CN204011024U - A kind of novel electronic type zero sequence current transformer - Google Patents
A kind of novel electronic type zero sequence current transformer Download PDFInfo
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- CN204011024U CN204011024U CN201420378430.2U CN201420378430U CN204011024U CN 204011024 U CN204011024 U CN 204011024U CN 201420378430 U CN201420378430 U CN 201420378430U CN 204011024 U CN204011024 U CN 204011024U
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- sequence current
- transformer
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- instrument transformer
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Abstract
The utility model proposes a kind of novel electronic type zero sequence current transformer, comprise phase-sequence current instrument transformer, described phase-sequence current instrument transformer comprises primary current instrument transformer and secondary current instrument transformer, the secondary winding of described primary current instrument transformer is connected with a winding of described secondary current instrument transformer, described electronic type zero sequence current transformer comprises three described phase-sequence current instrument transformers, the equal parallel resistance R of secondary winding of each phase-sequence current instrument transformer, described in each, resistance R is connected successively.That electronic type zero sequence current transformer of the present utility model has is safe, signal output accuracy is high, long distance of signal transmission, the advantage that easy for installation and cost performance is high.
Description
Technical field
The utility model relates to current transformer technical field, is specifically related to a kind of novel electronic type zero sequence current transformer.
Background technology
Current transformer (hereinafter to be referred as CT), according to electromagnetic induction principle, is comprised of closed iron core and winding.Seldom, general wire single turn is unshakable in one's determination through CT for a umber of turn of CT; The secondary winding turn ratio of CT is more, and secondary winding output is generally serially connected in measuring instrument or protection loop.Because first and second umber of turn is inconsistent, there is CT no-load voltage ratio, so CT can be the little electric current of secondary side or low-pressure side by primary side or on high-tension side large current conversion, be convenient to instrument and protector measuring.
Three-phase conducting wire (threephase cable) is together through a zero sequence CT, or a zero sequence CT is installed on neutral line N, or on three-phase line, respectively fill a CT, utilize these CT to detect current phasor and the IA+IB+IC (electric current of three-phase line is respectively IA, IB and IC) of three-phase, zero-sequence current Io, i.e. IA+IB+IC=Io.On circuit, connect three-phase load complete equipilibrium time, and while not considering the leakage current of earth fault and circuit, electric equipment, Io=0A; When the three-phase load connecing on circuit (load and the neutral line or formed greatly loop) and circuit stray capacitance laod unbalance, Io=IN, zero-sequence current is now unsymmetrical current IN; When a certain, while there is earth fault mutually, certainly lead to a single-phase earth fault current Id, the zero-sequence current Io=IN+Id now detecting, is the vector of three-phase imbalance electric current and single-phase earth fault current.
CT becomes the little electric current of secondary to use by large current conversion once, when line load is large or be short-circuited fault, the electric current of CT secondary circuit is very large, opening voltage is higher than 36V human safety voltage, opening overtension holds fire hazardous simultaneously, so CT secondary circuit definitely can not be opened a way, otherwise can cause equipment and personal safety accident.
In fact winding of CT is exactly high voltage wire, secondary winding is low-voltage wire, if but insulation breakdown, dangerous voltage can be transmitted to low-pressure side from high-pressure side, equipment and personal safety are caused to damage, therefore CT iron core must be drawn earth connection and connect the earth, and CT secondary line also should have single line to connect the earth, otherwise also has personal safety hidden danger.
For the overhead transmission line of 10kV isolated neutral or compensated distribution network, both do not had threephase cable not have the neutral line can be used for installing zero sequence CT yet, can only obtain by the CT method of zero sequence is installed on the closed busbar of the inner three-phase of on-pole switch the zero-sequence current of overhead transmission line.Realize in this way zero sequence CT, the one, equipment investment is larger, and the 2nd, installation and maintenance expense is high, and the 3rd, disconnect existing wire switch could be installed, be not suitable for applying.
Utility model content
The implementation that the utility model will solve existing zero sequence current mutual inductor can cause equipment investment large, and installation and maintenance expense is high, disconnect the problem that existing wire could be installed switch.
The technical solution of the utility model is achieved in that
A kind of novel electronic type zero sequence current transformer, comprise phase-sequence current instrument transformer, described phase-sequence current instrument transformer comprises primary current instrument transformer and secondary current instrument transformer, the secondary winding of described primary current instrument transformer is connected with a winding of described secondary current instrument transformer, described electronic type zero sequence current transformer comprises three described phase-sequence current instrument transformers, the equal parallel resistance R of secondary winding of each phase-sequence current instrument transformer, described in each, resistance R is connected successively.
In preferred scheme, above-mentioned electronic type zero sequence current transformer also comprises the equipotential line being electrically connected to the iron core of primary current instrument transformer described in each, and described equipotential line is wrapped on the wire through the iron core of described primary current instrument transformer.
In preferred scheme, the no-load voltage ratio of described primary current instrument transformer is 400:1.
In preferred scheme, the no-load voltage ratio of described secondary current instrument transformer is 400:1.
In preferred scheme, the metalfilmresistor of my 100 Ω, 1/4W of described resistance R, 1% precision.
