CN108683161B - Differential backup protection method applied to intelligent power distribution network - Google Patents

Differential backup protection method applied to intelligent power distribution network Download PDF

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CN108683161B
CN108683161B CN201810551482.8A CN201810551482A CN108683161B CN 108683161 B CN108683161 B CN 108683161B CN 201810551482 A CN201810551482 A CN 201810551482A CN 108683161 B CN108683161 B CN 108683161B
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differential
backup
main
protection
fault
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CN108683161A (en
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李稳国
陈春
王祎枭
李勇
曹一家
姜鹏
邹勇军
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Hunan Shiyou Electric Power Technology Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations

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Abstract

The invention discloses a differential backup protection method applied to an intelligent power distribution network, which comprises the following steps: the method comprises the following steps: communication detection and communication fault processing; step two: CT detection and CT fault processing; step three: main protection; step four: and (4) backup protection. The invention applies distributed differential protection to backup protection, and combines main protection and backup protection. When a secondary side fault occurs, and a primary side fault occurs in a secondary side fault area, the main protection fails, the backup protection can trip correctly, only the fault range is expanded to the upper level, the backup protection time is close to the main protection time, the protection speed is high, and when the primary side fault occurs outside the secondary side fault area, the main protection acts correctly, and the backup protection does not malfunction; under the condition of refusing action, the mode becomes an active backup protection mode, and backup bit supplement is required by bit supplement information sent out in a main differential ring formed by a neighbor and neighbors of the neighbor; faster than the traditional bit-filling mode.

Description

Differential backup protection method applied to intelligent power distribution network
Technical Field
The invention relates to the field of power distribution, in particular to a differential backup protection method applied to an intelligent power distribution network.
Background
With the development of social economy, the requirement of a user side on power supply reliability is higher and higher, and in order to provide safe and high-quality electric power, the application of an electronic power technology in an intelligent power grid and the application of a distributed power grid to aspects such as power system planning, power quality, relay protection and reliability are all played. For a power distribution system with distributed power sources, the customization of conventional current protection is difficult to determine due to the randomness of the power source processing. In a traditional power distribution network protection system, staged current protection including current flow rate interruption protection, time-limited current quick interruption protection and time-limited overcurrent protection exists, but with the access of a distributed power system, problems of protection dead zones, parameter setting, sensitivity and the like exist, and feeder protection based on a recloser mode causes a wide power failure range, long power failure time and a backup protection function is insufficient. The feeder automation protection system based on centralized communication, the feeder automation protection system taking centralized control as a core and the wide area measurement and control and protection system based on the synchronous vector measurement unit can acquire the global information of the power distribution network and can coordinate and optimize the whole system. However, such a protection method based on centralized communication and centralized control has problems of information transmission congestion and large calculation amount when a power distribution network fails, and particularly, the response speed of backup protection is slow.
In distributed differential protection in recent years, a fast communication network and a kirchhoff current law-based differential protection principle are utilized, multi-terminal electric quantity is adopted to judge faults, response speed is high, the system is not influenced by system oscillation, and the distributed differential protection has the advantages of excellent phase selection capability and the like and is used as main protection all the time. Unfortunately, since each communication node only communicates with its neighbor node in communication, a communication channel without backup protection is not available, and has not been practically applied in the field of backup protection.
Disclosure of Invention
In order to solve the technical problems, the invention provides a differential backup protection method which is simple in algorithm, safe and reliable and is applied to an intelligent power distribution network.
