Method and device for screening protection maloperation during application of active electronic transformer

Abstract

The invention relates to a method and a device for screening protection maloperation when an active electronic transformer is applied, and belongs to the field of relay protection. The screening method comprises the following steps: 1) under a no-load switching-on condition, calculating primary current and primary voltage at the installation position of the active electronic transformer corresponding to permutation and combination under different working conditions; permutation and combination of different working conditions comprise permutation and combination of different line lengths and different system impedance sizes; 2) according to the transfer function of each link of the active electronic transformer, taking the primary current and the primary voltage under different working conditions as input quantities, and calculating to obtain the output quantity of the active electronic transformer; and 3) substituting the output quantities of the active electronic transformer corresponding to different working conditions into a protection criterion, and screening the working conditions of which the criterion results are protection actions as maloperation working conditions. According to the method, the purpose of rapidly screening the working conditions of the relay protection misoperation can be achieved.

Description

Technical Field

[0001] The present invention relates to a screening method and device for protection malfunction when applying active electronic current transformers, belonging to the field of relay protection. Background Art

[0002] With the rapid growth of the installed capacity of new energy power generation and the wide application of UHV DC large-scale cross-regional power transmission, the power electronic characteristics of the power system have become increasingly obvious. The fault characteristics of the power electronic power system have changed greatly compared with the traditional power system. As a specialized anti-fault technology, relay protection is the first line of defense in the power system security defense system and plays a crucial role in ensuring the safe operation of the power system. The transmission effect of electrical quantities by transformers directly affects the performance of relay protection. Traditional transformers have problems such as CT saturation and the transient transmission process of CVT. The error in the electrical quantity transmission process, intertwined with the transient process of electrical quantities brought about by the rapid regulation characteristics of power electronic devices in new energy power generation during power system faults, further deteriorates the performance of relay protection.

[0003] Electronic current transformers have excellent transient transmission characteristics and are expected to solve the above problems. However, in actual engineering applications, there have been cases where abnormal outputs of electronic current transformers have led to protection malfunctions because the integration link in the electronic current transformer amplifies the transmission error, deteriorating the dynamic transmission characteristics of the electronic current transformer. In severe cases, abnormal output signals will cause relay protection malfunctions. Therefore, there is an urgent need for a screening method for protection malfunctions when applying active electronic current transformers to screen the operating conditions of relay protection malfunctions. Summary of the Invention

[0004] The purpose of the present invention is to provide a screening method and device for protection malfunctions when applying active electronic current transformers to solve the problem in the prior art that it is difficult to screen the operating conditions of relay protection malfunctions when there are active electronic current transformers.

[0005] To achieve the above purpose, the solution of the present invention includes:

[0006] A screening method for protection malfunctions when applying active electronic current transformers of the present invention includes the following steps:

[0007] 1) Under no-load closing conditions, calculate the primary current and primary voltage corresponding to the installation location of the active electronic current transformer under different permutations and combinations of operating conditions; different permutations and combinations of operating conditions include permutations and combinations of different line lengths and different system impedance magnitudes;

[0008] 2) According to the transfer function of each link of the active electronic current transformer, using the primary current and primary voltage under different operating conditions as input quantities, calculate the output quantity of the active electronic current transformer;

[0009] 3) Substitute the output of the active electronic current transformer corresponding to different working conditions into the protection criterion, and screen the working conditions with the criterion result of protection action as misoperation conditions.

[0010] Furthermore, the permutations and combinations of different working conditions include the permutations and combinations of different line lengths, different system impedance magnitudes, different voltage levels, different line parameters, and different closing angles.

[0011] Furthermore, the active electronic current transformer includes an electronic voltage transformer and an electronic current transformer;

[0012] The electronic current transformer includes a Rogowski coil section, an anti-aliasing filter section, an analog-to-digital conversion section, and a digital integration section;

[0013] The electronic voltage transformer includes a capacitive voltage divider section, an anti-aliasing filter section, a analog conversion section, and a digital integration section.

