CN105161258A - Wide-range current transformer and gas gap length calculation method - Google Patents
Wide-range current transformer and gas gap length calculation method Download PDFInfo
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- CN105161258A CN105161258A CN201510624166.5A CN201510624166A CN105161258A CN 105161258 A CN105161258 A CN 105161258A CN 201510624166 A CN201510624166 A CN 201510624166A CN 105161258 A CN105161258 A CN 105161258A
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- 238000004364 calculation method Methods 0.000 title claims abstract description 23
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 85
- 238000004804 winding Methods 0.000 claims abstract description 19
- 239000011162 core material Substances 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 11
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 230000035699 permeability Effects 0.000 claims description 6
- 230000004907 flux Effects 0.000 claims description 5
- 230000005284 excitation Effects 0.000 claims description 3
- 230000009466 transformation Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
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Abstract
The invention provides a wide-range current transformer and a gas gap length calculation method. The transformer structurally comprises a primary winding, a secondary winding and iron cores. The iron cores are composed of the fixed iron core and the movable iron core. A gas gap is formed by disassociating the movable iron core with the transformer. The structure is simple, and implementation is convenient. When primary current of the current transformer is large, the magnetizing curves of the iron cores are located in a linear region by adjusting the gas gap length, the problem that because of saturation of the iron cores, errors are large is effectively solved, and iron core loss is reduced. The gas gap length calculation method and a current inductor error calculation formula are clear, and calculation and analysis are convenient.
Description
Technical Field
The invention belongs to the field of current transformers, and particularly relates to a structure for widening the measuring range of a current transformer by changing the length of an air gap of an iron core and a design method thereof.
Background
The current transformer is widely applied to the electric energy metering in the links of power generation, power transmission, power transformation and distribution of an electric power system, converts large current on the primary side into uniform small current on the secondary side, and the accuracy of metering, measurement and control is greatly influenced by the quality of the performance of the current transformer. Because the current of the power grid at different places and in different time periods is greatly different from several amperes to tens of thousands of amperes, in order to facilitate measurement, protection and control, the current transformer often needs to make different transformation ratios according to different measured primary current ranges, so that the secondary current is within a specified range.
If the core saturation is not considered, the ratio of the primary side current to the secondary side current is inversely proportional to the number of turns of the primary and secondary windings. Therefore, the conventional current transformer often has a plurality of taps disposed at different positions of the secondary winding, so as to select different transformation ratios for different measurement objects. However, in practice, due to the restriction of factors such as iron core materials, it is difficult for the current transformer with a fixed iron core structure to simultaneously ensure that the measuring working point is in the linear region of the magnetic density of the iron core when the large current transformation ratio and the small current transformation ratio are high, so that the measuring result is inaccurate, and the measuring precision is affected. Research and analysis show that when the magnetic density of the iron core is too small or is close to saturation, the working point of the current transformer can enter a nonlinear characteristic region of the iron core, so that not only is the waveform of the secondary current distorted, but also the current amplitude is influenced, and a large error is generated.
Disclosure of Invention
The invention provides a wide-range current transformer and an air gap length calculation method, aiming at solving the defects and shortcomings in the prior art, and the wide-range current transformer and the air gap length calculation method can ensure that the magnetic flux density of an iron core does not exceed a saturation value when primary current is maximum through adjusting the air gap length, and the iron core characteristic is always located in a linear region.
In order to solve the technical problem, the invention provides a wide-range current transformer which comprises a primary winding, a secondary winding and an iron core, wherein the iron core is composed of a fixed iron core and a movable iron core, and the movable iron core is pulled away from the transformer to form an air gap.
Preferably, the movable iron core comprises at least 1 movable iron core unit, and the movable iron core unit is drawn away from the transformer to form an air gap.
Preferably, the number of the movable iron core units is the number of the current transformer ranges minus 1, wherein the number of the current transformer ranges is at least 2.
A method for calculating the air gap length of a wide-range current transformer comprises the following steps:
step one, according to the perimeter L of the iron coretCalculating the length g of the air gap and the length L of the fixed iron corefAnd the length L of the movable coreaThe relationship is as follows:
Lt＝Lf+La+g＝πD
wherein D is the diameter of the iron core;
step two, the primary current range of the current transformer is 0-I1_maxThe maximum magnetic flux density allowed by the iron core material in the unsaturated region is BmaxAnd is from 0 to BmaxWithin the range, the relative permeability of the iron core is murThe air gap length g is then:
wherein N is1The number of primary side winding turns; mu.s0Air permeability; omega is the angular frequency of the current; s is the sectional area of the iron core of the current transformer; z2The value of converting the internal impedance of the secondary side winding to the primary side; zL' is the value of the secondary side load impedance converted to the primary side.
