfan of described microprocessor is through audio frequency And sound control circuit accesses the input of sound light alarming circuit.
Further, described leakage current test module includes induction coil and electromagnetic switching circuit, described induction coil pair The DC source end of incoming cables of each secondary circuit load should be arranged on, the output of described induction coil accesses electromagnetic switching circuit Input, the output of described electromagnetic switching circuit terminates the input of described A/D change-over circuit.
Further, described DC ground fault on-line checking and alarm device are separately mounted to the unidirectional current of each load Separate between source end of incoming cables, and each described DC ground fault on-line checking and alarm device, its quantity is according to load The corresponding configuration of number.
Further, described alarm threshold value control module includes by dual operational amplifier LM4558 and its peripheral component, It is the logic circuit for microprocessor computing.
Further, described audio frequency and sound control circuit include stereo IC chip LM4610 and its periphery unit Device.
Further, present invention additionally comprises energy-saving electric power, described energy-saving electric power is microprocessor power supply.
Further, described load includes switch cubicle, sealer and other control and any direct current of communication system is used Electric equipment.
Beneficial effects of the present invention are as follows:
The present invention is a kind of intelligent, high-precision DC ground fault on-line checking and alarm device, sets in enabling to run It is accurately positioned earth fault branch road and earth fault in the case of not having a power failure.It is different from other Distributed Monitoring and Control System, This device does not need to configure complicated communication and processing system, is directly installed on the DC source end of incoming cables of secondary circuit load, The real time on-line monitoring of this load circuit D.C. isolation situation can be realized, by this device of reasonable Arrangement, can conveniently realize straight The accurate positioning function of stream earth fault, thus realizing the quick lookup of fault and avoiding the fault harm drawing road investigation to bring.
The present invention is based on the uninterrupted monitoring function of real-time online, realizes to electrical equipment electric power loop DC ground fault Real-time online monitors.
The load of present invention detection can be that any direct current of switch cubicle, sealer and other controls and communication system is used Electric equipment;Separate between each DC ground fault on-line checking and alarm device, can be joined according to the number of load Put.Flexible configuration is installed, can reflect that DC loop whether there is short circuit or earth fault in time, can provide for professional Reliable, foundation of timely fixing a breakdown.
The present invention realizes the setting of threshold value and the audible and visual alarm of fault by built-in microprocessor, has simple, high-precision Degree and intelligentized feature.
Brief description
Fig. 1 is the structured flowchart of the present invention.
Fig. 2 is the logic relation picture of the present invention.
Fig. 3 is the fundamental diagram of the present invention.
Wherein, 1 DC ground fault on-line checking and alarm device.
Specific embodiment
For making the object, technical solutions and advantages of the present invention clearer, with reference to Fig. 1 ~ Fig. 3 and specific embodiment pair Invention carries out clear, complete description.
The present invention devises a kind of intelligent, high-precision DC ground fault on-line checking and alarm device, detection spirit Sensitivity is up to 0.2 milliampere it is adaptable to the direct-current secondary loop such as power plant, transformer station.Can be widely applied to power system transformer substation, The confession of the industrial and mining establishment such as fiery power plant, power station and colliery, iron and steel, metallurgy, chemical industry, join, electricity system.
The present invention is applied to 220V, 110V power supply system of DC source, and communication equipment 48V, 36V DC source is powered and is System.
As shown in Fig. 1 ~ Fig. 3, the present embodiment includes leakage current test module, A/D change-over circuit, microprocessor, warning level Value control module, audio frequency and sound control circuit and sound light alarming circuit;The input of described leakage current test module is arranged on The DC source end of incoming cables of load, the outfan of described leakage current test module accesses microprocessor through described A/D change-over circuit, Described microprocessor is bi-directionally connected with alarm threshold value control module, and the outfan of described microprocessor is through audio frequency and sound control electricity The input of sound light alarming circuit is accessed on road.
Further, described leakage current test module includes induction coil and electromagnetic switching circuit, described induction coil pair The DC source end of incoming cables of each secondary circuit load should be arranged on, the output of described induction coil accesses electromagnetic switching circuit Input, the output of described electromagnetic switching circuit terminates the input of described A/D change-over circuit.
