CN102012448B - Rogowski current sensor - Google Patents

Abstract

The present invention relates to a Rogowski current sensor, comprising: an external shielding structure; a ring-shaped magnetic medium frame; a first coil and a second coil independently wound on the ring-shaped magnetic medium frame, the The first coil has more winding turns than the second coil; the first coil and the second coil are respectively connected in parallel with a first integral resistor and a second integral resistor with corresponding resistance values; the first integral resistor and the second integrating resistor respectively have corresponding measurement signal output terminals; the second integrating resistor is also connected in parallel with a transient voltage suppression diode. In the embodiment of the present invention, in the coil structure, coils with different winding turns are wound on the circular magnetic medium skeleton, so that the sensor can realize the measurement of the current signal of a wider amplitude range, and the TVS is connected in parallel with the second integrating resistor In this way, the outlet voltage at both ends of the second integrating resistor is limited when the coil passes a large current, which improves the reliability of the sensor.

Description

Rogowski current sensor

technical field

The invention relates to high voltage measurement technology, in particular to a Rogowski current sensor.

Background technique

The Rogowski coil is a hollow or toroidal coil with a magnetic core. Its working mechanism is the principle of electromagnetic induction. It can be directly placed on the conductor under test to measure the AC current passing through the conductor. The measuring range of the coil is from a few milliamps to hundreds of kiloamperes, which can meet different measurement requirements. The Rogowski coil has the advantages of wide applicable frequency, wide measurement amplitude, good linearity, easy calibration, and no electrical connection with the primary circuit. Therefore, it has extremely broad application prospects in many fields, such as power quality monitoring, rectifier monitoring, partial discharge monitoring, etc.

In the prior art, measuring sensors based on Rogowski coils that independently measure large currents and small currents are relatively mature. However, these current sensors can only measure current signals in a single amplitude range well. If the current amplitude varies greatly, it is difficult to make a complete measurement throughout the experiment.

Contents of the invention

The object of the present invention is to propose a Rogowski current sensor capable of measuring current signals with a wide range of amplitudes.

To achieve the above object, the invention provides a Rogowski current sensor, comprising:

External shielding structure;

Circular magnetic medium skeleton;

A first coil and a second coil independently wound on the circular magnetic medium skeleton, the first coil has more winding turns than the second coil;

The first coil and the second coil are respectively connected in parallel with a first integral resistor and a second integral resistor with corresponding resistance values;

The first integrating resistor and the second integrating resistor respectively have corresponding measurement signal output terminals;

The second integral resistor is also connected in parallel with a transient voltage suppression diode.

In this embodiment, in the coil structure, coils with different winding turns are wound on the circular magnetic medium skeleton, so that the sensor can realize the measurement of the current signal of a wider amplitude range, and through the second integrating resistor The way of connecting TVS in parallel limits the outlet voltage at both ends of the second integrating resistor when the coil passes a large current, so as not to threaten the safety of the subsequent measuring instrument due to the induction of high voltage.

Preferably, the number of turns of the first coil: 100-1000 turns, the integral resistance: 0.1-10Ω, the current range is about: 100A-tens of kA; the number of turns of the second coil: 1-100 Turn, integral resistance: 10~1000Ω, current range: 1mA~tens of A. The number of winding turns through the larger current coil is more, and the corresponding integral resistance is smaller; the number of winding turns through the smaller current coil is less, and the corresponding integral resistance is larger.

Preferably, the resistance value of the first integral resistor corresponding to the first coil is 0.1-10Ω, and the resistance value of the second integral resistor corresponding to the second coil is 10-1000Ω.

Preferably, the annular magnetic medium skeleton is a solid annular structure made of nickel-zinc ferrite material. Compared with ordinary magnetic cores such as manganese-zinc ferrite materials, due to the relatively low initial permeability of nickel-zinc ferrite materials, they can be used in the range of 10kHz to 300MHz (the frequency range of manganese-zinc ferrite is about: 1kHz～10MHz), thus expanding the use frequency band of the sensor of the present invention.

Further, the external shielding structure is a metal shielding box with a ring structure, and the circular magnetic core wound with the first coil and the second coil, the first integrating resistor, the second Integrating resistors and transient voltage suppressing diodes, the outer periphery of the metal shielding box is provided with a slit structure. The metal shielding box accommodates the main working parts of the sensor, which can prevent external electromagnetic interference, and the narrow slot structure can provide a coupling path for the magnetic field of the primary side current.

