Multi-impedance multi-time-limit distance protection method and system with remote backup function

Abstract

The invention discloses a multi-impedance multi-time-limit distance protection method and system with a remote backup function, and the method comprises the steps: adding four sections of remote backup grounding distance protection on the basis of the original grounding distance protection of a line; when a single-phase earth fault occurs in a lower-stage line and the duration exceeds the self-protection action time limit of the lower-stage line, the measured impedance is sequentially compared with the impedance range of each section of remote backup grounding distance, and if the impedance range of a certain section is matched, the grounding protection action of the section is performed to remove the fault after the action time of the corresponding section; on the basis of original phase distance protection, four sections of remote backup phase distance protection are added; and when the lower-stage line has an inter-phase fault and the duration exceeds the self-protection action time limit of the lower-stage line, sequentially comparing the measured impedance with each section of far backup inter-phase distance protection impedance range, and if a certain section of impedance range is matched, performing inter-phase protection action on the section to remove the fault after the action time of the corresponding section. According to the invention, the adaptability of the protection device in the aspect of protection configuration under some extreme conditions can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power transformation, and particularly relates to a multi-impedance multi-time limit distance protection method and system with a remote backup function. BACKGROUND

[0002] At present, as the first line of defense for ensuring the safety of the power grid, the accurate and rapid action of relay protection is crucial for isolating faults and controlling the spread of accidents. With the accelerated construction of new power systems, the widespread application of new technologies, the increasingly complex structure of the power grid, and the increasing operating pressure, the relay protection profession is also facing severe challenges. The current national standard "Technical Regulations for Relay Protection and Safety Automatic Device" (GB / T 14285-2023) stipulates that for lines with a voltage level of 220 kV and above, the principle of near backup protection should be adopted, and the line backup protection should be designed according to the full length of the line, without considering cooperation with lower-level lines. The protection configuration principle of "heavy main and simple backup" has adaptability risks in some extreme cases. According to the current relay protection setting regulations, the power grid above 220 kV is generally configured according to the near backup principle. When the line protection cannot act due to power loss, failure, or other reasons, there is no reliable remote backup to remove the fault.

[0003] The existing technical specifications stipulate that the I section of the distance protection is set to avoid faults on the opposite side of the line, the II section is preferentially set to faults at the end of the line, and the III section is generally set to the minimum impedance corresponding to the maximum accident overload current of the line. Due to the complex structure of the power grid and the variable operating mode, it is difficult to coordinate the setting between the values. The backup protection of the line cannot function as remote backup protection. The current power grid has a complex primary network structure, and many lines have branches. Due to the increase in measurement impedance caused by the increase in current, the distance protection cannot function as remote backup protection.

[0004] If the line protection maintenance is withdrawn and misoperation such as the closing of the ground wire by the operation and maintenance personnel occurs, the line loses the near backup protection function, other equipment at the station is not configured with redundant backup protection, which exceeds the current 220 kV and above power grid relay protection defense standard, and cannot quickly and reliably remove the fault, which will cause multiple substations to lose voltage and expand the scope of the accident. SUMMARY

[0005] Due to the increasing complexity of the power grid structure and the variable operating mode, it is difficult to coordinate the setting between the values. To solve the technical problem that the current backup protection cannot function as remote backup protection, the application provides a backup protection improvement method and system. Specifically, it includes a multi-impedance multi-time limit distance protection method and system with a remote backup function.

[0006] To achieve the purpose of the application, the following technical solutions are specifically adopted.

[0007] The application discloses a multi-impedance multi-time-limit distance protection method with a remote backup function. On the basis of the original ground distance protection of the line, four remote backup ground distance protections are added, including a remote backup ground I section, a remote backup ground II section, a remote backup ground III section and a remote backup ground IV section. When a single-phase ground fault occurs in the next stage line, the line protection device collects the voltage and current signals of the fault point, calculates the measured impedance observed from the installation of the line protection, and monitors the fault duration time. On the basis of the original phase-to-phase distance protection, four remote backup phase-to-phase distance protections are added, including a remote backup phase-to-phase I section, a remote backup phase-to-phase II section, a remote backup phase-to-phase III section and a remote backup phase-to-phase IV section. When a phase-to-phase fault occurs in the next stage line, the line protection device collects the voltage and current signals of the fault point, calculates the measured impedance observed from the installation of the line protection, and monitors the fault duration time.

[0008] Further preferably, When the four remote backup ground distance protections and the four remote backup phase-to-phase distance protections are added, the following setting values need to be added on the basis of the original protection setting values of the line, including remote backup ground distance stage setting values, remote backup ground distance times, remote backup phase-to-phase distance stage setting values and remote backup phase-to-phase distance times.

[0009] Further preferably, In the four remote backup ground distance protections, the impedance ranges of the remote backup ground distance protections in each section increase in a stepped manner, and specifically are as follows: The impedance range of the first remote backup grounding distance section is the sum of the original grounding III section impedance range of the line and the remote backup grounding distance stage setting value; the impedance range of the second remote backup grounding distance section is the sum of the original grounding III section impedance range of the line and 2 times the remote backup grounding distance stage setting value; the impedance range of the third remote backup grounding distance section is the sum of the original grounding III section impedance range of the line and 3 times the remote backup grounding distance stage setting value; and the impedance range of the fourth remote backup grounding distance section is the sum of the original grounding III section impedance range of the line and 4 times the remote backup grounding distance stage setting value.

[0010] Further preferably, In the four-section remote backup grounding distance protection, the action time of each section of the remote backup grounding distance protection is increased in steps, and specifically: The first remote backup grounding distance section time is the original grounding III section remote backup grounding distance time of the line plus the remote backup grounding distance time; the second remote backup grounding distance section time is the original grounding III section remote backup grounding distance time of the line plus 2 times the remote backup grounding distance time; the third remote backup grounding distance section time is the original grounding III section remote backup grounding distance time of the line plus 3 times the remote backup grounding distance time; and the fourth remote backup grounding distance section time is the original grounding III section remote backup grounding distance time of the line plus 4 times the remote backup grounding distance time.

