CN104237739A - Multipoint earth fault detection method, device and system for secondary current circuit - Google Patents
Multipoint earth fault detection method, device and system for secondary current circuit Download PDFInfo
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Abstract
The invention provides a multipoint earth fault detection method, device and system for a secondary current circuit. The method includes the steps that N-phase currents of an N-phase line of a three-phase current circuit and ground line currents of a ground line are collected in real time through a current mutual inductor, and the amplitude and the phase of the 1-kth harmonic of the N-phase currents and the amplitude and the phase of the 1-kth harmonic of the ground line currents are respectively calculated, wherein whether the amplitude of any harmonic, lager than a fault threshold, exists in the amplitude of the 1-kth harmonic of the N-phase currents is judged; if the harmonic exists, whether the amplitude of the harmonic is equal to the amplitude of the corresponding harmonic of the ground line currents and whether the difference between the phase of the harmonic and the phase of the corresponding harmonic of the ground line currents is 180 degrees are further judged; if the amplitude of the harmonic is equal to the amplitude of the corresponding harmonic of the ground line currents and the difference between the phase of the harmonic and the phase of the corresponding harmonic of the ground line currents is 180 degrees, it is judged that multipoint earth faults exist in the secondary current circuit.
Description
Technical field
The present invention relates to technical field of electric power, particularly relate to a kind of secondary current loop multipoint earth faults detection method, Apparatus and system.
Background technology
, between two different earth points, can potential difference (PD) be there is in the equipotential plane that grounding net of transformer substation is not actual.When the secondary circuit generation multipoint earthing of transformer substation current transformer, the potential difference (PD) between fault ground point and protective ground point will produce and scurry into electric current in the secondary circuit of mutual inductor.
When there is primary equipment earth fault, the potential difference (PD) generation marked change of two earth points, will affect the correct progress of disease of current transformer.Meanwhile, fault ground point and protective ground point can produce partial current to current transformer by earth mat, and one part of current flows back to current transformer from the earth.
Therefore, under the double action of partial current and earth point potential difference (PD), the amplitude of the electric current that current transformer detects and phase place all may change, and impact correctly judges, thus affects the operating result of fault detect.But when not breaking down, secondary current loop multipoint earthing is difficult to be found, belong to hidden fault, detect fault rapidly when not having good way that multipoint earth faults occurs in secondary current loop at present, the accuracy of electric current secondary loop ground connection cannot be ensured.
Summary of the invention
For solving the problems of the technologies described above, the invention provides a kind of secondary current loop multipoint earth faults detection method, Apparatus and system, the method, Apparatus and system flow process and structure is simple, easy to use and reaction velocity is fast, the secondary current loop occurring multipoint earth faults in multiple secondary current loop can be detected timely and effectively, thus the accuracy of secondary current loop testing result can be improved.
Secondary current loop provided by the invention multipoint earth faults detection method, comprising:
Adopt the N phase current of current transformer Real-time Collection three-phase current loop N phase line and the ground wire electric current of ground wire;
Calculate amplitude and the phase place of the 1-k subharmonic of described N phase current and ground wire electric current respectively; Wherein, k is natural number;
Judge that in the amplitude of the 1-k subharmonic of described N phase current, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold;
If there is the harmonic wave that its amplitude is greater than fault threshold in the 1-k subharmonic of described N phase current, then judge that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current;
If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then judge to there is multipoint earth faults in secondary current loop.
Wherein, described amplitude and the phase place calculating the 1-k subharmonic of described N phase current and ground wire electric current respectively, comprising:
Be voltage signal by described N phase current and ground wire current conversion respectively, and then voltage signal is converted into discrete digital signal;
Fourier transform is carried out to described digital signal, and then calculates the amplitude of 1-k subharmonic and the phase place of N phase current and ground wire electric current respectively.
Wherein, before the N phase current of described employing current transformer Real-time Collection three-phase current loop N phase line and the ground wire electric current of ground wire, also comprise:
Preset described fault threshold.
Wherein, after there is multipoint earth faults in described judgement secondary current loop, also comprise:
Multipoint earth faults information is sent to control terminal; Fault warning is sent after receiving multipoint earth faults information by described control terminal.
Wherein, the value of described k is 5; The value of described fault threshold is 8 ~ 12mA.