[0014] Furthermore, the expression of the primary current after passing through the Rogowski coil section I rc (t) is as follows:

[0015]

[0016] Where

[0017] s i3 =-α + jβ; s i4 =-α - jβ;

[0018]

[0019] Where, t represents the time domain time; I m is the amplitude of the input current signal, α is the reciprocal of the decay time constant of the input signal, β is the angular frequency of the input signal, is the initial phase of the input signal, M is the equivalent mutual inductance between the induced electromotive force of the Rogowski coil and the primary current, R r is the total resistance of the coil winding and the lead wire, L is the inductance of the Rogowski coil, C0 is the stray capacitance of the Rogowski coil, R a is the load resistance.

[0020] Furthermore, the expression of the primary current after passing through the Rogowski coil section I rc (t) is related to the value of ζ;

[0021] When ζ > 1, s i1 and s i2 are unequal real numbers, K i1 and K i2 are real numbers, Ki3 and K i4 are conjugate complex numbers. At this time, I rc (t) is expressed by the following formula:

[0022]

[0023] When 0 < ζ < 1, s i1 and s i2 are conjugate complex numbers, K i1 and K i2 are conjugate complex numbers, K i3 and K i4 are conjugate complex numbers. Let p = ζω n , then at this time, I rc (t) is expressed by the following formula:

[0024]

[0025] where, is the argument of the complex number K i3 ; is the argument of the complex number K i1 ;

[0026] Furthermore, after the primary voltage passes through the capacitor voltage divider section, the time-domain expression U ev (t) of the signal output by the capacitor voltage divider section is the following formula:

[0027]

[0028] where, s u1 = -1 / (C3R u + C2R u ); s u2 = -α + jβ; s u3 = -α - jβ;

[0029]

[0030] where, U m is the amplitude of the input voltage signal, α is the reciprocal of the decay time constant of the input signal, β is the angular frequency of the input signal, is the initial phase of the input signal, C3 and C2 are the capacitances of the high-voltage arm and low-voltage arm of the capacitor voltage divider respectively, R is the precision sampling resistor, and R2 is the load resistor;

[0031] When K u1 is a real number and K u2 and K u3 are conjugate complex numbers, the expression form of U ev (t) is the following formula:

[0032]

[0033] Among them, is the argument of the complex number K u2 .

[0034] Furthermore, the transfer function H Be (s) of the anti-aliasing filter section is as follows:

[0035]

[0036] Among them, s is the Laplace variable.

[0037] Furthermore, the transfer function H B (z) of the digital integrator section is as follows:

[0038]

[0039] Among them, k B and c B are both parameters of the digital integrator, T is the sampling interval, and z is the variable in the complex frequency domain.

[0040] Furthermore, the protection criterion at least includes: sampled value differential protection, non-differential filtered power frequency phasor differential protection, differential filtered power frequency phasor differential protection, non-differential filtered power frequency phasor distance protection, differential filtered power frequency phasor distance protection, and differential equation distance protection.

[0041] A protection misoperation screening device when applying an active electronic current transformer according to the present invention includes a processor, and the processor is used to execute a computer program to implement the method steps of the protection misoperation screening method when applying an active electronic current transformer as described above.

[0042] The beneficial effects of the present invention are as follows: As a pioneering invention, the present invention provides a protection misoperation screening method and device when applying an active electronic current transformer. By calculating the primary current and primary voltage at the installation location of the active electronic current transformer corresponding to the permutations and combinations of different working conditions under no-load closing; the permutations and combinations of different working conditions include the permutations and combinations of different line lengths and different system impedance magnitudes; then, according to the transfer functions of each link of the active electronic current transformer, using the primary current and primary voltage under different working conditions as input quantities, the output quantity of the active electronic current transformer is calculated; finally, the output quantities of the active electronic current transformer corresponding to different working conditions are brought into the protection criterion, and the working conditions with the criterion result of protection action are screened as misoperation conditions, so as to achieve the purpose of quickly screening the misoperation conditions of relay protection, and improve the performance and reliability of relay protection in a power electronic power system. Description of the Drawings

[0043] Figure 1 It is a schematic structural diagram of an equivalent circuit for no-load closing of a transmission line circuit breaker provided by an embodiment of the present invention;

[0044] Figure 2 It is a schematic structural diagram of an analysis system for dynamic transfer characteristics of an active electronic current transformer provided by an embodiment of the present invention;

[0045] Figure 3 It is a schematic diagram of a transfer link of an electronic current transformer provided by an embodiment of the present invention;