Further, described DC ground fault on-line checking and alarm device are separately mounted to the unidirectional current of each load Separate between source end of incoming cables, and each described DC ground fault on-line checking and alarm device, its quantity is according to load The corresponding configuration of number.
Further, described alarm threshold value control module is included by dual operational amplifier LM4558 and its peripheral component.
Further, described audio frequency and sound control circuit include stereo IC chip LM4610 and its periphery unit Device.
Further, present invention additionally comprises energy-saving electric power, described energy-saving electric power is microprocessor power supply.
Further, described load includes switch cubicle, sealer and other control and any direct current of communication system is used Electric equipment.
As shown in figure 3, this device employing difference stream Cleaning Principle, the electric current I+ that arbitrary branch road is flowed out from positive source, After flowing through the whole load of this branch road, return the electric current I- of power cathode, when this branch road does not have earth fault, I+=I-, wears The electric current crossing this device is equal, and this device no signal exports.When occurring earth resistance to be Rd, earth current is the ground connection event of Ir During barrier, I+=I-+Ir, the electric current flowing through this device is unequal, and this device exports a signal reacting this difference, as Leakage current signal.
The major function of the present embodiment is as follows:
1)Real-time monitoring, is accurately positioned.
The DC leakage current of real-time monitoring place direct current branch, monitors this loop direct current insulation against ground state accordingly and connects Earth fault situation, and it is pin-pointed to fault branch.
2)Off-limit alarm, according to the difference of equipment and service condition, arranges off-limit alarm value by toggle switch;
3)There is multipath alarm function, during warning, display lamp flashes and with buzzer rings, facilitates operation maintenance personnel fast Earth point is looked in quick checking;
4)Signal memory return function, after electric current off-limit alarm, even if electric current is decreased below more limit value, alarm lamp and honeybee again Ring device be not turned off, need to through manually reset after ability shutdown signal.
The advantage of the present embodiment is as follows:
(1)The equipment that enables does not have a power failure, and is accurately positioned earth fault branch road and earth fault device.
(2)Save the manpower searching fault and time, effectively prevent Wu La road simultaneously.
(3)Safe and reliable property is high.There is not electrical connection in DC earthing positioner and external system, direct current is not supplied The electric loop produces any impact;
(4)The situation that multichannel branch road, many equipment are grounded simultaneously can be detected.
(5)AC signal need not be injected to straight-flow system, also will not increase straight-flow system ripple coefficient of voltage to direct current system The safe operation of system does not affect.By branch road, distribution capacity is not affected the earth resistance detecting over the ground.Do not affect direct current system Unite the normal operation of original insulating monitoring.
(6)Compact, structure are simple, it is easy to install.This direct-current ground indicator utilizes built-in chip microcontroller shape The detection of state and warning are it is not necessary to the monitoring system of external complex and wiring;Installed using standard clamping-rail, quickly and easily;
(7)Each direct-current ground indicator is separate, can be according to the increasing of the different requirements of system and straight-flow system load Subtract flexible configuration;
(8)Using large scale integrated chip (LSI chip) design, sealing structure moisture resistance is good, strong anti-interference performance, strong environmental adaptability.
(9)Sensitivity is high.This earth detector detection sensitivity can be looked into 0.1 milliampere than hand-held tong-type leakage current Look for mode more accurate, high resistance ground and insulation decline situation can be found;
(10)Earth point is searched rapid.Due to having indicated to earth element, therefore need not search in loop one by one, greatly save event The barrier lookup time.
(11)Quick for installation.By 2 jumper transition, you can this indicator of Fast Installation of realizing not having a power failure, to secondary Equipment and loop no affect.
(12)Also the data of indicator can be passed on the server of centralized control center by connection communication equipment, realize to many Individual transformer station direct current system DC earthing and the online remotely monitor of insulation status, are at the State Maintenance of straight-flow system and fault Reason provides foundation.
