An adaptive closing method for lightning tripping of overhead collector lines in mountainous wind farms

Abstract

This invention relates to an adaptive closing method for overhead collector lines in mountainous wind farms that trips due to lightning strikes. Through multi-dimensional logical judgment based on lightning warning, current surges, protection actions, and current characteristics at the time of tripping, it can accurately identify transient lightning trips caused by ground potential backflash in overhead collector lines of mountainous wind farms. This effectively eliminates permanent faults, non-lightning faults, and accidental signal interference, resulting in high closing reliability. After determining that the tripping is due to ground potential backflash, an automatic delay is established to issue a reclosing signal, eliminating the need for manual fault location investigation and insulation testing. This significantly shortens the line outage time, avoiding the 1-2 day outage time of conventional methods and minimizing power loss. The reclosing delay Δt2 is set to be greater than the safe disconnection time of the wind turbine, preventing impact on the wind turbine and line equipment during the closing process. Simultaneously, the multi-step logical judgment prevents erroneous closing, ensuring the safe and stable operation of overhead collector lines and related equipment in mountainous wind farms.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power transmission line protection, and particularly to an adaptive reclosing method for lightning trip of overhead collector lines in mountain wind farms. Background Art

[0002] In the energy transmission system of mountain wind farms, the overhead collector line is the core link connecting single wind turbines and the booster station, and undertakes the key function of converging and transmitting the electric energy generated by the wind turbines to the booster station. Its safe and stable operation directly determines the operation reliability of the entire wind farm.

[0003] The mountain terrain of mountain wind farms is usually rough and steep. The overhead collector line needs to plan the path along with the terrain undulation, and often crosses complex landforms such as valleys, ridges, and ravines. These areas are exactly the high-incidence zones of thunderstorm activities, resulting in the long-term dilemma of high lightning trip rate for the overhead collector line, which becomes an outstanding problem困扰 the safe and stable operation of wind farms.

[0004] Currently, after the lightning trip of the overhead collector line in a wind farm, the conventional treatment method is to immediately organize manpower and material resources to conduct a fault point investigation: if a fault point is found, the fault point needs to be processed, and after the processing is completed and the line insulation is qualified, the overhead line is powered on; if no fault point is found, the line insulation also needs to be tested to be qualified before the line is powered on. This treatment process often takes 1 - 2 days or even longer, resulting in a large amount of power loss and consuming a large amount of human and material resources.

[0005] Through research, it is found that some lightning trips of the overhead collector line in mountain wind farms are caused by ground potential counterattack trips after lightning strikes on the tower or lightning protection wire. This type of trip belongs to an instantaneous fault: after the lightning directly strikes the tower, a high potential is generated on the grounding grid during the process of the lightning current discharging to the ground. This overvoltage acts on the line insulator, causing the insulator to flash over and form an instantaneous discharge channel. The power frequency current on the conductor forms a stable power frequency follow current along the discharge channel, and the flashover is short-circuited to the ground. The relay protection device monitors that the overcurrent reaches the protection setting value and then acts to trip the switch; after the switch trips, the power frequency follow current is cut off, and the insulator immediately restores insulation. Therefore, no fault point can be found during the investigation process of this type of fault, and the line can operate normally after power on. Currently, there is no reliable identification and correction method for ground potential counterattack trips caused by lightning strikes, and its improvement and innovation are imperative. Summary of the Invention

[0006] In view of the above situation, to overcome the defects of the prior art, the purpose of the present invention is to provide an adaptive reclosing method for lightning trip of overhead collector lines in mountain wind farms, which can immediately perform switch reclosing to correct the ground potential counterattack trip caused by lightning strike on the overhead collector line, avoid various losses during the fault point investigation process of such trip events, and improve the economic efficiency and reliability of the operation of the wind farm.

