Single-phase combined feeder protection method and system for phase-to-phase power supply

Abstract

The application provides a single-phase combined in-phase power supply system feeder protection method and system, relates to the technical field of relay protection, and the single-phase combined in-phase power supply system comprises an in-phase compensation device and a feeder.The method comprises the following steps: real-time monitoring of a feeder outlet current signal is performed to realize fault sensing, a fault sensing time is recorded and a protection starting signal is generated when a preset protection condition is met; the protection starting signal is sent to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to an electrical connection point of the feeder based on the signal and the fault sensing time; the detection excitation signal is used to synchronously acquire a feeder two-port transient current signal and realize fault discrimination; a protection action instruction is generated according to a fault discrimination result, and a feeder protection result is obtained. The method actively injects a detection excitation signal by triggering the in-phase compensation device through fault sensing, and realizes the selectivity and reliability of feeder protection by using the difference between the transient current signals of the two ports of the feeder.

Description

Technical Field

[0001] This invention belongs to the field of relay protection technology, specifically relating to a feeder protection method and system for a single-phase combined in-phase power supply system. Background Technology

[0002] In single-phase AC distribution systems with power electronic compensation devices, achieving in-phase power supply to the load side through in-phase compensation is a crucial technical means to improve power supply continuity and power quality. Existing feeder protection typically relies on a fixed system impedance model, passively detecting the electrical quantities naturally generated by faults and identifying faults based on current amplitude or impedance characteristics. However, power electronic compensation devices exhibit controlled current source characteristics under fault conditions, and their output response is constrained by the underlying control strategy and no longer follows the fixed impedance model. This causes the amplitude and phase distribution of the fault current to deviate from classical laws, resulting in reduced applicability, insufficient selectivity, and inadequate speed of traditional protection principles. Furthermore, existing protection methods do not fully utilize the controllable characteristics of the compensation devices, relying solely on passive detection on the feeder side. Under weak fault characteristics, it is difficult to reliably identify the fault direction, thus limiting protection performance. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method and system for feeder protection in a single-phase combined in-phase power supply system, thereby solving the aforementioned problems. This method actively injects a detection excitation signal by triggering the in-phase compensation device through fault perception, and uses the difference in transient current signals at the two ports of the feeder to determine the fault, thus achieving selectivity and reliability of feeder protection.

[0004] To solve the above-mentioned technical problems, the present invention provides a feeder protection method for a single-phase combined in-phase power supply system, wherein the single-phase combined in-phase power supply system includes an in-phase compensation device and a feeder, and the method includes the following steps: Real-time monitoring and acquisition of feeder outlet current signal, and fault detection and judgment based on the feeder outlet current signal. When the feeder outlet current signal meets the preset protection conditions, the fault detection time is recorded and a protection start signal is generated. The protection start signal is sent to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time. Based on the detection excitation signal, the transient current signal of the two ports of the feeder is synchronously acquired, and the fault is determined based on the transient current signal to obtain the fault determination result; Based on the fault identification result, a protection action command is generated so that the single-phase combined in-phase power supply system can perform feeder protection based on the protection action command, thereby obtaining the feeder protection result.

[0005] In the above scheme, the feeder outlet current signal is monitored and acquired in real time, and fault detection and judgment are performed based on the feeder outlet current signal. When the preset protection conditions are met, the fault detection time is recorded and a protection start signal is generated, thereby establishing a time reference for the fault occurrence and triggering the subsequent active detection process. The protection start signal is sent to the in-phase compensation device, which outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time. This triggers a controllable transient response in scenarios where the distribution characteristics of the fault electrical quantity change due to the connection of the in-phase compensation device. The transient current signal of the two ports of the feeder is acquired based on the detection excitation signal. Since the transient current signal of the two ports will show a difference when the detection excitation signal propagates along the feeder and the fault is located between the two ports, the fault can be judged by acquiring the transient current signal of the two ports of the feeder. Finally, the protection action command is generated based on the fault judgment result, so that the single-phase combined in-phase power supply system can accurately isolate the faulty feeder when a fault occurs between the two ports of the feeder, thereby improving the selectivity and reliability of the feeder protection.

[0006] Furthermore, the fault detection and determination based on the feeder outlet current signal, when the feeder outlet current signal meets the preset protection conditions, includes recording the fault detection time and generating a protection start signal, including: The instantaneous current value at the current sampling point and the instantaneous current value at the sampling point before the power frequency cycle are obtained based on the feeder outlet current signal. The current surge is obtained based on the instantaneous current value at the current sampling point and the instantaneous current value at the sampling point before the power frequency cycle; The current surge is compared with the preset start-up threshold current value. When the current surge is greater than the preset start-up threshold current value, the fault detection time is recorded and the protection start signal is generated.

[0007] In the above scheme, the instantaneous current value at the current sampling point and the instantaneous current value at the sampling point before the power frequency cycle are obtained based on the feeder outlet current signal. The current surge is obtained by the difference between the two, and the current surge is compared with the preset start-up threshold current value. When the surge is greater than the start-up threshold, the fault detection time is recorded and a protection start signal is generated. Since the current surge is calculated by the difference between the sampling values ​​of adjacent power frequency cycles of the same channel, it has a natural suppression effect on normal load fluctuations, while being highly sensitive to current surges caused by short-circuit faults. The preset start-up threshold current value is set to a value higher than the normal load fluctuation level but lower than the minimum current change of the fault. This avoids false start during normal operation and can sensitively detect current changes caused by faults, thereby achieving rapid fault detection while ensuring reliability, and providing an accurate time reference for subsequent active detection processes.

[0008] Further, the step of sending the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time, includes: The protection start signal is sent to the in-phase compensation device so that the in-phase compensation device enters the fault active detection mode based on the protection start signal and determines the detection excitation signal parameters based on the fault active detection mode. Based on the detection excitation signal parameters, a detection excitation signal is generated, and based on the detection excitation signal and the preset basic current limiting control signal, the current reference command is reconstructed to obtain the instantaneous reference command for the output current. The detection start time is determined based on the fault perception time and the preset detection delay, so that the in-phase compensation device outputs the detection excitation signal to the electrical connection point of the feeder based on the detection start time and the instantaneous reference command of the output current.

[0009] In the above scheme, a protection start signal is sent to the in-phase compensation device, enabling the device to enter active fault detection mode based on this signal and determine the detection excitation signal parameters. Then, based on these parameters, a detection excitation signal is generated and reconstructed with a preset basic current limiting control signal to form an instantaneous reference command for the output current. Simultaneously, the detection start time is determined based on the fault perception time and a preset detection delay, causing the in-phase compensation device to output the detection excitation signal to the electrical connection point of the feeder according to this start time and the instantaneous reference command for the output current. By reconstructing the detection excitation signal and the preset basic current limiting control signal into an instantaneous reference command for the output current, the in-phase compensation device can simultaneously output a detection excitation signal and maintain the basic current limiting function in active fault detection mode. The detection start time determined based on the fault perception time and the preset detection delay maintains a fixed timing difference between the output of the detection excitation signal and the fault perception time, thereby avoiding time-domain overlap between the detection excitation signal and the transient signal of the natural fault. This ensures that there is a clear excitation source when subsequently acquiring the transient current signal based on the detection excitation signal, improving the reliability and accuracy of fault diagnosis.

[0010] Further, the detection excitation signal is a short-time coded pulse perturbation sequence; the step of determining the detection excitation signal parameters based on the active fault detection mode, and generating the detection excitation signal based on the detection excitation signal parameters, includes: The round-trip time of the traveling wave is obtained based on the pre-acquired feeder length and the pre-acquired traveling wave propagation speed; The pulse width is obtained based on the traveling wave round-trip time and a preset empirical coefficient, and the pulse interval is determined based on the pulse width; The detection excitation signal parameters are obtained based on the preset injection amplitude, the preset number of pulse pairs, the pulse width, and the pulse interval. The short-time coded pulse perturbation sequence is generated based on the detection excitation signal parameters.

[0011] In the above scheme, the round-trip time of the traveling wave is obtained based on the pre-acquired feeder length and traveling wave propagation speed. Then, the pulse width is obtained and the pulse interval is determined based on the round-trip time and a preset empirical coefficient. Finally, the detection excitation signal parameters are obtained based on the preset injection amplitude, the preset number of pulse pairs, the pulse width, and the pulse interval to generate a short-time coded pulse disturbance sequence. Since the pulse width is set according to the round-trip time of the traveling wave and the preset empirical coefficient, the duration of a single pulse in the feeder covers the round-trip process of the traveling wave, avoiding the overlap of the reflected wave and the incident wave in the time domain. The pulse interval is determined by the pulse width, ensuring that there is no mutual interference between adjacent pulses. The preset injection amplitude, the preset number of pulse pairs, the pulse width, and the pulse interval jointly constrain the time-domain waveform characteristics of the short-time coded pulse disturbance sequence, giving the sequence a recognizable coded structure. Thus, when acquiring transient current signals at the two ports of the feeder, the detection response component can be accurately extracted from background noise and fault transients, improving the reliability and anti-interference capability of fault diagnosis based on transient current signals.

