A zero sequence direction discrimination method, electronic device and storage medium

Abstract

The present application relates to the technical field of relay protection, in particular to a zero sequence direction discrimination method, an electronic device and a storage medium. The method comprises the following steps: 1) obtaining a zero sequence voltage and a differential zero sequence current signal output by a Rogowski coil, and calculating the average values of the zero sequence voltage and the differential zero sequence current signal; 2) calculating the correlation coefficient of the zero sequence voltage and the differential zero sequence current signal according to the calculated average values of the zero sequence voltage and the differential zero sequence current signal; 3) determining the setting value of a zero sequence direction element, and comparing the size relationship between the correlation coefficient and the setting value of the zero sequence direction element, and judging whether the zero sequence direction element acts and the action direction according to the size relationship between the correlation coefficient and the setting value of the zero sequence direction element. The control of the zero sequence direction element is completed, the influence of the additional components introduced by the integrator of the Rogowski coil on the protection performance is avoided, and the protection performance is improved.

Description

Technical Field

[0001] This invention relates to a zero-sequence direction determination method, electronic device, and storage medium, belonging to the field of relay protection technology. Background Technology

[0002] Current transformers are the source of data for relay protection, and their performance directly affects the protection's operation. Rogowski coil electronic current transformers are unaffected by saturation and ferroresonance, exhibiting good linearity, wide bandwidth, high measurement accuracy, and digital output, aligning with the development trend of intelligent substations and thus receiving widespread attention and large-scale application. The output of a Rogowski coil is the derivative of the measured signal; therefore, an integrator is required to restore the derivative to a signal proportional to the primary signal. Integrators are divided into analog integrators and digital integrators. Analog integrators, during operation, are susceptible to the influence of environmental temperature changes, humidity, and electromagnetic interference, resulting in poor stability. The accuracy of digital integrators is affected by the accuracy of A / D conversion, the number of sampling points, and the accuracy of calculation, limiting the actual performance of the algorithm. Furthermore, under external disturbances, the integrator may cause the disturbance signal to persist in the output for an extended period, affecting the performance of the current transformer protection. Summary of the Invention

[0003] The purpose of this invention is to provide a zero-sequence direction discrimination method, electronic device, and storage medium to solve the problem of low calculation accuracy caused by the introduction of additional components by the integrator in Rogowski coil current transformers, which affects the protection performance.

[0004] To achieve the above objectives, the present invention includes:

[0005] A zero-order direction determination method of the present invention includes the following steps:

[0006] 1) Obtain the zero-sequence voltage and the differential zero-sequence current signal output by the Rogowski coil, and calculate the average value of the zero-sequence voltage and the differential zero-sequence current signal;

[0007] 2) Calculate the correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal based on the calculated average values ​​of the zero-sequence voltage and the differential zero-sequence current signal;

[0008] 3) Determine the set value of the zero-sequence direction element, and compare the magnitude relationship between the correlation coefficient and the set value of the zero-sequence direction element. Based on the magnitude relationship between the correlation coefficient and the set value of the zero-sequence direction element, determine whether the zero-sequence direction element is activated and the direction of activation.

[0009] Beneficial effects: This invention eliminates the need for an integrator. By acquiring the zero-sequence voltage and differential zero-sequence current signals, it calculates the average value of these signals. Using this average value, it calculates the correlation coefficient between the zero-sequence voltage and differential zero-sequence current signals. The correlation coefficient is then compared with the set value of the zero-sequence directional element. Based on the relationship between the correlation coefficient and the set value of the zero-sequence directional element, it determines whether the zero-sequence directional element has activated and in what direction. This further ensures accurate determination of whether the zero-sequence directional element has activated, avoiding the impact of additional components introduced by the integrator on protection performance.

[0010] Further, determining the setpoint of the zero-sequence direction element includes:

[0011] Based on the equivalent zero-sequence impedance angle of the system behind the protection installation point. Determine the correlation coefficient setpoint for the phase response of the Rogowski coil at a power frequency of 50 Hz, given its transfer function.