[0007] The technical solution solved by this invention is: An adaptive closing method for lightning-triggered overhead collector lines in mountainous wind farms is disclosed, which involves collecting lightning monitoring and early warning signals, overhead collector line protection device operation signals, three-phase current of the overhead collector line, and overhead collector line switch closing position signals. The lightning monitoring and early warning signals can be obtained from an atmospheric electric field meter, the overhead collector line protection device operation signals are obtained from the overhead collector line protection device itself, the three-phase current of the overhead collector line is obtained from the overhead collector line current transformer (CT), and the overhead collector line switch closing position signals are obtained from the overhead collector line switch cabinet.

[0008] Perform the following steps in sequence: Step 1: Determine whether the overhead collector line switch is in the closed position. If it is in the closed position, proceed to Step 2; otherwise, continue to determine the closing position signal of the overhead collector line switch. Step 2: Determine whether a lightning activity warning signal has been received. If so, record the warning period and proceed to Step 3; otherwise, continue to determine whether a lightning activity warning signal has been received. Step 3: During the lightning warning period, based on the collected three-phase current signals of A, B, and C, calculate the current mutation Δi_φ(t) of the three-phase current in real time, Δi_φ(t) = |i_φ(t) - i_φ(tT)|, where φ = the phase of the three phases A, B, and C, and T is the power frequency period of 20ms; if the current mutation of any X phase at any moment is greater than the start threshold value ΔI_set and the current mutation of the X phase at the previous sampling moment is less than the start threshold value ΔI_set, record this moment as t1, where 3 ≥ X ≥ 2, and ΔI_set is the mutation start threshold value of the line protection device; calculate the current mutation values ​​of X phase at N consecutive sampling moments after time t1. If all are greater than ΔI_set, proceed to step 4; otherwise, continue to collect three-phase current signals for mutation characteristic judgment. If the lightning warning time is exceeded, return to step 1; N is the number of judgment points based on the mutation start criterion of the protection device. Step 4: Determine whether the protection device issues a trip output signal within the time period (t1, t1+Δt), where Δt is the reset time of the entire protection device's sudden change. If it does, record the protection device's output time t2 and proceed to step 5; otherwise, return to step 1. Step 5: Calculate the effective value I of the three-phase current at time t2. φ1t2 I φ2t2 I φ3t2 When X is 3, if the effective values ​​of all three phase currents are greater than the overcurrent protection action threshold value I... set Then proceed to step 6; when X is 2, if the effective values ​​of both phase currents are greater than the overcurrent protection action threshold value Iset And the current in the other phase is less than I set If the condition is met, proceed to step 6; otherwise, return to step 1. Overcurrent protection action threshold value I set Taken from the calculation sheet for protection settings of overhead collector lines in a wind farm; Step 6: Send a reclosing signal to the line switch at time t2+Δt2 to complete adaptive closing. Δt2 is set to be greater than the safe disconnection time of the wind turbine.

[0009] Preferably, the start-up threshold value ΔI_set is 0.2In, where In is the rated current of the collector line.

[0010] Preferably, the value of N is 5, that is, the protection device is judged to start when the change criterion of 5 consecutive points is met.

[0011] Preferably, the sett of the complete reset time Δt for the sudden change of the protection device is 7 seconds.

[0012] Preferably, the wind turbine safe disconnection time setting Δt2 is taken as the typical value of the power distribution line reclosing time, which is 1.5s.