The technical scheme for solving the problems is as follows: a differential backup protection method applied to an intelligent power distribution network comprises the following steps:
1) each intelligent feeder terminal periodically performs communication frame detection with the neighbor intelligent feeder terminals, and the step 2) is performed;
2) judging whether a communication fault occurs between the intelligent feeder terminal and the adjacent intelligent feeder terminal, if so, entering the step 3), otherwise, turning to the step 6);
3) judging whether all communication links of the intelligent feeder terminal are in fault, if so, turning to the step 5); otherwise, the communication fault of the neighbor intelligent feeder terminal is detected, and the step 4) is carried out;
4) identifying the fault of the communication link with the neighbor, locking the main protection containing the fault communication link, reporting to the main station, and turning to the step 6);
5) starting three-section protection and reporting to the master station, and then turning to the step 20);
6) each intelligent feeder terminal periodically performs CT disconnection detection, and the step 7) is performed;
7) judging whether each intelligent feeder terminal CT is disconnected, if so, entering a step 8), and otherwise, turning to a step 9);
8) locking a circuit breaker with CT broken lines, namely locking a main protection of the circuit breaker with the CT broken lines, reporting to a main station, and then turning to the step 20);
9) judging whether the self intelligent feeder terminal meets the protection starting condition, if so, entering the step 10), otherwise, turning to the step 18);
10) exchanging current information between the self intelligent feeder terminal and the neighbor intelligent feeder terminals, performing main differential calculation, exchanging current information with all neighbor intelligent feeder terminals, performing backup differential calculation, and then entering step 11);
11) judging whether the main differential ring is in fault, if so, turning to the step 15); otherwise go to step 12);
12) judging whether the backup differential ring is in fault, if so, entering a step 13), and otherwise, turning to a step 18);
13) judging whether a CT fault or a communication fault exists in the backup differential ring, if so, turning to a step 15), and if not, entering a step 14);
14) judging whether a main differential ring formed by the neighbor circuit breakers and the neighbor circuit breakers in the backup differential ring has circuit breaker refusal, if yes, entering the step 15), and if not, turning to the step 18);
15) outputting a tripping command of the circuit breaker, and entering step 16);
16) judging whether the breaker rejects, if yes, entering the step 17), and if not, turning to the step 20);
17) sending neighbor bit-filling information and reporting to the master station, and turning to step 20);
18) judging whether the neighbor bit complementing information is received and a tripping command is not output, if so, entering a step 19), and otherwise, turning to a step 20);
19) outputting a tripping command of the circuit breaker, and entering the step 20);
20) the routine is ended.
In the differential backup protection method applied to the intelligent power distribution network, in the step 2), the criterion for judging the communication fault between the intelligent feeder terminal of the self and the intelligent feeder terminal of the neighbor is as follows: the self intelligent feeder line terminal sends a communication detection frame to the neighbor intelligent feeder line terminal for multiple times, but does not receive any reply information;
in the step 3), the criterion for judging that all communication links of the intelligent feeder terminal have faults is as follows: communication link faults exist between the self intelligent feeder terminal and all the neighbor intelligent feeder terminals.
In the differential backup protection method applied to the intelligent power distribution network, in the step 7), the criterion for judging the disconnection of the CT is as follows: satisfies the following formula
Figure BDA0001680346840000041
Wherein:
Figure BDA0001680346840000042
zero sequence current on two sides;
Figure BDA0001680346840000043
the current of the current: a, B, C three-phase difference current is firstly calculated respectively
Figure BDA0001680346840000044
Judging the phase with the maximum phase difference current, and recording the phase difference current as the current of the phase with the maximum phase difference current
Figure BDA0001680346840000045
IMKFor a predetermined threshold value equal to 6% In，InRated current; i isWIThe no current threshold.
In the above differential backup protection method applied to the smart distribution network, in step 8), the main protection lockout of the circuit breaker including the CT disconnection means: the main differential protection lock formed by the CT broken intelligent feeder line terminal and all the neighbor intelligent feeder line terminals is locked, and the number of differential rings and the main differential protection are provided for the number of neighbors of the CT broken intelligent feeder line terminal.
In the step 9), the starting criterion for protecting the starting condition is that the starting element comprises a current variation starting element, a zero sequence overcurrent starting element, a phase overcurrent starting element and a voltage auxiliary starting element, and the starting element is considered to be started as long as one of the elements acts, so that the protection starting condition is met.
In the above differential backup protection method applied to the smart distribution network, in step 11), the definition of the main differential ring is as follows: for the structure in the form of a ring main unit, the structure comprises two differential rings, namely a bus self differential ring and a differential ring formed by the opposite sides of the adjacent ring main units;
the fault criterion in the main differential ring is as follows: the mathematical expression that satisfies the action logic is:
Figure BDA0001680346840000046
the current flowing through the protective circuits at two ends of the line is defined as the positive direction of the bus flowing to the protected line
Figure BDA0001680346840000047
Using the sum of the two-terminal current vectors as the action current I of the differential relaydUsing the vector difference of the currents at two ends as the braking current I of the differential relayrI.e. by
Figure BDA0001680346840000051
IqdTo start the current, KrIs the braking coefficient.
