Lightning stroke risk assessment method for distribution line containing distributed photovoltaic system

Abstract

A lightning stroke risk assessment method for a distribution line comprising a distributed photovoltaic system comprises the following steps: building a distribution line overvoltage calculation model comprising the distributed photovoltaic system, and calculating the lightning resistance levels of a photovoltaic side and a line side; calculating the lightning stroke fault rate of the photovoltaic system and the fault rate of the photovoltaic system when the line side is struck by lightning by using the electrical geometric model of the photovoltaic side; calculating the lightning trip-out rate of each tower on the line and the trip-out rate of the tower on the line when the photovoltaic system is struck by lightning by using the electrical geometric model on the line side; calculating the annual average electric energy loss rate through the total failure rate of the photovoltaic system; and summarizing the calculated lightning stroke trip-out rate of each tower on the line and the trip-out rate of the tower on the line when the photovoltaic system is struck, obtaining the total lightning stroke trip-out rate of the tower on the line side, and performing risk assessment on each tower on the line side according to lightning stroke risk conditions borne by different towers. According to the method, the lightning stroke risk of the active power distribution network can be quantitatively evaluated, and a reference is provided for differentiated lightning protection transformation of the active power distribution system.

Description

Technical Field

[0001] The present invention belongs to the technical field of lightning risk assessment, and in particular relates to a method for assessing lightning risk of a distribution line containing a distributed photovoltaic system. Background Art

[0002] At present, new energy represented by distributed photovoltaics will be widely connected to the distribution network. Compared with traditional distribution lines, distributed photovoltaic systems are installed on open roofs and are located at high positions, making them vulnerable to lightning strikes, thus affecting the overall stable operation of active distribution lines. At present, the research on lightning risk assessment of distribution lines containing photovoltaic systems mainly focuses on the distribution lines or photovoltaic systems themselves, but there is a mutual influence between the photovoltaic side and the line side, that is, the lightning overvoltage may not only cause flashover failure on the lightning-struck side itself, but also threaten adjacent photovoltaic or distribution systems. Therefore, it is urgent to propose a lightning risk assessment method for active distribution networks that considers the influence of intrusion waves. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for assessing the lightning strike risk of a distribution line containing a distributed photovoltaic system, which can quantitatively assess the lightning strike risk of an active distribution network and provide a reference for the differentiated lightning protection transformation of an active distribution system. The technical solution adopted by the present invention is:

[0004] A method for assessing lightning strike risk of a distribution line including a distributed photovoltaic system comprises the following steps:

[0005] Step 1: Obtain information about the photovoltaic system, lines, and towers, build an overvoltage calculation model for distribution lines containing distributed photovoltaic systems, and calculate the lightning resistance levels on the photovoltaic side and line side;

[0006] Step 2: Build an electrical geometry model on the photovoltaic side. According to the lightning resistance level of the photovoltaic side calculated in step 1, use the electrical geometry model on the photovoltaic side to calculate the lightning failure rate of the photovoltaic system itself and the failure rate of the photovoltaic system when lightning strikes the line side.

[0007] Step 3: Build an electrical geometry model on the line side. According to the lightning resistance level of the line side calculated in step 1, use the electrical geometry model on the line side to calculate the lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when lightning strikes the photovoltaic system;

[0008] Step 4: Summarize the lightning failure rate of the photovoltaic system itself and the failure rate of the photovoltaic system when lightning strikes the line side calculated in step 2 to obtain the total failure rate of the photovoltaic system, and calculate the annual average power loss rate based on the total failure rate of the photovoltaic system;

[0009] Step 5: Conduct risk assessment on the photovoltaic system using the annual average power loss rate as an indicator;

[0010] Step 6: Summarize the calculated lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when lightning strikes the photovoltaic system to obtain the total lightning tripping rate of the towers on the line side, and conduct risk assessment on each tower on the line side according to the lightning risk conditions of different towers.

[0011] In the step 1, the photovoltaic array model and geometric parameters, inverter model and capacity, line model of conductors and ground wires, tower structure, span length, and power frequency voltage level are obtained; an overvoltage calculation model for distribution lines containing distributed photovoltaic systems is established in ATP-EMTP; and the lightning resistance levels of the photovoltaic side and the line side are calculated by changing the lightning current form and node position in the model.

