A 10kV overhead line phase-to-phase fault differential protection method, device and medium

Abstract

This invention discloses a method, equipment, and medium for differential protection of phase-to-phase faults on 10kV overhead lines, relating to the field of power protection technology. The method includes: quantifying the instantaneous waveforms of three-phase current and voltage to obtain discrete sequences; obtaining the line current and line voltage change waveforms through point-by-point differential analysis; detecting the power direction angle offset using cross-phase detection; determining the fault direction by combining the initial polarity of the current jump; latching the trigger differential judgment start signal for a positive-direction fault; nonlinearly mapping the fault phase current with the transient characteristic duration to obtain a fault level coefficient; performing interval matching of the fault level coefficient based on a preset action delay level library; starting a delay timer according to the matched delay level; and performing a tripping operation after the delay timer expires to disconnect the faulty section of the overhead line. This invention improves the efficiency of fault isolation and achieves accurate graded protection and rapid section clearing for phase-to-phase faults on 10kV overhead lines.

Description

Technical Field

[0001] This invention relates to the field of power protection technology, and in particular to a method, equipment and medium for differential protection against phase-to-phase faults on 10kV overhead lines. Background Technology

[0002] With the continuous improvement of distribution network automation, 10kV overhead lines, as the main body of urban and rural power supply networks, have made the speed and selectivity of their fault protection a core indicator for measuring power supply reliability. In existing methods, protection mechanisms for phase-to-phase faults mainly rely on the feature extraction of steady-state electrical quantities. Mainstream solutions typically employ overcurrent protection combined with reclosing strategies. This involves calculating the amplitude of the fundamental frequency current and the phase of the voltage after a fault occurs, and then using algorithms such as Fourier transform and wavelet transform to filter out harmonic interference, thereby achieving fault location. Furthermore, to coordinate the protection actions of upstream and downstream lines, the industry commonly adopts a tiered coordination technique. This involves setting a stepped fixed delay window to ensure that circuit breakers closer to the power source operate later than those at the load end, thus avoiding cascading tripping.

[0003] However, existing phase-to-phase fault protection schemes generally adopt fixed-delay differential protection logic, which does not achieve dynamic adaptation of delay based on the actual severity of the fault and transient change characteristics. The speed and accuracy of fault isolation cannot be optimized in a coordinated manner. This can easily lead to the expansion of the fault impact range due to the lag in fault clearing, and may also result in protection maloperation or failure to operate. It is impossible to achieve rapid and accurate clearing of fault sections, making it difficult to ensure the stable and reliable operation of the distribution network. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a method for differential protection of phase-to-phase faults on 10kV overhead lines to solve the problem that it is difficult to achieve accurate graded protection and rapid section isolation of phase-to-phase faults on 10kV overhead lines.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a method for differential protection against phase-to-phase faults in a 10kV overhead line, comprising,

[0008] The instantaneous waveforms of the three-phase current and the three-phase voltage at monitoring points on the overhead line are quantized at equal intervals to obtain the discrete current sequence and discrete voltage sequence of the overhead line.

[0009] By performing point-by-point difference on the current discrete sequence and the voltage discrete sequence respectively, the line current change waveform and the line voltage change waveform of the overhead line are obtained;

[0010] The cross-phase detection is performed between the line current change waveform and the line voltage change waveform of the overhead line to obtain the power direction angle offset of the overhead line, and the initial polarity of the current jump is read from the starting point of the line current change waveform of the overhead line.

[0011] The power direction angle offset and the initial polarity of the current jump are compared to determine whether they are the same or different, and the fault direction label of the overhead line is obtained.

[0012] When the fault direction label is a positive fault, the fault direction label is written into the status register for latching and triggering to obtain the differential judgment start signal of the overhead line.

[0013] After receiving the differential judgment start signal, the fault phase current in the current discrete sequence is nonlinearly mapped to the transient characteristic duration in the initial polarity of the current jump to obtain the fault level coefficient of the overhead line.

[0014] Based on a preset action delay level library, the fault level coefficient is matched within a range, and a delay timer is started according to the matched delay level. After the delay timer expires, a tripping operation is performed to disconnect the fault section of the overhead line.

[0015] As a preferred embodiment of the phase-to-phase fault differential protection method for 10kV overhead lines described in this invention, wherein:

[0016] Preferably, the process of obtaining the discrete current sequence and discrete voltage sequence of the overhead line is as follows:

[0017] The instantaneous waveforms of three-phase current and three-phase voltage at monitoring points on the overhead line were collected;

[0018] The instantaneous waveforms of the three-phase current and the three-phase voltage are digitally sampled to obtain the current sampling sequence and voltage sampling sequence of the overhead line.

[0019] High-frequency noise components in the current sampling sequence and the voltage sampling sequence are filtered out to obtain a smoothed current sampling sequence and a smoothed voltage sampling sequence for the overhead line.

[0020] According to a preset fixed time interval, the smoothed current sampling sequence and the smoothed voltage sampling sequence are truncated with a fixed step size to obtain the current discrete sequence and voltage discrete sequence of the overhead line.

[0021] Preferably, the process of obtaining the line current change waveform and line voltage change waveform of the overhead line is as follows:

[0022] Simultaneously perform sliding window steady-state detection on the current discrete sequence and the voltage discrete sequence to obtain the current steady-state reference point and voltage steady-state reference point of the overhead line;

[0023] Using the sampling value corresponding to the current steady-state reference point as the current dynamic reference value, the digital values ​​of each subsequent sampling point in the current discrete sequence are subtracted one by one from the most recent current dynamic reference value to obtain the current change increment sequence of the overhead line.

[0024] Using the sampled value corresponding to the steady-state voltage reference point as the voltage dynamic reference value, the digital values ​​of each subsequent sampled point in the voltage discrete sequence are subtracted one by one from the most recent voltage dynamic reference value to obtain the voltage change increment sequence of the overhead line.

[0025] Abrupt edge locking is performed on the current change increment sequence and the voltage change increment sequence respectively to obtain the current abrupt change waveform unit and the voltage abrupt change waveform unit of the overhead line;

[0026] The peak amplitudes in the current change waveform unit are time-sequentially arranged to obtain the line current change waveform of the overhead line, and the peak amplitudes in the voltage change waveform unit are time-sequentially reconstructed to obtain the line voltage change waveform of the overhead line.

[0027] Preferably, the process of obtaining the power direction angle offset of the overhead line is as follows:

[0028] Based on a preset noise threshold, the abrupt leading edge of the line current change waveform of the overhead line is captured to obtain the arrival time of the current abrupt change in the line current change waveform of the overhead line.

[0029] Extract the first abrupt change start point in the line voltage change waveform where the amplitude exceeds the noise threshold, and use the absolute time scale corresponding to the abrupt change start point as the arrival time of the voltage abrupt change in the line voltage change waveform;

[0030] The time offset between the arrival times of the current surge and the voltage surge is obtained by taking the difference between the arrival times of the current surge and the arrival times of the voltage surge.