[0011] Further preferably, In the four-section remote backup grounding distance protection, the action condition of each section of the remote backup grounding distance protection needs to meet the following requirements: The corresponding section of the remote backup grounding distance protection quadrilateral impedance characteristic meets; The impedance direction meets when the corresponding section of the zero sequence power direction or the zero sequence voltage is less than 1V; The corresponding section of the zero sequence current is greater than the original grounding III section setting value of the line; The action time of the corresponding section of the remote backup grounding distance protection meets; The corresponding section of the sequence current fault phase selection is correctly selected; The corresponding section of the remote backup grounding distance protection meets the fault phase opening condition.

[0012] Further preferably, The criterion for the fault phase opening condition meeting in the remote backup grounding distance protection is specifically:

[0013] Among them, , , The amplitudes of the zero sequence, positive sequence and negative sequence currents, respectively; The fault phase voltage amplitude; The included angle between the fault phase voltage and the fault phase current; is an angle between the positive sequence voltage and the positive sequence phase current; is a positive sequence voltage amplitude; the (a), (b), (c) conditions in the formula are a logical or relationship, and one of them is satisfied, i.e. a fault phase opening condition in the remote backup grounding distance protection is satisfied.

[0014] Further preferably, In the four-section remote backup phase-to-phase distance protection, the impedance ranges of the respective sections of the remote backup phase-to-phase distance protection are in a stepped increase, and specifically: The remote backup phase-to-phase I-section impedance range is a sum of the original phase-to-phase III-section impedance range of the current line and the remote backup phase-to-phase distance stage setting value; the remote backup phase-to-phase II-section range is a sum of the original phase-to-phase III-section impedance range of the current line and 2 times the remote backup phase-to-phase distance stage setting value; the remote backup phase-to-phase III-section range is a sum of the original phase-to-phase III-section impedance range of the current line and 3 times the remote backup phase-to-phase distance stage setting value; and the remote backup phase-to-phase IV-section range is a sum of the original phase-to-phase III-section impedance range of the current line and 4 times the remote backup phase-to-phase distance stage setting value.

[0015] Further preferably, In the four-section remote backup phase-to-phase distance protection, the action times of the respective sections of the remote backup phase-to-phase distance protection are in a stepped increase, and specifically: The remote backup phase-to-phase I-section time is a sum of the original phase-to-phase III-section remote backup phase-to-phase distance time of the current line and the remote backup phase-to-phase distance time; the remote backup phase-to-phase II-section time is a sum of the original phase-to-phase III-section remote backup phase-to-phase distance time of the current line and 2 times the remote backup phase-to-phase distance time; the remote backup phase-to-phase III-section time is a sum of the original phase-to-phase III-section remote backup phase-to-phase distance time of the current line and 3 times the remote backup phase-to-phase distance time; and the remote backup phase-to-phase IV-section time is a sum of the original phase-to-phase III-section remote backup phase-to-phase distance time of the current line and 4 times the remote backup phase-to-phase distance time.

[0016] Further preferably, In the four-section remote backup phase-to-phase distance protection, the action conditions of the respective sections of the remote backup phase-to-phase distance protection need to satisfy the following requirements simultaneously: The corresponding section of the remote backup phase-to-phase distance protection satisfies the phase circle impedance characteristic; The corresponding section of the fault phase-to-phase load line is satisfied; The corresponding section of the remote backup phase-to-phase distance protection satisfies the fault phase-to-phase opening condition; The corresponding section of the remote backup phase-to-phase distance protection satisfies the action time.

[0017] Further preferably, The criterion that the fault phase-to-phase opening condition is satisfied in the remote backup phase-to-phase distance protection is specifically:

[0018] Wherein, , , The amplitude of the zero sequence, positive sequence and negative sequence current respectively; It is the interphase voltage of two fault phases; It is the included angle between the interphase voltage of two fault phases and the interphase current; It is the included angle between the positive sequence voltage and the positive sequence phase current; It is the amplitude of the positive sequence phase voltage; the (a), (b) conditions in the formula are the logical or relationship, and one of them is satisfied, that is, the fault phase opening condition in the remote backup interphase distance protection is satisfied.

[0019] Another aspect of the present application discloses a multi-impedance multi-time limit distance protection system with remote backup function based on the foregoing method, comprising a remote backup ground distance protection addition module, a remote backup ground distance protection action judgment module, a remote backup interphase distance protection addition module and a remote backup interphase distance protection action judgment module; The remote backup ground distance protection addition module increases four segments of remote backup ground distance protection, including remote backup ground I segment, remote backup ground II segment, remote backup ground III segment and remote backup ground IV segment, on the basis of the original ground distance protection of the line; The remote backup ground distance protection action judgment module, when a single-phase ground fault occurs in the next level line, the voltage and current signals of the fault point are collected by the protection device of the line, the measured impedance observed from the installation place of the line protection is calculated, and the fault duration is monitored, if the fault duration exceeds the action time limit of the protection of the lower level line, the measured impedance is compared with the impedance range of the original ground III segment of the line, the impedance range of the remote backup ground I segment, the impedance range of the remote backup ground II segment, the impedance range of the remote backup ground III segment and the impedance range of the remote backup ground IV segment in turn, if it matches the impedance range of a segment, the fault is removed by the action of the ground protection of the corresponding segment after the action time of the segment; The remote backup interphase distance protection addition module increases four segments of remote backup interphase distance protection, including remote backup interphase I segment, remote backup interphase II segment, remote backup interphase III segment and remote backup interphase IV segment, on the basis of the original interphase distance protection; The far backup phase-to-phase distance protection action judging module, when a phase-to-phase fault occurs in the next stage line, the line protection device collects the voltage and current signals of the fault point, calculates the measured impedance observed from the installation of the line protection, and monitors the fault duration, if the fault duration exceeds the action time limit of the lower line self-protection, the measured impedance is compared with the impedance range of the original phase-to-phase III section of the line, the impedance range of the far backup phase-to-phase I section, the impedance range of the far backup phase-to-phase II section, the impedance range of the far backup phase-to-phase III section, and the impedance range of the far backup phase-to-phase IV section in turn, if it matches the impedance range of a section, after the action time of the corresponding section, the fault is removed by the action of the section phase-to-phase protection.