[0012] Furthermore, the fault determination based on the transient current signal to obtain the fault determination result includes: The power frequency background component is eliminated based on the transient current signal to obtain a two-terminal transient current increment signal; The dual-end detection response signal is obtained based on a preset sliding cross-correlation algorithm, a preset theoretical detection waveform, and the dual-end transient current increment signal. Based on the dual-end detection response signal, a difference feature vector is constructed, and fault discrimination is performed based on the difference feature vector to obtain the fault discrimination result.

[0013] In the above scheme, the incremental signal of the transient current is obtained by eliminating the power frequency background component based on the transient current signal. Then, the incremental signal of the transient current is obtained from the incremental signal based on the preset sliding cross-correlation algorithm and the preset theoretical detection waveform. Finally, the difference feature vector is constructed based on the response signal and the fault is judged. Eliminating the power frequency background component can separate the normal compensation current of the in-phase compensation device and the load power frequency current, and only retain the transient increment caused by the detection excitation, so as to avoid the power frequency quantity interfering with the extraction of transient features. The sliding cross-correlation algorithm uses the theoretical detection waveform as a template to match segment by segment in the incremental signal of the two ends, and accurately extracts the response waveform segment that is synchronized with the detection sequence time, so as to ensure that the two ends signal strictly corresponds to the same detection excitation. The difference feature vector is constructed based on the two ends detection response signal, and the difference of the two ends response is quantified from multiple dimensions such as instantaneous amplitude, energy distribution and correlation. This makes the essential asymmetry of the two ends response during the fault within the zone and the symmetry of the through current during the fault outside the zone form distinguishable quantitative features, thereby improving the fault judgment accuracy.

[0014] Further, the difference feature vector includes an instantaneous level difference index, an effective value level difference index, and a correlation level difference index; the fault discrimination based on the difference feature vector to obtain the fault discrimination result includes: The dual-end differential current value and dual-end suppression current value are obtained based on the dual-end detection response signal; Based on the aforementioned two-terminal difference current value and two-terminal suppression current value, instantaneous level difference index, effective value level difference index, and correlation level difference index are constructed. Based on the effective value level difference index and the preset effective value level difference threshold, a first-level discrimination is performed to obtain the first-level discrimination result; When the first-level discrimination result is an intra-regional fault, a second-level discrimination is performed based on the correlation level difference index and the preset correlation level difference threshold to obtain the second-level discrimination result; When the second-level discrimination result is a non-regional fault, a third-level discrimination is performed based on the instantaneous level difference index and the preset cumulative instantaneous difference threshold to obtain the third-level discrimination result; The fault identification result is determined based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result.

[0015] In the above scheme, the difference current value and the suppression current value at both ends are obtained based on the dual-end detection response signal. Based on this, instantaneous level difference index, effective value level difference index and correlation level difference index are constructed. The first level of discrimination is performed based on the effective value level difference index and the preset effective value level difference threshold. When the first level of discrimination result is an in-zone fault, the second level of discrimination is performed based on the correlation level difference index and the preset correlation level difference threshold. When the second level of discrimination result is a non-in-zone fault, the third level of discrimination is performed based on the instantaneous level difference index and the preset cumulative instantaneous difference threshold. Finally, the fault discrimination result is determined based on the first level discrimination result, the second level discrimination result or the third level discrimination result. The first level of discrimination is achieved through the effective value level difference index, which quickly distinguishes between faults within and outside the fault zone from an energy perspective. The effective value level difference index is highly sensitive to the energy difference of the two-terminal current. The second level of discrimination is achieved through the correlation level difference index, which verifies the results of the first level from a waveform similarity perspective. It distinguishes between faults within the fault zone by utilizing the low correlation of the two-terminal detection response signals and the high correlation of faults outside the fault zone. The third level of discrimination is achieved through the instantaneous level difference index, which accumulates and verifies the results of faults outside the fault zone from a time-domain waveform detail perspective. The three progressive discrimination levels complement each other, avoiding misjudgment by a single index in boundary fault scenarios and improving the reliability of fault discrimination results.

[0016] It should be noted that the first-level, second-level, and third-level discrimination described in this scheme constitute a progressively advancing and mutually verifying fault discrimination logic. The first-level discrimination uses an effective value-level difference index to measure the overall difference between the two-terminal response signals from an energy dimension. Its main function is to quickly screen samples suspected of being within the fault zone with high sensitivity, effectively covering various fault types including high-resistance grounding. However, this level of discrimination may have a risk of misjudgment due to large through-currents. The second-level discrimination, based on the initial determination of an in-zone fault by the first-level discrimination, introduces a correlation-level difference index for verification from a waveform similarity dimension. It utilizes the physical characteristics of low correlation between the two-terminal detection response signals reflecting independent current components flowing to the fault point during in-zone faults and high correlation between the two-terminal signals representing different measurements of the same through-current during out-of-zone faults, further eliminating misjudgments caused by through-current scenarios such as metallic short circuits outside the fault zone. The third level of discrimination addresses boundary samples where the results of the first two levels diverge—specifically, cases where the effective value level difference exceeds the threshold while the correlation level difference fails to meet it. It calculates the cumulative value of the instantaneous level difference index over the detection sequence period, performing a final verification from the perspective of time-domain waveform details. This avoids discrimination bias caused by instantaneous fluctuations or noise interference at individual sampling points. These three progressive levels of discrimination sequentially screen and confirm the dual-end response signal from three dimensions: energy, waveform similarity, and time-domain details. These three levels complement each other, effectively mitigating the risk of misjudgment under boundary fault scenarios using a single index, thereby significantly improving the reliability of the fault discrimination results.

[0017] Further, determining the fault discrimination result based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result includes: A preliminary fault identification result is determined based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result; When the preliminary fault identification result is an external fault, the direction coefficient of the feeder outlet end is obtained based on the dual-end detection response signal; The direction is determined based on the direction coefficient at the feeder outlet, and the fault direction determination result is obtained. The fault identification result is determined based on the fault direction determination result and the preliminary fault identification result.

[0018] In the above scheme, a preliminary fault identification result is determined based on the first-level, second-level, or third-level discrimination results. When the preliminary fault identification result indicates an out-of-zone fault, the direction coefficient at the feeder outlet is obtained based on the dual-end detection response signal. Then, the direction is determined based on this direction coefficient to obtain the fault direction determination result. Finally, the fault identification result is determined based on the fault direction determination result and the preliminary fault identification result. Since an out-of-zone fault only indicates that the fault point is not between the two ends of the feeder, but cannot distinguish whether the fault is located in the positive or negative direction at the feeder outlet, the direction coefficient at the feeder outlet is calculated, and the reference flow direction of the detection current is determined using the polarity relationship of the transient components in the dual-end detection response signal, thereby clarifying the fault direction. Combining this fault direction determination result with the preliminary fault identification result not only confirms that the fault is out-of-zone but also provides specific location information, providing a directional basis for the selective coordination of adjacent feeder protection, avoiding protection maloperation or cascading tripping due to unclear direction, and further improving the reliability of feeder protection in the same-phase power supply system.

[0019] It should be noted that the first-level, second-level, and third-level discrimination results refer to the conclusions output by the step-by-step discrimination based on the effective value level difference index, the correlation level difference index, and the instantaneous level difference index, respectively. These three results work together to arrive at a preliminary judgment of whether the fault is inside or outside the area. When the fault is initially determined to be outside the area, the direction coefficient at the feeder outlet is further calculated using the dual-end detection response signal. The fault direction is then determined through the signal polarity relationship, thereby obtaining a complete fault discrimination result that simultaneously includes information on the nature and location of the fault, providing a reliable basis for coordination with adjacent protection systems.

[0020] Further, the step of generating a protection action command based on the fault determination result, so that the single-phase combined in-phase power supply system performs feeder protection based on the protection action command, and obtains the feeder protection result, includes: When the fault identification result is an intra-zone fault, a trip command is generated and sent to a preset circuit breaker, so that the preset circuit breaker isolates the fault feeder based on the trip command and generates a detection completion signal. When the fault identification result is an external fault, an external fault confirmation signal is generated, and an in-phase compensation device recovery command and a detection completion signal are generated based on the external fault confirmation signal. Based on the detection completion signal, the in-phase compensation device is controlled to stop outputting the detection excitation signal; Based on the fault determination result within the zone, the in-phase compensation device is switched to current-limiting operation mode, or based on the fault determination result outside the zone and the recovery command of the in-phase compensation device, the in-phase compensation device is switched to normal operation compensation mode, thereby obtaining the feeder protection result.

