Optical fiber voltage and current transformer verification system

Abstract

The invention relates to the technical field of optical fiber voltage and current transformers, and discloses an optical fiber voltage and current transformer verification system. According to the optical fiber voltage and current transformer verification system, an input signal is denoised by using a low-pass filter, interference of high-frequency noise on measurement is eliminated, after the signal is acquired, the system accurately calculates an effective value and a phase difference of the signal by means of an amplification and demodulation technology, and the system also uses a Fourier transform technology to extract harmonic components in the signal, so that the detection accuracy of the optical fiber voltage and current transformer is improved. The amplitude and the frequency of the components are analyzed, so that the spectral characteristics of the signals are deeply known, the verification unit compares the processed result with a standard reference value in detail to effectively judge whether the signals meet the verification standard or not, the system design is friendly in the aspect of a user interface, a user can easily adjust parameters, and the verification efficiency is improved. And even the verification process can be quickly restarted, so that more efficient maintenance and data management are ensured, and the error rate in the verification process is reduced by reducing human intervention.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber voltage and current transformers, in particular to an optical fiber voltage and current transformer calibration system. Background Art

[0002] With the rapid development of smart grids and renewable energy, fiber optic voltage and current transformers (FOV-CT) have been widely used as key measurement and monitoring equipment in modern power systems. FOV-CTs use optical fiber technology to achieve non-contact measurement of voltage and current. They have the advantages of anti-electromagnetic interference, small size, light weight and high precision. Their application in complex and high-voltage environments can effectively improve the reliability and safety of power systems.

[0003] In the design and application of fiber-optic voltage and current transformers, it is crucial to ensure the accuracy and stability of their measurements. In order to ensure the performance of the transformer, regular calibration and maintenance become essential links. Traditional calibration usually requires multiple steps to be performed manually, including equipment disassembly, connection, measurement and data recording. Manual operations are easily affected by the operator's experience and skills. These operations are not only time-consuming, but may also cause the equipment to fail to work properly during the calibration process due to human errors, reducing the final calibration accuracy. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a fiber optic voltage and current transformer calibration system, which has the functions of real-time acquisition of voltage and current signals from a fiber optic transformer and digitization thereof, and accurately calculating the effective value and phase difference of the signal through low-pass filtering, amplification and demodulation, and at the same time, extracting harmonic components by Fourier transform and analyzing their amplitude and frequency. The calibration unit compares the processing results with standard reference values ​​to effectively judge the qualification of the calibration. Combining these functions, the system simplifies the operation process, and the user can easily adjust parameters and restart the calibration process through a friendly interface, making maintenance and data management more efficient, avoiding errors caused by human calibration, and improving the calibration accuracy, etc., thereby solving the above-mentioned problems.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solution: a fiber optic voltage and current transformer calibration system, characterized in that it includes a voltage signal acquisition unit, a current signal acquisition unit, a signal processing unit, a calibration unit and a display unit;

[0008] The voltage signal acquisition unit acquires the voltage signal from the optical fiber voltage transformer, converts it into a voltage digital signal, and sends the voltage digital signal to the signal processing unit;

[0009] The current signal acquisition unit acquires the current signal from the optical fiber current transformer, converts it into a current digital signal, and sends the current digital signal to the signal processing unit;

[0010] The signal processing unit calculates the effective values ​​of the voltage digital signal and the current digital signal after low-pass filtering, amplification and demodulation according to the converted voltage digital signal and current digital signal, and calculates the phase difference between the voltage digital signal and the current digital signal;

[0011] The verification unit calculates the measurement error according to the effective value of the processed voltage digital signal and the current digital signal and the phase difference between the voltage digital signal and the current digital signal, determines whether the measurement verification is qualified according to the measurement error, and sends the verification result to the display unit;

[0012] The display unit displays the effective value of voltage and current, phase difference and calibration results, and provides an operation panel for the user to adjust parameters and restart the calibration process.