The main cause causing DC system grounding is:The insulation ag(e)ing of cable or device components, make moist, damaged and The fault that installation's power source plate is damaged.The straight-flow system of power plant and transformer station is many to be powered using 110V or 220V power supply, just, Negative busbar floating over the ground.When there is one-point grounding fault, due to not formed to earth-return, straight-flow system remains to keep normal Run, earth fault is difficult to discover.But, if with one or more ground connection other, will result in protective relaying device and control The malfunction of device processed or tripping.For avoiding this situation, current common practice be using collecting and distributing type monitoring system to insulation Situation carries out real time on-line monitoring, but this mode has the shortcomings of invest big, wiring is complicated and is easily disturbed.
Existing electrical secondary system is widely used Microcomputer Protection, intelligence interface(IED), the startup electricity of its internal drive relay Stream is usually milliampere level electric current, therefore, even the electric current that tens kilo-ohms of high resistance grounding is all possible to produce several milliamperes is led Cause malfunction or the tripping of secondary circuit, potential hazard is very big.
Electrical secondary system microelectronics technology, miniaturization result it is required that DC earthing detection means can delicately be reacted as little as 0.1 milliampere of leakage current.
The present embodiment adopts leakage current test technology for detection DC loop to whether there is earth fault, and small volume, is palm As size.The present embodiment is intelligentized High-accuracy direct current earthing detection instruction device, and detection sensitivity, up to 0.2 milliampere, is fitted For the direct-current secondary loop such as power plant, transformer station.Different from other Distributed Monitoring and Control System, in the present embodiment, DC earthing is fixed Position device does not need to configure complicated communication and processing system, and it is directly installed on the DC source inlet wire of secondary circuit load End, it is possible to achieve the real time on-line monitoring of this load circuit D.C. isolation situation, and by built-in chip microcontroller threshold value Set the audible and visual alarm with fault;There is simple, high accuracy and intelligentized feature.By this device of reasonable Arrangement, can be square Just realize the accurate positioning function of DC ground fault, thus realizing the quick lookup of fault and avoiding the event drawing road investigation to bring Barrier harm, significant for improving power grid security, stable, Effec-tive Function.
This device is connected in multiple loads respectively, independent mutually between it, by this DC load loop of on-line checking Leakage current is out-of-balance current, realizes this load is had or not with the judgement of DC earthing.
During normal operation, if no DC earthing, the leakage current through DC ground fault on-line checking and alarm device is Zero or less than setting alarm threshold value, direct-current ground indicator do not report to the police.
When DC earthing or insulation reduction in the load equipment powered by this device or circuit, through this device Leakage current will exceed alarm threshold value, now be reported to the police with buzzing and light flash mode.
The present embodiment enables equipment in operation and is accurately positioned earth fault branch road and ground connection event in the case of not having a power failure Barrier.
The present embodiment is realized by the following method:
1. adopt leakage current test technology for detection DC loop to whether there is leakage current, detection sensitivity is up to 0.1 ~ 0.2 milli Peace.
2. microprocessor is compared by loop leakage current test and with device setting alarm threshold value, and leakage current is zero or little In setting alarm threshold value, then do not report to the police.When the load equipment by DC ground fault on-line checking and alarm device or circuit When DC earthing or insulation reduction, the leakage current through this device will exceed alarm threshold value, now use buzzing and light to dodge Bright mode is reported to the police.
Finally it should be noted that:Above example only in order to technical scheme to be described, is not intended to limit;Although With reference to the foregoing embodiments the present invention is described in detail, it will be understood by those within the art that:It still may be used To modify to the technical scheme described in previous embodiment, or equivalent is carried out to wherein some technical characteristics;And These modifications or replacement, do not make the essence of appropriate technical solution depart from spirit and the model of embodiment of the present invention technical scheme Enclose.

Claims (6)

1. a kind of DC ground fault on-line checking and alarm device it is characterised in that:It includes leakage current test module, A/D Change-over circuit, microprocessor, alarm threshold value control module, audio frequency and sound control circuit and sound light alarming circuit;Described electric leakage The input of stream detection module is arranged on the DC source end of incoming cables of load, and the outfan of described leakage current test module is through described A/D change-over circuit accesses microprocessor, and described microprocessor is bi-directionally connected with alarm threshold value control module, described microprocessor Outfan accesses the input of sound light alarming circuit through audio frequency and sound control circuit.
