A relay protection method for eliminating busbar dead zone

Abstract

The present invention discloses a relay protection method for eliminating a busbar dead zone, which relates to the technical field of relay protection, and is specifically a busbar protection method based on a double busbar wiring mode. The wiring structure of a relay protection method for eliminating a busbar dead zone is as follows: based on double busbar wiring, two busbars are connected through two busbar circuit breakers, and a busbar current transformer is installed between the two busbar circuit breakers; L1 is a busbar branch, L2 to L5 are line branches, the busbar branch has busbar circuit breakers DLX and DLY, and the busbar current transformer is TA1; branch 2 has circuit breaker DL2, and the current transformer of branch 2 is TA2; branch 3 has circuit breaker DL3, and the current transformer of branch 3 is TA3; branch 4 has circuit breaker DL4, and the current transformer of branch 4 is TA4; branch 5 has circuit breaker DL5, and the current transformer of branch 5 is TA5.

Description

Technical Field

[0001] The invention discloses a relay protection method for eliminating a busbar dead zone, which relates to the technical field of relay protection, and in particular is a busbar protection method based on a double busbar wiring mode. Background Art

[0002] The principle of bus differential protection is mainly to judge the fault inside and outside the bus area according to the large differential current, and select the fault bus to trip according to the small differential current. For the bus coupling interval, the bus protection is usually only connected to the bus coupling current transformer current. When a fault occurs between the bus coupling circuit breaker and the bus coupling current transformer, there is a situation where the fault cannot be quickly removed. The bus protection first trips the normal bus, and then removes the fault through the dead zone protection or bus coupling failure protection, resulting in the expansion of the fault removal range and the slow fault removal time, which has a great impact on the safe and stable operation of the system. Most engineering bus couplings are only equipped with a single switch. When the fault occurs between the bus coupling switch and the CT, the bus protection removes the two sections of the bus at the same time, which lacks selectivity and flexibility. The existing solution to the bus coupling dead zone problem is to install current transformers on both sides of the bus coupling circuit breaker. Although it can realize the rapid judgment of the bus coupling dead zone fault, it is necessary to remove two busbars to expand the power outage range, which greatly affects the power supply reliability of the system. Therefore, it is necessary to design a new solution to meet the actual power demand. Summary of the invention

[0003] In order to solve the problem of delayed tripping of double busbars and expanding the power outage range due to dead zone faults in the busbar coupling at the current stage, the present invention proposes a double busbar wiring mode and provides a corresponding relay protection action method.

[0004] The purpose of the present invention is to provide a relay protection method for eliminating busbar dead zone, which is applied to 220kV double-bus substation. It aims to solve the problem that when the traditional busbar protection method cuts off the busbar dead zone fault, the busbar protection delays the cutting off of two busbars, thereby expanding the power outage scope.

[0005] A wiring structure of a relay protection method for eliminating a busbar dead zone is as follows: based on double busbar wiring, two busbars are connected through two busbar circuit breakers, and a busbar current transformer is installed between the two busbar circuit breakers; L1 is a busbar branch, L2 to L5 are line branches, the busbar branch has busbar circuit breakers DLX and DLY, and the busbar current transformer is TA1; branch 2 has circuit breaker DL2, and the branch 2 current transformer is TA2; branch 3 has circuit breaker DL3, and the branch 3 current transformer is TA3; branch 4 has circuit breaker DL4, and the branch 4 current transformer is TA4; branch 5 has circuit breaker DL5, and the branch 5 current transformer is TA5 (hereinafter, current transformers are referred to as TA).

[0006] The busbar protection device is a BP-2CA / DG busbar protection device produced by Shenrui.

[0007] A relay protection method for eliminating busbar dead zone comprises: (1) fault area determination, (2) busbar differential protection action determination method, (3) busbar circuit breaker failure action determination method, (4) branch circuit breaker failure action determination method, (5) busbar inter-charging fault protection action determination method, and (6) busbar separate and parallel operation state determination method.