[0013] Preferably, the voltage digital signal conversion formula is as follows:

[0014]

[0015] In the formula, Dv[n] represents the voltage digital signal sampled at the nth time, V(n*Ts) represents the instantaneous voltage value sampled at time nTs, and V max It represents the maximum value of all voltage signals collected within the sampling period, Ts represents the sampling period, n represents the number of sampling times, Q(*) represents the quantization function, and N represents the number of quantization bits.

[0016] Preferably, the current digital signal conversion formula is as follows:

[0017]

[0018] In the formula, DI[n] represents the current digital signal sampled at the nth time, I(n*Ts) represents the instantaneous current value sampled at time nTs, and I max It represents the maximum value of all current signals collected within the sampling period, Ts represents the sampling period, n represents the number of sampling times, Q(*) represents the quantization function, and N represents the number of quantization bits.

[0019] Preferably, the calculation formula of the low-pass filtering is as follows:

[0020]

[0021] In the formula, Y[n] represents the voltage digital signal and current digital signal after low-pass filtering, D[n] represents the voltage digital signal and current digital signal input for the nth time, M represents the window size of the filter, and k represents the weighting of the filter on the past M samples. Represents a sum operation, which adds the current sample value n to the sum of the previous M-1 sample values, using the reverse index Implementation means starting from D[n], and obtaining M samples of data backwards. It means that the average value of the signal within the window is obtained by dividing the summation result by M.

[0022] Preferably, the formula for amplifying the voltage digital signal and the current digital signal is as follows:

[0023] Z[n]=G*Y[n]

[0024] In the formula, Z[n] represents the amplified voltage digital signal and current digital signal, G represents the amplification factor and is a constant value greater than 1, and Y[n] represents the voltage digital signal and current digital signal output after low-pass filtering.

[0025] Preferably, the formula for demodulating the voltage digital signal and the current digital signal by the signal processing unit is as follows:

[0026] S[n]=Z[n]*cos(2π*f c *k*Ts)+LPF{Z[n]*sin(2π*f c *k*Ts)}

[0027] In the formula, S[n] represents the demodulated voltage digital signal and current digital signal, Z[n] represents the amplified voltage digital signal and current digital signal, and f c represents the carrier frequency, that is, the frequency of the information signal contained in the modulated signal, which is measured by the mutual inductance calibration system. Ts represents the sampling period. LPF{Z[n]*sin(2π*f c *k*Ts)} represents low-pass filtering, which is used to remove high-frequency noise. k is the sample number, which represents the time series. c *k*Ts) represents the cosine component of the carrier signal, which is used for signal phase modulation, sin(2π*f c *k*Ts) represents the sinusoidal component of the carrier signal, which is used for signal amplitude modulation.

[0028] Preferably, the calculation formula of the effective value of the voltage digital signal is as follows:

[0029]

[0030] In the formula, V rms Represents the effective value of the voltage digital signal, V[e] represents the voltage sample value measured for the eth time, the processed voltage digital signal, P represents the total number of samples, the number of samples used to calculate the effective value, e represents the number of measurements, It means to sum the square values ​​of all voltage digital signal samples, divide the sum by P to get the average square value, and then take the square root to convert the calculated value back to the unit of voltage and get the actual effective value of the voltage signal;

[0031] The formula for calculating the effective value of the current digital signal is as follows:

[0032]

[0033] In the formula, I rms Represents the effective value of the current digital signal, I[e] represents the current sample value measured for the eth time, the processed current digital signal, P represents the total number of samples, the number of samples used to calculate the effective value, e represents the number of measurements, It means summing the square values ​​of all current digital signal samples, dividing the sum by P to obtain the average square value, and taking the square root is to convert the calculated value back to the unit of current and obtain the actual effective value of the current signal.

[0034] Preferably, the calculation formula for the phase difference between the voltage digital signal and the current digital signal is as follows:

[0035]

[0036] In the formula, It represents the phase difference between the voltage digital signal and the current digital signal, expressed in radians. Arctan represents the inverse tangent function. It means calculating the ratio of the reactive components of voltage and current, and the result is the phase difference of the signal.

[0037] Preferably, the formula for calculating the measurement error by the verification unit is as follows:

[0038]

[0039] In the formula, Ep represents the measurement error, It represents the phase difference between the voltage digital signal and the current digital signal, and Rt represents the standard phase difference.

