CN86201119U - Selectable electric leakage protector for mine low voltage net - Google Patents
Selectable electric leakage protector for mine low voltage net Download PDFInfo
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- CN86201119U CN86201119U CN 86201119 CN86201119U CN86201119U CN 86201119 U CN86201119 U CN 86201119U CN 86201119 CN86201119 CN 86201119 CN 86201119 U CN86201119 U CN 86201119U CN 86201119 U CN86201119 U CN 86201119U
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Abstract
The utility model discloses a selective electric leakage protector of mine low voltage electric network, characterized in that the selective electric leakage protector eliminates the misoperation of selective electric leakage which is caused in the transient state process of any electric network operation and enhances the reliability of the selective electric leakage protection of low voltage electric network. The device can not only achieve non-symmetrical selective electric leakage protection, but also have the functions of symmetrical electric leakage protection, selective electric leakage protection in support, displaying failure quality and displaying electric leakage branch circuit, realizing that testing and examining the electric leakage device without the power failure of electric network.
Description
Existing low voltage electric network earth leakage protective device non-selectivity exists several important disadvantages:
1. no matter this low voltage electric network leaks electricity, all cause this electrical network master switch tripping operation there, complete cause low voltage electric network to have a power failure.
2. do not know after having a power failure that the overcurrent reason still is the tripping operation of electric leakage reason, if the electric leakage reason does not know it is that branch road electric leakage yet? if find out the electric leakage branch road, combined floodgate heuristic commonly used, not only inconvenience but also incur loss through delay the production time is soundd out on fault branch and is also had certain danger.
3. safety regulations requires earth leakage protective device checkout facility every day, and every test once all causes 10～20 minutes power failure, influence the output of colliery digging footage and coal, surplus only an ore deposit of production loss just can reach ten every year ten thousand yuan.
In the application of existing earth leakage protective device, the leak detector test has a power failure and other distribution branch road of non-portable blower leaks electricity, and causes portable blower power failure blowing-out, and the safety of driving face in serious threat.Therefore, many high gassies adopt portable blower or the independently-powered mode of driving face.But the autonomous power supply system investment is too big, and every ore deposit needs the hundreds thousand of units of many investments.
Selective leakage protection device is the electric leakage of that branch road, that branch road tripping operation, and the branch road that not have to leak electricity not has a power failure and continues continuous power supply.Leak electricity and the branch road implementation leak current fault demonstration of tripping operation.Be that non-electric leakage branch road does not have a power failure, and the electric leakage branch road can be discerned at once.
Selective earth leakage protection can utilize the zero sequence power direction principle or be called residual voltage and zero-sequence current mutually the principle of bit comparison realize that it is being applied on the bigger high-voltage fence of zero-sequence current decades ago.Because of high-voltage fence and power supply neutral point when the low voltage electric network electric leakage of impedance earth, the residual voltage zero-sequence current is all bigger, realizes selective earth leakage protection easily, but it is difficult for realizing on the very little low-voltage power supply system of isolated neutral zero-sequence current.Zero-sequence current is very little during because of electric leakage, and the selective leakage protection device action must be very sensitive, and therefore the generation of any similar zero-sequence current under non-electric leakage situation all easily produces malfunction.Particularly require apace the multichannel power distribution net to be realized selectable earth leakage protective action, only when leaking electricity zero-sequence current and residual voltage mutually bit comparison be irrealizable., any operation transient process of electrical network easily causes malfunction because all having transient zero-sequence current to occur.The electrical network parameter excursion is very big under this external practical electrical network condition, the not equal phase relation that all influences between residual voltage and zero-sequence current of the difference of the electrical quantity that electrical network condition difference causes and drain conditions (resistance).Therefore the malfunction problem of practical selective earth leakage protection is the still irrealizable major obstacle of present power supply isolated neutral electrical network selective earth leakage protection.
The invention provides a kind of mining low voltage electric network property selected earth leakage protective device.
This device is by the coupling circuit of electrical network; Circuit measuring zero phase sequence current; Zero sequence voltage detection circuit; Phase-comparison circuit; The selective earth leakage protection executive circuit; The additional dc power supply electric-leakage detection circuit; The faulty action preventing exclusive circuit is differentiated in electric leakage; Electrical network do not have a power failure test check and the electric leakage display circuit; Main circuits such as symmetry earth leakage protective and selective leakage backup protection are formed, as shown in Figure 1.
