Load transfer method for power failure or full stop scene of certain section of 10kV bus of transformer substation

Abstract

The invention discloses a load transfer method for a power failure or full stop scene of a certain section of a 10kV bus of a transformer substation, and the method comprises the following steps: S100, when the 10kV bus of the transformer substation is N-1, classifying the lines of the transformer substation based on the line connection condition, and giving a corresponding load transfer strategy and a transfer load calculation method; and S200, when the transformer substation is fully stopped, classifying the transformer substation lines based on the line connection condition, and giving a corresponding load transfer strategy and a transfer load calculation method. According to the invention, the load transfer rate of the transformer substation under two special conditions that a certain section of 10-kilovolt bus of the transformer substation fails or is maintained and returned and the transformer substation is fully stopped can be improved, the load loss is reduced, and the load transfer capacity of a power distribution network in an urban core area is effectively improved; and the project investment for improving the load transfer capacity under the special fault condition can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of research and analysis of the power supply capacity and load transfer capacity of urban distribution networks. Specifically, it relates to a method for load transfer of a substation in a core urban area under two conditions: a fault or maintenance of a certain 10 kV busbar resulting in its outage, and the complete outage of the substation. Background Art

[0002] In recent years, power supply companies have attached great importance to the construction of distribution networks, continuously increasing investment, and remarkable achievements have been made in the development of distribution networks. At the same time, higher requirements have been put forward for the power supply reliability and high-quality service of the distribution networks in the core urban areas, and it is necessary to further reduce the outage time and outage scope of maintenance and faults, and improve the load transfer capacity of substations under various special conditions. In the core urban area power grids, there are often problems such as tight corridor resources, insufficient substation sites, and heavy loads on substations. Newly built lines often require large investments and high difficulties. With the continuous construction of smart distribution networks, the effective coverage rate and self-healing rate of distribution automation have been gradually improved, providing great support for high-reliability power supply. The commonly used substation load transfer strategies can no longer meet the construction requirements of the distribution networks in the core urban areas, and certain adjustments and optimizations are needed to improve the load transfer capacity of the distribution networks in the core urban areas. Summary of the Invention

[0003] In view of the above technical problems in the related art, the present invention provides a method for load transfer in the scenario of power outage of a certain 10 kV busbar or complete outage of a substation, which can solve the above problems.

[0004] To achieve the above technical objectives, the technical solution of the present invention is realized as follows:

[0005] A method for load transfer in the scenario of power outage of a certain 10 kV busbar or complete outage of a substation includes the following steps:

[0006] S100. When the 10 kV busbar of the substation is in the N-1 state, classify the substation lines based on the line connection situation, and give the corresponding load transfer strategy and the calculation method of the load that can be transferred;

[0007] S110. For lines with different-station connections or same-station different-busbar connections: If the load cannot be completely transferred out through the lines with different-station connections or same-station different-busbar connections, calculate the load that can be transferred according to how much can be transferred;

[0008] S120. For lines with only same-station same-busbar connections: If there are lines with different-station connections or same-station different-busbar connections among the same-busbar lines connected to this line, transfer the load of this line indirectly as much as possible through the same-busbar connection lines;

[0009] S130. For single-radiation or single-injection lines: The load is completely lost;

[0010] S200. When the substation is completely out of service, classify the substation lines based on the line connection situation, and give the corresponding load transfer strategy and the calculation method of the transferable load.

[0011] S210. Lines with inter-station connections: If not all the loads can be transferred out through the inter-station connection lines, calculate the transferable load according to how much can be transferred.

[0012] S220. Lines with only in-station connections: If there are inter-station connection lines for the in-station lines connected to this line, indirectly transfer the load of this line through the in-station connection lines. If there are inter-station connection lines for the lines on the same bus as this line, indirectly transfer the load of this line by reverse-feeding the bus.

[0013] S230. Single-radiation or single-injection lines: If there are inter-station connection lines for the lines on the same bus as this line, indirectly transfer the load of this line by reverse-feeding the bus.

[0014] Furthermore, the transformer is a two-winding transformer, and the low-voltage side is 10 kV for 110 kV substations, 66 kV substations or 35 kV substations; the main wiring diagram of the substation adopts single-bus sectionalized wiring, double-bus wiring or double-bus sectionalized wiring.

[0015] Furthermore, N-1 of the 10 kV bus of the substation means that a certain section of the bus is taken out of service due to a fault or maintenance, that is, a certain section of the 10 kV bus of the substation is de-energized; a complete outage of the substation means that the high-voltage power supply line or the main transformer of the substation is completely out of service, and the 10 kV bus can be operated.