[0020] Compared with the prior art, the present application has the following beneficial technical effects: The multi-impedance multi-time limit distance protection method with far backup function provided by the present application plays a far backup role when a fault occurs in the next stage line under the condition of complex power grid structure and increased current, and the protection range is the end of the next stage line. By increasing the far backup distance related setting value, the distance impedance range is increased based on the original distance III section, which can cope with faults under various operating conditions and plays a backup protection role for the next stage line. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The present application is a multi-impedance multi-time limit distance protection method with far backup function. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. The embodiments described in the present application are only a part of the embodiments of the present application, not all the embodiments. Based on the spirit of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0023] As shown in Figure 1 The present application discloses a multi-impedance multi-time limit distance protection method with far backup function, comprising: On the basis of the original grounding distance protection of the line, four sections of far backup grounding distance protection are added, including far backup grounding I section, far backup grounding II section, far backup grounding III section and far backup grounding IV section. When a single-phase ground fault occurs in the next level line, the line protection device collects the voltage and current signals at the fault point, calculates the measured impedance observed from the installation of the line protection, and monitors the fault duration. If the fault duration exceeds the action time limit of the backup protection of the lower level line, the measured impedance is compared with the impedance range of the original ground III section, the remote backup ground I section, the remote backup ground II section, the remote backup ground III section, and the remote backup ground IV section of the line in turn. When the measured impedance completely falls within the impedance range of a certain section, the fault is removed by the ground protection action of the section after the corresponding action time. Further preferably, When adding the four-section remote backup ground distance protection, the following setting values need to be added to the original protection setting values of the line, including: remote backup ground distance stage setting value, remote backup ground distance time.

[0024] In the four-section remote backup ground distance protection, the impedance range of each section of remote backup ground distance protection increases in steps, specifically: The impedance range of the remote backup ground I section is the sum of the impedance range of the original ground III section of the line and the remote backup ground distance stage setting value; the impedance range of the remote backup ground II section is the sum of the impedance range of the original ground III section of the line and 2 times the remote backup ground distance stage setting value; the impedance range of the remote backup ground III section is the sum of the impedance range of the original ground III section of the line and 3 times the remote backup ground distance stage setting value; the impedance range of the remote backup ground IV section is the sum of the impedance range of the original ground III section of the line and 4 times the remote backup ground distance stage setting value.

[0025] In the four-section remote backup ground distance protection, the action time of each section of remote backup ground distance protection increases in steps, specifically: The remote backup ground I section time is the remote backup ground distance time of the original ground III section of the line plus the remote backup ground distance time; the remote backup ground II section time is the remote backup ground distance time of the original ground III section of the line plus 2 times the remote backup ground distance time; the remote backup ground III section time is the remote backup ground distance time of the original ground III section of the line plus 3 times the remote backup ground distance time; the remote backup ground IV section time is the remote backup ground distance time of the original ground III section of the line plus 4 times the remote backup ground distance time.

[0026] In the four-section remote backup ground distance protection, the action condition of each section of remote backup ground distance protection needs to meet the following requirements: The corresponding section of the remote backup ground distance protection quadrilateral impedance characteristic meets; When the zero sequence power direction or the zero sequence voltage of the corresponding section is less than 1V, the impedance direction meets; The zero sequence current of the corresponding section is greater than the original ground zero sequence III section setting value of the line; The action time of the corresponding section of the remote backup ground distance protection meets; The sequence current fault phase selection of the corresponding section is correctly selected; The fault phase opening condition of the corresponding section of the remote backup ground distance protection meets.

[0027] The criterion that the fault phase opening condition of the remote backup ground distance protection meets is specifically:

[0028] Wherein, , , The amplitudes of the zero sequence, positive sequence and negative sequence currents respectively; The amplitude of the fault phase voltage; The included angle between the fault phase voltage and the fault phase current; The included angle between the positive sequence voltage and the positive sequence phase current; The amplitude of the positive sequence voltage; the (a), (b) and (c) conditions in the formula are logical or relations, and one of them is met, that is, the fault phase opening condition of the remote backup ground distance protection is met.

[0029] On the basis of the original phase-to-phase distance protection, four sections of remote backup phase-to-phase distance protection are added, including remote backup phase-to-phase I section, remote backup phase-to-phase II section, remote backup phase-to-phase III section and remote backup phase-to-phase IV section; When a phase-to-phase fault occurs in the next level line, the voltage and current signals of the fault point are collected by the protection device of the line, the measured impedance observed from the installation of the line protection is calculated, and the fault duration is monitored. If the fault duration exceeds the action time limit of the backup protection of the lower line itself, the measured impedance is compared with the impedance range of the original phase-to-phase III section, the remote backup phase-to-phase I section, the remote backup phase-to-phase II section, the remote backup phase-to-phase III section and the remote backup phase-to-phase IV section of the line in turn. If the measured impedance completely falls into the impedance range of a section, the section-to-phase protection will act after the corresponding action time of the section, and the fault will be removed.

[0030] Further preferably, In order to add four sections of remote backup phase-to-phase distance protection, the following setting values need to be added on the basis of the original protection setting values of the line, including remote backup phase-to-phase distance stage setting value and remote backup phase-to-phase distance time.

[0031] In the four sections of remote backup phase-to-phase distance protection, the impedance ranges of the remote backup phase-to-phase distance protection of each section are in a stepped increasing manner, specifically: The range of the first section of the remote backup phase-to-phase distance is the sum of the original phase-to-phase III section impedance range of the line and the distance stage value of the remote backup phase-to-phase distance; the range of the second section of the remote backup phase-to-phase distance is the sum of the original phase-to-phase III section impedance range of the line and 2 times the distance stage value of the remote backup phase-to-phase distance; the range of the third section of the remote backup phase-to-phase distance is the sum of the original phase-to-phase III section impedance range of the line and 3 times the distance stage value of the remote backup phase-to-phase distance; and the range of the fourth section of the remote backup phase-to-phase distance is the sum of the original phase-to-phase III section impedance range of the line and 4 times the distance stage value of the remote backup phase-to-phase distance.