The present invention is directed to the zero-sequence current that transient process produces under the non-electric leakage situation of electrical network and cause the earth leakage protective misoperation problem of the power supply isolated neutral low voltage electric network property selected, be provided with electric leakage and differentiate the faulty action preventing exclusive circuit.Electric leakage differentiates that the faulty action preventing locking can realize with multiple circuit, differentiates the earth leakage search/lockout circuit as additional dc power supply detection of electrical leakage relay; The electrical network transient high frequency exclusive circuit of the industrial frequency resonance tank circuit; Time-delay escapes the exclusive circuit of electrical network transient state etc.
This device has adopted additional dc power supply detection of electrical leakage relay to differentiate the exclusive circuit of electric leakage, sees Fig. 2.
This electric leakage differentiates that the faulty action preventing exclusive circuit mainly exports contact (OJ by the electric leakage discriminating relay of additional dc power supply (DC), electric leakage discriminating relay (OJ), electrical network coupling circuit (LU), capacitance (C) and latch-selective earth leakage protective link
n) form.According to the principle of additional dc power supply detection of grid electric leakage, to be not more than (the OJ of 50 milliseconds electric leakage discriminating relay
1) contact, to residual voltage or zero-sequence current or selective earth leakage protection executive circuit (ZX) implementation locking.Just allow residual voltage to compare when promptly having only grid power leakage or just connect the power supply of selective earth leakage protection executive circuit (ZX) with zero-sequence current.Under the situation that is not having electric leakage, electrical network resistance over the ground is very big, fail to start electric leakage discriminating relay (OJ), and any operation transient process of electrical network during promptly non-electric leakage is not because of locking all can make selective earth leakage protection generation misoperation.During electric leakage, electric leakage differentiates that faulty action preventing blocking relay OJ has electrolysis to remove locking, and the electric leakage branch road is carried out tripping operation.Trip performance element is (as nJ among Fig. 4
1-2Contact cuts off the residual voltage circuit) the interim function of carrying out anti-other branch road malfunction locking.Tripping operation back excision leak current fault, OJ
1Recover locking.Electrical network transient state has been crossed nJ
2Again with nJ
1-2The contact short circuit is carried out n-1 the latching relation under the line state.
The zero-sequence current of selective earth leakage protection detects, and available zero sequence power pack directly is enclosed within on the three-phase circuit of switch, but this needs transform the downhole anti-explosion switch, is extremely loaded down with trivial details and difficult and transform antiknock device.The present invention is designed to a kind of independently explosion-proof zero-sequence current converter, can directly be enclosed within the cable cover(ing) outside that comprises ground wire.The way of utilizing ground wire to turn back is once eliminated the influence that electric current detects the electrical network zero-sequence current in the ground wire, as shown in Figure 3.
Power pack is generally got its secondary load resistance both end voltage as signal.But because of varying in size of primary current, primary current is different with the phase difference of secondary voltage signal, and is prone to irregular sine wave, influences the phase bit comparison or easily causes the selective earth leakage protection malfunction.The present invention utilizes electric capacity to do the secondary load of zero-sequence current converter, the both end voltage signal is held in power taking, the phase difference of primary current and secondary voltage signal constant substantially (80 ± 5 degree) then, the size of the resistance of promptly leaking electricity or the size of primary current do not influence the phase angle of converter output signal.
Selective earth leakage protection is that the zero-sequence current that produces when utilizing grid power leakage is determined the electric leakage branch road with the bit comparison mutually of residual voltage, realizes selective earth leakage protection.But when the symmetry electric leakage takes place electrical network, there is not zero-sequence current, so selective earth leakage protection can not solve symmetrical electric leakage problem.In addition, also exist asymmetric electric leakage of a certain branch road and while to make the malfunctioning possibility of this branch road selective earth leakage protection for a certain reason.In order to address the above problem, can establish symmetrical earth leakage protective and selective leakage backup protection circuit.This circuit is made up of electric leakage discriminating relay (OJ), 0.2～0.5 second delay circuit (YS) and the contact of control (TQ) and (WY) thereof, as shown in Figure 2.When selective earth leakage protection was malfunctioning when taking place electric leakage of electrical network symmetry or asymmetry to leak electricity, electric leakage discriminating relay (OJ) starting through 0.2～0.5 second time-delay, was carried out jumping low pressure master switch (D by the contact of delay circuit outlet
0) or high-voltage switch gear (P), realize the symmetrical earth leakage protective that line insulation reduces, and as the backup protection of each branch road selective earth leakage protection.
