A Rogowski coil calibration device and method for lightning current measurement

Abstract

The present invention discloses a Rogowski coil calibration device and method for lightning current measurement, which belongs to the field of electrical measurement technology. The calibration device includes a main control computer, a signal generator, a kilometer amplifier, a high-frequency current booster, an AC shunt, a first data acquisition device, a second data acquisition device, etc.; by completing the traceability of the standard AC shunt; obtaining the standard value and the measured value within the nominal working frequency range of the calibrated Rogowski coil; calculating the calibration value of the proportional coefficient and the bandwidth according to the measurement data, and realizing the calibration of the Rogowski coil for lightning current measurement. The present invention is applicable to the aviation field, and based on the high-frequency current booster, the standard AC shunt and the frequency domain finite element technology, it solves the calibration problem of the proportional coefficient and the bandwidth of the Rogowski coil with hundreds of kiloamperes, and traces back to the superior standard to ensure that the aircraft meets the requirements of the lightning protection safety index.

Description

Technical Field

[0001] The invention relates to a Rogowski coil calibration device and method for lightning current measurement, belonging to the technical field of electrical measurement. Background Art

[0002] In the development stage of modern aircraft, the impact of lightning must be fully considered to ensure the safety of the aircraft and its onboard equipment. After being assembled into a complete aircraft, the local structures or components of the aircraft that meet the lightning protection safety requirements cannot guarantee that the complete aircraft also meets the requirements of the lightning protection safety index due to the mutual influence of load effects, electromagnetic coupling, etc. Therefore, general aircraft will undergo a lightning attachment area division test of a scaled model, a component engineering test, and a component identification test before conducting a lightning protection characteristic test of the complete aircraft. Only after the complete aircraft passes the lightning protection test and meets the specified requirements can it be considered that the aircraft meets the requirements of the lightning protection safety index.

[0003] The whole aircraft lightning test is used to obtain the actual transient level of the aircraft system wiring. During the test, it is necessary to simulate the lightning environment encountered by the aircraft. Generally, the simulated lightning current pulse defined in SAE ARP 5412B is injected into the aircraft. In order to avoid damage to the aircraft or equipment, the amplitude needs to be scaled down during the test; then, the transient level of the induced voltage and current in the specified interconnecting wires and cables is measured and recorded through instruments placed inside or near the aircraft; then the measured data is linearly extrapolated to obtain the actual transient level of the aircraft.

[0004] The whole lightning test system is generally composed of a transient impulse lightning current generating device, a lightning current monitoring device and an induced transient measuring device. The lightning current monitoring device is mainly composed of a Rogowski coil. Due to the large measuring current (hundreds of kiloamperes) and wide bandwidth range (several megahertz), it is very difficult to calibrate its characteristics. In the existing method, a multi-function calibration source and a digital multimeter are mainly used to calibrate the proportional coefficient during the calibration of the Rogowski coil. Due to the limited output current of the multi-function source, the voltage measured by the Rogowski coil is extremely small and is easily affected by noise, which is particularly obvious when calibrating a Rogowski coil with a small proportional coefficient. When calibrating the bandwidth, the rise time is measured to invert the bandwidth, and the upper and lower cut-off frequencies cannot be obtained. Summary of the invention

[0005] In view of the shortcomings of the existing calibration methods for the calibration process of Rogowski coils of hundreds of kiloamperes, the main purpose of the present invention is to propose a Rogowski coil calibration device and method for lightning current measurement, which is based on high-frequency current booster, standard AC shunt and frequency domain finite element technology to solve the calibration problem of proportional coefficient and bandwidth of Rogowski coils of hundreds of kiloamperes, and trace back to the superior standard.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The invention discloses a Rogowski coil calibration device for lightning current measurement, which mainly comprises a main control computer, a signal generator, a power amplifier, a high-frequency current booster, an AC shunt, a first data acquisition device and a second data acquisition device.

[0008] The main control computer controls the output of the signal generator and the data acquisition device collects the signal;

[0009] The signal generator outputs an AC signal with a frequency range exceeding 1MHz and a sine wave signal amplitude reaching 10V;

[0010] The power amplifier amplifies the small AC signal from the signal generator to generate a large enough current to drive the high-frequency current booster. Its frequency band covers the frequency range of the signal generator. The input signal amplitude is not less than 10V.

[0011] High-frequency current booster, the magnetic core is made of carbon nanocrystalline material, with low high-frequency loss, not easy to reach magnetic saturation state, bandwidth covers the frequency range of the signal generator, and generates a high-frequency AC current of not less than 100A in the secondary coil;

[0012] The AC shunt, as a calibration standard, is responsible for measuring the standard value of the output current and converting it into voltage;

[0013] A first data acquisition device integrates the output signal of the calibrated Rogowski coil to obtain an output voltage value;

[0014] The second data acquisition device collects the voltage value output by the AC shunt, transmits it to the main control computer, and converts it into a current standard value.