A shielding box made of a metal material can realize the function of preventing electromagnetic interference, for example, a metal with a low magnetic permeability such as aluminum or copper is used.

Further, the distance between the adjacent edges of the first coil and the second coil is 1/4 times the circumference of the circular magnetic medium skeleton. Both the first coil and the second coil are wound separately and cannot be overlapped, and a space distance of at least 1/4 of the circumference is required to be maintained.

Preferably, the distance is 1/4 times the circumference of the circular magnetic medium skeleton.

Preferably, the first integrating resistor and the second integrating resistor are non-inductive resistors. Since measuring the rapidly changing current needs to reduce the inductance of the integrating resistor, the stray inductance of the ordinary resistor is large, and a large oscillation will occur during integration, which cannot restore the original current signal well, and the measurement frequency band and accuracy of the sensor will be affected. Therefore, The use of non-inductive resistors can better restore the original current signal and ensure the measurement frequency band and accuracy of the sensor.

Based on the above technical solution, the embodiment of the present invention winds coils with different numbers of winding turns on the circular magnetic medium skeleton in the coil structure, so that the sensor can realize the measurement of the current signal with a wider amplitude range, and solves the problem of ordinary current The sensor can only measure the problem of limited application range caused by the current signal of a single amplitude range, and by connecting the TVS in parallel with the second integrating resistor, the outlet voltage at both ends of the second integrating resistor is limited when the coil passes a large current, so as to avoid The safety of the post-stage measuring instruments is threatened by the induction of high voltage, which improves the reliability of the sensor.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

FIG. 1 is a structural schematic diagram of an embodiment of the Rogowski current sensor of the present invention.

Fig. 2 is a schematic diagram of a square wave response curve for testing a relatively small current of 28mA using the Rogowski current sensor embodiment of the present invention.

Fig. 3 is a schematic diagram of a pulse response curve of a small current of 28mA tested by using the Rogowski current sensor embodiment of the present invention.

Fig. 4 is a schematic diagram of an impulse response curve for testing a relatively large current (5kA, 8/20μs standard current wave) using the Rogowski current sensor embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

As shown in FIG. 1 , it is a structural schematic diagram of an embodiment of the Rogowski current sensor of the present invention. In this embodiment, the Rogowski current sensor includes a circular magnetic medium skeleton 1, on which a first coil 2-1 and a second coil 2-2 are wound independently, respectively, Wherein the first coil 2-1 has more winding turns than the second coil 2-2, the first integrating resistor 5-1 is connected in parallel at both ends of the enameled wire forming the first coil 2-1, and the second integrating resistor 5-1 is formed in parallel The two ends of the enameled wire of the coil 2-2 are connected in parallel with a second integrating resistor 5-2, and the resistance values of the first integrating resistor 5-1 and the second integrating resistor 5-2 are respectively according to the first coil 2-1 and the second coil 2 -2 set. The first integrating resistor 5-1 has a corresponding measurement signal output terminal 6-1, which can be connected to one input channel of the oscilloscope, and the second integrating resistor 5-2 has a corresponding measurement signal output terminal 6-2, which can be connected to another input channel of the oscilloscope. connected to an input channel.

A transient voltage suppressor diode (Transient Voltage Suppressor, TVS for short) 4 may also be connected in parallel at both ends of the second integrating resistor. In order to avoid external electromagnetic interference, an external shielding structure 3 can be provided outside the above components.

In this embodiment, in the coil structure, coils with different winding turns are wound on the circular magnetic medium skeleton, so that the sensor can measure the current signal of a wider amplitude range, and use two detection signals to output Connect the two input channels of the oscilloscope to display signal waveforms of different magnitudes of current.

In the structure of the Rogowski current sensor in the prior art, only one coil is wound on the skeleton, and the number of winding turns and the resistance value of the integrating resistor are different according to the sensitivity of the detected current. In this embodiment, two coils with different winding turns are independently wound on the skeleton, and the amplitude range of the detected current covers two Rogowski coils with different winding turns. The amplitude range of the current sensor is reduced, and the manufacturing cost is also reduced due to the shared circular magnetic dielectric bobbin and external shielding structure.