[0012] The value of the zero-sequence direction element is determined based on the correlation coefficient.

[0013] Beneficial effect: By determining the value of the correlation coefficient, the calculation of the zero-sequence direction element is guaranteed.

[0014] Furthermore, the setpoint of the zero-sequence direction element includes a high setpoint and a low setpoint. The setpoint of the zero-sequence direction element is determined based on the correlation coefficient setpoint, including:

[0015] like High set value and low fixed value They are respectively:

[0016]

[0017] like High set value and low fixed value They are respectively:

[0018]

[0019] in, Set a value for the correlation coefficient.

[0020] Beneficial effect: The calculation of the zero-sequence direction element setpoint is completed by the above formula, which ensures the control of the zero-sequence direction element operation.

[0021] Furthermore, the correlation coefficient is fixed. The calculation method is as follows:

[0022]

[0023] in, To protect the equivalent zero-sequence impedance angle of the system behind the installation point, Let be the transfer function of the Rogowski coil and its phase response at a power frequency of 50 Hz.

[0024] Beneficial effect: The calculation of the correlation coefficient setting ensures the calculation of the zero-sequence direction element setting.

[0025] Furthermore, the formula for calculating the correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal is as follows:

[0026]

[0027] in, The correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal. It is the zero-sequence voltage. The average value of the zero-sequence voltage. The differential zero-sequence current, is the average value of the differential zero-sequence current, k is the sampling number, and N is the number of sampling points in one power frequency cycle.

[0028] Beneficial effect: The correlation coefficients between zero-sequence voltage and differential zero-sequence current were calculated.

[0029] Furthermore, the set value of the zero-sequence direction element includes a high set value and a low set value. If the correlation coefficient is less than the high set value and greater than the low set value, it indicates that the point is a positive direction fault and the zero-sequence direction element will operate; otherwise, it indicates that the zero-sequence direction element will not operate.

[0030] Beneficial effect: Enables the determination of the direction of zero-sequence direction elements.

[0031] Further, the average values ​​of the zero-sequence voltage and differential zero-sequence current signals are calculated, including: performing low-pass filtering on the acquired zero-sequence voltage and differential zero-sequence current signals, and using the low-pass filtered signals to calculate the average values ​​of the zero-sequence voltage and differential zero-sequence current signals.

[0032] Beneficial effects: The zero-sequence voltage and differential zero-sequence current signals are low-pass filtered, and the average values ​​of the zero-sequence voltage and differential zero-sequence current signals are calculated using the low-pass filtered signals.

[0033] The present invention also provides an electronic device, including a processor, the processor being configured to execute program instructions to implement the zero-order direction discrimination method as described above.

[0034] Beneficial effects: This electronic device can realize the above-mentioned zero-sequence direction discrimination method, determine whether the zero-sequence direction element is activated, and complete the direction discrimination of the zero-sequence direction element. It avoids the impact of the additional component introduced by the integrator on the protection performance and improves the reliability of the protection.

[0035] The present invention also provides a storage medium storing program instructions for implementing the zero-order direction discrimination method as described above.

[0036] Beneficial effect: The program instructions stored in the storage medium complete the above-mentioned zero-order direction discrimination method. Attached Figure Description

[0037] Figure 1 This is a flowchart of the zero-order direction discrimination method of the present invention;

[0038] Figure 2 This is the equivalent circuit diagram of the Rogowski coil of the present invention;

[0039] Figure 3 This is a schematic diagram of the amplitude-frequency response of the low-pass filter of the present invention. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0041] Method Implementation Examples:

[0042] An embodiment of the zero-order direction discrimination method of the present invention is as follows: Figure 1 As shown, it includes the following steps:

[0043] Step 1: Calculate the set value of the zero-sequence direction element.

[0044] 1) Obtain the transfer function of the Rogowski coil and its phase response at power frequency.

[0045] According to the equivalent circuit of the Rogowski coil (e.g. Figure 2 (As shown) and the parameters of the electronic components, the transfer function of the Rogowski coil is obtained. The phase response of the Rogowski coil at the power frequency of 50Hz is calculated and denoted as . .