[0008] The specific methods mentioned above are:

[0009] (1) Fault area determination

[0010] The busbar protection device collects the three-phase voltage on the two busbars through the busbar transformer, collects the knife switch positions of all branches connected to the busbar and the switch positions of the two busbar circuit breakers through auxiliary nodes and open-in loops, and collects the three-phase current of all branches through busbar current transformers and branch current transformers. The above analog quantities are converted into digital quantities through A / D and then input into the CPU module of the protection device for calculation. The busbar protection device then calculates the busbar differential current in real time, and then brings the calculated differential current into the action equation of the compound ratio differential criterion.

[0011] Id>Idset

[0012] Id>K(Ir-Id)

[0013] Idset is the differential setting value, Id is the differential current, and Ir is the braking current.

[0014] When judging the large differential, the large differential current is the absolute value of the sum of the current vectors of each branch except the bus-coupling current, and the large differential braking current is the sum of the absolute values ​​of the current vectors of each branch except the bus-coupling current. When the large differential current and the large differential braking current meet the above compound ratio differential judgment action equation, the large differential action indicates that the fault occurs in the bus area. Otherwise, it does not occur.

[0015] According to the collected positions of the knife switches of each branch, the operating branches on bus I and bus II are determined, and the branch currents on each bus are vector-added and then taken in absolute value to determine whether a fault has occurred on each bus. The bus coupling TA polarity of the BP-2CA / DG bus protection device is fixedly pointed to bus II, so when calculating the small differential current of bus I, the vector sum of the currents of each branch on bus I is first subtracted from the bus coupling current vector and then the absolute value is calculated. The small differential current of bus II is the vector sum of the currents of each branch on bus II plus the bus coupling current vector and then the absolute value is calculated. The braking current of bus I or bus II is the sum of the absolute value of the current vectors of each branch and the absolute value of the bus coupling current vector.

[0016] When the large differential difference is determined as an internal fault and the I bus differential is determined to meet the compound ratio differential criterion action equation, the protection is determined as a fault within the I bus, and the I bus differential protection is activated. When the large differential difference is determined as an internal fault and the II bus differential is determined to meet the compound ratio differential criterion action equation, the protection is determined as a fault within the II bus, and the II bus differential protection is activated.

[0017] (2) Method for determining busbar differential protection action

[0018] The bus differential protection operates to clear the fault after the differential criteria of bus voltage, bus large difference and bus small difference meet the action requirements.

[0019] Because there are two busbars, each busbar has a corresponding busbar circuit breaker. The corresponding circuit breaker for busbar I is busbar circuit breaker DLY, and the corresponding circuit breaker for busbar II is busbar circuit breaker DLX. When the differential of busbar I is actuated, the protection trips all branch circuit breakers and busbar circuit breaker DLY on busbar I, and busbar circuit breaker DLX does not actuate. When the differential of busbar II is actuated, the protection trips all branch circuit breakers and busbar circuit breaker DLY on busbar II, and busbar circuit breaker DLY does not actuate.

[0020] That is, when the sum current mutation is greater than the set value or the large differential current is greater than the set value, and the large differential compound ratio differential element meets the action requirements, the busbar large differential action occurs. At this time, any busbar composite voltage is open, and the differential protection trips the corresponding bus tie circuit breaker and all branch circuit breakers on the corresponding bus.

[0021] When the sum current mutation is greater than the set value or the large differential current is greater than the set value, and the large differential compound ratio differential element meets the action requirements, the bus large differential action occurs. At this time, any bus small differential action occurs and the bus composite voltage is open, and the bus protection trips the corresponding bus tie circuit breaker and all branch circuit breakers on the corresponding bus.

[0022] The present invention takes four representative fault point locations and analyzes the bus differential protection action determination method one by one.

[0023] When a fault occurs at position a, that is, any position on the I bus, including a short distance from TA to the bus connected to the I bus branch and the tie line from the bus tie breaker DLX to I bus, it is collectively referred to as a fault in area a. At this time, the bus big difference meets the action conditions, the I bus small difference meets the action conditions, the I bus voltage decreases, the voltage lockout is opened, the I bus differential operates, and the bus tie breaker DLY and all switches on the I bus branch are tripped.

[0024] When a fault occurs at position b, that is, a fault occurs at any position on bus I, including a short distance from TA of the branch connected to bus I and a short distance from bus tie breaker DLY to bus I, it is collectively referred to as a fault in area a. At this time, the bus big difference meets the action conditions, the II bus small difference meets the action conditions, the II bus voltage decreases, the voltage lockout is opened, the II bus differential operates, and the bus tie breaker DLX and all switches on the II bus branch are tripped.

