CN109061376A - A kind of judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity - Google Patents
A kind of judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity Download PDFInfo
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- CN109061376A CN109061376A CN201811094106.7A CN201811094106A CN109061376A CN 109061376 A CN109061376 A CN 109061376A CN 201811094106 A CN201811094106 A CN 201811094106A CN 109061376 A CN109061376 A CN 109061376A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/72—Testing of electric windings
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Abstract
The invention discloses a kind of judgment methods of Small Electric Current Earthing And Routing Device CT incorrect polarity, comprising the following steps: when ground fault occurs, determines fault branch zero-sequence current according to the selected faulty line of device；The instantaneous value of all branch currents is recorded using device sampling recording function；Calculating ratio pair is carried out to the instantaneous value of all branch currents, if feature against regulation, judgement has branch CT incorrect polarity, and route selection result is unreliable at this time, and such situation is shown on device.The present invention is based on isolated neutral system Small Electric Current Earthing And Routing Devices using the premise of each branch zero-sequence current on zero sequence CT acquisition bus, in conjunction with the route selection result of line selection apparatus, the characteristics of each branch current, carries out analytical calculation when by the way that singlephase earth fault occurs to branch, obtains the conclusion for having zero sequence CT reversed with the presence or absence of branch.
Description
Technical field
The present invention relates to isolated neutral system technical field, specifically a kind of Small Electric Current Earthing And Routing Device CT polarity
The judgment method of mistake.
Background technique
In medium voltage distribution network, singlephase earth fault accounts for 80% of total failare or more, accurate after singlephase earth fault occurs
Selection faulty line is just particularly important, therefore Small Electric Current Earthing And Routing Device has obtained widely answering in power distribution network
With.
Currently, the Small Electric Current Earthing And Routing Device of nearly all producer requires to carry out the zero-sequence current of route in market
To carry out dependent diagnostic, the polarity of zero sequence CT correctly just becomes vital one of influence route selection accuracy for sampling analysis
Factor.
The characteristics of in view of zero-sequence current, the very little when no ground failure occurs, therefore often can not be quasi- when being installed
Really judge CT polarity, which results in device is practical put into operation after have often route selection inaccuracy situation generation.
Therefore, for the above status, there is an urgent need to develop a kind of judgements of Small Electric Current Earthing And Routing Device CT incorrect polarity
Method, to overcome the shortcomings of in currently practical application.
Summary of the invention
The purpose of the present invention is to provide a kind of judgment methods of Small Electric Current Earthing And Routing Device CT incorrect polarity, to solve
The problems mentioned above in the background art.
To achieve the above object, the invention provides the following technical scheme:
A kind of judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity, comprising the following steps:
1) when ground fault occurs, fault branch zero-sequence current is determined according to the selected faulty line of device；
2) instantaneous value of all branch currents is recorded using device sampling recording function；
3) calculating ratio pair is carried out to the instantaneous value of all branch currents, if feature against regulation, judgement has the pole branch CT
Property mistake, route selection result is unreliable at this time, and such situation is shown on device.
As a further solution of the present invention: in step 1), fault branch zero-sequence current is equal to remaining all non-faulting
Route flow through zero-sequence current phasor and.
As a further solution of the present invention:, it is specified that feature is as follows in step 3):
System operate normally when, three-phase ground capacitance current phasor and be 0, every phase-to-ground voltage be equal to phase voltage；
When individual event ground fault occurs, the zero-sequence current of non-fault line is equal to the vector of the route three-phase ground capacitance electric current
With direction flows to route by bus；The zero-sequence current of faulty line is equal to the arrow of total system non-fault line capacitive earth current
Amount and, direction flows to bus by route.
Compared with prior art, the beneficial effects of the present invention are: in conjunction with line selection apparatus route selection as a result, to CT polarity carry out
Judgement, and by judging result in interface display, the case where current CT of maintenance personnel is with the presence or absence of setup error is reminded with this result.
Detailed description of the invention
Fig. 1 is three-phase phase voltage circuit diagram of the invention.
Fig. 2 is three-phase phase voltage schematic vector diagram of the invention.
Fig. 3 is three-phase ground capacitance current circuit schematic diagram of the invention.