To carry out test check to earth leakage protective device every day by the safety regulations requirement, but all cause grid power blackout during existing earth leakage protective device test check.For head it off, can establish electrical network do not have a power failure test check and the electric leakage display circuit.This circuit is carried out the contact (nJ of relay by test switch (SA) locking contact, selective earth leakage protection
1-2), have pressure release coil (TQ) and leakage detector (BG) to form, as shown in Figure 3.SA
2, nJ
1-2Insert electrical network with TQ series connection back.
The mining low voltage electric network property the selected earth leakage protective device that the present invention proposes has been realized only leaking electricity in the multichannel power distribution net, and branch road trips and the selective earth leakage protection of demonstration; Solved the malfunction problem that electrical network transient process under the non-electric leakage situation causes selective earth leakage protection; The backup protection function that also has electric leakage of electrical network symmetry and asymmetry electric leakage simultaneously; This device not only can used in new switch, also can not use under existing distribution system is not transformed the situation of its switch; Also can guarantee under the electrical network no cut-off condition, earth leakage protective device to be carried out checkout facility.This device can be discerned nature of trouble and electric leakage branch road rapidly, can shorten the processing time of leak current fault, can improve the continuity of power supply and the security performance in colliery again thereby can improve coal production.
Fig. 1 is mining low voltage electric network is selected property earth leakage protective device block diagram.
Fig. 2 leaks electricity and differentiates faulty action preventing locking and symmetry electric leakage and asymmetric electric leakage backup protection block diagram.
The DC--additional dc power supply
BHL--zero-sequence current converter
DY--electronic circuit power supply
The P--high-voltage switch gear
WY--does not have the pressure release coil
The KSJ--mining transformer
D
0--the electrical network master switch
D
1-Dn--power distribution network branch switch
TQ--has the pressure release coil
The YS--delay circuit
LU--electrical network coupling circuit and zero sequence voltage detection circuit
The OJ--discriminating relay that leaks electricity
The XM--phase-comparison circuit
ZX--selective earth leakage protection executive circuit
Fig. 3 electrical network does not have a power failure, and the test check earth leakage protective device shows with electric leakage and zero-sequence current converter elimination ground wire influences schematic diagram.
D
0--the electrical network master switch
D
1-Dn--power distribution network branch switch
TQ--has the pressure release coil
The SA--test switch
NJ
1-2--n branch road the earth leakage protective the 2nd is carried out contact
The BG--leakage detector
BHL--zero-sequence current converter
Fig. 4 is mining low voltage electric network is selected property earth leakage protective device schematic circuit.