In preferred scheme, a winding of described secondary current instrument transformer is 5 circles, and secondary winding is 2000 circles.
The beneficial effects of the utility model are as follows:
1, fail safe is higher
Secondary CT and a CT are poured into a mould and are packaged together by composite insulating material, and back panel wiring does not expose, and do not exist a CT second open circuit to cause overvoltage problem.Adopt the high insulating property of secondary CT, realize 10kV overhead transmission line to the secondary electrical isolation in electronic type zero sequence CT output signal loop, guarantee that human body and equipment are safer.
2, signal output accuracy is higher
Adopt the high magnetic property of secondary CT, realize the undistorted transmission of electronic type zero sequence CT output signal.
3, signal transmission distance is farther
Adopt electric current-current transformation function of secondary CT, adopt current signal to transmit, more can adapt to electromagnetic interference environment, realize the remote transmission of electronic type zero sequence CT output signal.
4, install more convenient
The electronic type zero sequence CT of the technical program by three independently phase sequence CT form, and phase sequence CT can install separately, and can make open C T, need not disconnect 10kV aerial condutor and install.Zero sequence current signal is synthetic in the circuit board by measurement mechanism.
5, cost performance is higher
The product that utilizes the technical program development, volume is little, lightweight, and cost is low, installs, maintenance cost is low.
Accompanying drawing explanation
In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only embodiment more of the present utility model, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.
Fig. 1 is the schematic diagram of existing current transformer;
Fig. 2 is the schematic diagram of a kind of novel electronic type zero sequence current transformer of the utility model embodiment.
Embodiment
Below in conjunction with the accompanying drawing in the utility model embodiment, the technical scheme in the utility model embodiment is clearly and completely described, obviously, described embodiment is only the utility model part embodiment, rather than whole embodiment.Embodiment based in the utility model, those of ordinary skills are not making the every other embodiment obtaining under creative work prerequisite, all belong to the scope of the utility model protection.
The schematic diagram of existing current transformer shown in Figure 1; existing CT is comprised of iron core 1 and the winding 2 and the secondary winding 3 that are wrapped on iron core; this CT can be the little electric current of secondary winding 3 of flowing through in secondary side or low-pressure side by the large current conversion of the winding 2 of flowing through on primary side or high-pressure side, is convenient to the instrument and the protector measuring electric current that are connected with the output of secondary winding 3.
The utility model adopts an outdoor CT and secondary CT synthetic technology to realize electronic type zero sequence CT, by secondary electrical isolation, improve fail safe, reduce CT output current and opening voltage simultaneously, at CT, surprisingly open a way and imperfect earth also can be guaranteed the person and device security when good.
Secondary CT adopts the extraordinary amorphous alloy material of insulation property, on the magnetic guiding loop of amorphous alloy material respectively around the coil of two different turn ratios.More than withstand voltage between two coils of secondary CT after epoxy resin encapsulated can reach 10kV, thereby can realize the secondary isolation of electronic type zero sequence CT, improve the fail safe that product is used.
In addition, the utility model adopts secondary CT technology to improve the signal measurement precision of electronic type zero sequence CT.The magnetic property of amorphous alloy material is very good, and on the former limit of non-crystaline amorphous metal magnetic guiding loop, around 5 circles, secondary is around 2000 circles, and secondary CT no-load voltage ratio is 400:1.One time, high-pressure side CT also adopts 400:1 no-load voltage ratio, and secondary CT can realize the undistorted transmission of the following unsymmetrical current of 40A or zero sequence current signal.
Below by specific embodiment, the implementation based on above-mentioned design is described:
The principle of the electronic type zero sequence CT of the present embodiment as shown in Figure 2, the electronic type zero sequence CT of the present embodiment comprises phase sequence CT, phase sequence CT comprises CT and secondary CT, the secondary winding of a CT is connected with a winding of secondary CT, described electronic type zero sequence CT comprises three phase sequence CT, the equal parallel resistance R of secondary winding of each phase sequence CT, each resistance R is connected successively.The phase sequence CT that comprises CT and secondary CT can be integrated into an electric component, the equal ground connection of winding of the secondary winding of a CT and secondary CT.This electronic type zero sequence CT being comprised of phase sequence CT and resistance R, because each phase sequence CT is arranged on a phase conductor, so installation and maintenance is all very convenient.Resistance R can certainly be incorporated in phase sequence CT.
The circuit theory of electronic type zero sequence CT is as follows:
1.IA, IB, IC are 10kV overhead transmission line electric currents, and the phase CT of flow through respectively three-phase conducting wire A, B, the upper installation of C, as a winding of a CT in phase CT.Phase CT comprises CT and secondary CT.The no-load voltage ratio of CT, a secondary CT is all selected 400A:1A, and precision can reach 0.5%.The iron core of a CT is drawn equipotential line, and equipotential line and 10kV wire are intertwined, and to meet safety regulations, realize equipotential.Equipotential line is welded on iron core and (is electrically connected to iron core).The output capacity of secondary CT is very little, and opening voltage is very low, need not design the protection of CT opening, also without ground connection.