[0032] In the four-section remote backup phase-to-phase distance protection, the action time of each section of the remote backup phase-to-phase distance protection is increased in steps, and specifically: The action time of the first section of the remote backup phase-to-phase distance is the remote backup phase-to-phase distance time of the original phase-to-phase III section of the line plus the remote backup phase-to-phase distance time; the action time of the second section of the remote backup phase-to-phase distance is the remote backup phase-to-phase distance time of the original phase-to-phase III section of the line plus 2 times the remote backup phase-to-phase distance time; the action time of the third section of the remote backup phase-to-phase distance is the remote backup phase-to-phase distance time of the original phase-to-phase III section of the line plus 3 times the remote backup phase-to-phase distance time; and the action time of the fourth section of the remote backup phase-to-phase distance is the remote backup phase-to-phase distance time of the original phase-to-phase III section of the line plus 4 times the remote backup phase-to-phase distance time.

[0033] In the four-section remote backup phase-to-phase distance protection, the action condition of each section of the remote backup phase-to-phase distance protection needs to meet the following requirements: The corresponding section of the remote backup phase-to-phase distance protection meets the phase circle impedance characteristic; The corresponding section of the fault phase-to-phase load line meets the requirement; The corresponding section of the remote backup phase-to-phase distance protection meets the fault phase-to-phase open condition; The action time of the corresponding section of the remote backup phase-to-phase distance protection meets the requirement.

[0034] The criterion for the fault phase-to-phase open condition in the remote backup phase-to-phase distance protection is specifically:

[0035] wherein, , , are the amplitudes of the zero sequence, positive sequence and negative sequence currents; is the phase-to-phase voltage of the two fault phases; is the included angle between the phase-to-phase voltage and the phase-to-phase current of the two fault phases; is the included angle between the positive sequence voltage and the positive sequence phase current; is the amplitude of the positive sequence phase voltage; the (a) and (b) conditions in the formula are the logical or relationship, and one of them is met, which meets the fault phase open condition in the remote backup phase-to-phase distance protection.

[0036] The present invention also discloses a multi-impedance multi-time-limit distance protection system with remote backup function based on the aforementioned method, including a remote backup ground distance protection addition module, a remote backup ground distance protection action judgment module, a remote backup phase-to-phase distance protection addition module, and a remote backup phase-to-phase distance protection action judgment module. The remote backup grounding distance protection module adds four remote backup grounding distance protection sections to the existing grounding distance protection of this line, including remote backup grounding section I, remote backup grounding section II, remote backup grounding section III and remote backup grounding section IV. The remote backup grounding distance protection action judgment module collects voltage and current signals at the fault point when a single-phase grounding fault occurs on the next-level line, calculates the measured impedance observed from the installation point of the protection on this line, and monitors the duration of the fault. If the duration of the fault exceeds the action time limit of the protection of the next-level line itself, the measured impedance is compared with the impedance range of the original grounding section III, the impedance range of the remote backup grounding section I, the impedance range of the remote backup grounding section II, the impedance range of the remote backup grounding section III, and the impedance range of the remote backup grounding section IV in sequence. If the impedance range of a certain section is matched, the grounding protection of that section will operate to clear the fault after the corresponding section's action time. The remote backup phase-to-phase distance protection module adds four stages of remote backup phase-to-phase distance protection on the basis of the original phase-to-phase distance protection, including remote backup phase-to-phase I stage, remote backup phase-to-phase II stage, remote backup phase-to-phase III stage and remote backup phase-to-phase IV stage. The remote backup phase-to-phase distance protection action judgment module, when a phase-to-phase fault occurs on the next-level line, collects the voltage and current signals at the fault point, calculates the measured impedance observed from the installation location of the protection on this line, and monitors the duration of the fault. If the duration of the fault exceeds the action time limit of the protection of the next-level line itself, the measured impedance is compared sequentially with the impedance range of the original phase-to-phase III section, the impedance range of the remote backup phase-to-phase I section, the impedance range of the remote backup phase-to-phase II section, the impedance range of the remote backup phase-to-phase III section, and the impedance range of the remote backup phase-to-phase IV section. If the impedance range of a certain section matches, the phase-to-phase protection of that section will operate to clear the fault after the corresponding section's action time.