[0046] Figure 4 It is a schematic structural diagram of an equivalent circuit of a Rogowski coil provided by an embodiment of the present invention;

[0047] Figure 5 It is a schematic diagram of a transfer link of a Rogowski coil provided by an embodiment of the present invention;

[0048] Figure 6 It is a schematic diagram of a transfer link of an electronic voltage transformer provided by an embodiment of the present invention;

[0049] Figure 7 It is a schematic structural diagram of an equivalent circuit of a capacitive voltage divider provided by an embodiment of the present invention;

[0050] Figure 8 It is a schematic diagram of a transfer link of a capacitive voltage divider provided by an embodiment of the present invention. Detailed implementation manners

[0051] To make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be described in detail clearly and completely below with reference to the accompanying drawings and embodiments.

[0052] The concept of the present invention lies in: inputting the voltage and current values under the condition of non-operation of the protection into the active electronic current transformer, and inputting the voltage value and current value after passing through the active electronic current transformer into the protection criterion. If the result is protection action, it is regarded as misoperation.

[0053] Specifically: the screening method and screening device provided by the present invention calculate the primary current and primary voltage at the installation location of the active electronic current transformer corresponding to different permutations and combinations of working conditions under no-load closing; the permutations and combinations of different working conditions include permutations and combinations of different line lengths and different system impedance magnitudes; then, according to the transfer function of each link of the active electronic current transformer, using the primary current and primary voltage under different working conditions as input quantities, the output quantity of the active electronic current transformer is calculated; finally, the output quantities of the active electronic current transformer corresponding to different working conditions are brought into the protection criterion, and the working conditions with the protection action as the criterion result are screened as misoperation working conditions.

[0054] An embodiment of a screening method for protection maloperation when applying active electronic current transformers:

[0055] The screening method for protection maloperation when applying active electronic current transformers provided by the embodiment of the present invention is used to analyze the possibility of abnormal output of electronic current transformers causing maloperation of relay protection in the full frequency band within the transmission signal bandwidth, provide a basis for targeted improvement of the dynamic transfer characteristics of active electronic current transformers, and improve the performance and reliability of relay protection in a power electronic power system.

[0056] The screening method for protection maloperation when applying active electronic current transformers depends on the equivalent circuit during no-load closing of a transmission line circuit breaker. That is, first, draw the equivalent circuit during no-load closing of the circuit breaker. Through the analysis of the equivalent circuit, obtain the primary current and primary voltage at the installation location of the active electronic current transformer. Then, pass the primary current and primary current through the active electronic current transformer respectively to obtain the output voltage and output current. Finally, input the output voltage and output current into the protection criterion to screen out the maloperation conditions.

[0057] Taking the no-load closing condition of a transmission line circuit breaker as an example, the screening method for protection maloperation when applying active electronic current transformers will be described below.

[0058] In the first step, it is necessary to establish the equivalent circuit during no-load closing of a specific circuit breaker and derive the expressions of the voltage and current at the protection installation location under no-load closing conditions.

[0059] Figure 1 is a schematic structural diagram of an equivalent circuit for no-load closing of a transmission line circuit breaker provided by the embodiment of the present invention. As Figure 1 shown, R s and L s are the positive sequence resistance and inductance of the system respectively, and R l , L l and C l are the positive sequence resistance, inductance and capacitance of the entire line length respectively. According to Figure 1 the expressions of the voltage and current at the protection installation location can be derived.

[0060] Assume that the system power supply voltage expression is Define

[0061]

[0062] where U m is the amplitude of the input voltage signal; ω is the angular velocity corresponding to the power frequency; is the initial phase of the input signal.

[0063] Then, the current i(t) at the relay protection measurement point (i.e., the current at the protection installation location) and the voltage u(t) at the relay protection measurement point (i.e., the voltage at the protection installation location) are respectively shown in the following formulas (1) and (2):

[0064]

[0065] Among them, k i1 = ωC l U cm ; k i2 = -C l (δK1 + χK2); k i3 = C l (-δK2 + χK1);

[0066] Among them,

[0067] Among them,

[0068] Among them, t represents the time domain time.

[0069] Step 2: Derive the current output signal after the Rogowski coil.

