A line protection method and device for coping with high-resistance grounding faults in power systems

Abstract

A line protection method and device for dealing with high-resistance grounding faults in an electric power system, the method comprising: calculating the instantaneous values ​​of zero-sequence voltage and current of the line according to the continuously updated instantaneous values ​​of three-phase voltage and three-phase current collected; using the line zero-sequence voltage and current, respectively calculating the sum of the absolute values ​​of zero-sequence voltage and current in one cycle (referred to as "modulus sum"); using the collected instantaneous values ​​of three-phase voltage, calculating the maximum and minimum values ​​of the modulus sum of the three-phase voltage, and the maximum value of the absolute value of the difference between the modulus sums of the phase voltages between each two phases; using the collected instantaneous values ​​of three-phase current, calculating the maximum value of the phasor value of the three-phase current, and the maximum value of the modulus sum of the three-phase current; judging whether a grounding fault occurs according to the relationship between the physical quantity and the setting value within a preset time after the fault. The present invention avoids the problem of zero-sequence overcurrent protection refusal to operate due to too small short-circuit current in a high-proportion power electronic power supply system, has high reliability, and can effectively deal with high-resistance grounding faults occurring in the electric power system.

Description

Technical Field

[0001] The present invention belongs to the field of relay protection for electric power systems, and more specifically, relates to a line protection method and device for coping with high-resistance grounding faults in electric power systems. Background Art

[0002] With the large-scale grid connection of power electronic power sources such as wind power, photovoltaic power, and energy storage, the degree of power electronicization of power systems is becoming increasingly profound. There are obvious differences in the fault characteristics of power electronic power sources and synchronous generators, which are mainly manifested in the limited short-circuit current amplitude and frequency offset. After an asymmetric fault occurs in the transmission line, when the transition resistance is large, the positive sequence and negative sequence impedances of the line are large, the zero sequence current may be very small, and the line zero sequence IV protection may fail to operate. These characteristics have brought huge challenges to traditional relay protection, and new methods are urgently needed to deal with high-resistance grounding faults.

[0003] The existing zero-sequence overcurrent IV protection is based on the traditional power system. With the access of all new energy sources to the power grid, on the one hand, when an asymmetric grounding fault occurs in the line, if the transition resistance is large, the positive-sequence and negative-sequence impedances of the line become larger, resulting in a smaller fault current. On the other hand, the power electronic power supply has the characteristics of limited short-circuit current amplitude and frequency offset, which brings great difficulties to the setting. In view of the above shortcomings, through the analysis of the fault characteristics of the access of new energy sources to the power grid and a large number of fault simulations, the weak fault identification criterion proposed in the present invention can well deal with high-resistance grounding faults, thereby realizing the accurate action of the relay protection device when a high-resistance grounding fault occurs. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide a line protection method and device for dealing with high-resistance grounding faults in power systems, aiming to solve the technical problem in the prior art that zero-sequence current IV stage protection refuses to operate under high-resistance grounding conditions.

[0005] To achieve the above object, the present invention provides a line protection method for dealing with a high-resistance grounding fault in a power system, comprising the following steps:

[0006] A line protection method for dealing with a high-resistance grounding fault in an electric power system comprises the following steps:

[0007] Step 1: Determine whether the zero-sequence current modulus and I0 are greater than the line zero-sequence overcurrent protection setting value I 0set , if the judgment result is yes, then execute the protection action, otherwise execute step 2;

[0008] Step 2: Compare the maximum value of the current phasor value modulus The maximum value of the current modulus and Get the larger value of the two max , determine the larger value Imax Is it greater than the current threshold I set If the judgment result is yes, execute step 3, otherwise the protection will not work;

[0009] Step 3: Determine whether the sum of the zero-sequence voltage modulus and U0 is greater than the zero-sequence overvoltage protection setting value U 0set , if the judgment result is yes, then execute the protection action, otherwise execute step 4;

[0010] Step 4: Determine the maximum value of the sum of the three-phase voltage moduli The maximum value of the sum of the three-phase voltage moduli

[0011] The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases And the minimum value of the sum of the three-phase voltage moduli Whether the criteria are met and protection actions are performed based on the criteria results.