[0037] Example 1: like Figure 1 As shown, this invention discloses a multi-impedance, multi-time-limit distance protection method with remote backup function, comprising: Based on the existing grounding distance protection of this line, four sections of remote backup grounding distance protection are added, including remote backup grounding section I, remote backup grounding section II, remote backup grounding section III and remote backup grounding section IV. When a single-phase ground fault occurs in the next level line, the line protection device collects the voltage and current signals at the fault point, calculates the measured impedance observed from the installation of the line protection, and monitors the fault duration. If the fault duration exceeds the action time limit of the lower level line self-protection, the measured impedance is compared with the impedance range of the original ground III section, the remote backup ground I section, the remote backup ground II section, the remote backup ground III section, and the remote backup ground IV section in turn. If the measured impedance meets the impedance range of the original ground III section, the ground distance III section acts after the ground distance III section time, and the fault is removed. When the measured impedance exceeds the range of the original ground III section, but meets the impedance range of the remote backup ground I section, the remote backup ground I section acts after the remote backup ground I section time, and the fault is removed. When the measured impedance exceeds the range of the remote backup ground I section, it meets the impedance range of the remote backup ground II section, and the remote backup ground II section acts after the remote backup ground II section time, and the fault is removed. When the measured impedance exceeds the range of the remote backup ground II section, it meets the impedance range of the remote backup ground III section, and the remote backup ground III section acts after the remote backup ground III section time, and the fault is removed. When the measured impedance exceeds the range of the remote backup ground III section, it meets the impedance range of the remote backup ground IV section, and the remote backup ground IV section acts after the remote backup ground IV section time, and the fault is removed. The measured impedance meets which section, and which section acts to remove the fault; On the basis of the original phase-to-phase distance protection, four remote backup phase-to-phase distance protections are added, including remote backup phase-to-phase I section, remote backup phase-to-phase II section, remote backup phase-to-phase III section, and remote backup phase-to-phase IV section. When the next level line occurs phase-to-phase fault, the line protection device collects the voltage and current signals of the fault point, calculates the measured impedance observed from the installation of the line protection, and monitors the fault duration. If the fault duration exceeds the action time limit of the lower level line protection, the measured impedance is compared with the impedance range of the original phase-to-phase III section, the impedance range of the remote backup phase-to-phase I section, the impedance range of the remote backup phase-to-phase II section, the impedance range of the remote backup phase-to-phase III section, and the impedance range of the remote backup phase-to-phase IV section in turn. If the measured impedance meets the impedance range of the original phase-to-phase III section, the phase-to-phase III section acts after the phase-to-phase III section time to remove the fault. If the measured impedance exceeds the impedance range of the original phase-to-phase III section, but meets the impedance range of the remote backup phase-to-phase I section, the remote backup phase-to-phase I section acts after the remote backup phase-to-phase I section time to remove the fault. If the measured impedance exceeds the impedance range of the remote backup phase-to-phase I section, but meets the impedance range of the remote backup phase-to-phase II section, the remote backup phase-to-phase II section acts after the remote backup phase-to-phase II section time to remove the fault. If the measured impedance exceeds the impedance range of the remote backup phase-to-phase II section, but meets the impedance range of the remote backup phase-to-phase III section, the remote backup phase-to-phase III section acts after the remote backup phase-to-phase III section time to remove the fault. If the measured impedance exceeds the impedance range of the remote backup phase-to-phase III section, but meets the impedance range of the remote backup phase-to-phase IV section, the remote backup phase-to-phase IV section acts after the remote backup phase-to-phase IV section time to remove the fault. The measured impedance meets which section, and which section acts to remove the fault.

[0038] The purpose of adding remote backup distance protection on the basis of the original ground distance protection in the interval of the line is the remote backup protection of the lower level line.

[0039] The setting principle considers four-level remote backup, that is, the sensitivity of the full length of all lines of the lower level line with assistance is considered.

[0040] According to the scheme, the related protection setting values and control words are added on the basis of the original protection setting values and control words of the line in the interval, including: Remote backup ground distance stage setting value, remote backup ground distance time, remote backup phase-to-phase distance stage setting value, remote backup phase-to-phase distance time, remote backup ground distance control word, and remote backup phase-to-phase distance control word. Among them, the remote backup ground distance time and the remote backup phase-to-phase distance time are both fixed time 200 ms.

[0041] The line protection remote backup ground distance protection is put into operation only when the distance protection hard pressure plate, the distance protection soft pressure plate, and the remote backup ground distance control word are put into operation.

[0042] The impedance range of the remote backup grounding I section is the original grounding III section impedance range of the line + the remote backup grounding distance stage setting value, the impedance range of the remote backup grounding II section is the original grounding III section impedance range + 2 times the remote backup grounding distance stage setting value, the impedance range of the remote backup grounding III section is the original grounding III section impedance range + 3 times the remote backup grounding distance stage setting value, and the impedance range of the remote backup grounding IV section is the original grounding III section impedance range + 4 times the remote backup grounding distance stage setting value. The remote backup grounding distance stage setting value considers the minimum calculated impedance value after all the lower line grounding faults.

[0043] The remote backup grounding I section time is the remote backup grounding distance time of the original grounding III section of the line + the remote backup grounding distance time, the remote backup grounding II section time is the remote backup grounding distance time of the original grounding III section of the line + 2 times the remote backup grounding distance time, the remote backup grounding III section time is the remote backup grounding distance time of the original grounding III section of the line + 3 times the remote backup grounding distance time, and the remote backup grounding IV section time is the remote backup grounding distance time of the original grounding III section of the line + 4 times the remote backup grounding distance time.

[0044] According to the scheme, the remote backup grounding I section action needs to meet the following conditions and: 1. The remote backup grounding I section quadrilateral impedance characteristic meets; 2. The impedance direction meets when the zero sequence power direction or the zero sequence voltage is less than 1V; 3. The zero sequence current is greater than the original grounding zero sequence III section setting value of the line; 4. The remote backup grounding distance I section time meets; 5. The sequence current fault phase selection is correctly selected; 6. The fault phase opening condition meets.

[0045] The opening criterion is shown in the following formula (1): (1) Wherein, I 0, I 1, I 2 are the amplitudes of the zero sequence, positive sequence and negative sequence currents respectively; is the fault phase voltage amplitude; is the included angle between the fault phase voltage and the fault phase current; is the included angle between the positive sequence voltage and the positive sequence phase current; is the positive sequence voltage amplitude; the (a), (b) and (c) conditions in formula (1) are the logical or relationship, and one of them meets the fault phase opening condition.

[0046] According to the scheme, the non-full-phase remote backup grounding I section action needs to meet the following conditions and: When any one side of a phase is a skip, the non-full phase state is entered, and impedance discrimination is no longer performed on the phase.

[0047] 1. The impedance of any one of the other two phases that are not skipped satisfies the far back-up grounding distance I section quadrilateral; 2. The resistance of the phase is less than 0.5 times the load resistance; 3. The far back-up grounding distance I section time is satisfied.

[0048] According to the scheme, the far back-up grounding distance II section action needs to satisfy the following conditions phase and: 1. The far back-up grounding distance II section quadrilateral impedance characteristic is satisfied; 2. The zero sequence power direction or the zero sequence voltage is less than 1V, and the impedance direction is satisfied; 3. The zero sequence current is greater than the original grounding zero sequence III section setting value of the line; 4. The far back-up grounding distance II section time is satisfied; 5. The sequence current fault phase selection is correctly selected; 6. The fault phase open condition is satisfied.

