A large-caliber AC and DC current sensor based on the zero-flux principle

Abstract

The present invention provides a large-caliber AC and DC current sensor based on the zero magnetic flux principle, wherein the magnetic core induction unit of the sensor includes two DC core windings, an AC core winding and a shielding structure; any of the DC core windings includes a DC core, a first bracket, a DC coil and a first shielding layer, and the two DC core windings are stacked up and down and shielded by the first shielding layer; the AC core winding includes an AC core, a second bracket, a compensation coil, an AC coil and a third bracket; the AC core is arranged in the second bracket and stacked on top of the two DC windings and shielded by the second shielding layer, and the outer layer is successively wound with the compensation coil and the AC coil and then shielded by the third shielding layer, and then arranged in the third bracket for packaging; the core diameter of the magnetic core induction unit meets the insulation requirement distance. Thus, the application occasions of measuring current on high voltage lines can be better met.

Description

[Technical field]

[0001] The invention relates to a current measuring device in a high voltage environment, in particular to an AC and DC current sensor based on the zero magnetic flux principle. [Background technology]

[0002] High current measurement is widely used in electrolysis plants, high-speed railways, electric vehicles and other fields. As a special instrument for measuring current, current sensors have received extensive attention in the field of high current precision measurement.

[0003] According to different measurement principles, current sensors can be divided into:

[0004] (1) Electromagnetic current sensor: The typical structure consists of an iron core and two windings (primary winding and secondary winding) wound on the iron core. According to the principle of electromagnetic induction, when current flows into the primary side, a magnetic field will be established on the iron core and an induced current will be generated on the secondary winding. Ideally, the product of the primary current and the number of primary winding turns will be equal to the product of the secondary current and the number of secondary winding turns, thereby achieving measurement. Due to its stable measurement and electrical isolation, it is the most widely used. However, it is easily affected by the magnetic saturation of the iron core and needs to be introduced into the current loop during measurement.

[0005] (2) Shunt: This method is mainly based on Ohm's law and uses a shunt with very small stray inductance and capacitance to convert current into voltage. However, due to the thermal effect of the shunt, it is difficult to ensure accuracy when the measured current is large.

[0006] (3) Rogowski coil, similar in structure to electromagnetic type, is made by winding a wire evenly around a non-magnetic material to form an induction coil. The induction coil surrounds the wire through which the current to be measured passes, thereby inducing the changing current. Rogowski coil has a wide frequency band and is not affected by the magnetic saturation of the iron core, but is affected by frequency and can only measure AC signals below the lower frequency cutoff frequency.

[0007] (4) Magneto-optical current sensor, mainly based on the Faraday effect, has a photosensitive element with the Faraday effect. When affected by the current magnetic field, the polarization plane of light will produce an angle rotation. Based on the relationship between the rotation angle and the current size, it can be used to measure the measured current. Magneto-optical current sensor also has a wide bandwidth and no magnetic saturation characteristics, but it is not conducive to the measurement of small currents.

[0008] (5) Giant magnetoresistance current sensor, mainly based on the giant magnetoresistance effect, in a multi-layer metal film several nanometers thick, the different spin states of current-carrying electrons and the different effects of the magnetic field will cause the resistance value to change. That is, the angle between the applied magnetic field and the sensor reference layer determines the resistance change of the metal film, which can be used to measure current. The giant magnetoresistance current sensor has a wide measurement band, but is easily affected by magnetic saturation.

[0009] (6) Fiber optic current sensor, as a phase modulation fiber optic sensor, converts the change of current into the change of light wave phase in the fiber, and detects the current passing through the sensing ring through coherent detection and digital closed-loop feedback technology. Fiber optic current sensor has the characteristics of good insulation performance, small size, light weight, large measurement range, good dynamic characteristics, full digitalization, and simultaneous measurement of AC and DC signals, but the measurement device is complex.

[0010] (7) Fluxgate current sensor uses the nonlinear relationship between the magnetic induction intensity and the magnetic field intensity of the high permeability core in the measured magnetic field under the saturation excitation of the alternating magnetic field to measure weak magnetic fields and thus measure current. Fluxgate current sensors have the characteristics of high accuracy, high resolution and high sensitivity.

