CN112018733B - Regional differential protection method applied to feeder automation - Google Patents
Regional differential protection method applied to feeder automation Download PDFInfo
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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
- 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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- 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
- H02H7/262—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 involving transmissions of switching or blocking orders
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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
- 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
- H02H7/263—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 involving transmissions of measured values
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Abstract
The invention discloses a regional differential protection method applied to feeder automation, and relates to the field of intelligent power grids and distribution automation. At present, the conventional feeder line has the problem of repeated power failure impact of users with non-fault paths. The invention comprises the following steps: communication synchronicity confirmation; confirming the communication validity, namely confirming the communication validity of the latest sampling point number after the unit confirms the communication synchronism; calculating analog quantity data; and performing area differential protection judgment according to the sigma I value. The technical scheme solves the defects of the conventional FA, does not cause power failure of the whole distribution line when the distribution line fails, and avoids repeated power failure impact on non-fault path users in the fault isolation and power restoration processes. The problem of distribution network protection cooperation under ring network structure and distributed generator access environment is solved. The application object is not limited to a single radiation type network any more, and can be applied to a power distribution primary network frame with any complex ring network structure, and the application range is wide.
Description
Technical Field
The invention relates to the field of intelligent power grids and distribution automation, in particular to a regional differential protection method applied to feeder automation.
Background
Feeder automation (feeder automation) is the basis of Distribution Automation (DA) and is the most central content of distribution automation. At present, in a feeder automation project implemented in China, a single-radiation type network is generally used. Even if the distribution primary net rack has a ring network structure, in actual operation, the disconnection interconnection switch adopts an open-loop operation mode, so that the single-radiation type network design is still adopted when the feeder automation project construction is implemented. On the one hand, realize through feeder automation that switching power supply function is one of feeder automation's main purpose, on the other hand, when implementing feeder automation project, consider based on single radiation type network again, be to some extent to the breach of feeder automation original intention, also be to the breach of distribution once rack looped netowrk structural design individual and transformation purpose, be especially to the waste of distribution automation construction investment.
With the introduction of Distributed Generation (DG), the operation and management of conventional distribution networks has become more complex. In a certain sense, each distributed power supply and the original single-radiation type network form a miniature power distribution ring network structure. Compared with the conventional power distribution ring network structure with double-side power supply, the access of a large number of distributed power supplies is a more complex power distribution network with a mesh-shaped multi-ring network structure. Since the distribution ring network structure is unavoidable, DA and feeder automation must be designed and built for the ring network structure.
Protection and distribution automation in the ring network structure and distributed power supply access environment need to consider the bidirectionality of the tidal current and the fault current, the difference of the fault current in different directions and the difference of corresponding protection fixed values. Since the conventional protection configuration and the conventional feeder automation (such as voltage time feeder automation and voltage current time feeder automation) cannot meet the requirements, a completely new idea is required in the design of the protection configuration and the feeder automation project.
The conventional feeder automation technology, whether centralized feeder automation or local feeder automation technologies such as voltage time feeder automation, voltage current time feeder automation and adaptive comprehensive feeder automation, has the following defects:
(1) when a fault occurs, the outgoing line switch of the transformer substation trips to cause power failure of the whole line. For the in-situ feeder automation, a reclosing function from one time to three times is required to be set on a substation outgoing line breaker, multiple impacts are caused to a line in the fault isolation and power supply recovery processes, and a user on a non-fault path can feel multiple times of power failure and power restoration.
(2) The conventional feeder automation is a technical scheme developed for a single-radiation network, and when the feeder automation is applied to a primary power distribution network frame with a ring network structure, a connection switch must be disconnected to adopt an open-loop operation mode, so that the construction investment of power distribution automation is wasted
(3) For a multi-connection line, after the operation mode is changed, in order to ensure the correct action of the feeder automation, the protection constant value needs to be adjusted, and especially, the adjustment of the protection constant value of the line with multiple branches and sectionalizers on the branches is very complicated. Further, for distribution networks in a distributed power access environment, conventional protection may be ineffective or insensitive due to DG injection, or adjustment of the protection settings may become impossible.