In the above differential backup protection method applied to the smart distribution network, in step 12), the backup differential ring is defined as: the boundary of any main differential ring of the self circuit breaker and the main differential ring containing the neighbor circuit breakers but not containing the self circuit breaker is used as a backup differential ring; the number of backup differential rings of the circuit breaker is equal to the number of neighbors which are not boundary switches;
in the step 12), the fault criterion in the backup differential ring is as follows: satisfy the requirement ofThe mathematical expression of the action logic is:
Figure BDA0001680346840000052
in the differential backup protection method applied to the intelligent power distribution network, in the step 13), the criterion of the backup differential intra-loop communication or CT fault is as follows: and judging that the main protections of two main differential rings in the backup differential ring are locked by CT disconnection or the main protection of one main differential ring in the backup differential ring is locked by communication.
In the differential backup protection method applied to the intelligent power distribution network, in the step 14), the criterion for judging the failure of the neighbor circuit breaker is as follows: the backup differential ring judges the fault, the main differential ring in the backup differential ring can not judge the fault, but the main differential ring composed of the neighbor circuit breakers and the neighbor circuit breakers can judge the fault, and the time delay delta T is T after a period of timep+Tpb，TpFor maximum time of tripping of circuit breaker, TpbIf the time margin is the time margin and the overcurrent condition is still met, the circuit breaker at the boundary of each main differential ring in the backup differential ring is judged to be refused to operate.
In the differential backup protection method applied to the intelligent power distribution network, in the step 16), the criterion for judging the failure of the circuit breaker is as follows: the circuit breaker in the main differential ring where the intelligent feeder terminal is located outputs a tripping instruction, and the time delay delta T is T after a period of timep+Tpb，TpFor maximum time of tripping of circuit breaker, TpbAnd if the time margin is, the trip in-place information of the circuit breaker is not set, and the circuit breaker is judged to be refused to operate.
The invention has the beneficial effects that: the invention applies distributed differential protection to backup protection, and compared with the prior main protection, the backup calculation in the backup differential ring is increased. When secondary side faults (CT disconnection and communication faults) occur, and primary side faults occur in a secondary side fault area, main protection fails, backup protection can trip correctly, only the fault range is expanded to the upper level, the backup protection time is close to the main protection time, a speed block is protected, when the primary side faults occur outside the secondary side fault area, the main protection acts correctly, and the backup protection is not tripped; under the condition of refusing action, the mode becomes an active backup protection mode, and backup bit supplement is required by bit supplement information sent out in a main differential ring formed by a neighbor and neighbors of the neighbor; faster than the traditional bit-filling mode.
Drawings
FIG. 1 is a detailed flow chart of the present invention.
FIG. 2 is a schematic view of a primary differential ring and a backup differential ring.
FIG. 3 is a backup differential ring definition diagram.
Detailed Description
The invention is further described below with reference to the figures and examples.
As shown in fig. 1, a differential backup protection method applied to a smart distribution network includes the following steps: the method comprises the following steps: communication detection and communication fault processing; step two: CT detection and CT fault processing; step three: main protection; step four: and (4) backup protection. The method comprises the following specific steps:
1) and (3) each intelligent feeder terminal (short for terminal) periodically performs communication frame detection with the neighbor terminal, and the step 2) is carried out.
2) And (4) judging whether a communication fault occurs between the self terminal and the neighbor terminal, if so, entering the step 3), and otherwise, turning to the step 6).
The criterion for judging the communication fault between the terminal and the neighbor terminal is as follows: the self terminal sends a communication detection frame to the neighbor terminal for many times, but does not receive any reply information.
3) Judging whether all communication links of the terminal are in fault, if so, turning to the step 5); otherwise, it means that the neighbor terminal has communication failure, and step 4) is entered.
The criterion for judging the faults of all communication links of the terminal is as follows: the self terminal and all the neighbor terminals have communication link faults.
4) And identifying the fault of the communication link with the neighbor, locking the main protection containing the fault communication link, reporting to the main station, if a plurality of communication link faults exist, locking a plurality of main protections, and turning to the step 6).
5) And (4) starting three-section protection and reporting to the master station, and then turning to the step 20).
6) Each terminal periodically performs CT disconnection detection, and the process proceeds to step 7).