In order to make the Rogowski current sensor of the present invention have a wider amplitude range, the number of winding turns of the first coil is 100 to 1000 turns, which is suitable for measuring large currents in the range of 100A to tens of kA; the second coil The number of winding turns is 1 to 100 turns, suitable for measuring small currents ranging from 1mA to dozens of A. Since the number of turns of the first coil is large and the variable ratio is large, the sensitivity is small; while the number of turns of the second coil is small and the variable ratio is small, so the sensitivity is relatively high. For the first coil for measuring large current, the resistance value of the corresponding first integral resistor is 0.1-10Ω; for the second coil for measuring small current, the resistance value of the corresponding second integral resistor is 10-1000Ω.

Connecting TVS in parallel at both ends of the second integrating resistor can limit the outlet voltage at both ends of the second integrating resistor when the coil passes a large current, so as not to threaten the safety of the subsequent measuring instrument due to high voltage induced.

The cross-section of the ring-shaped magnetic medium skeleton can be square, which is convenient for manufacturing and winding coils. Its material can be selected from plexiglass or ordinary magnetic core, preferably a solid ring structure made of nickel-zinc ferrite material. Because the nickel-zinc ferrite material has low magnetic permeability and high resistance, it is suitable for occasions with high frequency.

The outer shielding structure can be a metal shielding box with a ring structure, which contains the circular magnetic core wound with the first coil and the second coil, the first integrating resistor, the second integrating resistor and the TVS, and the metal shielding box The outer periphery of the shielding box is provided with a slit structure. The metal shielding box accommodates the main working parts of the sensor and can prevent external electromagnetic interference. The slit structure generates a magnetic field on a plane perpendicular to the current direction when the primary current passes through the central axis of the sensor. The magnetic field passes through the slit structure and induces a voltage on the coil of the sensor. The slit structure is the primary current Provides a coupling path. The metal shielding box can use commonly used metals with high conductivity, such as aluminum and copper.

The first coil and the second coil are wound separately and cannot be overlapped, and a certain space distance is required to be maintained. The distance between the adjacent edges of the first coil and the second coil can be selected as 1/4 of the circumference. Preferably, the distance is 1/4 times the circumference of the circular magnetic medium skeleton. When the spacing of 1/4 of the circumference is adopted, the frequency band of the current signal induced by the second coil is wider and the performance is better, but if other spacings are selected, both the frequency band and the performance are adversely affected.

Preferably, the first integral resistor and the second integral resistor can be non-inductive resistors. Since measuring the rapidly changing current needs to reduce the inductance of the integrating resistor, the stray inductance of the ordinary resistor is large, and a large oscillation will occur during integration, which cannot restore the original current signal well, and the measurement frequency band and accuracy of the sensor will be affected. Therefore, The use of non-inductive resistors can better restore the original current signal and ensure the measurement frequency band and accuracy of the sensor. Ordinary resistors can also be used as integral resistors if low-frequency currents are mainly tested.

The two measurement signal output ends of the embodiment of the Rogowski current sensor of the present invention can adopt engineering standard connectors, such as Q9 connectors, etc., which can be well matched with the input channel of the oscilloscope through the cable. Adjust the trigger level to a suitable position before testing. The measurement signal output terminal 6-1 in Fig. 1 is the output terminal of relatively large current, and its sensitivity is small (for example 5V/A), and the measurement signal output terminal 6-2 is the output terminal of relatively small current, and its sensitivity is relatively large (eg 0.005V/A). Pass the signal wire to be tested through the center of the coil, when a small current passes through, the test signal output terminal 6-2 outputs a small current signal, and the corresponding waveform is displayed on the oscilloscope; at this time, the test signal output terminal 6-1 is due to sensitivity Low, the output is almost zero, and the oscilloscope cannot measure, so there is no waveform or the waveform is not obvious on the display. When a large current passes through, the test signal output terminal 6-1 outputs a larger current signal, which is suitable for oscilloscope measurement, so the corresponding waveform is displayed on the oscilloscope, and the test signal output terminal 6-2 has higher sensitivity, and the output pulse The signal will be very large, which will easily cause damage to the measuring instrument. Therefore, the output voltage amplitude is limited to the regulated value of the TVS tube by connecting TVS in parallel to avoid damage to the measuring instrument.