Disclosure of Invention
The technical problem to be solved and the technical task provided by the invention are to perfect and improve the prior technical scheme, and provide a regional differential protection method applied to feeder automation, so as to achieve the purpose of reducing repeated power failure impact of a user on a non-fault path. Therefore, the invention adopts the following technical scheme.
A regional differential protection method applied to feeder automation comprises the following steps:
1) communication synchronization confirmation
After the node unit is reset to operate, the latest sampling point number of the receiving unit is fed back by the node unit to carry out communication synchronism confirmation;
2) communication validity confirmation
After the unit communication synchronism is confirmed, the communication validity of the latest sampling point number is confirmed;
3) analog data calculation
After data communication synchronization and validity confirmation, calculating once analog quantity data including voltage quantity and current quantity when the latest sampling point number is equal to integral multiple of the sampling point number of each cycle, and obtaining sigma I of each area;
4) according to the sigma I value, performing regional differential protection judgment;
401) judging and processing faults of the closed regions, namely judging that the faults are located in the region as long as Σ I > Id for any closed region, and immediately starting protective tripping operation by all switches corresponding to the region;
402) judging and processing faults aiming at the non-closed area; aiming at any non-closed area, if only one node in the area detects fault current, the fault is judged to be in the area, and all switches corresponding to the area immediately start protection tripping;
403) performing failure treatment; when the voltage and current data synchronization fails, namely the data synchronization and the effectiveness cannot be guaranteed, the power distribution terminal automatically exits from a regional differential protection mechanism and is subjected to conventional protection to be responsible for fault judgment and processing;
404) failure processing; when the power distribution terminal drive switch fails to trip, namely the switch fails to move, the power distribution terminal of the node should immediately inform all the node switches of the other region to which the node belongs to trip and block the switch.
As a preferable technical means: the communication synchronicity confirmation at step 1) includes the steps of:
101) continuously broadcasting for 5 cycles to send the latest sampling point number of the unit and receive the latest sampling point number of each unit on the left and right sides;
102) when data is sent for the second time, the latest sampling point number of the unit and the latest sampling point number of the adjacent unit received last time are sent out;
103) and calculating the difference value between the latest sampling point number sent by the unit last time and the latest sampling point number sent by the unit just now, and judging whether the difference value is less than 5/4 cycle sampling points.
104) When the difference value is less than 5/4 cycle sampling points, the received data is considered to be synchronous, otherwise, the unit received data is synchronously alarmed and the differential protection of the unit area is locked.
105) After data synchronization is confirmed, the sampling point number of the Uab zero-crossing point changed from negative to positive for the first time is set as the latest sampling point number = 0.
As a preferable technical means: the communication validity confirmation in step 2) includes the steps of:
201) continuously broadcasting for 5 cycles to send the latest sampling point number of the unit and receive the latest sampling point number of each unit on the left side and the right side;
202) calculating a difference value of the latest sampling point numbers of the units on the left side and the right side which are received twice adjacently, wherein the difference value is less than the 1/4 cycle sampling point number, the received data is considered to be valid at the moment, otherwise, the unit receives invalid data and alarms, and the differential protection of the unit area is locked; the sampling point number validity self-check is continuously kept during the normal operation of the device.
As a preferable technical means: before the confirmation of communication synchronism and communication validity, the method also comprises the preamble steps: waiting for the trip result to return to judge, judging the failure transfer drive trip, judging the regional differential locking state and judging the closed region; the regional differential protection comprises the following steps:
a) judging whether a trip waiting result is returned or not; if yes, entering step j), if not, entering step b);
b) judging whether the transmission of the drive trip fails or not, if so, entering a step i), and if not, entering a step c);
c) judging whether the locking device is in a regional differential locking state; if yes, entering step l), and if not, entering step d);
d) judging whether the area is a closed area; if not, entering the step e), and if so, entering the step f);
e) judging whether a fault current exists; if yes, entering the step i), and if not, entering the step l);
f) judging whether the data are synchronous and effective, if so, entering a step g), and if not, entering a step l);
g) calculating the sigma I;
h) judging whether the Id is sigma I, if yes, entering the step I), and if not, entering the step l);
i) the drive switch trips and begins to wait for the operation result to return to time;
j) judging whether the action fails; if yes, entering step k), if not, entering step l);
k) transferring the action failure information between areas;
l) switching the process of selecting another area, then returning to step a) until the end.