[0021] In the above scheme, when the fault identification result is an intra-zone fault, a trip command is generated and sent to a preset circuit breaker to isolate the faulty feeder, and a detection completion signal is generated at the same time; when the identification result is an extra-zone fault, an extra-zone fault confirmation signal, a phase compensation device recovery command, and a detection completion signal are generated; based on the detection completion signal, the phase compensation device is controlled to stop outputting detection excitation signals; based on the intra-zone fault identification result, the phase compensation device is switched to current-limiting operation mode; based on the extra-zone fault identification result and the phase compensation device recovery command, the phase compensation device is switched to normal operation compensation mode, thereby obtaining the feeder protection result. When a fault occurs within the protection zone, a trip command is generated to quickly isolate the faulty feeder using a preset circuit breaker. Simultaneously, the in-phase compensation device switches to current-limiting operation mode to prevent the fault current from continuously impacting the system. When a fault occurs outside the protection zone, an external fault confirmation signal and a recovery command for the in-phase compensation device are generated, causing the in-phase compensation device to switch to normal operation compensation mode to prevent power outages caused by false tripping of non-faulty feeders. Based on the detection completion signal, the in-phase compensation device is controlled to stop outputting detection excitation signals, ensuring the orderly termination of the active detection process. This achieves coordinated action between protection actions and compensation mode switching, improving the speed of feeder protection results and the stability of system operation.

[0022] Furthermore, the feeder protection method for a single-phase combined in-phase power supply system as described above also includes: Real-time detection and acquisition of the output current value of the in-phase compensation device; When the output current value is greater than or equal to the preset power device safety limit, a detection termination signal is output to the in-phase compensation device so that the in-phase compensation device stops outputting the detection excitation signal based on the detection termination signal. Based on the detection termination signal, a preset backup protection mechanism is triggered, so that the single-phase combined in-phase power supply system performs feeder protection based on the preset backup protection mechanism, and a backup protection result is obtained.

[0023] In the above scheme, the output current value of the in-phase compensation device is detected and acquired in real time. When the output current value is greater than or equal to the preset safety limit of the power device, a detection termination signal is output to the in-phase compensation device. This causes the in-phase compensation device to stop outputting the detection excitation signal based on the detection termination signal, and triggers a preset backup protection mechanism based on the detection termination signal. This enables the single-phase combined in-phase power supply system to perform feeder protection based on the preset backup protection mechanism, thus obtaining the backup protection result. During active detection, a sudden change in impedance at the fault point or the control response may cause the output current value of the in-phase compensation device to momentarily exceed the preset safety limit of the power device. By detecting in real time and comparing it with the safety limit, once the limit is exceeded, a detection termination signal is immediately output to forcibly stop the detection excitation signal, avoiding overcurrent damage to the power device. At the same time, the detection termination signal triggers the preset backup protection mechanism, switching the feeder protection from active detection mode to backup protection mode. This ensures that the fault can still be reliably isolated after active detection is safely withdrawn by the device. Thus, while protecting the physical safety of the power device, dual redundancy of the protection function is achieved, improving the reliability and safety of the power supply system.

[0024] This invention also provides a feeder protection system for a single-phase combined in-phase power supply system, comprising: The signal detection module is used to monitor and acquire the feeder outlet current signal in real time, and to perform fault detection and judgment based on the feeder outlet current signal. When the feeder outlet current signal meets the preset protection conditions, the fault detection time is recorded and a protection start signal is generated. The in-phase compensation device control module is used to send the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time; The fault detection module is used to synchronously acquire the transient current signal of the dual-port of the feeder based on the detection excitation signal, and to perform fault detection based on the transient current signal to obtain the fault detection result; The protection execution module is used to generate protection action commands based on the fault discrimination results, so that the single-phase combined in-phase power supply system can perform feeder protection based on the protection action commands and obtain feeder protection results.

[0025] In the above scheme, the signal detection module monitors and acquires the feeder outlet current signal in real time to perform fault detection and judgment. When the preset protection conditions are met, it records the fault detection time and generates a protection start signal. The in-phase compensation device control module sends the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the signal and the fault detection time. The fault discrimination module acquires the transient current signal of the two ports of the feeder synchronously based on the detection excitation signal and performs fault discrimination to obtain the fault discrimination result. The protection execution module generates a protection action command based on the fault discrimination result to perform feeder protection and obtain the feeder protection result. The signal detection module establishes a time reference for the fault occurrence based on the moment of fault detection, ensuring that the subsequent detection excitation signal and the transient fault process are controllable in timing. The in-phase compensation device control module switches the in-phase compensation device from normal operation mode to active detection mode, enabling the detection excitation signal to be accurately injected into the feeder electrical connection point. The fault discrimination module uses the detection excitation signal to synchronously acquire the dual-port transient current signal and performs fault discrimination based on the difference between the two-terminal transients, avoiding the electrical quantity characteristic distortion problem caused by the connection of the in-phase compensation device in traditional protection. The protection execution module generates corresponding action commands based on the results within or outside the protection zone, realizing accurate isolation of the faulty feeder or rapid restoration of the non-faulty feeder. The four modules are functionally integrated and work together to improve the selectivity and reliability of feeder protection. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of a feeder protection method for a single-phase combined in-phase power supply system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a feeder protection system architecture for a single-phase combined in-phase power supply system, provided as an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Please see Figure 1 This embodiment provides a feeder protection method for a single-phase combined in-phase power supply system. The single-phase combined in-phase power supply system includes an in-phase compensation device and a feeder. The method includes the following steps: Step S1: Monitor and acquire the feeder outlet current signal in real time, and perform fault detection and judgment based on the feeder outlet current signal. When the feeder outlet current signal meets the preset protection conditions, record the fault detection time and generate a protection start signal. Step S2: Send the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time; Step S3: Based on the detection excitation signal, synchronously acquire the transient current signal of the dual-port of the feeder, and perform fault judgment based on the transient current signal to obtain the fault judgment result; Step S4: Generate a protection action command based on the fault identification result, so that the single-phase combined in-phase power supply system can perform feeder protection based on the protection action command and obtain the feeder protection result.

[0029] In this embodiment, the feeder outlet current signal is monitored and acquired in real time, and fault detection and judgment are performed based on the feeder outlet current signal. When the preset protection conditions are met, the fault detection time is recorded and a protection start signal is generated, thereby establishing a time reference for the fault occurrence and triggering the subsequent active detection process. The protection start signal is sent to the in-phase compensation device, which outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time. This triggers a controllable transient response in the scenario where the distribution characteristics of the fault electrical quantity change due to the connection of the in-phase compensation device. The transient current signal of the two ports of the feeder is acquired based on the detection excitation signal. Since the transient current signal of the two ports will show a difference when the detection excitation signal propagates along the feeder and the fault is located between the two ports, the fault can be judged by acquiring the transient current signal of the two ports of the feeder. Finally, a protection action command is generated based on the fault judgment result, so that the single-phase combined in-phase power supply system can accurately isolate the faulty feeder when a fault occurs between the two ports of the feeder, thereby improving the selectivity and reliability of the feeder protection.

[0030] Furthermore, the fault detection and determination based on the feeder outlet current signal, when the feeder outlet current signal meets the preset protection conditions, includes recording the fault detection time and generating a protection start signal, including: The instantaneous current value at the current sampling point and the instantaneous current value at the sampling point before the power frequency cycle are obtained based on the feeder outlet current signal. The current surge is obtained based on the instantaneous current value at the current sampling point and the instantaneous current value at the sampling point before the power frequency cycle; The current surge is compared with the preset start-up threshold current value. When the current surge is greater than the preset start-up threshold current value, the fault detection time is recorded and the protection start signal is generated.

[0031] In one embodiment, a feeder protection method for a single-phase combined in-phase power supply system is provided. The single-phase combined in-phase power supply system includes an in-phase compensation device and a feeder. The method includes the following steps: The system monitors the voltage and current signals at the output of each feeder in the traction substation of a single-phase combined in-phase power supply system in real time, and performs fault detection and judgment based on the current signals. Specifically, it obtains the instantaneous current value at the current sampling point based on the feeder output current signal acquired through real-time monitoring. The instantaneous current value at the corresponding sampling point before a power frequency cycle And calculate the current surge according to the following formula. : in, This refers to the sudden change in current. This represents the instantaneous current value at the current sampling point. Let N be the instantaneous current value at the sampling point one power frequency cycle prior, and N be the number of sampling points within one power frequency cycle. The current abrupt change... Compared with the preset start-up threshold current value Perform a comparison and judgment, when When a suspected fault is detected in the traction network, the moment of fault detection is recorded. And generate a protection start signal. Preferably, the preset start threshold current value Use 5% to 10% of the rated feeder current to adapt to high-resistance fault scenarios.