[0025] When a fault occurs at position c, that is, a fault occurs in area c between the bus tie breaker DLX and the bus tie TA, for the traditional double bus connection method, when a fault occurs at this position, the bus protection will first operate to trip one bus, and then trip the other bus after a delay. However, when a fault occurs here, the protection action judgment method of the present invention is changed to: the bus large difference meets the action condition, the I bus small difference meets the action condition, the I bus voltage is reduced, the voltage lock is opened, the I bus differential is operated, and the bus tie breaker DLY and all switches on the I bus branch are tripped.

[0026] Since the bus tie circuit breaker DLY that is tripped by the I bus differential action is not within the I bus differential protection range, that is, it is not within area a and area c, when a fault occurs at any point within area a and area c, tripping the bus tie circuit breaker DLY can disconnect the connection between the fault point and the II bus, so that there is no dead zone in the differential protection, eliminating the bus tie dead zone problem.

[0027] When a fault occurs at position d, that is, a fault occurs in area d between the bus tie breaker DLY and the bus tie TA, the II bus action determination method is similar. All branch circuit breakers and the bus tie breaker DLX on the II bus are cut off, and there is also no dead zone problem.

[0028] From the above analysis, it can be seen that when a fault occurs at any position on the bus, the bus differential protection can remove the fault, and the differential protection range of bus I and bus II also extends to the bus coupling dead zone position, that is, the bus differential protection range of bus I is expanded from the original area a to the sum of area a and area c. Similarly, the bus differential protection range of bus II is expanded from the original area b to the sum of area b and area d, eliminating the bus coupling dead zone problem.

[0029] (3) Method for determining failure of bus tie circuit breaker

[0030] When the bus tie circuit breaker is in the closed position, the protection receives the start-failure signal, the protection action node has not returned, and there is current in the bus tie TA, the bus protection starts the bus tie failure protection. The protection trips two bus tie circuit breakers within a time limit according to the opening status of the bus voltage, even if the failed bus tie circuit breaker will trip once, and trips two buses within a time limit.

[0031] When a fault occurs at any point in area a, the differential protection of bus I is activated, and the protection trips all branch circuit breakers and bus tie circuit breaker DLY on bus I. At this time, bus tie circuit breaker DLY fails but does not trip, and current still flows through the fault point. According to the voltage reduction of bus I, there is current in bus tie TA, and the protection action node has not returned. The bus tie failure protection is started, and the protection delay action is performed. The bus tie circuit breaker DLX is tripped in the first time limit, and all branch circuit breakers on bus II are tripped in the second time limit. When bus tie circuit breaker DLX trips, bus II is isolated from the fault point, the failure protection action returns, and bus II maintains normal operation.

[0032] When a fault occurs at any point in area c, the busbar failure protection will trip the busbar circuit breaker DLX within the first time limit. At this time, the fault has not been removed and the failure criterion is still met. The protection will trip all branches on the II bus within the second time limit and the fault point will be isolated.

[0033] When the fault point is located at any point in area a or area c, the differential protection of bus I is activated, the bus tie circuit breaker DLY fails and does not operate, and the bus tie circuit breaker DLX is tripped within a time limit. However, the bus tie circuit breaker DLX also fails and operates. The failure action criteria are still met, and all branch circuit breakers on bus II are tripped within a time limit.

[0034] When the fault point is located in area b or area d, the protection action determination method is similar.

[0035] From the above analysis, it can be seen that only when the fault point occurs in area a or area b or both circuit breakers fail to operate, will all circuit breakers on bus II be tripped. However, the probability of two bus tie circuit breakers failing at the same time is much smaller than the probability of a single bus tie circuit breaker failing. Therefore, when a fault occurs on the bus and the bus tie circuit breaker fails, compared with the traditional method, it is very likely that only one bus needs to be cut off to isolate the fault, greatly improving the power supply reliability.

[0036] (4) Method for determining branch circuit breaker failure

[0037] When the branch circuit breaker fails, the busbar protection logic is the same, which is to trip all the circuit breakers on the corresponding bus where the branch is located and the corresponding bus tie circuit breaker. The failure of branch 3 circuit breaker is taken as an example for analysis.