[0012] For the photovoltaic side, it is necessary to obtain the actual photovoltaic system equipment information and model; for the line side, it is necessary to obtain the actual line and each tower parameter, including: the model parameters of the conductor and ground wire, tower drawings, span length, and power frequency voltage level. In step 2, the electrical geometry model of the photovoltaic side is used to calculate the photovoltaic system's own lightning strike failure rate and the photovoltaic system failure rate when the lightning strikes the line side. The calculation formula is as follows:

[0013] TR 光伏 =TR z +TR g

[0014]

[0015] Among them: TR 光伏 is the lightning failure rate of the photovoltaic system, unit: times / year; TR z TR is the direct lightning failure rate, unit: times / year; g is the induced lightning failure rate, unit: times / year; η is the arcing rate; P(I) is the number of lightning current peaks greater than I z ,I g The cumulative probability of z ,I g They are the lightning resistance levels for direct lightning and induction lightning faults, in kA; N D is the average number of direct lightning strikes per year, unit: times / year; N m It is the average annual number of induced lightning strikes, unit: times / year, and the calculation formula is as follows:

[0016] N D =N g A d C d 10 -6

[0017] N m =N g (A m -A d Cd )10 -6

[0018] Where: N g is the density of ground-to-ground lightning, unit: times / (km 2 a); C d A is the coefficient that takes into account the influence of the relative position of the protected object; d is the equivalent receiving area of ​​the photovoltaic array, unit: m 2 ; A m The maximum equivalent area of ​​induced lightning, unit: m 2 , the calculation formula is as follows:

[0019] A d =LW+6(H+W)+9π(H) 2

[0020]

[0021] Where: L represents the length of the photovoltaic array, unit: m; W represents the width of the photovoltaic array, unit: m; H is the height of the photovoltaic array, unit: m; D m The distance between the lightning-sensitive area and the building.

[0022] In step 3, the electrical geometry model on the line side is used to calculate the lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when lightning strikes the photovoltaic system. The calculation formula is as follows:

[0023] TR=TR 反击 +TR 绕击 +TR 感应

[0024]

[0025] Where, TR is the line side lightning trip rate, unit: times / (100km·a); TR 反击 is the counter-tripping rate, unit: times / (100km·a); TR 绕击 TR is the shielding failure tripping rate, unit: times / (100km·a); 感应 is the induced lightning tripping rate, unit: times / (100km·a); g is the pole striking rate; I A ,I B ,I C They are the lightning resistance levels of counter-attack, bypass and induction lightning, unit: kA; D k is the width of the lightning rod, unit: m; y max,k The amplitude of the induced lightning current is I k The maximum critical flashover distance at , unit: m, is calculated as follows:

[0026]

[0027] y max,I =4I-57.6

[0028] Where b is the width of the tower cross arm, unit: m; h is the height of the conductor to the ground, unit: m; I is the lightning current amplitude, unit: kA; R s is the exposure arc strike distance, unit: m; R g is the ground striking distance, unit: m, the calculation formula is as follows:

[0029]

[0030] In step 4, the annual average power loss rate is calculated by the total failure rate of the photovoltaic system, and the calculation formula is as follows:

[0031] W L =(TR z +TR g )·P·T

[0032] Among them, W L is the annual power loss rate, unit: kWh / year; P is the photovoltaic power generation power, unit: kW; T is the average power outage duration, unit: h / time.

[0033] In step 5, the risk assessment of the photovoltaic system is carried out using the annual average power loss as an indicator, and the annual average power loss of the photovoltaic system caused by lightning strikes is calculated in combination with the annual average power loss rate calculation formula, and the risk level is given according to the value.

[0034] In step 6, risk assessment is performed on each tower on the line side, specifically including:

[0035] Level I risk towers indicate the lowest risk, with a theoretical trip rate of 0, meaning that lightning strikes here will basically not cause line flashover or PV side failures, and lightning strikes on the PV side will not cause flashover of this level of towers;

[0036] II1 level risk towers are: Lightning strikes here will cause line flashover, but will not cause faults on the photovoltaic side, nor will they be affected by lightning intrusion waves on the photovoltaic side;

[0037] II2 level risk towers are: Lightning strikes here will not cause line flashover, but will cause faults on the photovoltaic side, and will not cause tripping on the photovoltaic side;

[0038] II3 level risk towers indicate that lightning strikes here will not cause line flashover or PV side failure, but will be affected by lightning strikes and cause tripping;

[0039] Level III1 risk means that lightning strikes here will not cause line flashover, but will cause faults on the PV side, and there is a risk of tripping caused by lightning strikes on the PV;

[0040] Level III2 risk means that lightning strikes here only cause flashover on the line side and will not affect the PV side, but the PV side may be tripped by lightning.