[0012] Furthermore, step 4 specifically includes: if the comparison results of the criteria are respectively: If three sampling points are met continuously and there is no protection lock at this moment, the protection action flag is output, otherwise, the protection does not act. is the voltage unbalance coefficient, is the low voltage threshold coefficient, is the overvoltage threshold coefficient, U N is the rated phase voltage of the line.

[0013] Furthermore, the three-phase current phasor value The maximum value of the current phasor value modulus The calculation method is:

[0014]

[0015] Among them, i a (t), i b (t), i c (t) is the current sampling value at time t after low-pass filtering. is the value after Fourier algorithm n The current phasor value at the moment, N is the sampling frequency, and i is the imaginary unit.

[0016] Furthermore, the calculation method of the zero-sequence current modulus and I0 is:

[0017]

[0018] Among them, Δt is the sampling interval, T is the power frequency period, and i0(t) is the zero-sequence current at time t.

[0019] Furthermore, the maximum value of the current modulus and The calculation method is:

[0020]

[0021] Among them, i a (t), i b (t), i c (t) is the current sampling value at time t after low-pass filtering, Δt is the sampling interval, and T is the power frequency period.

[0022] Furthermore, the calculation method of the zero-sequence voltage modulus and U0 is:

[0023]

[0024] Among them, Δt is the sampling interval, T is the power frequency period, and u0(t) is the zero-sequence voltage sampling value at time t.

[0025] Furthermore, the maximum value of the sum of the three-phase voltage moduli is The minimum value of the sum of the three-phase voltage moduli And the maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases The calculation method is:

[0026]

[0027]

[0028]

[0029] Among them, u a (t),u b (t),u c (t) is the voltage sampling value at time t after low-pass filtering, Δt is the sampling interval, and T is the power frequency period.

[0030] A line protection device for dealing with a high-resistance grounding fault in a power system, comprising:

[0031] The first judgment module is used to judge whether the zero-sequence current modulus and I0 are greater than the line zero-sequence overcurrent protection setting value I 0set , if the judgment result is yes, the protection action is executed;

[0032] The second judgment module is used to compare the maximum value of the current phasor value modulus when the judgment result obtained by the first judgment module is no. The maximum value of the current modulus and Get the larger value of the two max , determine the larger value Imax Is it greater than the current threshold I set , if the judgment result is otherwise, the protection will not act;

[0033] The third judgment module is used to judge whether the sum of the zero-sequence voltage modulus value and U0 is greater than the zero-sequence overvoltage protection setting value U when the judgment result obtained by the second judgment module is yes, and execute the protection action if the judgment result is yes;

[0034] 0set

[0035] The fourth judgment module is used to judge the maximum value of the sum of the three-phase voltage modulus values ​​when the third judgment module obtains a judgment result of no. The maximum value of the sum of the three-phase voltage moduli The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases And the minimum value of the sum of the three-phase voltage moduli Whether the criteria are met and protection actions are performed based on the criteria results.

[0036] Furthermore, the fourth judgment module performs a protection action according to the judgment result, specifically including: if the comparison results of the judgment are respectively: If three sampling points are met continuously and there is no protection lock at this moment, the protection action flag is output, otherwise, the protection does not act. is the voltage unbalance coefficient, is the low pressure threshold coefficient, is the overvoltage threshold coefficient, U N is the rated phase voltage of the line.

[0037] A line protection system for coping with a high-resistance grounding fault in a power system, comprising:

[0038] A computer readable storage medium and a processor;

[0039] The computer-readable storage medium is used to store executable instructions;

[0040] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the line protection method for coping with high-resistance grounding faults in the power system.

[0041] A non-transitory computer-readable storage medium stores a computer program, which, when executed by a processor, implements the line protection method for coping with a high-resistance grounding fault in a power system as described above.