[0032] It should be noted that the aforementioned current surge amount Calculated by the difference of sampled values ​​from adjacent power frequency cycles within the same channel, it has a natural suppression effect on normal load fluctuations, but is highly sensitive to current surges caused by short-circuit faults. The preset starting threshold current value is used. Setting the value to be higher than the normal load fluctuation level but lower than the minimum current change during a fault, especially taking 5% to 10% of the rated feeder current, can both avoid false starts during normal operation and sensitively detect current changes caused by high-resistance faults. This enables rapid fault detection while ensuring reliability and provides an accurate time reference for subsequent active detection processes.

[0033] After generating the protection start signal, the protection start signal is sent to the in-phase compensation device, so that the in-phase compensation device can base its response on the protection start signal and the fault detection time. Output the detection excitation signal to the electrical connection point of the feeder. It should be noted that since the connection of the in-phase compensation device will change the distribution characteristics of the fault electrical quantity, traditional passive protection is difficult to accurately determine the fault. However, by actively injecting the detection excitation signal, a controllable transient response can be triggered in the scenario where the in-phase compensation device is connected, creating conditions for subsequent accurate fault identification.

[0034] Next, transient current signals at both ports of the feeder are synchronously acquired based on the detection excitation signal, and fault identification is performed based on these transient current signals to obtain the fault identification result. It should be noted that when the detection excitation signal propagates along the feeder, if the fault is located between the two ports, the transient current signals at both ports will show a significant difference; if the fault is located outside the two ports, the difference in the transient current signals at both ports will be smaller. Therefore, by extracting features and comparing differences in the transient current signals at the two ports of the feeder, it is possible to accurately determine whether the fault is located within the protected feeder section.

[0035] Finally, a protection action command is generated based on the fault identification result, enabling the single-phase combined in-phase power supply system to perform feeder protection based on the protection action command. For example, only the circuit breakers at both ends of the faulty feeder are tripped, resulting in the feeder protection outcome. Therefore, when a fault occurs between the two ends of a feeder, the faulty feeder can be accurately and selectively isolated, effectively improving the selectivity and reliability of feeder protection in the single-phase combined in-phase power supply system.

[0036] Further, the step of sending the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time, includes: The protection start signal is sent to the in-phase compensation device so that the in-phase compensation device enters the fault active detection mode based on the protection start signal and determines the detection excitation signal parameters based on the fault active detection mode. Based on the detection excitation signal parameters, a detection excitation signal is generated, and based on the detection excitation signal and the preset basic current limiting control signal, the current reference command is reconstructed to obtain the instantaneous reference command for the output current. The detection start time is determined based on the fault perception time and the preset detection delay, so that the in-phase compensation device outputs the detection excitation signal to the electrical connection point of the feeder based on the detection start time and the instantaneous reference command of the output current.

[0037] In this embodiment, a protection start signal is sent to the in-phase compensation device, causing it to enter an active fault detection mode and determine the detection excitation signal parameters. Based on these parameters, a detection excitation signal is generated and reconstructed with a preset basic current limiting control signal to form an instantaneous output current reference command. Simultaneously, a detection start time is determined based on the fault perception time and a preset detection delay. The in-phase compensation device then outputs the detection excitation signal to the electrical connection point of the feeder according to this start time and the instantaneous output current reference command. By reconstructing the detection excitation signal and the preset basic current limiting control signal into an instantaneous output current reference command, the in-phase compensation device simultaneously outputs the detection excitation signal and maintains the basic current limiting function in active fault detection mode. The detection start time, determined based on the fault perception time and the preset detection delay, maintains a fixed timing difference between the output of the detection excitation signal and the fault perception time, thus preventing the detection excitation signal from overlapping with the transient signal of a natural fault in the time domain. This ensures a clear excitation source when subsequently acquiring transient current signals based on the detection excitation signal, improving the reliability and accuracy of fault diagnosis.

[0038] Further, the detection excitation signal is a short-time coded pulse perturbation sequence; the step of determining the detection excitation signal parameters based on the active fault detection mode, and generating the detection excitation signal based on the detection excitation signal parameters, includes: The round-trip time of the traveling wave is obtained based on the pre-acquired feeder length and the pre-acquired traveling wave propagation speed; The pulse width is obtained based on the traveling wave round-trip time and a preset empirical coefficient, and the pulse interval is determined based on the pulse width; The detection excitation signal parameters are obtained based on the preset injection amplitude, the preset number of pulse pairs, the pulse width, and the pulse interval. The short-time coded pulse perturbation sequence is generated based on the detection excitation signal parameters.

[0039] In this embodiment, the round-trip time of the traveling wave is obtained based on the pre-acquired feeder length and traveling wave propagation speed. Then, the pulse width is obtained and the pulse interval is determined based on this round-trip time and a preset empirical coefficient. Finally, the detection excitation signal parameters are obtained based on a preset injection amplitude, a preset number of pulse pairs, the pulse width, and the pulse interval, generating a short-time coded pulse disturbance sequence. Since the pulse width is set according to the round-trip time and the preset empirical coefficient, the duration of a single pulse in the feeder covers the round-trip process of the traveling wave, avoiding overlap between the reflected wave and the incident wave in the time domain. The pulse interval is determined by the pulse width, ensuring no mutual interference between adjacent pulses. The preset injection amplitude, the preset number of pulse pairs, the pulse width, and the pulse interval jointly constrain the time-domain waveform characteristics of the short-time coded pulse disturbance sequence, giving the sequence a recognizable coded structure. Therefore, when acquiring transient current signals at the dual ports of the feeder, the detection response component can be accurately extracted from background noise and fault transients, improving the reliability and anti-interference capability of fault diagnosis based on transient current signals.

[0040] In one embodiment, sending the protection start signal to the in-phase compensation device so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time specifically includes: the protection start signal is sent in real time to the local controller of the in-phase compensation device (CPD) via the substation internal communication network; after receiving the protection start signal, the CPD controller switches its operating mode from normal operation compensation mode to fault active detection mode within a preset very short time, and determines the detection excitation signal parameters based on the fault active detection mode.

[0041] The detection excitation signal is a short-time coded pulse perturbation sequence, and its parameters are determined as follows: the round-trip time of the traveling wave is obtained based on the pre-acquired feeder length L and traveling wave propagation speed v. For example, the feeder length L is 40km and the traveling wave propagation speed v is v. Take 2.8 × 10 8 m / s; the single pulse width is obtained based on the traveling wave round-trip time and a preset empirical coefficient λ. ,Right now ;in Take 1.5; determine the pulse interval based on the pulse width. , Pick The amplitude is 1.5 times that of the rated output current of the CPD. The injection amplitude is 5% of the rated output current of the CPD, and the preset number of pulse pairs is 2 to 6. This obtains the detection excitation signal parameters and generates an coded sequence of alternating positive and negative pulse injections. Then, a detection excitation signal is generated based on the detection excitation signal parameters, and this detection excitation signal is reconstructed with the preset basic current limiting control signal to obtain the instantaneous reference command for the output current, that is, the detection excitation signal is superimposed on the basic current limiting control signal. At the same time, based on the fault detection moment... and preset detection delay The start time of the probe was determined to be ,in satisfy ≤2ms, so that the CPD controller, based on the detection start time and the instantaneous reference command of the output current, outputs the short-time coded pulse disturbance sequence as the detection excitation signal to the electrical connection point of the feeder.

[0042] It should be noted that the pulse width Based on the round-trip time of the traveling wave and the preset empirical coefficient set up, Setting it to 1.5 ensures that the duration of a single pulse in the feeder fully covers the round-trip process of the traveling wave along the entire length of the feeder, thus avoiding the impact on signal identification caused by the time-domain overlap of the reflected and incident waves; pulse interval Pick The amplitude is 1.5 times that of the standard pulse, ensuring effective temporal separation of response signals from adjacent pulse pairs and avoiding mutual interference. This makes the encoded sequence unique in the time domain, facilitating reliable identification via template matching algorithms. The injection amplitude is selected as 5% of the CPD's rated output current. This reasonable selection ensures that the generated transient detection current signal is significantly higher than the measurement noise level, guaranteeing a high signal-to-noise ratio. Simultaneously, it avoids significant fluctuations in the traction network voltage to maintain normal locomotive load operation and prevents malfunctions of other protection devices. A preset detection delay is also included. With a pulse width of ≤2ms, combined with pulse width, pulse interval, and number of pulse pairs, the entire process of fault detection, signal detection, and fault diagnosis can be completed within 10ms after a fault occurs, meeting the stringent speed requirements of the feeder main protection. By reconstructing the detection excitation signal and the preset basic current limiting control signal into an instantaneous reference command for the output current, the CPD, in active fault detection mode, not only outputs the detection excitation signal but also maintains the basic current limiting function, ensuring the safe operation of the device itself and the system. (Based on fault perception time...) Based on the preset detection delay Determining the detection start time ensures that the injection of the detection excitation signal and the transient signal of the natural fault maintain a fixed timing difference in the time domain, avoiding their overlap. This ensures that the transient current signal obtained based on the detection excitation signal has a clear excitation source, further improving the reliability and accuracy of fault diagnosis.