[0038] When the breaker DL3 of branch 3 of bus I fails, according to the voltage reduction of bus I, there is current in bus tie TA, and the protection action node has not returned, the two bus tie circuit breakers and the remaining branch circuit breakers on bus I are tripped with delay. If other branch circuit breakers fail, the action determination method is the same. If any branch circuit breaker of bus II fails, the action determination method is similar and will not be repeated.

[0039] (5) Method for determining the action of fault protection during busbar charging

[0040] When bus I charges bus II, a fault occurs in the area formed by bus tie TA and the branches of bus II. At this time, bus II differentially operates to trip bus tie circuit breaker DLX and cut off the fault. Since bus II is the charged bus and the entire bus has only power transmission branches, the action of bus II does not affect the operation of the operating interval.

[0041] When bus I charges bus II, a fault occurs between bus tie TA and bus tie circuit breaker DLX. The bus protection is based on: bus I has normal voltage, bus tie circuit breaker DLX is open, bus tie circuit breaker DLY is closed, bus tie circuit breaker is closed to charge bus II, a fault occurs between bus tie circuit breaker DLX and bus tie TA, bus I voltage decreases, bus I has a small differential action, bus tie TA has no current, and the protection delay is 300ms to cut off bus tie circuit breaker DLX. The branch circuit breaker on bus I does not change position.

[0042] When bus II charges bus I, bus tie circuit breaker DLY is closed, and bus tie circuit breaker DLX is always in the closed position. The operating principle is the same, and the protection action is opposite.

[0043] It can be seen that when the operating bus charges the maintenance bus, no matter where the fault point occurs, it will not affect the normal operation of the equipment on the operating bus.

[0044] (6) Determination method of busbar separate and parallel operation status

[0045] The tripping positions of bus tie circuit breaker DLX and bus tie circuit breaker DLY are TWJ X and TWJ Y When TWJ=0, the circuit breaker is in the closed position, and when TWJ=1, the circuit breaker is in the open position. The dual bus connection mode of the present invention has two bus tie circuit breakers. When both bus tie circuit breakers are in the closed position, it is determined that the dual busbars are in parallel operation. When any one of the two bus tie circuit breakers is in the open position, it is determined that the dual busbars are in separate operation.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. It eliminates the dead zone problem of the busbar. There is no need to cut off two busbars to eliminate the dead zone fault of the busbar, and quick action ensures the safety of the equipment.

[0048] 2. When a single busbar circuit breaker fails, there is a high probability that only one busbar needs to be cut off, which improves the power supply reliability.

[0049] 3. Although the primary wiring method has changed, the calculation logic of the protection does not need to be specially adjusted. The existing busbar protection devices can meet the needs. Only the specific settings of the tripped busbar switch need to be made, and it can be adjusted by setting the export matrix, which is highly flexible and feasible.

[0050] 4. Only one bus tie switch is added, which has a relatively low cost, but compared with the traditional method, one less busbar is tripped, and the overall economy is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is the primary wiring diagram of the system;

[0052] Figure 2 This is a schematic diagram of different fault points in the primary system;

[0053] Figure 3 This is a schematic diagram of a system fault area;

[0054] Figure 4 This is a diagram showing the method for determining the large differential action of the differential protection busbar;

[0055] Figure 5 This is a diagram of the method for determining the small differential action of the differential protection busbar;

[0056] Figure 6 This is a diagram of the method for determining the action of the busbar failure protection;

[0057] Figure 7 It is the logic diagram for distinguishing the parallel and separate operation of buses. DETAILED DESCRIPTION

[0058] The following is combined with Figure 1-7 The present invention is further described in detail with reference to the embodiments. In this embodiment, a relay protection method for eliminating a busbar dead zone is provided, and the busbar protection device is a BP-2CA / DG busbar protection device produced by Shenrui as an example.

[0059] Fault area determination

[0060] The busbar protection device collects the three-phase voltage on the two busbars through the busbar transformer, collects the knife switch positions of all branches connected to the busbar and the switch positions of the two busbar circuit breakers through auxiliary nodes and open-in loops, and collects the three-phase current of all branches through busbar current transformers and branch current transformers. The above analog quantities are converted into digital quantities through A / D and then input into the CPU module of the protection device for calculation. The busbar protection device then calculates the busbar differential current in real time, and then brings the calculated differential current into the action equation of the compound ratio differential criterion.