[0049] According to the scheme, the non-full phase far back-up grounding distance II section action needs to satisfy the following conditions phase and: When any one side of a phase is a skip, the non-full phase state is entered, and impedance discrimination is no longer performed on the phase.

[0050] 1. The impedance of any one of the other two phases that are not skipped satisfies the far back-up grounding distance II section quadrilateral; 2. The resistance of the phase is less than 0.5 times the load resistance; 3. The far back-up grounding distance II section time is satisfied.

[0051] According to the scheme, the far back-up grounding distance III section action needs to satisfy the following conditions phase and: 1. The far back-up grounding distance III section quadrilateral impedance characteristic is satisfied; 2. The zero sequence power direction or the zero sequence voltage is less than 1V, and the impedance direction is satisfied; 3. The zero sequence current is greater than the original grounding zero sequence III section setting value of the line; 4. The far back-up grounding distance III section time is satisfied; 5. The sequence current fault phase selection is correctly selected; 6. The fault phase open condition is satisfied.

[0052] According to the scheme, the non-full phase far back-up grounding distance III section action needs to satisfy the following conditions phase and: When any one side of a phase is a skip, the non-full phase state is entered, and impedance discrimination is no longer performed on the phase.

[0053] 1. The other two-phase impedance of the non-jumping phase meets the requirements of the remote backup grounding III section quadrilateral; 2. The phase resistance is less than 0.5 times the load resistance; 3. The remote backup grounding distance III section time meets the requirements.

[0054] According to the scheme, the remote backup grounding IV section action needs to meet the following conditions: 1. The remote backup grounding IV section quadrilateral impedance characteristic meets the requirements; 2. The zero sequence power direction or the zero sequence voltage is less than 1V, and the impedance direction meets the requirements; 3. The zero sequence current is greater than the original grounding zero sequence III section setting value of the line; 4. The remote backup grounding distance IV section time meets the requirements; 5. The sequence current fault selection is correctly selected; 6. The fault phase opening condition meets the requirements.

[0055] According to the scheme, the non-full-phase remote backup grounding IV section action needs to meet the following conditions: When one side of a certain phase is a jump, the non-full-phase state is entered, and the impedance of the phase is no longer distinguished.

[0056] 1. The other two-phase impedance of the non-jumping phase meets the requirements of the remote backup grounding IV section quadrilateral; 2. The phase resistance is less than 0.5 times the load resistance; 3. The remote backup grounding distance IV section time meets the requirements.

[0057] The remote backup phase-to-phase I section impedance range is the original phase-to-phase III section impedance range + the remote backup phase-to-phase distance stage setting value, the remote backup phase-to-phase II section impedance range is the original phase-to-phase III section impedance range + 2 times the remote backup phase-to-phase distance stage setting value, the remote backup phase-to-phase III section impedance range is the original phase-to-phase III section impedance range + 3 times the remote backup phase-to-phase distance stage setting value, and the remote backup phase-to-phase IV section impedance range is the original phase-to-phase III section impedance range + 4 times the remote backup phase-to-phase distance stage setting value.

[0058] The remote backup phase-to-phase I section time is the remote backup phase-to-phase distance time + 2 times the remote backup phase-to-phase distance time, the remote backup phase-to-phase II section time is the remote backup phase-to-phase distance time + 3 times the remote backup phase-to-phase distance time, the remote backup phase-to-phase III section time is the remote backup phase-to-phase distance time + 4 times the remote backup phase-to-phase distance time, and the remote backup phase-to-phase IV section time is the remote backup phase-to-phase distance time + 5 times the remote backup phase-to-phase distance time.

[0059] According to the scheme, the remote backup phase-to-phase I section action needs to meet the following conditions: The open criterion is shown in the following formula (1): (2) wherein, , , are the amplitudes of the zero sequence, positive sequence and negative sequence currents respectively; is the inter-phase voltage of the two fault phases; is the included angle between the inter-phase voltage of the two fault phases and the inter-phase current; is the included angle between the positive sequence voltage and the positive sequence phase current; is the amplitude of the positive sequence phase voltage; the (a) and (b) conditions in formula (2) are logically OR, and one of them is satisfied, which satisfies the open condition of the fault phase in the remote backup inter-phase distance protection.

[0060] According to the scheme, the non-full-phase remote backup inter-phase I section action needs to satisfy the following conditions and: When one side of a certain phase is a jump position, the non-full-phase state is entered, and impedance discrimination is no longer performed on the phase.

[0061] 1. The impedance remote backup inter-phase I section of the other two phases which are not the jump position satisfies the phase circle; 2. The fault phase inter-phase load line satisfies; 3. The remote backup inter-phase distance I section time satisfies.

[0062] According to the scheme, the remote backup inter-phase II section action needs to satisfy the following conditions and: 1. The remote backup inter-phase II section satisfies the phase circle; 2. The fault phase inter-phase load line satisfies; 3. The fault phase inter-phase open condition satisfies; 4. The remote backup inter-phase distance II section time satisfies.

[0063] According to the scheme, the non-full-phase remote backup inter-phase II section action needs to satisfy the following conditions and: When one side of a certain phase is a jump position, the non-full-phase state is entered, and impedance discrimination is no longer performed on the phase.

[0064] 1. The impedance remote backup inter-phase II section of the other two phases which are not the jump position satisfies the phase circle; 2. The fault phase inter-phase load line satisfies; 3. The remote backup inter-phase distance II section time satisfies.

[0065] According to the scheme, the remote backup inter-phase III section action needs to satisfy the following conditions and: 1. The remote backup inter-phase III section satisfies the phase circle; 2. The fault phase inter-phase load line satisfies; 3. The fault phase inter-phase open condition satisfies; 4. The remote backup distance III section time meets.

[0066] According to the scheme, the non-full-phase remote backup distance III section action needs to meet the following conditions: When any side of a certain phase is a jump position, the non-full-phase state is entered, and impedance discrimination is no longer performed on the phase.