Corresponding, the present invention also provides a kind of secondary current loop multipoint earth faults pick-up unit, comprises
Current acquisition module, for being arranged on N phase line and the ground wire in three-phase current loop respectively, gathers N phase current and ground wire electric current;
Current processing module, for calculating amplitude and the phase place of the 1-k subharmonic of N phase current that described current acquisition module gathers and ground wire electric current respectively; Wherein, k is natural number;
First judge module, for judging that in the amplitude of 1-k subharmonic of the N phase current that described current processing module calculates, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold;
Second judge module, for judge the 1-k subharmonic of the N phase current that described current processing module calculates at described first judge module amplitude in exist amplitude be greater than the harmonic wave of fault threshold time, judge that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current; If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then judge to there is multipoint earth faults in secondary current loop.
Wherein, described current processing module comprises:
Change-over circuit, for being voltage signal by described N phase current and ground wire current conversion respectively, and then is converted into discrete digital signal by voltage signal;
Harmonics Calculation unit, for carrying out Fourier transform to described digital signal, and then calculates the amplitude of 1-k subharmonic and the phase place of N phase current and ground wire electric current respectively.
Wherein, described device also comprises: threshold value preset module, for preset described fault threshold.
Wherein, described device also comprises: information interaction module, for when described second judge module judges to there is multipoint earth faults in secondary current loop, outwards sends multipoint earth faults information.
Accordingly, the present invention also provides a kind of secondary current loop multipoint earth faults detection system, comprise: for receiving by the control terminal sending fault warning after the multipoint earth faults information of secondary current loop multipoint earth faults pick-up unit transmission, described control terminal is connected with at least one foregoing secondary current loop multipoint earth faults pick-up unit, and accepts its described multipoint earth faults information sent.
Method flow provided by the invention is simple, the reaction velocity of device is fast, system easy to use, the method, device and system can detect the multipoint earth faults in secondary current loop in time, thus inaccurate hidden danger is detected in the earth fault secondary current loop of bringing solved because hiding, and improves the accuracy of secondary current loop testing result.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is secondary current loop provided by the invention multipoint earth faults detection method first embodiment schematic flow sheet;
Fig. 2 is secondary current loop provided by the invention multipoint earth faults detection method second embodiment schematic flow sheet;
Fig. 3 is the schematic equivalent circuit of secondary current loop when there is not multipoint earth faults;
Schematic equivalent circuit when Fig. 4 is the arbitrary phase line generation multipoint earth faults in the triple-phase line in secondary current loop;
Schematic equivalent circuit when Fig. 5 is the N phase line generation multipoint earth faults in secondary current loop.
Fig. 6 is secondary current loop provided by the invention multipoint earth faults pick-up unit first example structure schematic diagram;
Fig. 7 is secondary current loop provided by the invention multipoint earth faults pick-up unit second example structure schematic diagram;
Fig. 8 is secondary current loop provided by the invention multipoint earth faults pick-up unit circuit module schematic diagram;
Fig. 9 is current processing modular structure schematic diagram in the multipoint earth faults pick-up unit of secondary current loop provided by the invention;
Figure 10 is secondary current loop provided by the invention multipoint earth faults detection system example structure schematic diagram.
Embodiment
Secondary current loop provided by the invention multipoint earth faults detection method flow process is simple, the reaction velocity of device is fast, system easy to use, the method, device and system can detect the multipoint earth faults in secondary current loop in time, thus inaccurate hidden danger is detected in the earth fault secondary current loop of bringing solved because hiding, and improves the accuracy of secondary current loop testing result.
See Fig. 1, it is secondary current loop provided by the invention multipoint earth faults detection method first embodiment schematic flow sheet.As shown in Figure 1, this secondary current loop multipoint earth faults detection method comprises:
Step S101, adopts the N phase current of current transformer Real-time Collection three-phase current loop N phase line and the ground wire electric current of ground wire.
Step S102, calculates amplitude and the phase place of the 1-k subharmonic of described N phase current and ground wire electric current respectively; Wherein, k is natural number, preferred k=5.
Step S103, judges that in the amplitude of the 1-k subharmonic of described N phase current, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold; If be judged as YES, then perform step S104, if be judged as NO, then return step S101.
Step S104, judges that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current; If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then perform step S105; Otherwise, judge to there is not multipoint earth faults in secondary current loop.
Step S105, judges to there is multipoint earth faults in secondary current loop.
Secondary current loop provided by the invention multipoint earth faults detection method flow process is simple, the multipoint earth faults in secondary current loop can be detected in time, thus inaccurate hidden danger is detected in the earth fault secondary current loop of bringing solved because hiding, and improves the accuracy of secondary current loop testing result.