As a preferable technical means: the application subject of the regional differential protection is an intelligent power distribution terminal matched with a power distribution switch for use), and the application subject is a region of a power distribution network;
the power distribution switch and the intelligent power distribution terminal form a node; the intelligent power distribution terminal realizes data acquisition and can communicate with other adjacent intelligent power distribution terminals, and the intelligent power distribution terminal can also control the tripping/closing of a switch; the control switch comprises a circuit breaker or a load switch;
a differential area, which is called an area for short, is formed by a plurality of nodes and distribution lines surrounded by the nodes; when a boundary switch node exists in the region, the region is a non-closed region, otherwise, the region is a closed region;
any node necessarily belongs to 2 areas and only belongs to 2 areas; the current flowing through a node must be an outgoing current for one region if it is an incoming current for another region, and a negative current for the latter if the former is defined as positive;
when the switch of one node is refused to act, the current of another area to which the node belongs is the switch with the same flow direction to replace the action.
As a preferable technical means: also includes the node definition step; the node includes information:
static information: node type, node identification and node addressing information;
real-time dynamic information: switch state, current magnitude data, voltage magnitude data.
As a preferable technical means: also comprises a region defining step; each region contains at least the following information:
node chain table: node 1, node 2, node 3, node 4, … …;
status flag information: communication synchronization mark, data effective mark, area differential locking mark, action failure area transmission mark, action result return waiting mark and action result return waiting timing;
calculating the value of Σ I.
As a preferable technical means: the power distribution terminal includes at least the following two tasks:
communication maintenance and data collection tasks: synchronous communication between the regional nodes is maintained, and the validity of data is ensured; writing real-time dynamic information data into each node data structure;
and the regional differential protection task realizes the control of regional differential protection.
As a preferable technical means: switch configuration: the circuit breakers are arranged from a substation outgoing switch, a line section switch to a boundary switch;
protection and matching:
conventional protection configuration: three-stage protection is configured for all the switches, wherein the three-stage protection comprises a quick break section, an overcurrent 1 section and an overcurrent 2 section; and under the condition that the regional differential protection mechanism fails, the conventional protection works normally and serves as backup protection of the regional differential protection.
The outgoing line switch node, the sectional switch node and the tail end node of the transformer substation are all circuit breakers, and the three types of nodes have 3-level protection level difference matching through setting of the starting delay and the protection constant value.
As a preferable technical means: the terminal node delay =0ms, all the section switch nodes delay =150ms, and the substation outgoing line switch node delay =250 ms.
Has the advantages that:
1. the method solves the defects of the conventional FA, can not cause the power failure of the whole line when the distribution line fails, and avoids repeated power failure impact on non-fault path users in the process of fault isolation and power supply recovery.
2. The problem of protection and cooperation of a power distribution network under the ring network structure and Distributed Generation (DG) access environment is solved.
3. Based on the FA scheme of the differential protection mechanism, an application object is not limited to a single radiation type network any more, and can be applied to a power distribution primary network frame of any complex ring network structure, including an active power distribution network with a distributed power supply (DG) access environment.
The distribution automation terminal (FTU/DTU) and the Feeder Automation (FA) technology are improved to a new height, the function and the performance of the Feeder Automation (FA) are greatly improved, and the application range of FTU/DTU products and FA technical schemes is expanded. The popularization and application of FA based on regional differential protection promote the improvement of the distribution automation level, thereby greatly improving the operation management level of a distribution network, improving the power supply reliability, bringing economic benefits to power enterprises and bringing immeasurable social benefits.
Drawings
Figure 1 is a diagram of a distribution line in a distributed energy access environment.
Fig. 2 is a diagram illustrating an exemplary application of the area differential protection of the present invention.
Fig. 3 is a flow chart of the present invention.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the drawings in the specification.