[0016] Furthermore, the calculation formula for the sum of transferable loads L1 in S110 is:

[0017]

[0018] In the formula, L i represents the load directly transferred out through inter-station connection or in-station connection between different buses, and n1 represents the number of lines through which the load can be completely or partially transferred out through inter-station connection or in-station connection between different buses;

[0019] The calculation formula for the sum of transferable loads L2 in S120 is:

[0020]

[0021] In the formula, L j represents the load that can be indirectly transferred out through the same-bus connection lines, and n2 represents the number of lines through which the load can be completely or partially transferred out through the same-bus connection lines.

[0022] Furthermore, when calculating N-1 of the 10 kV bus of the substation, all transferable loads L Z1= L1 + L2, and calculate the proportion of all transferable loads to the sum of the loads of the outgoing lines of this section of the 10 kV bus to obtain the load transferability rate T at N-1 of the 10 kV bus l1 = (L Z1 / L 01 ) × 100%, where L 01 represents the sum of the loads of the outgoing lines of this section of the 10 kV bus.

[0023] Furthermore, the calculation formula for the sum of transferable loads L3 in S210 is:

[0024]

[0025] In the formula, L k represents the load directly transferred out through the inter-station connection line, and n3 represents the number of lines that can transfer all or part of the load through the inter-station connection line;

[0026] The calculation formula for the sum of transferable loads L4 in S220 is:

[0027]

[0028] In the formula, L r represents the load indirectly transferred out through the in-station connection line, n4 represents the number of lines that can transfer all or part of the load through the in-station connection line, and L s represents the load that can be indirectly transferred out by the line of the same bus reversing to supply the bus, and n5 represents the number of lines that can transfer all or part of the load by the line of the same bus reversing to supply the bus;

[0029] The calculation formula for the sum of transferable loads L5 in S230 is:

[0030]

[0031] In the formula, L h represents the load of the single-radiation or single-injection line indirectly transferred out by the line of the same bus reversing to supply the bus, and n6 represents the number of single-radiation or single-injection lines that can transfer all or part of the load by the line of the same bus reversing to supply the bus.

[0032] Furthermore, calculate all transferable loads L Z2 = L3 + L4 + L5 when the substation is completely out of service, and calculate the proportion of all transferable loads to the sum of the loads of the 10 kV outgoing lines of this substation to obtain the load transferability rate T l2 = (L Z2 / L 02 ) × 100%, where L 02 represents the sum of the loads of the 10 kV outgoing lines of this substation.

[0033] Advantages of the present invention: This application can improve the load transfer rate of a substation under two special conditions, namely, when a certain section of the 10-kV busbar of the substation fails or is taken out of service for maintenance, and when the entire substation shuts down. It reduces load losses, effectively improves the load transfer capacity of the distribution network in the core area of the city, and helps to reduce project investment for enhancing the load transfer capacity under special fault conditions. Detailed implementation manners

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention shall fall within the protection scope of the present invention.

[0035] According to the present invention, a load transfer method for a 10-kV busbar outage or full outage scenario of a certain section of a substation is disclosed. The specific method is as follows:

[0036] (1) Load transfer scheme when the 10-kV busbar of the substation is N-1

[0037] When the 10-kV busbar of the substation is N-1, based on the line connection situation, the substation lines are classified and corresponding load transfer strategies and load transferable calculation methods are given.

[0038] 1) For lines with off-site connections or on-site connections between different busbars, calculate the load transferable according to "transfer as much as possible". The sum of the load transferable is L1.

[0039]

[0040] In the formula, L i represents the load directly transferred out through off-site connection or on-site connection between different busbars, and n1 represents the number of lines that can transfer all or part of the load through off-site connection or on-site connection between different busbars.

[0041] 2) For lines with only on-site connections between the same busbars, if there are off-site connections or on-site connections between different busbars for the lines connected to the same busbar as this line, the load of this line can be indirectly transferred as much as possible through the lines connected to the same busbar. The sum of the load transferable is L2.

[0042]

[0043] In the formula: L j represents the load that can be indirectly transferred through the lines connected to the same busbar, and n2 represents the number of lines that can transfer all or part of the load through the lines connected to the same busbar.

[0044] 3) For single-radiation or single-injection lines, all their loads are lost.

[0045] 4) Calculate all transferable loads L when the 10 kV bus of the substation experiences N - 1 contingency by synthesizing the transfer of various types of loads. Z1 = L1 + L2.

[0046] 5) Calculate the ratio of all transferable loads to the sum of the loads of the outgoing lines of this section of the 10 kV bus to obtain the load transferability rate T when the 10 kV bus is in N - 1 contingency. l1 = (L Z1 / L 01 ) × 100%, where L 01 represents the sum of the loads of the outgoing lines of this section of the 10 kV bus.