[0015] The present invention discloses a Rogowski coil calibration method for lightning current measurement, comprising the following steps:

[0016] Step 1: Complete the traceability of the standard AC shunt

[0017] Based on the frequency domain finite element technology, the physical model of the AC shunt (including materials and dimensions) is established, and the transfer function H(f) of the AC shunt within 1MHz is calculated;

[0018] Step 2: Obtain the standard value and measured value within the nominal operating frequency range of the calibrated Rogowski coil

[0019] Within the operating frequency range of the calibrated Rogowski coil (f L , f H), the frequency sweep output is performed in steps of 1%, and the voltage U2 measured by the second data acquisition device is calculated with H(f) according to formula (1) to obtain the output current standard value I0 at each frequency point;

[0020] U2=I0·H(f) (1)

[0021] Step 3: Calculate the proportionality factor and bandwidth

[0022] The voltage U1 at each frequency point measured by the first data acquisition device. According to formula (2), the ratio of U1 to I0 is calculated at each frequency point to obtain the proportional coefficient calibration value R of the calibrated Rogowski coil; 10 points are selected at the center frequency of the working frequency range to calculate the average value R of the proportional coefficient m , and find R upward and downward respectively L and R H With R m The difference is not less than 3dB, R L and R H The corresponding frequency f L and f H , as the upper and lower limit calibration values ​​of the working frequency of the Rogowski coil being calibrated. If no frequency matching R is found in the entire frequency band, m If the difference is not less than 3dB, it is determined that the frequency band range of the calibrated Rogowski coil is consistent with the nominal range, that is, the calibration of the Rogowski coil for lightning current measurement is achieved.

[0023] R=U1 / I0 (2)

[0024] Beneficial effects:

[0025] 1. The present invention discloses a Rogowski coil calibration device and method for lightning current measurement, which realizes the calibration of the proportional coefficient and bandwidth parameters of the Rogowski coil (peak current reaches 100 kA) for lightning current measurement based on a high-frequency current booster, an AC shunt, a data acquisition device and a frequency domain finite element technology.

[0026] 2. The present invention discloses a Rogowski coil calibration device and method for lightning current measurement, which uses a frequency sweeping method for measurement, and can obtain the upper and lower cut-off frequencies when calibrating the bandwidth parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention discloses a schematic diagram of the composition of a Rogowski coil calibration device for lightning current measurement. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. The technical problems solved by the technical solution of the present invention and the beneficial effects are also described. It should be noted that the described embodiments are only intended to facilitate the understanding of the present invention and do not have any limiting effect on it.

[0029] The present embodiment discloses a Rogowski coil calibration device for lightning current measurement, comprising a main control computer, a signal generator, a power amplifier, a high-frequency current booster, an AC shunt, a first data acquisition device and a second data acquisition device.

[0030] The specific composition of the calibration device is as follows: the signal generator is Keysight's 33250A; the power amplifier is Antai's ATA-4014 high-voltage power amplifier, with an output power of 452W and a maximum output current of 4A; the high-frequency current booster is designed by itself, and the magnetic core is made of carbon nanocrystalline material, which can provide sufficient current gain within a bandwidth of 1MHz to increase the current to 100A; the AC shunt adopts a 10mΩ improved squirrel cage shunt, and the transmission characteristics within a bandwidth of 1MHz meet the requirements; the first data acquisition device and the second data acquisition device are composed of a 16-bit data acquisition card; the calibrated Rogowski coil has a nominal bandwidth of 1MHz, a lower cut-off frequency of 5Hz, an upper cut-off frequency of 1MHz, and a nominal proportional coefficient of 0.001V / A.

[0031] The present embodiment discloses a Rogowski coil calibration method for lightning current measurement, comprising the following steps:

[0032] Step 1: Complete the traceability of the standard AC shunt

[0033] Based on the frequency domain finite element technology, by establishing the physical model of the AC shunt (including materials and dimensions), the transfer function H(f) of the AC shunt within 1 MHz is calculated. The present invention only needs to consider the amplitude accuracy of the proportional coefficient, and does not consider the phase change. Therefore, only the amplitude of H(f) is listed in the calculation process, as shown in Table 1;

[0034] Table 1 The transfer function amplitude values ​​of AC shunt at various frequency points

[0035]

[0036] Step 2: Obtain the standard value and measured value within the nominal operating frequency range of the calibrated Rogowski coil

[0037] Within the working frequency range of the calibrated Rogowski coil of 0.005kHz to 1MHz, the frequency sweep output is performed in a step of 1%. The voltage U2 measured by the second data acquisition device is calculated with H(f) according to formula (1) to obtain the output current standard value I0 at each frequency point;