[0070] The current input signal at the relay protection measurement point at the protection installation location is collected by the Rogowski coil. As can be seen from Equation (1), the signal input to the Rogowski coil consists of two parts, namely the power frequency signal and the decaying periodic signal, and both of these signals are represented by the following formula (3):

[0071]

[0072] Among them, α is the reciprocal of the decay time constant of the input signal; when α = 0, the input signal I h (t) to the Rogowski coil is the power frequency signal; when α ≠ 0, the input signal I h (t) to the Rogowski coil is the decaying periodic signal; β is the angular frequency of the input signal; I m is the amplitude of the input current signal.

[0073] The active electronic current transformer includes an electronic voltage transformer and an electronic current transformer. Among them, the signal transformation link of the electronic current transformer is as Figure 3 shown, Figure 3 is a schematic diagram of the signal transformation link of an electronic current transformer provided in an embodiment of the present invention. As Figure 3 shown, it includes a Rogowski coil link, an anti-aliasing filter link, an analog-to-digital conversion link, and a digital integration link.

[0074] Figure 4 is a schematic structural diagram of an equivalent circuit of a Rogowski coil provided by an embodiment of the present invention. As Figure 4 shown, M is the equivalent mutual inductance between the induced electromotive force of the Rogowski coil and the primary current; R r is the total resistance of the coil winding and the lead, L is the inductance of the Rogowski coil; C0 is the stray capacitance of the Rogowski coil; R a is the load resistance; i(t) is the primary current, e(t) is the induced electromotive force of the Rogowski coil; u(t) is the output signal.

[0075] Figure 5 is a schematic diagram of a transmission link of a Rogowski coil provided by an embodiment of the present invention. As Figure 5 shown, Figure 5 in (a) is the transfer function of the Rogowski coil when ζ>1; Figure 5 in (b) is the transfer function of the Rogowski coil when 0<ζ<1.

[0076] As Figure 5 shown, when ζ>1, it includes a differential link, an oscillation link, and a proportional link. The transfer function of the oscillation link is When 0<ζ<1, it includes a differential link, a first inertia link, a second inertia link, and a proportional link. The transfer function of the first inertia link is The transfer function of the second inertia link is

[0077]

[0078] where s is the Laplace variable, K rc =-(MR a ) / (LC0).

[0079] The expression after passing the current input signal shown in Equation (3) through the Rogowski coil link can be referred to the following formula (4):

[0080]

[0081] where, s i3 =-α + jβ; s i4 =-α - jβ.

[0082] where,

[0083] where,

[0084] When ζ>1, s i1 and s i2 are unequal real numbers, K i1and K i2 are real numbers, and K i3 and K i4 are conjugate complex numbers. At this time, formula (4) is arranged as formula (5) below:

[0085]

[0086] When 0 < ζ < 1, s i1 and s i2 are conjugate complex numbers, and K i1 and K i2 are conjugate complex numbers, and K i3 and K i4 are conjugate complex numbers. Let p = ζω n , then at this time, formula (4) is arranged as formula (6) below:

[0087]

[0088] Among them, is the argument of the complex number K i3 ; is the argument of the complex number K i1 ;

[0089] Formulas (5) and (6) are the expressions for deriving the current output signal after passing through the Rogowski coil link.

[0090] The third step is to derive the voltage output signal after passing through the capacitive voltage divider.

[0091] The voltage input signal at the relay protection measurement point at the protection installation location is collected by the capacitive voltage divider. It can be seen from formula (2) that the signal input to the capacitive voltage divider consists of two parts, namely the power frequency signal and the decaying periodic signal, and both of these signals are expressed by the following formula (7):

[0092]

[0093] Among them, α is the reciprocal of the decay time constant of the input signal; when α = 0, the input signal U h (t) to the capacitive voltage divider is the power frequency signal; when α ≠ 0, the input signal U h (t) to the capacitive voltage divider is the decaying periodic signal; U m represents the amplitude of the input voltage signal.

[0094] The transmission link of the electronic voltage transformer is as Figure 6 shown, Figure 6 which is a schematic diagram of the transmission link of an electronic voltage transformer provided in an embodiment of the present invention, as Figure 6As shown, it includes a capacitive voltage divider section, an anti-aliasing filter section, an analog-to-digital conversion section, and a digital integration section.