[0047] (2) Load transfer scheme when the substation is completely out of service

[0048] When the substation is completely out of service, based on the line connection situation, classify the substation lines and give the corresponding load transfer strategies and calculation methods for transferable loads.

[0049] 1) For lines with inter - substation connections, calculate the transferable loads according to "transfer as much as possible", and the sum of their transferable loads is L3.

[0050]

[0051] Where L k represents the load directly transferred out through the inter - substation connection line, and n3 represents the number of lines that can transfer all or part of the load through the inter - substation connection line.

[0052] 2) For lines with only in - substation connections, if the in - substation line connected to this line has an inter - substation connection line, the load of this line can be indirectly transferred out as much as possible through the in - substation connection line; if the line on the same bus as this line has an inter - substation connection line, the load of this line can also be indirectly transferred through the reverse - feeding bus.

[0053]

[0054] Where L r represents the load that can be indirectly transferred out through the in - substation connection line, n4 represents the number of lines that can transfer all or part of the load through the in - substation connection line, L s represents the load that can be indirectly transferred out through the reverse - feeding bus by the line on the same bus, and n5 represents the number of lines that can transfer all or part of the load through the reverse - feeding bus by the line on the same bus.

[0055] 3) For single - radiation or single - injection lines, if the line on the same bus as this line has an inter - substation connection line, the load of this line can be indirectly transferred through the reverse - feeding bus.

[0056]

[0057] Where Lh It represents the load of a single-radiation or single-injection line that can be indirectly transferred out through the line on the same busbar. n6 represents the number of single-radiation or single-injection lines that can transfer all or part of the load out through the line on the same busbar via the reverse busbar connection.

[0058] 4) Considering the load transfer situations of various types comprehensively, calculate all the transferable loads L of the substation when the substation is completely out of service. Z2 = L3 + L4 + L5.

[0059] 5) Calculate the ratio of all the transferable loads to the sum of the loads of the 10 kV feed lines of the substation to obtain the load transferable rate T of the substation when the substation is completely out of service. 12 = (L Z2 / L 02 ) × 100%, where L 02 represents the sum of the loads of the 10 kV feed lines of the substation.

[0060] Advantages of the proposed solution in this application: When analyzing the load transfer in the case of a fault outage of a certain section of the 10 kV busbar of the substation, in addition to the fact that the line can directly transfer the load through the inter-station connection or the connection between different busbars in the same station, it is also considered that if there is an inter-station connection or a connection between different busbars in the same station on the busbar of the same line as this line, the load can be indirectly transferred out through the busbar connection of the same busbar; when analyzing the load transfer in the case of the complete outage of the substation, in addition to the fact that the line can directly transfer the load through the inter-station connection line, it is also considered that if the inter-station line connected to this line can transfer the loads of other lines of this station through the reverse busbar connection of this line at the same time.

[0061] The following further illustrates this solution with an actual case.

[0062] Taking a certain substation in the core area of Weihai City as an example, collecting basic data, sorting out the line connection situation, and comparing the load transferable rates of the substation in two special cases of the outage of a certain section of the 10 kV busbar or the complete outage of the substation before and after adopting the load transfer solution in this article, which proves the rationality and effectiveness of the solution.

[0063] (1) Basic situation of the substation

[0064] The capacity of Substation A at 35 kV is 40 MVA (20 + 20 MVA). There are 15 10 kV switchgear cubicles in the station (0 in the civil engineering location). Currently, 12 are in use. Among them, there are 11 public lines (8 have inter-station connection lines, and 3 are connection lines within the station), and 1 user dedicated line. At the typical load moment, the total 10 kV load of Substation A is 22 MW, and the substation load rate is 55%. Among them, the load of the 10 kV Section I busbar is 12 MW, and the load of the 10 kV Section II busbar is 10 MW. The basic situation is shown in the following table.

[0065] Table 1: Basic situation table of the load of Substation A at 35 kV and the 10 kV lines

[0066]

[0067] (2) Load transfer situation when the 10 kV busbar of the substation experiences an N-1 event

[0068] 1) Load transfer situation without using the load transfer method of this application

[0069] ① When the 10 kV section I busbar of Substation A fails or is taken out of service for maintenance, a load of approximately 2.2 MW on the common line Jiawu Line cannot be transferred out.