Specific embodiments of the invention are as follows:
Electric leakage discriminating faulty action preventing exclusive circuit in this device is made up of electric leakage discriminating exclusive circuit and leakage tripping exclusive circuit.Electric leakage differentiates that exclusive circuit is by three-phase reactor (SK), zero-sequence reactor (LK), ohmmeter (M), electric leakage discriminating relay (OJ
1, OJ
2), additional dc power supply (OBG
2), potentiometer (OR adjusts
T), block capacitor (OC
1) and main earth electrode (ZD) composition.Its order of connection is by OBG
2(+) end begins to be connected in series OR
T, ZD enters the earth, gets back to three phase network by electrical network insulation against ground resistance, three terminals of three phase network are connected with the origin or beginning of three windings of SK respectively, three ends of winding are connected into neutral point, are connected in series LK, M, OJ again by neutral point
1, OJ
2Get back to OBG
2(-) end.Differentiate in the faulty action preventing exclusive circuit to have only when electrical network insulation against ground resistance is lower than setting (according to the China's coal mines safety regulations, 1140 volts of electrical networks are that 22K Ω, 660 volts of electrical networks are that 11K Ω, 380 volts of electrical networks are 3.5K Ω) in electric leakage, electric leakage discriminating relay (OJ
1) could start, connect the residual voltage sampling circuit of each branch road.And the residual voltage that any transitional circuit produces all can not make the insulation resistance of electrical network reduce, OJ
1Can not move, whether leak electricity, reach the purpose of normal running faulty action preventing thereby can identify electrical network.The leakage tripping exclusive circuit is by the coupling coil of zero-sequence reactor (LK), electric leakage discriminating relay (OJ
1) normal opened contact (OJ
1-A), the execution relay (nJ of each branch road
1) normally closed contact (nJ
1-2) and the residual voltage of each branch road inlet nR
6Form.Its order of connection is the coupling coil one end ground connection of LK, other end serial connection OJ
1--B, 1J
1-2～nJ
1-2To the P point, receive the 1R of each branch road respectively by the P point
6～nR
6On.Carry out relay nJ owing to seal in n electric leakage in this loop
1Normally closed contact nJ
1-2, any branch road electric leakage, the normally closed contact nJ of respective branch
1-2Disconnect the residual voltage sample circuit of other branch roads, avoided because the tripping operation of electric leakage branch road causes other branch road misoperations.After the transient process of electric leakage branch road tripping operation finishes, by electric capacity nC
5With relay nJ
2The normal opened contact nJ of the time-delay relay of forming
2Connect the residual voltage sampling circuit of other branch roads, recovered the normal selective earth leakage protection function of other branch roads.
Zero-sequence current converter (BHL) is made of a ring structure iron core and secondary winding, as shown in Figure 3.The selective earth leakage protection zero-sequence current detects available zero sequence power pack (BHL) and is enclosed within the cable cover(ing) outside that comprises ground wire and ground wire is turned back once, cable and the winding of the zero line that turns back as BHL.The secondary winding one end ground connection of zero-sequence current converter (BHL), the other end is connected on nC
2With nR
2Connecting line on, pass through nR
2Be defeated by zero-sequence current operational amplifier (nBG
2) positive input, zero-sequence current is amplified and shaping.
Phase-comparison circuit is made up of residual voltage output circuit and zero-sequence current output circuit, shown in the NO1 plate among Fig. 4.The zero-sequence current output circuit comprises that zero-sequence current square wave that electric capacity (C2), resistance (R2), operational amplifier (BG2) are formed forms zero-sequence current square wave differential circuit and resistance (R4), (R5), the triode (BG5) that circuit, electric capacity (C3), resistance (R3) form and forms the zero-sequence current output circuit.The residual voltage output circuit is made up of resistance (R6), (R7), (R8), triode (BG8).
The selective earth leakage protection executive circuit is carried out relay (1J by resistance (R9), triode (BG9), voltage-stabiliser tube (BG11), controllable silicon (BG14) and electric leakage
1) and (1J
2) constitute.
The principle of phase-comparison circuit and selective earth leakage protection executive circuit is: when electrical network just often; no residual voltage and zero sequence current signal; no residual voltage and the output of zero-sequence current square wave; triode (BG5) and (BG8) output high potential; triode (BG9) output electronegative potential, voltage-stabiliser tube (BG11) and not conducting of controllable silicon (BG14).Therefore control the electric leakage of power network switch and carry out relay (nJ
1) be failure to actuate.When asymmetric electric leakage occurring, the differentiated pulse of faulty circuit zero-sequence current is identical with the phase place of residual voltage, therefore when the differentiated pulse of faulty circuit zero-sequence current makes triode (BG5) conducting, residual voltage makes triode (BG8) conducting, triode (BG5) and (BG8) export electronegative potential simultaneously, triode (BG9) ends, triode (BG9) output high potential, make voltage-stabiliser tube (BG11) and controllable silicon (BG14) conducting, relay (nJ is carried out in electric leakage
1) action, make the tripping operation of electric leakage branch switch.Non-electric leakage branch road is because zero-sequence current phase difference 180 degree of the zero-sequence current of electric leakage branch road and leakproof branch road, therefore its zero-sequence current differentiated pulse and residual voltage square wave homophase not, triode (BG5) and (BG8) conducting simultaneously, triode (BG9) can not end, triode (BG9) output electronegative potential, relay (nJ is carried out in electric leakage
1) be failure to actuate.
