CN113552401A - High-frequency current sensor adopting auxiliary winding degaussing and discharge current detection method - Google Patents
High-frequency current sensor adopting auxiliary winding degaussing and discharge current detection method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a high-frequency current sensor adopting an auxiliary winding for degaussing, which comprises a magnetic core and a main winding NTAnd an auxiliary degaussing winding, the main winding NTAnd the auxiliary degaussing winding is wound on the magnetic core, and the main winding NTThe discharge current is obtained by connecting the discharge current with an external signal processing circuit; the auxiliary degaussing winding is composed of N turnsSAny one of a winding composed of a single-turn winding, a winding composed of a plurality of windings having the same number of turns, a winding composed of a plurality of windings having different numbers of turns, and a winding composed of a plurality of short-circuit rings; the invention also discloses a discharge current detection method, which specifically comprises the following steps: when the primary side of the high-frequency current sensor flows the power frequency current ipWhen the auxiliary demagnetization winding induces currents with corresponding magnitude, the sum sigma i of the currentss≈ipTo offset the primary side power frequency current ipExcitation of (3); through the main winding NTAnd the detection circuit is connected with an external signal processing circuit to realize discharge current detection.
Description
Technical Field
The invention belongs to the technical field of current measurement, and particularly relates to a current sensor and a current detection method capable of effectively transmitting high-frequency small current components under the background of power frequency or low-frequency large current.
Background
When the electrical equipment runs for a long time, the temperature can be kept higher, the insulating material becomes brittle and aged, the insulating property is reduced, the discharge phenomenon is easy to occur inside or on the surface of the insulating material of the electrical equipment, and the discharge phenomenon existing in an insulating medium is a complex electrical process. Although it has a small discharge energy and does not directly break down the insulation, it can cause partial damage to the dielectric. When the insulation material is used all the time, the insulation material can be changed in quality and completely broken down under special environment, so that the normal operation of electrical equipment is influenced, and safety accidents are caused.
At present, there are various methods for detecting discharge current, among which the pulse current detection method is the earliest studied and most widely used. The measurement principle is as follows: when a discharge occurs, this causes a movement of the charge, which generates a pulsed current (in the order of mA) in the peripheral measuring circuit, which is detected to enable the measurement of the discharge current.
The existing current sensor is used for detecting the discharge current, and has certain limitation and deficiency in use.
1. The Rogowski coil, a current sensor for detecting the current of a high-voltage side or a transmission line, is generally mainly used for measuring large current, overload current and short-circuit current, and because of the hollow coil, the magnetic core cannot be saturated when the power frequency is large current, but if the Rogowski coil is used for detecting discharge current, the sensitivity is low, and the requirement of milliampere-level high-frequency current measurement cannot be met.
2. A high frequency current sensor for ground side discharge current detects can satisfy milliampere level high frequency current measurement sensitivity requirement, but if be used for high-voltage side or power transmission line time, power frequency operating current can lead to the magnetic core saturation, can not normally pass and become under the power frequency heavy current condition.
Therefore, a high-frequency current sensor is needed, which can eliminate the influence of power frequency current and detect the high-frequency discharge current of mA level. There is currently no relevant technology that meets the needs.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the problem that a discharge current signal is difficult to effectively extract from a large-current working current when a high-frequency current sensor is used on the high-voltage side of a transformer or a transmission line, the invention provides a high-frequency current sensor adopting an auxiliary winding for demagnetization and a current detection method, and the effective transmission of a high-frequency small current component is realized under the background of power frequency or low-frequency large current.
The technical scheme is as follows: a high-frequency current sensor adopting auxiliary winding for degaussing comprises a magnetic core and a main winding NTAnd an auxiliary degaussing winding, the main winding NTThe auxiliary degaussing winding is wound on the magnetic core;
the main windingGroup NTThe discharge current is obtained by connecting the discharge current with an external signal processing circuit;
the auxiliary degaussing winding is composed of N turnsSThe coil may be any one of a coil formed of a single-turn coil, a coil formed of a plurality of coils having the same number of turns, a coil formed of a plurality of coils having different numbers of turns, and a coil formed of a plurality of short-circuit rings.