As shown in fig. 3, the present invention comprises the steps of:
a) judging whether a trip result is to be returned or not; if yes, entering step j), if not, entering step b);
b) judging whether the transmission of drive tripping fails or not, if so, entering the step i), and if not, entering the step c);
c) judging whether the locking device is in a regional differential locking state or not; if yes, entering step l), and if not, entering step d);
d) judging whether the area is a closed area; if not, entering the step e), and if so, entering the step f);
e) judging whether fault current exists; if yes, entering the step i), and if not, entering the step l);
f) judging whether the data are synchronous and effective, if so, entering a step g), and if not, entering a step l);
g) calculating the sigma I;
h) judging whether the Id is sigma I, if yes, entering the step I), and if not, entering the step l);
i) the drive switch trips and begins to wait for the operation result to return to time;
j) judging whether the action fails; if yes, entering step k), if not, entering step l);
k) transferring the action failure information between the areas;
l) switching the process of selecting another area, then returning to step a) until the end.
The following is a detailed description of some aspects:
summary of the invention
The core content of the invention is as follows 4 items:
(1) for a power distribution network, the concepts of nodes and regions are abstracted, and a node and region relation theorem and a node action transfer theorem based on the concepts of the nodes and the regions are invented.
(2) The invention discloses a voltage and current magnitude data synchronization technology for realizing peer-to-peer communication among switch nodes, which is the realization basis of a regional differential protection mechanism.
(3) The invention discloses an area differential protection mechanism which can be applied to a distribution automation FA scheme, and the distribution automation FA technical scheme constructed based on the area differential protection mechanism can greatly improve the overall technical level of FA and distribution automation.
(4) The invention discloses a program architecture system of a power distribution terminal FTU/DTU product capable of realizing a regional differential protection mechanism, and the architecture system can be used as a universal design idea and a universal design method for design and development of the power distribution terminal FTU/DTU product.
Figure 1 is a typical block diagram of a distribution line in a distributed energy access environment. After introducing the area differential protection technology, the protection constant value is 0 for an area according to kirchhoff's current law and for an area Σ I =0, theoretically, in any environment. The actual protection fixed value should be a certain value Id greater than 0. This Id is independent of the region and only dependent on the individual component sampling and calculation error in Σ I. That is, in the conventional FA technology, the problem that the protection constant adjustment is difficult and cannot be set is completely eliminated in the area differential protection technology.
The problem of constant value setting is solved, the power failure of the whole line caused by the tripping of the outgoing line switch of the transformer substation in the fault processing process in the conventional FA technology, and the impact of repeated reclosure on the line are solved.
2 concept definition and associated theorem
The application subject of the regional differential protection mechanism is an intelligent power distribution terminal (FTU) matched with a power distribution switch for use, and the application subject is a region of a power distribution network. Before discussing the regional differential protection mechanism, the concept of the region is defined, and the concept of the node related to the region concept is as follows:
(1) and (3) node: the power distribution switch and the intelligent power distribution terminal (FTU) are a node. The FTU realizes data acquisition and can communicate with other adjacent FTUs, and the FTU can also control the tripping/closing of a switch (a circuit breaker or a load switch). There are 11 nodes in total in FIG. 1, which are CB1, CB2, S1-S9.
(2) Differential region: a plurality of nodes and distribution lines surrounded by the nodes form a differential area, which is called an area for short. In the distribution network shown in fig. 1, (CB 1, S1, S2), (S2, S3), (S3, S4, S5) are 3 differential areas, the 3 areas respectively have 3, 2, and 3 switching nodes, the switching nodes are boundaries between the inside and outside of the area, and there is no other boundary except for the switching nodes, and the switching nodes are all closed areas.
The node S1 belongs to a demarcation switch node of a subscriber branch line, which is a so-called end node, and part of property right and management behind the node is assigned to a subscriber and does not belong to the jurisdiction of a power distribution department. And the node CB1 is a substation outlet switch node, belongs to a demarcation point of power transformation and distribution, and belongs to a power transformation department for property right and management and also does not belong to the jurisdiction of a power distribution department. For both cases, we define another type of region: a non-enclosed area. The former is represented as (S1, Null) or (Null, S1), and the latter is represented as (CB 1, Null) or (Null, CB 1). The places where the non-enclosed area is distinguished from the enclosed area are: it has a Null boundary for the non-switching node.