FIG. 2 and FIG. 3 are two specific test examples of the embodiment of the Rogowski current sensor of the present invention. Wherein, Fig. 2 is a schematic diagram of a square wave response curve for testing a small current (28mA), wherein curve 1 represents a shunt, and curve 2 represents a small current coil; Fig. 3 is a schematic diagram of a pulse response curve for testing a small current (28mA), wherein Curve 1 represents a shunt, curve 2 represents a small current coil; Figure 4 is a schematic diagram of the impulse response curve for testing a larger current (5kA, 8/20μs standard current wave), where curve 1 represents a large current coil, and curve 2 represents a shunt.

Figure 2 shows that the response time of the rising edge and falling edge of the square wave response curve with a small current is shorter than the shunt response time on average, indicating that the high-frequency performance of the coil is better; at the same time, the response flat-top drop of the square wave response curve is very small, indicating that Its low-frequency characteristics are also good; in addition, there is no oscillation and overshoot near the rising and falling edges. Figure 3 shows that the response time of the rising edge and falling edge of the small current pulse response curve is shorter than the shunt response time on average, indicating that the high frequency performance of the coil is better. At the same time, there is no overshoot and oscillation at the pulse tail.

与理论灵敏度很接近，说明较大电流的测试8/20μs标准电流波未发生截止，正负峰值基本重合，无相差，波形响应好。In Fig. 4, the number of turns of the high-current coil is 200 turns, and the integral resistance is 1Ω, so the theoretical sensitivity is H=1/200=0.005. A standard shunt is used to calibrate the sensitivity of the high-current coil, and the resistance value of the shunt is 0.001824Ω. At this time, the output voltage of the shunt is 9.9V, and the output voltage of the high-current coil is 27.1V, so the actual sensitivity is

It is very close to the theoretical sensitivity, indicating that the 8/20μs standard current wave of the larger current test has not been cut off, the positive and negative peaks basically coincide, there is no phase difference, and the waveform response is good.

Those of ordinary skill in the art can understand that all or part of the steps for realizing the above-mentioned method embodiments can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the It includes the steps of the above method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other various media that can store program codes.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: the present invention can still be Modifications to the specific implementation of the invention or equivalent replacement of some technical features; without departing from the spirit of the technical solution of the present invention, should be included in the scope of the technical solution claimed in the present invention.

Claims (8)

1. A Rogowski current sensor, comprising: External shielding structure; Circular magnetic medium skeleton; A first coil and a second coil independently wound on the circular magnetic medium skeleton, the first coil has more winding turns than the second coil; The first coil and the second coil are respectively connected in parallel with a first integral resistor and a second integral resistor with corresponding resistance values; The first integrating resistor and the second integrating resistor respectively have corresponding measurement signal output terminals; The second integral resistor is also connected in parallel with a transient voltage suppression diode. 2. The Rogowski current sensor according to claim 1, wherein the number of turns of the first coil is 100-1000 turns; the number of turns of the second coil is 1-100 turns. 3. The Rogowski current sensor according to claim 2, wherein the resistance value of the first integrating resistor corresponding to the first coil is 0.1～10Ω, and the second integrating resistor corresponding to the second coil The resistance value is 10~1000Ω. 4. The Rogowski current sensor according to claim 1, wherein the annular magnetic medium skeleton is a solid annular structure made of nickel-zinc ferrite material. 5. The Rogowski current sensor according to claim 1, wherein the outer shielding structure is a metal shielding box of annular structure, and the metal shielding box wound with the first coil and the second coil is accommodated in the metal shielding box. The ring-shaped magnetic medium skeleton, the first integral resistor, the second integral resistor and the transient voltage suppression diode are provided with a slit structure on the outer periphery of the metal shielding box. 6. The Rogowski current sensor according to claim 1, wherein the spacing between the adjacent edges of the first coil and the second coil is at least 1/4 times the circumference of the circular magnetic medium skeleton long. 7. The Rogowski current sensor according to claim 6, wherein the distance is 1/4 times the circumference of the circular magnetic medium skeleton. 8. The Rogowski current sensor according to claim 1 or 3, wherein the first integrating resistor and the second integrating resistor are non-inductive resistors.

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