See Fig. 2, it is secondary current loop provided by the invention multipoint earth faults detection method second embodiment schematic flow sheet.In the present embodiment, by the step of this secondary current loop multipoint earth faults detection method of description specifically and flow process.This secondary current loop multipoint earth faults detection method as shown in Figure 2, comprising:
Step S201, preset described fault threshold.Further, the value of described fault threshold is 8 ~ 12mA, is preferably 10mA.It will be appreciated by persons skilled in the art that this step is initialization step, need when first time implements secondary current loop multipoint earth faults detection method provided by the invention to perform, in follow-up implementation process, can not this step be performed.
Step S202, adopts the N phase current of current transformer Real-time Collection three-phase current loop N phase line and the ground wire electric current of ground wire.Further, described current transformer preferably adopts open type current transformer.
Step S203, is voltage signal by described N phase current and ground wire current conversion respectively, and then voltage signal is converted into discrete digital signal.
Step S204, carries out Fourier transform to described digital signal, and then calculates the amplitude of 1-k subharmonic and the phase place of N phase current and ground wire electric current respectively; Wherein, k is natural number, preferred k=5.
Step S205, judges that in the amplitude of the 1-k subharmonic of described N phase current, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold; If be judged as YES, then perform step S206, if be judged as NO, then return step S202.
Step S206, judges that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current; If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then perform step S207; Otherwise, judge to there is not multipoint earth faults in secondary current loop.
Step S207, judges to there is multipoint earth faults in secondary current loop.
Preferably, the secondary current loop multipoint earth faults detection method step that the present embodiment provides can also comprise: step S208, is sent to control terminal by multipoint earth faults information; Fault warning is sent after receiving multipoint earth faults information by described control terminal.
Below in conjunction with accompanying drawing 3 ~ 5 in detail principle of the present invention is described in detail, with reference to shown in Fig. 3, Fig. 3 is the schematic equivalent circuit of secondary current loop when there is not multipoint earth faults, when the secondary current loop in Fig. 3 does not exist multipoint earthing, has I1, I2, I3 through node electric current 2..Load being considered as a node, is 0 can to obtain according to node current vector:
I1=Ia+Ib+Ic；
In like manner I3=Ia+Ib+Ic can be obtained;
For node 2., meet the following conditions:
I1+I2=I3；
Therefore, I2=0 can be released according to above formula.
When ignoring distributed capacitance and affecting, due to three-phase current equal and opposite in direction, and phase differential is 120 degree, therefore can obtain I1=Ia+Ib+Ic ≈ 0.
If therefore measure I1 and I2 with mutual inductor 1 and mutual inductor 2 respectively in the position of such as Fig. 3, have: when there is not secondary current loop multipoint earthing, mutual inductor 1 to survey electric current I 1 be 0, mutual inductor 2 to survey electric current I 2 be 0.
Schematic equivalent circuit in A, B, C phase line in secondary current loop during arbitrary phase line generation multipoint earth faults as shown in Figure 4; suppose that earth fault occurs at 1. place in the diagram; Ib will be split into Ib1 and Ib2; Ib1 flows through load and gets back to 2. point from phase line; and Ib1 flows through earth mat through protective ground line after fault ground point gets back to 2. point, be 0 can to obtain according to node current vector:
I1+I2=I3；
I1=Ia+Ib1+Ic?=-?Ib?+?Ib1=-?Ib2；
I3=0；
I2=Ib2 can be obtained according to above formula;
Impact as earth mat electric potential difference: due to the earth potential 1. and 2. put, need could form loop through mutual inductor this locality or load, loop resistance is comparatively large, so this part electric current is ignored when phase line grounding is analyzed.
Mutual inductor 1 and mutual inductor 2 measure I1 and I2 respectively in the such as position of Fig. 4 then to be had: during at secondary current loop phase line generation multipoint earthing, mutual inductor 1 to survey electric current be-Ib2, mutual inductor 2 to survey electric current be Ib2, namely, when phase line generation multipoint earthing, mutual inductor 1 and mutual inductor 2 will record one group of contrary electric current of equal and opposite in direction, direction.