[0011] The zero flux current sensor is a type of fluxgate sensor. Zero flux current sensors are widely used in power batteries and new energy vehicle industries, large medical equipment, urban rail transit industries, new energy power generation and other industries. Major domestic and foreign manufacturers include Switzerland LEM, Denmark DANISENSE, Germany GMC, Japan YOKOGAWA, Galaxy Electric, Jingheng Kedian, Xunleizhiyun, Beijing Senshe, Wuhan Tianrui, Ankerui, Nanjing Xinruipu, Nanjing Qihuo, Ningbo CRRC, etc. However, the existing zero flux current sensors are generally not large in diameter for passing through the current conductor to be measured. For example, the sensor DS1000UBSA with a rated current of 1000A produced by Denmark DANISENSE has a diameter of only 26.6mm at the sensor through-hole; the sensor DS2000IDLA with a rated current of 2000A has a diameter of only 68mm at the sensor through-hole. This through-hole diameter is only to meet the requirements of the measured conductor to pass through, and does not consider the safe insulation distance, so it cannot meet the insulation distance requirements when measuring current on high voltage lines. [Summary of the invention]

[0012] In view of this, the technical problem to be solved by the present invention is to provide a large-diameter AC and DC current sensor based on the zero magnetic flux principle. By redesigning the inner diameters of the three iron cores of the current sensor, the through-hole diameter meets the insulation requirement distance. Combined with the design of the insulating shielding structure, it can better meet the application scenarios of measuring current on high voltage lines.

[0013] In order to achieve the purpose of the aforementioned invention, the technical solution adopted by the embodiment of the present invention is: a large-caliber AC and DC current sensor based on the zero magnetic flux principle, the magnetic core sensing unit of the sensor includes two DC core windings, an AC core winding and a shielding structure;

[0014] The shielding structure comprises a first shielding layer, a second shielding layer and a third shielding layer, the first shielding layer is suspended and has no electrical connection, and the second shielding layer and the third shielding layer are grounded;

[0015] Any of the DC core windings comprises a DC core, a first bracket and a DC coil, wherein the DC core is arranged in the first bracket and the DC coil is wound on the first bracket; and the two DC core windings are stacked up and down and shielded by the first shielding layer;

[0016] The AC core winding comprises an AC core, a second bracket, a compensation coil, an AC coil and a third bracket; the AC core is arranged in the second bracket and is stacked on top of the two DC windings and is shielded by the second shielding layer to form a superimposed structure, the outer layer of the superimposed structure is sequentially wound with the compensation coil and the AC coil and then shielded by the third shielding layer, and then arranged in the third bracket for packaging to form a complete magnetic core induction unit;

[0017] The core diameter of the magnetic core induction unit meets the required insulation distance. Further, when the rated current of the large-diameter AC and DC current sensor is 1000A and the voltage of the high-voltage line is 10KV, the core diameter of the magnetic core induction unit is 70-88; when the rated current of the large-diameter AC and DC current sensor is 1000A and the voltage of the high-voltage line is 35KV, the core diameter of the magnetic core induction unit is 120-150.

[0018] Furthermore, the DC core is a circular core made of wound amorphous material; the AC core is a circular core made of Permalloy; the first bracket and the third bracket are both hard polytetrafluoroethylene shells; and the second bracket is a hard plastic shell.

[0019] The advantages of the present invention are: by adopting a customized iron core of special caliber and a design of a better insulation shielding structure, compared with existing current sensors of similar rated current levels, the present invention not only meets the same degree of accuracy level requirements, but also better meets the requirements for safe insulation distance when used for high-voltage line current measurement.

Brief Description of the Drawings

[0020] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0021] Figure 1 It is a schematic diagram of the iron core and winding of the zero flux current sensor of the present invention.

[0022] Figure 2 It is a schematic diagram of the circuit principle of the zero flux current sensor of the present invention.

[0023] Figure 3It is a schematic diagram of the cross-sectional structure of the magnetic core induction unit of the zero-flux current sensor of the present invention.

[0024] Figure 4 It is a schematic diagram of the structure of three iron cores of the zero flux current sensor of the present invention.

[0025] Figure 5 It is a structural schematic diagram of a magnetic core induction unit of a zero flux current sensor of the present invention. [Specific implementation method]

[0026] The embodiment of the present invention provides a large-caliber AC and DC current sensor based on the zero magnetic flux principle. By redesigning the inner diameters of the three iron cores of the current sensor, the through-core diameter meets the insulation requirement distance. Combined with the design of the insulating shielding structure, it better meets the application scenarios of measuring current on high voltage lines.

[0027] The technical solution in the embodiment of the present invention is to solve the above problems, and the overall idea is as follows: the present invention adopts a customized special-caliber iron core and a better insulation shielding structure design to better meet the requirements for safe insulation distance when applied to high-voltage line current measurement.

