Coordinated planning method for main transformer capacity and outgoing line interval of 220kV substation

Abstract

The invention discloses a 220kV substation main transformer capacity and outgoing line interval coordinated planning method, which comprises the following steps: acquiring working data information of a target power system, and sorting and analyzing the working data information; determining a target frame structure of the 110kV and 35kV power grids; selecting a 110kV and 35kV power grid load ratio; selecting a capacity-load ratio of the target area according to the load increasing speed; calculating the number of main transformers of the 110kV power grid and the 35kV power grid, and further calculating the outgoing line interval requirement of the 110kV power grid and the 35kV power grid; according to the load requirements and development potentials of different areas, the configuration of the main transformer capacity and the outgoing line interval is dynamically adjusted, and the outgoing line interval requirements under different load ratio conditions are optimized in combination with the capacity-load ratio of the target area. According to the method, the defects of a traditional method when load change is rapid or development space pre-judgment is insufficient are overcome, the economical efficiency, reliability and flexibility of power grid planning are improved, and the stability and coping capacity of a power grid are effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of power distribution network, and in particular relates to a method for coordinating planning of main transformer capacity and outgoing line interval of a 220kV substation. Background Art

[0002] The existing coordinated planning of substation main transformer capacity and outgoing line interval is based on certain engineering experience and grid operation requirements. According to the results of load forecast analysis, the main transformer capacity of the substation is determined by considering the matching of maximum load, load margin and load factor with transformer capacity. Then, the number and interval of outgoing lines are determined according to the load distribution of the substation and the needs of the power supply area. The existing method has the following disadvantages:

[0003] (1) Increased risk of short-circuit current:

[0004] If the capacity of the main transformer and the line spacing are not coordinated, a large short-circuit current may occur in the substation, especially when a system failure occurs. For example, when the substation capacity is too large or there are too many lines, the short-circuit current increases, which will cause a greater impact on electrical equipment and increase the action frequency of protection devices, thus affecting the safety of the power grid.

[0005] Excessive short-circuit current will increase the risk of damage to electrical equipment, which may cause damage to equipment such as transformers, circuit breakers, and busbars, and even affect the grid's ability to provide continuous power.

[0006] (2) System stability is impaired:

[0007] If the capacity of the main transformer and the line spacing are not designed properly, it may lead to uneven load distribution, making it difficult for the power grid to recover quickly when a fault occurs, which can easily cause local power outages and affect the stable operation of the power grid.

[0008] If the capacity of a substation is too large, the failure of a single transformer or a single outgoing line may cause a large-scale power outage, affecting the power system's ability to recover and posing a threat to the overall stability of the grid.

[0009] (3) Poor economic efficiency:

[0010] Too large or too small transformer capacity will affect economic efficiency. If the capacity is too large, it may cause idle equipment and unnecessary investment; if the capacity is too small, it may lead to insufficient load access, unable to meet power demand, and affect the reliability of power supply.

[0011] Too many outgoing line intervals will increase the investment cost and maintenance difficulty of the distribution line; too few outgoing line intervals may cause a single outgoing line to be overloaded, affecting the redundancy and fault recovery capabilities of the system.

[0012] (4) Adaptability of load and power grid:

[0013] The selection of substation capacity is often based on current load demand, but the uncertainty of future load changes may lead to too small or too large design capacity, which in turn affects the adaptability of the power grid. If the load demand of the power grid grows too fast, it may cause the substation to be overloaded; while if the load grows slowly or stagnates, the substation equipment may be in a low-load state for a long time, resulting in a waste of resources.

[0014] (5) Fault scalability issues:

[0015] Too few outgoing line intervals may result in a greater impact of the substation on the entire power supply area when a fault occurs; too many outgoing line intervals increase the difficulty of protection during power grid faults, which may cause excessive overcurrent and affect the safety of equipment. Summary of the invention

[0016] In view of this, the purpose of the present invention is to provide a method for coordinated planning of the capacity of the main transformer and the outgoing line interval of a 220kV substation, so as to avoid the shortcomings of the traditional method when the load changes rapidly or the development space is insufficiently predicted.

