A method for setting closing delay time limit of feeder automation tie switch

Abstract

The present invention discloses a method for setting the closing delay time limit of a feeder automation tie switch, comprising the steps of: calculating the maximum fault isolation time of each line; calculating the minimum fault isolation time of the tie switch; sorting the line priorities; and setting the associated tie switch delay parameters according to the line priorities from high to low. When the contact point between the backup line and the tie switch of the current line is located at or below the second segment of the current line, it is necessary to determine whether the tie switch closing delay parameters or ranges involved in both the upper-level line fault transfer strategy and the current line fault transfer strategy can simultaneously meet the requirements. When there is no solution to the conflict between the tie switch closing delay parameters or ranges involved in both the upper-level line fault transfer strategy and the current line fault transfer strategy, the current line fault transfer strategy is adjusted in consultation with the grid operation mode developers, and the tie switch closing delay parameters are set according to the adjusted current line fault transfer strategy. The method has strong operability, adaptability, and application value.

Description

Technical Field

[0001] The present invention relates to the technical field of power protection, and in particular to a method for setting a closing delay time limit of a feeder automation tie switch. Background Art

[0002] The proportion of electricity in terminal energy consumption will gradually increase, and the demand for power supply reliability will also become increasingly stringent. Feeder automation has the advantages of quickly isolating faults and restoring power to non-faulty areas. It is an important method to reduce the duration of power outages caused by distribution network faults, improve power supply reliability, and enhance user satisfaction. Feeder automation technology mainly includes four types: voltage-time type, current-time type, voltage-current type, and adaptive type. Related literature focuses on improving fault tripping criteria and fault isolation methods, improving the accuracy of automatic fault diagnosis, and shortening fault handling time. However, there is less research on the setting method of the closing delay limit of the tie switch, especially the method that can adapt to complex distribution networks and meet the flexible setting requirements of grid operation mode developers.

[0003] A paper (Feeder Automation with Reclosers and Voltage-Current Switches, Liu Jian, Cheng Hongli, and Li Qirui, Automation of Electric Power Systems, November 25, 2003, Vol. 27, No. 22, pp. 68-71) proposes that for grid-type distribution networks with multiple rescue strategies, the tie-breaker closing delay setting value should be greater than the maximum fault isolation time of the areas on either side of the tie-breaker. The closing delay of each tie-breaker is set based on the priority of the fault recovery strategy, and the tie-breaker setting value for a particular line must be greater than the maximum fault isolation time of all connected lines. This has certain limitations. If a line is connected to a line with a smaller number of sections, a shorter fault isolation time, and a higher priority, it is not necessary to set the tie-breaker setting value to exceed the maximum fault isolation time of all associated lines.

[0004] The paper ("Strategy for Implementation of Quasi-Real-Time Voltage-Current Feeder Automation for Overhead Lines," by Yang Hui, Wu Fubao, Lü Hongbing, and Jin Youhong, Automation of Electric Power Systems, Vol. 31, No. 22, November 25, 2007, pp. 108-111) proposes that a master station remotely controls substation and line section switches and tie switches via GPRS to implement optimal network reconfiguration, restoring power to healthy sections of a feeder after a fault. This strategy offers high post-fault network reconfiguration flexibility, but requires the installation of batteries on the FTUs to meet communication requirements and places high demands on the security of control data commands, reliability, and immediacy of communications. Summary of the Invention

[0005] In order to overcome the above-mentioned defects, the purpose of the present invention is to provide a method for setting the closing delay time limit of a feeder automation interconnection switch, which can flexibly adjust the number of transfer sections, disconnection points, and backup lines, can adapt to the interconnection structure of complex distribution networks, is simple and easy to learn, and has strong operability, adaptability and promotion and application value.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for setting a closing delay time limit of a feeder automation tie switch comprises the following steps:

[0008] S1. Calculate the maximum fault isolation time for each line based on the line reclosing time, the closing delay time of the sectionalizer, and the number of sectionalizers. The maximum fault isolation time for each line includes the time required for a permanent fault to occur between the last sectionalizer and the tie switch, the line outgoing line switch to open, the line sectionalizer to open, the reclosing delay to end, the closing of the last sectionalizer to the fault, and the accelerated opening and isolation of the fault after the protection switch is closed.