[0031] Obtain the per-unit value of the power frequency angular velocity corresponding to the rated frequency of the overhead line, and divide the time offset by the fixed time interval to obtain the phase offset multiple of the overhead line. Then multiply the phase offset multiple by the per-unit value of the power frequency angular velocity to obtain the power direction angle offset of the overhead line.

[0032] Preferably, the process of obtaining the fault direction label of the overhead line is as follows:

[0033] The power direction angle offset is subjected to direction position identification to obtain the polarity direction identifier of the power direction angle offset;

[0034] The initial polarity of the current jump is identified by the jump direction to obtain the current polarity identifier of the initial polarity of the current jump;

[0035] When the sign bit of the polarity direction indicator is the same as that of the current polarity indicator, it is determined that the polarities are the same; when the sign bit of the polarity direction indicator is opposite to that of the current polarity indicator, it is determined that the polarities are different.

[0036] When it is determined that the polarity is the same and the absolute value of the power direction angle offset falls within the preset effective action range, the positive direction fault label of the overhead line is output.

[0037] When the polarity is determined to be opposite, the fault tag in the opposite direction of the overhead line is output;

[0038] When it is determined that the polarity is the same and the absolute value of the power direction angle offset does not fall within the effective operating range, the reverse direction fault tag of the overhead line is output.

[0039] Preferably, the process of obtaining the differential judgment start signal for the overhead line is as follows:

[0040] If the direction identifier bit in the fault direction label is a positive direction fault, then the fault direction latch bit pre-allocated in the location status register corresponds to the current monitoring section of the overhead line.

[0041] Write the positive direction fault status value in the fault direction label into the fault direction latch bit to update the current value of the status register;

[0042] Based on the updated status register, the hardware latching logic corresponding to the status register is triggered to hold the positive direction fault status value in the fault direction latch bit and generate the latching completion identifier of the status register.

[0043] The latch completion flag is mapped to a state to obtain the differential judgment start signal for the overhead line.

[0044] Preferably, the process of obtaining the fault level coefficient of the overhead line is as follows:

[0045] When the grade difference judgment start signal is received, the hardware trigger circuit responds to the grade difference judgment start signal and outputs a high-level enable signal to activate the fault phase screening circuit.

[0046] The fault phase screening circuit extracts the current sampling value of the fault phase from the current discrete sequence according to the hardware trigger signal, so as to obtain the fault phase current sequence of the current discrete sequence.

[0047] Read the transient characteristic duration in the initial polarity of the current jump, and take the starting point of the sudden change as the time zero point to extract the transient current subsequence in the fault phase current sequence that is located within the transient characteristic duration;

[0048] The time interval of the timestamp of the sampled value in the transient current subsequence and the time distance of the initial abrupt change point are tuned to obtain the attenuation weight sequence corresponding to the transient current subsequence;

[0049] The absolute value of the sampled value in the transient current subsequence is weighted and superimposed with the weight at the corresponding position in the attenuation weight sequence to obtain the weighted cumulative total of the overhead line;

[0050] The weighted cumulative total is compared with a preset level threshold range to make a threshold decision, thereby obtaining the fault level coefficient of the overhead line.

[0051] Preferably, the process of disconnecting the faulty section of the overhead line is as follows:

[0052] The fault level coefficient is mapped to a preset action delay level library, the numerical range in which the fault level coefficient falls is located, and the delay level corresponding to the numerical range is extracted.

[0053] Based on the delay level, the corresponding delay length value is extracted from the action delay level library, and the delay length value is loaded into the delay counter to start the decrementing counting process of the delay counter;

[0054] Monitor the current count value of the delay counter. When the current count value decreases to zero, determine that the delay timer has ended and set the trip enable flag of the fault section in the overhead line.

[0055] The hardware trip execution circuit monitors the level of the trip enable flag in real time. When the trip enable flag is detected to be at a valid high level, the hardware trip execution circuit responds to the trip enable flag signal and outputs a stable drive level signal that meets the circuit breaker operation requirements to the circuit breaker operating mechanism corresponding to the fault section. This triggers the internal tripping structure of the circuit breaker operating mechanism to perform the tripping action and disconnect the fault section of the overhead line.

[0056] In a second aspect, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein when the computer program is executed by the processor, it implements any step of the method for differential protection of phase-to-phase faults in a 10kV overhead line as described in the first aspect of the present invention.

[0057] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, it implements any step of the method for differential protection of phase-to-phase faults in a 10kV overhead line as described in the first aspect of the present invention.

[0058] The beneficial effects of this invention are as follows: By quantifying, discretizing, and performing point-by-point differential processing on the instantaneous waveforms of the three-phase current and voltage of a 10kV overhead line, the waveforms of line current and line voltage changes can be accurately extracted. Combined with cross-phase detection to obtain the power direction angle offset, and with the initial polarity of the current jump, the fault direction can be accurately determined. It can reliably latch the positive-direction fault state and trigger the differential judgment process, ensuring the accuracy of fault identification and the stability of action triggering from the source. By performing a nonlinear mapping between the fault phase current and the transient characteristic duration to obtain the fault level coefficient, the actual severity of the fault can be accurately quantified. Then, by interval matching with a preset action delay level library, the protection delay is highly adapted to the fault state, thoroughly realizing accurate fault classification and ensuring that the protection action accurately targets the fault section, eliminating the operational risks caused by protection action deviation.

[0059] This invention performs a tripping operation after timing based on a matched delay level, enabling rapid disconnection of the faulty section and significantly improving the isolation efficiency of phase-to-phase faults on 10kV overhead lines, achieving rapid and accurate fault handling. Leveraging the technical advantages of precise graded protection and rapid section isolation, this invention comprehensively optimizes the overall performance of phase-to-phase fault protection for overhead lines, effectively shortening fault handling time, reducing the continuous impact of faults on line operation, and significantly improving the stability and security of 10kV overhead line power supply. Simultaneously, the entire protection logic is implemented using digital processing and hardware latching logic, improving the response speed and operational reliability of the protection device, providing a solid technical guarantee for the safe and stable operation of the distribution network, and making 10kV overhead line fault protection more efficient, accurate, and reliable. Attached Figure Description

[0060] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 This is a flowchart of a phase-to-phase fault differential protection method for 10kV overhead lines.

[0062] Figure 2 A flowchart for generating discrete current and voltage sequences and linear change waveforms.

[0063] Figure 3 Flowchart for fault direction determination and differential start signal generation.

[0064] Figure 4 This is a flowchart for calculating the fault level coefficient and executing the delayed trip. Detailed Implementation

[0065] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0066] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0067] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0068] Reference Figures 1-4 As one embodiment of the present invention, this embodiment provides a method for differential protection against phase-to-phase faults on a 10kV overhead line, comprising the following steps:

[0069] The instantaneous waveforms of the three-phase current and the three-phase voltage at monitoring points on the overhead line are quantized at equal intervals to obtain the discrete current sequence and discrete voltage sequence of the overhead line.

[0070] In this embodiment of the invention, the process of obtaining the discrete current sequence and discrete voltage sequence of the overhead line is as follows:

[0071] The instantaneous waveforms of three-phase current and three-phase voltage at monitoring points on the overhead line were collected;

[0072] The instantaneous waveforms of the three-phase current and the three-phase voltage are digitally sampled to obtain the current sampling sequence and voltage sampling sequence of the overhead line.