7) And (4) judging whether each terminal CT is broken, if so, entering the step 8), and otherwise, turning to the step 9).
The criterion for judging CT disconnection is as follows: satisfies the following formula
Figure BDA0001680346840000071
Wherein:
Figure BDA0001680346840000072
zero sequence current on two sides;
Figure BDA0001680346840000073
the current of the current: a, B, C three-phase difference current is firstly calculated respectively
Figure BDA0001680346840000074
Judging the phase with the maximum phase difference current, and recording the phase difference current as the current of the phase with the maximum phase difference current
Figure BDA0001680346840000075
IMKFor a predetermined threshold value equal to 6% In，InRated current; i isWIThe no current threshold.
8) And (3) locking the circuit breaker with the CT broken line, locking the main protection of the circuit breaker with the CT broken line, reporting to the main station, and then turning to the step 20).
The main protection lockout of a circuit breaker containing a CT break refers to: the terminal of CT broken line and all the neighbors form the main differential protection lock, and the number of the differential rings and the main differential protection are provided for the number of the neighbors of the terminal of CT broken line. For example: as shown in FIG. 2, when RMU1-S2 has a CT disconnection, both main differential ring PDR1 and PDR2 are mainly protected and locked.
9) Judging whether the self terminal meets the protection starting condition, if so, entering the step 10), otherwise, turning to the step 18).
The starting criteria of the main (or backup) protection starting condition are that the starting element mainly comprises 4 parts: the starting device comprises a current variation starting element, a zero sequence overcurrent starting element, a phase overcurrent starting element and a voltage auxiliary starting element, wherein the starting element is considered to be started as long as one of the elements acts, and the protection starting condition is met. The current starting element and the voltage auxiliary starting element are taken as phases under normal conditions.
10) Exchanging current information between the self terminal and the neighbor terminals and carrying out main differential calculation, exchanging current information with the neighbor terminals of all the neighbors and carrying out backup differential calculation, and then entering step 11);
11) judging whether the main differential ring is in fault, if so, turning to the step 15); otherwise step 12) is entered.
The definition of the main differential ring is: for a ring main unit type structure, only two differential rings are usually included, i.e. a bus self differential ring and a differential ring formed by the opposite side of the adjacent ring main unit. For example, as shown in fig. 2, RMUs 2-S1 include a bus bar self differential ring PDR3 and a main differential ring PDR2 formed on the opposite side of the adjacent ring main units.
The fault criterion in the main differential ring is as follows: the mathematical expression that satisfies the action logic is:
Figure BDA0001680346840000081
the current flowing through the protective circuits at two ends of the line is defined as the positive direction of the bus flowing to the protected line
Figure BDA0001680346840000082
Using the sum of the two-terminal current vectors as the action current I of the differential relaydUsing the vector difference of the currents at two ends as the braking current I of the differential relayrI.e. by
Figure BDA0001680346840000083
IqdTo start the current, KrIs the braking coefficient.
12) Judging whether the backup differential ring is in fault, if so, entering the step 13), otherwise, turning to the step 18).
The back-up differential ring is defined as: the boundary of any main differential ring of its own breaker and the main differential ring containing its neighbor breakers but not its own breaker acts as a backup differential ring. For example: as shown in FIG. 3, RMU2-S1 has 4 neighbors that are not boundary switches (RMU1-S2, RMU2-S2, RMU2-S3, RMU2-S4), then RMU2-S1 has 4 backup differential rings, BDR1, BDR2, BDR3, BDR 4. BDR1 is composed of the boundary of main differential ring PDR2 and PDR1 (including three breakers RMU1-S1, RMU1-S2 and RMU 1-S3); BDR2 is composed of the boundary of main differential ring PDR3 and PDR6 (including four breakers RMU2-S2, RMU2-S3, RMU2-S4, RMU 5-S1); BDR3 is composed of the boundary of main differential ring PDR3 and PDR4 (including four breakers RMU2-S2, RMU2-S3, RMU2-S4, RMU 4-S1); BDR4 is made up of the boundaries of the main differential ring PDR3 and PDR5 (including four circuit breakers RMU2-S2, RMU2-S3, RMU2-S4, RMU 3-S4).
The number of backup differential rings of the own breaker is equal to the number of neighbors which are not boundary switches. For example: as shown in FIG. 3, RMUs 5-S1 have 4 neighbors, but one neighbor RMU5-S3 is a boundary switch, so there are only three backup differential rings.
