CN212209198U - Passive zero-flux wide-range current transformer for metering - Google Patents
Passive zero-flux wide-range current transformer for metering Download PDFInfo
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- CN212209198U CN212209198U CN202020479780.3U CN202020479780U CN212209198U CN 212209198 U CN212209198 U CN 212209198U CN 202020479780 U CN202020479780 U CN 202020479780U CN 212209198 U CN212209198 U CN 212209198U
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Abstract
The utility model discloses a passive zero magnetic flux's wide range current transformer for measurement, including mutual-inductor core, mutual-inductor winding, the mutual-inductor core is including main iron core and power winding core, and the mutual-inductor core is hollow cylinder, the mutual-inductor winding includes primary winding, first secondary winding, second secondary winding, third secondary winding, first secondary winding, second secondary winding evenly wind on main iron core, and third secondary winding evenly winds on power winding iron core, and second secondary winding and third secondary winding form closed circuit around to opposite, series connection each other, main iron core and power winding core are parallel and the center passes primary winding. The utility model discloses a current transformer for measurement that has wider range, the higher degree of accuracy. In addition, the rimless zero-flux current transformer does not need an external power supply, and is low in cost and easier to popularize.
Description
Technical Field
The utility model relates to a mutual-inductor technical field, concretely relates to system's electric current is in rated current's 1 thousandth ~ 200% full range, and the whole wide range current transformer for measurement that can accurate switching signal's passive zero magnetic flux.
Background
Current transformers are one of the key devices in power systems. The high-current signal in a primary system of a power grid can be converted into a standard low-current signal (1A or 5A) with high accuracy according to a specified proportion, the standard low-current signal is used for a secondary metering, measuring and protecting system which is connected in sequence, and the conversion precision of a current transformer is closely related to the trade settlement accuracy of electricity charges, the collection of power grid operation data, the monitoring of an operation state and the operation safety of the power grid.
According to the regulations of the national standard GB/T20840 of the transformer, the highest accuracy level of the current transformer for metering adopted in the current power system is 0.2S level, and the accuracy range and the limit value are shown in figure 1. It can be seen that the accuracy of the transformer metering is gradually reduced below the rated current of 20%. Actually, the variation range of the load of many users is very large, such as manufacturing enterprises, electric locomotives, residential quarters and the like, because of the full-load operation, the primary current is very large, so the rated current of the current transformer for metering is set according to the full-load current, when large electric equipment of an enterprise stops operation, an electric locomotive passes through, and the residence rate of a residential quarter is low, the actually used current may be far lower than 20% or even lower than 1% of the set rated current of the transformer, which causes inaccurate electricity charge metering, and the transformer principle and experience data show that the descending trend is that the ratio difference is negative, the phase difference is positive, and the overall performance is that the metered electricity charge is reduced, so the current transformer in the prior art can not meet the metering requirement under the condition. Official network display data of the national grid company: the annual electricity selling amount is 36051 hundred million kilowatt hours, the line loss rate reaches 6.75 percent, and the annual electricity loss amount exceeds 2433 million kilowatt hours.
In summary, a transformer capable of accurately measuring current when the primary current is far lower than the rated current of the transformer by 1% is realized, and the problem to be solved in the field of power grid electricity charge measurement is urgent.
The patent application with publication number CN 209198521U discloses a zero-flux high accuracy zero sequence current transformer, including mutual-inductor core, mutual-inductor winding and compensating circuit, the mutual-inductor core includes main iron core and supplementary iron core, the mutual-inductor winding includes secondary current winding, zero-flux detection winding and compensation winding, zero-flux detection winding evenly winds on main iron core, compensation winding evenly winds on supplementary iron core, has the main iron core of zero-flux detection winding and has the supplementary iron core of compensation winding and bonds side by side, secondary current winding evenly winds on main iron core and supplementary iron core after the bonding, compensating circuit links to each other with zero-flux detection winding, compensation winding respectively.
Although the transformer with zero magnetic flux is disclosed, the transformer with zero magnetic flux has the problems of high cost, high requirement on use environment, necessity of an external power supply for controlling the power supply of a circuit and the like, so that the product is difficult to be applied to a power system on a large scale.
Therefore, aiming at the defects of the prior art, how to realize the low-cost wide-range current transformer for metering is a problem to be solved urgently in the field.