[0073] High-frequency noise components in the current sampling sequence and voltage sampling sequence are filtered out to obtain the smoothed current sampling sequence and smoothed voltage sampling sequence of the overhead line.

[0074] Based on a preset fixed time interval, the smoothed current sampling sequence and the smoothed voltage sampling sequence are truncated with a fixed step size to obtain the discrete current sequence and discrete voltage sequence of the overhead line.

[0075] The preset monitoring locations for 10kV overhead lines are determined based on line segment nodes, branch nodes, and sections with high incidence of phase-to-phase faults. These monitoring locations are key points where the characteristics of electrical quantity changes are most easily collected. Rogowski coils adapted to the 10kV voltage level are installed at the monitoring locations as dedicated current sensing devices, and capacitive voltage dividers adapted to the 10kV voltage level are installed as dedicated voltage sensing devices. Both types of sensing devices are laid close to the line conductors to continuously sense the continuous changes in the three-phase current and three-phase voltage during line operation, and to fully acquire the instantaneous waveforms of the three-phase current and three-phase voltage at the monitoring points.

[0076] The preset sampling frequency is based on the rated power frequency of 50 Hz for 10kV overhead lines, and is determined to be 10 kHz according to the Nyquist theorem of electrical quantity sampling. Continuous numerical acquisition of the instantaneous waveforms of the three-phase current is carried out according to the sampling frequency, and the continuous current waveforms are converted into a set of values ​​arranged in chronological order. The set of values ​​is the current sampling sequence of the overhead line. Continuous numerical acquisition of the instantaneous waveforms of the three-phase voltage is carried out according to the same sampling frequency of 10 kHz, and the continuous voltage waveforms are converted into a set of values ​​arranged in chronological order. The set of values ​​is the voltage sampling sequence of the overhead line.

[0077] Based on the fact that the highest effective electrical quantity generated by the normal operation and phase-to-phase fault of a 10kV overhead line is 2 kHz, a high-frequency limit is determined. Values ​​exceeding 2 kHz are judged as high-frequency noise. A passive low-pass filter circuit is used as a dedicated filter device to process the current sampling sequence. The passive low-pass filter circuit only allows values ​​below 2 kHz to pass through, blocks interference values ​​above 2 kHz, and retains the effective values ​​that reflect the true changes in the line current. After processing, a smoothed current sampling sequence of the overhead line is obtained. The same passive low-pass filter circuit is used to process the voltage sampling sequence, blocking interference values ​​above 2 kHz and retaining the effective values ​​that reflect the true changes in the line voltage. After processing, a smoothed voltage sampling sequence of the overhead line is obtained.

[0078] The pre-set fixed time interval is determined to be 0.1 milliseconds based on the shortest duration of the transient process of phase-to-phase fault in a 10kV overhead line. The numerical extraction node is determined based on the fixed time interval. The smoothed current sampling sequence is extracted with equal length according to the node, and the values ​​outside the extraction range are removed to obtain a regular discrete current sequence of the overhead line. The same fixed time interval of 0.1 milliseconds is used to determine the numerical extraction node. The smoothed voltage sampling sequence is extracted with equal length according to the node, and the values ​​outside the extraction range are removed to obtain a regular discrete voltage sequence of the overhead line.

[0079] The beneficial effects are that by completing the entire process based on clear field and electrical parameters, it is possible to obtain current discrete sequences and voltage discrete sequences that are free of high-frequency noise, have regular timing, and complete characteristics. This provides accurate and reliable basic data for subsequent fault direction identification, fault level calculation, and level difference protection core operations, ensuring the execution accuracy and operational stability of the entire phase-to-phase fault level difference protection process from the data source.

[0080] By performing point-by-point difference on the current discrete sequence and the voltage discrete sequence respectively, the waveforms of line current change and line voltage change of the overhead line are obtained.

[0081] In this embodiment of the invention, the process of obtaining the waveforms of line current change and line voltage change of the overhead line is as follows:

[0082] Simultaneously perform sliding window steady-state detection on the current discrete sequence and voltage discrete sequence to obtain the current steady-state reference point and voltage steady-state reference point of the overhead line;

[0083] Using the sampled value corresponding to the current steady-state reference point as the current dynamic reference value, the digital values ​​of each subsequent sampled point in the current discrete sequence are subtracted from the most recent current dynamic reference value to obtain the current change increment sequence of the overhead line.

[0084] Using the sampled value corresponding to the steady-state voltage reference point as the voltage dynamic reference value, the digital values ​​of each subsequent sampled point in the voltage discrete sequence are subtracted from the most recent voltage dynamic reference value to obtain the voltage change increment sequence of the overhead line.

[0085] Abrupt edge locking is performed on the current change increment sequence and the voltage change increment sequence respectively to obtain the current change waveform unit and the voltage change waveform unit of the overhead line.

[0086] The peak amplitudes in the current change waveform unit are time-sequentially arranged to obtain the line current change waveform of the overhead line, and the peak amplitudes in the voltage change waveform unit are time-sequentially reconstructed to obtain the line voltage change waveform of the overhead line.

[0087] The length of the sliding window is determined based on the electrical quantity stability characteristics within the power frequency cycle of a 10kV overhead line, and is the length of ten consecutive sampling points. The steady-state judgment criterion is that the numerical fluctuation amplitude of all sampling points within the window does not exceed one percent of the line's rated current or rated voltage. The current discrete sequence and voltage discrete sequence are simultaneously traversed and detected segment by segment according to the sliding window. The sampling point at the center of the window that meets the steady-state judgment criterion is the steady-state reference point of the corresponding sequence. Thus, the steady-state reference points of the current and voltage of the overhead line are obtained.

[0088] First, extract the sampling values ​​corresponding to the steady-state current reference point and use the sampling values ​​as the current dynamic reference values. Starting from the first sampling point after the steady-state current reference point, subtract the digital value of each subsequent sampling point in the current discrete sequence from the current dynamic reference value closest to the current sampling point. Combine all the results of the subtraction operations in chronological order to form a complete set of values. The complete set of values ​​is the current change increment sequence of the overhead line.

[0089] First, extract the sampled values ​​corresponding to the steady-state voltage reference point and use the sampled values ​​as the voltage dynamic reference value. Starting from the first sampled point after the steady-state voltage reference point, subtract the digital value of each subsequent sampled point in the voltage discrete sequence from the voltage dynamic reference value closest to the current sampled point. Combine all the results of the subtraction operations in chronological order to form a complete set of values. The complete set of values ​​is the voltage change increment sequence of the overhead line.

[0090] The criteria for determining the edge of a sudden change are the minimum characteristic value of the electrical quantity change when a phase-to-phase fault occurs on a 10kV overhead line, i.e., the change increment value exceeds 5% of the line's rated current or rated voltage. The current change increment sequence and the voltage change increment sequence are traversed separately, and the first value point that reaches the criterion is locked as the starting edge of the sudden change, and the last value point that falls back below the criterion is locked as the ending edge of the sudden change. All value combinations between the starting edge and the ending edge form the current change waveform unit and the voltage change waveform unit of the overhead line, respectively.