[0046] 2) Calculate the constant value of the zero-sequence direction based on the phase response of the coil at power frequency calculated in step (1) and the zero-sequence impedance angle of the line. The steps are as follows:

[0047] ① Define parameters ,in, To protect the equivalent zero-sequence impedance angle of the system behind the installation location;

[0048] ② Determine the setpoint of the zero-sequence direction element according to the following formula:

[0049] like High set value and low fixed value They are respectively:

[0050] (1)

[0051] like High set value and low fixed value They are respectively:

[0052] (2)

[0053] in, Set a value for the correlation coefficient.

[0054] Step 2: Calculate the correlation coefficient between zero-sequence voltage and zero-sequence current.

[0055] 1) The zero-sequence voltage signal and the differential zero-sequence current signal output from the Rogowski coil are filtered by a low-pass filter. The amplitude-frequency response of the low-pass filter is as follows: Figure 3 As shown, its low-pass filter form is:

[0056] (3)

[0057] in, For sampled data, For sampling sequence number, The output data is the sampled data after passing through a low-pass filter, and the filter coefficients are... The values ​​are 0.0058, 0.0136, 0.0265, 0.0438, 0.0641, 0.0848, 0.1029, 0.1152, 0.1196, 0.1152, 0.1029, 0.0848, 0.0641, 0.0438, 0.0265, 0.0136, and 0.0058, respectively.

[0058] 2) The instantaneous values ​​of the three-phase voltages at the measurement points are summed to obtain the zero-sequence voltage, and the instantaneous values ​​of the phase currents output by the Rogowski coils are summed to obtain the differential zero-sequence current. The formulas for calculating the average values ​​of the zero-sequence voltage and differential zero-sequence current signals over one cycle are:

[0059] (4)

[0060] in, For sampled data, For sampling sequence number, The average value of the sampled data. This represents the number of sampling points per power frequency cycle.

[0061] 3) Substitute the zero-sequence voltage and differential zero-sequence current signals as sampling data into formula (4) to calculate the zero-sequence voltage at each sampling point. and the average value of the differential zero-sequence current .

[0062] 4) Calculate the correlation coefficient between zero-sequence voltage and differential zero-sequence current. The formula is:

[0063] (5)

[0064] in, It is the zero-sequence voltage. The average value of the zero-sequence voltage. The differential zero-sequence current, is the average value of the differential zero-sequence current, k is the sampling number, and N is the number of sampling points in one power frequency cycle.

[0065] Step 3: Determine whether the zero-sequence direction element operates based on the calculation results of Step 1 and Step 2.

[0066] The calculated value and the set value of the correlation coefficient between the zero-sequence voltage and the differential zero-sequence current are compared to determine whether the zero-sequence directional element operates. Specifically, the calculated correlation coefficient is compared with the set value of the zero-sequence directional element. If the calculated correlation coefficient is less than the high set value and greater than the low set value, then the point is a positive direction fault and the zero-sequence directional element operates; otherwise, the zero-sequence directional element does not operate.

[0067] This method eliminates the integrator, constructing protection using the differential signal output from the Rogowski coil, thus avoiding the impact of additional components introduced by the integration stage on protection performance. A low-pass filter is used to process the zero-sequence voltage and differential current signals, eliminating the influence of higher harmonics. The setting value of the zero-sequence directional element is calculated using the phase response of the Rogowski coil transfer function at power frequency and the zero-sequence impedance angle of the line. This setting value calculation can be performed offline without affecting the protection's operating speed. Correlation coefficients are calculated using one week's worth of sampled data, resulting in high stability.

[0068] Electronic device example:

[0069] An embodiment of the electronic device of the present invention includes a memory, a processor, and an internal bus. The processor and the memory communicate and exchange data with each other through the internal bus. The processor can be a microprocessor (MCU), a programmable logic device (FPGA), or other processing device. The memory can be any type of memory that stores information electrically; it can also be any type of memory that stores information magnetically, such as a hard disk. The processor executes program instructions stored in the memory to implement a zero-order direction determination method described in the method embodiment of the present invention.