For the power distribution network shown in fig. 1, the following 12 areas can be abstracted, wherein 7 areas are closed areas, and 5 areas are non-closed areas:
l region (NULL, CB 1) belonging to a non-enclosed area
l region (CB 1, S1, S2)
l region (S1, NULL) belonging to a non-closed region
l region (S2, S3)
l region (S3, S4, S5)
l region (S5, NULL) belonging to a non-closed region
l region (S4, S6)
l region (S6, S7)
l area (S7, S8, S9)
l region (S9, NULL) belonging to a non-closed region
l region (S8, CB 2)
l area (CB 2, NULL) belonging to a non-enclosed area
(3) Node and region relation theorem: any node necessarily belongs to 2 of the regions, and only 2 regions. The current flowing through a node must be out for one region if it is in for another region and negative if the former is defined as positive.
(4) Node action transmission theorem: if the switch of a node fails, the current of another region to which the node belongs is the same to flow (flow in/out) to replace the action.
3-volt/ampere data synchronization technology
The realization of the regional differential protection mechanism is based on peer-to-peer communication between nodes and synchronization of voltage and current data between the nodes. Therefore, it is necessary to solve the synchronization of the communication between the nodes and to ensure the validity of the data.
1. Communication synchronization confirmation
After the node unit is reset to operate, firstly, the communication synchronism is confirmed by sending the node unit and feeding back the latest sampling point number of the receiving unit. The process is as follows:
l broadcasting and sending the latest sampling point number of the unit continuously for 5 cycles and receiving the latest sampling point number of each unit on the left side and the right side;
when the data is sent for the second time, the latest sampling point number of the unit and the latest sampling point number of the adjacent unit received last time are sent out;
l the difference between the last sent "latest sampling point number" by the unit which calculates the feedback and the last sent "latest sampling point number" by the unit is smaller than the number of 5/4 cycle sampling points.
And l, considering that the received data is synchronous at the moment, otherwise, giving an alarm (self-checking signal) to the unit for receiving the data synchronization, and locking the local unit area differential protection.
After data synchronization is confirmed, the sampling point number of the Uab zero-crossing point which is changed from negative to positive for the first time is regarded as the latest sampling point number =0 ".
2. Communication validity confirmation
After the unit confirms the communication synchronism, the unit should also confirm the communication validity through the latest sampling point number, and the process is designed as follows:
(1) continuously broadcasting for 5 cycles to send the latest sampling point number of the unit and receive the latest sampling point number of each unit on the left and right sides;
(2) and calculating a difference value of the latest sampling point number of each unit on the left side and the right side which are received twice adjacently, wherein the difference value is less than the 1/4 cycle sampling point number, the received data is considered to be valid at the moment, and otherwise, the unit receives invalid data and alarms (self-checking signals) to lock the regional differential protection of the unit. The sampling point number validity self-check should be kept continuously during normal operation of the device.
3. Analog data calculation
After the data communication synchronization and validity confirmation, in order to ensure continuous synchronization, analog quantity data (voltage quantity and current quantity) is calculated once when the latest sampling point number is equal to integral multiple of the sampling point number of each cycle. The sampling point number cannot be readjusted due to the amount of mutation or the like.
Since the synchronization of the data of the switching nodes in a region is ensured and the data is valid, the Σ I of each region can be calculated.
4-zone differential protection mechanism
The theoretical basis of the regional differential protection mechanism is kirchhoff's current law, and aiming at any closed region, when a line is normal, the following constraint conditions are met:
ΣI < Id
however, in the non-closed region, the current value outside the Null view cannot be obtained, and the above-described constraint relationship cannot be obtained.
The control strategies corresponding to the area differential protection mechanism are 4 as follows:
(1) and judging and processing faults of the closed area. For any closed region, as long as Σ I > Id, it is determined that the fault is located in the region, and all switches corresponding to the region immediately start protective tripping.
(2) And (4) fault judgment and processing aiming at the non-closed area. Aiming at any non-closed area, as long as one node in the area detects fault current, the fault is judged to be in the area, and all switches corresponding to the area immediately start protection tripping.
(3) And (5) failure treatment. When the voltage and current data synchronization fails (the data synchronism and the effectiveness cannot be guaranteed), the FTU automatically exits from the regional differential protection mechanism, and is subjected to conventional protection to be responsible for fault judgment and processing.
(4) And (6) failure processing. When the FTU drives the switch to fail to trip (the switch rejects), the FTU of the node should immediately inform all node switches of the other area to which the FTU belongs to trip and lock off the switch.