[0040] Preferably, the verification unit determines whether the measurement verification is qualified according to the measurement error as follows:

[0041] When the absolute value of the measurement error |Ep|≤∈, the measurement verification result is qualified, otherwise, the measurement verification fails, where ∈ represents the error range.

[0042] Compared with the prior art, the present invention provides a fiber optic voltage and current transformer calibration system, which has the following beneficial effects:

[0043] The present invention collects voltage and current signals from the optical fiber mutual inductor in real time and digitizes them, and accurately calculates the effective value and phase difference of the signal through low-pass filtering, amplification and demodulation. At the same time, Fourier transform is used to extract harmonic components and analyze their amplitude and frequency. The verification unit compares the processing results with the standard reference values ​​to effectively judge the qualification of the verification. Combining these functions, the system simplifies the operation process. The user can easily adjust parameters and restart the verification process through a friendly interface, making maintenance and data management more efficient, avoiding human verification errors, and improving verification accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the system flow of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Traditional calibration methods often require manual operation, which not only wastes time but also may lead to human errors, reducing the final calibration accuracy. Therefore, a fiber optic voltage and current transformer calibration system is proposed. Figure 1 , the system includes a voltage signal acquisition unit, a current signal acquisition unit, a signal processing unit, a verification unit and a display unit;

[0047] The voltage signal acquisition unit and the current signal acquisition unit acquire voltage and current signals from the optical fiber voltage transformer and the current transformer, and convert them into digital signals. The formula for converting the voltage signal from the optical fiber voltage transformer into a digital signal is as follows:

[0048]

[0049] Digital signals can be stored and transmitted more easily and are less susceptible to noise and interference than analog signals, thus ensuring the reliability and accuracy of the data. This conversion also allows the signal to be efficiently processed by digital signal processing algorithms, such as filtering, amplification, and various verification algorithms. In the formula, Dv[n] represents the voltage digital signal sampled at the nth time, V(n*Ts) represents the instantaneous voltage value sampled at time nTs, and V max It represents the maximum value of all voltage signals collected within the sampling period, Ts represents the sampling period, n represents the number of sampling times, Q(*) represents the quantization function, and N represents the number of quantization bits;

[0050] The formula for converting the current signal from the fiber optic current transformer into a digital signal is as follows:

[0051]

[0052] By converting the current signal into a digital signal, the stability and accuracy of the current signal during data acquisition and processing are ensured. The digitized current signal can not only eliminate the attenuation and distortion of the traditional analog signal during long-distance transmission, but also be processed and analyzed dynamically to respond to changes in the power system in real time. In the formula, DI[n] represents the digital current signal sampled for the nth time, I(n*Ts) represents the instantaneous current value sampled at time nTs, and I max It represents the maximum value of all current signals collected within the sampling period, Ts represents the sampling period, n represents the number of sampling times, Q(*) represents the quantization function, and N represents the number of quantization bits, which determines the resolution of the digital signal. The digital signal is easy to process with complex algorithms in the computer. In this way, the system can implement more complex control and maintenance strategies and provide more efficient power services for power users.

[0053] The signal processing unit calculates the effective values ​​of the voltage digital signal and the current digital signal and calculates the phase difference between the voltage digital signal and the current digital signal according to the converted current digital signal and voltage digital signal by low-pass filtering, amplifying and demodulating the voltage digital signal and the current digital signal, wherein:

[0054] The formula for low-pass filtering the voltage digital signal and the current digital signal is as follows:

[0055]

[0056] The purpose of low-pass filtering of digital signals is to remove high-frequency noise and unnecessary interference signals, thereby retaining useful low-frequency components. Signals in power systems are often affected by electromagnetic interference or other noise. Low-pass filters can effectively clean these signals, making the final measured voltage and current data more accurate and clean. In the formula, Y[n] represents the voltage digital signal and current digital signal after low-pass filtering, D[n] represents the voltage digital signal and current digital signal input for the nth time, M represents the window size of the filter, which determines the cutoff frequency of the filter, and k represents the weighting of the filter on the past M samples. Represents a sum operation, which adds the current sample value n to the sum of the previous M-1 sample values, using the reverse index Implementation means starting from D[n], and obtaining M samples of data backwards. It means that the average value of the signal in the window is obtained by dividing the summation result by M. The signal after low-pass filtering can more truly reflect the dynamic changes of the system, especially in transient analysis and harmonic analysis, ensuring the credibility of subsequent data processing and measurement results, thereby improving the overall performance of the system;