[0095] Figure 7 is a schematic structural diagram of an equivalent circuit of a capacitive voltage divider provided by an embodiment of the present invention. As Figure 7 shown, C3 and C2 are the high-voltage arm and low-voltage arm capacitors respectively, R is a precision sampling resistor, R2 is a load resistor, u1(t) is the input primary voltage, and u2(t) is the output secondary voltage.

[0096] Figure 8 is a schematic diagram of a transfer link of a capacitive voltage divider provided by an embodiment of the present invention. The transfer link of the capacitive voltage divider includes a differentiation link, a third inertia link, and a proportional link. The transfer function of the third inertia link is Define

[0097]

[0098] where, T ev =(C3 + C2)R u , K ev =C3R u .

[0099] The time-domain form expression of the voltage output signal after passing the signal shown in formula (7) through the capacitive voltage divider section can be referred to as formula (8) below:

[0100]

[0101] where, s u1 =-1 / (C3R u +C2R u ); s u2 =-α + jβ; s u3 =-α - jβ.

[0102] where,

[0103] When K u1 is a real number, and K u2 and K u3 are conjugate complex numbers, the expression form of U ev (t) is as formula (9) below:

[0104]

[0105] where, is the argument of the complex number K u2 .

[0106] Derive the expression of the voltage output signal after passing through the capacitive voltage divider according to formula (9).

[0107] Step 4: Calculate the current output digital signal and voltage output digital signal after the anti-aliasing filter for the current output signal and voltage output signal after the Rogowski coil and capacitive voltage divider.

[0108] From the expressions of the current output signal and voltage output signal shown in Formula (5), Formula (6) and Formula (8), the sampling sequences of current and voltage at high sampling rate f s can be obtained.

[0109] The transfer function H Be (s) of the anti-aliasing filter link is as follows in Formula (10):

[0110]

[0111] Adopt the pre-corrected bilinear transformation to discretize the transfer function shown in Formula (10) at sampling rate f s . The current and voltage sampling sequences after discretizing the current output signal and voltage output signal after the Rogowski coil and capacitive voltage divider respectively are processed by the discretized anti-aliasing filter to obtain the processed current and voltage digital signals.

[0112] Step 5: Calculate the current output digital signal and voltage output digital signal after the integrator for the current output digital signal and voltage output digital signal after the anti-aliasing filter link.

[0113] The current output digital signal and voltage output digital signal output after the anti-aliasing filter link are respectively integrated by the digital integrator link, and the integrated signal is proportional to the primary signal.

[0114] The expression of the transfer function H B (z) of the digital integrator link is as follows in Formula (11):

[0115]

[0116] where k B and c B are both parameters of the digital integrator, T is the sampling interval, and z is the variable in the complex frequency domain.

[0117] After having the transfer functions of each above link, combined with Figure 2 a screening method for protection maloperation when applying an active electronic current transformer provided by an embodiment of the present invention will be introduced.

[0118] Figure 2 is a schematic structural diagram of an active electronic current transformer dynamic transfer characteristic analysis system provided by an embodiment of the present invention, as Figure 2As shown, the method for screening maloperation of the active electronic current transformer includes the following steps:

[0119] S101. Under no-load closing conditions, calculate the primary current and primary voltage at the installation location of the active electronic current transformer corresponding to different permutations and combinations of working conditions.

[0120] Among them, the permutations and combinations of different working conditions include the permutations and combinations of different line lengths and different system impedance magnitudes.

[0121] Exemplarily, the line lengths can be sorted in descending order first, and the impedances can be sorted in ascending order; then the shortest line is paired with the smallest impedance, and the primary current and primary voltage under this working condition are calculated according to the equivalent circuit diagram of no-load closing shown in Figure 1 Then the shortest length is paired with the second smallest impedance, and the primary current and primary voltage under this working condition are calculated according to the equivalent circuit diagram of no-load closing shown in

[0122] Next, the shortest length is paired with the second smallest impedance, and the primary current and primary voltage under this working condition are calculated according to the equivalent circuit diagram of no-load closing shown in Figure 1 ... until all line lengths and all impedances are paired, and the primary current and primary voltage corresponding to several groups of working conditions can be obtained.