[0042] Compared with the prior art, the above technical scheme conceived by the present invention calculates the instantaneous values ​​of line zero-sequence voltage and current according to the collected and continuously updated instantaneous values ​​of three-phase voltage and three-phase current; uses the line zero-sequence voltage and current to respectively calculate the zero-sequence voltage and current modulus sum; uses the collected three-phase voltage instantaneous values ​​to calculate the maximum and minimum values ​​of the sum of the three-phase voltage modulus, and the maximum value of the absolute value of the difference between the sum of the phase voltage modulus between each two phases; uses the collected three-phase current instantaneous values ​​to calculate the maximum value of the three-phase current phasor value and the maximum value of the sum of the three-phase current modulus; and determines whether a ground fault occurs according to the relationship between the physical quantity and the set value within a preset time after the fault. The present invention avoids the problem of zero-sequence overcurrent protection refusal to operate due to the small short-circuit current in a high-proportion power electronic power supply system, has high reliability, and can effectively deal with high-resistance ground faults occurring in traditional power systems and all-power electronic power supply power system lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of the protection method provided by the implementation of the present invention;

[0044] Figure 2 This is a schematic diagram of the 110kV AC power transmission system of the Guangshui demonstration project provided by the present invention;

[0045] Figure 3 A phase short circuit fault occurs at 50% of the protected line in the positive direction of the first relay protection device of the 110kV AC transmission system ( Figure 2 Point f), the action diagram of the traditional relay protection device with a transition resistance of 150 ohms;

[0046] Figure 4 A phase short circuit fault occurs at 50% of the protected line in the positive direction of the first relay protection device of the 110kV AC transmission system ( Figure 2 Point f), with a transition resistor of 150 ohms, the maximum value of the three-phase current modulus and the three-phase current phasor modulus of the relay protection device of the present invention and the action diagram with current threshold;

[0047] Figure 5 A phase short circuit fault occurs at 50% of the protected line in the positive direction of the first relay protection device of the 110kV AC transmission system ( Figure 2 f), with a transition resistance of 150 ohms, the action diagram of the maximum value of the sum of the three-phase voltage moduli and the overvoltage threshold, the minimum value and the undervoltage threshold, and the quotient of the maximum value of the absolute value of the difference between the sum of the phase voltage moduli between each two phases and the maximum value of the sum of the three-phase voltage moduli and the unbalanced voltage threshold of the relay protection device of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described below in conjunction with embodiments. It should be noted that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0049] Aiming at the problem that a traditional relay protection device fails to operate when a high-resistance grounding short circuit occurs in an electric power system, the present invention provides a line protection method capable of coping with a high-resistance grounding fault in the electric power system.

[0050] like Figure 1 As shown, it is a flow chart of a line protection method for coping with a high-resistance grounding fault in a power system provided by an embodiment of the present invention. The system based on the method includes: a first equivalent power source 1, a first AC line 2, a first busbar 3, a protected AC line 4, a second busbar 5, a second AC line 6, a second equivalent power source 7, a first relay protection device 8 and a second relay protection device 9. The first equivalent power source 1 is connected to the first busbar through the first AC line 2 3, the first busbar 3 is connected to the second busbar through the protected AC line 4 5, and the second busbar 5 is connected to the second equivalent power source 7 through the second AC line 6; the first relay protection device 8 is installed at the outlet of the first busbar 3, and the second relay protection device 9 is installed at the outlet of the second busbar 5.

[0051] The method comprises the following steps:

[0052] S1. The current and voltage signals are collected in real time by the current transformer and voltage transformer at the protection installation site to obtain the continuously updated instantaneous values ​​of current and voltage, and then the values ​​are processed by the same low-pass filter;

[0053] In step S1, the current and voltage collected by the mutual inductor are instantaneous values; the passband of the low-pass filter allows a maximum attenuation of 3dB, and the stopband allows a minimum attenuation of 30dB. The passband cutoff frequency is usually selected as 300Hz, and the stopband start frequency is usually selected as 350Hz.

[0054] S2. According to the instantaneous current and voltage values ​​processed by S1, the corresponding zero-sequence voltage u0(t), zero-sequence current i0(t), and current phasor value are calculated in real time. The maximum value of the current phasor value modulus

[0055] The calculation method for the maximum value of the three-phase current phasor value and the current phasor value modulus is:

[0056]

[0057] Among them, i a (t), i b (t), i c (t) is the current sampling value at time t after low-pass filtering. is the value after Fourier algorithm n The current phasor value at the moment, N is the sampling frequency, and i is the imaginary unit.

[0058] S3. Calculate the zero-sequence current modulus and I0 for each sampling point and the data in the previous cycle, and transmit the calculation result to S4;

[0059] In step S3, the calculation method of the zero-sequence current modulus value and is:

[0060] Among them, Δt is the sampling interval, T is the power frequency period, and i0(t) is the zero-sequence current at time t.