[0041] Level III3 risk means that lightning strikes here may affect both the line side and the PV side, but will not be affected by lightning strikes on the PV side;

[0042] Level IV risk means that lightning strikes here may affect both the line side and the photovoltaic side, and there is a possibility that the photovoltaic side will be affected by lightning strikes.

[0043] The present invention provides a method for assessing lightning strike risks of distribution lines containing a distributed photovoltaic system, and the technical effects are as follows:

[0044] 1) Step 1 of the present invention establishes a refined overvoltage calculation model for distribution lines containing distributed photovoltaic systems based on basic information of actual active distribution lines, which can calculate the lightning resistance level on both sides of the active distribution lines when considering the influence of lightning intrusion waves;

[0045] 2) Step 2 of the present invention proposes a method for calculating the lightning failure rate of a photovoltaic system under the influence of an intrusion wave, which provides a certain reference for risk assessment of active distribution lines;

[0046] 3) Step 3 of the present invention calculates the line-side lightning trip rate under the influence of the intrusion wave, which provides a certain reference for the risk assessment of active distribution lines;

[0047] 4) Step 4 of the present invention calculates the annual average power loss rate under the influence of the intrusion wave based on the lightning meter failure rate of the photovoltaic system calculated in step 2, paving the way for risk assessment of the photovoltaic system;

[0048] 5) Step 5 of the present invention proposes a risk level classification method for photovoltaic systems, and performs quantitative risk assessment on active distribution lines;

[0049] 6) Step 6 of the present invention proposes a risk level classification method for the distribution line side, and performs quantitative risk assessment on active distribution lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0051] Figure 1 This is a flow chart of the method for assessing lightning strike risk of power distribution lines of the present invention.

[0052] Figure 2 This is the electrical geometry model diagram of the photovoltaic system.

[0053] Figure 3 This is the electrical geometry model diagram of the line side.

[0054] Figure 4 This is a schematic diagram of the risk level classification standard.

[0055] Figure 5 It is a line trend diagram in the embodiment.

[0056] Figure 6 Graph showing the line-side lightning trip rate in the embodiment.

[0057] Figure 7 This is a line-side lightning strike risk distribution diagram in the embodiment. DETAILED DESCRIPTION

[0058] The purpose of the present invention is to propose an electrical geometry model of a photovoltaic system based on the principle of equivalent receiving area, calculate the lightning resistance level of the photovoltaic side and the line side by building a distribution line overvoltage model containing a distributed photovoltaic system in ATP, calculate the photovoltaic side's own failure rate and the line side's tripping rate when the photovoltaic side is struck by lightning, and calculate the line side's own tripping rate and the photovoltaic side's failure rate when the line side is struck by lightning in combination with the electrical geometry models of the photovoltaic side and the line side, and finally summarize the calculation results of the lightning tripping rate to obtain the annual power loss rate of the photovoltaic side and the total lightning tripping rate of each tower on the line side, and the annual average power loss rate and the lightning tripping rate can be used to quantify the risk assessment of the active distribution network system, thereby providing a reference for the differentiated lightning protection transformation of the active distribution system.

[0059] In order to achieve the above-mentioned object, the present invention provides a method for assessing the lightning risk of a distribution line containing a distributed photovoltaic system. The assessment flow chart is as follows: Figure 1 As shown, it includes the following steps (1) to (6):

[0060] Step (1): Based on the actual PV system, line, and tower parameters, build a distribution line overvoltage model containing a distributed PV system in ATP, and calculate the lightning withstand level on the PV side and the line side;

[0061] For the photovoltaic side, it is necessary to obtain the actual photovoltaic system equipment information and model. The specific data information is shown in Table 1.

[0062] Table 1 Photovoltaic system parameter information

[0063]

[0064] For the line side, it is necessary to obtain the actual line and tower parameters, including the model parameters of the conductor and ground wire, tower drawings, span length, power frequency voltage level. The specific data information is shown in Table 2.