Schematic equivalent circuit during N phase line generation multipoint earth faults as shown in Figure 5; suppose that earth fault occurs at 3. place in Figure 5; due to protective ground point 2. with fault ground point 3. between be that wire is directly connected; to form electric current I s under earth mat electric potential difference Vs effect, be 0 can to obtain according to node current vector:
I1+I2=I3；
I1=-Is+Ia+Ib1+Ic?=-Is；
I3=0；
According to above formula, I2=Is;
Mutual inductor 1 and mutual inductor 2 measure I respectively in the position of such as Fig. 5
1and I
2then have: when secondary current loop N phase line generation multipoint earthing, mutual inductor 1 to survey electric current be-I
s, mutual inductor 2 to survey electric current be I
s, namely when N phase line generation multipoint earthing, mutual inductor 1 and mutual inductor 2 will record one group of contrary electric current of equal and opposite in direction, direction.
Therefore, when there is not multipoint earth faults in secondary current loop, I
1and I
2be 0, when there is multipoint earth faults in secondary current loop, I
1and I
2amplitude is not all 0, and equal and opposite in direction, direction is contrary.Therefore, only detect that in secondary current loop, certain harmonic wave of N phase current is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, when direction is phase 180 degree on the contrary, could judge to there is multipoint earth faults in secondary current loop.
Secondary current loop provided by the invention multipoint earth faults detection method flow process is simple, the multipoint earth faults in secondary current loop can be detected in time, thus inaccurate hidden danger is detected in the earth fault secondary current loop of bringing solved because hiding, and improves the accuracy of secondary current loop testing result.
See Fig. 6, it is secondary current loop provided by the invention multipoint earth faults pick-up unit first example structure schematic diagram; As shown in Figure 6, this secondary current loop multipoint earth faults pick-up unit comprises:
Current acquisition module 1, for being arranged on N phase line and the ground wire in three-phase current loop respectively, gathers N phase current and ground wire electric current;
Current processing module 2, for calculating amplitude and the phase place of the 1-k subharmonic of N phase current that described current acquisition module gathers and ground wire electric current respectively; Wherein, k is natural number;
First judge module 3, for judging that in the amplitude of 1-k subharmonic of the N phase current that described current processing module calculates, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold;
Second judge module 4, for judge the 1-k subharmonic of the N phase current that described current processing module calculates at described first judge module amplitude in exist amplitude be greater than the harmonic wave of fault threshold time, judge that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current; If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then judge to there is multipoint earth faults in secondary current loop.
Secondary current loop provided by the invention multipoint earth faults pick-up unit reaction velocity is fast, easy to use, this device can detect the multipoint earth faults in secondary current loop in time, thus inaccurate hidden danger is detected in the earth fault secondary current loop of bringing solved because hiding, and improves the accuracy of secondary current loop testing result.
Fig. 7 and Fig. 8, Fig. 7 are secondary current loop provided by the invention multipoint earth faults pick-up unit second example structure schematic diagram; Fig. 8 is secondary current loop provided by the invention multipoint earth faults pick-up unit circuit module schematic diagram.In the present embodiment, by the structure of this secondary current loop multipoint earth faults pick-up unit of description specifically and realizing circuit.As shown in the figure, this device comprises:
Current acquisition module 1, for being arranged on N phase line and the ground wire in three-phase current loop respectively, gathers N phase current and ground wire electric current; Preferably, described current acquisition module 1 can be two open type current transformers.
Current processing module 2, for calculating amplitude and the phase place of the 1-k subharmonic of N phase current that described current acquisition module gathers and ground wire electric current respectively; Wherein, k is natural number.More specifically, as shown in Figure 9, described current processing module 2 comprises:
Change-over circuit 21, for being voltage signal by described N phase current and ground wire current conversion respectively, and then is converted into discrete digital signal by voltage signal.More specifically, as shown in Figure 5, this change-over circuit 21 can be made up of electricity Liu voltage conversion circuit and A/D converter, and electricity Liu voltage conversion circuit is all connected with two open type current transformers, for being voltage signal by current conversion; A/D converter and electric current voltage conversion circuit be connected, for voltage signal is converted into discrete digital signal.
Harmonics Calculation unit 22, for carrying out Fourier transform to described digital signal, and then calculates the amplitude of 1-k subharmonic and the phase place of N phase current and ground wire electric current respectively.In circuit theory diagrams as shown in Figure 5, Harmonics Calculation unit 22 is integrated in central processing unit.
First judge module 3, for judging that in the amplitude of 1-k subharmonic of the N phase current that described current processing module calculates, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold.Preferably, the secondary current loop multipoint earth faults pick-up unit that the present embodiment provides also comprises: threshold value preset module 5, for preset described fault threshold.