With the exemplary distribution network of fig. 1, a differential protection mechanism operation analysis is performed for a fault at F1-F5, as in fig. 2.
F1 failure: f1 is located in a non-closed area (S1, NULL), fault current is detected in S1, quick-break protection action is carried out, and S1 is tripped. If the S1 refuses to act, the CB1 and the S2 act to trip.
F2 failure: Σ I (S2, S3) > Id, S2, S3 action trip. If the S2 refuses to act, the CB1 and the S1 act to trip. If the operation is refused at S3, the operation is tripped at S4 and S5.
F3 failure: f1 is located in a non-closed area (S5, NULL), fault current is detected in S5, quick-break protection action is carried out, and S5 is tripped. If the operation is refused at S5, the operations S3 and S4 are tripped.
F4 failure: since the tie switch S6 is in the off state, I (S6) =0, Σ I (S6, S7) > Id, and S7 is tripped. If the operation is refused at S7, the operation is tripped at S8 and S9.
F5 failure: Σ I (S7, S8, S9) > Id, the zone differential protection mechanism initiates the S7, S8, S9 action trip. If S7 refuses to move, S6 is closed due to the S6 is originally in the opening state. If S8 refuses to act, CB2 acts to trip.
5 program architecture system of power distribution terminal product
1. Metadata structure
Node and region type 2 data structures are defined, and these type 2 data structures are treated as metadata structures.
(1) Node description
Describing a node, at least the following information needs to be defined:
l static information: node type, node identification, node addressing information
l real-time dynamic information: switching state, current amount data, and voltage amount data
(2) Region description
For any node, it must belong to and only belong to 2 regions, so 2 regions need to be defined: region 1 and region 2, each region containing at least the following information:
l node chain table (node 1, node 2, node 3, node 4, … …)
l status flag information: communication synchronization flag, data valid flag, area differential latch flag, operation failure area transfer flag, wait operation result return flag, and wait operation result return timing
Sigma-delta I calculated value
2. Program task
The power distribution terminal at least comprises the following two tasks:
(1) communication maintenance and data collection tasks
l maintaining synchronous communication between regional nodes to ensure validity of data
Writing real-time dynamic information data into each node data structure
(2) Regional differential protection task
And l, implementing a control strategy of regional differential protection, as shown in fig. 3.
The basic application technology can be applied to the implementation of FTU/DTU product development and distribution automation FA.
1. FTU/DTU product development
The invention is the expansion of the function of the FTU/DTU product, in particular to the promotion of the protection function of the FTU/DTU product.
When the invention is implemented in the development of FTU/DTU products, the invention can be based on the original hardware platform of the products under the general condition, and does not need to change or add the original hardware platform, but only needs to add the definition of nodes and the area 2 type data structure on the original software platform, and adds a special task aiming at the area differential.
2. Distribution automation FA implementation
The technical scheme of the distribution automation FA with the regional differential protection mechanism is applied on the basis that peer-to-peer communication can be realized between the FTU/DTU. If the DTU is applied to places such as a power distribution room, a switching station and the like, the nodes belong to intra-station communication, and a wired communication mode, such as network communication based on a local area network, can be adopted. If the FTUs are applied to a line switch, the FTUs belong to remote inter-station communication, an optical fiber communication mode can be selected, and a 5G communication mode can be selected after 5G communication in the future.
In addition, the FA based on the area differential protection also has certain requirements on the switch and the protection configuration when the FA is implemented.
(1) Switch arrangement
Based on the FA of the area differential protection, the protection function can drive the switch to trip when the line is in fault, so a breaker instead of a load switch must be configured from a substation outgoing line switch, a line section switch, to a demarcation switch (end node).
(2) Protection fitting
Conventional protection configuration: three-stage protection (quick break, overcurrent 1 stage and overcurrent 2 stage) is configured for all switches (circuit breakers). Under the condition that the regional differential protection mechanism fails, the conventional protection normally works, so the conventional protection is backup protection of the regional differential protection.
The outgoing line switch nodes, the sectional switch nodes and the tail end nodes of the transformer substation are all circuit breakers, the three types of nodes have 3-level protection level difference coordination through setting of starting delay and protection fixed values, and if the tail end node delay =0ms, all the sectional switch nodes delay =150ms, and the outgoing line switch nodes of the transformer substation delay =250 ms.