[0061] Id>Idset

[0062] Id>K(Ir-Id)

[0063] Idset is the differential setting value, Id is the differential current, and Ir is the braking current.

[0064] When judging the large differential, the large differential current is the absolute value of the sum of the current vectors of each branch except the bus-coupling current, and the large differential braking current is the sum of the absolute values ​​of the current vectors of each branch except the bus-coupling current. When the large differential current and the large differential braking current meet the above compound ratio differential judgment action equation, the large differential action indicates that the fault occurs in the bus area. Otherwise, it does not occur.

[0065] According to the collected positions of the knife switches of each branch, the operating branches on bus I and bus II are determined, and the branch currents on each bus are vector-added and then taken in absolute value to determine whether a fault has occurred on each bus. The bus coupling TA polarity of the BP-2CA / DG bus protection device is fixedly pointed to bus II, so when calculating the small differential current of bus I, the vector sum of the currents of each branch on bus I is first subtracted from the bus coupling current vector and then the absolute value is calculated. The small differential current of bus II is the vector sum of the currents of each branch on bus II plus the bus coupling current vector and then the absolute value is calculated. The braking current of bus I or bus II is the sum of the absolute value of the current vectors of each branch and the absolute value of the bus coupling current vector.

[0066] When the large differential difference is determined as an internal fault and the I bus differential is determined to meet the compound ratio differential criterion action equation, the protection is determined as a fault within the I bus, and the I bus differential protection is activated. When the large differential difference is determined as an internal fault and the II bus differential is determined to meet the compound ratio differential criterion action equation, the protection is determined as a fault within the II bus, and the II bus differential protection is activated.

[0067] Method for determining busbar differential protection action

[0068] When the sum current mutation is greater than the set value or the large differential current is greater than the set value, and the large differential compound ratio differential element meets the action requirements, the busbar large differential action occurs. At this time, any busbar composite voltage is open, and the differential protection trips the corresponding busbar circuit breaker and all branch circuit breakers on the corresponding busbar. The schematic diagram is as follows Figure 4 shown.

[0069] When the sum current mutation is greater than the set value or the large differential current is greater than the set value, and the large differential compound ratio differential element meets the action requirements, the busbar large differential action occurs. At this time, any busbar small differential action occurs and the busbar composite voltage is open. The busbar protection trips the corresponding bus tie circuit breaker and all branch circuit breakers on the corresponding busbar. The schematic diagram is as follows: Figure 5 shown.

[0070] According to different fault locations, four fault points are selected to conduct a detailed analysis on the bus differential protection action determination method.

[0071] When position a, i.e., any position on busbar I, includes a short distance from TA of the connecting branch on busbar I to the busbar and the connecting line from busbar tie breaker DLX to busbar I, it is collectively referred to as a phase A grounding fault in area a. The voltage of phase A of busbar I decreases. At this time, the currents of branch 3 and branch 5 flow from the line to the busbar, and the busbar tie current flows from busbar II to busbar I. The currents are recorded as Ik3, Ik5, and Ik1 respectively. The currents of branch 2 and branch 4 on busbar II flow from the line to the busbar, and the currents are recorded as Ik2 and Ik4 respectively. The sum of the two is equal to the busbar tie current Ik1. The busbar points to the line, which is positive. The busbar tie current flows from busbar II to busbar I, which is positive. According to the calculation formula of the small difference of busbar I, the difference current Id of busbar I is the sum of the absolute values ​​of Ik3, Ik5, and Ik1, which satisfies the action equation of the compound ratio differential criterion. At this time, the large differential current satisfies the action equation of the compound ratio differential criterion, the small differential current of bus II is 0, all bus protections determine that bus I is faulty, and the differential action of bus I trips the bus tie circuit breaker DLY and all branch circuit breakers on bus I.

[0072] When a fault occurs at position c, that is, a fault occurs between the bus tie circuit breaker DLX and the bus tie TA, the current conditions in each branch remain unchanged. At this time, it is determined that I bus is faulty, and the I bus differential is operated to trip the bus tie circuit breaker DLY and the left and right branch circuit breakers on I bus, and the fault is eliminated.