The fault criterion in the backup differential ring is as follows: the mathematical expression that satisfies the action logic is:
Figure BDA0001680346840000091
13) and (4) judging whether the CT fault or the communication fault exists in the backup differential ring, if so, turning to the step 15), and otherwise, entering the step 14).
The criterion of the communication or CT fault in the backup differential ring is as follows: (the backup differential ring has been judged to be faulty before the procedure-the backup differential ring is judged to be faulty, the own primary differential ring in the backup differential ring is not faulty or the primary protection is locked out.) the primary protection of both primary differential rings in the backup differential ring is CT broken line locked out (both primary differential ring CT broken line locking flags are set, meaning that the cross point CT of both primary differential rings is broken), or the primary protection of one primary differential ring in the backup differential ring is communication locked out (both primary differential ring communication fault locking flags are set, meaning that the cross point of both primary differential rings is in communication fault).
For example, (1): in FIG. 2, the fault occurred at F1 and the CT of RMU1-S2 was disconnected (CT disconnection was located upstream of the fault point). The backup differential ring BDR1 can judge the fault, the main differential ring PDR1 and the main differential ring PDR2 are locked and cannot judge the fault, and the BDR1(RMU1-S1, RMU1-S3 and RMU2-S1) backup output is tripped when the criterion is met.
The back-up differential ring BDR0 can also judge the fault due to the CT disconnection of RMU1-S2, but the PDR0 main protection judges no fault, and the main differential ring PDR1 main protection is locked and can not judge the fault. The main protection CT open latch (both main differential ring CT open latch flags are set) condition for both main differential rings in the backup differential ring cannot be met, so the backup differential ring BDR0(CB1, RMU1-S1, RMU1-S3) will not trip by false action.
While the backdifferential ring BDR2 is divided into two cases, (i) double-ended powering: (similarly, the backup differential ring BDR0 described above), the backup differential ring BDR2 can also determine a fault due to a CT disconnection of RMU1-S2, but the PDR3 primary protection determines no fault, and the primary differential ring PDR2 primary protection is locked and cannot determine a fault. The condition of both main protection CT out-of-line latches (both main differential ring CT out-of-line latch flags are set) for both main differential rings in the backup differential ring cannot be met, so the backup differential ring BDR2(RMU2-S1, RMU2-S2, RMU2-S3) will not trip by false action. (ii) Single-ended power supply: the back-up differential ring BDR2 cannot determine a fault due to the CT disconnection of RMU 1-S2. The condition that the backup differential ring has determined a fault cannot be met, so the backup differential ring BDR2(RMU2-S1, RMU2-S2, RMU2-S3) will not trip by false action.
For example, (2): in FIG. 2, the fault occurred at F1 and the CT of RMU2-S1 was disconnected (CT disconnection was located downstream of the fault point). The backup differential ring BDR2 can judge the fault, while the main differential ring PDR2 and the main differential ring PDR3 are locked and can not judge the fault, and the backup output tripping meeting the criteria BDR2(RMU1-S2, RMU2-S2 and RMU2-S3) is realized. Similarly, the BDR1 and the BDR3 do not meet the criterion and do not trip by mistake.
For example, (3): in FIG. 2, the fault occurred at F1 and the CT of RMU2-S2 was disconnected (CT disconnection was outside the fault point). And the main differential ring PDR2 judges the fault and trips normally. And the main differential ring PDR3 and the main differential ring PDR4 are locked and do not perform misoperation, and similarly, the backup differential rings BDR1, BDR2, BDR3 and BDR4 do not meet the criterion condition and do not perform misoperation.
For example, (4): in FIG. 2, the failure occurred at F1 and RMUs 1-S2 failed the communication links with RMUs 2-S1, assuming that the communication link failure was due to a RMU1-S2 node being a communication failure (located within the physical failure zone, with the communication failure node located upstream of the failure point). The backup differential ring BDR1 can judge the fault, the main differential ring PDR1 and the main protection PDR2 are locked due to communication faults and cannot judge the fault, BDR1(RMU1-S1, RMU1-S3 and RMU2-S1) meet the criterion, and backup output is tripped.