Preferably, the calculation process of the second step is specifically:
the primary side current is in the range of 0 to I1_maxThe corresponding secondary side current range is 0-I2_maxFrom the conservation of magnetomotive force, the following formula is derived:
wherein N is2The number of turns of the secondary side winding is;
solving by using an equivalent circuit of the current transformer, namely:
wherein Z ismIn order to be the excitation impedance,will ZmSubstituting the expression of (a) into the above equation yields:
preferably, the calculation method further includes an error calculation process.
Preferably, the error is calculated by measuring the primary side current in a range of 0 to I1_maxError of current transformer in this state when air gap length is gComprises the following steps:
wherein,the corresponding range of the primary side actual current value at any time is 0 to I1_Max；Measuring current for corresponding secondary sideThe value is obtained.
Preferably, the movable iron core comprises at least 1 movable iron core unit, and the movable iron core unit is drawn away from the transformer to form an air gap.
Preferably, the number of the movable iron core units is the number of the current transformer ranges minus 1, wherein the number of the current transformer ranges is at least 2.
The invention achieves the following beneficial technical effects: the wide-range current transformer provided by the invention is simple in structure and convenient to realize; when primary current is large, the current transformer can enable the magnetization curve of the iron core to be located in a linear region by adjusting the length of the air gap, effectively solves the problem of error increase caused by iron core saturation, and reduces iron core loss; the air gap length calculation method and the current transformer error calculation formula provided by the invention are clear and convenient to calculate and analyze.
Drawings
FIG. 1 is a schematic diagram of a current transformer according to the present invention;
FIG. 2 is a graph comparing the secondary current and primary current curves of a gapless current transformer and a gapped current transformer in accordance with an embodiment of the present invention.
Detailed Description
So that the technical features and technical contents of the present invention and technical effects achieved thereby can be better understood, the accompanying drawings of the present invention will be described in more detail with reference to the embodiments.
The invention is further described with reference to the following figures and examples.
As shown in fig. 1, the present invention provides a wide-range current transformer, which comprises a primary winding 1, a secondary winding 2 and an iron core, wherein the iron core is composed of a fixed iron core 3 and movable iron cores 4, and the length and the number of the movable iron cores 4 can be set according to actual requirements, so that the length of the movable iron cores 4 which are pulled away from the transformer to form air gaps 5 is also changed, and the magnetic flux density of the iron core still does not exceed a saturation value when the primary current is maximum, and the iron core characteristic is always located in a linear region. Preferably, the movable core 4 includes at least 1 movable core unit 40, so that different air gap lengths can be obtained when different numbers of movable core units 40 are extracted, the structure is simple, and the operation is convenient.
A method for calculating the air gap length of a wide-range current transformer comprises the following steps:
step one, according to the perimeter L of the iron coretCalculating the length g of the air gap and the length L of the fixed iron corefAnd the length L of the movable coreaThe relationship is as follows:
Lt＝Lf+La+g＝πD
wherein D is the diameter of the iron core;
secondly, the primary side current range of the current transformer is 0-I1_maxThe corresponding secondary side current range is 0-I2_maxThe maximum magnetic flux density allowed by the iron core material in the unsaturated region is BmaxAnd is from 0 to BmaxWithin the range of relative permeability of murFrom the conservation of magnetomotive force, the following formula is derived:
wherein N is2The number of secondary side winding turns.
Solving by using an equivalent circuit of the current transformer, namely:
wherein Z ismIn order to be the excitation impedance,will ZmSubstituting the expression of (c) into the above equation, the air gap length g is:
wherein N is1The number of primary side winding turns; mu.s0Air permeability; omega is the angular frequency of the current; s is the sectional area of the iron core of the current transformer; z2The value of converting the internal impedance of the secondary side winding to the primary side; zL' is the value of the secondary side load impedance converted to the primary side.
When the primary side current range is 0-I1_maxError of current transformer in this state when air gap length is gComprises the following steps:
wherein,the corresponding range of the primary side actual current value at any time is 0 to I1_Max；The current values are measured for the corresponding secondary side.
Preferably, the movable iron core 4 comprises at least 1 movable iron core unit, and the movable iron core unit is drawn away from the transformer to form an air gap.
Preferably, the relationship between the number of the movable iron core units and the number of the measuring ranges of the current transformer is as follows:
j＝i-1
wherein i is the number of the measuring ranges of the mutual inductor, and j is the number of the movable iron core units.
The specific embodiment is as follows:
in order to verify the effect of the wide-range current transformer and the air gap length calculation method provided by the invention, a finite element method is utilized to model and simulate a current transformer with an air gap-free iron core structure and the current transformer with a certain air gap iron core structure provided by the invention, wherein the air gap length obtained by drawing the current transformer with the air gap iron core structure away from a movable iron core unit is 5mm, and the comparison result is shown in figure 2.