[0057] The formula for amplifying the voltage digital signal and the current digital signal is as follows:

[0058] Z[n]=G*Y[n]

[0059] The main benefit of amplifying digital signals is to enhance the detectability of weak signals. In actual measurements, the optical fiber voltage or current signal may be affected by factors such as noise and attenuation, resulting in a small signal amplitude, and may even lose important information in the subsequent processing stage. By amplifying the signal, the summer rate and related depth can be ensured, thereby improving the response speed and sensitivity of the system. In the formula, Z[n] represents the amplified voltage digital signal and current digital signal, H represents the amplification factor, and is a constant value greater than 1, and Y[n] represents the voltage digital signal and current digital signal output after low-pass filtering. The amplified signal enables subsequent digital processing (such as filtering and demodulation) to be carried out more effectively, reducing errors in subsequent links and ensuring that accurate and useful values ​​can be obtained throughout the measurement cycle;

[0060] The formula for demodulating the voltage digital signal and the current digital signal is as follows:

[0061] S[n]=Z[n]*cos(2π*f c *n*Ts)+LPF{Z[n]*sin(2π*f c *n*Ts)}

[0062] The process of demodulating digital signals can effectively restore the basic information of the signal, which is especially important in modulation and demodulation technology. Through demodulation, the system can restore the signal modulated on the carrier to its original information content, so that the person in charge can accurately analyze the actual situation of current and voltage changes. In the formula, S[n] represents the demodulated signal, Z[n] represents the amplified voltage digital signal and current digital signal, and f c represents the carrier frequency, that is, the frequency of the information signal contained in the modulated signal, which is measured by the mutual inductance calibration system. Ts represents the sampling period. LPF{Z[n]*sin(2π*f c *k*Ts)} represents low-pass filtering, which is used to remove high-frequency noise. k is the sample number, which represents the time series. c *k*Ts) represents the cosine component of the carrier signal, which is used for signal phase modulation, sin(2π*f c *k*Ts) represents the sinusoidal component of the carrier signal, which is used for signal amplitude modulation. After demodulation, important features of the signal (such as phase and amplitude) are clearly extracted, which is helpful for subsequent stability evaluation and operation adjustment. In addition, the demodulation process is crucial for real-time monitoring and feedback mechanisms, which can ensure that the system can respond quickly to emergencies and improve the safety and reliability of power equipment.

[0063] The formula for calculating the effective value of the voltage digital signal is as follows:

[0064]

[0065] The formula for calculating the effective value of the current digital signal is as follows:

[0066]

[0067] In the formula, V rms Represents the effective value of the voltage digital signal, V[e] represents the voltage sample value measured for the eth time, the processed voltage digital signal, P represents the total number of samples, the number of samples used to calculate the effective value, e represents the number of measurements, It means to sum the square values ​​of all voltage digital signal samples, divide the sum by P to get the average square value, and then take the square root to convert the calculated value back to the unit of voltage and get the actual effective value of the voltage digital signal, I rms Represents the effective value of the current digital signal, I[e] represents the current sample value measured for the eth time, the processed current digital signal, P represents the total number of samples, the number of samples used to calculate the effective value, e represents the number of measurements, It represents the sum of the square values ​​of all current digital signal samples, and the sum is divided by P to get the average square value. The square root is taken to convert the calculated value back to the unit of current and get the actual effective value of the current digital signal. The effective value provides an intuitive information, allowing users to clearly understand the power capacity of the actual voltage and current. The result of the effective value calculation helps to determine whether the power system meets the design standards and the stability of the system under load fluctuations. This data is the theoretical basis for evaluating the performance of electrical equipment and ensuring the operation of the system. It also provides an important reference for fault detection and maintenance, reduces power loss, and improves overall economic benefits.