Fig. 4 is three-phase ground capacitance current phasor schematic diagram of the invention.
Fig. 5 is that C phase ground fault circuit diagram occurs in the present invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
Fig. 1~5 are please referred to, a kind of judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity is based primarily upon following
Principle is realized:
It will form capacitor when between any two conductor across dielectric, therefore in simple power grid, isolated neutral
When system operates normally, each phase line has identical direct-to-ground capacitance C0 over the ground, under phase voltage effect, every phase have one it is advanced
In 90 degree of phase voltage capacitance currents flow into ground in, however the size due to capacitor it is directly proportional to capacitor plate area and and pole plate
Distance is inversely proportional, so the direct-to-ground capacitance of route, especially overhead transmission line direct-to-ground capacitance very little, capacitive reactance is very big, direct-to-ground capacitance electricity
Flow very little.
When system operates normally, as shown in Figs 1-4, since three-phase phase voltage UA, UB, UC are symmetrically, three is relatively electric
Capacitance current Ico.A, Ico.B, Ico.C are also balance.Therefore, three-phase ground capacitance current phasor and be 0, without current direction
Greatly, every phase-to-ground voltage is equal to phase voltage.
In the presence of having voltage source G and a plurality of route in network system, as shown in figure 5, every voltage source and every route
It is indicated here with C0G, C01, C02 with the presence of capacitor over the ground, after the C phase in route 2 is grounded, total system C phase-to-ground voltage
It is 0, therefore relatively capacitance current is also 0 to C, while the voltage-to-ground of A, B phase and is increased to original √ 3 to earth-current
Times.It in this case,, therefore, should since C phase current is to have self capacity electric current in 0, A phase and B phase on non-fault line 1
Zero-sequence current 3I01=IA1+IB1 on route, direction flows to route by bus.
On faulty line 2, capacitive earth current IA2, IB2 for having itself of A phase and B phase, the difference is that ground connection
Point will flow back to A phase and B relatively the sum of capacitance current from C phase, therefore it is total from the electric current that C phase flows out to be represented by IC1=- I, this
Zero-sequence current on line-transect road 2 is 3I02=IA2+IB2+IC2=IAG+IBG+IA1+IB1, and direction is to flow to bus by route.
By analyzing above it can be concluded that, in small current neutral grounding system, when individual event ground fault occurs, non-fault line
Zero-sequence current be equal to the vector sum of the route three-phase ground capacitance electric current, direction flows to route by bus, the zero of faulty line
Sequence electric current is equal to the vector sum of total system non-fault line capacitive earth current, and direction flows to bus by route.
Application Example
As shown in figure 5, fault branch zero-sequence current is determined according to the selected faulty line of device when ground fault occurs,
This electric current should be equal to remaining all non-fault line flow through zero-sequence current phasor and.Device is utilized after ground fault occurs
Sampling recording function records the instantaneous value of all branch currents, carries out calculating ratio pair to current value using principle noted earlier, such as
Fruit does not meet feature noted earlier, then judgement has branch CT incorrect polarity, and route selection result is unreliable at this time, and such situation is existed
It is shown on device.
The judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity, is connect based on isolated neutral system low current
Ground line selection apparatus obtains the premise of each branch zero-sequence current on bus using zero sequence CT, in conjunction with line selection apparatus route selection as a result, logical
The characteristics of crossing each branch current when singlephase earth fault occurs to branch carries out analytical calculation, and obtaining has zero sequence with the presence or absence of branch
CT reversed conclusion.
In conjunction with line selection apparatus route selection as a result, judging CT polarity, and judging result is tied in interface display with this
The case where fruit reminds the current CT of maintenance personnel to whether there is setup error.
It is obvious to a person skilled in the art that invention is not limited to the details of the above exemplary embodiments, Er Qie
In the case where without departing substantially from spirit or essential attributes of the invention, the present invention can be realized in other specific forms.Therefore, no matter
From the point of view of which point, the present embodiments are to be considered as illustrative and not restrictive, and the scope of the present invention is by appended power
Benefit requires rather than above description limits, it is intended that all by what is fallen within the meaning and scope of the equivalent elements of the claims
Variation is included within the present invention.Any reference signs in the claims should not be construed as limiting the involved claims.
