Method and system for determining transmission potential of 220kV lines

Abstract

The present invention discloses a method for determining the transmission potential of a 220kV line, comprising obtaining data information of a target area power grid; calculating basic load information of a key line of the target area power grid; calculating the flow transfer ratio of the key line of the target area power grid after an N-1 fault; calculating the flow data of the bayonet line of the target area power grid; calculating the flow sensitivity of the key line after a set load increase; calculating the load increase ratio of the target area power grid; calculating the maximum power supply capacity of the target area power grid and the transmission capacity that can be increased by the key line; and completing the transmission potential determination of the 220kV line of the target area power grid based on the maximum power supply capacity and the transmission capacity that can be increased by the key line. The present invention also discloses a system for implementing the 220kV line transmission potential determination method. The present invention can not only realize the transmission potential determination of the 220kV line, but also has higher reliability, better accuracy, and higher efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of electrical automation, and in particular relates to a method and system for determining the transmission potential of a 220kV line. Background Art

[0002] With the development of economy and technology and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and life, bringing endless convenience to people's production and life. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] As environmental issues become increasingly severe, more and more renewable energy generation systems are being integrated into the power system. Simultaneously, power system user loads are increasing, their complexity is growing, and power system flows are fluctuating more frequently, requiring ever-increasing transmission capacity during peak demand periods. However, power system planning and construction cannot be accomplished overnight, so exploring the transmission potential of existing power systems is crucial.

[0004] Currently, the evaluation method for the transmission potential of 220kV power lines in power systems still relies on manual evaluation. This involves power system personnel manually determining and evaluating the transmission potential of 220kV power lines using simulation systems. However, this method is not only time-consuming and labor-intensive, but also relatively subjective, and cannot meet the requirements for safe and stable operation of power systems. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a method for determining the transmission potential of a 220kV line with high reliability and good accuracy.

[0006] A second object of the present invention is to provide a system for implementing the method for determining the transmission potential of a 220kV line.

[0007] The method for determining the transmission potential of a 220 kV line provided by the present invention comprises the following steps:

[0008] S1. Obtain data information of the target area power grid;

[0009] S2. Calculate the basic load information of the key lines of the target area power grid according to the data information obtained in step S1;

[0010] S3. Based on the data information obtained in step S1, calculate the flow transfer ratio of the key lines of the target area power grid after the N-1 fault;

[0011] S4. Calculate the target area grid's bayonet line flow data based on the flow transfer ratio obtained in step S3;

[0012] S5. According to the flow data obtained in step S4, based on the current power supply mode and load level of the target area power grid, calculate the flow sensitivity of the key lines after the set load growth;

[0013] S6. Calculate the load growth ratio of the target area power grid according to the power flow sensitivity obtained in step S5;

[0014] S7. Based on the load growth ratio obtained in step S6, calculate the maximum power supply capacity of the target area power grid and the transmission capacity of key lines that can be increased;

[0015] S8. Based on the maximum power supply capacity obtained in step S7 and the increased transmission capacity of the key lines, the transmission potential of the 220 kV lines of the target area power grid is determined.

[0016] Step S2, based on the data information obtained in step S1, calculates the basic load information of the key lines of the target area power grid, specifically including the following steps:

[0017] The key line load rate α in the target area power grid is calculated using the following formula:

[0018]

[0019] Where P line Deliver power to key lines; P N,line is the sustained maximum transmission capacity of the critical line, and U is the line voltage of the critical line, I is the actual safety control current of the critical line, is the power factor;

[0020] The following formula is used to determine the actual safety control current I of the critical circuit:

[0021] I=min{I T ,I D ,I K ,I J ,I L}

[0022] Where I T Safely control the current for the current transformer in the substation; I D To safely control the current for the switch in the substation; I K Safely control current for switches in substations; I J Safely control current for spaced conductors in substations; I L Rated safety control current for the critical circuit itself.