[0065] Table 2 Distribution line parameter information

[0066]

[0067] Step (2): Build the electrical geometry model of the photovoltaic side as follows Figure 2 As shown, according to the PV side lightning resistance level calculated in step (1), the PV side electrical geometry model is used to calculate the PV system's own lightning strike failure rate and the PV system failure rate when lightning strikes the line side. The calculation formula is as follows:

[0068] TR 光伏 =TR z +TR g

[0069]

[0070] Among them: TR 光伏 is the lightning failure rate of the photovoltaic system, unit: times / year; TR z TR is the direct lightning failure rate, unit: times / year; g is the induced lightning failure rate, unit: times / year. According to GB / T 50064-2014 "Design Specification for Overvoltage Protection and Insulation Coordination of AC Electrical Installations", the arcing rate η is 0.56; P(I) is the lightning current peak value greater than I z ,I g The cumulative probability, I z ,I g They are the lightning withstand levels for direct lightning and induced lightning faults, in kA. According to the lightning current probability density function, when the lightning current amplitude is greater than 200 kA, the probability of lightning current occurrence is almost 0 and can be ignored. Therefore, the upper limit of the integral in the formula for calculating the trip rate is 200.

[0071] N D is the average number of direct lightning strikes per year, unit: times / year; N m It is the average annual number of induced lightning strikes, unit: times / year, and the calculation formula is as follows:

[0072] N D =N g A d C d 10 -6

[0073] N m =N g (A m -A d C d )10 -6

[0074] Where: N g is the density of ground-to-ground lightning, unit: times / (km 2 a); C dA is the coefficient that takes into account the influence of the relative position of the protected object, as shown in Table 3; d is the equivalent receiving area of ​​the photovoltaic array, unit: m 2 ; A m The maximum equivalent area of ​​induced lightning, unit: m 2 , the calculation formula is as follows:

[0075] A d =LW+6(H+W)+9π(H) 2

[0076]

[0077] Where: L represents the length of the photovoltaic array, unit: m; W represents the width of the photovoltaic array, unit: m; H is the height of the photovoltaic array, unit: m; D m The distance between the lightning induction area and the building is 125m.

[0078] Table 3 Position influence coefficient C d

[0079]

[0080] Step (3): Build the electrical geometry model of the line side as follows Figure 3 As shown, according to the lightning resistance level of the line side calculated in step (1), the line side electrical geometry model is used to calculate the lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when lightning strikes the photovoltaic system. The calculation formula is as follows:

[0081] TR=TR 反击 +TR 绕击 +TR 感应

[0082]

[0083] Where, TR is the line side lightning trip rate, unit: times / (100km·a); TR 反击 is the counter-tripping rate, unit: times / (100km·a); TR 绕击 TR is the shielding failure tripping rate, unit: times / (100km·a); 感应 is the induced lightning tripping rate, unit: times / (100km·a). The pole striking rate g is taken as 0.5 according to the IEEE calculation process; I A ,I B ,I C They are the lightning resistance levels of counter-strike, bypass strike and induction lightning, in kA. k is the width of the lightning rod, unit: m; y max,k The amplitude of the induced lightning current is I kThe maximum critical flashover distance when the unit is m, using the induced lightning calculation model in ATP to calculate y max,k The calculation formula is as follows:

[0084]

[0085] y max,I =4I-57.6

[0086] Where b is the width of the tower cross arm, unit: m; h is the height of the conductor to the ground, unit: m; I is the lightning current amplitude, unit: kA; R s is the exposure arc strike distance, unit: m; R g is the ground striking distance, unit: m, where R s , R g The calculation formula refers to the lightning protection calculation standard proposed by IEEE, and the calculation formula is as follows:

[0087]

[0088] Step (4): Summarize the lightning failure rate of the photovoltaic system itself and the photovoltaic system failure rate when the lightning strikes the line side calculated in step (2) to obtain the total failure rate of the photovoltaic system. The annual average power loss rate is calculated based on the total failure rate of the photovoltaic system. The calculation formula is as follows:

[0089] W L =(TR z +TR g )·P·T

[0090] Among them, W L is the annual power loss rate, unit: kWh / year; P is the photovoltaic power generation power, unit: kW; T is the average power outage duration, unit: h / time.