[0013] This invention is applicable to mountain wind farms where the collection lines are entirely overhead, or mountain wind farms with a mixed overhead-underground cable collection line where the overhead line accounts for no less than 70%. Compared with the prior art, this invention has the following advantages: (1) Accurately identify transient lightning strike faults: Through multi-dimensional logical judgment of lightning warning, current change, protection action, and current characteristics at the time of tripping, it can accurately identify transient lightning strike tripping caused by ground potential backlash in the overhead collection line of the mountain wind farm, effectively eliminating permanent faults, non-lightning strike faults and accidental signal interference, and ensuring high reliability of closing. (2) Achieve adaptive fast closing: After the ground potential backflash lightning trip is determined, the reclosing signal is automatically delayed, eliminating the need for manual fault point investigation and insulation testing, greatly shortening the line outage time, avoiding the 1-2 day outage time of conventional handling methods, and minimizing power loss. (3) Save human and material resources: It eliminates the need for manual troubleshooting and line testing after a lightning trip, avoiding the waste of human, equipment, and vehicle resources, significantly reducing the operation and maintenance costs of wind farms and improving the economic efficiency of wind farm operation. (4) Ensure safe operation of equipment: The reclosing delay Δt2 is set to be greater than the safe disconnection time of the wind turbine to avoid impact on the wind turbine and line equipment during the closing process. At the same time, the multi-step logic judgment can prevent accidental closing and ensure the safe and stable operation of the overhead collection line and related equipment of the mountain wind farm. (5) Wide range of applications: It is not only applicable to mountain wind farms with pure overhead collection lines, but also to mixed collection lines with an overhead line ratio of not less than 70%, which can meet the collection line protection needs of most mountain wind farms. Detailed Implementation

[0014] The specific embodiments of the present invention will be further described in detail below with reference to examples.

[0015] This embodiment describes an adaptive closing method for overhead collector lines in mountainous wind farms that trips due to lightning strikes. First, four types of core signals are collected: lightning monitoring and early warning signals, overhead collector line protection device operation signals, three-phase current of the overhead collector line, and overhead collector line switch closing position signals.

[0016] Among them, the lightning monitoring and early warning signals are taken from lightning monitoring equipment such as atmospheric electric field meters; the action signals of the overhead collector line protection devices are taken from the overhead collector line protection devices; the three-phase current of the overhead collector line is taken from the overhead collector line CT (current transformer); and the switch closing position signals of the overhead collector line are taken from the overhead collector line switch cabinet.

[0017] Based on the signals collected above, the following six steps are executed sequentially to complete the adaptive closing of the lightning-triggered circuit breaker: Step 1: Determine if the switch is in the closed position Determine whether the overhead collector line switch is in the closed position. If the overhead collector line switch is in the closed position, it means that the basic conditions for normal operation of the line are met, and proceed to the next step. If the switch is not in the closed position, continue to judge the closing position signal of the overhead collector line switch until the switch is closed or other protection logic is triggered.

[0018] Step 2: Judgment of Lightning Activity Warning Determine whether a lightning activity warning signal has been received from equipment such as an atmospheric electric field meter. If a lightning activity warning signal is received, record the warning period (i.e., the effective time range of the lightning warning) and proceed to the next step. If no signal is received, continue to determine whether a lightning activity warning signal is received and rule out line faults caused by factors other than lightning strikes.

[0019] Step 3: Determining the characteristics of sudden changes in three-phase current during the lightning warning period During the lightning warning period, based on the collected three-phase current signals (A, B, and C), the instantaneous change in three-phase current Δi_φ(t) is calculated in real time. The calculation formula is as follows: Δi_φ(t)=|i_φ(t)-i_φ(tT)| Where φ = the phases of the three phases A, B, and C, respectively, and T is the power frequency period, with a value of 20ms.

[0020] If at any given moment the current surge of any X phase (3≥X≥2, i.e., two or three phases) is greater than the starting threshold value ΔI_set, and the current surge of the X phase at the previous sampling moment is less than the starting threshold value ΔI_set, it indicates that a sudden current surge has occurred in the line at this moment, which is consistent with the current characteristics of a ground potential backflash fault. This moment is recorded as t1.

[0021] Wherein, ΔI_set is the threshold value for the sudden change in the line protection device, preferably 0.2In (In is the rated current of the collector line).

[0022] Subsequently, the current mutation values ​​of phase X at N consecutive sampling times after time t1 are calculated, and it is determined whether the current mutation values ​​at these N sampling times are all greater than ΔI_set. If they are all satisfied, it indicates that the current mutation is a continuous sudden characteristic, and random interference is excluded, and the process proceeds to step 4. If it is not satisfied, the three-phase current signals are collected again to determine the mutation characteristics. If the lightning warning time is exceeded, the process returns to step 1 and the logic judgment is restarted.