And the backup differential ring BDR0 cannot judge the fault and does not meet the criterion condition, so the backup differential ring BDR0 cannot be tripped by mistake. The backup differential ring BDR2 cannot determine a fault and the PDR3 primary protection determines no fault and the primary differential ring PDR2 primary protection is locked out and cannot determine a fault. The criterion condition cannot be met, so the back-up differential ring BDR2 will not malfunction.
For example, (5): in FIG. 2, the failure occurred at F1 and RMUs 1-S2 failed the communication links with RMUs 2-S1, assuming that the communication link failure was due to a communication failure of RMUs 2-S1 nodes (located within the failure zone, with the communication failure node located downstream of the failure point). The backup differential ring BDR2 can judge the fault, the main differential ring PDR2 and the main protection PDR3 are locked due to communication faults and cannot judge the fault, BDR2(RMU1-S2, RMU2-S2 and RMU2-S3) meet the criterion, and backup output is tripped. Similarly, the BDR1 and the BDR3 do not meet the criterion condition and do not malfunction.
For example, (6): in FIG. 2, the failure occurred at F1 and the node of RMU2-S2 failed in communication (communication link failure was located outside the physical failure point). And the main differential ring PDR2 judges the fault and trips normally. And the main differential ring PDR3 and PDR4 are locked and do not perform misoperation, and the BDR1, the BDR2, the BDR3 and the BDR4 do not meet the criterion condition and do not perform misoperation.
Therefore, when a secondary side fault (CT disconnection and communication fault) occurs and a primary side fault occurs in a secondary side fault area, the main protection fails, the backup protection can be tripped correctly, only the fault range is expanded to the previous stage, and the backup protection time is close to the main protection time, so that the speed is ultra-fast. And when the primary side fault occurs outside the secondary side fault area, the main protection acts correctly, and the backup protection does not act mistakenly.
14) Judging whether a circuit breaker refuses to operate in a main differential ring formed by the neighbor circuit breakers and the neighbor circuit breakers in the backup differential ring, if yes, entering the step 15), and if not, turning to the step 18).
The criterion for judging the failure of the neighbor circuit breaker is as follows: the backup differential ring judges the fault, the main differential ring in the backup differential ring can not judge the fault, but the main differential ring composed of the neighbor and the neighbor of the neighbor can judge the fault, and the time delay delta T after a period of time is Tp+Tpb，TpFor maximum time of tripping of circuit breaker, TpbIf the time margin is the time margin and the overcurrent condition is still met, the circuit breaker at the boundary of each main differential ring in the backup differential ring is judged to be refused to operate. The mode becomes an active backup protection mode, and the backup bit supplement is required by the bit supplement information sent out in a main differential ring formed by a neighbor and neighbors of the neighbor; and therefore faster than the conventional bit-filling method.
For example, (7): in fig. 2, the fault occurred at F1 and RMU1-S2 failed (the failed breaker was located upstream of the fault point), the main differential ring PDR2 can determine the fault, the backup differential ring BDR1 at the end of RMU1 determines the fault, while the own main differential ring PDR1 in the backup differential ring cannot determine the fault, and the main differential ring PDR2 composed of the neighbor and the neighbor' S neighbors can determine the fault. Time delay delta T after a period of timep+TpbAnd (4) judging that the circuit breaker at the junction of the main differential ring PDR2 and the PDR1 in the backup differential ring BDR1 refuses to operate if the overcurrent condition is still met.
15) And outputting a breaker tripping command and entering the step 16).
16) Judging whether the breaker rejects, if yes, entering the step 17), otherwise, turning to the step 20).
The criterion for judging the failure of the breaker is as follows: the circuit breaker in the main differential ring where the terminal is located outputs a tripping instruction, and the time delay delta T is T after a period of timep+Tpb(TpFor maximum time of tripping of circuit breaker, TpbTime margin), the trip in-place information of the circuit breaker is not set, and the circuit breaker is judged to be refused to operate.