[0043] Furthermore, the fault determination based on the transient current signal to obtain the fault determination result includes: The power frequency background component is eliminated based on the transient current signal to obtain a two-terminal transient current increment signal; The dual-end detection response signal is obtained based on a preset sliding cross-correlation algorithm, a preset theoretical detection waveform, and the dual-end transient current increment signal. Based on the dual-end detection response signal, a difference feature vector is constructed, and fault discrimination is performed based on the difference feature vector to obtain the fault discrimination result.

[0044] In this embodiment, a two-terminal transient current increment signal is obtained by eliminating the power frequency background component based on the transient current signal. Then, a two-terminal detection response signal is obtained from the increment signal based on a preset sliding cross-correlation algorithm and a preset theoretical detection waveform. Finally, a difference feature vector is constructed based on the response signal for fault identification. Eliminating the power frequency background component can separate the normal compensation current of the in-phase compensation device and the load power frequency current, retaining only the transient increment caused by the detection excitation, avoiding power frequency interference in transient feature extraction. The sliding cross-correlation algorithm uses the theoretical detection waveform as a template to match segment by segment in the two-terminal increment signal, accurately extracting the response waveform segment that is time-synchronized with the detection sequence, ensuring that the two-terminal signals strictly correspond to the same detection excitation. A difference feature vector is constructed based on the two-terminal detection response signal, quantifying the difference between the two-terminal responses from multiple dimensions such as instantaneous amplitude, energy distribution, and correlation. This makes the essential asymmetry of the two-terminal response during faults within the zone and the symmetry of the through current during faults outside the zone form distinguishable quantitative features, thereby improving the fault identification accuracy.

[0045] In one embodiment, while the CPD actively injects the detection sequence, current detection devices installed at both ends of the protected feeder (i.e., the feeder outlet M end and the feeder end N end) synchronously collect transient current signals at both ends of the feeder, with a sampling frequency of not less than 10kHz (i.e., sampling interval ≤100μs). The sampling times of the M end and the N end are strictly synchronized through a time synchronization network within the substation. The time synchronization network can be an IEEE 1588 Precision Time Protocol (PTP) or a Global Positioning System (GPS) / BeiDou Navigation Satellite System timing signal, thereby ensuring the time scale consistency of the signals at both ends.

[0046] The current signals acquired at the M and N terminals are processed to extract the detection feature components. First, adaptive power frequency component elimination is performed: the power frequency fundamental component and the compensation current component during normal CPD operation are treated as background components and eliminated using adaptive notch filtering based on a sliding data window or time-varying fundamental parameter estimation method based on least squares fitting, while retaining the transient current increment caused by the detection excitation signal. and .

[0047] It should be noted that this embodiment can remove the normal compensation current of the CPD and the load power frequency current by eliminating the power frequency background component, and only retain the transient increment caused by the detection excitation, thereby avoiding the interference of power frequency quantity on transient feature extraction.

[0048] Secondly, the detection signal is extracted: using the theoretical waveform of the injected detection sequence as a reference template, the transient current increment is extracted through sliding cross-correlation calculation. and Accurately extract the detection response waveform segment that is time-synchronized with the detection sequence. and The sliding cross-correlation operation is performed on the signal sequence. Upward sliding template sequence And calculate each sliding position Normalized cross-correlation coefficients The calculation formula is as follows: Where k is the sliding offset index, representing the starting position of the template in the signal sequence; The length of the template sequence. The length of the signal sequence; The mean of the template sequence. This represents the mean of the signal sequence within the current window. Normalized cross-correlation coefficient. The value range of is [-1, 1], where close to 1 indicates a strong positive correlation, i.e., similar waveforms and consistent polarity; close to -1 indicates a strong negative correlation; and close to 0 indicates no correlation. In this embodiment, by setting an appropriate correlation coefficient threshold, the detection response waveform segment can be strictly separated from the non-detection period, ensuring that only the response signal caused by the detection excitation is processed subsequently, eliminating any interference from non-detection excitations.

[0049] Then, using the synchronization time stamp information of the M and N terminals, the probe response waveform segments extracted from both ends are... and Alignment is performed point-by-point on a unified time axis. Then, a difference feature vector is constructed based on the aligned dual-end probe response waveform segments, and fault discrimination is performed based on the difference feature vector to obtain the fault discrimination result.

[0050] It should be noted that the sliding cross-correlation algorithm uses the theoretical detection waveform as a template to match segment by segment in the double-ended incremental signal, which can accurately extract the response waveform segment that is synchronized with the detection sequence in time, ensuring that the double-ended signals strictly correspond to the same detection excitation. Based on the double-ended response signal, a difference feature vector is constructed, which can quantify the difference between the double-ended responses from multiple dimensions such as instantaneous amplitude, energy distribution and correlation. This makes the essential asymmetry of the double-ended response during faults within the zone and the symmetry of the through current during faults outside the zone form distinguishable quantitative features, thereby effectively improving the accuracy and reliability of fault identification.

[0051] Further, the difference feature vector includes an instantaneous level difference index, an effective value level difference index, and a correlation level difference index; the fault discrimination based on the difference feature vector to obtain the fault discrimination result includes: The dual-end differential current value and dual-end suppression current value are obtained based on the dual-end detection response signal; Based on the aforementioned two-terminal difference current value and two-terminal suppression current value, instantaneous level difference index, effective value level difference index, and correlation level difference index are constructed. Based on the effective value level difference index and the preset effective value level difference threshold, a first-level discrimination is performed to obtain the first-level discrimination result; When the first-level discrimination result is an intra-regional fault, a second-level discrimination is performed based on the correlation level difference index and the preset correlation level difference threshold to obtain the second-level discrimination result; When the second-level discrimination result is a non-regional fault, a third-level discrimination is performed based on the instantaneous level difference index and the preset cumulative instantaneous difference threshold to obtain the third-level discrimination result; The fault identification result is determined based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result.

[0052] In this embodiment, the difference current value and the suppression current value at both ends are obtained based on the dual-end detection response signal, and instantaneous level difference index, effective value level difference index and correlation level difference index are constructed accordingly. The first level of discrimination is performed based on the effective value level difference index and the preset effective value level difference threshold. When the first level of discrimination result is an intra-zone fault, the second level of discrimination is performed based on the correlation level difference index and the preset correlation level difference threshold. When the second level of discrimination result is an intra-zone fault, the third level of discrimination is performed based on the instantaneous level difference index and the preset cumulative instantaneous difference threshold. Finally, the fault discrimination result is determined based on the first level discrimination result, the second level discrimination result or the third level discrimination result. The first level of discrimination is achieved through the effective value level difference index, which quickly distinguishes between faults within and outside the fault zone from an energy perspective. The effective value level difference index is highly sensitive to the energy difference of the two-terminal current. The second level of discrimination is achieved through the correlation level difference index, which verifies the results of the first level from a waveform similarity perspective. It distinguishes between faults within the fault zone by utilizing the low correlation of the two-terminal detection response signals and the high correlation of faults outside the fault zone. The third level of discrimination is achieved through the instantaneous level difference index, which accumulates and verifies the results of faults outside the fault zone from a time-domain waveform detail perspective. The three progressive discrimination levels complement each other, avoiding misjudgment by a single index in boundary fault scenarios and improving the reliability of fault discrimination results.

[0053] In one embodiment, after aligning the dual-end detection response signals, a difference feature vector is constructed based on the aligned dual-end detection response signals, and fault discrimination is performed based on the difference feature vector to obtain the fault discrimination result.

[0054] First, define the characteristic quantity of bidirectional differential current. Define differential current. M-end detection response signal With N-terminal detection response signal The sum of the instantaneous values, i.e. The positive direction of the N terminal is defined as the direction flowing into the feeder. The suppression current is defined. It is half the sum of the absolute values ​​of the instantaneous values ​​of the detection response signals at the M and N ends, and is used to characterize the degree of influence of the through load.

[0055] It should be noted that the above-mentioned bidirectional differential current has a specific physical meaning: under normal operating conditions before the fault occurs, the load current detected at the M and N terminals has the same amplitude and opposite direction, with zero difference; after the fault occurs, if the fault point is located inside the protected feeder, the detection response current components measured from both ends of the feeder will exhibit an essential asymmetry in amplitude and polarity.