SUMMERY OF THE UTILITY MODEL
The utility model aims at prior art's defect, provide a current transformer is used in wide range measurement of passive zero magnetic flux. The rimless zero-flux current transformer is utilized, an external power supply is not needed, and the realization cost is low and the popularization is easier.
In order to realize the above purpose, the utility model adopts the following technical scheme:
the utility model provides a wide range of passive zero magnetic flux measures and uses current transformer which characterized in that includes:
the transformer comprises a transformer iron core and a transformer winding, wherein the transformer iron core comprises a main iron core and a power supply winding iron core, the transformer iron core is a hollow cylinder, the transformer winding comprises a primary winding, a first secondary winding, a second secondary winding and a third secondary winding, the first secondary winding and the second secondary winding are uniformly wound on the main iron core, the third secondary winding is uniformly wound on the power supply winding iron core, the second secondary winding and the third secondary winding are oppositely wound and are mutually connected in series to form a closed loop, and the main iron core and the power supply winding iron core are arranged side by side and the center of the main iron core and the power supply winding iron core penetrates through the primary winding.
Further, the magnetic potential balance equation of the main core is as follows:
wherein the primary current through the primary winding is
The secondary current through the first secondary winding is
The current passing through the second secondary winding and the third secondary winding is
Excitation current of
The number of turns of the primary winding is N1The number of turns of the first secondary winding and the second secondary winding is N2、N3。
Further, the power winding iron core is:
wherein N is4The number of turns of the third secondary winding.
Further, the number of turns of the second secondary winding N3And the number of turns N of the third secondary winding4Satisfies the following conditions:
furthermore, the first secondary winding is a secondary output winding, and the first end and the last end of the first secondary winding are led out to a secondary wiring terminal.
Furthermore, the first end and the last end of the primary winding are connected with a primary wiring terminal.
Furthermore, iron core insulation and buffering are arranged on the surface of the transformer iron core.
Further, the transformer winding is provided with external insulation.
The utility model provides a wide range of zero magnetic flux of rimless current transformer for measurement has solved the great user of load variation in the electric wire netting, when being less than rated current 1% or surpassing rated current 120% operation, the measurement is inaccurate, influences the difficult problem of trade settlement, current transformer working range in rated current 1 thousandth ~ 200%, be the current transformer for measurement that has wider range, higher degree of accuracy. Furthermore, the utility model discloses a realization of zero magnetic flux of indifference does not need external power supply, and is with low costs and convenient to use, has high using value.
Drawings
FIG. 1 is an exemplary illustration of a ratio difference value for a conventional current transformer;
FIG. 2 is an electrical schematic diagram of a passive zero flux wide range current transformer for metering;
FIG. 3 is a schematic diagram of a three-dimensional structure of a passive zero-flux wide-range current transformer for metering;
FIG. 4 is a schematic plan view of a passive zero flux wide range current transformer for metering;
fig. 5 is a performance comparison example diagram of the current transformer for passive zero-flux wide-range metering and the current transformer for current metering of the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The present invention can also be implemented or applied through other different specific embodiments, and various details in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic concept of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the form, amount and ratio of the components in actual implementation may be changed at will, and the layout of the components may be more complicated.
The present invention will be further described with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.
In the current sensor, a primary current is set to
A secondary current of
Excitation current of
A secondary impedance of Z2Secondary induction potential is E2Excited magnetic potential (IN)0The first ampere-turn of the primary current Is (IN)1Magnetic flux density in the core is B, magnetic field strength is H, magnetic permeability of the core material is mu, and average magnetic path length in the coreIs L, KFIs a constant determined by the horizontal coefficient of the iron core manufacturing process, and the magnetic potential balance equation of the current transformer is as follows according to the magnetic potential balance principle
Wherein N is1Is the number of turns in the primary winding and N2 is the number of turns in the secondary winding.
Under the ideal condition, the iron core of the current transformer does not consume active power and does not need reactive power excitation, and at the moment,
it can be derived that:
that is, the current ratio of the current transformer in the ideal state is the turn ratio, and there is no error. However, in the actual current transformer, to generate an induced electromotive force in the secondary winding, excitation current is required to supply excitation and power loss to the core, that is,
this generates an error in the secondary output of the current transformer. The errors are divided into a ratio difference (%) and a phase difference ('), and the theoretical calculation values are:
wherein alpha is Z2θ is the core loss angle.