[0028] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0029] The zero flux current sensor of the present invention is a type of fluxgate sensor. The basic structure of the zero flux current sensor is a combination of a double-core magnetic modulation current comparator and an AC current comparator. Feedback compensation technology is used to ensure automatic ampere-turn balance of the main core, thereby achieving stable AC / DC closed-loop measurement.

[0030] See also Figure 1 The figure shows the core and winding schematic diagram of the zero flux current sensor, which mainly includes three cores, four winding coils, a zero flux detection module, an amplifier circuit module, an addition circuit module and an output circuit. The three cores are T1, T2 and T3, and the four winding coils include two excitation windings X1 / 1-X1 / 3 and X1 / 2-X1 / 4, a feedback winding X2 / 1-X2 / 2, and a compensation winding X2 / 3-X2 / 4.

[0031] The cores of the two excitation windings are made of the same magnetic material with equal cross-sectional area and magnetic path length. The measured current I P It is connected to all cores through the primary winding.

[0032] The two ends of the excitation winding with the same name are connected, that is, they are connected in anti-series, to ensure that the magnetic flux directions generated by the DC signal winding and the AC excitation winding on one of the cores are consistent, while the magnetic flux directions generated on the other core are just opposite, such as Figure 2 As shown. When the measured DC current Ip flows through the primary winding, a DC magnetic flux is generated on the two excitation cores. This DC magnetic flux will increase the magnetic flux of one and reduce the magnetic flux of the other. The nonlinear characteristics of the magnetic permeability of the magnetic core are used to detect the area sum of the magnetizing currents of the two coils in any half cycle through the circuit. This value changes monotonically with the change of Ip, so this value is the detection signal value of the DC current Ip. This signal is amplified to generate a compensation current Ic, which is fed back to the compensation coil to offset the magnetic flux generated by Ip on the two excitation cores, so that the DC component of the magnetic flux on the two excitation cores tends to 0, thereby reducing the detection signal value, and as a result, the magnetic flux generated by Ip and Ic on the two excitation cores is balanced. By measuring Ic through the output resistor RL, the measured current Ip can be obtained.

[0033] When the measured AC current Ip flows through the primary winding, the direct feedback winding induces an induced voltage signal which is input into the input of the amplifier, and also generates a compensation current Ic to offset the magnetic flux generated by Ip on the two excitation cores, so that the magnetic flux on the two excitation cores reaches a balance, thereby obtaining Ip.

[0034] Embodiment 1

[0035] like Figure 3 As shown, the magnetic core sensing unit 100 of the zero flux current sensor of the present invention mainly includes an iron core winding and a shielding structure 3. The iron core winding includes two DC iron core windings 1 and an AC iron core winding 2. The shielding structure 3 is interspersed in the iron core winding.

[0036] The shielding structure 3 includes a first shielding layer 31 , a second shielding layer 32 and a third shielding layer 33 . The first shielding layer 31 is suspended in the air without electrical connection, and the second shielding layer 32 and the third shielding layer 33 are grounded.

[0037] Any of the DC core windings 1 includes a DC core 11, a first bracket 12 and a DC coil 13, wherein the DC core 11 is arranged in the first bracket 12, and the DC coil 13 is wound on the first bracket 12; and the two DC core windings 1 are stacked up and down and shielded by the first shielding layer 31.

[0038] The AC core winding 2 includes an AC core 21, a second bracket 22, a compensation coil 23, an AC coil 24 and a third bracket 25; the AC core 21 is arranged in the second bracket 22 and is stacked on top of the two DC windings 1 and shielded by the second shielding layer 32 to form a superimposed structure, and the outer layer of the superimposed structure is sequentially wound with the compensation coil 23 and the AC coil 24 and then shielded by the third shielding layer 33, and then arranged in the third bracket 25 for packaging to form a complete magnetic core induction unit 100.

[0039] Among them, the first shielding layer 31 is used to shield the interference of the external magnetic field on the DC core 11, and the second shielding layer 32 is used to prevent the electrostatic field from interfering with the three cores; the first bracket 12, the second bracket 22 and the third bracket 25 can not only support and fix the core, but also further improve the insulation strength of the sensor through the selection of materials.