[0023] Step S3, based on the data information obtained in step S1, calculates the power flow transfer ratio of the key line of the target area power grid after the N-1 fault, and specifically includes the following steps:

[0024] The following formula is used to calculate the power flow transfer ratio of the key lines of the target area power grid after N-1 faults:

[0025]

[0026] Where β i,j is the power flow transfer ratio of the i-th key line to the j-th key line after N-1 failure; P j ' ,line is the power flow of the jth key line after the i-th key line fails at N-1; P j,line is the power flow of the jth key line before the N-1 failure of the i-th key line; P i,line is the power flow of the i-th critical line before N-1 failure.

[0027] The step S4 of calculating the power flow data of the checkpoint line of the target area power grid based on the power flow transfer ratio obtained in step S3 specifically includes the following steps:

[0028] The power flow of the target area power grid's checkpoint line is calculated using the following formula:

[0029] β i,j ·P i,line +P j,line =P j,line,N

[0030] Where P j,line,N is the continuous maximum transmission capacity of the j-th checkpoint line; the checkpoint line is defined as a critical line where the transmission power of the 220kV line reaches the maximum transmission capacity when N-1 faults occur in other lines.

[0031] Step S5, based on the power flow data obtained in step S4 and the current power supply mode and load level of the target area power grid, calculates the power flow sensitivity of the key line after the load increase, specifically including the following steps:

[0032] Based on the current power supply mode and load level of the target area power grid, the load of each substation is set to increase simultaneously according to the set growth rate;

[0033] The power flow sensitivity of the key lines after the assumed load increase is calculated using the following formula:

[0034]

[0035] Where δ iP′ is the power flow sensitivity of the i-th key line in the target area power grid after the set load increase; i,line,up is the power of the i-th key line of the target area power grid after the set load increase; P i,line,up is the power of the i-th key line in the target area power grid before the set load increase.

[0036] Calculating the load growth ratio of the target area power grid based on the power flow sensitivity obtained in step S5 in step S6 specifically includes the following steps:

[0037] The following formula is used to calculate the load growth ratio of the target area power grid when the i-th key line is used as the checkpoint line:

[0038]

[0039] Where η i " is the load growth ratio of the target area power grid when the i-th key line is used as the checkpoint line; P i,line,N is the continuous limit transmission capacity of the i-th key line;

[0040] At the same time, if the load growth is nonlinear, then for η i ", the perturbation method is used for further optimization, and the load growth ratio η' is corrected i is η′ i =η i ”+Δη i , Δη i is the load growth ratio step value adopted by the perturbation method;

[0041] Finally, if the load growth ratio is linear, the load growth ratio η of the target area power grid is i is η i =η i "; If the load growth ratio is nonlinear, the load growth ratio of the target area power grid is η i is η i =η i '.

[0042] Step S7, based on the load growth ratio obtained in step S6, calculates the maximum power supply capacity of the target area power grid and the increased power transmission capacity of the key lines, which specifically includes the following steps:

[0043] The maximum power supply capacity of the target area power grid is calculated using the following formula:

[0044] P load =P 0,load +ΔP i,load

[0045] Where P loadis the maximum power supply capacity of the target area power grid; P 0,load is the initial power supply capacity of the target area power grid; ΔP i,load is the increased load when the i-th key line of the target area power grid is used as a checkpoint line, and ΔP i,load =η i ·P 0,load ;

[0046] The following formula is used to calculate the increased transmission capacity of the i-th key line:

[0047]

[0048] Where ΔP i,line I is the increased transmission capacity of the i-th key line; Line Rated safety control current for the critical circuit itself.

[0049] Step S8, based on the maximum power supply capacity obtained in step S7 and the increased power transmission capacity of the key lines, completes the determination of the power transmission potential of the 220 kV lines of the target area power grid, specifically including the following steps:

[0050] The transmission potential index ε of the 220kV line of the target area power grid is calculated as follows:

[0051] Determine the transmission potential index ε:

[0052] The larger the transmission potential index ε is, the greater the transmission potential of the 220 kV line in the target area power grid is, which means that the studied 220 kV line has the conditions to tap the transmission potential.