The regional differential protection method applied to feeder automation shown in fig. 3 is a specific embodiment of the present invention, which already embodies the essential features and advances of the present invention, and can be modified equivalently in shape, structure and the like according to the practical needs and with the teaching of the present invention, and is within the scope of protection of the present solution.
Claims (10)
1. A regional differential protection method applied to feeder automation is characterized by comprising the following steps:
1) communication synchronization confirmation
After the node unit is reset to operate, the latest sampling point number of the receiving unit is fed back by the node unit to carry out communication synchronism confirmation;
2) communication validity confirmation
After the unit communication synchronism is confirmed, the communication validity of the latest sampling point number is confirmed;
3) analog data calculation
After data communication synchronization and validity confirmation, when the latest sampling point number is equal to the integral multiple of the sampling point number of each cycle wave, calculating once analog quantity data including voltage quantity and current quantity to obtain sigma I of each area;
4) according to the sigma I value, judging the regional differential protection;
401) judging and processing faults of the closed regions, namely judging that the faults are located in the region as long as Σ I > Id for any closed region, and immediately starting protective tripping operation by all switches corresponding to the region;
402) judging and processing faults aiming at the non-closed area; aiming at any non-closed area, if only one node in the area detects fault current, the fault is judged to be in the area, and all switches corresponding to the area immediately start protection tripping;
403) performing failure treatment; when the voltage and current magnitude data synchronization fails, namely the data synchronism and effectiveness are not guaranteed, the power distribution terminal automatically exits from a regional differential protection mechanism and is subjected to conventional protection to be responsible for fault judgment and processing;
404) failure processing; when the power distribution terminal drive switch fails to trip, namely the switch refuses to operate, the power distribution terminal of the node immediately informs all the node switches of the other region to which the power distribution terminal belongs to trip, and closes the switch in a locking manner;
the distribution lines surrounded by the nodes form a differential area, which is called an area for short; when the boundary switch node exists in the region, the region is a non-closed region, otherwise, the region is a closed region.
2. The regional differential protection method applied to feeder automation as claimed in claim 1, wherein: the communication synchronicity confirmation in step 1) includes the steps of:
101) continuously broadcasting for 5 cycles to send the latest sampling point number of the unit and receive the latest sampling point number of each unit on the left and right sides;
102) when the data is sent for the second time, the latest sampling point number of the unit and the latest sampling point number of the adjacent unit received for the first time are sent out;
103) calculating the difference value between the latest sampling point number sent by the feedback unit for the first time and the latest sampling point number sent by the feedback unit for the second time, and judging whether the difference value is less than 5/4 cycle sampling points;
104) when the difference value is less than the 5/4 cycle sampling point number, the received data is considered to be synchronous, otherwise, the unit receives data synchronous alarm and locks the unit area differential protection;
105) after data synchronization is confirmed, the sampling point number of the Uab zero-crossing point changed from negative to positive for the first time is set as the latest sampling point number = 0.
3. The regional differential protection method applied to feeder automation as claimed in claim 2, wherein: the communication validity confirmation in step 2) includes the steps of:
201) continuously broadcasting for 5 cycles to send the latest sampling point number of the unit and receive the latest sampling point number of each unit on the left side and the right side;
202) calculating a difference value of the latest sampling point numbers of the units on the left side and the right side received twice adjacently, wherein the difference value is less than the 1/4 cycle sampling point number, the received data is considered to be valid at the moment, otherwise, the unit receives invalid data and alarms, and the differential protection of the unit area is locked; the sampling point number validity self-check is continuously kept during the normal operation of the device.