[0070] Storage medium examples:

[0071] The storage medium embodiment of the present invention includes program instructions in the storage medium, and the method embodiment of the present invention is implemented through the program instructions in the storage medium to perform a zero-order direction discrimination method described in the present invention.

Claims

1. A method for determining zero-order direction, characterized in that, Includes the following steps: 1) Obtain the zero-sequence voltage and the differential zero-sequence current signal output by the Rogowski coil, and calculate the average value of the zero-sequence voltage and the average value of the differential zero-sequence current signal respectively; 2) Calculate the correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal based on the obtained average value; 3) Based on the equivalent zero-sequence impedance angle of the system behind the protection installation point. The transfer function of the Rogowski coil and its phase response at power frequency Determine the correlation coefficient constant K1. ; and then the high set value is determined according to the following method. and low fixed value The zero-sequence direction element's set value: If but and ,like but and ; 4) Compare the correlation coefficient with the set value of the zero-sequence direction element, and determine whether the zero-sequence direction element is activated and the direction of activation based on the correlation coefficient.

2. The zero-order direction discrimination method according to claim 1, characterized in that, The formula for calculating the correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal is: in, The correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal. It is the zero-sequence voltage. The average value of the zero-sequence voltage. The differential zero-sequence current, is the average value of the differential zero-sequence current, k is the sampling sequence number, N is the number of sampling points in one power frequency cycle, and j is the number of sampling points.

3. The zero-order direction discrimination method according to claim 1, characterized in that, If the correlation coefficient is less than the high set value and greater than the low set value, it indicates a positive direction fault, and the zero-sequence direction element will operate; otherwise, the zero-sequence direction element will not operate.

4. The zero-order direction discrimination method according to claim 1, characterized in that, The calculation of the average value of the zero-sequence voltage and the differential zero-sequence current signal includes: performing low-pass filtering on the acquired zero-sequence voltage and the differential zero-sequence current signal, and using the low-pass filtered signal to calculate the average value of the zero-sequence voltage and the differential zero-sequence current signal.

5. An electronic device, characterized in that, Includes a processor, the processor being configured to execute program instructions to implement the following method: 1) Obtain the zero-sequence voltage and the differential zero-sequence current signal output by the Rogowski coil, and calculate the average value of the zero-sequence voltage and the average value of the differential zero-sequence current signal respectively; 2) Calculate the correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal based on the obtained average value; 3) Based on the equivalent zero-sequence impedance angle of the system behind the protection installation point. The transfer function of the Rogowski coil and its phase response at 50 Hz. Determine the correlation coefficient constant K1. ; and then the high set value is determined according to the following method. and low fixed value The zero-sequence direction element's set value: If but and ,like but and ; 4) Compare the correlation coefficient with the set value of the zero-sequence direction element, and determine whether the zero-sequence direction element is activated and the direction of activation based on the correlation coefficient.

6. The electronic device according to claim 5, characterized in that, The formula for calculating the correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal is: in, The correlation coefficient between the zero-sequence voltage and the differential zero-sequence current signal. It is the zero-sequence voltage. The average value of the zero-sequence voltage. The differential zero-sequence current, is the average value of the differential zero-sequence current, k is the sampling sequence number, N is the number of sampling points in one power frequency cycle, and j is the number of sampling points.

7. The electronic device according to claim 5, characterized in that, If the correlation coefficient is less than the high set value and greater than the low set value, it indicates a positive direction fault, and the zero-sequence direction element will operate; otherwise, the zero-sequence direction element will not operate.

8. The electronic device according to claim 5, characterized in that, The calculation of the average value of the zero-sequence voltage and the differential zero-sequence current signal includes: performing low-pass filtering on the acquired zero-sequence voltage and the differential zero-sequence current signal, and using the low-pass filtered signal to calculate the average value of the zero-sequence voltage and the differential zero-sequence current signal.

9. A storage medium, characterized in that, The storage medium stores program instructions for implementing the zero-order direction discrimination method as described in any one of claims 1 to 4.

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