[0067] 1. The impedance of any one of the other two non-jump positions meets the remote backup distance III section ratio; 2. The fault phase interval load line meets; 3. The remote backup distance III section time meets.

[0068] According to the scheme, the remote backup distance IV section action needs to meet the following conditions: 1. The remote backup distance IV section ratio meets; 2. The fault phase interval load line meets; 3. The fault phase interval open condition meets.

[0069] 4. The remote backup distance IV section time meets; According to the scheme, the non-full-phase remote backup distance IV section action needs to meet the following conditions: When any side of a certain phase is a jump position, the non-full-phase state is entered, and impedance discrimination is no longer performed on the phase.

[0070] 1. The impedance of any one of the other two non-jump positions meets the remote backup distance IV section ratio; 2. The fault phase interval load line meets; 3. The remote backup distance IV section time meets.

[0071] Through the above scheme, the remote backup distance protection is added to the basic protection configuration of the line protection, which plays a protective role for the next stage line end fault.

[0072] The present disclosure can be a system, a method, and / or a computer program product. The computer program product can include a computer readable storage medium having computer readable program instructions loaded thereon for causing a processor to implement various aspects of the present disclosure.

[0073] Computer readable storage media can be tangible storage media which can retain and store instructions for use by an instruction execution device. Computer readable storage media can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer readable storage media include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0074] Computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0075] Computer readable program instructions for carrying out operations of the present disclosure can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages such as the "C" programming language or similar programming languages. The computer readable program instructions can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate array (FPGA), or programmable logic array (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present disclosure.

[0076] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced, and any modification or replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. A multi-impedance, multi-time-limit distance protection method with remote backup function, characterized in that, include: Based on the existing grounding distance protection of this line, four sections of remote backup grounding distance protection are added, including remote backup grounding section I, remote backup grounding section II, remote backup grounding section III and remote backup grounding section IV. When a single-phase ground fault occurs on the next-level line, the protection device of this line collects the voltage and current signals at the fault point, calculates the measured impedance observed from the installation location of the protection on this line, and monitors the duration of the fault. If the duration of the fault exceeds the operating time limit of the backup protection of the next-level line itself, the measured impedance is compared with the impedance range of the original grounding section III, the remote backup grounding section I, the remote backup grounding section II, the remote backup grounding section III, and the remote backup grounding section IV of this line in sequence. When the measured impedance falls completely within the impedance range of a certain section, the grounding protection of that section will operate to clear the fault after the corresponding operating time of that section. Based on the existing phase-to-phase distance protection, four stages of remote backup phase-to-phase distance protection are added, including remote backup phase-to-phase I stage, remote backup phase-to-phase II stage, remote backup phase-to-phase III stage and remote backup phase-to-phase IV stage. When a phase-to-phase fault occurs on the next-level line, the protection device of this line collects the voltage and current signals at the fault point, calculates the measured impedance observed from the installation location of the protection on this line, and monitors the duration of the fault. If the duration of the fault exceeds the operating time limit of the backup protection of the next-level line itself, the measured impedance is compared with the impedance range of the original phase-to-phase III section, the remote backup phase-to-phase I section, the remote backup phase-to-phase II section, the remote backup phase-to-phase III section, and the remote backup phase-to-phase IV section of this line in sequence. If the measured impedance falls completely within the impedance range of a certain section, the phase-to-phase protection of that section will operate to clear the fault after the corresponding operating time of that section.

2. The multi-impedance multi-time distance protection method with remote backup function according to claim 1, characterized in that, When adding four sections of remote backup grounding distance protection and four sections of remote backup phase-to-phase distance protection, the following settings need to be added to the original protection settings of this line, including: remote backup grounding distance stage setting, remote backup grounding distance time, remote backup phase-to-phase distance stage setting, and remote backup phase-to-phase distance time.

3. The multi-impedance multi-time distance protection method with remote backup function according to claim 2, characterized in that, In the four-stage remote backup grounding distance protection, the impedance range of each stage of remote backup grounding distance protection increases in a stepwise manner, specifically as follows: The impedance range of the remote backup grounding section I is the sum of the impedance range of the original grounding section III of this line and the set value of the remote backup grounding distance stage; the impedance range of the remote backup grounding section II is the sum of the impedance range of the original grounding section III of this line and twice the set value of the remote backup grounding distance stage. The impedance range of the remote backup grounding section III is the sum of the impedance range of the original grounding section III of this line and the stage setting of 3 times the remote backup grounding distance; the impedance range of the remote backup grounding section IV is the sum of the impedance range of the original grounding section III of this line and the stage setting of 4 times the remote backup grounding distance.

4. The multi-impedance multi-time distance protection method with remote backup function according to claim 2, characterized in that, In the four-stage remote backup grounding distance protection, the operating time of each stage of remote backup grounding distance protection increases in a stepwise manner, specifically as follows: The distance time for the remote backup grounding I stage is the sum of the distance time for the original grounding III stage of this line and the distance time for the remote backup grounding. The distance for the second stage of the remote backup grounding is the distance for the original third stage of the grounding of this line plus twice the distance for the remote backup grounding. The remote backup grounding third stage time is the original grounding third stage remote backup grounding distance time of this line plus 3 times the remote backup grounding distance time; The distance for the remote backup grounding IV stage is the distance for the original grounding III stage of this line plus four times the distance for the remote backup grounding stage.

5. The multi-impedance multi-time distance protection method with remote backup function according to claim 2, characterized in that, In the four-stage remote backup grounding distance protection, the operating conditions of each stage of remote backup grounding distance protection must simultaneously meet the following requirements: The quadrilateral impedance characteristics of the corresponding section's far backup grounding distance protection are satisfied; The impedance direction is satisfied when the zero-sequence power direction or zero-sequence voltage is less than 1V in the corresponding segment; The zero-sequence current of the corresponding segment is greater than the original grounding zero-sequence III segment setting value of this line; The operating time of the remote backup grounding distance protection for the corresponding section is satisfied; The correct phase selection is made for the sequence current fault in the corresponding segment; The fault phase opening condition is met in the remote backup grounding distance protection of the corresponding section.