[0053] The present invention also provides a system for realizing the method for determining the transmission potential of the 220kV line, comprising a data acquisition module, a load calculation module, a transfer calculation module, a flow calculation module, a sensitivity calculation module, a growth calculation module, a capacity calculation module and a potential determination module; the data acquisition module, the load calculation module, the transfer calculation module, the flow calculation module, the sensitivity calculation module, the growth calculation module, the capacity calculation module and the potential determination module are connected in series in sequence; the data acquisition module is used to acquire data information of the target area power grid and upload the data information to the load calculation module; the load calculation module is used to calculate the basic load information of the key lines of the target area power grid according to the received data information, and upload the data information to the transfer calculation module; the transfer calculation module is used to calculate the flow transfer ratio of the key lines of the target area power grid after N-1 fault according to the received data information, and upload the data information to the flow calculation module; the flow calculation module The calculation module is used to calculate the flow data of the checkpoint line of the target area power grid according to the received data information, and upload the data information to the sensitivity calculation module; the sensitivity calculation module is used to calculate the flow sensitivity of the key line after the set load increase based on the current power supply mode and load level of the target area power grid according to the received data information, and upload the data information to the growth calculation module; the growth calculation module is used to calculate the load growth ratio of the target area power grid according to the received data information, and upload the data information to the capacity calculation module; the capacity calculation module is used to calculate the maximum power supply capacity of the target area power grid and the increased transmission capacity of the key line according to the received data information, and upload the data information to the potential judgment module; the potential judgment module is used to complete the transmission potential judgment of the 220kV line of the target area power grid according to the received data information, the maximum power supply capacity and the increased transmission capacity of the key line.

[0054] The method and system for determining the transmission potential of a 220kV line provided by the present invention reduce the process of gradually increasing the iterative calculation of loads during analysis, and quickly calculate the maximum power supply capacity of the area under the constraints of the key line checkpoint by combining the power flow transfer ratio and the power flow sensitivity of the key line. Therefore, the present invention can not only realize the transmission potential determination of the 220kV line, but also has higher reliability, better accuracy and higher efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the process of the present invention.

[0056] Figure 2 This is a schematic diagram of the power flow in a certain area under normal operation of the power grid in the target year of the embodiment of the method of the present invention.

[0057] Figure 3 This is a schematic diagram of the power flow of a regional power grid when the load is set to increase in the target year of the method embodiment of the present invention.

[0058] Figure 4 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0059] like Figure 1 The method flow diagram of the present invention is shown as follows: The method for determining the transmission potential of a 220kV line disclosed in the present invention comprises the following steps:

[0060] S1. Obtain data information of the target area power grid;

[0061] S2. Calculate the basic load information of the key lines of the target area power grid according to the data information obtained in step S1; specifically comprising the following steps:

[0062] The key line load rate α in the target area power grid is calculated using the following formula:

[0063]

[0064] Where P line Deliver power to key lines; P N,line is the sustained maximum transmission capacity of the critical line, and U is the line voltage of the critical line, I is the actual safety control current of the critical line, is the power factor;

[0065] The following formula is used to determine the actual safety control current I of the critical circuit:

[0066] I=min{I T ,I D ,I K ,I J ,I L}

[0067] Where I T Safely control the current for the current transformer in the substation; I D To safely control the current for the switch in the substation; I K Safely control current for switches in substations; I J Safely control current for spaced conductors in substations; I L Rated safety control current for the critical circuit itself;

[0068] S3. According to the data information obtained in step S1, the flow transfer ratio of the key lines of the target regional power grid after the N-1 fault is calculated; specifically comprising the following steps:

[0069] The following formula is used to calculate the power flow transfer ratio of the key lines of the target area power grid after N-1 faults:

[0070]

[0071] Where β i,j is the power flow transfer ratio of the i-th key line to the j-th key line after N-1 failure; P′ j,line is the power flow of the jth key line after the i-th key line fails at N-1; P j,line is the power flow of the jth key line before the N-1 failure of the i-th key line; P i,line is the power flow of the i-th critical line before N-1 failure;

[0072] S4. According to the flow transfer ratio obtained in step S3, the flow data of the target area power grid bayonet line is calculated; specifically comprising the following steps:

[0073] The power flow of the target area power grid's checkpoint line is calculated using the following formula:

[0074] β i,j ·P i,line +P j,line =P j,line,N

[0075] Where P j,line,N is the continuous maximum transmission capacity of the jth checkpoint line; the checkpoint line is defined as the critical line where the transmission power of the 220kV line reaches the maximum transmission capacity when N-1 faults occur in other critical lines;

[0076] Here P j,line,N represents the continuous limit transmission capacity of the jth key line; in step S3, β i,j In the calculation formula of j,line The power flow of the jth critical line after the N-1 failure of the i-th critical line are two different concepts;

[0077] S5. Based on the flow data obtained in step S4, the flow sensitivity of the key lines after the set load increase is calculated based on the current power supply mode and load level of the target area power grid; specifically comprising the following steps:

[0078] Based on the current power supply mode and load level of the target area power grid, the load of each substation is set to increase simultaneously according to the set growth rate;

[0079] The power flow sensitivity of the key lines after the assumed load increase is calculated using the following formula:

[0080]

[0081] Where δ iP′ is the power flow sensitivity of the i-th key line in the target area power grid after the set load increase; i,line,up is the power of the i-th key line of the target area power grid after the set load increase; P i,line,up is the power of the i-th key line of the target area power grid before the set load increase;

[0082] S6. Calculate the load growth ratio of the target area power grid based on the power flow sensitivity obtained in step S5; specifically comprising the following steps:

[0083] The following formula is used to calculate the load growth ratio of the target area power grid when the i-th key line is used as the checkpoint line:

[0084]

[0085] Where η i " is the load growth ratio of the target area power grid when the i-th key line is used as the checkpoint line; P i,line,N is the continuous limit transmission capacity of the i-th key line;

[0086] At the same time, if the load growth is nonlinear, then for η i ", the perturbation method is used for further optimization, and the load growth ratio η' is corrected i is η′ i =η i ”+Δη i , Δη i is the load growth ratio step value adopted by the perturbation method;

[0087] Finally, if the load growth ratio is linear, the load growth ratio η of the target area power grid is i is η i =η i "; If the load growth ratio is nonlinear, the load growth ratio of the target area power grid η i is η i =η i ';

[0088] S7. Calculate the maximum power supply capacity of the target area power grid and the increased transmission capacity of key lines based on the load growth ratio obtained in step S6; specifically, the steps include:

[0089] The maximum power supply capacity of the target area power grid is calculated using the following formula:

[0090] P load =P 0,load +ΔP i,load

[0091] Where P loadis the maximum power supply capacity of the target area power grid; P 0,load is the initial power supply capacity of the target area power grid; ΔP i,load is the increased load when the i-th key line of the target area power grid is used as a checkpoint line, and ΔP i,load =η i ·P 0,load ;

[0092] The following formula is used to calculate the increased transmission capacity of the i-th key line:

[0093]

[0094] Where ΔP i,line I is the increased transmission capacity of the i-th key line; Line Rated safety control current for the critical circuit itself;

[0095] S8. Based on the maximum power supply capacity obtained in step S7 and the increased transmission capacity of the key lines, the transmission potential of the 220kV line of the target area power grid is determined; specifically, the following steps are included:

[0096] The transmission potential index ε of the 220kV line of the target area power grid is calculated as follows:

[0097] Determine the transmission potential index ε:

[0098] The larger the transmission potential index ε is, the greater the transmission potential of the 220 kV line in the target area power grid is, which means that the studied 220 kV line has the conditions to tap the transmission potential.

[0099] The method of the present invention is further described below with reference to an embodiment:

[0100] For example, a regional power grid is expected to be supplied by four 500 kV main transformers and seven 220 kV substations in the target year. The 220 kV substation capacity totals 3,300 MVA, and the 500 kV substation capacity totals 5,000 MVA. The target annual load for the regional power grid is estimated to be 1,925 MW. The load forecast for the seven 220 kV substations is shown in Table 1 below:

[0101] Table 1 Schematic diagram of load forecast for 220 kV substation in a certain area of ​​power grid

[0102]

[0103] According to the regulations for safe and stable operation, the maximum continuous transmission capacity of the ZH~HX line is 579 MW, the maximum continuous transmission capacity of the XC~LH line is 635 MW, and the maximum continuous transmission capacity of the YT~ZH line is 640 MW.