[0023] Among them, N is determined by the number of points to be judged according to the sudden change start criterion of the protection device, and the preferred value is 5 (the protection device is judged to start when the sudden change criterion of 5 consecutive points is met).

[0024] Step 4: Determine the trip output signal of the protection device Determine whether the overhead collector line protection device issues a trip output signal within the time period (t1, t1+Δt), where Δt is the reset time of the entire protection device's sudden change, preferably 7 seconds.

[0025] If the protection device operates and issues a trip output signal within this time period, it indicates that the current change in step 3 triggered this line protection action, which conforms to the protection logic of ground potential backflash trip. Record the protection device output time t2 and proceed to the next step; if no trip output signal is issued, return to step 1 and restart the logic judgment.

[0026] Step 5: Re-evaluate the current characteristics at the moment of tripping Calculate the effective values ​​of the three-phase currents at the protection device output time t2, and denot them as I. φ1t2 I φ2t2 I φ3t2 Combined with the determination of phase X (two-phase or three-phase) in step 3, the effective value of the current is determined: When X is 3 (three-phase current sudden change), if the effective values ​​of all three phase currents are greater than the overcurrent protection action threshold value I... set This indicates that all three phases have experienced overcurrent faults, which is consistent with the overcurrent characteristics of a ground potential backflash trip. When X is 2 (two-phase current sudden change), if the effective values ​​of both phase currents are greater than I... set And the current in the other phase is less than I set This indicates that two phases are overcurrent and one phase is normal, which is consistent with another overcurrent characteristic of ground potential backflash trip.

[0027] In the above judgment, I set The overcurrent protection action threshold value is directly taken from the wind farm overhead collector line protection setting calculation sheet; if the above corresponding judgment conditions are met, proceed to step 6; if not, return to step 1 and restart the logic judgment.

[0028] Step 6: Send a switch reclosing signal Based on the protection device's output time t2, after a delay of Δt2, a reclosing signal is sent to the line switch to complete the adaptive closing of the overhead collector line after lightning trip.

[0029] Among them, Δt2 is set to be greater than the safe disconnection time of the wind turbine, and the typical value of 1.5s for the reclosing time of the distribution line is preferred to ensure that the closing process will not cause impact on the wind turbine equipment and ensure the safety of the wind turbine and line equipment.

[0030] The adaptive closing method for lightning tripping of overhead collector lines in mountain wind farms of the present invention is applicable to mountain wind farms where the collector lines are all overhead lines, and is also applicable to mountain wind farms with overhead-underground cable mixed collector lines where the proportion of overhead lines is not less than 70%.

[0031] The method of this invention has achieved good technical results in practical applications, as shown in the following examples: Application Example 1: The rated current of the overhead collector III line of a wind farm is 0.82A (secondary effective value, the same below). The overcurrent protection action value of the collector III line is 4.92A, the action time is 0 seconds, the current surge threshold is 0.2In, which is 0.164A, and the number of sampling points per cycle current is 52. At 12:15:28.1341 on March 3, 2025, the overcurrent protection of the collector III line of the wind farm tripped, and reclosing was successful at 12:15:29.6445. The data recorded is as follows: (1) At 12:10 on March 3, 2025, the wind farm lightning warning system issued a lightning warning signal, predicting a red lightning warning in the next 15 minutes; (2) At 12:15:28.1174, the current of phases B and C of the collector line III of the wind farm suddenly changed. The current change values ​​of the five consecutive sampling points after this moment are shown in the table below: (3) 12:15:28.1341, the overcurrent protection of collector III line is activated. At this time, IA is 0.541A, IB is 6.713A and IC is 6.928A.

[0032] (4) At 12:15:29.6445, a switch reclosing signal was sent. At 12:15:21.6951, the switch reclosing was successful.