[0123] As an alternative implementation, the permutations and combinations of different working conditions include the permutations and combinations of different line lengths, different system impedance magnitudes, different voltage levels, different line parameters, and different closing angles.

[0124] It can be understood that after those skilled in the art know the permutation and combination methods of different line lengths and different system impedance magnitudes, they can think of the permutation and combination methods when the permutations and combinations of different working conditions include the permutations and combinations of different line lengths, different system impedance magnitudes, different voltage levels, different line parameters, and different closing angles. Details are not described here. By adopting a combination permutation similar to that listed in the example, the primary current and primary voltage corresponding to several groups of working conditions are obtained.

[0125] S102. According to the transfer functions of each link of the active electronic current transformer, using the primary current and primary voltage under different working conditions as input quantities, calculate the output quantity of the active electronic current transformer.

[0126] S103. Substitute the output quantities of the active electronic current transformer corresponding to different working conditions into the protection criterion, and screen the working conditions with the criterion result of protection operation as maloperation conditions.

[0127] Among them, the protection criterion includes at least: sampled value differential protection, non-differential filtering power frequency phasor differential protection, differential filtering power frequency phasor differential protection, non-differential filtering power frequency phasor distance protection, differential filtering power frequency phasor distance protection, and differential equation distance protection.

[0128] Taking the voltage and current signals at the protection installation location during no-load closing of the circuit breaker under different voltage levels, different line parameters, different line lengths, different system impedance magnitudes, and different closing angles as inputs, the output signals of the active electronic current transformer are calculated, that is, the integrated current output digital signal and voltage output digital signal. After resampling and synchronizing the integrated current output digital signal and voltage output digital signal, they are used for protection logic discrimination, and case calculations are carried out, including sampled value differential protection, non-differential filtered power frequency phasor differential protection, differential filtered power frequency phasor differential protection, non-differential filtered power frequency phasor distance protection, differential filtered power frequency phasor distance protection, and differential equation distance protection, and the scenarios of protection maloperation are screened out.

[0129] An embodiment of a method for screening protection maloperation when applying an active electronic current transformer provided by the embodiment of the present invention calculates the primary current and primary voltage at the installation location of the active electronic current transformer corresponding to different permutations and combinations of different working conditions under no-load closing; different permutations and combinations of different working conditions include permutations and combinations of different line lengths and different system impedance magnitudes; then, according to the transfer function of each link of the active electronic current transformer, taking the primary current and primary voltage under different working conditions as input quantities, the output quantity of the active electronic current transformer is calculated; finally, the output quantities of the active electronic current transformer corresponding to different working conditions are brought into the protection criterion, and the working conditions with the criterion result of protection action are screened as maloperation conditions, so as to achieve the purpose of quickly screening the working conditions of relay protection maloperation and improve the performance and reliability of relay protection in a power electronic power system.

[0130] An embodiment of a device for screening protection maloperation when applying an active electronic current transformer:

[0131] The embodiment of the present invention provides a device for screening protection maloperation when applying an active electronic current transformer, including a processor, and the processor is used to execute a computer program to implement the method steps of the method for screening protection maloperation when applying an active electronic current transformer.

[0132] Among them, regarding the "method steps of the method for screening protection maloperation when applying an active electronic current transformer", reference can be made to the relevant expressions in the foregoing "embodiment of the method for screening protection maloperation when applying an active electronic current transformer", and details are not described herein again.

[0133] The embodiment of the present invention provides a device for screening protection maloperation when applying an active electronic current transformer, which can achieve the same beneficial effects as the foregoing method for screening protection maloperation when applying an active electronic current transformer, and details are not described herein again.

Claims

1. A screening method for protection maloperation when applying active electronic current transformers, characterized in that It includes the following steps: 1) Under no-load closing conditions, calculate the primary current and primary voltage at the installation location of the active electronic current transformer corresponding to the permutations and combinations of different operating conditions; the permutations and combinations of different operating conditions include the permutations and combinations of different line lengths and different system impedance magnitudes; 2) According to the transfer functions of each link of the active electronic current transformer, using the primary current and primary voltage under different operating conditions as input quantities, calculate the output quantity of the active electronic current transformer; 3) Substitute the output quantities of the active electronic current transformer corresponding to different operating conditions into the protection criterion, and screen the operating conditions with the criterion result of protection action as misoperation conditions.