[0091] The peak amplitude corresponding to each time node in the current change waveform unit is extracted one by one. These peak amplitudes are arranged in chronological order of occurrence. The waveform data formed after the arrangement is completed is the line current change waveform of the overhead line. The peak amplitude corresponding to each time node in the voltage change waveform unit is extracted one by one. These peak amplitudes are rearranged in the original time order. The waveform data formed after the arrangement is completed is the line voltage change waveform of the overhead line.

[0092] The beneficial effects are that, based on clear steady-state judgment and sudden change locking criteria, steady-state electrical quantity interference can be accurately stripped and fault transient change characteristics can be completely extracted, generating standardized and uniform line current change waveforms and line voltage change waveforms for overhead lines. This provides real and reliable basic waveform data for subsequent cross-phase detection and fault direction identification, effectively improving the accuracy and reliability of differential protection discrimination.

[0093] Cross-phase detection is performed on the waveform of line current change and the waveform of line voltage change of overhead line to obtain the power direction angle offset of overhead line, and the initial polarity of current jump is read from the starting point of the abrupt change of the waveform of line current change of overhead line.

[0094] In this embodiment of the invention, the process of obtaining the power direction angle offset of the overhead line is as follows:

[0095] Based on a preset noise threshold, the abrupt leading edge of the line current change waveform of the overhead line is captured to obtain the arrival time of the current abrupt change in the line current change waveform of the overhead line.

[0096] Extract the first abrupt change point in the line voltage change waveform where the amplitude exceeds the noise threshold, and use the absolute time scale corresponding to the abrupt change point as the arrival time of the voltage abrupt change in the line voltage change waveform.

[0097] The time offset between the arrival times of the current change and the voltage change is obtained by taking the difference between the arrival times of the current change and the arrival times of the voltage change.

[0098] Obtain the per-unit value of the power frequency angular velocity corresponding to the rated frequency of the overhead line, and perform a division operation between the time offset and the fixed time interval to obtain the phase offset multiple of the overhead line. Then, multiply the phase offset multiple with the per-unit value of the power frequency angular velocity to obtain the power direction angular offset of the overhead line.

[0099] The preset noise threshold is determined based on the maximum amplitude of the background noise of electrical quantities under normal operation of a 10kV overhead line. The maximum amplitude is 0.5% of the rated current of the line. All data points of the line current change waveform of the overhead line are traversed one by one. The first data point whose amplitude exceeds the noise threshold is located, and the time information corresponding to the current data point is recorded. The current time information is the arrival time of the current change waveform of the overhead line.

[0100] The entire data point of the line voltage change waveform is iterated through one by one. The first data point whose amplitude exceeds the preset noise threshold is selected as the starting point of the change. The absolute time scale information corresponding to the starting point of the change is retrieved and the absolute time scale information is directly determined as the arrival time of the voltage change in the line voltage change waveform.

[0101] Extract the specific time value corresponding to the arrival time of the current change and the specific time value corresponding to the arrival time of the voltage change. Subtract the larger time value from the smaller time value and calculate the time difference, which is the time offset between the arrival times of the current change and the voltage change.

[0102] The rated frequency of a 10kV overhead line is 50 Hz. The per-unit value of the power frequency angular velocity corresponding to this rated frequency is determined based on the standard angular characteristics of the power frequency cycle. The time offset is divided by the previously set fixed time interval according to its magnitude. The calculated result is the phase offset multiple of the overhead line. The phase offset multiple is multiplied by the per-unit value of the power frequency angular velocity according to its magnitude. The final result is the power direction angular offset of the overhead line.

[0103] Locate the first abrupt change point in the waveform of the line current change of the overhead line where the amplitude exceeds the preset noise threshold, and read the positive or negative attribute of the current value corresponding to the initial abrupt change point. The positive or negative attribute is the initial polarity of the current jump in the waveform of the line current change of the overhead line.

[0104] Ideally, by establishing clear noise thresholds and electrical parameter calculation criteria, the system can accurately capture the moment of fault abrupt change and calculate the power direction angle offset. Simultaneously, it can accurately obtain the initial polarity of the current jump, providing accurate and stable phase and polarity data for subsequent fault direction determination, thereby effectively improving the accuracy and reliability of the fault direction determination process.

[0105] The power direction angle offset and the initial polarity of the current jump are used to determine whether they are the same or different, and the fault direction label of the overhead line is obtained.

[0106] In this embodiment of the invention, the process of obtaining the fault direction label of the overhead line is as follows:

[0107] The direction position of the power direction angle offset is identified to obtain the polarity direction mark of the power direction angle offset.

[0108] The initial polarity of the current jump is identified by the direction of the jump, so as to obtain the current polarity identifier of the initial polarity of the current jump;

[0109] When the sign bit of the polarity direction indicator is the same as that of the current polarity indicator, they are determined to be the same polarity; when the sign bit of the polarity direction indicator is opposite to that of the current polarity indicator, they are determined to be different polarities.

[0110] When it is determined that the polarity is the same and the absolute value of the power direction angle offset falls within the preset effective operating range, the positive direction fault label of the overhead line is output.

[0111] When the polarity is determined to be opposite, the fault tag in the opposite direction of the overhead line is output.

[0112] When the polarity is determined to be the same and the absolute value of the power direction angle offset does not fall within the effective operating range, the reverse direction fault label of the overhead line is output.

[0113] The complete calculated value of the power direction angle offset is read by the hardware numerical discrimination circuit. The direction position is identified based on the phase sign characteristics corresponding to the positive direction of the phase-to-phase fault of the 10kV overhead line. When the discrimination circuit determines that the value is greater than zero, it outputs a positive sign mark. When the value determines that the value is less than zero, it outputs a negative sign mark. The negative sign mark is the polarity direction indicator of the power direction angle offset.

[0114] The initial polarity value of the current jump at the starting point of the line current change waveform of the overhead line is read by the hardware polarity detection circuit. The jump direction is identified based on the numerical attribute of the fault current change of the 10kV overhead line. When the detection circuit determines that the value is positive, a positive polarity mark is generated. When the value is negative, a negative polarity mark is generated. The negative polarity mark is the current polarity identifier of the initial polarity of the current jump.

[0115] The hardware logic extraction circuit obtains the sign bit corresponding to the polarity direction indicator and the sign bit corresponding to the current polarity indicator respectively. The two sign bits are sent to the sign comparison circuit for direct comparison. When the circuit recognizes that the two sign bits are the same direction, it outputs the polarity same judgment result. When it recognizes that the two sign bits are different direction, it outputs the polarity different judgment result.

[0116] The preset effective operating range is based on the standard phase range of the positive direction of the phase-to-phase fault of the 10kV overhead line and is fixed in the hardware range determination circuit. The effective operating range is the effective characteristic range of the positive direction fault phase. The absolute value of the power direction angle offset is sent to the range determination circuit for verification. When the symbol comparison circuit outputs the same polarity and the absolute value falls within the effective operating range, the fault tag output circuit outputs the positive direction fault tag of the overhead line.