[0104] The power flow diagram of the regional power grid under normal operation in the target year is as follows Figure 2 As shown, the power grid in the studied area is shown as the black dotted box in the figure;

[0105] Power flow analysis reveals that the primary factor limiting the regional grid's power supply capacity is the YT M1-ZH dual-circuit 220 kV line. Under normal operation, when the YT M1-ZH line is in operation at N-1, the power flow on the other circuit is 663 MW, which is insufficient to meet the regional grid's 1,783 MW power demand. The regional grid's safety control current is as follows:

[0106] I=min{I T , I D ,I K ,I J ,I L}=I L =1787A

[0107] The power flow transfer ratio for the YT M1~ZH line N-1 is as follows:

[0108]

[0109] Therefore, when the maximum power supply capacity of the region is met, the line flow is as follows:

[0110]

[0111] The YT M1-ZH line's safety control current was selected based on a 70°C conductor temperature rise. However, during the design phase, the conductor was actually designed for an 80°C temperature rise, so the conductor failed to fully realize its true transmission capacity. According to the design, its maximum continuous transmission capacity is 769 MW. Therefore, the above equation can be rewritten as:

[0112] 0.79·P i,line +P j,line =769

[0113] Considering that the conductor models of the YT M1~ZH double-circuit lines are exactly the same, the P i,line =P j,line =430 MW;

[0114] By increasing the load in this area by 1%, the power flow sensitivity of the YT M1~ZH line can be calculated as follows:

[0115]

[0116] Therefore, the load growth ratio at this time can be calculated as:

[0117]

[0118] According to the above analysis, when the regional power grid load increases by 27% based on the previous year, when the YT M1~ZH line N-1, while considering the actual operation with a certain margin of about 20MW, the other line power flow is 753 MW, which can meet the operation requirements. At this time, the regional power grid power supply capacity is 2100 MW, and the power flow is as follows Figure 3 As shown;

[0119] The evaluation index for tapping the transmission capacity potential of the line is calculated as shown in the following formula. Based on the transmission capacity potential tapping index, it can be seen that for every unit increase in transmission capacity of the YT M1-ZH line, the transmission capacity of the regional power grid can be increased by 2.46 MW, emphasizing the urgent need to tap the transmission capacity of this transmission line. By controlling the safety current of the YT M1-ZH line according to its design temperature, the line's transmission capacity can be maximized:

[0120]

[0121] This patented solution can fully enhance the power supply capacity of the regional power grid while ensuring the safe and stable operation of the power grid, provide a theoretical basis for power grid planners and operators, and then timely adjust the regional power grid structure and operation mode, identify the bottleneck factors that limit the power supply capacity of the power grid and propose corresponding solutions, which has very important engineering practical significance.

[0122] like Figure 4The functional module diagram of the system of the present invention is shown as follows: the system disclosed in the present invention for realizing the method for determining the transmission potential of the 220kV line comprises a data acquisition module, a load calculation module, a transfer calculation module, a flow calculation module, a sensitivity calculation module, a growth calculation module, a capacity calculation module and a potential determination module; the data acquisition module, the load calculation module, the transfer calculation module, the flow calculation module, the sensitivity calculation module, the growth calculation module, the capacity calculation module and the potential determination module are connected in series in sequence; the data acquisition module is used to acquire data information of the target area power grid and upload the data information to the load calculation module; the load calculation module is used to calculate the basic load information of the key lines of the target area power grid based on the received data information, and upload the data information to the transfer calculation module; the transfer calculation module is used to calculate the flow transfer ratio of the key lines of the target area power grid after N-1 faults based on the received data information, and upload the data information to the flow calculation module. Calculation module; the flow calculation module is used to calculate the flow data of the checkpoint line of the target area power grid according to the received data information, and upload the data information to the sensitivity calculation module; the sensitivity calculation module is used to calculate the flow sensitivity of the key line after the set load increase based on the current power supply mode and load level of the target area power grid according to the received data information, and upload the data information to the growth calculation module; the growth calculation module is used to calculate the load growth ratio of the target area power grid according to the received data information, and upload the data information to the capacity calculation module; the capacity calculation module is used to calculate the maximum power supply capacity of the target area power grid and the increased transmission capacity of the key line according to the received data information, and upload the data information to the potential judgment module; the potential judgment module is used to complete the transmission potential judgment of the 220kV line of the target area power grid according to the received data information, the maximum power supply capacity and the increased transmission capacity of the key line.