[0091] Step (5): Conduct risk assessment on the photovoltaic system using the annual average power loss as an indicator.

[0092] Step (6): Summarize the lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when the photovoltaic system is struck by lightning, and obtain the total lightning tripping rate of the tower on the line side. According to the lightning risk of different towers, risk assessment is performed on each tower on the line side. The classification standard is as follows: Figure 4 shown.

[0093] Among them, the I-level risk tower indicates the lowest risk, and its theoretical tripping rate is 0, that is, lightning strikes here will basically not cause line flashover or photovoltaic side faults, and lightning strikes on the photovoltaic side will not cause flashover of this level of towers; II1-level risk towers are: lightning strikes here will cause line flashover, but will not cause photovoltaic side faults, and will not be affected by lightning strikes on the photovoltaic side. The II2-level risk tower is: lightning strikes here will not cause line flashover, but will cause photovoltaic side faults, and will not be tripped by lightning strikes on the photovoltaic side; II3-level risk towers indicate that lightning strikes here will not cause line flashover or photovoltaic Level III1 risk indicates that lightning strike here will not cause line flashover, but will cause fault on the PV side, and there is a risk of tripping caused by lightning strike on the PV side; Level III2 risk indicates that lightning strike here will only cause flashover on the line side and will not affect the PV side, but may cause tripping on the PV side; Level III3 risk indicates that lightning strike here may affect both the line side and the PV side, but will not be affected by lightning strike on the PV side; Level IV risk indicates that lightning strike here may affect both the line side and the PV side, and there is a possibility of being affected by lightning strike on the PV side.

[0094] Example:

[0095] The direction of distributed photovoltaic grid-connected lines in a certain area is as follows Figure 5 As shown, there are 12 photovoltaic users on the photovoltaic side of the active distribution line, each with a distance of 10m. The photovoltaic panel model is ZXP6-72-350W, with a length, width and height of 20m, 10m and 10m respectively, and a grid-connected capacity of 20kW. They are all connected to meters, DC junction boxes and inverters, of which the inverter model is SG7 / 8K-D. Finally, they are connected to the 380V distribution line tower and connected to the 10kV distribution line through the SHB-15 distribution transformer, and the transformer capacity is 240kVA. Among them, the flashover voltage U of the insulator of the 380V distribution line tower is 50％ It is 30kV.

[0096] The type of the distribution line side tower is a straight tower with a tower height of 15m, a cross arm width of 2m, a grounding resistance of 10Ω, no lightning arrester, and an insulator flashover voltage U 50％ It is 100kV. The Guantang Second Station branch line has 4 towers, and the spacing between each tower is 30m. The Baiguan line has 10 towers, and the spacing between each tower is 50m.

[0097] According to the actual line direction and basic information, the overvoltage calculation model of the distribution line containing the distributed photovoltaic system is established in ATP, and the lightning resistance levels of the photovoltaic side and the line side are calculated as shown in Table 4 and Table 5:

[0098] Table 4 Lightning strike line side

[0099]

[0100] Table 5 Lightning strikes photovoltaic side

[0101]

[0102] According to the above calculation results of lightning resistance level, combined with the electrical geometric models of photovoltaic side and line side, the lightning failure rate of photovoltaic side is calculated as shown in Table 6, and the lightning tripping rate of line side is shown in Table 6. Figure 6 As shown, the density of ground flashes on the photovoltaic side is 10 times / (unit: km 2 a).

[0103] Table 6 Lightning failure rate on photovoltaic side

[0104]

[0105] After calculation: the total failure rate of the photovoltaic side (including the failure rate of the photovoltaic side caused by lightning and the failure rate of the photovoltaic system caused by lightning on the distribution line side) is 3.0766 times / year, and the total power generation capacity of the photovoltaic side is 240kW. According to the "Guiding Opinions on Accelerating the Construction and Reconstruction of Distribution Networks", the average power outage duration for each household in my country does not exceed 1 hour. Taking the photovoltaic system failure as an example, each power outage of 1 hour can be analyzed. It can be calculated that the annual power loss rate of the photovoltaic system is about 738kWh / year. Overall, the failure rate of the photovoltaic system is still relatively low.