[0117] To further clarify, the standard phase range is quantified through electromagnetic transient simulation and statistical analysis of on-site fault recording data. The power direction angle offset distribution of positive-direction phase-to-phase faults is statistically analyzed; metallic short circuits are concentrated in the range of [-75°, +105°], extending to [-60°, +120°] via a 20% transition resistance grounding. After taking a safety margin, the effective operating range is fixed as a closed interval of [-120°, +120°], with a lower threshold of -120° and an upper threshold of +120°.

[0118] The polarity difference result output by the symbol comparison circuit is directly transmitted to the fault tag output circuit. After receiving the polarity difference result, the circuit immediately triggers the output command and outputs the fault tag in the opposite direction of the overhead line.

[0119] The polarity matching result of the symbol comparison circuit and the non-falling result of the interval determination circuit are simultaneously transmitted to the integrated discrimination circuit. After the circuit confirms that both conditions are met at the same time, it sends a command to the fault tag output circuit to output the fault tag in the opposite direction of the overhead line.

[0120] Preferably, based on the hardware circuit, the entire process of concrete discrimination operation is realized. The fault direction is accurately determined by fixed symbol discrimination logic and standard effective action range. The fault label in the positive or negative direction is stably output, providing a reliable directional basis for the start of differential discrimination, completely avoiding misjudgment of fault direction, and greatly improving the accuracy and stability of phase-to-phase fault direction identification of 10kV overhead lines.

[0121] When the fault direction label is a positive fault, the fault direction label is written into the status register for latching and triggering to obtain the differential judgment start signal for the overhead line.

[0122] In this embodiment of the invention, the process of obtaining the differential judgment start signal for overhead lines is as follows:

[0123] If the direction identifier bit in the fault direction label is a positive direction fault, then the fault direction latch bit pre-allocated in the location status register corresponds to the current monitoring section of the overhead line.

[0124] Write the positive direction fault status value in the fault direction label to the fault direction latch bit to update the current value of the status register;

[0125] Based on the updated status register, the hardware latching logic corresponding to the status register is triggered to keep the positive fault status value in the fault direction latch bit and generate the latching completion flag of the status register.

[0126] The latch completion flag is mapped to a state to obtain the differential judgment start signal for the overhead line.

[0127] The hardware level recognition circuit continuously reads the direction identifier signal output by the fault direction tag in real time. For a positive direction fault on a 10kV overhead line, a fixed high-level valid identifier is preset. During hardware layout, the status register is allocated a dedicated fault direction latch bit for each segment according to the total number of independent monitoring segments of the line. Each fault direction latch bit is bound to the physical address of the current monitoring segment. After the level recognition circuit detects that the direction identifier bit is a fixed high-level signal corresponding to a positive direction fault, it immediately sends a segment location command to the hardware address decoding circuit. The address decoding circuit accurately addresses and locates the fault direction latch bit that perfectly matches the current monitoring segment based on the physical address signal of the current monitoring segment.

[0128] The positive direction fault status value inside the fault direction label is set to a fixed hardware logic high-level signal. After the hardware data write drive circuit receives the positioning completion instruction, it transmits the logic high-level signal stably to the fault direction latch bit that has been located according to the fixed hardware write timing. After the fault direction latch bit receives the level signal, it immediately completes the update of the internal storage status. The current value of all storage units inside the status register is synchronously refreshed to the exclusive status corresponding to the positive direction fault, ensuring that the register status is completely consistent with the fault direction information.

[0129] The status register integrates a dedicated hardware self-locking latching logic circuit. This circuit automatically triggers the latching action the instant it detects that the status register has completed a value update. The latching logic circuit continuously outputs a constant holding level to the storage cell of the fault-direction latch bit, completely blocking the influence of external interference signals on the latch bit state. This ensures that the positive fault state value is permanently and stably retained in the fault-direction latch bit until the fault is reset. After the latching logic circuit completes the stable holding action and confirms that the state has not changed, it outputs a dedicated fixed-level signal, which serves as the latching completion indicator for the status register.

[0130] The latch completion indicator is output to the outside in the form of a stable hardware level signal. After receiving the stable hardware level signal, the hardware state transition mapping circuit converts the stable hardware level signal into a control enable signal with a dedicated trigger function according to the preset level conversion rules. The control enable signal is specifically used to activate the subsequent fault level coefficient calculation and level difference discrimination process. The control enable signal generated after conversion is the level difference discrimination start signal for overhead lines.

[0131] To further explain, the level conversion rule refers to the hardware state transition mapping circuit mapping the high and low level signals of the latch completion flag to control enable signals according to a fixed correspondence. Specifically, when the latch completion flag is high, the control enable signal outputs a high level; when the latch completion flag is low, the control enable signal outputs a low level. The mapping process is implemented by hardware logic, ensuring a one-to-one correspondence between the latch state and the control enable signal, unaffected by external interference, thereby reliably activating the subsequent fault level coefficient calculation and level difference discrimination process, and guaranteeing the stability and triggering accuracy of the level difference discrimination start signal.

[0132] Preferably, through precise coordinated operation of the entire link hardware circuit, the location, writing, self-locking and signal mapping conversion of the positive fault state are completed, the fault state is reliably latched and the differential judgment start signal is stably generated, effectively avoiding the problems of fault state loss, trigger signal jitter or false triggering, and providing stable and reliable start triggering conditions for subsequent fault level calculation, delay matching and trip execution, ensuring the continuous, accurate and orderly execution of the 10kV overhead line phase-to-phase fault differential protection process.

[0133] After receiving the differential judgment start signal, the fault phase current in the current discrete sequence is nonlinearly mapped to the transient characteristic duration in the initial polarity of the current jump to obtain the fault level coefficient of the overhead line.

[0134] In this embodiment of the invention, the process of obtaining the fault level coefficient of the overhead line is as follows:

[0135] When the differential judgment start signal is received, the hardware trigger circuit responds to the differential judgment start signal and outputs a high-level enable signal to activate the fault phase screening circuit.

[0136] The fault phase screening circuit extracts the current sampling value of the fault phase from the current discrete sequence based on the hardware trigger signal to obtain the fault phase current sequence of the current discrete sequence.

[0137] Read the transient characteristic duration in the initial polarity of the current jump, and take the initial abrupt change point as the time zero point to extract the transient current subsequence within the transient characteristic duration in the fault phase current sequence;

[0138] The time interval of the timestamp of the sampled value in the transient current subsequence is tuned to the time distance between the initial abrupt change point to obtain the attenuation weight sequence corresponding to the transient current subsequence;

[0139] The absolute value of the sampled value in the transient current subsequence is weighted and superimposed with the corresponding weight in the attenuation weight sequence to obtain the weighted cumulative total of the overhead line.

[0140] The weighted cumulative total is compared with the preset level threshold range for threshold judgment to obtain the fault level coefficient of the overhead line.