[0009] S2. Based on the longest fault isolation time of each line calculated in S1, the larger value of the fault isolation time of the lines on both sides of the tie switch is selected as the minimum fault isolation time of the tie switch;

[0010] S3. Develop the line importance ranking and fault transfer strategy given by personnel according to the grid operation mode, and rank the line priorities;

[0011] S4. Adjust the delay parameters of the associated tie switches in descending order of the line priorities determined in S3. First, determine whether the contact point between the backup line and the current line is located in the first segment of the current line. If the contact point is in the first segment of the current line, use the longest fault isolation time of the backup line as the tie switch closing delay time limit. If the contact point is in the second segment of the current line or below, proceed to S5.

[0012] S5. When the contact point between the backup line and the tie switch of the current line is located at the second section or below of the current line, it is necessary to determine whether the tie switch closing delay parameters or ranges involved in both the upper-level line fault transfer strategy and the current line fault transfer strategy can meet the requirements at the same time. If the requirements are met, the closing delay parameters of the tie switches associated with the current line are set by trial value according to the principle of reducing the fault recovery time. When setting the tie switch closing delay parameters by trial value, if the disconnection point for power restoration of the non-fault section of the fault line is the fault line section switch, the absolute value of the power time difference on both sides of the section switch should be less than or equal to the time difference ΔT. If the non-fault section of the fault line restores power to a specified line, the closing delay time of the tie switches of other backup lines of the fault line should be greater than the closing delay time of the designated backup line tie switches. If the requirements are not met, proceed to S6.

[0013] S6. When the interconnecting switch closing delay parameters or ranges involved in the upper-level line fault transfer strategy and the current-level line fault transfer strategy are inconsistent and cannot be resolved, the current-level line transfer strategy should be adjusted in consultation with the grid operation mode formulation personnel, and the interconnecting switch closing delay parameters should be set according to the adjusted current-level line fault transfer strategy.

[0014] Optionally, the section switches are all circuit breakers.

[0015] The technology closest to the present invention is the voltage-current feeder automation technology, which has the advantages of being simple, practical, economical, and easy to implement. The technical process is as follows:

[0016] (1) In the event of a short-term line fault, the line outlet circuit breaker opens, the line loses power, and the line section switches open with a delay. The outlet circuit breaker recloses, and the line section switches close in sequence with a delay, restoring power to the line.

[0017] (2) If the line fails permanently, the circuit breaker at the exit of the line opens, the line loses power, and the line section switches open with a time delay. The exit circuit breaker recloses and closes, and the line section switches close in sequence with a time delay. When the circuit breaker closes to the faulty section, the section (or interconnecting) switches on both sides of the faulty section open and lock. The exit circuit breaker recloses again to restore power to the non-faulty area, or the interconnecting switch closes after a long time delay to restore power to the non-faulty area.

[0018] Related literature mainly studies the transfer of all loads in non-fault sections to specific backup interconnecting lines when a fault occurs in the first section of a line. This strategy has a single transfer method and does not provide a method for setting the delay limit of the interconnecting switch when there is a interconnecting switch in the first section of a given line. It does not solve the problem of simultaneous closing of section switches or interconnecting switches at both ends of a section to be restored; it does not consider the closing delay setting of interconnecting switches between backup interconnecting lines; it is not suitable for complex distribution networks with high load rates of backup interconnecting lines; and it cannot meet the requirements of grid operation mode developers to flexibly adjust the transfer strategy according to the development of interconnecting line loads.

[0019] The positive beneficial effects of the present invention are:

[0020] 1) Based on a complex multi-connection line grid structure, the line load rate is coordinated, solving the problem of the transfer line being limited to a specific line when the first section of the line fails and the problem of insufficient backup capacity of a single backup line, making the transfer strategy more flexible;

[0021] 2) Introducing priorities among multiple backup supply lines to meet the requirements of grid operation mode planners to flexibly adjust the power transfer strategy based on the load development of the interconnection lines;

[0022] 3) Introducing a variable time difference in the closing delay of sectionalizers or tie switches, combined with the priority of the backup line transfer, solves the problem of setting the delay time limit of sectionalizers and tie switches on complex multi-tie lines, and avoids the simultaneous closing of sectionalizers or tie switches. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a flow chart of a method for setting a closing delay time limit of a feeder automation tie switch provided in Example 1 of the present invention;

[0024] Figure 2 This is a grid diagram of a method for setting the closing delay time limit of a feeder automation interconnection switch provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to some specific embodiments.

[0026] Example 1

[0027] like Figure 1 As shown, a method for setting the closing delay time limit of a feeder automation tie switch includes the following steps:

[0028] S1. Calculate the maximum fault isolation time for each line based on the line reclosing time, the closing delay time of the sectionalizer, and the number of sectionalizers. The maximum fault isolation time for each line includes the time required for a permanent fault to occur between the last sectionalizer and the tie switch, the line outgoing line switch to open, the line sectionalizer to open, the reclosing delay to end, the closing of the last sectionalizer to the fault, and the accelerated opening and isolation of the fault after the protection switch is closed.