[0017] In a first aspect, an embodiment of the present invention provides a method for coordinating the capacity and outgoing line interval of a 220 kV substation main transformer, comprising:

[0018] Obtain the working data information of the target power system and organize and analyze it;

[0019] Based on the obtained working data information, determine the target framework structure of 110kV and 35kV power grids;

[0020] Based on the determined target framework structure, the load ratio of 110kV and 35kV power grids is selected;

[0021] Select the target area load ratio based on the load growth rate;

[0022] Based on the working data information and target framework structure, the number of main transformers of 110kV and 35kV power grids is calculated, and then the outgoing line spacing requirements of 110kV and 35kV power grids are calculated;

[0023] According to the load demand and development potential of different regions, the configuration of main transformer capacity and outgoing line interval is dynamically adjusted, and combined with the capacity-load ratio of the target area, the outgoing line interval requirements under different load ratio conditions are optimized.

[0024] Preferably, the working data information includes all data information of the 220kV substation, and the capacity of the main transformer in the 220kV substation is set to 240MVA, and the number of main transformers in the 220kV substation does not exceed 3;

[0025] The main transformer overload factor is set to 1.3, the maximum load rate of the main transformer of the 220kV substation is 87%, and the maximum power supply capacity of a single main transformer is 209MW.

[0026] Preferably, the target grid of the 110kV power grid adopts a chain-type π-connected 3-3-3-3 structure, and the capacity of a single 110kV main transformer is 50MVA;

[0027] The target framework of the 35kV power grid adopts a double-sided power supply radial structure, and the capacity of a single 110kV main transformer is 20MVA.

[0028] Preferably, the capacity-load ratio calculation formula is:

[0029] R SP =S ∑i / P max

[0030] In the formula, R SP is the capacity load ratio of a certain voltage level; S ∑i is the capacity of the main transformer of the substation at this voltage level; P max This is the annual maximum predicted load for this voltage level.

[0031] Preferably, the calculation formula for the number of main transformers is as follows:

[0032] n 110 =S ∑110 / S 110

[0033] n 35 =S ∑35 / S 35

[0034] Where n 110 and n 35 The number of 110kV and 35kV main transformers respectively; S ∑110 and S ∑35 The main transformer capacity and MVA of 110kV and 35kV substations respectively; S 110 and S 35 The main transformer capacity of a single 110kV and 35kV substation in MVA respectively;

[0035] The calculation formula for the required spacing of 110kV power grid outgoing lines is:

[0036]

[0037] In the formula, k 110 It is the 110kV outgoing line spacing requirement.

[0038] The calculation formula for the required spacing of 35kV power grid outgoing lines is:

[0039]

[0040] In the formula, k 35 It is the 35kV outgoing line spacing requirement.

[0041] The embodiments of the present invention bring the following beneficial effects:

[0042] Compared with the traditional substation main transformer capacity and outgoing line interval planning method, the planning method proposed in the present invention has significant advantages in flexibility, accuracy and adaptability. By introducing multi-factor analysis such as regional capacity-load ratio and load ratio, the configuration of the main transformer capacity and outgoing line interval can be dynamically adjusted according to the load demand and development potential of different regions. For example, when the regional capacity load is relatively small, the maximum load rate of the main transformer is large, which can reduce the demand for medium and low voltage outgoing line intervals, while more outgoing line intervals are required when the load is large.

[0043] The requirements for outgoing line spacing under different load ratios are optimized so that the power grid design can meet the current load demand while reserving sufficient redundant space for future load growth. By comprehensively considering the growth of power demand and regional development potential, the present invention avoids the shortcomings of traditional methods when the load changes rapidly or the development space is insufficiently predicted, improves the economy, reliability and flexibility of power grid planning, and effectively enhances the stability and response capabilities of the power grid.

[0044] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic flow chart of a method for coordinating the capacity and outgoing line interval of a 220kV substation main transformer provided by an embodiment of the present invention;

[0047] Figure 2 A schematic diagram of a 110kV chain-type π-connection "3-3-3-3" structure provided in an embodiment of the present invention;

[0048] Figure 3 A schematic diagram of a single 110kV chain-type π-connected structure provided by an embodiment of the present invention;

[0049] Figure 4 A schematic diagram of a 35kV double-side power supply radiation structure provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] To facilitate understanding of this embodiment, firstly, a method for coordinated planning of the capacity and outgoing line interval of a 220kV substation main transformer disclosed in Embodiment 1 of the present invention is described in detail. Figure 1 As shown, the following steps are included:

[0052] S1. Obtain the working data information of the target power system and organize and analyze it;

[0053] The working data information includes all data information of the 220kV substation, and the capacity of the main transformer in the 220kV substation is set to 240MVA, and the number of main transformers in the 220kV substation does not exceed 3;

[0054] The main transformer overload factor is set to 1.3, and the maximum load rate of the main transformer of the 220kV substation is 87%, which meets the N-1 requirement of 3 main transformers. The maximum power supply capacity of a single main transformer is 209MW.