[0033] That is: Signal acquisition: The atmospheric electric field instrument of the wind farm issues a lightning monitoring and early warning signal, and at the same time acquires the action signal of the collector III line protection device, the A / B / C three-phase current signal, and the switch cabinet switch closing position signal; Step 1: Determine that the collector III line switch is in the closed position, then proceed to Step 2; Step 2: At 12:10 on March 3, 2025, a red lightning warning signal was received. The lightning warning period is expected to last for the next 15 minutes. Record this period and proceed to Step 3. Step 3: At 12:15:28.1170, the sudden changes in phase B and C currents are 0.129A and 0.147A respectively, both less than ΔI_set=0.164A; at 12:15:28.1174, the sudden changes in phase B and C currents are 0.168A and 0.182A respectively, both greater than ΔI_set. Record this time as t1; after t1, the sudden changes in phase B and C currents at 5 consecutive sampling points are all greater than 0.164A, satisfying the N=5 criterion, proceed to step 4; Step 4: During the time period (t1, t1+7s), at 12:15:28.1341, the overcurrent protection of collector III line operates and sends a trip output signal. Record this time as t2, and proceed to step 5. Step 5: Calculate the effective values ​​of the three-phase currents at time t2: IA = 0.541A, IB = 6.713A, IC = 6.928A; Step 3 determines X = 2 (phases B and C), the effective values ​​of the currents in these two phases are both greater than I. set =4.92A, and IA is less than I. set If the judgment condition is met, proceed to step 6; Step 6: At time t2+1.5s=12:15:29.6445, a switch reclosing signal is sent, and the switch reclosing is successful, restoring power to the line.

[0034] Application Example 2: The rated current of the overhead collector line I of a wind farm is 0.73A (secondary effective value, the same below). The overcurrent protection action value of collector line I is 5.1A, the action time is 0 seconds, the current surge threshold is 0.146A, and the number of sampling points per cycle current is 52. On July 21, 2025, at 18:01:38.9783, the overcurrent protection of collector line I of the wind farm tripped, and reclosing was successful at 18:01:40.5246. The data analysis is as follows: (1) At 17:50 on July 21, 2025, the wind farm's lightning warning system issued a lightning warning signal, predicting a red lightning warning in the next 20 minutes; (2) At 18:01:38.9711, the current of phases A, B, and C of the collector I line of the wind farm suddenly changed. The values ​​of the sudden changes at the five consecutive current sampling points after this moment are shown in the table below: (3) 18:01:38.9783, the overcurrent protection of collector I line is activated. At this time, IA is 6.051A, IB is 6.132A, and IC is 6.065A.

[0035] (4) At 18:01:40.4695, a switch reclosing signal was sent. At 18:01:40.5246, the switch reclosing was successful.

[0036] That is: Signal acquisition: The lightning locator of the wind farm issues a lightning monitoring and early warning signal, and at the same time acquires the action signal of the collector I line protection device, the A / B / C three-phase current signal, and the switch cabinet switch closing position signal; Step 1: Determine that the collector I line switch is in the closed position, then proceed to Step 2; Step 2: At 17:50 on July 21, 2025, a red lightning warning signal was received. The lightning warning period is expected to last for the next 20 minutes. Record this period and proceed to Step 3. Step 3: At 18:01:38.9707, the sudden changes in the three-phase currents of A, B, and C are all less than ΔI_set = 0.146A; at 18:01:38.9711, the sudden changes in the three-phase currents of A, B, and C are 0.261A, 1.902A, and 1.631A respectively, all greater than ΔI_set. Record this time as t1; after t1, the sudden changes in the three-phase currents at 5 consecutive sampling points are all greater than 0.146A, satisfying the N=5 criterion, proceed to step 4; Step 4: During the time period (t1, t1+7s), at 18:01:38.9783, the collector I line overcurrent protection operates and sends a trip output signal. Record this time as t2, and proceed to step 5. Step 5: Calculate the effective values ​​of the three-phase currents at time t2: IA = 6.051A, IB = 6.132A, IC = 6.065A; Step 3: Determine X = 3 (three-phase), the effective values ​​of the three-phase currents are all greater than I. set =5.1A, the judgment condition is met, proceed to step 6; Step 6: At time t2+1.5s=18:01:40.4695, a switch reclosing signal is sent. At time 18:01:40.5246, the switch reclosing is successful, and power supply to the line is restored.