[0073] When a fault occurs at position b and position d, the fault is cleared by the II bus differential action. It can be seen that no matter where the fault occurs on the bus, the faulty bus can be determined based on the current calculation, and then the fault is cleared by the corresponding differential protection. There is no traditional way that when a fault occurs between the bus tie circuit breaker and the bus tie TA, the bus tie protection first trips one bus and then trips the other bus after a delay. This reduces the scope of power outages, greatly improves power supply reliability, and eliminates the problem of bus tie dead zones.

[0074] Method for judging failure of bus tie circuit breaker

[0075] When the bus tie circuit breaker is in the closed position, the protection receives the start failure signal, the protection action node does not return, the bus tie TA has current, and the bus protection starts the bus tie failure protection. The protection trips two bus tie circuit breakers in one time limit according to the bus voltage opening situation. Even if the failed bus tie circuit breaker trips once, it trips two buses in two time limits. The logic diagram is as follows Figure 6 shown.

[0076] When a fault occurs at point a, the bus differential action of bus I trips the bus tie circuit breaker DLY. Due to the mechanism fault, the bus tie circuit breaker DLY fails and does not trip. At this time, bus II is powered through the bus tie circuit breaker fault point, resulting in current flowing through bus tie TA all the time. The bus protection determines that the bus tie circuit breaker DLY fails based on the bus differential startup failure action node not returning and the current flowing through bus tie TA. The bus tie failure protection is started and the two bus tie circuit breakers are tripped within a time limit. Due to the failure of the bus tie circuit breaker DLY, the bus tie circuit breaker DLX trips at this time, isolating bus II from the fault point and removing the fault.

[0077] If the fault point is at point c, that is, between the bus tie circuit breaker DLX and the bus tie TA, the tripping of the bus tie circuit breaker DLX cannot isolate the II bus from the fault point. At this time, the bus tie TA determines that there is still a fault current, the protection action does not return, and the bus tie failure protection second time limit trips all branches on the two busbars, and the fault is removed.

[0078] It can be seen that the failure protection will only cut off the two busbars when the bus tie circuit breaker fails and the fault occurs between another bus tie circuit breaker and the bus tie TA or when the two bus tie circuit breakers fail at the same time. Since the bus tie circuit breaker and the bus tie TA are close to each other and the probability of two bus tie circuit breakers failing at the same time is very small, in most cases, when a single bus tie circuit breaker fails, only one busbar needs to be cut off to isolate the fault, greatly improving the high-point reliability of the system.

[0079] Method for judging failure of branch circuit breaker

[0080] When the busbar circuit breaker is in the closed position, the protection receives the start failure signal, the protection action node does not return, the busbar TA has current, and the busbar protection starts the busbar failure

[0081] Method for determining fault protection action during busbar charging

[0082] When bus I charges bus II, all the operating intervals on bus II are adjusted to bus I operation through knife switches, there is no voltage on bus II, the bus tie circuit breaker DLX is disconnected, the bus tie circuit breaker DLY is closed, and the power transmission branch is adjusted to bus II operation. When power is transmitted, the bus tie circuit breaker DLX is manually closed, and bus I charges bus II, i.e. the power transmission interval on bus II, through the bus tie circuit breaker. When a fault occurs at position b or position d, the voltage of bus II decreases, the large differential differential operates, the small differential differential operates, and there is current on bus TA. The differential operation of bus II disconnects the bus tie circuit breaker DLX and the power transmission line on bus II.

[0083] If the charge reaches the dead zone, that is, when a fault occurs at point c, there is no current in the bus coupler TA, the large differential action occurs, the I bus small differential action occurs, the busbar protection delays 300ms to open the bus coupler circuit DLX and cut off the fault.

[0084] Method for determining busbar separate and parallel operation status

[0085] The busbar protection collects the switch positions of the two bus tie breakers through the circuit breaker position auxiliary node, and through the trip position mark, the trip positions of the bus tie breakers DLX and DLY are TWJ respectively. X and TWJ Y When TWJ=0, the circuit breaker is in the closed position, and when TWJ=1, the circuit breaker is in the open position.