Symmetry earth leakage protective and selective leakage backup protection circuit are by electric leakage discriminating relay (OJ
1), resistance (OR
4) (OR
5) and electric capacity (OC4) 0.2～0.5 second the delay circuit and voltage-stabiliser tube (OBG6), the controllable silicon (OBG8) that constitute carry out relay (OJ
1') and the control mains switch executive circuit that has the nothing of pressure release coil (TQ) or power supply high-voltage switch gear to press release coil (WY) to constitute form, as shown in Figure 4.When selective earth leakage protection is malfunctioning when electric leakage of electrical network symmetry or asymmetry electric leakage take place, electric leakage discriminating relay (OJ
1) starting, its contact (OJ
1-A) connect, through 0.2～0.5 second time-delay, by the contact (OJ of delay circuit outlet
1-1') or (OJ
1-2') carry out to jump low pressure master switch (ODW) or high-voltage switch gear (PB), realize the symmetrical earth leakage protective that line insulation reduces, and as the backup protection of each branch road selective earth leakage protection.
Electrical network does not have a power failure test check and electric leakage display circuit by the contact (nJ of test switch (SA) locking contact, selective earth leakage protection relay
1-2), leakage detector (BG) etc. forms as shown in Figure 3.Which branch road leaks electricity, and then the respective branch selective earth leakage protection is carried out the actuating of relay, connects the electric leakage display of respective branch, is that the tripping operation of electric leakage reason also can be determined the branch road that leaks electricity thereby can determine immediately.During the test check selective leakage protection device, control branch road test switch (SA) by the test check personnel, cause artificial ground, if protective device is normal, then this branch road is carried out relay (nJ
1) action corresponding electric leakage display (BG) demonstration.But power network switch does not trip, and this is because in control test switch (SA), its locking contact (SA
2) locking (cut-out) this trip circuit.
Claims (1)
1, a kind of mining low voltage electric network property selected earth leakage protective device of being made up of electrical network coupling circuit, zero sequence voltage detection circuit, circuit measuring zero phase sequence current, phase-comparison circuit and selective earth leakage protection circuit is characterized in that:
A, have electric leakage and differentiate the faulty action preventing exclusive circuit, this circuit differentiates that by electric leakage exclusive circuit and leakage tripping exclusive circuit form.Electric leakage differentiates that exclusive circuit is by three-phase reactor (SK), zero-sequence reactor (LK), ohmmeter (M), electric leakage discriminating relay (OJ
1, OJ
2), additional dc power supply (OBG
2), potentiometer (OR adjusts
T), block capacitor (OC
1) and main earth electrode (ZD) composition.The order of connection of this circuit is by OBG
2(+) end begins to be connected in series OR
T, ZD enters the earth, gets back to electrical network by electrical network insulation against ground resistance, the three-phase termination of electrical network is connected on the top of three windings of SK respectively, the end of three windings is connected together becomes neutral point serial connection LK, M, OJ
1, OJ
2, get back to OBG
2(-) end.The leakage tripping exclusive circuit is the coupling coil by zero-sequence reactor (LK), electric leakage discriminating relay (OJ
1) normal battle of (OJ
1-A), the execution relay (nJ of each branch road
1) normally closed contact (nJ
1-2) and the residual voltage of each branch road inlet nR
6Form.Its order of connection is the coupling coil one end ground connection of LK, other end serial connection OJ
1-B, 1J
1-2～nJ
1-2To the P point, receive the 1R of each branch road respectively by the P point
6～nR
6On.
B, have symmetrical earth leakage protective and asymmetric electric leakage backup protection circuit.This circuit is by DC power supply (OBG
3), 0.2～0.5 second delay trigger circuit and carry out relay (OJ
' 1) form.Its order of connection is with electric leakage discriminating relay (OJ
1) another normal opened contact (OJ
1-A) one terminate at voltage-stabiliser tube (OBG4) and resistance (OR
3) connecting line on, the other end is connected on the resistance (OR5), the negative pole of controllable silicon (OBG8) meets power supply (OBG
3) negative pole, anodal serial connection is carried out relay OJ
' 1, meet power supply (OBG then
3) positive pole.OJ
' 1Normal opened contact OJ
' 1-1String has in pressure release coil (TQ) loop OJ primary cut-out (PB) (or feed master switch ODW)
' 1Normally closed contact OJ
' 1-2The nothing that is serially connected in primary cut-out (PB) (or feed master switch ODW) is pressed in the release coil loop.