Second judge module 4, during for judging that at described first judge module 3 there is amplitude in the amplitude of the 1-k subharmonic of the N phase current that described current processing module calculates is greater than the harmonic wave of fault threshold, judge that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current; If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then judge to there is multipoint earth faults in secondary current loop.
It will be appreciated by persons skilled in the art that above-mentioned Harmonics Calculation unit 22, first judge module 3, second judge module 4 can be integrated in the central processing unit of circuit as shown in Figure 5.Preferably, the secondary current loop multipoint earth faults pick-up unit that the embodiment of the present invention provides also comprises information interaction module 6, information interaction module 6, for when described second judge module 4 judges to there is multipoint earth faults in secondary current loop, outwards sends multipoint earth faults information.
Secondary current loop provided by the invention multipoint earth faults pick-up unit reaction velocity is fast, easy to use, this device can detect the multipoint earth faults in secondary current loop in time, thus inaccurate hidden danger is detected in the earth fault secondary current loop of bringing solved because hiding, and improves the accuracy of secondary current loop testing result.
See Figure 10, it is secondary current loop provided by the invention multipoint earth faults detection system example structure schematic diagram.Control terminal 8 and at least one secondary current loop multipoint earth faults pick-up unit 9 being connected with this control terminal as shown in the figure.Control terminal 8 is for receiving by the control terminal sending fault warning after the multipoint earth faults information of secondary current loop multipoint earth faults pick-up unit transmission.It will be appreciated by persons skilled in the art that this control terminal 8 can with alarm module 81, display module 82 and memory module 83 with the use of.It should be noted that, the secondary current loop multipoint earth faults pick-up unit in the present embodiment is identical with the secondary current loop multipoint earth faults pick-up unit in two secondary current loop multipoint earth faults pick-up unit embodiments provided by the invention.
Secondary current loop provided by the invention multipoint earth faults detection system is easy to use, the multipoint earth faults in secondary current loop can be detected in time, thus inaccurate hidden danger is detected in the earth fault secondary current loop of bringing solved because hiding, and improves the accuracy of secondary current loop testing result.
The specific works principle of secondary current loop provided by the invention multipoint earth faults pick-up unit and system is consistent with the principle of work described in embodiment of the method before, repeats no more herein.
Above content is in conjunction with concrete preferred implementation further description made for the present invention, can not assert that specific embodiment of the invention is confined to these explanations.For general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, some simple deduction or replace can also be made, all should be considered as belonging to protection scope of the present invention.
Claims (10)
1. a secondary current loop multipoint earth faults detection method, is characterized in that, comprising:
Adopt the N phase current of current transformer Real-time Collection three-phase current loop N phase line and the ground wire electric current of ground wire;
Calculate amplitude and the phase place of the 1-k subharmonic of described N phase current and ground wire electric current respectively; Wherein, k is natural number;
Judge that in the amplitude of the 1-k subharmonic of described N phase current, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold;
If there is the harmonic wave that its amplitude is greater than fault threshold in the 1-k subharmonic of described N phase current, then judge that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current;
If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then judge to there is multipoint earth faults in secondary current loop.
2. secondary current loop as claimed in claim 1 multipoint earth faults detection method, it is characterized in that, described amplitude and the phase place calculating the 1-k subharmonic of described N phase current and ground wire electric current respectively, comprising:
Be voltage signal by described N phase current and ground wire current conversion respectively, and then voltage signal is converted into discrete digital signal;
Fourier transform is carried out to described digital signal, and then calculates the amplitude of 1-k subharmonic and the phase place of N phase current and ground wire electric current respectively.
3. secondary current loop as claimed in claim 1 multipoint earth faults detection method, is characterized in that, before the N phase current of described employing current transformer Real-time Collection three-phase current loop N phase line and the ground wire electric current of ground wire, also comprises:
Preset described fault threshold.
4. secondary current loop as claimed in claim 1 multipoint earth faults detection method, is characterized in that, after there is multipoint earth faults, also comprise in described judgement secondary current loop:
Multipoint earth faults information is sent to control terminal; Fault warning is sent after receiving multipoint earth faults information by described control terminal.
5. the secondary current loop multipoint earth faults detection method according to any one of Claims 1-4, is characterized in that, the value of described k is 5; The value of described fault threshold is 8 ~ 12mA.