[0086] After the switch position is collected to the bus protection, the CPU performs a logical operation and performs an OR operation on the two switch positions. When the two bus tie circuit breakers are both in the closed position, the double busbars are judged to be in parallel operation. When any of the two bus tie circuit breakers is in the open position, the double busbars are judged to be in separate operation. The logic diagram is as follows Figure 7 shown.

Claims

1. A relay protection method for eliminating busbar dead zone, characterized in that: The wiring structure used in the method is as follows: based on double busbar wiring, two busbars are connected through two busbar circuit breakers, and a busbar current transformer is installed between the two busbar circuit breakers; L1 is a busbar branch, L2 to L5 are line branches, the busbar branch includes a busbar circuit breaker DLX, a busbar current transformer TA1 and a busbar circuit breaker DLY connected in series in sequence; branch 2 includes a circuit breaker DL2 and a current transformer TA2 connected in series; branch 3 includes a circuit breaker DL3 and a current transformer TA3 connected in series; branch 4 includes a circuit breaker DL4 and a current transformer TA4 connected in series; branch 5 includes a circuit breaker DL5 and a current transformer TA5 connected in series; The above wiring structure is respectively subjected to the fault area determination method, bus differential protection action determination method, bus tie circuit breaker failure action determination method, branch circuit breaker failure action determination method, bus inter-charging fault protection action determination method and bus separate and parallel operation status determination method.

2. A relay protection method for eliminating busbar dead zone according to claim 1, characterized in that: The fault area determination method is: The busbar protection device collects the three-phase voltage on the two busbars through the busbar transformer, collects the switch positions of all branches connected to the busbar and the switch positions of the two busbar circuit breakers through the auxiliary node and the open circuit, and collects the three-phase current of all branches through the busbar current transformer and the current transformer of each branch; the analog quantity is converted into digital quantity through A / D and then input into the CPU module of the protection device for calculation; then the busbar protection device calculates the busbar differential current in real time, and then brings the calculated differential current into the action equation of the compound ratio differential criterion; Id>Idset Id>K(Ir-Id) Idset is the differential setting value, Id is the differential current, and Ir is the braking current; When judging the large differential, the large differential current is the absolute value of the sum of the vector currents of each branch except the bus-coupling current, and the large differential braking current is the sum of the absolute values ​​of the vector currents of each branch except the bus-coupling current; when the large differential current and the large differential braking current meet the above compound ratio differential judgment action equation, the large differential action indicates that the fault occurs in the bus area, otherwise it does not; According to the acquired switch positions of each branch, determine the operating branches on bus I and bus II, and add the branch currents on each bus by vector and then take the absolute value to determine whether a fault occurs on each bus; The busbar protection device busbar TA polarity is fixed to bus II. When calculating the small differential current of bus I, the current vector sum of each branch on bus I is first subtracted from the busbar current vector and then the absolute value is calculated. The small differential current of bus II is the sum of the current vector sum of each branch on bus II plus the busbar current vector and then the absolute value is calculated. The braking current of bus I or bus II is the sum of the absolute value of the current vector of each branch and the absolute value of the busbar current vector. When the large differential difference is judged as a fault within the zone and the I bus differential is judged to satisfy the compound ratio differential criterion action equation, the protection is judged as a fault within the I bus, and the I bus differential protection is activated; when the large differential difference is judged as a fault within the zone and the II bus differential is judged to satisfy the compound ratio differential criterion action equation, the protection is judged as a fault within the II bus, and the II bus differential protection is activated.

3. A relay protection method for eliminating busbar dead zone according to claim 1, characterized in that: The busbar differential protection action determination method is: After the bus differential protection determines that the bus voltage, bus large difference and bus small difference meet the action requirements, the bus differential protection will operate to clear the fault. Because there are two busbars, each bus has a corresponding busbar circuit breaker. The corresponding circuit breaker for bus I is busbar circuit breaker DLY, and the corresponding circuit breaker for bus II is busbar circuit breaker DLX. When the differential of bus I is actuated, the protection will trip all branch circuit breakers and busbar circuit breaker DLY on bus I, and busbar circuit breaker DLX will not actuate. When the differential of bus II is actuated, the protection will trip all branch circuit breakers and busbar circuit breaker DLY on bus II, and busbar circuit breaker DLY will not actuate.