[0055] S2. Determine the target framework structure of 110kV and 35kV power grids based on the obtained working data information;

[0056] Among them, Figure 2 As shown in the figure, the target grid of 110kV power grid adopts the chain-type π-connected "3-3-3-3" structure, that is, three 110kV public substations are chain-connected on both sides, and six lines supply nine 50MVA main transformers. Figure 3 The single-group double-side power chain structure shown has two lines supplying three 50MVA main transformers, and the capacity of a single 110kV main transformer is 50MVA;

[0057] like Figure 4 As shown, the target framework of the 35kV power grid adopts a double-sided power supply radial structure, that is, the double-sided power supply directly supplies a 35kV public substation, 3 lines supply 3 20MVA main transformers and the capacity of a single 110kV main transformer is 20MVA.

[0058] S3. Based on the determined target framework structure, select the load ratio of 110kV and 35kV power grids;

[0059] Among them, a single 220kV main transformer has a capacity of 240MVA and a load of 209MW; the maximum load on the 35kV side is 83.6MW, which meets the 120MVAN-1 requirement for the half capacity of the low-voltage side of the 220kV main transformer. The details are shown in Table 1.

[0060] Table 1 Load distribution on the medium and low voltage sides of 220kV main transformer

[0061]

[0062] S4. Select the target area load ratio according to the load growth rate;

[0063] The calculation formula of capacity ratio is:

[0064] R SP =S ∑i / P max

[0065] In the formula, R SP is the capacity ratio of a certain voltage level (MVA / kW); S ∑i is the sum of the main transformer capacities of the substation at this voltage level, in MVA; P max It is the annual maximum predicted or current load for this voltage level, in MW.

[0066] S5. Based on the working data information and the target framework structure, the number of main transformers of the 110kV and 35kV power grids is calculated, and then the outgoing line interval requirements of the 110kV and 35kV power grids are calculated;

[0067] The calculation formula for the number of main transformers is as follows:

[0068] n 110 =S ∑110 / S 110

[0069] n 35 =S ∑35 / S 35

[0070] Where n 110 and n 35 The number of 110kV and 35kV main transformers, in units; S ∑110 and S ∑35 The sum of the main transformer capacities of 110kV and 35kV substations, in MVA; S 110 and S 35 The main transformer capacity of a single 110kV and 35kV substation, in MVA, is 50MVA and 20MVA respectively.

[0071] When the calculated value of the number of main transformers is a decimal and is rounded to an integer, the integer is increased by 1 in accordance with the principle of improving the utilization efficiency of 220kV main transformers. When the number of 110kV main transformers is used to calculate the interval requirements, the general principles of 6 lines and 9 transformers (3 groups of chain), 4 lines and 6 transformers (2 groups of chain), and 2 lines and 3 transformers (1 group of chain) are followed.

[0072] When the number of main transformers is 7 or 8, it is necessary to add one line on the basis of 4 lines and 6 transformers to supply power to another 1 or 2 transformers; when the number of main transformers is 4 or 5, it is necessary to add one line on the basis of 2 lines and 3 transformers to supply power to another 1 or 2 transformers.

[0073] The calculation formula for the required spacing of 110kV power grid outgoing lines is:

[0074]

[0075] In the formula, k 110 It is the 110kV outgoing line spacing requirement.

[0076] The calculation formula for the required spacing of 35kV power grid outgoing lines is:

[0077]

[0078] In the formula, k 35 It is the 35kV outgoing line spacing requirement.

[0079] S6. Dynamically adjust the configuration of main transformer capacity and outgoing line spacing according to the load demand and development potential of different regions, and optimize the outgoing line spacing requirements under different load ratio conditions in combination with the capacity-load ratio of the target area, so that the power grid design can meet the current load demand.