[0038] U2=I0·H(f) (1)

[0039] Table 2 Output voltage of AC shunt at different frequencies

[0040]

[0041] Table 3 Standard current values ​​through Rogowski coil at different frequencies

[0042]

[0043] Step 3: Calculate the proportionality factor and bandwidth

[0044] The voltage U1 at each frequency point measured by the first data acquisition device. According to formula (2), the ratio of U1 to I0 is calculated at each frequency point to obtain the proportional coefficient calibration value R of the calibrated Rogowski coil; 10 points are selected at the center frequency of the working frequency range to calculate the average value R of the proportional coefficient m , and find R upward and downward respectively L and R H With R m The difference is not less than 3dB, R L and R H The corresponding frequency f L and f H , as the upper and lower limit calibration values ​​of the working frequency of the Rogowski coil being calibrated. If no frequency matching R is found in the entire frequency band, m If the difference is not less than 3dB, it is determined that the frequency band range of the calibrated Rogowski coil is consistent with the nominal range.

[0045] R=U1 / I0 (2)

[0046] Table 4 Output voltage of Rogowski coil at different frequencies

[0047]

[0048]

[0049] Table 5 Proportional coefficients of Rogowski coils at different frequencies

[0050]

[0051]

[0052] According to the table above, the proportional coefficient in the frequency range of 0.005kHz to 1MHz is proportional to the average value R m The difference does not exceed 3dB, which shows that the bandwidth meets the nominal range requirements.

[0053] Through the above embodiments, the effectiveness of the calibration device and calibration method of the present invention is verified, and the calibration of the proportionality coefficient and bandwidth of the Rogowski coil at the hundreds of kiloamperes level is achieved.

[0054] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A Rogowski coil calibration method for lightning current measurement, characterized in that: The following steps are included: Step 1: Complete the traceability of the standard AC shunt; Based on the frequency domain finite element technology, the physical model of the AC shunt is established and the transfer function H(f) of the AC shunt within 1MHz is calculated. Step 2: Obtain standard values ​​and measured values ​​within the nominal operating frequency range of the calibrated Rogowski coil; Within the operating frequency range of the calibrated Rogowski coil (f L , f H ), the frequency sweep output is performed according to the preset step, and the voltage U2 measured by the second data acquisition device is calculated with H(f) according to formula (1) to obtain the output current standard value I0 at each frequency point; U2=I0·H(f) (1) Step 3, calculate the proportionality coefficient and bandwidth; The voltage U1 at each frequency point measured by the first data acquisition device; according to formula (2), the ratio of U1 to I0 is calculated at each frequency point to obtain the proportional coefficient calibration value R of the calibrated Rogowski coil; a preset number of points are selected at the center frequency of the working frequency range to calculate the average value R of the proportional coefficient m , and find R upward and downward respectively L and R H With R m The difference is not less than 3dB, R L and R H The corresponding frequency f L and f H , as the upper and lower limit calibration values ​​of the working frequency of the Rogowski coil being calibrated. If no frequency matching R is found in the entire frequency band, m If the difference is not less than 3dB, it is determined that the frequency band range of the calibrated Rogowski coil is consistent with the nominal range, that is, the calibration of the Rogowski coil for lightning current measurement is achieved. R=U1 / I0 (2) The device for implementing the Rogowski coil calibration method for lightning current measurement mainly includes a main control computer, a signal generator, a power amplifier, a high-frequency current booster, an AC shunt, a first data acquisition device and a second data acquisition device; The main control computer controls the output of the signal generator and the data acquisition device collects the signal; The signal generator outputs an AC signal with a frequency range exceeding 1MHz and a sine wave signal amplitude reaching 10V; The power amplifier amplifies the small AC signal from the signal generator to generate a large enough current to drive the high-frequency current booster. Its frequency band covers the frequency range of the signal generator. The input signal amplitude is not less than 10V. High-frequency current booster, the magnetic core is made of carbon nanocrystalline material, the bandwidth covers the frequency range of the signal generator, and generates a high-frequency AC current of not less than 100A in the secondary coil; The AC shunt, as a calibration standard, is responsible for measuring the standard value of the output current and converting it into voltage; A first data acquisition device integrates the output signal of the calibrated Rogowski coil to obtain an output voltage value; The second data acquisition device collects the voltage value output by the AC shunt, transmits it to the main control computer, and converts it into a current standard value.

2. A Rogowski coil calibration method for lightning current measurement as claimed in claim 1, characterized in that: The preset step refers to performing frequency sweep output in steps of 1%.

3. A Rogowski coil calibration method for lightning current measurement as claimed in claim 1, characterized in that: Select 10 points at the center frequency of the operating frequency range to calculate the average value of the proportional coefficient R m .

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