[0029] S2. Based on the longest fault isolation time of each line calculated in S1, the larger value of the fault isolation time of the lines on both sides of the tie switch is selected as the minimum fault isolation time of the tie switch;

[0030] S3. Develop the line importance ranking and fault transfer strategy given by personnel according to the grid operation mode, and rank the line priorities;

[0031] S4. Adjust the delay parameters of the associated tie switches in descending order of the line priorities determined in S3. First, determine whether the contact point between the backup line and the current line is located in the first segment of the current line. If the contact point is in the first segment of the current line, use the longest fault isolation time of the backup line as the tie switch closing delay time limit. If the contact point is in the second segment of the current line or below, proceed to S5.

[0032] S5. When the contact point between the backup line and the tie switch of the current line is located at the second section or below of the current line, it is necessary to determine whether the tie switch closing delay parameters or ranges involved in both the upper-level line fault transfer strategy and the current line fault transfer strategy can meet the requirements at the same time. If the requirements are met, the closing delay parameters of the tie switches associated with the current line are set by trial value according to the principle of reducing the fault recovery time. When setting the tie switch closing delay parameters by trial value, if the disconnection point for power restoration of the non-fault section of the fault line is the fault line section switch, the absolute value of the power time difference on both sides of the section switch should be less than or equal to the time difference ΔT. If the non-fault section of the fault line restores power to a specified line, the closing delay time of the tie switches of other backup lines of the fault line should be greater than the closing delay time of the designated backup line tie switches. If the requirements are not met, proceed to S6.

[0033] S6. When the interconnecting switch closing delay parameters or ranges involved in the upper-level line fault transfer strategy and the current-level line fault transfer strategy are inconsistent and cannot be resolved, the current-level line transfer strategy should be adjusted in consultation with the grid operation mode formulation personnel, and the interconnecting switch closing delay parameters should be set according to the adjusted current-level line fault transfer strategy.

[0034] The section switches all adopt circuit breakers with functions of delayed closing, pressure loss opening, forward residual pressure locking, reverse residual pressure locking, pressure locking on both sides, and acceleration after closing.

[0035] This application is based on a complex multi-interconnection line grid structure and coordinates the line load rate to solve the following problems: the problem that the transfer line is limited to a specific line when the first section of the line fails and the problem of insufficient spare capacity of a single backup line, making the transfer strategy more flexible; introducing priorities among multiple backup lines to meet the requirements of power grid operation mode developers to flexibly adjust the transfer strategy according to the development of the interconnection line load; introducing a variable time difference in the closing delay of the section or interconnection switch, combined with the transfer priority of the backup line, solves the problem of setting the delay time limit of the section switch and the interconnection switch of complex multi-interconnection lines, and avoids the simultaneous closing of the section switch or the interconnection switch.

[0036] Example 2

[0037] like Figure 2 As shown in the figure, SLx is the line number, CBx is the line outlet switch, SxFDx is the x-section switch of Sx line (the closing delay is set to 7s in the example), SxyL is the contact switch of lines x and y, Tx is the maximum fault isolation time of line x, SSxyL is the minimum closing delay time of the contact switch of lines x and y, TSxyL is the set closing delay time of the contact switch of lines x and y, the time difference is ΔT (set to 6s in the example), and the line reclosing action time limit is set to 3s.

[0038] 1) Calculate the maximum fault isolation time for each line. Based on the line reclosing time limit, the closing delay time limit of the sectionalizer, and the number of sectionalizers, the maximum fault isolation time for lines SL1, SL2, SL3, SL4, and SL5 is T1 = 3 + 7 + 7 + 7 = 24 seconds, T2 = 3 + 7 = 10 seconds, T3 = 3 + 7 + 7 + 7 + 7 = 31 seconds, T4 = 3 + 7 + 7 + 7 = 24 seconds, and T5 = 3 + 7 = 10 seconds.

[0039] 2) Calculate the minimum closing delay of the tie switch. Taking the maximum of the longest fault isolation times of the lines on both sides of each tie switch as the minimum closing delay of the tie switch, we have: SS12L = max(T1, T2) = 24s, SS13L = max(T1, T3) = 31s, SS14L = max(T1, T4) = 24s, SS15L = max(T1, T5) = 24s, and SS34L = max(T3, T4) = 31s.