Claims

1. A method for determining the transmission potential of a 220 kV line, comprising the following steps: S1. Obtain data information of the target area power grid; S2. Calculate the basic load information of the key lines of the target area power grid according to the data information obtained in step S1; S3. Based on the data information obtained in step S1, calculate the flow transfer ratio of the key lines of the target area power grid after the N-1 fault; S4. Calculate the target area grid's bayonet line flow data based on the flow transfer ratio obtained in step S3; S5. According to the flow data obtained in step S4, based on the current power supply mode and load level of the target area power grid, calculate the flow sensitivity of the key lines after the set load growth; S6. Calculate the load growth ratio of the target area power grid according to the power flow sensitivity obtained in step S5; S7. Based on the load growth ratio obtained in step S6, calculate the maximum power supply capacity of the target area power grid and the transmission capacity of key lines that can be increased; S8. Based on the maximum power supply capacity obtained in step S7 and the increased transmission capacity of the key lines, the transmission potential of the 220 kV lines of the target area power grid is determined.

2. The method for determining the transmission potential of a 220 kV line according to claim 1, characterized in that Step S2, based on the data information obtained in step S1, calculates the basic load information of the key lines of the target area power grid, specifically including the following steps: The key line load rate α in the target area power grid is calculated using the following formula: Where P line Deliver power to key lines; P N,line is the sustained maximum transmission capacity of the critical line, and U is the line voltage of the critical line, I is the actual safety control current of the critical line, is the power factor; The following formula is used to determine the actual safety control current I of the critical circuit: I=min{I T ,IN D ,IN K ,IN J ,IN L } Where I T Safely control the current for the current transformer in the substation; I D To safely control the current for the switch in the substation; I K Safely control current for switches in substations; I J Safely control current for spaced conductors in substations; I L Rated safety control current for the critical circuit itself.

3. The method for determining the transmission potential of a 220kV line according to claim 2, characterized in that Step S3, based on the data information obtained in step S1, calculates the power flow transfer ratio of the key line of the target area power grid after the N-1 fault, and specifically includes the following steps: The following formula is used to calculate the power flow transfer ratio of the key lines of the target area power grid after N-1 faults: Where β i,j is the power flow transfer ratio of the i-th key line to the j-th key line after N-1 failure; P j ' ,line is the power flow of the jth key line after the i-th key line fails at N-1; P j,line is the power flow of the jth key line before the N-1 failure of the i-th key line; P i,line is the power flow of the i-th critical line before N-1 failure.

4. The method for determining the transmission potential of a 220 kV line according to claim 3, characterized in that The step S4 of calculating the power flow data of the checkpoint line of the target area power grid based on the power flow transfer ratio obtained in step S3 specifically includes the following steps: The power flow of the target area power grid's checkpoint line is calculated using the following formula: β i,j ·P i,line +P j,line =P j,line,N Where P j,line,N is the continuous maximum transmission capacity of the j-th checkpoint line; the checkpoint line is defined as the critical line where the transmission power of the 220kV line reaches the maximum transmission capacity when N-1 faults occur in other critical lines.

5. The method for determining the transmission potential of a 220 kV line according to claim 4, characterized in that Step S5, based on the power flow data obtained in step S4 and the current power supply mode and load level of the target area power grid, calculates the power flow sensitivity of the key line after the load increase, specifically including the following steps: Based on the current power supply mode and load level of the target area power grid, the load of each substation is set to increase simultaneously according to the set growth rate; The power flow sensitivity of the key lines after the assumed load increase is calculated using the following formula: Where δ i is the power flow sensitivity of the i-th key line in the target area power grid after the set load increase; P i ' ,line,up is the power of the i-th key line of the target area power grid after the set load increase; P i,line,up is the power of the i-th key line in the target area power grid before the set load increase.