[0068] The formula for calculating the phase difference between the voltage digital signal and the current digital signal is as follows:

[0069]

[0070] Phase difference is a key parameter for analyzing power loss, power factor, and equipment efficiency. It directly affects the energy efficiency and operational stability of the power system. When phase difference measurement is integrated into the instrument, it can help identify abnormal loads or nonlinear loads and prevent equipment damage and power loss. In the formula, It represents the phase difference between the voltage digital signal and the current digital signal, expressed in radians. Arctan represents the inverse tangent function. It means calculating the ratio of reactive components of voltage and current. The result is the phase difference of the signal. Accurate understanding of the phase relationship can also optimize power transmission and ensure equipment operation efficiency, which helps to improve the overall economy and safety of the system.

[0071] After calculating the signal phase difference, the calculated value needs to be Fourier transformed. Fast Fourier transform is used to improve the calculation efficiency, so as to quickly and accurately extract the harmonic components in the signal. When analyzing these harmonic components, the amplitude indicates the relative strength of each harmonic component in the signal, and the frequency reflects the periodic changes of these harmonics. By thresholding the extracted spectrum, important harmonic components can be screened out. Low-frequency harmonics are often closely related to system stability and quality, while high-frequency harmonics can indicate potential faults or interference. When analyzing the amplitude, we can further calculate the harmonic distortion (such as total harmonic distortion THD) to evaluate the power quality of the system. Through these analyses, we can better understand the characteristics of the signal, perform fault diagnosis, optimize equipment performance, and formulate effective filtering strategies when necessary to reduce the impact of harmonics on the system.

[0072] The verification unit compares the processed effective value and phase difference with the standard reference value, calculates the measurement error, and determines whether the measurement verification is qualified based on the measurement error, where:

[0073] The formula for measurement error is as follows:

[0074]

[0075] By comparing the actual measured value with the standard reference value, the system can promptly identify inaccuracies and deviations in the measurement process and provide necessary feedback for correction. In the formula, Ep represents the measurement error, Represents the phase difference between the voltage digital signal and the current digital signal. Rt represents the standard phase difference. Understanding the measurement error not only helps maintain the accuracy and stability of the equipment, but also can timely discover potential faults and problems and optimize maintenance plans. This process facilitates real-time monitoring and quality management of equipment conditions, significantly improves the operating efficiency and safety of the system, and ultimately achieves efficient use of resources.

[0076] When the absolute value of the measurement error |Ep|≤∈, the measurement verification result is qualified, otherwise, the measurement verification is unqualified, where ∈ indicates that the error range is 0.2;

[0077] The display unit shows the effective value of voltage and current, phase difference, harmonic components and calibration results, and provides an operation panel for users to adjust parameters and restart the calibration process.

[0078] Embodiment 1:

[0079] In this experiment, current and voltage samples were collected manually, and the sample data of voltage and current signals are as follows:

[0080] Voltage sample V[n]:

[0081] V[0]=11.0V;

[0082] V[1]=12.5V;

[0083] V[2] = 10.1V (this sample is lower than the actual value, probably due to interference);

[0084] V[3] = 9.5V (this sample is low, indicating a fault in the manual detection equipment);

[0085] V[4] = 14.0V (this sample is too high, possibly due to human error);

[0086] Current sample I[n]:

[0087] I[0] = 3.0A (this sample is too high, indicating device drift);

[0088] I[1] = 2.5A (this sample is lower than the actual value, probably due to environmental factors);

[0089] I[2] = 3.3A (this sample is too high, indicating device failure);

[0090] I[3] = 2.2A (this sample should meet the standard, but it does not truly reflect it);

[0091] I[4] = 4.0A (this sample is much higher than normal, indicating a device failure);

[0092] The total number of samples is 5, and the calculation is performed using the formula for the effective value of the voltage digital signal:

[0093]

[0094] Get V[0] 2 =121, V[1] 2 =156.25, V[2] 2 =102.01, V[3] 2 =90.25, V[4] 2 =196;

[0095] Sum Substituting the total number of samples,

[0096] Calculate using the formula for the effective value of the current digital signal:

[0097]

[0098] Get I[0] 2 =9, I[1] 2 =6.25, I[2] 2 =10.89, I[3] 2 =4.84, I[4] 2

[0099] =16.00

[0100] Sum Substituting the total number of samples,

[0101] At this time, the phase difference between the voltage digital signal and the current digital signal is:

[0102]

[0103] According to the above calculation, the phase difference is 14.74, the test detection theoretical circuit phase difference is 20.98, and the measurement error |Ep|=|14-20.98|=|-6.98|>0.2, which means that the verification result is obviously unqualified;

[0104] Embodiment 2:

[0105] In this experiment, after multiple measurements through the optical fiber voltage and current transformer calibration system, the sample data of voltage and current signals collected by the system are as follows:

[0106] Voltage sample V[n]:

[0107] V[0]=5.0, V[1]=7.0, V[2]=6.0, V[3]=8.0, V[4]=5.0;

[0108] Current sample I[n]:

[0109] I[0]=2.0, I[1]=2.5, I[2]=2.0, I[3]=3.0, I[4]=2.5;

[0110] The total number of samples is 5, and the calculation is performed using the formula for the effective value of the voltage digital signal:

[0111]

[0112] Get V[0] 2 =25, V[1] 2 =49, V[2] 2 =36, V[3] 2 =64, V[4] 2 =25;

[0113] Sum Substituting the total number of samples,

[0114] Calculate using the formula for the effective value of the current digital signal:

[0115]

[0116] Get I[0] 2 =4, I[1] 2 =6.25, I[2] 2 =4.0, I[3] 2 =9.0, I[4] 2 =6.25

[0117] Sum Substituting the total number of samples,

[0118]

[0119] At this time, the phase difference between the voltage digital signal and the current digital signal is:

[0120]

[0121] According to the above calculation, the phase difference is 21, the test detection theoretical circuit phase difference is 20.98, the measurement error |Ep|=|21-20.98|=|0.02|<0.2, which means the verification result is qualified and valid;

[0122] It is verified through the above experiments that the present invention makes data maintenance and data management more efficient, avoids errors caused by human verification, and improves verification accuracy.

[0123] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fiber optic voltage and current transformer calibration system, characterized in that: It includes a voltage signal acquisition unit, a current signal acquisition unit, a signal processing unit, a verification unit and a display unit; The voltage signal acquisition unit acquires the voltage signal from the optical fiber voltage transformer, converts it into a voltage digital signal, and sends the voltage digital signal to the signal processing unit; The current signal acquisition unit acquires the current signal from the optical fiber current transformer, converts it into a current digital signal, and sends the current digital signal to the signal processing unit; The signal processing unit calculates the effective values ​​of the voltage digital signal and the current digital signal after low-pass filtering, amplification and demodulation according to the converted voltage digital signal and current digital signal, and calculates the phase difference between the voltage digital signal and the current digital signal; The verification unit calculates the measurement error according to the calculated effective values ​​of the voltage digital signal and the current digital signal and the phase difference between the voltage digital signal and the current digital signal, determines whether the measurement verification is qualified according to the measurement error, and sends the verification result to the display unit; The display unit displays the effective value of voltage and current, phase difference and calibration results, and provides an operation panel for the user to adjust parameters and restart the calibration process.

2. The optical fiber voltage and current transformer calibration system according to claim 1, characterized in that: The voltage digital signal conversion formula is as follows: In the formula, Dv[n] represents the voltage digital signal sampled at the nth time, V(n*Ts) represents the instantaneous voltage value sampled at time nTs, and V max It represents the maximum value of all voltage signals collected within the sampling period, Ts represents the sampling period, n represents the number of sampling times, Q(*) represents the quantization function, and N represents the number of quantization bits.

3. The optical fiber voltage and current transformer calibration system according to claim 2, characterized in that: The current digital signal conversion formula is as follows: In the formula, DI[n] represents the current digital signal sampled at the nth time, I(n*Ts) represents the instantaneous current value sampled at time nTs, and I max It represents the maximum value of all current signals collected within the sampling period, Ts represents the sampling period, n represents the number of sampling times, Q(*) represents the quantization function, and N represents the number of quantization bits.