[0040] like Figure 4 and Figure 5 As shown, the core diameter 102 of the magnetic core sensing unit 100 meets the required insulation distance. In this embodiment, when the rated current of the large-diameter AC and DC current sensor is 1000A and the voltage of the high-voltage line is 10KV, the core diameter of the magnetic core sensing unit 100 is 70-88mm. This size of core diameter can fully meet the required insulation distance and will not have too much impact on the production process and material selection due to the large diameter. When selecting the iron core, on the premise of meeting the requirements of the core diameter 102, taking into account the size of the bracket, coil winding, and the setting of the shielding structure, the inner diameter of the DC core and the AC core can be 120mm, the outer diameter is 145mm, and the height is 25mm.

[0041] When the rated current of the large-caliber AC and DC current sensor is 1000A and the secondary current is 1A, the DC coil and the compensation coil both have 250 turns, and the AC coil has 1000 turns.

[0042] The DC core 11 is a circular core made of wound amorphous material, and the AC core 21 is a circular core made of Permalloy. The combination of these two materials can meet the requirements of better magnetic permeability, thereby making the sensor test more accurate and improving the sensitivity.

[0043] The first bracket 12 and the third bracket 25 are both made of hard polytetrafluoroethylene shells; polytetrafluoroethylene material has high hardness and good insulation strength, and can usually provide 10 12～15 The insulation strength of the sensor can be further improved.

[0044] The second bracket is a hard plastic shell, thereby providing better support for the AC core.

[0045] Embodiment 2

[0046] The difference between the second embodiment and the first embodiment is that the first embodiment is used to adapt to the test when the voltage of the high-voltage line is 10KV, while the second embodiment is used to adapt to the test when the voltage of the high-voltage line is 35KV. Therefore, the difference in structure is:

[0047] When the rated current of the large-diameter AC and DC current sensor is 1000A and the voltage of the high-voltage line is 35KV, the core diameter of the magnetic core induction unit is 120-150mm. Similarly, this size of core diameter can fully meet the insulation distance requirements, and will not have too much impact on the factory's process and material selection due to the large diameter. When selecting the iron core, on the premise of meeting the requirements of the core diameter, taking into account the size of the bracket, coil winding, and the setting of the shielding structure, the inner diameter of the DC core and the AC core can be 180mm, the outer diameter is 210mm, and the height is 30mm.

[0048] The advantages of the present invention are: by adopting a customized iron core of special caliber and a design of a better insulation shielding structure, compared with existing current sensors of similar rated current levels, the present invention not only meets the same degree of accuracy level requirements, but also better meets the requirements for safe insulation distance when used for high-voltage line current measurement.

[0049] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A large-caliber AC and DC current sensor based on the zero flux principle, Features: The magnetic core sensing unit of the sensor includes two DC core windings, an AC core winding and a shielding structure; The shielding structure comprises a first shielding layer, a second shielding layer and a third shielding layer, the first shielding layer is suspended and has no electrical connection, and the second shielding layer and the third shielding layer are grounded; Any of the DC core windings comprises a DC core, a first bracket and a DC coil, wherein the DC core is arranged in the first bracket and the DC coil is wound on the first bracket; and the two DC core windings are stacked up and down and shielded by the first shielding layer; The AC core winding comprises an AC core, a second bracket, a compensation coil, an AC coil and a third bracket; the AC core is arranged in the second bracket and is stacked on top of the two DC coils and shielded by the second shielding layer to form a superimposed structure, the outer layer of the superimposed structure is sequentially wound with the compensation coil and the AC coil and then shielded by the third shielding layer, and then arranged in the third bracket for packaging to form a complete magnetic core induction unit; The core diameter of the magnetic core induction unit meets the insulation requirement distance: When the rated current of the large-caliber AC and DC current sensor is 1000A and the voltage of the high-voltage line is 10KV, the core diameter of the magnetic core induction unit is 70-88mm, and the inner diameter of the DC core and the AC core is 120mm, the outer diameter is 145mm, and the height is 25mm; When the rated current of the large-diameter AC and DC current sensor is 1000A and the voltage of the high-voltage line is 35KV, the core diameter of the magnetic core induction unit is 120-150mm, and the inner diameter of the DC core and the AC core is 180mm, the outer diameter is 210mm, and the height is 30mm.

2. A large-caliber AC and DC current sensor based on the zero magnetic flux principle as claimed in claim 1, Features: The DC core is a toroidal core made of wound amorphous material. The AC iron core is a ring iron core made of Permalloy; The first bracket and the third bracket are both hard polytetrafluoroethylene shells; The second bracket is a hard plastic shell.

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