[0106] according to Figure 4 The risk classification criteria shown, combined with Figure 6 The line tower trip rate calculation results shown in the figure are used to conduct risk assessment on the line side towers of the active distribution system. Figure 7 As shown. Figure 7 It can be seen that the tower closest to the photovoltaic side has the greatest lightning strike risk and the highest lightning tripping rate. Compared with the #4 tower, the lightning strike risk of the tower farther away from the photovoltaic side will be further reduced to level III3. The towers at this risk level are not affected by lightning strikes on the photovoltaic side, but will affect the photovoltaic side when they are struck by lightning. The tower at the end of the line has the lowest risk, which is level II1. Its lightning strike characteristics are basically unrelated to the photovoltaic side of the system and can be analyzed separately as a distribution line.

[0107] Based on the equivalent area receiving principle, the present invention proposes an electrical geometry model of the photovoltaic system, uses the actual distribution line parameters containing distributed photovoltaic systems to establish an overvoltage calculation model in ATP, calculates the lightning failure rate of the photovoltaic system and the lightning tripping rate of the tower on the line through the electrical geometry models on the photovoltaic side and the line side, and uses the annual average power loss rate and lightning tripping rate as indicators to conduct risk assessment on the photovoltaic system and distribution line, thereby conducting a quantitative risk assessment on the active distribution network. This provides a reference for the differentiated lightning protection transformation of the active distribution system.

Claims

1. A method for assessing lightning strike risk of distribution lines containing distributed photovoltaic systems, characterized in that The following steps are involved: Step 1: Obtain information about the photovoltaic system, lines, and towers, build an overvoltage calculation model for distribution lines containing distributed photovoltaic systems, and calculate the lightning resistance levels on the photovoltaic side and line side; Step 2: Build an electrical geometry model on the photovoltaic side. According to the lightning resistance level of the photovoltaic side calculated in step 1, use the electrical geometry model on the photovoltaic side to calculate the lightning failure rate of the photovoltaic system itself and the failure rate of the photovoltaic system when lightning strikes the line side. Step 3: Build an electrical geometry model on the line side. According to the lightning resistance level of the line side calculated in step 1, use the electrical geometry model on the line side to calculate the lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when lightning strikes the photovoltaic system; Step 4: Summarize the lightning failure rate of the photovoltaic system itself and the failure rate of the photovoltaic system when lightning strikes the line side calculated in step 2 to obtain the total failure rate of the photovoltaic system, and calculate the annual average power loss rate based on the total failure rate of the photovoltaic system; Step 5: Conduct risk assessment on the photovoltaic system using the annual average power loss rate as an indicator; Step 6: Summarize the calculated lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when lightning strikes the photovoltaic system to obtain the total lightning tripping rate of the towers on the line side, and conduct risk assessment on each tower on the line side according to the lightning risk conditions of different towers.

2. A method for assessing lightning strike risk of a distribution line containing a distributed photovoltaic system according to claim 1, characterized in that: In the step 1, the photovoltaic array model and geometric parameters, inverter model and capacity, line model of conductors and ground wires, tower structure, span length, and power frequency voltage level are obtained; In ATP-EMTP, an overvoltage calculation model for distribution lines containing distributed photovoltaic systems is established; by changing the lightning current form and node position in the model, the lightning withstand level on the photovoltaic side and the line side is calculated; For the photovoltaic side, the actual photovoltaic system equipment information and model are obtained; for the line side, the actual line and each tower parameter are obtained, including: model parameters of conductors and ground wires, tower drawings, span length, and power frequency voltage level.

3. A method for assessing lightning strike risk of a distribution line containing a distributed photovoltaic system according to claim 1, characterized in that: In step 2, the electrical geometry model of the photovoltaic side is used to calculate the photovoltaic system's own lightning failure rate and the photovoltaic system failure rate when the lightning strikes the line side. The calculation formula is as follows: TR 光伏 =TR z +TR g Among them: TR 光伏 is the lightning failure rate of the photovoltaic system, unit: times / year; TR z TR is the direct lightning failure rate, unit: times / year; g is the induced lightning failure rate, unit: times / year; η is the arcing rate; P(I) is the number of lightning current peaks greater than I z ,I g The cumulative probability of z ,I g They are the lightning resistance levels for direct lightning and induction lightning faults, in kA; N D is the average number of direct lightning strikes per year, unit: times / year; N m It is the average annual number of induced lightning strikes, unit: times / year, and the calculation formula is as follows: N D =N g A d C d 10 -6 N m =N g (A m -A d C d )10 -6 Where: N g is the density of ground-to-ground lightning, unit: times / (km 2 a); C d A is the coefficient that takes into account the influence of the relative position of the protected object; d is the equivalent receiving area of ​​the photovoltaic array, unit: m 2 ; A m The maximum equivalent area of ​​induced lightning, unit: m 2 , the calculation formula is as follows: A d =LW+6(H+W)+9π(H) 2 Where: L represents the length of the photovoltaic array, unit: m; W represents the width of the photovoltaic array, unit: m; H is the height of the photovoltaic array, unit: m; D m The distance between the lightning-sensitive area and the building.