4. A relay protection method for eliminating busbar dead zone according to claim 1, characterized in that: The method for determining the failure of the busbar circuit breaker is as follows: When the bus tie circuit breaker is in the closed position, the protection receives the start failure signal, the protection action node does not return, and the bus tie TA has current, the bus protection starts the bus tie failure protection. The protection trips two bus tie circuit breakers in one time limit according to the bus voltage opening situation. Even if the failed bus tie circuit breaker trips once, it will trip two buses in two time limits. That is, when a fault occurs at any point in area a, the differential protection of bus I is activated, and the protection trips all branch circuit breakers and bus tie circuit breaker DLY on bus I. At this time, bus tie circuit breaker DLY fails but does not trip, and current still flows through the fault point. According to the voltage reduction of bus I, there is current in bus tie TA, and the protection action node has not returned, so bus tie failure protection is started, and the protection delay action is performed. The bus tie circuit breaker DLX is tripped within a time limit, and all branch circuit breakers on bus II are tripped within a time limit. When bus tie circuit breaker DLX is tripped, bus II is isolated from the fault point, the failure protection action returns, and bus II maintains normal operation. When a fault occurs at any point in area c, the busbar failure protection 1 time limit trips the busbar circuit breaker DLX. At this time, the fault has not been removed and the failure criterion is still met. The protection 2 time limit trips all branches on bus II and the fault point is isolated. When the fault point is located at any point in area a or area c, the differential protection of bus I is activated, the bus tie circuit breaker DLY fails and does not operate, and the bus tie circuit breaker DLX is tripped within a time limit, but the bus tie circuit breaker DLX also fails and operates, and the failure action criterion is still met, and all branch circuit breakers on bus II are tripped within a time limit; When the fault point is located in area b or area d, the protection action determination method is similar.

5. A relay protection method for eliminating busbar dead zone according to claim 1, characterized in that: The method for determining the failure of branch circuit breaker is as follows: When the branch circuit breaker fails, the busbar protection logic is the same, which is to trip all the circuit breakers on the corresponding bus where the branch is located and the corresponding bus tie circuit breaker. The failure of branch 3 circuit breaker is taken as an example for analysis; When the circuit breaker DL3 of branch 3 of bus I fails, the voltage of bus I decreases, there is current in bus tie TA, and the protection action node does not return, so the two bus tie circuit breakers and the remaining branch circuit breakers on bus I are delayed to open; if other branch circuit breakers fail, the action judgment method is the same; if any branch circuit breaker of bus II fails, the action judgment method is the same.

6. A relay protection method for eliminating busbar dead zone according to claim 1, characterized in that: The method for determining the fault protection action during busbar charging is as follows: When bus I charges bus II, a fault occurs in the area formed by bus tie TA and branches of bus II. At this time, bus II differentially operates to trip bus tie circuit breaker DLX and remove the fault. Since bus II is the charged bus and the entire bus only has power transmission branches, the operation of bus II does not affect the operation interval. When bus I charges bus II, a fault occurs between bus tie TA and bus tie circuit breaker DLX. The bus protection is based on: bus I has normal voltage, bus tie circuit breaker DLX is open, bus tie circuit breaker DLY is closed, bus tie circuit breaker is closed to charge bus II, a fault occurs between bus tie circuit breaker DLX and bus tie TA, bus I voltage decreases, bus I has a small differential action, bus tie TA has no current, protection delays 300ms to cut off bus tie circuit breaker DLX, and branch circuit breaker on bus I does not change position; When bus II charges bus I, bus tie circuit breaker DLY is closed, and bus tie circuit breaker DLX is always in the closed position. The operating principle is the same, and the protection action is opposite.

7. A relay protection method for eliminating busbar dead zone according to claim 1, characterized in that: The method for determining the busbar separate and parallel operation status is as follows: The tripping positions of bus tie circuit breaker DLX and bus tie circuit breaker DLY are TWJ X and TWJ Y When TWJ=0, the circuit breaker is in the closed position, and when TWJ=1, the circuit breaker is in the open position; when both bus tie circuit breakers are in the closed position, the double busbars are determined to be operating in parallel, and when any one of the two bus tie circuit breakers is in the open position, the double busbars are determined to be operating in separate positions.

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