Further, the main winding NTAnd the discharge current is obtained by connecting the non-inductive resistor with an external signal processing circuit.
Further, each output of the auxiliary degaussing winding is short-circuited.
Furthermore, each output of the auxiliary degaussing winding is externally connected with an inductor.
Furthermore, each output of the auxiliary degaussing winding is short-circuited and connected with the magnetic ring in series.
Further, the main winding NTAnd an auxiliary degaussing winding wound on the frame and provided with a main winding NTAnd a distance is kept between the framework of the auxiliary degaussing winding and the magnetic core.
The invention provides a discharge current detection method based on the high-frequency current sensor adopting the auxiliary winding for demagnetization, which specifically comprises the following steps:
when the primary side of the high-frequency current sensor flows the power frequency current ipWhen the auxiliary demagnetization winding induces currents with corresponding magnitude, the sum sigma i of the currentss≈ipTo offset the primary side power frequency current ipExcitation of (3);
through the main winding NTAnd the detection circuit is connected with an external signal processing circuit to realize discharge current detection.
Has the advantages that: compared with the prior art, the invention has the following advantages:
(1) the high-frequency current sensor adopting the auxiliary winding for demagnetization can transmit milliampere high-frequency current signals under the background of hundreds and thousands of amperes of power frequency current;
(2) the high-frequency current sensor adopting the auxiliary winding for demagnetization has obvious counteraction effect on primary side power frequency current, and can reach 1V/1000A magnitude, namely the induced voltage of 1000A power frequency current is less than 1V;
(3) the high-frequency current sensor for demagnetization of the auxiliary winding can detect a discharge current signal with a frequency band of hundreds of K to tens of M hertz, and the measuring frequency range of the sensor can be adjusted by adjusting the material of the magnetic core;
(4) the multi-winding or short-circuit ring demagnetization is beneficial to reducing the influence of winding parasitic capacitance on the high-frequency transmission characteristic of the sensor, the fault tolerance is stronger, and the reliability of the corresponding primary side power frequency current offset is higher;
(5) the auxiliary windings output short circuits or are externally connected with elements such as inductors, magnetic beads and the like, the short circuit effect on low-frequency current is obvious, and the short circuit effect on high-frequency current is limited due to leakage inductance of the auxiliary windings and impedance of the elements such as the externally connected inductors, the magnetic beads and the like; the auxiliary winding is adopted for demagnetization, so that the influence of the winding parasitic capacitance on a high-frequency current signal can be reduced, and the high-frequency transmission characteristic is improved. Generally, the transmission ratio (voltage/current) of the high-frequency current can reach at least 1V/A, namely, the induced voltage of the current signal of 1mA can reach 1 mV.
Drawings
FIG. 1 is a schematic wiring diagram of a conventional high-frequency current sensor;
FIG. 2 is a schematic diagram of a single winding, multiple windings and short circuit ring degaussing connection;
FIG. 3 is a schematic diagram of demagnetization wiring of a single winding, multiple windings and a short-circuit loop connection inductor or a series of magnetic rings;
fig. 4 is a schematic diagram of a current sensor for auxiliary winding degaussing.
Detailed Description
The technical solution of the present invention will be further explained with reference to the accompanying drawings and embodiments.
Referring to fig. 1, when the conventional high-frequency current sensor is used on a high-voltage side or a power line, the primary side operating current easily causes saturation of the sensor core, which makes the measurement impossible.
As shown in fig. 2, 3 and 4, the core of the high-frequency current sensor employing auxiliary winding degaussing is in the design of winding, the winding includes a main winding and an auxiliary degaussing winding, the main winding and the auxiliary degaussing winding are both wound around a magnetic core, and the main winding and the auxiliary degaussing winding are located at different positions of a magnetic ring, and the area occupied by the main winding is usually small; the number of turns and the wire diameter of the main winding and the auxiliary demagnetizing winding are determined according to the rated working current of the primary side, the main winding and the auxiliary demagnetizing winding are normally wound in a forward direction without overlapping, and in order to reduce parasitic capacitance, the windings can be wound on the framework and keep a certain distance from the magnetic core. According to the application, the magnetic core in the current sensor can adopt a whole ring, two semi-rings or a magnetic core in other shapes or spliced by a plurality of blocks, the size of the magnetic core is determined according to the application, the magnetic core in the current sensor usually adopts ferrite with good high-frequency characteristics, and the magnetic core can also adopt other magnetic cores made of materials with better high-frequency characteristics.