4. A regional differential protection method applied to feeder automation according to any one of claims 1 to 3, characterized in that: before the confirmation of communication synchronism and communication validity, the method also comprises the preamble steps: waiting for the trip result to return to judge, judging the failure transfer drive trip, judging the regional differential locking state and judging the closed region; the regional differential protection comprises the following steps:
a) judging whether a trip result is to be returned or not; if yes, entering step j), if not, entering step b);
b) judging whether the transmission of the drive trip fails or not, if so, entering a step i), and if not, entering a step c);
c) judging whether the locking device is in a regional differential locking state; if yes, entering step l), and if not, entering step d);
d) judging whether the area is a closed area; if not, entering the step e), and if so, entering the step f);
e) judging whether fault current exists; if yes, entering the step i), and if not, entering the step l);
f) judging whether the data are synchronous and effective, if so, entering a step g), and if not, entering a step l);
g) calculating the sigma I;
h) judging whether the Id is sigma I, if yes, entering the step I), and if not, entering the step l);
i) driving the switch to trip, and starting to wait for the operation result to return to time;
j) judging whether the action fails; if yes, entering step k), if not, entering step l);
k) transferring the action failure information between areas;
l) switching the process of selecting another area, then returning to step a) until the end.
5. The regional differential protection method applied to feeder automation as claimed in claim 4, wherein: the application main body of the regional differential protection is an intelligent power distribution terminal matched with a power distribution switch for use, and an application object is a region of a power distribution network;
the power distribution switch and the intelligent power distribution terminal form a node; the intelligent power distribution terminal realizes data acquisition and can communicate with other adjacent intelligent power distribution terminals, and the intelligent power distribution terminal can also control the tripping/closing of a switch; the control switch comprises a circuit breaker or a load switch;
a plurality of nodes and distribution lines surrounded by the nodes form a differential area, which is called an area for short; when a boundary switch node exists in the region, the region is a non-closed region, otherwise, the region is a closed region;
any node necessarily belongs to 2 areas, and only belongs to 2 areas; the current flowing through a node must be an outgoing current for one region if it is an incoming current for another region, and a negative current for the latter if the former is defined as positive;
when the switch of one node is refused to act, the current of another area to which the node belongs is the switch with the same flow direction to replace the action.
6. The regional differential protection method applied to feeder automation as claimed in claim 5, wherein: also includes the node definition step; the node includes information:
static information: node type, node identification and node addressing information;
real-time dynamic information: switch state, current magnitude data, voltage magnitude data.
7. The regional differential protection method applied to feeder automation as claimed in claim 6, wherein: also comprises a region definition step; each region contains at least the following information:
node chain table: a corresponding node number;
status flag information: communication synchronization mark, data effective mark, area differential locking mark, action failure area transmission mark, action result return waiting mark and action result return waiting timing;
calculating the value of Σ I.
8. The regional differential protection method applied to feeder automation as claimed in claim 1, wherein: the power distribution terminal at least comprises the following two tasks:
communication maintenance and data collection tasks: synchronous communication between the regional nodes is maintained, and the validity of data is ensured; writing real-time dynamic information data into each node data structure;
and the regional differential protection task realizes the control of regional differential protection.
9. The regional differential protection method applied to feeder automation as claimed in claim 8, wherein:
switch configuration: the circuit breakers are arranged from a substation outgoing switch, a line section switch to a boundary switch;
protection and matching:
conventional protection configuration: three-stage protection is configured for all switches, wherein the three-stage protection comprises a quick break section, an overcurrent 1 section and an overcurrent 2 section; under the condition that the regional differential protection mechanism fails, normal protection works normally, and the normal protection is used as backup protection of the regional differential protection;
the outgoing line switch node, the sectional switch node and the tail end node of the transformer substation are all circuit breakers, and the three types of nodes have 3-level protection level difference matching through setting of starting delay and protection fixed values.
10. The regional differential protection method for feeder automation according to claim 9, wherein: the delay of the tail end node is =0ms, the delay of all the section switch nodes is =150ms, and the delay of the substation outlet switch node is =250 ms.
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| CN114977134B (en) * | 2022-08-01 | 2023-03-21 | 广东电网有限责任公司珠海供电局 | Differential protection method for active power distribution network and related device |
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| CN102623966B (en) * | 2012-04-01 | 2015-01-07 | 许继电气股份有限公司 | Differential protection method for bus |
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| EP3136528B1 (en) * | 2015-08-31 | 2020-04-22 | Siemens Aktiengesellschaft | Differential protection method, differential protection device and differential protection system |
| CN108347039A (en) * | 2017-01-24 | 2018-07-31 | 中国电力科学研究院 | A kind of station domain back-up protection method and system based on jump-value of current |
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