[0141] After receiving the differential judgment start signal, the hardware trigger circuit immediately outputs a stable high-level enable signal, which synchronously activates the dedicated fault phase screening hardware circuit. The fault phase screening circuit retrieves the unique fault phase identifier signal determined in the previous fault direction judgment stage. The unique fault phase identifier signal accurately corresponds to the line phase where the phase-to-phase fault occurred. The circuit retrieves the fully stored current discrete sequence from the hardware data storage unit, and filters and extracts all current sample values ​​that completely match the fault phase identifier according to the original time sequence of the sampling points. After extraction, all sample values ​​are strictly arranged according to the original time sequence to form a continuous and complete set of values. The continuous and complete set of values ​​is the fault phase current sequence of the current discrete sequence.

[0142] The hardware storage unit for the initial polarity of the current jump stores the transient characteristic duration. The pre-stored transient characteristic duration is based on the typical duration of the initial transient stage after a phase-to-phase fault in a 10kV overhead line, combined with a large amount of field measured operating data and preset to a fixed duration. The hardware duration reading circuit reads the transient characteristic duration value through precise address addressing. At the same time, the hardware timing marking circuit marks the starting point of the line current change waveform of the overhead line, which was determined in the previous waveform processing stage, as the time zero point of the entire transient analysis process. The hardware timing interception circuit receives two sets of parameters: the time zero point and the transient characteristic duration. With the time zero point as the starting boundary and the transient characteristic duration as the ending boundary, it accurately intercepts all sampled values ​​within the boundary range from the fault phase current sequence, automatically discarding invalid sampled values ​​outside the boundary range. The continuous set of intercepted values ​​is the transient current subsequence.

[0143] The hardware time-spacing tuning circuit incorporates hardware logic that matches the attenuation characteristics of the transient fault current in 10kV overhead lines. This matching hardware logic follows the physical law that the transient fault current naturally decays over time. It retrieves the timestamp corresponding to each sample value in the transient current subsequence one by one, calculates the actual time interval between each timestamp and the zero point of the initial abrupt change, and assigns a larger weight to the sample value with a shorter time interval and a smaller weight to the sample value with a longer time interval. All the generated weights are arranged sequentially according to the sampling time order of the transient current subsequence, forming a complete weight set that corresponds one-to-one with each sample point. This complete weight set is the attenuation weight sequence corresponding to the transient current subsequence.

[0144] The hardware weighted calculation circuit first activates the dedicated absolute value conversion module to unsign each sampled value in the transient current subsequence, converting positive and negative values ​​into absolute values. Then, the circuit activates the point-to-point matching operation logic to perform corresponding numerical operations on the absolute value of each converted sampled value and the weight at the same time position in the attenuation weight sequence. After completing the matching operation of all sampled points, the circuit activates the continuous accumulation operation module to accumulate the results of all matching operations in time sequence. The final total value is the weighted accumulation total of the overhead line.

[0145] The preset threshold ranges for fault levels are based on the three-level classification standard of minor, moderate, and severe phase-to-phase faults on 10kV overhead lines, and are also quantitatively determined by combining measured data of the line's rated current and various fault currents. The specific classifications are as follows:

[0146] Minor fault level: When the weighted cumulative total is less than or equal to 1.5 times the rated current, it is judged as a minor fault, and the corresponding level code is "1";

[0147] General fault level: When the weighted cumulative total is greater than the upper limit of the minor fault level and less than or equal to 3 times the rated current, it is judged as a general fault, and the corresponding level code is "2".

[0148] Severe fault level: When the weighted cumulative total exceeds the upper limit of the general level, it is judged as a severe fault, and the corresponding level code is "3".

[0149] The three threshold intervals mentioned above are fixed in the hardware threshold decision circuit. The hardware threshold decision circuit compares the transient weighted cumulative total of the fault phase current with the threshold values ​​of each level in turn to locate the interval to which it belongs, and outputs a fixed numerical identifier according to the level code corresponding to the interval. The fixed numerical identifier is the fault level coefficient of the overhead line, which is used for subsequent delay matching and tripping operations.

[0150] Preferably, this invention achieves accurate extraction of fault phase current, effective interception of transient subsequence, scientific tuning of attenuation weights, objective calculation of weighted accumulation, and accurate judgment of fault level through the coordinated operation of the entire link hardware circuit. It fully conforms to the transient change law of phase-to-phase faults in 10kV overhead lines, accurately quantifies the actual severity of the fault, and generates stable and reliable fault level coefficients. This provides a real and credible quantitative basis for subsequent action delay level matching, making the graded judgment of differential protection more in line with the actual fault state, and greatly improving the pertinence and rationality of protection actions.

[0151] Based on a preset action delay level library, the fault level coefficient is matched within a range, and a delay timer is started according to the matched delay level. After the delay timer expires, a tripping operation is performed to disconnect the faulty section of the overhead line.

[0152] In this embodiment of the invention, the process of disconnecting the faulty section of the overhead line is as follows:

[0153] Map the fault level coefficient to a preset action delay level library, locate the numerical range in which the fault level coefficient falls, and extract the delay level corresponding to the numerical range.

[0154] Based on the delay level, the corresponding delay length value is extracted from the action delay level library, and the delay length value is loaded into the delay counter to start the decrementing counting process of the delay counter;

[0155] Monitor the current count value of the delay counter. When the current count value decreases to zero, determine that the delay timer has ended and set the trip enable flag of the fault section in the overhead line.

[0156] The hardware trip execution circuit monitors the level of the trip enable flag in real time. When the trip enable flag is detected to be at a valid high level, the hardware trip execution circuit responds to the trip enable flag signal and outputs a stable drive level signal that meets the circuit breaker operation requirements to the circuit breaker operating mechanism corresponding to the fault section. This triggers the internal tripping structure of the circuit breaker operating mechanism to perform the tripping action and disconnect the fault section of the overhead line.

[0157] The preset action delay level library establishes a one-to-one fixed correspondence between fault level coefficients and delay levels based on the upper and lower level section coordination specifications of 10kV overhead line phase-to-phase fault differential protection, the graded delay setting standards for faults of different severity, and the differential coordination requirements for line operation. This fixed correspondence is permanently stored in the dedicated read-only memory unit of the hardware address mapping circuit. After receiving the fault level coefficient, the hardware address mapping circuit iterates and compares all the value ranges in the action delay level library one by one according to the hardware address addressing method, accurately locates the unique value range to which the fault level coefficient belongs, and extracts the delay level identifier pre-bound to the unique value range. The delay level identifier is the delay level that matches the fault level coefficient.

[0158] Based on the acquired delay level identifier, the hardware delay extraction circuit precisely extracts the delay length value that uniquely matches the delay level from the action delay level library stored in the hardware storage unit through hardware address addressing. The delay length value is a fixed duration preset according to the line differential protection coordination requirements. The hardware value loading circuit transmits the delay length value to the parameter configuration unit of the delay counter in a stable hardware level form. After the delay counter completes the value verification and loading, it immediately starts the clock-synchronized decrementing counting process, gradually decreasing from the delay length value to zero according to a fixed clock cycle.