[0061] S4. According to the zero-sequence overcurrent criterion, the zero-sequence current modulus value and I0 obtained in S3 and the line zero-sequence overcurrent protection setting value I 0set Compare and pass the result to S5;

[0062] S5. If the comparison result of S4 is I0>I 0set If the three sampling points are maintained continuously and there is no protection lock at this moment, the protection action flag is output. Otherwise, go to S6;

[0063] S6. Calculate the maximum value of the sum of the current modulus of each phase for each sampling point and the data in the previous cycle And transmit the calculation result to S7;

[0064] In step S6, the maximum value of the sum of the current modulus values ​​of each phase is calculated as follows:

[0065]

[0066] Among them, i a (t), i b (t), i c (t) is the current sampling value at time t after low-pass filtering, Δt is the sampling interval, and T is the power frequency period.

[0067] S7. Compare the maximum value of the current phasor value modulus obtained by S2 The maximum value of the current modulus and the current modulus obtained by S6 Get the larger value of the two max , and this larger value I max With current threshold I set Compare and pass the result to S8;

[0068] S8. If the comparison result of S7 is 1 max >I set And keep it continuously at three sampling points, and go to S9. Otherwise, the protection will not work;

[0069] S9. Calculate the zero-sequence voltage modulus and U0 for each sampling point and the data in the previous cycle, and transmit the calculation result to S10;

[0070] In step S9, the calculation method of the zero-sequence voltage modulus and U0 is:

[0071] Among them, Δt is the sampling interval, T is the power frequency period, and u0(t) is the zero-sequence voltage sampling value at time t.

[0072] S10. According to the zero-sequence overvoltage criterion, the zero-sequence voltage modulus value and U0 obtained in S9 and the zero-sequence overvoltage protection setting value U 0set Compare and transmit the result to S11;

[0073] S11. If the comparison result of S10 is U0>U 0set If the three sampling points are maintained continuously and there is no protection lock at this moment, the protection action flag is output. Otherwise, go to S12;

[0074] S12. Calculate the maximum value of the sum of the three-phase voltage modulus values ​​for each sampling point and the data in the previous cycle and minimum value And the maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases And transmit the calculation result to S13;

[0075] In step S12, the maximum value of the sum of the three-phase voltage moduli is The minimum value of the sum of the three-phase voltage moduli The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases The calculation method is:

[0076]

[0077]

[0078]

[0079] Among them, u a (t),u b (t),u c (t) is the voltage sampling value at time t after low-pass filtering, Δt is the sampling interval, and T is the power frequency period.

[0080] S13. The maximum value of the three-phase voltage modulus and the maximum value of S12 and line rated phase voltage U N , the maximum value of the sum of the three-phase voltage moduli The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases The minimum value of the sum of the three-phase voltage moduli and line rated phase voltage U N Compare and pass the result to S14;

[0081] S14. If the three comparison results of S13 are: If the three sampling points are met continuously and there is no protection lock at this moment, the protection action flag is output. Otherwise, the protection does not act. is the voltage unbalance coefficient, usually 0.15; is the low-pressure threshold coefficient, usually selected as 0.1; is the overvoltage threshold coefficient, usually 0.75.

[0082] In order to further illustrate the line protection method for coping with a high-resistance grounding fault in a power system provided by an embodiment of the present invention, it is now described in detail as follows in conjunction with the accompanying drawings and specific examples:

[0083] The specific implementation method is described by taking the schematic diagram of the 110kV AC power transmission system of the Guangshui demonstration project as an example. Figure 3 As shown, the 110kV AC transmission system structure of the Guangshui demonstration project includes: various new energy stations, Baolin 110kV busbar, Beihuan 110kV busbar, protected line (Baolin-Beihuan line), the first relay protection device is installed on the Baolin side of the Baolin-Beihuan line, and the second relay protection device is installed on the Beihuan side of the Baolin-Beihuan line.