2. DC ground fault on-line checking according to claim 1 and alarm device it is characterised in that:Described leakage current Detection module includes induction coil and electromagnetic switching circuit, and described induction coil correspondence is arranged on the straight of each secondary circuit load Stream power inleting terminal, the output of described induction coil accesses the input of electromagnetic switching circuit, described electromagnetic switching circuit defeated Go out the input terminating described A/D change-over circuit.
3. DC ground fault on-line checking according to claim 1 and 2 and alarm device it is characterised in that:Described straight Flow earth fault on-line checking and alarm device is separately mounted to the DC source end of incoming cables of each load, and each described direct current Separate between earth fault on-line checking and alarm device, its quantity is according to the corresponding configuration of number of load.
4. DC ground fault on-line checking according to claim 1 and alarm device it is characterised in that:Described warning level Value control module is included by dual operational amplifier LM4558 and its peripheral component.
5. DC ground fault on-line checking according to claim 1 and alarm device it is characterised in that:Described audio frequency and Sound control circuit includes stereo IC chip LM4610 and its peripheral component.
6. DC ground fault on-line checking according to claim 1 and alarm device it is characterised in that:It also includes saving Energy power supply, described energy-saving electric power is microprocessor power supply.
CN201610667961.7A 2016-08-15 2016-08-15 Direct current ground fault online detection and alarm device Pending CN106443293A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108535603A (en) * 2018-05-23 2018-09-14 安徽国电京润电力科技有限公司 A kind of power circuit automatic fault detection positioning system
CN110346675A (en) * 2019-06-27 2019-10-18 广东电网有限责任公司佛山供电局 Direct-current power supply earthing alarm unit

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101582585A (en) * 2009-06-02 2009-11-18 河北德普电器有限公司 Composite monitoring device for electrode difference protection and grounding of direct-current system
CN102129005B (en) * 2011-01-30 2013-06-05 重庆元虎科技有限公司 Transformer substation/power plant secondary circuit direct-current ground indicator and application thereof
CN203204114U (en) * 2013-05-08 2013-09-18 重庆艾派科斯科技有限公司 Direct current grounding alarm based on current detector with openings
CN204166081U (en) * 2014-10-24 2015-02-18 山东智洋电气股份有限公司 Straight-flow system insulating ground warning device
US20150106043A1 (en) * 2010-08-31 2015-04-16 Hitachi Automotive Systems, Ltd. Overcurrent Fault Detection Device for Electrical Drive Control System
CN204556765U (en) * 2015-05-07 2015-08-12 保定市科威电力科技有限公司 A kind of leakage current detect system
CN206002627U (en) * 2016-08-15 2017-03-08 国家电网公司 A kind of DC ground fault on-line checking and alarm device

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101582585A (en) * 2009-06-02 2009-11-18 河北德普电器有限公司 Composite monitoring device for electrode difference protection and grounding of direct-current system
US20150106043A1 (en) * 2010-08-31 2015-04-16 Hitachi Automotive Systems, Ltd. Overcurrent Fault Detection Device for Electrical Drive Control System
CN102129005B (en) * 2011-01-30 2013-06-05 重庆元虎科技有限公司 Transformer substation/power plant secondary circuit direct-current ground indicator and application thereof
CN203204114U (en) * 2013-05-08 2013-09-18 重庆艾派科斯科技有限公司 Direct current grounding alarm based on current detector with openings
CN204166081U (en) * 2014-10-24 2015-02-18 山东智洋电气股份有限公司 Straight-flow system insulating ground warning device
CN204556765U (en) * 2015-05-07 2015-08-12 保定市科威电力科技有限公司 A kind of leakage current detect system
CN206002627U (en) * 2016-08-15 2017-03-08 国家电网公司 A kind of DC ground fault on-line checking and alarm device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108535603A (en) * 2018-05-23 2018-09-14 安徽国电京润电力科技有限公司 A kind of power circuit automatic fault detection positioning system
CN110346675A (en) * 2019-06-27 2019-10-18 广东电网有限责任公司佛山供电局 Direct-current power supply earthing alarm unit

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Application publication date: 20170222