While
The error and the excitation current I of the mutual inductor can be obtained by combining the formula0Is positively correlated when excited by an excitation current I0When the error is reduced, the error range is narrowed, i.e. the accuracy is higher. Thus, the excitation current I is reduced0Is the core of the utility model.
The utility model provides a current transformer is used in wide range measurement of passive zero magnetic flux, include:
the transformer comprises a transformer iron core and a transformer winding, wherein the transformer iron core comprises a main iron core and a power supply winding iron core, the transformer iron core is a hollow cylinder, the transformer winding comprises a primary winding, a first secondary winding, a second secondary winding and a third secondary winding, the first secondary winding and the second secondary winding are uniformly wound on the main iron core, the third secondary winding is uniformly wound on the power supply winding iron core, the second secondary winding and the third secondary winding are oppositely wound and are mutually connected in series to form a closed loop, and the main iron core and the power supply winding iron core are arranged side by side and the center of the main iron core and the power supply winding iron core penetrates through the primary winding.
Specifically, as shown in fig. 2, the utility model discloses a passive zero magnetic flux's wide range is current transformer for measurement is equipped with two iron cores, and the A iron core is main iron core, and the B iron core is power winding iron core. The A iron core is wound with two secondary windings with the number of turns of N2、N3，N2The winding is a secondary output winding, and the number of turns of the current transformer winding is N2The head end and the tail end of the secondary output winding are led out to secondary wiring terminals which are respectively a head end s1 and a tail end s 2. A secondary winding is wound on the B iron core and used as a power supply winding, and the number of turns is N4，N3、N4The winding directions of the windings are opposite, the windings are mutually connected in series to form a closed loop, the two iron cores are arranged in parallel, the iron core of the mutual inductor is a hollow cylinder, the center of the mutual inductor penetrates through the primary winding, and the number of primary turns is N1And the first end and the last end of the primary winding P1 and P2 are connected with a primary connecting terminal.
Fig. 3 shows a three-dimensional structure diagram of the current transformer, wherein an iron core a and an iron core B are arranged in parallel and are in the shape of a hollow cylinder. The center of the primary winding penetrates through the centers of the primary winding side by side, P1 and P2 are the head end and the tail end of the primary winding, and S1 and S2 are the head end and the tail end of the secondary output winding.
The utility model provides a wide range of passive zero magnetic flow measures uses current transformer, passive zero magnetic flow adopts two iron core structures, and B unshakable in one's determination provides exciting current for main core A, makes the effect of main core self realization zero magnetic flow, has improved the degree of accuracy and the range of product. The main iron core is wound with two secondary windings with the number of turns N2For secondary output winding, number of winding turns N3To compensate for the excitation current winding. The iron core B is a power supply winding, is opposite to the winding direction of a compensation excitation current winding in the iron core A, is connected in series, and provides excitation current for the main iron core A.
The utility model discloses be provided with the iron core insulation and the buffering of buffering usefulness, for example crepe paper or insulating adhesive tape on mutual-inductor iron core surface. And external insulation is also arranged outside the winding.
Fig. 4 shows a schematic plan view of a current transformer. The transformer comprises a core 1, a core 2, a winding 4, a winding outer insulation 5, a secondary output lead 6, a secondary output terminal 7, a main core 7, a first secondary winding 8, a power supply winding core 9, a third secondary winding 10, a second secondary winding 11, a primary winding 12 and a primary wiring board 13.
Setting the primary current through the primary winding to
The secondary current through the first secondary winding is
The current passing through the second secondary winding and the third secondary winding is
The equilibrium equation of the magnetic potential in the core A is
To obtain
Since the iron core B is only used for compensating the excitation current for the iron core A, the excitation current of the iron core B can be ignored, and the excitation current of the iron core B can be obtained
General formula
In
Carry-in type
To get
Due to N3、N4The winding directions are opposite, and the exciting current of the alloy iron core
Has a small value, for this reason, when
And are connected with
Value matching can ensure
So that
And further, when the primary current power grid is lower than 1% or higher than 120% of rated current, the current transformer for metering can also meet the requirement of high precision.