[0084] Using the above system, the line protection method for high-resistance grounding fault in the power system is implemented according to the following steps:

[0085] Step 1: The current and voltage signals are collected in real time through the current transformer and voltage transformer at the protection installation site to obtain the continuously updated sampled current and voltage instantaneous values, which are then processed by the same low-pass filter;

[0086] Step 2: According to the processed current and voltage in step 1, the corresponding zero-sequence voltage u0(t), zero-sequence current i0(t), and current phasor value are calculated in real time. The maximum value of the current phasor value modulus

[0087] Step 3: For each sampling point and the data in the previous cycle, calculate the zero-sequence current modulus value and I0, and pass the calculation result to step 4;

[0088] Step 4: According to the zero-sequence overcurrent criterion, the zero-sequence current modulus value and I0 obtained in step 3 and the line zero-sequence overcurrent protection setting value I 0setCompare and pass the result to step 5;

[0089] Step 5: If the comparison result of step 4 is I0>I 0set If the three sampling points are maintained continuously and there is no protection lock at this moment, the protection action flag is output. Otherwise, go to step 6;

[0090] Step 6: For each sampling point and the data in the previous cycle, calculate the maximum value of the sum of the current modulus of each phase And pass the calculation result to step 7;

[0091] Step 7: Compare the maximum value of the current phasor value modulus obtained in step 2 The maximum value of the current modulus value and the current modulus value obtained in step 6 Get the larger value of the two max , and this larger value I max With current threshold I set Compare and pass the result to step 8;

[0092] Step 8: If the comparison result of step 7 is 1 max >I set And keep it continuously at three sampling points, go to step 9. Otherwise, the protection does not work;

[0093] Step 9: For each sampling point and the data in the previous cycle, calculate the zero-sequence voltage modulus and U0, and transmit the calculation result to S10;

[0094] Step 10: According to the zero-sequence overvoltage criterion, the zero-sequence voltage modulus value U0 and the zero-sequence overvoltage protection setting value U obtained in step 9 are calculated. 0se t is compared and the result is passed to step 11;

[0095] Step 11: If the comparison result of step 10 is U0>U 0set If the three sampling points are maintained continuously and there is no protection lock at this moment, the protection action flag is output. Otherwise, go to step 12;

[0096] Step 12: For each sampling point and the data in the previous cycle, calculate the maximum value of the sum of the three-phase voltage modulus values and minimum value And the maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases And pass the calculation result to step 13;

[0097] Step 13: Calculate the maximum value of the three-phase voltage modulus and the maximum value of the sum obtained in step 12 and line rated phase voltage U N , the maximum value of the sum of the three-phase voltage moduli The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases The minimum value of the sum of the three-phase voltage moduli and line rated phase voltage U N Compare and pass the result to step 14

[0098] Step 14: If the three comparison results of step 13 are: If the three sampling points are met continuously and there is no protection lock at this moment, the protection action flag is output. Otherwise, the protection does not act. is the voltage unbalance coefficient, take 0.15; is the low-pressure threshold coefficient, which is taken as 0.1; is the overvoltage threshold coefficient, which is taken as 0.75.

[0099] In an embodiment of the present invention, in step 1, taking the first relay protection device installed at the Baolin exit of the Baolin-Beihuan line as an example, the three-phase voltage and current of the line are taken as the instantaneous values ​​sampled by the transformer at the Baolin exit, the AC transmission line adopts the Berylon model, the filter adopts the Butterworth low-pass filter, the maximum attenuation allowed in the passband is 3dB, the cut-off frequency is 300Hz, the minimum attenuation allowed in the stopband is 30dB, and the starting frequency is 350Hz.

[0100] In the embodiment of the present invention, in step 2, the three-phase current phasor value The maximum value of the current phasor value modulus The calculation method is:

[0101]

[0102] Among them, i a (t), i b (t), i c (t) is the current sampling value at the Baolin outlet at time t after low-pass filtering. is the value after Fourier algorithm n The current phasor value at the moment, N is the sampling frequency, and i is the imaginary unit.

[0103] 1. In the embodiment of the present invention, in step 3, the method for calculating the sum of the zero-sequence current modulus values ​​is:

[0104]

[0105] Among them, Δt is the sampling interval, T is the power frequency period, and i0(t) is the zero-sequence current at time t.

[0106] In the embodiment of the present invention, in step 4, the zero-sequence overcurrent protection setting value I 0set Take 0.144kA.

[0107] In the embodiment of the present invention, in step 6, the maximum value of the sum of the modulus values ​​of each phase current is calculated as follows:

[0108]

[0109] Among them, i a (t), i b (t), i c (t) is the current sampling value at the Baolin outlet at time t after low-pass filtering, Δt is the sampling interval, which is 250μs, and T is the power frequency period of 50Hz.