The present invention has been disclosed in terms of the preferred embodiment, but is not intended to be limited to the embodiment, and all technical solutions obtained by substituting or converting equivalents thereof fall within the scope of the present invention.
Claims (9)
1. The wide-range current transformer is characterized in that: the transformer comprises a primary winding, a secondary winding and an iron core, wherein the iron core is composed of a fixed iron core and a movable iron core, and the movable iron core is pulled away from the transformer to form an air gap.
2. The wide-range current transformer of claim 1, wherein: the movable iron core comprises at least 1 movable iron core unit, and the movable iron core unit is pulled away from the mutual inductor to form an air gap.
3. The wide-range current transformer of claim 2, wherein: the number of the movable iron core units is the number of the current transformer ranges minus 1, wherein the number of the current transformer ranges is at least 2.
4. A method for calculating the air gap length of a wide-range current transformer is characterized by comprising the following steps: the method comprises the following steps:
step one, according to the perimeter L of the iron coretCalculating the length g of the air gap and the length L of the fixed iron corefAnd the length L of the movable coreaThe relationship is as follows:
Lt＝Lf+La+g＝πD
wherein D is the diameter of the iron core;
step two, the primary current range of the current transformer is 0-I1_maxThe maximum magnetic flux density allowed by the iron core material in the unsaturated region is BmaxAnd is from 0 to BmaxWithin the range, the relative permeability of the iron core is murThe air gap length g is then:
wherein N is1The number of primary side winding turns; mu.s0Air permeability; omega is the angular frequency of the current; s is the sectional area of the iron core of the current transformer; z2The value of converting the internal impedance of the secondary side winding to the primary side; zL' is the value of the secondary side load impedance converted to the primary side.
5. The wide-range current transformer air gap length calculation method of claim 4, wherein: the calculation process of the second step is specifically as follows:
the primary side current is in the range of 0 to I1_maxThe corresponding secondary side current range is 0-I2_maxFrom the conservation of magnetomotive force, the following formula is derived:
wherein N is2The number of turns of the secondary side winding is;
solving by using an equivalent circuit of the current transformer, namely:
wherein Z ismIn order to be the excitation impedance,will ZmSubstituting the expression of (a) into the above equation yields:
6. the wide-range current transformer air gap length calculation method of claim 4, wherein: the calculation method further includes an error calculation process.
7. The wide-range current transformer air gap length calculation method of claim 6, wherein: the error calculation process is that the primary side current range is 0-I1_maxError of current transformer in this state when air gap length is gComprises the following steps:
wherein,the corresponding range of the primary side actual current value at any time is 0 to I1_Max；The current values are measured for the corresponding secondary side.
8. The wide-range current transformer air gap length calculation method according to any one of claims 4 to 7, wherein: the movable iron core comprises at least 1 movable iron core unit, and the movable iron core unit is pulled away from the mutual inductor to form an air gap.
9. The wide-range current transformer air gap length calculation method of claim 8, wherein: the number of the movable iron core units is the number of the current transformer ranges minus 1, wherein the number of the current transformer ranges is at least 2.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106910596A (en) * | 2017-02-28 | 2017-06-30 | 南通壹选工业设计有限公司 | One kind prevents oversaturated current transformer |
| CN107741518A (en) * | 2017-11-15 | 2018-02-27 | 国网辽宁省电力有限公司鞍山供电公司 | A kind of cable shaft earth current test device of more opening joint testing currents |
| CN109698066A (en) * | 2019-03-06 | 2019-04-30 | 中国科学院重庆绿色智能技术研究院 | A kind of UI, UU type silicon steel sheet magnetic core band air gap inductance non-standard de-sign method |
| CN111880138A (en) * | 2020-08-19 | 2020-11-03 | 国网福建省电力有限公司 | Zero-sequence current transformer measurement accuracy optimization method based on ferromagnetic characteristics |