C, has the zero-sequence current converter (BHL) that the load of secondary shunt capacitance and ground wire turn back.BHL is made of a ring structure iron core and secondary winding, is enclosed within the cable cover(ing) outside and the ground wire that comprise ground wire and turns back once, cable and the winding of the ground wire that turns back as BHL.One end ground connection of the secondary winding of zero-sequence current converter (BHL), the other end are connected on zero-sequence current inlet resistance nR
2With electric capacity nC
2Connecting line on, pass through nR
2Be defeated by zero-sequence current operational amplifier nBG
2Positive input.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 86201119 CN86201119U (en) | 1986-03-05 | 1986-03-05 | Selectable electric leakage protector for mine low voltage net |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 86201119 CN86201119U (en) | 1986-03-05 | 1986-03-05 | Selectable electric leakage protector for mine low voltage net |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN86201119U true CN86201119U (en) | 1988-12-28 |
Family
ID=4804945
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 86201119 Expired - Lifetime CN86201119U (en) | 1986-03-05 | 1986-03-05 | Selectable electric leakage protector for mine low voltage net |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN86201119U (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100353632C (en) * | 2004-01-16 | 2007-12-05 | 烽火通信科技股份有限公司 | Method for branch line unit protection |
| CN100357749C (en) * | 2005-10-08 | 2007-12-26 | 华北电力大学（北京） | Zero-line and breakage detector of three-phase and four-line system |
| CN100389527C (en) * | 2005-09-27 | 2008-05-21 | 傅桂兴 | Earthing compensation process for mine low-voltage electricity grid selective leakage protection system |
| CN100412556C (en) * | 2005-01-31 | 2008-08-20 | 傅桂兴 | Low-voltage electric network sequential discriminating leakage selecting method and protector for mine |
| CN100456594C (en) * | 2007-05-30 | 2009-01-28 | 唐山智诚电气有限公司 | Selective leakage determining method and leakage determining circuit |
| CN1635386B (en) * | 2003-12-30 | 2010-04-28 | 许继电气股份有限公司 | Relay protection fault detection module |
| CN101860005A (en) * | 2010-04-30 | 2010-10-13 | 江苏省电力公司南通供电公司 | Uninterrupted power test residual current protective device |
| CN104753024A (en) * | 2015-03-18 | 2015-07-01 | 胡妍 | Electricity leakage protecting method for preventing symmetric electricity leakage |
-
1986
- 1986-03-05 CN CN 86201119 patent/CN86201119U/en not_active Expired - Lifetime
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1635386B (en) * | 2003-12-30 | 2010-04-28 | 许继电气股份有限公司 | Relay protection fault detection module |
| CN100353632C (en) * | 2004-01-16 | 2007-12-05 | 烽火通信科技股份有限公司 | Method for branch line unit protection |
| CN100412556C (en) * | 2005-01-31 | 2008-08-20 | 傅桂兴 | Low-voltage electric network sequential discriminating leakage selecting method and protector for mine |
| CN100389527C (en) * | 2005-09-27 | 2008-05-21 | 傅桂兴 | Earthing compensation process for mine low-voltage electricity grid selective leakage protection system |
| CN100357749C (en) * | 2005-10-08 | 2007-12-26 | 华北电力大学（北京） | Zero-line and breakage detector of three-phase and four-line system |
| CN100456594C (en) * | 2007-05-30 | 2009-01-28 | 唐山智诚电气有限公司 | Selective leakage determining method and leakage determining circuit |
| CN101860005A (en) * | 2010-04-30 | 2010-10-13 | 江苏省电力公司南通供电公司 | Uninterrupted power test residual current protective device |
| CN101860005B (en) * | 2010-04-30 | 2012-09-05 | 江苏省电力公司南通供电公司 | Uninterrupted power test residual current protective device |
| CN104753024A (en) * | 2015-03-18 | 2015-07-01 | 胡妍 | Electricity leakage protecting method for preventing symmetric electricity leakage |
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