[0080] In this embodiment, the value of 110(35)kV capacity-load ratio is related to the growth rate of regional distribution network load, and should be generally controlled between 1.5 and 2.0. Three levels of 1.6, 1.8, and 2.0 are selected, and a level of 2.2 is added for relevant calculations.

[0081] Furthermore, when the distribution network load is in a slow growth stage, the capacity-load ratio is selected as 1.6, that is, the maximum load rate of the regional main transformer is 62.5%. The requirements for the low-voltage outgoing line interval of the 220kV main transformer are shown in Table 2.

[0082] Table 2 Requirements for the spacing between medium and low voltage outgoing lines of 220kV main transformer when the capacity load ratio is 1.6

[0083]

[0084] When the capacity-load ratio is 1.6, the 110kV outgoing line intervals of a single 220kV main transformer are 3 to 4, the 35kV outgoing line intervals are 7 to 2, and the total outgoing line intervals are 6 to 10.

[0085] Furthermore, when the distribution network load is in a medium growth stage, the capacity-load ratio is selected as 1.8, that is, the maximum load rate of the regional main transformer is 55.6%. The requirements for the medium and low voltage outgoing line intervals of the 220kV main transformer are shown in Table 3.

[0086] Table 3 Requirements for the spacing between medium and low voltage outgoing lines of 220kV main transformer when the capacity load ratio is 1.8

[0087]

[0088] When the capacity-load ratio is 1.8, the 110kV outgoing line intervals of a single 220kV main transformer are 3 to 5, the 35kV outgoing line intervals are 8 to 2, and the total outgoing line intervals are 7 to 11.

[0089] Furthermore, when the distribution network load is in a rapid growth stage, the capacity-load ratio is selected as 2.0, that is, the maximum load rate of the regional main transformer is 50%. The requirements for the medium and low voltage outgoing line intervals of the 220kV main transformer are shown in Table 4.

[0090] Table 4 Requirements for the spacing between medium and low voltage outgoing lines of 220kV main transformer when the capacity load ratio is 2.0

[0091]

[0092] When the capacity-load ratio is 2.0, the 110kV outgoing line intervals of a single 220kV main transformer are 3 to 5, the 35kV outgoing line intervals are 9 to 3, and the total outgoing line intervals are 8 to 12.

[0093] Furthermore, when the load of the distribution network is in a faster growth stage (load growth rate is greater than 12%), the capacity-load ratio is selected as 2.2, that is, the maximum load rate of the regional main transformer is 45.5%. The requirements for the low-voltage outgoing line spacing of the 220kV main transformer are shown in Table 5.

[0094] Table 5 Requirements for the spacing between medium and low voltage outgoing lines of 220kV main transformer when the capacity load ratio is 2.2

[0095]

[0096] When the capacity-load ratio is 2.2, the 110kV outgoing line intervals of a single 220kV main transformer are 4 to 6, the 35kV outgoing line intervals are 10 to 3, and the total outgoing line intervals are 9 to 14.

[0097] Through the above configuration of dynamically adjusting the main transformer capacity and the outgoing line interval, it can be seen that: when the medium and low voltage load ratios of the 220kV main transformer are the same, the smaller the regional capacity-load ratio, the greater the maximum load rate of the main transformer, and the less the medium and low voltage outgoing line interval requirements; conversely, the more medium and low voltage outgoing line interval requirements.

[0098] When the regional capacity-load ratio is the same, the greater the medium- and low-voltage load ratio of the 220kV main transformer, the greater the 110kV load, the smaller the total demand for medium- and low-voltage line intervals, and the greater the demand for 110kV intervals; conversely, the greater the total demand for medium- and low-voltage line intervals, the smaller the demand for 110kV line intervals.

[0099] Example 2, taking the current Limin Road as an example,

[0100] The capacity of the 220kV main transformer is 3×150MVA, and the voltage level is 220 / 35 / 10kV. There are 24 total bays on the 35kV side, 23 outgoing lines at present, and the total maximum load is 208.4MW, of which the public station load is 173.1MW and the user station load is 35.3MW. There are 18 total bays on the 10kV side, which are currently full, and the total maximum load is 37.4MW.