[0040] 3) Prioritize backup lines for transfer. Assume that the line importance ranking, as determined by the grid operation mode planner, is SL1, SL2, SL3, SL4, and SL5, from high to low. The fault transfer strategy is: if a fault occurs between CB1 and S1FD1 on line SL1, the load of the non-faulty section will be transferred to SL2 and SL3; if a fault occurs between CB2 and S2FD1 on line SL2, the load of the non-faulty section will be transferred to SL1; if a fault occurs between CB3 and S3FD1 on line SL3, the load of the non-faulty section will be transferred to SL1 and SL4; if a fault occurs between CB4 and S4FD1 on line SL4, the load of the non-faulty section will be transferred to SL1; if a fault occurs between CB5 and S5FD1 on line SL5, the load of the non-faulty section will be transferred to SL1.

[0041] 4) Set the closing delay parameters of the associated tie switches on line SL1 according to line priority. The first section of line SL1 is connected to line SL5. After a fault in the first section, tie switch S15L on line SL5 receives residual fault voltage and closes when CB1 coincides with the fault. After faults in the second and third sections of line SL1, the non-faulty sections on the power supply side of the faulty section continue to be powered by the power supply from line SL1, while the non-faulty sections on the load side of the faulty section are powered by the backup line tie switch. Specifically, S15L closes only according to dispatch instructions when CB1, the outgoing line switch of line SL1, is under maintenance; it does not close during a fault on line SL1. A permanent fault occurs between CB1 and S1FD1 on line SL1, and the load on the non-faulty sections is transferred to SL2 and SL3. Section switches S1FD1 and S1FD2 are required to open, S1FD3 is required to close, and tie switches S12L, S13L, and S14L are required to close. To avoid line closed-loop operation, it is necessary to meet |TS13L-TS12L|<=ΔT=6s, TS14L>TS12L+7s, and SS12L=24s, SS13L=31s, and SS14L=24s. Since the minimum closing delay of S13L is 31s, to reduce the power outage time, the S13L closing delay time limit should be set to TS13L=SS13L=31s, the S12L closing delay time limit should be set to TS12L=TS13L-ΔT=31-6=25s, and the adjustable range of the S14L closing delay time limit is TS14L>32s.

[0042] 5) Set the closing delay parameters of the associated tie switches on line SL2 according to line priority. If a fault occurs between CB2 and S2FD1 on line SL2, the load on the non-faulty section will be transferred to SL1. Section switch S2FD1 must be opened and tie switch S12L closed. The closing delay of tie switch S12L, set to TS12L = 25s for the fault transfer strategy on the upper-level line SL1, meets the requirements.

[0043] 6) Set the closing delay parameters of the associated tie switches on line SL3 based on line priority. If a fault occurs between CB3 and S3FD1 on line SL3, and the load on the non-faulty section is transferred to SL1 and SL4, section switch S3FD1 must be opened, S3FD2 closed, S3FD3 opened, S3FD4 closed, and tie switches S13L and S34L closed. To prevent closed-loop operation, |TS13L+7-TS34L| <= ΔT = 6s must be met. Since TS13L = 31s, the adjustable range of S34L is 32s <= TS34L <= 44s.

[0044] 7) Set the closing delay parameters of the associated tie breaker on line SL4 based on line priority. If a fault occurs between CB4 and S4FD1 on line SL4, and the load on the non-faulty section is transferred to SL1, section breaker S4FD1 must be opened, S4FD2 closed, and S4FD3 closed. Tie breaker S34L must be opened and S14L closed. To prevent closed-loop operation, the requirement TS34L > TS14L + 7s + 7s must be met. Since TS14L > 32s, TS34L > 46s is obtained. This contradicts the S34L adjustable range of 32s <= TS34L <= 44s specified for the fault transfer strategy on the upper-level line SL3. This means that the load transfer strategy for the non-faulty section of line SL4 to SL1 cannot be implemented if a fault occurs between CB4 and S4FD1. This should be adjusted in consultation with the grid operation planner. The adjusted power transfer strategy assumes that if a fault occurs between CB4 and S4FD1 on line SL4, the load on the non-faulty section will be transferred in sections to SL1 and SL3. Specifically, section switches S4FD1 and S4FD2 are open, S4FD3 is closed, and tie switches S34L and S14L are closed. To avoid closed-loop operation, |TS14L+7-TS34L| <= ΔT = 6s must be satisfied. Since TS14L > 32s, to minimize outage duration, TS14L is temporarily set to 33s, resulting in 34s <= TS34L <= 46s. Considering the adjustable range of S34L (32s <= TS34L <= 44s) set for the fault transfer strategy on the upper-level line SL3, the minimum value, TS34L = 34s, is selected, resulting in TS14L = 33s, which meets the requirement.