The main winding functions similarly to a conventional high-frequency current sensor, the main winding NTThe output is generally connected with a noninductive resistor of dozens of ohms, or not connected with the resistor, a signal processing circuit is directly sent by adopting a shielding twisted pair or a coaxial cable, and the current on a main winding is relatively small (mA level).
Referring to fig. 2, the auxiliary degaussing winding may be made of enameled wire or insulated wire, and may have N turnsSThe single-turn winding may be a plurality of windings N1-Nn with the same number of turns, or a plurality of windings with different numbers of turns, and the number of corresponding turns is k 1-kn, or may be a plurality of (number N) single-turn windings (called short-circuit rings), and these windings have the common characteristic of low-frequency impedance, and each winding output in the auxiliary degaussing winding can be directly short-circuited, or connected with an inductor, or short-circuited and connected in series with a magnetic ring, so as to improve the impedance at high frequency, as shown in fig. 2 to 4, where Lr 1-Lrn in fig. 4 are parasitic inductors or external inductors of the auxiliary degaussing winding.
The main winding and the auxiliary degaussing winding are arranged in the same shell, and the shell can be made of metal (with an opening at the inner layer) or nonmetal.
During operation, supplementary demagnetization winding offsets the excitation of a power frequency current to the sensor magnetic core to utilize winding impedance frequency characteristic to reduce the influence to the high frequency current transmission, thereby improve discharge current signal transmission SNR by a wide margin, it is specific: when the high-frequency current sensor is used onceSide flowing industrial frequency current ipWhen the high-frequency current sensor is used, a current with a corresponding magnitude is induced on an auxiliary demagnetizing winding of the high-frequency current sensor, and the sum sigma i of the currentssAnd a power frequency current i of the primary sidepApproximately equal to each other, and the excitation of primary side power frequency current is counteracted to the maximum extent. The auxiliary degaussing winding has certain influence on a high-frequency current signal, mainly aims to induce and shunt the high-frequency current by the auxiliary degaussing winding, particularly reduces the high-frequency impedance of the auxiliary degaussing winding due to parasitic capacitance at high frequency, can be connected with an inductor or a magnetic ring (magnetic bead) at the output of the auxiliary degaussing winding in order to reduce the influence on the high-frequency signal as much as possible, improves the high-frequency impedance, and can reduce the influence of the parasitic capacitance to the maximum extent by adopting a plurality of short circuit rings for degaussing.
Based on the sensor with the structure, the invention also discloses a discharge current detection method, which specifically comprises the following steps:
when the primary side of the high-frequency current sensor flows the power frequency current ipWhen the auxiliary demagnetization winding induces currents with corresponding magnitude, the sum sigma i of the currentss≈ipTo offset the primary side power frequency current ipExcitation of (3);
through the main winding NTAnd the detection circuit is connected with an external signal processing circuit to realize discharge current detection.
The high-frequency current sensor adopting the structure has the characteristic of effectively transmitting the high-frequency small current component under the background of power frequency or low-frequency large current. Now, the practical test is carried out on the high-frequency current sensor for demagnetizing the auxiliary winding with the structure, and the specific structural parameters are as follows: the size of the magnetic core is 120/85/20(mm), the sampling winding has 16 turns (load 50 ohm noninductive resistance), and 40 single turns (string magnetic beads) are short-circuited. The degaussing effect of the actual test is shown in table 1, and the high frequency transmission characteristic is shown in table 2. As can be seen from tables 1 and 2, the high-frequency current sensor for demagnetizing the auxiliary winding having the above-described structure has a characteristic of effectively transmitting a high-frequency small current component in a background of a large current at a power frequency or a low frequency.