4. A method for assessing lightning strike risk of a distribution line containing a distributed photovoltaic system according to claim 1, characterized in that: In step 3, the electrical geometry model on the line side is used to calculate the lightning tripping rate of each tower on the line and the tripping rate of the tower on the line when lightning strikes the photovoltaic system. The calculation formula is as follows: TR=TR 反击 +TR 绕击 +TR 感应 Where, TR is the line side lightning trip rate, unit: times / (100km·a); TR 反击 is the counter-tripping rate, unit: times / (100km·a); TR 绕击 TR is the shielding failure tripping rate, unit: times / (100km·a); 感应 is the induced lightning tripping rate, unit: times / (100km·a); g is the pole striking rate; I A ,I B ,I C They are the lightning resistance levels of counter-attack, bypass and induction lightning, unit: kA; D k is the width of the lightning rod, unit: m; y max,k The amplitude of the induced lightning current is I k The maximum critical flashover distance at , unit: m, is calculated as follows: and max,I =4I-57.6 Where b is the width of the tower cross arm, unit: m; h is the height of the conductor to the ground, unit: m; I is the lightning current amplitude, unit: kA; R s is the exposure arc strike distance, unit: m; R g is the ground striking distance, unit: m, the calculation formula is as follows:

5. A method for assessing lightning strike risk of a distribution line containing a distributed photovoltaic system according to claim 1, characterized in that: In step 4, the annual average power loss rate is calculated by the total failure rate of the photovoltaic system, and the calculation formula is as follows: W L =(TR z +TR g )·P·T Among them, W L is the annual power loss rate, unit: kWh / year; P is the photovoltaic power generation power, unit: kW; T is the average power outage duration, unit: h / time.

6. A method for assessing lightning strike risk of a distribution line containing a distributed photovoltaic system according to claim 1, characterized in that: In step 5, the risk assessment of the photovoltaic system is carried out using the annual average power loss as an indicator, and the annual average power loss of the photovoltaic system caused by lightning strikes is calculated in combination with the annual average power loss rate calculation formula, and the risk level is given according to the value.

7. A method for assessing lightning strike risk of a distribution line containing a distributed photovoltaic system according to claim 1, characterized in that: In step 6, risk assessment is performed on each tower on the line side, specifically including: Level I risk towers indicate the lowest risk, with a theoretical trip rate of 0, meaning that lightning strikes here will basically not cause line flashover or PV side failures, and lightning strikes on the PV side will not cause flashover of this level of towers; II1 level risk towers are: Lightning strikes here will cause line flashover, but will not cause faults on the photovoltaic side, nor will they be affected by lightning intrusion waves on the photovoltaic side; II2 level risk towers are: Lightning strikes here will not cause line flashover, but will cause faults on the photovoltaic side, and will not cause tripping on the photovoltaic side; II3 level risk towers indicate that lightning strikes here will not cause line flashover or PV side failure, but will be affected by lightning strikes and cause tripping; Level III1 risk means that lightning strikes here will not cause line flashover, but will cause faults on the PV side, and there is a risk of tripping caused by lightning strikes on the PV; Level III2 risk means that lightning strikes here only cause flashover on the line side and will not affect the PV side, but the PV side may be tripped by lightning. Level III3 risk means that lightning strikes here may affect both the line side and the PV side, but will not be affected by lightning strikes on the PV side; Level IV risk means that lightning strikes here may affect both the line side and the photovoltaic side, and there is a possibility that the photovoltaic side will be affected by lightning strikes.

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