4. The optical fiber voltage and current transformer calibration system according to claim 3, characterized in that: The calculation formula of the low-pass filter is as follows: In the formula, Y[n] represents the voltage digital signal and current digital signal after low-pass filtering, D[n] represents the voltage digital signal and current digital signal input for the nth time, M represents the window size of the filter, and k represents the weighting of the filter on the past M samples. Represents a sum operation, which adds the current sample value n to the sum of the previous M-1 sample values, using the reverse index Implementation means starting from D[n], and obtaining M samples of data backwards. It means that the average value of the signal within the window is obtained by dividing the summation result by M.

5. The optical fiber voltage and current transformer calibration system according to claim 4, characterized in that: The formula for amplifying the voltage digital signal and the current digital signal is as follows: Z[n]=G*Y[n] In the formula, Z[n] represents the amplified voltage digital signal and current digital signal, G represents the amplification factor and is a constant value greater than 1, and Y[n] represents the voltage digital signal and current digital signal output after low-pass filtering.

6. The optical fiber voltage and current transformer calibration system according to claim 5, characterized in that: The formula for demodulating the voltage digital signal and the current digital signal by the signal processing unit is as follows: S[n]=Z[n]*cos(2π*f c *k*Ts)+LPF{Z[n]*sin(2π*f c *k*Ts)} In the formula, S[n] represents the demodulated voltage digital signal and current digital signal, Z[n] represents the amplified voltage digital signal and current digital signal, and f c represents the carrier frequency, that is, the frequency of the information signal contained in the modulated signal, which is measured by the mutual inductance calibration system. Ts represents the sampling period. LPF{Z[n]*sin(2π*f c *k*Ts)} represents low-pass filtering, which is used to remove high-frequency noise. k is the sample number, which represents the time series. c *k*Ts) represents the cosine component of the carrier signal, which is used for signal phase modulation, sin(2π*f c *k*Ts) represents the sinusoidal component of the carrier signal, which is used for signal amplitude modulation.

7. The optical fiber voltage and current transformer calibration system according to claim 6, characterized in that: The calculation formula of the effective value of the voltage digital signal is as follows: In the formula, V rms Represents the effective value of the voltage digital signal, V[e] represents the voltage sample value measured for the eth time, the processed voltage digital signal, P represents the total number of samples, the number of samples used to calculate the effective value, e represents the number of measurements, It means to sum the square values ​​of all voltage digital signal samples, divide the sum by P to get the average square value, and then take the square root to convert the calculated value back to the unit of voltage and get the actual effective value of the voltage signal; The formula for calculating the effective value of the current digital signal is as follows: In the formula, I rms Represents the effective value of the current digital signal, I[e] represents the current sample value measured for the eth time, the processed current digital signal, P represents the total number of samples, the number of samples used to calculate the effective value, e represents the number of measurements, It means summing the square values ​​of all current digital signal samples, dividing the sum by P to obtain the average square value, and taking the square root is to convert the calculated value back to the unit of current and obtain the actual effective value of the current signal.

8. The optical fiber voltage and current transformer calibration system according to claim 7, characterized in that: The calculation formula of the phase difference between the voltage digital signal and the current digital signal is as follows: In the formula, It represents the phase difference between the voltage digital signal and the current digital signal, expressed in radians. Arctan represents the inverse tangent function. It means calculating the ratio of the reactive components of voltage and current, and the result is the phase difference of the signal.

9. The optical fiber voltage and current transformer calibration system according to claim 8, characterized in that: The formula for calculating the measurement error of the verification unit is as follows: In the formula, Ep represents the measurement error, It represents the phase difference between the voltage digital signal and the current digital signal, and Rt represents the standard phase difference.

10. The optical fiber voltage and current transformer calibration system according to claim 9, characterized in that: The method in which the verification unit determines whether the measurement verification is qualified according to the measurement error is as follows: When the absolute value of the measurement error |Ep|≤∈, the measurement verification result is qualified, otherwise, the measurement verification fails, where ∈ represents the error range.

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