6. The multi-impedance multi-time distance protection method with remote backup function according to claim 5, characterized in that, The specific criteria for satisfying the fault phase opening condition in the remote backup grounding distance protection are as follows: in, , , These represent the amplitudes of the zero-sequence, positive-sequence, and negative-sequence currents, respectively. The voltage amplitude of the faulty phase; The angle between the fault phase voltage and the fault phase current; It is the angle between the positive sequence voltage and the positive sequence phase current; The positive sequence voltage amplitude; conditions (a), (b), and (c) in the formula are logical OR relationships, and satisfying any one of them satisfies the fault phase opening condition in the remote backup grounding distance protection.

7. The multi-impedance multi-time distance protection method with remote backup function according to claim 2, characterized in that, In the four-stage remote backup phase-to-phase distance protection, the impedance range of each stage of remote backup phase-to-phase distance protection increases in a stepwise manner, specifically as follows: The impedance range of the remote backup phase-to-phase I section is the sum of the impedance range of the original phase-to-phase III section of this line and the stage setting value of the remote backup phase-to-phase distance; the impedance range of the remote backup phase-to-phase II section is the sum of the impedance range of the original phase-to-phase III section of this line and twice the stage setting value of the remote backup phase-to-phase distance; the impedance range of the remote backup phase-to-phase III section is the sum of the impedance range of the original phase-to-phase III section of this line and three times the stage setting value of the remote backup phase-to-phase distance; the impedance range of the remote backup phase-to-phase IV section is the sum of the impedance range of the original phase-to-phase III section of this line and four times the stage setting value of the remote backup phase-to-phase distance.

8. The multi-impedance multi-time distance protection method with remote backup function according to claim 2, characterized in that, In the four-stage remote backup phase-to-phase distance protection, the operating time of each stage of remote backup phase-to-phase distance protection increases in a stepwise manner, specifically as follows: The time for the remote backup phase-to-phase I section is the original phase-to-phase III section remote backup phase-to-phase distance time of this line plus the remote backup phase-to-phase distance time; the time for the remote backup phase-to-phase II section is the original phase-to-phase III section remote backup phase-to-phase distance time of this line plus twice the remote backup phase-to-phase distance time. The remote backup phase-to-phase III time is the original phase-to-phase III distance time of this line plus 3 times the remote backup distance time. The time for the remote backup phase-to-phase IV section is the original phase-to-phase III section remote backup phase-to-phase distance time of this line plus 4 times the remote backup phase-to-phase distance time.

9. The multi-impedance multi-time distance protection method with remote backup function according to claim 2, characterized in that, In the four-stage remote backup phase-to-phase distance protection, the operating conditions of each stage of remote backup phase-to-phase distance protection must simultaneously meet the following requirements: The corresponding section's remote backup phase-to-phase distance protection ratio phase circle impedance characteristics are satisfied; The faulty phase-to-phase load line in the corresponding section meets the requirements; The fault phase-to-phase opening condition is met in the remote backup phase-to-phase distance protection of the corresponding section; The operating time of the remote backup phase-to-phase distance protection for the corresponding segment is satisfied.

10. The multi-impedance multi-time-limit distance protection method with remote backup function according to claim 9, characterized in that, The specific criteria for satisfying the fault phase-to-phase opening condition in the remote backup phase-to-phase distance protection are as follows: in, , , These represent the amplitudes of the zero-sequence, positive-sequence, and negative-sequence currents, respectively. This refers to the phase-to-phase voltage between the two faulty phases; The angle between the phase-to-phase voltage and phase-to-phase current of the two faulty phases; It is the angle between the positive sequence voltage and the positive sequence phase current; The positive sequence phase voltage amplitude; conditions (a) and (b) in the formula are logical OR relationships, and satisfying either one satisfies the fault phase opening condition in the remote backup phase-to-phase distance protection.

11. A multi-impedance multi-time-limit distance protection system with remote backup function based on the method of any one of claims 1-10, comprising a remote backup ground distance protection addition module, a remote backup ground distance protection operation judgment module, a remote backup phase-to-phase distance protection addition module, and a remote backup phase-to-phase distance protection operation judgment module, characterized in that: The remote backup grounding distance protection module adds four remote backup grounding distance protection sections to the existing grounding distance protection of this line, including remote backup grounding section I, remote backup grounding section II, remote backup grounding section III and remote backup grounding section IV. The remote backup grounding distance protection action judgment module collects voltage and current signals at the fault point when a single-phase grounding fault occurs on the next-level line, calculates the measured impedance observed from the installation point of the protection on this line, and monitors the duration of the fault. If the duration of the fault exceeds the action time limit of the protection of the next-level line itself, the measured impedance is compared with the impedance range of the original grounding section III, the impedance range of the remote backup grounding section I, the impedance range of the remote backup grounding section II, the impedance range of the remote backup grounding section III, and the impedance range of the remote backup grounding section IV in sequence. If the impedance range of a certain section is matched, the grounding protection of that section will operate to clear the fault after the corresponding section's action time. The remote backup phase-to-phase distance protection module adds four stages of remote backup phase-to-phase distance protection on the basis of the original phase-to-phase distance protection, including remote backup phase-to-phase I stage, remote backup phase-to-phase II stage, remote backup phase-to-phase III stage and remote backup phase-to-phase IV stage. The remote backup phase-to-phase distance protection action judgment module, when a phase-to-phase fault occurs on the next-level line, collects the voltage and current signals at the fault point, calculates the measured impedance observed from the installation location of the protection on this line, and monitors the duration of the fault. If the duration of the fault exceeds the action time limit of the protection of the next-level line itself, the measured impedance is compared sequentially with the impedance range of the original phase-to-phase III section, the impedance range of the remote backup phase-to-phase I section, the impedance range of the remote backup phase-to-phase II section, the impedance range of the remote backup phase-to-phase III section, and the impedance range of the remote backup phase-to-phase IV section. If the impedance range of a certain section matches, the phase-to-phase protection of that section will operate to clear the fault after the corresponding section's action time.

Images