[0070] Table 2: Table of the N-1 situation of the 35 kV section I busbar of Substation A

[0071] Serial number Line Current (A) Outgoing line Load rate of outgoing line Current to be limited (A) Reason for limitation 1 Line A-1 70.5 Line A-9 40％ - - 2 Line A-2 464 Line B-1 74％ - - 3 Line A-3 1099 Line C-3 51％ - - 4 Line A-4 233 Line B-2 66％ - - 5 Line A-5 126.8 None - 126.8 Only bus tie 6 Line A-6 921 Line A-7 45％ - -

[0072] ② When the 10 kV section II busbar of Substation A fails or is taken out of service for maintenance, a load of approximately 0.7 MW on the common line Jia Ba Line cannot be transferred out.

[0073] Table 3: Table of the N-1 situation of the 35 kV section II busbar of Substation A

[0074]

[0075] 2) Load transfer situation using the load transfer method of this application

[0076] ① When the 10 kV section I busbar of Substation A fails or is taken out of service for maintenance, all loads can be transferred out.

[0077] Table 4: Table of the N-1 situation of the 35 kV section I busbar of Substation A

[0078] Serial number Line Current (A) Outgoing line Load rate of outgoing line Current limited (A) Reason for limitation 1 Line A-1 70.5 Line A-9 40％ - - 2 Line A-2 464 Line B-1 74％ - - 3 Line A-3 1099 Line C-3 51％ - - 4 Line A-4 233 Line B-2 66％ - - 5 Line A-5 126.8 Line B-2 (feeding Line A-5 via Line A-4) 97％ - - 6 Line A-6 921 Line A-7 45％ - -

[0079] ② When the 10 kV section II busbar of Substation A fails or is taken out of service for maintenance, a load of approximately 0.7 MW on the Jia Ba Line cannot be transferred out.

[0080] Table 5: Table of the N-1 situation of the 35 kV section II busbar of Substation A

[0081]

[0082] (3) Load transfer situation when the substation is completely out of service

[0083] 1) Load transfer situation without using the load transfer method of this application

[0084] When Substation A is completely out of service, loads on 4 circuits, namely the common lines Jia Yi Line, Jia Wu Line, Jia Liu Line, and Jia Ba Line, approximately 5.7 MW, and the dedicated line Jia Twelve Line, 1.3 MW, cannot be transferred out. The load transfer rate of the common lines is 71.78%, and all loads on the dedicated line are lost.

[0085] Table 6: Table of the full outage and full transfer of Substation A at 35 kV

[0086]

[0087] 2) Load transfer situation using the load transfer method of this application

[0088] When Substation A is completely out of service, about 1.2 MW of the load on 1 circuit of the common line Jia-1 cannot be transferred out. The load transfer rate of the common line is 94.06%, and the load of the dedicated line can be completely transferred out.

[0089] Table 7: Table of the full outage and full transfer of Substation A at 35 kV

[0090]

[0091] According to the above comparison, after adopting the load transfer method of this application, when a certain section of the 10 kV busbar in Substation A fails or is taken out of service for maintenance, the number of lines that do not meet the busbar N-1 requirement drops from 2 circuits to 1 circuit, and the load transfer rate of the common line rises from 85.64% to 96.53%; when the substation is completely out of service, the number of common lines that do not meet the full outage and full transfer requirement of the substation drops from 4 circuits to 1 circuit, and the load transfer rate of the common line rises from 71.78% to 94.06%, and the load of the dedicated line is improved from complete loss to complete transfer out.

[0092] Not meeting the busbar / line N-1: At the moment of the maximum load, when the 10 kV busbar / line is at N-1, after the backup power supply automatic switching device or FA operates, if the load of a certain line cannot be completely transferred to other busbars / lines through the tie line (without overload), then it is said that this line does not meet the busbar / line N-1 (here, the busbar N-1 refers to the withdrawal of a certain section of the busbar from operation).

[0093] Load transfer rate at 10 kV busbar N-1: At 10 kV busbar N-1, the proportion of the load that can be transferred in the total load of the 10 kV lines (since most of the user dedicated lines have no connection, the load transfer rate of the 10 kV busbar N-1 in this article only counts the load transfer rate of the common lines).

[0094] Not meeting the full outage and full transfer of the substation: When the substation is completely out of service, if the load of a certain line cannot be completely transferred to other substations through the tie line, then it is said that this line does not meet the full outage and full transfer of the substation.

[0095] Load transfer rate when the substation is completely out of service: When the substation is completely out of service, the proportion of the load that can be transferred on the 10 kV lines in the total load of the 10 kV lines.