[0045] 8) Set the closing delay parameters of the tie-breaker associated with line SL5 according to line priority. When a fault occurs between CB5 and S5FD1 of line S5L, SL5 has a single fault-transfer path. When SL1 fails, no load is transferred to SL5. Therefore, S15L can restore power supply to the non-fault section according to the longest fault isolation time of S5L. Therefore, the closing delay time limit of S15L is set to TS15L = 10s.

[0046] The present invention proposes a method for setting the closing delay time limit of feeder automation interconnecting switches. The method uses the longest fault isolation time of the backup line to set the delay time limit of the interconnecting switch with interconnection in the first section of the fault line. By adding a delay time difference, the possibility of simultaneous closing of switches at both ends of the non-fault section of the fault line is avoided. The delay time limit of the interconnecting switches between the backup lines is set according to the requirements of the power transfer strategy. The grid operation mode planner can transfer the non-fault section of the fault line to the backup line in sections or transfer all of it to a single backup line according to the load changes of the phase interconnecting lines. The number of transfer sections, disconnection points, and backup lines can be flexibly adjusted, and the method can adapt to the interconnection structure of complex distribution networks. The method is simple and easy to learn, and has strong operability, adaptability, and promotion and application value.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for setting the closing delay time limit of a feeder automation tie switch, characterized in that: Including steps: S1. Calculate the maximum fault isolation time for each line based on the line reclosing time, the closing delay time limit of the sectionalizer, and the number of sectionalizers; The maximum fault isolation time of a line includes the time required for a permanent fault to occur between the last sectionalizing switch and the tie switch, the opening of the outgoing line switch, the opening of the sectionalizing switch, the closing of the reclosing switch after the reclosing delay expires, the closing of the last sectionalizing switch to the fault, and the accelerated opening and isolation of the fault after the protection switch is closed; S2. Based on the longest fault isolation time of each line calculated in S1, the larger value of the fault isolation time of the lines on both sides of the tie switch is selected as the minimum fault isolation time of the tie switch; S3. Develop personnel-defined line importance rankings and fault transfer strategies based on the grid operation mode, and prioritize the lines. S4. Adjust the delay parameters of the associated tie switches in descending order of the line priorities determined in S3. First, determine whether the contact point between the backup line and the current line is located in the first segment of the current line. If the contact point is in the first segment of the current line, use the longest fault isolation time of the backup line as the tie switch closing delay time limit. If the contact point is in the second segment of the current line or below, proceed to S5. S5. When the contact point between the backup supply line and the tie switch of the current line is located in the second section of the current line or below, it is necessary to determine whether the tie switch closing delay parameters or ranges involved in both the upper-level line fault transfer strategy and the current line fault transfer strategy can meet the requirements at the same time. If the requirements are met, the closing delay parameters of the tie switches associated with the current line can be set by trial value according to the principle of reducing the fault recovery time. If the first section of the current line fails, the tie switch between the current line and the backup line will receive the residual voltage from the fault and lock out when the outgoing switch of the current line coincides with the fault; if the second section and below of the current line fails, the non-fault section on the power supply side of the fault section will still be restored to power by the power supply of the current line, and the non-fault section on the load side of the fault section will be restored to power by closing the tie switch of the backup line; When setting the closing delay parameters of the tie switch during trial setting, if the disconnection point for power restoration of the non-fault section of the faulty line is the sectionalizer of the faulty line, the absolute value of the power-incoming time difference on both sides of the sectionalizer should be less than or equal to the time difference ΔT; if power is restored to a designated line from the non-fault section of the faulty line, the closing delay time of the tie switch of the other backup lines of the faulty line should be greater than the closing delay time of the tie switch of the designated backup line; If the requirements are not met, proceed to S6; S6. When the interconnecting switch closing delay parameters or ranges involved in the upper-level line fault transfer strategy and the current-level line fault transfer strategy are inconsistent and cannot be resolved, the current-level line transfer strategy should be adjusted in consultation with the grid operation mode formulation personnel, and the interconnecting switch closing delay parameters should be set according to the adjusted current-level line fault transfer strategy.

2. A method for setting the closing delay time limit of a feeder automation tie switch according to claim 1, characterized in that: The section switches all adopt circuit breakers.

3. A method for setting the closing delay time limit of a feeder automation tie switch according to claim 2, characterized in that: In step S5, when the outgoing line switch or the first section switch of the current level line fails, the load of the non-fault section is transferred to the backup line in sections.

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