[0056] Based on the aforementioned difference in current value at both ends and dual-terminal suppression current value Construct a difference feature vector from the following three time scales. Instantaneous level difference index Calculate using the following formula: in, It is a very small positive number, used to avoid the denominator being zero; It directly reflects the instantaneous amplitude difference between the two-end detection signals at the same moment. During faults within the area, the amplitude difference between the two-end signals is significant. The amplitude approaches 1, and the amplitudes at both ends are symmetrical during faults outside the zone or normal operation. Approaching 0.

[0057] Effective value level difference index Calculate using the following formula: in, and They are respectively and Valid value (Root Mean Square, RMS) within the probe sequence period; The overall difference between the two-terminal signals is measured from an energy perspective.

[0058] Correlation level difference index Calculate using the following formula: in, M-end detection response With N-terminal detection response The Pearson correlation coefficient is calculated as follows: When the fault occurs outside the fault zone, the two-terminal signals are different measurements of the same through current, resulting in a strong correlation and D3 approaching 0; when the fault occurs inside the fault zone, the two-terminal signals reflect two independent current components flowing towards the fault point, leading to a decreased correlation and D3 approaching 1.

[0059] After constructing the difference feature vector, based on the effective value level difference index The system performs a first-level discrimination based on the difference between the pre-set effective value level and the threshold, yielding the first-level discrimination result. When the first-level discrimination result indicates an intra-regional fault, the system is further refined based on the correlation level difference index. A second-level discrimination is performed based on the preset correlation level difference threshold to obtain the second-level discrimination result. When the second-level discrimination result is a non-intra-area fault, the instantaneous level difference index is used. A third-level discrimination is performed based on the preset cumulative instantaneous difference threshold to obtain the third-level discrimination result. Finally, the fault discrimination result is determined based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result.

[0060] It should be noted that the effective value level difference index is used. The first-level discrimination can quickly distinguish between faults within and outside the designated area based on energy levels. It exhibits high sensitivity to differences in energy between two-terminal currents; through correlation level difference index A second-level discrimination is performed, verifying the first-level results from the waveform similarity dimension. This is achieved by differentiating the signals based on the low correlation of the dual-end detection response signals during in-zone faults versus the high correlation during non-in-zone faults; and by using instantaneous level difference indices. A third level of discrimination is performed, accumulating and verifying the results of faults outside the designated area from the perspective of time-domain waveform details. These three progressive discrimination levels complement each other, effectively avoiding misjudgments by a single indicator in boundary fault scenarios, thereby improving the reliability of fault discrimination results.

[0061] Further, determining the fault discrimination result based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result includes: A preliminary fault identification result is determined based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result; When the preliminary fault identification result is an external fault, the direction coefficient of the feeder outlet end is obtained based on the dual-end detection response signal; The direction is determined based on the direction coefficient at the feeder outlet, and the fault direction determination result is obtained. The fault identification result is determined based on the fault direction determination result and the preliminary fault identification result.

[0062] In this embodiment, a preliminary fault identification result is determined based on the first-level, second-level, or third-level identification results. When the preliminary fault identification result indicates an out-of-zone fault, the direction coefficient at the feeder outlet is obtained based on the dual-end detection response signal. Then, the direction is determined based on this direction coefficient to obtain the fault direction determination result. Finally, the fault identification result is determined based on the fault direction determination result and the preliminary fault identification result. Since an out-of-zone fault only indicates that the fault point is not between the two ends of the feeder, but cannot distinguish whether the fault is located in the forward or reverse direction at the feeder outlet, the direction coefficient at the feeder outlet is calculated, and the reference flow direction of the detection current is determined using the polarity relationship of the transient components in the dual-end detection response signal, thereby clarifying the fault direction. Combining this fault direction determination result with the preliminary fault identification result not only confirms that the fault is out-of-zone but also provides specific location information, providing a directional basis for the selective coordination of adjacent feeder protection, avoiding protection maloperation or cascading tripping due to unclear direction, and further improving the reliability of feeder protection in the same-phase power supply system.

[0063] In one embodiment, the step of performing fault discrimination based on the difference feature vector to obtain a fault discrimination result specifically includes: first, based on the three-dimensional difference feature vector... The values ​​of each element are used to perform preliminary fault identification of the feeder fault status using hierarchical logic.

[0064] In the first level of discrimination, the effective value level difference index will be used. Difference threshold from preset effective value level If a comparison is made, If the fault is within the zone, it is initially determined to be a fault within the zone; otherwise, it is determined to be a fault outside the zone or a disturbance to normal operation. It has high sensitivity as a coarse screening criterion and can effectively cover various fault types, including high-resistance grounding.

[0065] In the second-level discrimination, when the first-level discrimination result is an intra-regional fault, the correlation level difference index is further examined. :like ,in If a threshold for the difference in correlation level is preset, it is confirmed that the fault outside the zone has been eliminated and is judged as a clear fault inside the zone; otherwise, there may be a through-current, such as a metallic short circuit outside the zone at a far end, in which case the third-level comprehensive inspection is entered.

[0066] In the third level of discrimination, for Exceeding the standard but For samples that did not meet the threshold, the instantaneous level of variability was used. Perform instantaneous discrimination and calculate the instantaneous difference within the detection sequence time period. cumulative value ,like Greater than the preset cumulative instantaneous difference threshold If the fault is within the designated area, it is still considered an in-area fault; otherwise, it is considered an out-of-area fault. Through this three-level progressive judgment, a preliminary fault determination result is obtained.

[0067] When the preliminary fault identification result is an external fault, the direction coefficient at the feeder outlet is obtained based on the dual-end detection response signal. It should be noted that an external fault only indicates that the fault point is not between the two ends of this feeder, but it cannot distinguish whether the fault is located in the positive or negative direction at the feeder outlet. By calculating the direction coefficient at the feeder outlet, the reference flow direction of the detection current is determined using the polarity relationship of the transient components in the dual-end detection response signal, thereby clarifying the fault direction.

[0068] The fault direction is determined based on the direction coefficient at the feeder outlet, resulting in a fault direction determination result. Then, the final fault identification result is determined based on the fault direction determination result and the preliminary fault identification result. It should be noted that combining the fault direction determination result with the preliminary fault identification result not only confirms that the fault is outside the fault zone but also provides specific fault location information. This provides a directional basis for the selective coordination of adjacent feeder protection, avoiding maloperation or cascading tripping due to unclear direction, thereby further improving the reliability of feeder protection in single-phase combined in-phase power supply systems.

[0069] Further, the step of generating a protection action command based on the fault determination result, so that the single-phase combined in-phase power supply system performs feeder protection based on the protection action command, and obtains the feeder protection result, includes: When the fault identification result is an intra-zone fault, a trip command is generated and sent to a preset circuit breaker, so that the preset circuit breaker isolates the fault feeder based on the trip command and generates a detection completion signal. When the fault identification result is an external fault, an external fault confirmation signal is generated, and an in-phase compensation device recovery command and a detection completion signal are generated based on the external fault confirmation signal. Based on the detection completion signal, the in-phase compensation device is controlled to stop outputting the detection excitation signal; Based on the fault determination result within the zone, the in-phase compensation device is switched to current-limiting operation mode, or based on the fault determination result outside the zone and the recovery command of the in-phase compensation device, the in-phase compensation device is switched to normal operation compensation mode, thereby obtaining the feeder protection result.

[0070] In this embodiment, when the fault determination result is an intra-zone fault, a trip command is generated and sent to a preset circuit breaker to isolate the faulty feeder, and a detection completion signal is generated simultaneously. When the determination result is an extra-zone fault, an extra-zone fault confirmation signal, a phase compensation device recovery command, and a detection completion signal are generated. Based on the detection completion signal, the phase compensation device is controlled to stop outputting the detection excitation signal. Based on the intra-zone fault determination result, the phase compensation device is switched to current-limiting operation mode. Based on the extra-zone fault determination result and the phase compensation device recovery command, the phase compensation device is switched to normal operation compensation mode, thereby obtaining the feeder protection result. When a fault occurs within the protection zone, a trip command is generated to quickly isolate the faulty feeder using a preset circuit breaker. Simultaneously, the in-phase compensation device switches to current-limiting operation mode to prevent the fault current from continuously impacting the system. When a fault occurs outside the protection zone, an external fault confirmation signal and a recovery command for the in-phase compensation device are generated, causing the in-phase compensation device to switch to normal operation compensation mode to prevent power outages caused by false tripping of non-faulty feeders. Based on the detection completion signal, the in-phase compensation device is controlled to stop outputting detection excitation signals, ensuring the orderly termination of the active detection process. This achieves coordinated action between protection actions and compensation mode switching, improving the speed of feeder protection results and the stability of system operation.