2. respectively at the sample resistance R of the signal output part of A, B, a C three-phase CT similar resistance in parallel, then, by 3 R resistance series connection, can solve and learn that the both end voltage U0 of series resistance is proportional to zero-sequence current I0.Solution procedure is as follows:
The system zero-sequence current of setting up departments is
(vector), A phase current is
(vector), B phase current is
(vector), C phase voltage is
(vector), the R both end voltage of A phase secondary CT is
the R both end voltage of B phase secondary CT is
the R both end voltage of C phase secondary CT is
the no-load voltage ratio of CT and secondary CT is all 400:1, according to the definition of zero-sequence current,
?
(
be the connect vector expressions of later both end voltage U0 of 3 R resistance)
Resistance R is selected the metalfilmresistor of 100 Ω, 1/4W, 1% precision.When 10kV circuit normally moves, A, B, C three-phase load are in a basic balance, and three resistance R later voltage U 0 of connecting levels off to 0V.After single-phase earthing, Earth Phase CT is because detecting earth current, and this phase total current increases, this phase resistance R both end voltage increases, ungrounded phase resistance R both end voltage is substantially constant, and the both end voltage U0 that three resistance R are connected later increases, and by the A/D U0 signal of sampling, just can obtain zero-sequence current I0.
The electronic type zero sequence CT of the present embodiment has the good linearity, can meet 3% protection precision and fault detect requirement, will progressively substitute traditional zero sequence CT detection method at power distribution network.If require this electronic type zero sequence CT to reach 1% or 0.5% certainty of measurement, must adopt hardware or Software error compensation method, concrete methods of realizing is not the category of the utility model research.
The foregoing is only preferred embodiment of the present utility model; not in order to limit the utility model; all within spirit of the present utility model and principle, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection range of the present utility model.
Claims (6)
1. a novel electronic type zero sequence current transformer, it is characterized in that: comprise phase-sequence current instrument transformer, described phase-sequence current instrument transformer comprises primary current instrument transformer and secondary current instrument transformer, the secondary winding of described primary current instrument transformer is connected with a winding of described secondary current instrument transformer, described electronic type zero sequence current transformer comprises three described phase-sequence current instrument transformers, the equal parallel resistance R of secondary winding of each phase-sequence current instrument transformer, described in each, resistance R is connected successively.
2. a kind of novel electronic type zero sequence current transformer according to claim 1, it is characterized in that: also comprise the equipotential line being electrically connected to the iron core of primary current instrument transformer described in each, described equipotential line is wrapped on the wire through the iron core of described primary current instrument transformer.
3. a kind of novel electronic type zero sequence current transformer according to claim 1 and 2, is characterized in that: the no-load voltage ratio of described primary current instrument transformer is 400:1.
4. a kind of novel electronic type zero sequence current transformer according to claim 1 and 2, is characterized in that: the no-load voltage ratio of described secondary current instrument transformer is 400:1.
5. a kind of novel electronic type zero sequence current transformer according to claim 1, is characterized in that: described resistance R is selected the metalfilmresistor of 100 Ω, 1/4W, 1% precision.
6. a kind of novel electronic type zero sequence current transformer according to claim 1, is characterized in that: a winding of described secondary current instrument transformer is 5 circles, and secondary winding is 2000 circles.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420378430.2U CN204011024U (en) | 2014-07-09 | 2014-07-09 | A kind of novel electronic type zero sequence current transformer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420378430.2U CN204011024U (en) | 2014-07-09 | 2014-07-09 | A kind of novel electronic type zero sequence current transformer |
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| Publication Number | Publication Date |
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| CN204011024U true CN204011024U (en) | 2014-12-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201420378430.2U Expired - Fee Related CN204011024U (en) | 2014-07-09 | 2014-07-09 | A kind of novel electronic type zero sequence current transformer |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106098349A (en) * | 2016-08-12 | 2016-11-09 | 山东亿玛信诺电气有限公司 | Secondary side combination transformer not being afraid of open circuit and preparation method thereof |
| CN106158333A (en) * | 2016-02-02 | 2016-11-23 | 何排枝 | A kind of current transformer integrating device |
| CN106291038A (en) * | 2016-08-12 | 2017-01-04 | 山东亿玛信诺电气有限公司 | Secondary side current transformer not being afraid of open circuit and preparation method thereof |
| CN106783119A (en) * | 2017-01-03 | 2017-05-31 | 陈永山 | A kind of threephase current transformer |
-
2014
- 2014-07-09 CN CN201420378430.2U patent/CN204011024U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106158333A (en) * | 2016-02-02 | 2016-11-23 | 何排枝 | A kind of current transformer integrating device |
| CN106098349A (en) * | 2016-08-12 | 2016-11-09 | 山东亿玛信诺电气有限公司 | Secondary side combination transformer not being afraid of open circuit and preparation method thereof |
| CN106291038A (en) * | 2016-08-12 | 2017-01-04 | 山东亿玛信诺电气有限公司 | Secondary side current transformer not being afraid of open circuit and preparation method thereof |
| CN106783119A (en) * | 2017-01-03 | 2017-05-31 | 陈永山 | A kind of threephase current transformer |
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|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20141210 Termination date: 20170709 |