6. a secondary current loop multipoint earth faults pick-up unit, is characterized in that, comprise
Current acquisition module, for being arranged on N phase line and the ground wire in three-phase current loop respectively, gathers N phase current and ground wire electric current;
Current processing module, for calculating amplitude and the phase place of the 1-k subharmonic of N phase current that described current acquisition module gathers and ground wire electric current respectively; Wherein, k is natural number;
First judge module, for judging that in the amplitude of 1-k subharmonic of the N phase current that described current processing module calculates, the amplitude that whether there is arbitrary harmonic wave is greater than fault threshold;
Second judge module, for judge the 1-k subharmonic of the N phase current that described current processing module calculates at described first judge module amplitude in exist amplitude be greater than the harmonic wave of fault threshold time, judge that whether the amplitude of this harmonic wave equal with the amplitude of the corresponding harmonic wave of ground wire electric current further, and the phase place of this harmonic wave whether with the phase 180 degree of the corresponding harmonic wave of ground wire electric current; If the amplitude of this harmonic wave is equal with the amplitude of the corresponding harmonic wave of ground wire electric current, and the phase place of this harmonic wave and the phase 180 degree of the corresponding harmonic wave of ground wire electric current, then judge to there is multipoint earth faults in secondary current loop.
7. secondary current loop as claimed in claim 6 multipoint earth faults pick-up unit, it is characterized in that, described current processing module comprises:
Change-over circuit, for being voltage signal by described N phase current and ground wire current conversion respectively, and then is converted into discrete digital signal by voltage signal;
Harmonics Calculation unit, for carrying out Fourier transform to described digital signal, and then calculates the amplitude of 1-k subharmonic and the phase place of N phase current and ground wire electric current respectively.
8. secondary current loop as claimed in claim 6 multipoint earth faults pick-up unit, it is characterized in that, described device also comprises: threshold value preset module, for preset described fault threshold.
9. secondary current loop as claimed in claim 6 multipoint earth faults pick-up unit, it is characterized in that, described device also comprises: this system comprises
A kind of secondary current loop multipoint earth faults detection system, it is characterized in that, comprise: for receiving by the control terminal sending fault warning after the multipoint earth faults information of secondary current loop multipoint earth faults pick-up unit transmission, described control terminal is connected with at least one secondary current loop multipoint earth faults pick-up unit according to any one of claim 6 to 9, and accepts its described multipoint earth faults information sent.
10. a secondary current loop multipoint earth faults detection system, it is characterized in that, comprise: for receiving by the control terminal sending fault warning after the multipoint earth faults information of secondary current loop multipoint earth faults pick-up unit transmission, described control terminal is connected with at least one secondary current loop multipoint earth faults pick-up unit according to any one of claim 6 to 9, and accepts its described multipoint earth faults information sent.
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| CN104914352A (en) * | 2015-05-07 | 2015-09-16 | 国家电网公司 | NUGS single-phase grounding fault location method based on harmonic difference distinguishing |
| CN108051699A (en) * | 2017-11-17 | 2018-05-18 | 国网湖南省电力有限公司 | A kind of secondary loop of mutual inductor of transformer substation exception live detection method and system |
| CN111060846A (en) * | 2019-12-19 | 2020-04-24 | 深圳供电局有限公司 | CT secondary circuit fault on-line monitoring method |
| CN111665455A (en) * | 2020-05-21 | 2020-09-15 | 国网江苏省电力有限公司南京供电分公司 | Short-circuit fault positioning method for direct-current power distribution system |
| CN115407241A (en) * | 2022-10-31 | 2022-11-29 | 国网辽宁省电力有限公司 | Secondary circuit grounding current monitoring system, method and computer readable storage medium |
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| CN111060846A (en) * | 2019-12-19 | 2020-04-24 | 深圳供电局有限公司 | CT secondary circuit fault on-line monitoring method |
| CN111060846B (en) * | 2019-12-19 | 2022-03-22 | 深圳供电局有限公司 | CT secondary circuit fault on-line monitoring method |
| CN111665455A (en) * | 2020-05-21 | 2020-09-15 | 国网江苏省电力有限公司南京供电分公司 | Short-circuit fault positioning method for direct-current power distribution system |
| CN111665455B (en) * | 2020-05-21 | 2022-07-12 | 国网江苏省电力有限公司南京供电分公司 | Short-circuit fault positioning method for direct-current power distribution system |
| CN115407241A (en) * | 2022-10-31 | 2022-11-29 | 国网辽宁省电力有限公司 | Secondary circuit grounding current monitoring system, method and computer readable storage medium |
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