Specifically, the utility model discloses the B winding number of turns N unshakable in one's determination4Is far greater than the number N of winding turns connected with the main iron core A in series3The purpose of compensating the exciting current in the main iron core A without influencing the normal accuracy output is achieved. The utility model discloses a pair
The value of the main core A is not limited, the value can be adjusted along with different products, the compensation of the excitation current of the main core A is realized, the excitation current of the main core is not required to be provided by the primary winding current of the main core, the purposes of higher accuracy and wider range are achieved, and the main characteristic is that the product cost is low, an external power supply is not required, and the main core A is suitable for the requirement of a power distribution power system. Preferably, the utility model discloses set for
Fig. 5 shows the adoption the utility model provides a current transformer measuring degree of accuracy index and measurement range, can know by fig. 5, the utility model discloses be higher than the 0.2S level product of current standard far away.
Therefore, the utility model discloses the wide range of the zero magnetic flux of the nothing is measured and is used current transformer's operating range in rated current 1 thousandth ~ 200%, and the utility model discloses a have the current transformer for measurement of wider range, the higher degree of accuracy. Furthermore, the utility model discloses realize that the zero magnetic flux current transformer of indifference does not need external power supply, realizes with low costs, changes the popularization.
It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.
Claims (8)
1. The utility model provides a wide range of passive zero magnetic flux measures and uses current transformer which characterized in that includes:
the transformer comprises a transformer iron core and a transformer winding, wherein the transformer iron core comprises a main iron core and a power supply winding iron core, the transformer iron core is a hollow cylinder, the transformer winding comprises a primary winding, a first secondary winding, a second secondary winding and a third secondary winding, the first secondary winding and the second secondary winding are uniformly wound on the main iron core, the third secondary winding is uniformly wound on the power supply winding iron core, the second secondary winding and the third secondary winding are oppositely wound and are mutually connected in series to form a closed loop, and the main iron core and the power supply winding iron core are arranged side by side and the center of the main iron core and the power supply winding iron core penetrates through the primary winding.
2. The current transformer of claim 1, wherein the magnetic potential balance equation of the main core is:
wherein the primary current through the primary winding is
The secondary current through the first secondary winding is
The current passing through the second secondary winding and the third secondary winding is
Excitation current of
The number of turns of the primary winding is N1The number of turns of the first secondary winding and the second secondary winding is N2、N3。
3. The current transformer of claim 2, wherein the power winding core is:
wherein N is4The number of turns of the third secondary winding.
4. The current transformer of claim 3, wherein the second number of secondary winding turns, N3And the number of turns N of the third secondary winding4Satisfies the following conditions:
5. the current transformer of claim 1, wherein the first secondary winding is a secondary output winding having first and second ends leading to secondary terminals.
6. The current transformer of claim 1, wherein the first and second ends of the primary winding are connected to primary terminals.
7. The current transformer according to claim 1, wherein a surface of said transformer core is provided with core insulation and cushioning.
8. The current transformer of claim 1, wherein the transformer winding is provided with external insulation.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020479780.3U CN212209198U (en) | 2020-04-03 | 2020-04-03 | Passive zero-flux wide-range current transformer for metering |
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| CN202020479780.3U CN212209198U (en) | 2020-04-03 | 2020-04-03 | Passive zero-flux wide-range current transformer for metering |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111540574A (en) * | 2020-04-07 | 2020-08-14 | 浙江天际互感器有限公司 | Wide-range current transformer and manufacturing method thereof |
| CN114089011A (en) * | 2021-11-30 | 2022-02-25 | 江苏科兴电器有限公司 | Zero magnetic flux current transformer |
| CN114113737A (en) * | 2021-11-30 | 2022-03-01 | 江苏科兴电器有限公司 | 150kV zero-flux direct current transformer |
-
2020
- 2020-04-03 CN CN202020479780.3U patent/CN212209198U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111540574A (en) * | 2020-04-07 | 2020-08-14 | 浙江天际互感器有限公司 | Wide-range current transformer and manufacturing method thereof |
| CN114089011A (en) * | 2021-11-30 | 2022-02-25 | 江苏科兴电器有限公司 | Zero magnetic flux current transformer |
| CN114113737A (en) * | 2021-11-30 | 2022-03-01 | 江苏科兴电器有限公司 | 150kV zero-flux direct current transformer |
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Address after: No. 8, Jingtian Road, Jiangshan Economic Development Zone, Jiangshan City, Quzhou City, Zhejiang Province 324102 Patentee after: Zhejiang Tianji Instrument Transformer Co.,Ltd. Address before: No.2, Shanhai Road, Shanhai cooperation zone, Jiangshan Economic Development Zone, Quzhou City, Zhejiang Province Patentee before: ZHEJIANG HORIZON INSTRUMENT TRANSFORMERS Co.,Ltd. |
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