[0159] The hardware real-time monitoring circuit keeps synchronized with the working clock of the delay counter, continuously collects the current count value output by the delay counter in real time, and continuously compares the current count value with the zero value in hardware level. When the level state of the current count value and the zero value are completely consistent, it immediately confirms that the entire delay timing process has been completed. The hardware flag setting circuit outputs a fixed high-level valid signal to the fault section control unit, and stably sets the trip enable flag of the fault section in the overhead line to the valid state.

[0160] The hardware trip execution circuit monitors the trip enable flag's level in real time with a fixed clock cycle. When the trip enable flag is detected to be in a valid high-level state, it immediately outputs a stable drive level signal that meets the circuit breaker operation requirements to the circuit breaker operating mechanism corresponding to the fault section. After receiving the drive level signal, the circuit breaker operating mechanism triggers the internal tripping structure to perform the tripping action, disconnecting the fault section of the overhead line through physical mechanical operation, thus completing the electrical isolation of the fault section.

[0161] Ideally, by using a fully hardware-based fixed mapping relationship and timing control logic, the fault level coefficient and action delay can be accurately matched. The delay counting, status monitoring and trip execution are completed in strict accordance with the requirements of differential protection. The graded delay action is implemented according to the actual severity of the fault, and the fault section is accurately and quickly disconnected. This effectively avoids protection maloperation or failure to operate, improves the efficiency and accuracy of phase-to-phase fault isolation of 10kV overhead lines, and ensures the rationality of the section coordination and the overall reliability of differential protection.

[0162] Figure 2 This flowchart illustrates the process of generating line current and voltage variation waveforms for overhead lines from instantaneous three-phase current and voltage waveforms. The process involves digital sampling and filtering of the acquired instantaneous waveforms, followed by equal-interval quantization to obtain discrete current and voltage sequences. A dynamic reference value is acquired through sliding window steady-state detection, and the variation increment sequence is obtained through point-by-point differential analysis. Abrupt edge locking is performed on the variation increment sequence, and abrupt waveform units are extracted. The peak amplitudes of these abrupt waveform units are then arranged or reconstructed according to time sequence to generate the line current and line voltage variation waveforms for the overhead line.

[0163] Figure 3 This document presents a flowchart for fault direction determination and differential fault indication signal generation. It describes the process of determining the fault direction and generating a differential fault indication signal based on the line current and line voltage change waveforms of an overhead line. The power direction angle offset is calculated using cross-phase detection, and the initial polarity of the current jump is read from the line current change waveform of the overhead line. The sign bits of the two are compared: if the signs match and the power direction angle offset falls within a preset valid operating range, a positive fault tag is output; otherwise, a negative fault tag is output. The positive fault tag is written to the corresponding bit in the status register and triggers hardware latching, ultimately generating the differential fault indication signal.

[0164] Figure 4 This document presents a flowchart illustrating the calculation of fault level coefficients and the execution of adaptive time-delay tripping. Upon receiving the fault differential judgment initiation signal, the fault phase current sequence is extracted, and a transient current subsequence within the transient characteristic duration is extracted, using the initial abrupt change point as the time zero point. The subsequence is time-distance tuned to generate an attenuation weight sequence, which is then weighted and superimposed to obtain a weighted cumulative total. The weighted cumulative total is compared with a preset level threshold range for threshold judgment, and the fault level coefficient is output. The fault level coefficient is mapped to an action delay level library, the delay level is matched, and the delay length value is obtained. A delay counter is then started to decrement. When the count value reaches zero, the trip enable flag is set, and a tripping operation is performed to disconnect the faulty section.

[0165] This embodiment also provides a computer device applicable to a 10kV overhead line phase-to-phase fault differential protection method, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the 10kV overhead line phase-to-phase fault differential protection method proposed in the above embodiment.

[0166] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0167] This embodiment also provides a storage medium storing a computer program. When executed by a processor, the program implements a method for phase-to-phase fault differential protection of a 10kV overhead line as proposed in the above embodiment. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0168] In summary, this invention: By quantifying, discretizing, and performing point-by-point differential processing on the instantaneous waveforms of three-phase current and voltage of a 10kV overhead line, it can accurately extract the waveforms of line current and line voltage changes. Combined with cross-phase detection to obtain the power direction angle offset, and with the initial polarity of the current jump, it can accurately determine the fault direction. It can reliably latch the positive-direction fault state and trigger the differential judgment process, ensuring the accuracy of fault identification and the stability of action triggering from the source. By nonlinearly mapping the fault phase current and transient characteristic duration to obtain the fault level coefficient, it can accurately quantify the actual severity of the fault. Then, by interval matching with a preset action delay level library, it ensures a high degree of adaptation between the protection delay and the fault state, thoroughly realizing accurate fault classification and ensuring that the protection action accurately targets the fault section, eliminating the operational risks caused by protection action deviation.

[0169] This invention performs a tripping operation after timing based on a matched delay level, enabling rapid disconnection of the faulty section and significantly improving the isolation efficiency of phase-to-phase faults on 10kV overhead lines, achieving rapid and accurate fault handling. Leveraging the technical advantages of precise graded protection and rapid section isolation, this invention comprehensively optimizes the overall performance of phase-to-phase fault protection for overhead lines, effectively shortening fault handling time, reducing the continuous impact of faults on line operation, and significantly improving the stability and security of 10kV overhead line power supply. Simultaneously, the entire protection logic is implemented using digital processing and hardware latching logic, improving the response speed and operational reliability of the protection device, providing a solid technical guarantee for the safe and stable operation of the distribution network, and making 10kV overhead line fault protection more efficient, accurate, and reliable.

[0170] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for differential protection against phase-to-phase faults in 10kV overhead lines, characterized in that: include, The instantaneous waveforms of the three-phase current and the three-phase voltage at monitoring points on the overhead line are quantized at equal intervals to obtain the discrete current sequence and discrete voltage sequence of the overhead line. By performing point-by-point difference on the current discrete sequence and the voltage discrete sequence respectively, the line current change waveform and the line voltage change waveform of the overhead line are obtained; The cross-phase detection is performed between the line current change waveform and the line voltage change waveform of the overhead line to obtain the power direction angle offset of the overhead line, and the initial polarity of the current jump is read from the starting point of the line current change waveform of the overhead line. The power direction angle offset and the initial polarity of the current jump are compared to determine whether they are the same or different, and the fault direction label of the overhead line is obtained. When the fault direction label is a positive fault, the fault direction label is written into the status register for latching and triggering to obtain the differential judgment start signal of the overhead line. After receiving the differential judgment start signal, the fault phase current in the current discrete sequence is nonlinearly mapped to the transient characteristic duration in the initial polarity of the current jump to obtain the fault level coefficient of the overhead line. Based on a preset action delay level library, the fault level coefficient is matched within a range, and a delay timer is started according to the matched delay level. After the delay timer expires, a tripping operation is performed to disconnect the faulty section of the overhead line.