[0110] In the embodiment of the present invention, in step 7, there is a current threshold I set Take 50A.

[0111] In the embodiment of the present invention, in step 9, the calculation method of the zero-sequence voltage modulus and U0 is: Among them, Δt is the sampling interval, which is 250μs, T is the power frequency period of 50Hz, and u0(t) is the zero-sequence voltage sampling value at the Baolin outlet at time t.

[0112] In the embodiment of the present invention, in step 10, the zero-sequence overvoltage protection setting value U is 0.2 times the rated phase voltage of the line.

[0113] 0set

[0114] In the embodiment of the present invention, in step 12, the maximum value of the sum of the three-phase voltage modulus values ​​is The minimum value of the sum of the three-phase voltage moduli The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases The calculation method is:

[0115]

[0116]

[0117]

[0118] Among them, u a (t),u b (t),u c (t) is the voltage sampling value at the Baolin outlet at time t after low-pass filtering, Δt is the sampling interval, which is 250μs, and T is the power frequency period of 50Hz.

[0119] In this embodiment, a fault is set at 50% of the protected line in the positive direction of the first relay protection device, that is, at the midpoint f of the Baolin-Northern Ring Line. The fault type is a phase grounding fault, and the transition resistance is 150 ohms. Since the fault is set after the midpoint of the Baolin-Northern Ring Line, the line length becomes smaller, and then the equivalent PI model is adopted. The action of the traditional relay protection device is as follows Figure 3 As shown in FIG. 1 , the sum of the line zero-sequence current modulus is less than the zero-sequence overcurrent setting value, and the sum of the zero-sequence voltage modulus is less than the zero-sequence overvoltage setting value, and the conventional relay protection device refuses to operate. The operation of the relay protection device of the present invention is shown in FIG. Figure 4-Figure 5 As shown, the maximum value of the sum of the three-phase current modulus and the three-phase current phasor modulus is greater than the current threshold, the maximum value of the sum of the three-phase voltage modulus is greater than the overvoltage threshold, the minimum value of the sum of the three-phase voltage modulus is less than the low-voltage threshold, the quotient of the maximum value of the absolute value of the difference between the sum of the phase voltage modulus between each two phases and the maximum value of the sum of the three-phase voltage modulus is greater than the unbalanced voltage threshold, and the protection is activated.

[0120] Reference Figure 3 , Figure 4 , Figure 5 , Figure 3 This is the action of the conventional relay protection device when a fault occurs at 50% of the protected line in the positive direction of the first relay protection device of the 110kV AC power transmission system of the Guangshui Demonstration Project of the present invention, i.e., at the midpoint f of the Baolin-Beihuan line, and the fault type is a phase grounding fault, and the transition resistance is 150 ohms. Figure 4-Figure 5 This is the action of the relay protection device of the present invention. Figure 3-Figure 5 It can be seen that the method provided by the embodiment of the present invention can effectively deal with a high-resistance grounding fault occurring in a line.

[0121] Another aspect of the present invention provides a line protection system for coping with a high-resistance grounding fault in an electric power system, comprising: a computer-readable storage medium and a processor;

[0122] The computer-readable storage medium is used to store executable instructions;

[0123] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the line protection method for dealing with high-resistance grounding faults in the power system described in the first aspect.

[0124] Another aspect of the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the line protection method for coping with a high-resistance grounding fault in a power system as described in the first aspect.

[0125] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0126] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0127] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0128] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modification or equivalent replacement that does not deviate from the spirit and scope of the present invention should be included in the scope of protection of the claims of the present invention.