[0096] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A load transfer method for a substation when a section of 10kV busbar is out of power or completely shut down, characterized in that: The steps include: S100, when the substation has 10 kV busbar N-1, based on the line connection situation, the substation lines are classified and the corresponding load transfer strategy and transferable load calculation method are given; S110. Lines with inter-station connections or inter-station connections with different mothers: If the load cannot be fully transferred out through inter-station connections or inter-station connections with different mothers, the load that can be transferred is calculated based on how much can be transferred; S120, only lines with the same mother line in the same station: if the same mother line in contact with this line has a different station contact or a same station different mother contact line, the load of this line will be indirectly transferred as much as possible through the same mother contact line; S130, single radial or single line circuit: total loss of load; S200, when all substations are shut down, based on the line connection situation, the substation lines are classified and corresponding load transfer strategies and transferable load calculation methods are given; S210, there is a line with inter-station connection: if the load cannot be fully transferred out through the inter-station connection line, the load that can be transferred is calculated according to how much can be transferred; S220, only lines with same-station contact: if there is a different-station contact line with the same-station line connected with this line, the load of this line will be indirectly transferred out through the same-station contact line; if there is a different-station contact line with the same busbar as this line, the load of this line will be indirectly transferred through the reverse busbar; S230, single radial or single line: If there is an inter-station interconnection line on the same bus as this line, the load of this line will be indirectly transferred through the reverse bus.

2. A load transfer method for a substation when a certain section of 10kV busbar is out of power or completely shut down according to claim 1, characterized in that: The transformer is a double-winding transformer and the low-voltage side is 10 kV for a 110 kV substation, 66 kV substation or 35 kV substation; the main connection diagram of the substation adopts single-busbar sectional connection, double-busbar connection or double-busbar sectional connection.

3. A load transfer method for a substation when a certain section of 10kV busbar is out of power or completely shut down according to claim 1, characterized in that: The substation 10kV busbar N-1 refers to a section of the busbar being out of operation due to a fault or maintenance, that is, a section of the 10kV busbar in the substation is out of power; a complete shutdown of the substation means that the high-voltage side power line or main transformer of the substation is completely shut down, and the 10kV busbar can be operated.

4. A load transfer method for a substation when a certain section of 10kV busbar is out of power or completely shut down according to claim 3, characterized in that: The calculation formula for the sum of the transferable load L1 in S110 is: ， Where L i It indicates the load directly transferred out through inter-station ties or inter-station but different mother ties, and n1 indicates the number of lines that can transfer all or part of the load through inter-station ties or inter-station but different mother ties; The calculation formula for the sum of the transferable load L2 in S120 is: ， Where L j It represents the load that can be transferred indirectly through the same mother interconnection line, and n2 represents the number of lines that can transfer all or part of the load through the same mother interconnection line.

5. A load transfer method for a substation when a certain section of 10kV busbar is out of power or completely shut down according to claim 4, characterized in that: Calculate all transferable loads L at 10 kV busbar N-1 of the substation Z1 =L1+L2, and calculate the ratio of all transferable loads to the total load of the 10kV bus feeder line of this section, and get the load transfer rate T for 10kV bus N-1 l1 =(L Z1 / L 01 )×100%, where L 01 It represents the sum of the loads of the 10kV bus feeder lines.

6. A load transfer method for a substation when a certain section of 10kV busbar is out of power or completely shut down according to claim 3, characterized in that: The calculation formula for the sum of the transferable load L3 in S210 is: ， Where L k It indicates the load directly transferred out through the inter-station contact line, and n3 indicates the number of lines that can transfer all or part of the load through the inter-station contact line; The calculation formula for the sum of the transferable load L4 in S220 is: ， Where L r represents the load indirectly transferred through the same-station interconnection line, n4 represents the number of lines that can transfer all or part of the load through the same-station interconnection line, L s It indicates the load that can be transferred indirectly through the line with the same busbar and the busbar, and n5 indicates the number of lines that can transfer all or part of the load through the line with the same busbar and the busbar; The calculation formula for the sum of the transferable load L5 in S230 is: ， Where L h It indicates the load of a single radial or single line circuit indirectly transferred out through the line with the same busbar and the busbar, and n6 indicates the number of single radial or single line circuits that can transfer all or part of the load through the line with the same busbar and the busbar.

7. A load transfer method for a substation when a certain section of 10kV busbar is out of power or completely shut down according to claim 6, characterized in that: Calculate all transferable loads L when the substation is completely shut down Z2 =L3+L4+L5, and calculate the ratio of all transferable loads to the total load of the 10kV line fed out of the substation, and obtain the load transfer rate T when the substation is completely shut down l2 =(L Z2 / L 02 )×100%, where L 02 It represents the sum of the loads of the 10kV lines fed by the substation.

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