2. The method for differential protection of phase-to-phase faults on a 10kV overhead line as described in claim 1, characterized in that, The process of obtaining the discrete current sequence and discrete voltage sequence of the overhead line is as follows: The instantaneous waveforms of three-phase current and three-phase voltage at monitoring points on the overhead line were collected; The instantaneous waveforms of the three-phase current and the three-phase voltage are digitally sampled to obtain the current sampling sequence and voltage sampling sequence of the overhead line. High-frequency noise components in the current sampling sequence and the voltage sampling sequence are filtered out to obtain a smoothed current sampling sequence and a smoothed voltage sampling sequence for the overhead line. According to a preset fixed time interval, the smoothed current sampling sequence and the smoothed voltage sampling sequence are truncated with a fixed step size to obtain the current discrete sequence and voltage discrete sequence of the overhead line.

3. The method for differential protection of phase-to-phase faults on a 10kV overhead line as described in claim 1, characterized in that, The process of obtaining the line current change waveform and line voltage change waveform of the overhead line is as follows: Simultaneously perform sliding window steady-state detection on the current discrete sequence and the voltage discrete sequence to obtain the current steady-state reference point and voltage steady-state reference point of the overhead line; Using the sampling value corresponding to the current steady-state reference point as the current dynamic reference value, the digital values ​​of each subsequent sampling point in the current discrete sequence are subtracted one by one from the most recent current dynamic reference value to obtain the current change increment sequence of the overhead line. Using the sampled value corresponding to the steady-state voltage reference point as the voltage dynamic reference value, the digital values ​​of each subsequent sampled point in the voltage discrete sequence are subtracted one by one from the most recent voltage dynamic reference value to obtain the voltage change increment sequence of the overhead line. Abrupt edge locking is performed on the current change increment sequence and the voltage change increment sequence respectively to obtain the current abrupt change waveform unit and the voltage abrupt change waveform unit of the overhead line; The peak amplitudes in the current change waveform unit are time-sequentially arranged to obtain the line current change waveform of the overhead line, and the peak amplitudes in the voltage change waveform unit are time-sequentially reconstructed to obtain the line voltage change waveform of the overhead line.

4. A method for differential protection of phase-to-phase faults on a 10kV overhead line as described in claim 2, characterized in that, The process of obtaining the power direction angle offset of the overhead line is as follows: Based on a preset noise threshold, the abrupt leading edge of the line current change waveform of the overhead line is captured to obtain the arrival time of the current abrupt change in the line current change waveform of the overhead line. Extract the first abrupt change start point in the line voltage change waveform where the amplitude exceeds the noise threshold, and use the absolute time scale corresponding to the abrupt change start point as the arrival time of the voltage abrupt change in the line voltage change waveform; The time offset between the arrival times of the current surge and the voltage surge is obtained by taking the difference between the arrival times of the current surge and the arrival times of the voltage surge. Obtain the per-unit value of the power frequency angular velocity corresponding to the rated frequency of the overhead line, and divide the time offset by the fixed time interval to obtain the phase offset multiple of the overhead line. Then multiply the phase offset multiple by the per-unit value of the power frequency angular velocity to obtain the power direction angle offset of the overhead line.

5. A method for differential protection of phase-to-phase faults on a 10kV overhead line as described in claim 1, characterized in that, The process of obtaining the fault direction label of the overhead line is as follows: The power direction angle offset is subjected to direction position identification to obtain the polarity direction identifier of the power direction angle offset; The initial polarity of the current jump is identified by the jump direction to obtain the current polarity identifier of the initial polarity of the current jump; When the sign bit of the polarity direction indicator is the same as that of the current polarity indicator, it is determined that the polarities are the same; when the sign bit of the polarity direction indicator is opposite to that of the current polarity indicator, it is determined that the polarities are different. When it is determined that the polarity is the same and the absolute value of the power direction angle offset falls within the preset effective action range, the positive direction fault label of the overhead line is output. When the polarity is determined to be opposite, the fault tag in the opposite direction of the overhead line is output; When it is determined that the polarity is the same and the absolute value of the power direction angle offset does not fall within the effective operating range, the reverse direction fault tag of the overhead line is output.

6. A method for differential protection of phase-to-phase faults on a 10kV overhead line as described in claim 1, characterized in that, The process of obtaining the differential judgment start signal for the overhead line is as follows: If the direction identifier bit in the fault direction label is a positive direction fault, then the fault direction latch bit pre-allocated in the location status register corresponds to the current monitoring section of the overhead line. Write the positive direction fault status value in the fault direction label into the fault direction latch bit to update the current value of the status register; Based on the updated status register, the hardware latching logic corresponding to the status register is triggered to hold the positive direction fault status value in the fault direction latch bit and generate the latching completion identifier of the status register. The latch completion flag is mapped to a state to obtain the differential judgment start signal for the overhead line.

7. A method for differential protection of phase-to-phase faults on a 10kV overhead line as described in claim 1, characterized in that, The process of obtaining the fault level coefficient of the overhead line is as follows: When the grade difference judgment start signal is received, the hardware trigger circuit responds to the grade difference judgment start signal and outputs a high-level enable signal to activate the fault phase screening circuit. The fault phase screening circuit extracts the current sampling value of the fault phase from the current discrete sequence according to the hardware trigger signal, so as to obtain the fault phase current sequence of the current discrete sequence. Read the transient characteristic duration in the initial polarity of the current jump, and take the starting point of the sudden change as the time zero point to extract the transient current subsequence in the fault phase current sequence that is located within the transient characteristic duration; The time interval of the timestamp of the sampled value in the transient current subsequence and the time distance of the initial abrupt change point are tuned to obtain the attenuation weight sequence corresponding to the transient current subsequence; The absolute value of the sampled value in the transient current subsequence is weighted and superimposed with the weight at the corresponding position in the attenuation weight sequence to obtain the weighted cumulative total of the overhead line; The weighted cumulative total is compared with a preset level threshold range to make a threshold decision, thereby obtaining the fault level coefficient of the overhead line.

8. A method for differential protection of phase-to-phase faults on a 10kV overhead line as described in claim 1, characterized in that, The process of disconnecting the faulty section of the overhead line is as follows: The fault level coefficient is mapped to a preset action delay level library, the numerical range in which the fault level coefficient falls is located, and the delay level corresponding to the numerical range is extracted. Based on the delay level, the corresponding delay length value is extracted from the action delay level library, and the delay length value is loaded into the delay counter to start the decrementing counting process of the delay counter; Monitor the current count value of the delay counter. When the current count value decreases to zero, determine that the delay timer has ended and set the trip enable flag of the fault section in the overhead line. The hardware trip execution circuit monitors the level of the trip enable flag in real time. When the trip enable flag is detected to be at a valid high level, the hardware trip execution circuit responds to the trip enable flag signal and outputs a stable drive level signal that meets the circuit breaker operation requirements to the circuit breaker operating mechanism corresponding to the fault section. This triggers the internal tripping structure of the circuit breaker operating mechanism to perform the tripping action and disconnect the fault section of the overhead line.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, it implements the steps of the phase-to-phase fault differential protection method for a 10kV overhead line as described in any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the phase-to-phase fault differential protection method for a 10kV overhead line as described in any one of claims 1 to 8.

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