[0130] Those skilled in the art will easily understand that the above description is only a preferred example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A line protection method for dealing with high-resistance grounding faults in a power system, characterized in that: The method comprises the following steps: Step 1: Determine whether the zero-sequence current modulus and I0 are greater than the line zero-sequence overcurrent protection setting value I 0set , if the judgment result is yes, then execute the protection action, otherwise execute step 2; Step 2: Compare the maximum value of the current phasor value modulus The maximum value of the current modulus and Get the larger value of the two max , determine the larger value I max Is it greater than the current threshold I set If the judgment result is yes, execute step 3, otherwise the protection will not work; Step 3: Determine whether the sum of the zero-sequence voltage modulus and U0 is greater than the zero-sequence overvoltage protection setting value U 0set , if the judgment result is yes, then execute the protection action, otherwise execute step 4; Step 4: Determine the maximum value of the sum of the three-phase voltage moduli The maximum value of the sum of the three-phase voltage moduli The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases And the minimum value of the sum of the three-phase voltage moduli Whether the criterion is met, and protection actions are performed according to the criterion results. Step 4 specifically includes: if the comparison results of the criteria are: If three sampling points are met continuously and there is no protection lock at this moment, the protection action flag is output, otherwise, the protection does not act. is the voltage unbalance coefficient, is the low pressure threshold coefficient, is the overvoltage threshold coefficient, U N is the rated phase voltage of the line.

2. The line protection method for coping with a high-resistance grounding fault in a power system according to claim 1, characterized in that: The maximum value of the modulus of the current phasor value The calculation method is: Among them, i a (t), i b (t), i c (t) is the current sampling value at time t after low-pass filtering. is the value after Fourier algorithm n The current phasor value at the moment, N is the sampling frequency, and i is the imaginary unit.

3. The line protection method for dealing with high-resistance grounding faults in a power system according to claim 1, characterized in that: The calculation method of the zero-sequence current modulus and I0 is: Among them, Δt is the sampling interval, T is the power frequency period, and i0(t) is the zero-sequence current at time t.

4. The line protection method for coping with a high-resistance grounding fault in a power system according to claim 1, characterized in that: The current modulus and the maximum value of The calculation method is: Among them, i a (t), i b (t), i c (t) is the current sampling value at time t after low-pass filtering, Δt is the sampling interval, and T is the power frequency period.

5. The line protection method for coping with a high-resistance grounding fault in a power system according to claim 1, characterized in that: The calculation method of the zero-sequence voltage modulus and U0 is: Among them, Δt is the sampling interval, T is the power frequency period, and u0(t) is the zero-sequence voltage sampling value at time t.

6. The line protection method for coping with a high-resistance grounding fault in a power system according to claim 1, characterized in that: The maximum value of the sum of the three-phase voltage moduli The minimum value of the sum of the three-phase voltage moduli And the maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases The calculation method is: Among them, u a (t),u b (t),u c (t) is the voltage sampling value at time t after low-pass filtering, Δt is the sampling interval, and T is the power frequency period.

7. A line protection device for dealing with high-resistance grounding faults in a power system, characterized in that: include: The first judgment module is used to judge whether the zero-sequence current modulus and I0 are greater than the line zero-sequence overcurrent protection setting value I 0set , if the judgment result is yes, the protection action is executed; The second judgment module is used to compare the maximum value of the current phasor value modulus when the judgment result obtained by the first judgment module is no. The maximum value of the current modulus and Get the larger value of the two max , determine the larger value I max Is it greater than the current threshold I set , if the judgment result is otherwise, the protection will not act; The third judgment module is used to judge whether the sum of the zero-sequence voltage modulus and U0 is greater than the zero-sequence overvoltage protection setting value U0 when the judgment result obtained by the second judgment module is yes. 0set , if the judgment result is yes, the protection action is executed; The fourth judgment module is used to judge the maximum value of the sum of the three-phase voltage modulus values ​​when the third judgment module obtains a judgment result of no. The maximum value of the sum of the three-phase voltage moduli The maximum absolute value of the difference between the phase voltage modulus and the phase voltage modulus between each two phases And the minimum value of the sum of the three-phase voltage moduli Whether the criterion is met, and protection actions are performed according to the criterion results. The fourth judgment module performs a protection action according to the judgment result, specifically including: if the comparison results of the judgment are respectively: If three sampling points are met continuously and there is no protection lock at this moment, the protection action flag is output, otherwise, the protection does not act. is the voltage unbalance coefficient, is the low pressure threshold coefficient, is the overvoltage threshold coefficient, U N is the rated phase voltage of the line.

8. A line protection system for dealing with high-resistance grounding faults in a power system, characterized in that: include: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium and execute the line protection method for dealing with high-resistance grounding faults in the power system according to any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the line protection method for coping with a high-resistance grounding fault in a power system as claimed in any one of claims 1 to 6 is implemented.

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