| CN116027245A (en) * | 2023-02-01 | 2023-04-28 | 广州市德珑电子器件有限公司 | Measuring method and system based on wide-range current transformer |
Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5392423A (en) * | 1977-01-25 | 1978-08-14 | Toshiba Corp | Core for current transformer |
| US4980794A (en) * | 1987-02-19 | 1990-12-25 | Westinghouse Electric Corp. | Electromagnetic contactor with lightweight wide range current transducer with sintered powdered metal core |
| JPH1022136A (en) * | 1996-06-28 | 1998-01-23 | Tokin Corp | Magnetic core |
| JP2002075747A (en) * | 2000-09-04 | 2002-03-15 | Mitsubishi Electric Corp | Gapped magnetic core and its manufacturing method |
| JP2002299128A (en) * | 2001-03-30 | 2002-10-11 | Nippon Chemicon Corp | Winding-type core |
| JP2003142319A (en) * | 2001-11-05 | 2003-05-16 | Nec Tokin Corp | Dust core, coil component, and power converter using them |
| CN202887907U (en) * | 2012-11-26 | 2013-04-17 | 哈尔滨理工大学 | Magnetic wedge type adjustable reactor |
| CN203351390U (en) * | 2013-07-05 | 2013-12-18 | 武汉伏特克电气工程有限公司 | Mechanical-adjusting adjustable reactor |
| CN203910418U (en) * | 2014-05-13 | 2014-10-29 | 江苏省电力公司南京供电公司 | Adjustable-power type electric reactor |
| CN205039036U (en) * | 2015-09-25 | 2016-02-17 | 国家电网公司 | Wide -range current transformer |
-
2015
- 2015-09-25 CN CN201510624166.5A patent/CN105161258A/en active Pending
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5392423A (en) * | 1977-01-25 | 1978-08-14 | Toshiba Corp | Core for current transformer |
| US4980794A (en) * | 1987-02-19 | 1990-12-25 | Westinghouse Electric Corp. | Electromagnetic contactor with lightweight wide range current transducer with sintered powdered metal core |
| JPH1022136A (en) * | 1996-06-28 | 1998-01-23 | Tokin Corp | Magnetic core |
| JP2002075747A (en) * | 2000-09-04 | 2002-03-15 | Mitsubishi Electric Corp | Gapped magnetic core and its manufacturing method |
| JP2002299128A (en) * | 2001-03-30 | 2002-10-11 | Nippon Chemicon Corp | Winding-type core |
| JP2003142319A (en) * | 2001-11-05 | 2003-05-16 | Nec Tokin Corp | Dust core, coil component, and power converter using them |
| CN202887907U (en) * | 2012-11-26 | 2013-04-17 | 哈尔滨理工大学 | Magnetic wedge type adjustable reactor |
| CN203351390U (en) * | 2013-07-05 | 2013-12-18 | 武汉伏特克电气工程有限公司 | Mechanical-adjusting adjustable reactor |
| CN203910418U (en) * | 2014-05-13 | 2014-10-29 | 江苏省电力公司南京供电公司 | Adjustable-power type electric reactor |
| CN205039036U (en) * | 2015-09-25 | 2016-02-17 | 国家电网公司 | Wide -range current transformer |
Non-Patent Citations (6)
| Title |
|---|
| 万千云, 赵智勇, 万英: "《电力系统运行技术》", 30 November 2007, 北京：中国电力出版社 * |
| 张凤鸽，易长松，杨德先: "《电力系统动态模拟技术》", 31 January 2014, 北京：机械工业出版社 * |
| 王世祥, 刘千宽: "《电流互感器二次回路现场验收及运行维护》", 31 May 2013, 北京：中国电力出版社 * |
| 王乐仁, 等: "电流互感器误差仿真的应用及其限制", 《高电压技术》 * |
| 腾晓红, 等: "保护用电流互感器各种不同准确级的要求及其设计要点", 《变压器》 * |
| 黄世泽, 等: "铁芯开气隙电流互感器暂态特性仿真", 《系统仿真学报》 * |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106910596A (en) * | 2017-02-28 | 2017-06-30 | 南通壹选工业设计有限公司 | One kind prevents oversaturated current transformer |
| WO2018157471A1 (en) * | 2017-02-28 | 2018-09-07 | 南通壹选工业设计有限公司 | Current transformer for use in preventing over-saturation |
| CN107741518A (en) * | 2017-11-15 | 2018-02-27 | 国网辽宁省电力有限公司鞍山供电公司 | A kind of cable shaft earth current test device of more opening joint testing currents |
| CN107741518B (en) * | 2017-11-15 | 2023-12-19 | 国网辽宁省电力有限公司鞍山供电公司 | Cable well grounding current testing device for multi-opening combined current testing |
| CN109698066A (en) * | 2019-03-06 | 2019-04-30 | 中国科学院重庆绿色智能技术研究院 | A kind of UI, UU type silicon steel sheet magnetic core band air gap inductance non-standard de-sign method |
| CN109698066B (en) * | 2019-03-06 | 2021-01-12 | 中国科学院重庆绿色智能技术研究院 | Non-standard design method for gap inductance of UI and UU type silicon steel sheet magnetic core belt |
| CN111880138A (en) * | 2020-08-19 | 2020-11-03 | 国网福建省电力有限公司 | Zero-sequence current transformer measurement accuracy optimization method based on ferromagnetic characteristics |
| CN111880138B (en) * | 2020-08-19 | 2022-11-08 | 国网福建省电力有限公司 | Zero-sequence current transformer measurement accuracy optimization method based on ferromagnetic characteristics |
| CN116027245A (en) * | 2023-02-01 | 2023-04-28 | 广州市德珑电子器件有限公司 | Measuring method and system based on wide-range current transformer |
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