TABLE 1 Primary side Power frequency Current demagnetization Effect
TABLE 2 Voltage-Current Transmission relationship at high frequencies
Claims (7)
1. A high-frequency current sensor adopting auxiliary winding degaussing is characterized in that: comprises a magnetic core and a main winding NTAnd an auxiliary degaussing winding, the main winding NTThe auxiliary degaussing winding is wound on the magnetic core;
the main winding NTThe discharge current is obtained by connecting the discharge current with an external signal processing circuit;
the auxiliary degaussing winding is composed of N turnsSThe coil may be any one of a coil formed of a single-turn coil, a coil formed of a plurality of coils having the same number of turns, a coil formed of a plurality of coils having different numbers of turns, and a coil formed of a plurality of short-circuit rings.
2. A high frequency current sensor using auxiliary winding degaussing according to claim 1, wherein: the main winding NTAnd the discharge current is obtained by connecting the non-inductive resistor with an external signal processing circuit.
3. A high frequency current sensor using auxiliary winding degaussing according to claim 1, wherein: each output of the auxiliary degaussing winding is short-circuited.
4. A high frequency current sensor using auxiliary winding degaussing according to claim 1, wherein: and each output of the auxiliary degaussing winding is externally connected with an inductor.
5. A high frequency current sensor using auxiliary winding degaussing according to claim 1, wherein: and each output of the auxiliary degaussing winding is in short circuit and connected with the magnetic ring in series.
6. A high frequency current sensor using auxiliary winding degaussing according to claim 1, wherein: the main winding NTAnd an auxiliary degaussing winding wound on the frame and provided with a main winding NTAnd a distance is kept between the framework of the auxiliary degaussing winding and the magnetic core.
7. A discharge current detecting method of a high frequency current sensor using demagnetization of an auxiliary winding according to any one of claims 1 to 6, characterized in that: the method specifically comprises the following steps:
when the primary side of the high-frequency current sensor flows the power frequency current ipWhen the auxiliary demagnetization winding induces currents with corresponding magnitude, the sum sigma i of the currentss≈ipTo offset the primary side power frequency current ipExcitation of (3);
through the main winding NTAnd the detection circuit is connected with an external signal processing circuit to realize discharge current detection.
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| CN202110769781.0A CN113552401A (en) | 2021-07-07 | 2021-07-07 | High-frequency current sensor adopting auxiliary winding degaussing and discharge current detection method |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030201873A1 (en) * | 2002-04-29 | 2003-10-30 | Ambient Corporation | High current inductive coupler and current transformer for power lines |
| CN106526287A (en) * | 2016-11-25 | 2017-03-22 | 太原理工大学 | Zero-flux micro-current sensor used for leakage current detection |
| CN111190039A (en) * | 2018-11-14 | 2020-05-22 | 台达电子工业股份有限公司 | Current detection circuit of power converter |
| CN111880123A (en) * | 2020-07-21 | 2020-11-03 | 华北电力大学 | Method for detecting frequency response signal of transformer winding resisting power frequency magnetic saturation |
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2021
- 2021-07-07 CN CN202110769781.0A patent/CN113552401A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030201873A1 (en) * | 2002-04-29 | 2003-10-30 | Ambient Corporation | High current inductive coupler and current transformer for power lines |
| CN106526287A (en) * | 2016-11-25 | 2017-03-22 | 太原理工大学 | Zero-flux micro-current sensor used for leakage current detection |
| CN111190039A (en) * | 2018-11-14 | 2020-05-22 | 台达电子工业股份有限公司 | Current detection circuit of power converter |
| CN111880123A (en) * | 2020-07-21 | 2020-11-03 | 华北电力大学 | Method for detecting frequency response signal of transformer winding resisting power frequency magnetic saturation |
Non-Patent Citations (1)
| Title |
|---|
| 王军 等: "特高压电流互感器励磁特性测试研究", 山东电力技术, no. 05, 25 May 2017 (2017-05-25) * |
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