2. The screening method for protection maloperation when applying active electronic current transformers according to claim 1, characterized in that, The permutations and combinations of different operating conditions include the permutations and combinations of different line lengths, different system impedance magnitudes, different voltage levels, different line parameters, and different closing angles.

3. The screening method for protection maloperation when applying active electronic current transformers according to claim 1, characterized in that, The active electronic current transformer includes an electronic voltage transformer and an electronic current transformer; The electronic current transformer includes a Rogowski coil link, an anti-aliasing filter link, an analog-to-digital conversion link, and a digital integration link; The electronic voltage transformer includes a capacitive voltage divider link, an anti-aliasing filter link, a mode conversion link, and a digital integration link.

4. The screening method for protection maloperation when applying active electronic current transformers according to claim 3, wherein, The expression of the primary current I after passing through the Rogowski coil section rc (t) is as follows: Among them, s i3 = -α + jβ; s i4 = -α - jβ; where t represents the time in the time domain; I m is the amplitude of the input current signal, α is the reciprocal of the decay time constant of the input signal, β is the angular frequency of the input signal, is the initial phase of the input signal, M is the equivalent mutual inductance between the induced electromotive force of the Rogowski coil and the primary current, R r is the total resistance of the coil winding and the lead, L is the inductance of the Rogowski coil, C0 is the stray capacitance of the Rogowski coil, R a is the load resistance.

5. The screening method for protection maloperation when applying active electronic current transformers according to claim 4, characterized in that The expression of the primary current I after passing through the Rogowski coil section rc (t) is related to the value of ζ; When ζ > 1, s i1 and s i2 are unequal real numbers, K i1 and K i2 are real numbers, K i3 and K i4 are conjugate complex numbers, then at this time, the expression of I rc (t) is as follows: When \(0 < \zeta < 1\), \(s\) i1 and \(s\) i2 are conjugate complex numbers, \(K\) i1 and \(K\) i2 are conjugate complex numbers, \(K\) i3 and \(K\) i4 are conjugate complex numbers. Let \(p = \zeta\omega\) n , then at this time, the expression of \(I\) rc (t) is as follows: Among them, is the argument of the complex number K i3 ; is the argument of the complex number K i1 .

6. The screening method for protection maloperation when applying active electronic current transformers according to claim 3, characterized in that After the primary voltage passes through the capacitor voltage divider section, the time-domain expression U ev (t) of the signal output by the capacitor voltage divider section is as follows: where s u1 = -1 / (C3R u + C2R u )); s u2 = -α + jβ; s u3 = -α - jβ; Among them, U m is the amplitude of the input voltage signal, α is the reciprocal of the decay time constant of the input signal, β is the angular frequency of the input signal, is the initial phase of the input signal, C3 and C2 are the capacitances of the high-voltage arm and the low-voltage arm of the capacitive voltage divider respectively, R is a precision sampling resistor, and R2 is a load resistor; At K u1 is a real number, K u2 and K u3 are conjugate complex numbers, the expression form of U ev (t) is as follows: wherein, is the argument of the complex number K u2 .

7. The screening method for protection maloperation when applying active electronic current transformers according to claim 3, characterized in that, The transfer function H Be (s) of the anti-aliasing filter section is given by the following formula: Where s is the Laplace variable.

8. The screening method for protection maloperation when applying active electronic current transformers according to claim 3, characterized in that, The transfer function H B (z) of the digital integrator section is given by the following formula: where k B and c B are both parameters of the digital integrator, T is the sampling interval, and z is a variable in the complex frequency domain.

9. The screening method for protection maloperation when applying active electronic current transformers according to any one of claims 1-8, characterized in that, The protection criterion at least includes: sampled value differential protection, non-differential filtered power frequency phasor differential protection, differential filtered power frequency phasor differential protection, non-differential filtered power frequency phasor distance protection, differential filtered power frequency phasor distance protection, and differential equation distance protection.

10. A screening device for protection maloperation when applying active electronic current transformers, including a processor, characterized in that, The processor is used to execute a computer program to implement the method steps of the method for screening protection misoperation when applying an active electronic current transformer as described in any one of claims 1-9.

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