6. The method for determining the transmission potential of a 220 kV line according to claim 5, characterized in that Calculating the load growth ratio of the target area power grid based on the power flow sensitivity obtained in step S5 in step S6 specifically includes the following steps: The following formula is used to calculate the load growth ratio of the target area power grid when the i-th key line is used as the checkpoint line: Where η i " is the load growth ratio of the target area power grid when the i-th key line is used as the checkpoint line; P i,line,N is the continuous limit transmission capacity of the i-th key line; At the same time, if the load growth is nonlinear, then for η i ", the perturbation method is used for further optimization, and the load growth ratio η' is corrected i is η′ i =η i ”+Δη i , Δη i is the load growth ratio step value adopted by the perturbation method; Finally, if the load growth ratio is linear, the load growth ratio η of the target area power grid is i is η i =η i "; If the load growth ratio is nonlinear, the load growth ratio of the target area power grid is η i is η i =η i '.

7. The method for determining the transmission potential of a 220 kV line according to claim 6, characterized in that Step S7, based on the load growth ratio obtained in step S6, calculates the maximum power supply capacity of the target area power grid and the increased power transmission capacity of the key lines, which specifically includes the following steps: The maximum power supply capacity of the target area power grid is calculated using the following formula: P load =P 0,load +ΔP i,load Where P load is the maximum power supply capacity of the target area power grid; P 0,load Initial power supply capacity of the target area power grid; ΔP i,load is the increased load when the i-th key line of the target area power grid is used as a checkpoint line, and ΔP i,load =η i ·P 0,load ; The following formula is used to calculate the increased transmission capacity of the i-th key line: Where ΔP i,line I is the increased transmission capacity of the i-th key line; Line Rated safety control current for the critical circuit itself.

8. The method for determining the transmission potential of a 220 kV line according to claim 7, characterized in that Step S8, based on the maximum power supply capacity obtained in step S7 and the increased power transmission capacity of the key lines, completes the determination of the power transmission potential of the 220 kV lines of the target area power grid, specifically including the following steps: The transmission potential index ε of the 220kV line of the target area power grid is calculated as follows: Determine the transmission potential index ε: The larger the transmission potential index ε is, the greater the transmission potential of the 220 kV line in the target area power grid is.

9. A system for implementing the method for determining the transmission potential of a 220kV line according to any one of claims 1 to 8, characterized in that It includes a data acquisition module, a load calculation module, a transfer calculation module, a flow calculation module, a sensitivity calculation module, a growth calculation module, a capacity calculation module and a potential determination module; the data acquisition module, the load calculation module, the transfer calculation module, the flow calculation module, the sensitivity calculation module, the growth calculation module, the capacity calculation module and the potential determination module are connected in series in sequence; the data acquisition module is used to obtain data information of the target area power grid and upload the data information to the load calculation module; The load calculation module is used to calculate the basic load information of the key lines of the target area power grid based on the received data information, and upload the data information to the transfer calculation module; the transfer calculation module is used to calculate the power flow transfer ratio of the key lines of the target area power grid after N-1 faults based on the received data information, and upload the data information to the power flow calculation module; The power flow calculation module is used to calculate the power flow data of the checkpoint line of the target area power grid based on the received data information, and upload the data information to the sensitivity calculation module; The sensitivity calculation module is used to calculate the power flow sensitivity of the key lines after the set load increase based on the received data information and the current power supply mode and load level of the target area power grid, and upload the data information to the growth calculation module; The growth calculation module is used to calculate the load growth ratio of the target area power grid based on the received data information and upload the data information to the capacity calculation module; The capacity calculation module is used to calculate the maximum power supply capacity of the target area power grid and the increased transmission capacity of key lines based on the received data information, and upload the data information to the potential determination module; The potential determination module is used to determine the transmission potential of the 220kV lines in the target area power grid based on the received data information, the maximum power supply capacity and the increased transmission capacity of the key lines.

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