[0071] In one embodiment, generating a protection action command based on the fault identification result, so that the single-phase combined in-phase power supply system performs feeder protection based on the protection action command to obtain the feeder protection result, specifically includes: when the fault identification result is an intra-zone fault, the protection device issues a trip command to a preset circuit breaker after a set delay, so that the preset circuit breaker isolates the faulty feeder based on the trip command. Simultaneously, the protection device sends a detection completion signal to the CPD controller.

[0072] When the fault identification result is an external fault, an external fault confirmation signal is generated, and the fault direction is further determined. Specifically, the direction coefficient at the M end is defined. The calculation formula is as follows: in, For the M-end detection response signal, This is the response signal detected at the N-terminal. If... >0 indicates that the fault is located in the positive direction interval of the M end, thus confirming that the fault is located in the segment outside the positive direction region; if A value less than 0 indicates that the fault is located in the opposite direction of the M-end, thus confirming that the fault is located outside the reverse zone. This yields the fault direction determination result. Based on this, a recovery command for the in-phase compensation device and a detection completion signal are generated.

[0073] It should be noted that the term "outside-zone fault" only indicates that the fault point is not between the two ports of this feeder. By calculating the direction coefficient at the feeder outlet and using the polarity relationship of the transient components in the two-terminal detection response signal, the reference flow direction of the detection current is determined, thereby clarifying the fault direction. Combining this fault direction determination result with the outside-zone fault confirmation signal can both confirm that the fault is outside the zone and provide specific fault location information. This provides a directional basis for the selective coordination of adjacent feeder protection, avoiding protection maloperation or cascading tripping due to unclear direction.

[0074] Based on the detection completion signal, the in-phase compensation device stops outputting the detection excitation signal. Specifically, the CPD automatically exits the active fault detection mode after receiving the detection completion signal or after the detection mode duration reaches a preset upper limit. It should be noted that the preset upper limit is exemplarily set to 20ms to ensure that the entire detection-detection-discrimination process is completed quickly after a fault occurs.

[0075] After the CPD exits the active fault detection mode, it switches its operating mode based on different fault identification results. If the feeder protection has tripped, indicating an internal fault, the CPD switches to current-limiting operation mode. The current-limiting value... According to the CPD rated current The 15% setting balances multiple constraints, including the safe operating area of ​​the Insulated Gate Bipolar Transistor (IGBT), minimum reactive power support requirements, and prevention of maloperation of robust feeder protection. This is achieved through current inner-loop saturation limiting. It should be noted that during an in-zone fault, a trip command is generated to quickly isolate the faulty feeder using the preset circuit breaker, while simultaneously switching the CPD to current-limiting operation mode. This prevents the fault current from continuously impacting the system and maintains necessary reactive power support.

[0076] If the feeder protection fails to operate, indicating an external fault or interference, the CPD smoothly recovers to normal operating compensation mode. Specifically, a linear slope recovery algorithm is used, meaning the CPD output current reference value is... The current value is linearly and smoothly transitioned to the target value. If there is a phase difference in the traction network voltage, a flexible grid-connected pre-synchronization control based on a phase-locked loop (PLL) is introduced to ensure a shock-free switching process. It should be noted that by generating an external fault confirmation signal and a recovery command for the in-phase compensation device when an external fault occurs, the CPD is switched to normal operation compensation mode, which can avoid power outages caused by false tripping of non-faulty feeders. The above-mentioned current limiting value and smooth transition strategy together ensure the safety of the CPD and the stability of the system during fault ride-through and recovery.

[0077] If the CPD is blocked or a trip command has been issued after a fault occurs within the feeder's fault zone, the backup protection function will be taken over by the adjacent feeder or the upstream protection. Thus, through the coordinated action of protection actions and CPD compensation mode switching, the feeder protection result is obtained, effectively improving the speed of feeder protection and the stability of system operation in single-phase combined in-phase power supply systems.

[0078] Furthermore, the feeder protection method for a single-phase combined in-phase power supply system as described above also includes: Real-time detection and acquisition of the output current value of the in-phase compensation device; When the output current value is greater than or equal to the preset power device safety limit, a detection termination signal is output to the in-phase compensation device so that the in-phase compensation device stops outputting the detection excitation signal based on the detection termination signal. Based on the detection termination signal, a preset backup protection mechanism is triggered, so that the single-phase combined in-phase power supply system performs feeder protection based on the preset backup protection mechanism, and a backup protection result is obtained.

[0079] In this embodiment, the output current value of the in-phase compensation device is detected and acquired in real time. When the output current value is greater than or equal to the preset power device safety limit, a detection termination signal is output to the in-phase compensation device. This causes the in-phase compensation device to stop outputting the detection excitation signal based on the detection termination signal, and triggers a preset backup protection mechanism based on the detection termination signal. This enables the single-phase combined in-phase power supply system to perform feeder protection based on the preset backup protection mechanism, thus obtaining backup protection results. During active detection, sudden impedance changes or control responses at the fault point may cause the output current value of the in-phase compensation device to momentarily exceed the preset power device safety limit. By detecting in real time and comparing it with the safety limit, a detection termination signal is immediately output to forcibly stop the detection excitation signal once the limit is exceeded, avoiding overcurrent damage to the power device. At the same time, the detection termination signal triggers the preset backup protection mechanism, switching the feeder protection from active detection mode to backup protection mode. This ensures that the fault can still be reliably isolated after active detection is safely withdrawn by the device. Thus, while protecting the physical safety of the power device, dual redundancy of the protection function is achieved, improving the reliability and safety of the power supply system.

[0080] One embodiment of a feeder protection method for a single-phase combined in-phase power supply system further includes a backup protection mechanism. Specifically, during the active detection process of the CPD, the CPD controller detects and acquires the output current value of the AC side of the in-phase compensation device in real time. When the transient peak value of the output current is detected to be greater than or equal to a preset power device safety limit, the backup protection mechanism is activated. When the fault is detected, a detection termination signal is output to the in-phase compensation device, so that the in-phase compensation device immediately terminates the active fault detection mode based on the detection termination signal, stops outputting the detection excitation signal, and quickly limits the current to a safe level.

[0081] It should be noted that the preset power device safety limit This corresponds to the safe operating area limit for power devices in in-phase compensation devices, such as insulated-gate bipolar transistor modules. During active detection, if the output current momentarily exceeds this safe limit due to a sudden change in impedance at the fault point or abnormal control response, real-time detection and forced termination of detection can effectively prevent damage to power devices due to overcurrent, ensuring the physical safety of the device itself.

[0082] Simultaneously, a preset backup protection mechanism is triggered based on the detection termination signal, enabling the single-phase combined in-phase power supply system to perform feeder protection based on this preset backup protection mechanism, thus obtaining backup protection results. Specifically, when the CPD terminates the active detection mode, the feeder protection automatically reverts to the backup protection mode based on natural fault quantities. This backup protection employs a coordinated strategy combining definite-time overcurrent protection and impedance protection.

[0083] The criterion for time-limit overcurrent protection is: the effective value of the feeder current. Greater than or equal to the maximum load current The protection trips when the impedance is 1.2 times the normal value and the condition persists for 1 second. Impedance protection employs a three-stage distance protection system, with impedance settings for each stage set at 80%, 120%, and 300% of the total length of the protected feeder, respectively, and includes a directional blocking function. If any of the above-mentioned definite-time overcurrent protection criteria and the three-stage impedance protection criteria are met, a trip command is issued to isolate the faulty feeder.

[0084] It should be noted that the detection termination signal triggers a preset backup protection mechanism, smoothly switching the feeder protection from active detection mode to backup protection mode. This ensures that even if active detection is disabled due to device safety reasons, the system can still reliably detect and isolate faults based on natural fault quantities, achieving dual redundancy of protection functions. This design does not rely on a single protection mechanism under any operating condition, effectively improving the power supply reliability and operational safety of single-phase combined in-phase power supply systems.

[0085] Please see Figure 2 This embodiment also provides a single-phase combined in-phase power supply system feeder protection system, including: The signal detection module is used to monitor and acquire the feeder outlet current signal in real time, and to perform fault detection and judgment based on the feeder outlet current signal. When the feeder outlet current signal meets the preset protection conditions, the fault detection time is recorded and a protection start signal is generated. The in-phase compensation device control module is used to send the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time; The fault detection module is used to synchronously acquire the transient current signal of the dual-port of the feeder based on the detection excitation signal, and to perform fault detection based on the transient current signal to obtain the fault detection result; The protection execution module is used to generate protection action commands based on the fault discrimination results, so that the single-phase combined in-phase power supply system can perform feeder protection based on the protection action commands and obtain feeder protection results.