[0037] The two application examples above both verify the effectiveness of the adaptive closing method for lightning tripping of overhead collector lines in mountain wind farms of the present invention. It can quickly and accurately identify ground potential backflash lightning tripping and complete adaptive closing, successfully restoring power supply to the line without power loss or waste of manpower and material resources, and the closing process does not cause any impact on the equipment.

Claims

1. A method for adaptive closing of overhead collector lines in mountainous wind farms after lightning tripping, characterized in that, Collect lightning monitoring and early warning signals, overhead collector line protection device operation signals, three-phase current of overhead collector lines, and switch closing position signals of overhead collector lines; Perform the following steps in sequence: Step 1: Determine whether the overhead collector line switch is in the closed position. If it is in the closed position, proceed to Step 2; otherwise, continue to determine the closing position signal of the overhead collector line switch. Step 2: Determine whether a lightning activity warning signal has been received. If so, record the warning period and proceed to Step 3; otherwise, continue to determine whether a lightning activity warning signal has been received. Step 3: During the lightning warning period, based on the collected three-phase current signals of A, B, and C, calculate the current mutation Δi_φ(t) of the three-phase current in real time, Δi_φ(t) = |i_φ(t) - i_φ(tT)|, where φ = the phase of the three phases A, B, and C, and T is the power frequency period of 20ms; if the current mutation of any X phase at any moment is greater than the start threshold value ΔI_set and the current mutation of the X phase at the previous sampling moment is less than the start threshold value ΔI_set, record this moment as t1, and ΔI_set is the mutation start threshold value of the line protection device; calculate the current mutation values ​​of X phase at N consecutive sampling moments after t1. If all are greater than ΔI_set, proceed to step 4; otherwise, continue to collect three-phase current signals for mutation characteristic judgment. If the lightning warning time is exceeded, return to step 1; N is the number of judgment points based on the mutation start criterion of the protection device. Step 4: Determine whether the protection device issues a trip output signal within the time period (t1, t1+Δt), where Δt is the reset time of the entire protection device's sudden change. If it does, record the protection device's output time t2 and proceed to step 5; otherwise, return to step 1. Step 5: Calculate the effective value I of the three-phase current at time t2. φ1t2 I φ2t2 I φ3t2 When X is 3, if the effective values ​​of all three phase currents are greater than the overcurrent protection action threshold value I... set Then proceed to step 6; when X is 2, if the effective values ​​of both phase currents are greater than the overcurrent protection action threshold value I set And the current in the other phase is less than I set If the condition is met, proceed to step 6; otherwise, return to step 1. Overcurrent protection action threshold value I set Taken from the calculation sheet for protection settings of overhead collector lines in a wind farm; Step 6: Send a reclosing signal to the line switch at time t2+Δt2 to complete adaptive closing. Δt2 is set to be greater than the safe disconnection time of the wind turbine.

2. The adaptive closing method for lightning tripping of overhead collector lines in mountain wind farms according to claim 1, characterized in that, The starting threshold value ΔI_set is set to 0.2In, where In is the rated current of the collector line.

3. The adaptive closing method for lightning tripping of overhead collector lines in mountain wind farms according to claim 1, characterized in that, The value of N is 5.

4. The adaptive closing method for lightning tripping of overhead collector lines in mountain wind farms according to claim 1, characterized in that, The set time Δt for the complete set of mutations in the protection device is 7 seconds.

5. The adaptive closing method for lightning tripping of overhead collector lines in mountain wind farms according to claim 1, characterized in that, The wind turbine's safe disconnection time setting Δt2 is taken as the typical value of the power distribution line reclosing time, which is 1.5s.

6. The adaptive closing method for lightning tripping of overhead collector lines in mountain wind farms according to any one of claims 1-5, characterized in that, This method is applicable to mountain wind farms where the collection lines are all overhead lines, or mountain wind farms where the proportion of overhead lines is not less than 70% and the collection lines are a mixture of overhead and underground cables.

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