[0101] Considering the need for 35kV step-up reconstruction, the capacity of Limin Road Station is selected as 3×240MVA during reconstruction, and the voltage sequence is 220 / 110 / 35kV. In the long term, the 35kV public station load and the 10kV distribution transformer load are both supplied by the 110kV public station. The medium and low voltage load ratio is 6:1, which is between 8:2 and 9:1. Referring to Table 4, 5 intervals are selected on the 110kV side, and 5 or 3 intervals are selected on the 35kV side.

[0102] After the reconstruction of Limin Road Station, the 35kV side mainly supplies power to user stations. The main transformer capacity of a single user is generally less than 20MVA, so the 35kV side intervals are selected as the larger value of 5, and 1 to 2 intervals can be appropriately increased according to the needs of optimizing the 35kV grid structure.

[0103] Example 3, taking Chengnan Company as an example, as the power load increases, the load ratio of 110kV and 35kV power grids will gradually increase, and four gears of 6:4, 7:3, 8:2, and 9:1 are selected to carry out relevant calculations.

[0104] In 2022, the per capita comprehensive electricity consumption will be 4144 kWh / person, and the per capita living electricity consumption will be 1004 kWh / person. This is a city with an upper-middle level of electricity consumption and there is still much room for development. The load-to-capacity ratio will be considered based on the upper limit of 2.0 to retain sufficient power supply capacity.

[0105] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0106] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for coordinating the capacity and outgoing line interval of a 220kV substation main transformer, characterized in that: Include the following: Obtain the working data information of the target power system and organize and analyze it; Based on the obtained working data information, determine the target framework structure of 110kV and 35kV power grids; Based on the determined target framework structure, the load ratio of 110kV and 35kV power grids is selected; Select the target area capacity ratio according to the load growth rate; Based on the working data information and target framework structure, the number of main transformers of 110kV and 35kV power grids is calculated, and then the outgoing line spacing requirements of 110kV and 35kV power grids are calculated; According to the load demand and development potential of different regions, the configuration of main transformer capacity and outgoing line interval is dynamically adjusted, and combined with the capacity-load ratio of the target area, the outgoing line interval requirements under different load ratio conditions are optimized.

2. The method for coordinated planning of main transformer capacity and outgoing line interval of a 220kV substation according to claim 1 is characterized in that: The working data information includes all data information of the 220kV substation, and the capacity of the main transformer in the 220kV substation is set to 240MVA, and the number of main transformers in the 220kV substation does not exceed 3; The main transformer overload factor is set to 1.3, the maximum load rate of the main transformer of the 220kV substation is 87%, and the maximum power supply capacity of a single main transformer is 209MW.

3. The method for coordinated planning of main transformer capacity and outgoing line interval of a 220kV substation according to claim 1 is characterized in that: The target grid of the 110kV power grid adopts a chain-type π-connected 3-3-3-3 structure, and the capacity of a single 110kV main transformer is 50MVA; The target framework of the 35kV power grid adopts a double-sided power supply radial structure, and the capacity of a single 110kV main transformer is 20MVA.

4. The method for coordinated planning of main transformer capacity and outgoing line interval of a 220kV substation according to claim 1 is characterized in that: The formula for calculating the capacity load ratio is: R SP =S ∑i / P max In the formula, R SP is the capacity load ratio of a certain voltage level; S ∑i is the capacity of the main transformer of the substation at this voltage level; P max This is the annual maximum predicted load for this voltage level.

5. The method for coordinated planning of main transformer capacity and outgoing line interval of 220kV substation according to claim 1 is characterized in that: The calculation formula for the number of main transformers is as follows: n 110 =S ∑110 / S 110 n 35 =S ∑35 / S 35 Where n 110 and n 35 The number of 110kV and 35kV main transformers respectively; S ∑110 and S ∑35 The main transformer capacity and MVA of 110kV and 35kV substations respectively; S 110 and S 35 The main transformer capacity of a single 110kV and 35kV substation in MVA respectively; The calculation formula for the required spacing of 110kV power grid outgoing lines is: In the formula, k 110 The 110kV outgoing line spacing requirement; The calculation formula for the required spacing of 35kV power grid outgoing lines is: In the formula, k 35 It is the 35kV outgoing line spacing requirement.

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