[0086] In this embodiment, the signal detection module monitors and acquires the feeder outlet current signal in real time to perform fault detection and judgment. When the preset protection conditions are met, it records the fault detection time and generates a protection start signal. The in-phase compensation device control module sends the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the signal and the fault detection time. The fault discrimination module acquires the transient current signal of the two ports of the feeder synchronously based on the detection excitation signal and performs fault discrimination to obtain the fault discrimination result. The protection execution module generates a protection action command based on the fault discrimination result to perform feeder protection and obtain the feeder protection result. The signal detection module establishes a time reference for the fault occurrence based on the moment of fault detection, ensuring that the subsequent detection excitation signal and the transient fault process are controllable in timing. The in-phase compensation device control module switches the in-phase compensation device from normal operation mode to active detection mode, enabling the detection excitation signal to be accurately injected into the feeder electrical connection point. The fault discrimination module uses the detection excitation signal to synchronously acquire the dual-port transient current signal and performs fault discrimination based on the difference between the two-terminal transients, avoiding the electrical quantity characteristic distortion problem caused by the connection of the in-phase compensation device in traditional protection. The protection execution module generates corresponding action commands based on the results within or outside the protection zone, realizing accurate isolation of the faulty feeder or rapid restoration of the non-faulty feeder. The four modules are functionally integrated and work together to improve the selectivity and reliability of feeder protection.

[0087] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A feeder protection method for a single-phase combined in-phase power supply system, characterized in that, The single-phase combined in-phase power supply system includes an in-phase compensation device and a feeder. The method includes the following steps: Real-time monitoring and acquisition of feeder outlet current signal, and fault detection and judgment based on the feeder outlet current signal. When the feeder outlet current signal meets the preset protection conditions, the fault detection time is recorded and a protection start signal is generated. The protection start signal is sent to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time. Based on the detection excitation signal, the transient current signal of the two ports of the feeder is synchronously acquired, and the fault is determined based on the transient current signal to obtain the fault determination result; Based on the fault identification result, a protection action command is generated so that the single-phase combined in-phase power supply system can perform feeder protection based on the protection action command, thereby obtaining the feeder protection result.

2. The feeder protection method for a single-phase combined in-phase power supply system according to claim 1, characterized in that, The fault detection and determination based on the feeder outlet current signal, when the feeder outlet current signal meets the preset protection conditions, records the fault detection time and generates a protection start signal, including: The instantaneous current value at the current sampling point and the instantaneous current value at the sampling point before the power frequency cycle are obtained based on the feeder outlet current signal. The current surge is obtained based on the instantaneous current value at the current sampling point and the instantaneous current value at the sampling point before the power frequency cycle; The current surge is compared with the preset start-up threshold current value. When the current surge is greater than the preset start-up threshold current value, the fault detection time is recorded and the protection start signal is generated.

3. The feeder protection method for a single-phase combined in-phase power supply system according to claim 1, characterized in that, The step of sending the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time, includes: The protection start signal is sent to the in-phase compensation device so that the in-phase compensation device enters the fault active detection mode based on the protection start signal and determines the detection excitation signal parameters based on the fault active detection mode. Based on the detection excitation signal parameters, a detection excitation signal is generated, and based on the detection excitation signal and the preset basic current limiting control signal, the current reference command is reconstructed to obtain the instantaneous reference command for the output current. The detection start time is determined based on the fault perception time and the preset detection delay, so that the in-phase compensation device outputs the detection excitation signal to the electrical connection point of the feeder based on the detection start time and the instantaneous reference command of the output current.

4. The feeder protection method for a single-phase combined in-phase power supply system according to claim 3, characterized in that, The detection excitation signal is a short-time coded pulse perturbation sequence; the step of determining the detection excitation signal parameters based on the active fault detection mode, and generating the detection excitation signal based on the detection excitation signal parameters, includes: The round-trip time of the traveling wave is obtained based on the pre-acquired feeder length and the pre-acquired traveling wave propagation speed; The pulse width is obtained based on the traveling wave round-trip time and a preset empirical coefficient, and the pulse interval is determined based on the pulse width; The detection excitation signal parameters are obtained based on the preset injection amplitude, the preset number of pulse pairs, the pulse width, and the pulse interval. The short-time coded pulse perturbation sequence is generated based on the detection excitation signal parameters.

5. The feeder protection method for a single-phase combined in-phase power supply system according to claim 1, characterized in that, The fault discrimination based on the transient current signal, to obtain the fault discrimination result, includes: The power frequency background component is eliminated based on the transient current signal to obtain a two-terminal transient current increment signal; The dual-end detection response signal is obtained based on a preset sliding cross-correlation algorithm, a preset theoretical detection waveform, and the dual-end transient current increment signal. Based on the dual-end detection response signal, a difference feature vector is constructed, and fault discrimination is performed based on the difference feature vector to obtain the fault discrimination result.

6. A feeder protection method for a single-phase combined in-phase power supply system according to claim 5, characterized in that, The difference feature vector includes an instantaneous difference index, an effective value difference index, and a correlation-level difference index; the fault discrimination based on the difference feature vector to obtain the fault discrimination result includes: The dual-end differential current value and dual-end suppression current value are obtained based on the dual-end detection response signal; Based on the aforementioned two-terminal difference current value and two-terminal suppression current value, instantaneous level difference index, effective value level difference index, and correlation level difference index are constructed. Based on the effective value level difference index and the preset effective value level difference threshold, a first-level discrimination is performed to obtain the first-level discrimination result; When the first-level discrimination result is an intra-regional fault, a second-level discrimination is performed based on the correlation level difference index and the preset correlation level difference threshold to obtain the second-level discrimination result; When the second-level discrimination result is a non-regional fault, a third-level discrimination is performed based on the instantaneous level difference index and the preset cumulative instantaneous difference threshold to obtain the third-level discrimination result; The fault identification result is determined based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result.

7. A feeder protection method for a single-phase combined in-phase power supply system according to claim 6, characterized in that, Determining the fault identification result based on the first-level identification result, the second-level identification result, or the third-level identification result includes: A preliminary fault identification result is determined based on the first-level discrimination result, the second-level discrimination result, or the third-level discrimination result; When the preliminary fault identification result is an external fault, the direction coefficient of the feeder outlet end is obtained based on the dual-end detection response signal; The direction is determined based on the direction coefficient at the feeder outlet, and the fault direction determination result is obtained. The fault identification result is determined based on the fault direction determination result and the preliminary fault identification result.

8. A feeder protection method for a single-phase combined in-phase power supply system according to claim 1, characterized in that, The generation of protection action commands based on the fault identification results, enabling the single-phase combined in-phase power supply system to perform feeder protection based on the protection action commands, and obtaining feeder protection results, includes: When the fault identification result is an intra-zone fault, a trip command is generated and sent to a preset circuit breaker, so that the preset circuit breaker isolates the fault feeder based on the trip command and generates a detection completion signal. When the fault identification result is an external fault, an external fault confirmation signal is generated, and an in-phase compensation device recovery command and a detection completion signal are generated based on the external fault confirmation signal. Based on the detection completion signal, the in-phase compensation device is controlled to stop outputting the detection excitation signal; Based on the fault determination result within the zone, the in-phase compensation device is switched to current-limiting operation mode, or based on the fault determination result outside the zone and the recovery command of the in-phase compensation device, the in-phase compensation device is switched to normal operation compensation mode, thereby obtaining the feeder protection result.

9. A feeder protection method for a single-phase combined in-phase power supply system according to claim 1, characterized in that, Also includes: Real-time detection and acquisition of the output current value of the in-phase compensation device; When the output current value is greater than or equal to the preset power device safety limit, a detection termination signal is output to the in-phase compensation device so that the in-phase compensation device stops outputting the detection excitation signal based on the detection termination signal. Based on the detection termination signal, a preset backup protection mechanism is triggered, so that the single-phase combined in-phase power supply system performs feeder protection based on the preset backup protection mechanism, and a backup protection result is obtained.

10. A feeder protection system for a single-phase combined in-phase power supply system, characterized in that, include: The signal detection module is used to monitor and acquire the feeder outlet current signal in real time, and to perform fault detection and judgment based on the feeder outlet current signal. When the feeder outlet current signal meets the preset protection conditions, the fault detection time is recorded and a protection start signal is generated. The in-phase compensation device control module is used to send the protection start signal to the in-phase compensation device, so that the in-phase compensation device outputs a detection excitation signal to the electrical connection point of the feeder based on the protection start signal and the fault detection time; The fault detection module is used to synchronously acquire the transient current signal of the dual-port of the feeder based on the detection excitation signal, and to perform fault detection based on the transient current signal to obtain the fault detection result; The protection execution module is used to generate protection action commands based on the fault discrimination results, so that the single-phase combined in-phase power supply system can perform feeder protection based on the protection action commands and obtain feeder protection results.

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