The above are merely the preferred embodiment of the present invention, it is noted that for those skilled in the art, not
Under the premise of being detached from present inventive concept, several modifications and improvements can also be made, these also should be considered as protection model of the invention
It encloses, these all will not influence the effect and patent practicability that the present invention is implemented.
Claims (4)
1. a kind of judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity, which comprises the following steps:
1) when ground fault occurs, fault branch zero-sequence current is determined according to the selected faulty line of device；
2) instantaneous value of all branch currents is recorded using device sampling recording function；
3) calculating ratio pair is carried out to the instantaneous value of all branch currents, if feature against regulation, judgement has the pole branch CT
Property mistake, route selection result is unreliable at this time, and such situation is shown on device.
2. the judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity according to claim 1, which is characterized in that
In step 1), fault branch zero-sequence current be equal to remaining all non-fault line flow through zero-sequence current phasor and.
3. the judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity according to claim 1, which is characterized in that
, it is specified that feature is as follows in step 3): system operate normally when, three-phase ground capacitance current phasor and be 0, every phase-to-ground voltage etc.
In phase voltage.
4. the judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity according to claim 1 or 3, feature exist
In, it is specified that feature is as follows in step 3): when individual event ground fault occurs, the zero-sequence current of non-fault line is equal to the route
The vector sum of three-phase ground capacitance electric current, direction flow to route by bus；The zero-sequence current of faulty line is equal to the non-event of total system
Hinder the vector sum of line mutual-ground capacitor electric current, direction flows to bus by route.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201811094106.7A CN109061376A (en) | 2018-09-19 | 2018-09-19 | A kind of judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201811094106.7A CN109061376A (en) | 2018-09-19 | 2018-09-19 | A kind of judgment method of Small Electric Current Earthing And Routing Device CT incorrect polarity |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110927631A (en) * | 2019-12-03 | 2020-03-27 | 陕西省地方电力（集团）有限公司宝鸡供电分公司 | Polarity judgment method for zero-sequence current transformer |
| CN111077477A (en) * | 2019-10-27 | 2020-04-28 | 徐州和纬信电科技有限公司 | Line selection device and zero sequence current polarity detection and automatic correction method thereof |
| CN111308398A (en) * | 2020-03-31 | 2020-06-19 | 深圳供电局有限公司 | Method and device for judging polarity of zero sequence current transformer in transformer substation |
| CN114200354A (en) * | 2022-02-16 | 2022-03-18 | 广东电网有限责任公司肇庆供电局 | Zero sequence CT polarity online detection method, system and equipment |
| CN114895144A (en) * | 2022-05-05 | 2022-08-12 | 云南电网有限责任公司电力科学研究院 | Line selection evaluation method and device, electronic equipment and storage medium |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111077477A (en) * | 2019-10-27 | 2020-04-28 | 徐州和纬信电科技有限公司 | Line selection device and zero sequence current polarity detection and automatic correction method thereof |
| CN110927631A (en) * | 2019-12-03 | 2020-03-27 | 陕西省地方电力（集团）有限公司宝鸡供电分公司 | Polarity judgment method for zero-sequence current transformer |
| CN110927631B (en) * | 2019-12-03 | 2022-01-11 | 陕西省地方电力（集团）有限公司宝鸡供电分公司 | Polarity judgment method for zero-sequence current transformer |
| CN111308398A (en) * | 2020-03-31 | 2020-06-19 | 深圳供电局有限公司 | Method and device for judging polarity of zero sequence current transformer in transformer substation |
| CN114200354A (en) * | 2022-02-16 | 2022-03-18 | 广东电网有限责任公司肇庆供电局 | Zero sequence CT polarity online detection method, system and equipment |
| CN114200354B (en) * | 2022-02-16 | 2022-04-19 | 广东电网有限责任公司肇庆供电局 | Zero sequence CT polarity online detection method, system and equipment |
| CN114895144A (en) * | 2022-05-05 | 2022-08-12 | 云南电网有限责任公司电力科学研究院 | Line selection evaluation method and device, electronic equipment and storage medium |
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