For example, (8): in FIG. 2, the fault occurred at F1 and the rejection of RMU2-S1 (the circuit breaker that rejected was located so)Downstream of the fault point), the primary differential ring PDR2 can determine the fault, the backup differential ring BDR2 at the end of the RMU2 can determine the fault, while the own primary differential ring PDR3 in the backup differential ring cannot determine the fault, and the primary differential ring PDR2 consisting of the neighbor breaker and the neighbor's neighbor breaker can determine the fault. Time delay delta T after a period of timep+Tpb(TpFor maximum time of tripping of circuit breaker, TpbTime margin), an overcurrent condition has not been met and a circuit breaker failure at the interface of primary differential ring PDR2 and PDR1 within backup differential ring BDR1 cannot be determined. Of particular note is that this criterion has limitations: when single-end power supply is carried out, the backup method cannot carry out backup tripping on the refused action of the downstream circuit breaker with the fault, and only can carry out the backup tripping by adopting the position supplementing information for judging the refused action of the main differential ring.
17) And (5) sending neighbor bit-filling information and reporting to the master station, and turning to the step 20).
18) Judging whether the neighbor bit complement information is received and no tripping command is output, if so, entering the step 19), otherwise, turning to the step 20).
Receiving the bit-filling information and outputting no tripping command criterion: 1) receiving the complement bit information, and 2) not outputting the tripping command.
Description of the drawings: 2) not outputting a trip command means excluding steps 14) and 15), so if a rejection occurs upstream of the fault zone, the backup active has tripped before receiving the complement information. And particularly, the refusal occurs at the downstream of the fault area, and the nonradiative structure has no DG, which means that the backup cannot identify whether the neighbor refuses to operate, and the backup needs to identify the circuit breaker refusal removal steps 16) and 17). Therefore, the criterion is as follows: 1) receiving the complement bit information, and 2) not outputting the tripping command, in particular to the latter.
19) And outputting a breaker tripping instruction, and entering the step 20).
20) The routine is ended.

Claims (6)

1. A differential backup protection method applied to an intelligent power distribution network comprises the following steps:
1) each intelligent feeder terminal periodically performs communication frame detection with the neighbor intelligent feeder terminals, and the step 2) is performed;
2) judging whether a communication fault occurs between the intelligent feeder terminal and the adjacent intelligent feeder terminal, if so, entering the step 3), otherwise, turning to the step 6);
3) judging whether all communication links of the intelligent feeder terminal are in fault, if so, turning to the step 5); otherwise, the communication fault of the neighbor intelligent feeder terminal is detected, and the step 4) is carried out;
4) identifying the fault of the communication link with the neighbor, locking the main protection containing the fault communication link, reporting to the main station, and turning to the step 6);
5) starting three-section protection and reporting to the master station, and then turning to the step 20);
6) each intelligent feeder terminal periodically performs CT disconnection detection, and the step 7) is performed;
7) judging whether each intelligent feeder terminal CT is disconnected, if so, entering a step 8), and otherwise, turning to a step 9);
8) locking a circuit breaker with CT broken lines, namely locking a main protection of the circuit breaker with the CT broken lines, reporting to a main station, and then turning to the step 20);
9) judging whether the self intelligent feeder terminal meets the protection starting condition, if so, entering the step 10), otherwise, turning to the step 18);
10) exchanging current information between the self intelligent feeder terminal and the neighbor intelligent feeder terminals, performing main differential calculation, exchanging current information with all neighbor intelligent feeder terminals, performing backup differential calculation, and then entering step 11);
11) judging whether the main differential ring is in fault, if so, turning to the step 15); otherwise go to step 12);
in the step 11), the definition of the main differential ring is as follows: for the structure in the form of a ring main unit, the structure comprises two differential rings, namely a bus self differential ring and a differential ring formed by the opposite sides of the adjacent ring main units;
the fault criterion in the main differential ring is as follows: the mathematical expression that satisfies the action logic is:
Figure FDA0002360704260000021
the protection circuit is regulated to flow through two ends of the line by taking the bus flow direction to the protected line as the positive directionCurrent of
Figure FDA0002360704260000022
Using the sum of the two-terminal current vectors as the action current I of the differential relaydUsing the vector difference of the currents at two ends as the braking current I of the differential relayrI.e. by
Figure FDA0002360704260000023
IqdTo start the current, KrIs the braking coefficient;
12) judging whether the backup differential ring is in fault, if so, entering a step 13), and otherwise, turning to a step 18);
in the step 12), the definition of the backup differential ring is as follows: the boundary of any main differential ring of the self circuit breaker and the main differential ring containing the neighbor circuit breakers but not containing the self circuit breaker is used as a backup differential ring; the number of backup differential rings of the circuit breaker is equal to the number of neighbors which are not boundary switches;
in the step 12), the fault criterion in the backup differential ring is as follows: the mathematical expression that satisfies the action logic is:
Figure FDA0002360704260000024
13) judging whether a CT fault or a communication fault exists in the backup differential ring, if so, turning to a step 15), and if not, entering a step 14);
14) judging whether a main differential ring formed by the neighbor circuit breakers and the neighbor circuit breakers in the backup differential ring has circuit breaker refusal, if yes, entering the step 15), and if not, turning to the step 18);
the criterion for judging the failure of the neighbor circuit breaker is as follows: the backup differential ring judges the fault, the main differential ring in the backup differential ring can not judge the fault, but the main differential ring composed of the neighbor circuit breakers and the neighbor circuit breakers can judge the fault, and the time delay delta T is T after a period of timep+Tpb，TpFor maximum time of tripping of circuit breaker, TpbIf the time margin is the same as the time margin and the overcurrent condition is still met, judging that each main differential motion in the backup differential ring is in the standby differential ringThe circuit breaker at the ring boundary refuses to operate;
15) outputting a tripping command of the circuit breaker, and entering step 16);
16) judging whether the breaker rejects, if yes, entering the step 17), and if not, turning to the step 20);
the criterion for judging the failure of the breaker is as follows: the circuit breaker in the main differential ring where the intelligent feeder terminal is located outputs a tripping instruction, and the time delay delta T is T after a period of timep+Tpb，TpFor maximum time of tripping of circuit breaker, TpbIf the time margin is, the in-place tripping information of the circuit breaker is not set, and the circuit breaker is judged to be refused to operate;
17) sending neighbor bit-filling information and reporting to the master station, and turning to step 20);
18) judging whether the neighbor bit complementing information is received and a tripping command is not output, if so, entering a step 19), and otherwise, turning to a step 20);
19) outputting a tripping command of the circuit breaker, and entering the step 20);
20) the routine is ended.
2. The differential backup protection method applied to the intelligent distribution network according to claim 1, wherein in the step 2), the criterion for judging the occurrence of the communication fault between the own intelligent feeder terminal and the neighbor intelligent feeder terminal is as follows: the self intelligent feeder line terminal sends a communication detection frame to the neighbor intelligent feeder line terminal for multiple times, but does not receive any reply information;
in the step 3), the criterion for judging that all communication links of the intelligent feeder terminal have faults is as follows: communication link faults exist between the self intelligent feeder terminal and all the neighbor intelligent feeder terminals.
3. The differential backup protection method applied to the intelligent power distribution network according to claim 1, wherein in the step 7), the criterion for judging the disconnection of the CT is as follows: satisfies the following formula
Figure FDA0002360704260000031
Wherein
Figure FDA0002360704260000032
Zero sequence current on two sides;
Figure FDA0002360704260000033
the current of the current: a, B, C three-phase difference current is firstly calculated respectively
Figure FDA0002360704260000034
Judging the phase with the maximum phase difference current, and recording the phase difference current as the current of the phase with the maximum phase difference current
Figure FDA0002360704260000041
IMKFor a predetermined threshold value equal to 6% In，InRated current; i isWIThe no current threshold.
4. The differential backup protection method applied to the intelligent power distribution network according to claim 1, wherein in the step 8), the main protection lockout of the circuit breaker including the CT disconnection means: the main differential protection lock formed by the CT broken intelligent feeder line terminal and all the neighbor intelligent feeder line terminals is locked, and the number of differential rings and the main differential protection are provided for the number of neighbors of the CT broken intelligent feeder line terminal.
5. The differential backup protection method applied to the intelligent power distribution network according to claim 1, wherein in the step 9), the starting criterion for protecting the starting condition is that the starting element comprises a current variation starting element, a zero sequence overcurrent starting element, a phase overcurrent starting element and a voltage auxiliary starting element, and as long as one of the elements is operated, the starting element is considered to be started, so that the protection starting condition is met.
6. The differential backup protection method applied to the intelligent power distribution network according to claim 1, wherein in the step 13), the criterion of the backup differential intra-loop communication or CT fault is as follows: and judging that the main protections of two main differential rings in the backup differential ring are locked by CT disconnection or the main protection of one main differential ring in the backup differential ring is locked by communication.
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