Simulation of Cloud-to-Ground Lightning Strikes to Wind Turbines Considering Polarity Effect Based on an Improved Stochastic Lightning Model
Round 1
Reviewer 1 Report
The paper faces an interesting and actual topic and presents novelties with respect to the influence of the Polarity effect on the lightning damage risk for wind turbines. An improved stochastic lightning model is constructed, and a modified method for predicting the annual lightning flash number is proposed. It stresses the importance of the polarity effect, lightning current amplitude, and blade rotations in estimating the lightning strike risk of wind turbines. This work will be of great interest to those studying lightning strike protection of wind turbines. So, the paper is highly recommended for publication in Atmosphere. Below are some remarks for the article:
(1) The research involves the lightning-induced effects with wind turbines, also noted as pending key issues so far, namely, the Polarity effect. Preliminary studies about the differences between +CG lightning and -CG lightning can reveal the physical process of +CG/-CG lightning. The research has theoretical significance and practical value and has enough innovation.
(2) The authors extend the understanding of the lightning damage risk of wind turbines under the -CG lightning and +CG lightning by dealing with the interaction of downward and multiple upward leaders. The analyses of the lightning strike risk of wind turbines also cover the influence of wind turbine height, blade rotation, and lightning current amplitude. Quantitative conclusions presented in the paper could deepen the scientific understanding of the interaction between flashes and wind turbines, which provide a more physically realistic basis for lightning protection analysis. Comparisons with the observed data and other scholars’ researches prove the reliability and the accuracy of the calculation method in the paper.
(3) As for the leader progression, new possible extensions and the probability to determine the subsequent channel point is given by Equation (1), however, in my opinion, the section of this Equation is not clear to me in some points, this is a standard formula, which is to say that, given an input, the output will be a solid one. In that case, the authors should clearly explain how to represent stochastic behavior.
(4) The paper is complete with clear logic. But there are some wrong English words in the paper. The title “Quantitative Prediction of Downward Lightning Risk Associated with Wind Turbine Considering Polarity effect based on an Improved Stochastic Lightning Model” is suggested to be modified as “Simulation of cloud-to-ground lightning strikes to Wind Turbines Considering Polarity effect based on an Improved Stochastic Lightning Model”.
Author Response
回复审稿人 1 条评论
亲爱的评论家，
我们感谢您的意见和建议，并将其纳入修订稿“atmosphere-2069203”中。我们仔细考虑了审稿人的所有评论，并相应地修改了我们的手稿。
要点1：该研究涉及风力涡轮机的雷电效应，也被认为是迄今为止悬而未决的关键问题，即极性效应。初步研究+CG闪电与-CG闪电的区别可以揭示+CG/-CG闪电的物理过程。该研究具有理论意义和实用价值，具有足够的创新性。
Response 1: Thank you so much for your best comments. We will continue to work hard on the next work to make greater innovation.
Point 2: The authors extend the understanding of the lightning damage risk of wind turbines under the -CG lightning and +CG lightning by dealing with the interaction of downward and multiple upward leaders. The analyses of the lightning strike risk of wind turbines also cover the influence of wind turbine height, blade rotation, and lightning current amplitude. Quantitative conclusions presented in the paper could deepen the scientific understanding of the interaction between flashes and wind turbines, which provide a more physically realistic basis for lightning protection analysis. Comparisons with the observed data and other scholars’ researches prove the reliability and the accuracy of the calculation method in the paper.
Response 2: Thank the reviewer for the recognition and the affirmation of our work. We will continue to work hard on the next work to make greater innovation.
Point 3: As for the leader progression, new possible extensions and the probability to determine the subsequent channel point is given by Equation (1), however, in my opinion, the section of this Equation is not clear to me in some points, this is a standard formula, which is to say that, given an input, the output will be a solid one. In that case, the authors should clearly explain how to represent stochastic behavior.
Response 3: We gratefully appreciate for your valuable comment. The certainty of the leader development is reflected in that the greater the field intensity of the potential breakdown points exceeds the threshold, the greater the probability that it will be broken down by the next step to form the leader channel. The randomness of leader development is reflected in that the point with the highest breakdown probability may not necessarily develop into a breakdown point, but the probability of all the ac-cumulated potential development points will be normalized into a probability interval [0,1] according to the calculated breakdown probability. The next breakdown point of the leader will be chosen by the random number generated by the random function. And the vague statement pointed out by the reviewer have been corrected in the updated manuscript.
Point 4: The paper is complete with clear logic. But there are some wrong English words in the paper. The title “Quantitative Prediction of Downward Lightning Risk Associated with Wind Turbine Considering Polarity effect based on an Improved Stochastic Lightning Model” is suggested to be modified as “Simulation of cloud-to-ground lightning strikes to Wind Turbines Considering Polarity effect based on an Improved Stochastic Lightning Model”.
Response 4: We gratefully appreciate for your valuable comment. The title have been modified in the updated manuscript and we have read through the manuscript carefully and have made corrections of wrong English words.
如果对我们的论文还有任何问题或疑问，请随时告诉我们。非常感谢您关注我们的论文。
真挚地，
作者们
Author Response File: 
Author Response.docx
Reviewer 2 Report
This manuscript titled “Quantitative Prediction of Downward Lightning Risk Associated with Wind Turbine Considering Polarity effect based on an Improved Stochastic Lightning Model” presents a numerical and stochastic approach for the risk assessment of wind turbine structures against downward lightning strikes. A modified Stochastic Lightning Model is employed to calculate the predicted risks quantitatively.
Finally, I recommend publication of this manuscript in Atmoshpere after being revised based on the comments below.
1) The review of previous works is not detailed enough to emphasise the difference between this study and the others. The paper has some new original investigation and deserves to emphasize its originality. For a more thorough review of the literature, I recommend the following;
a. Lighhtning strike on structures and its hazardous effects need to be discussed in more detail. In this section I recommend referring to these papers as examples
i. 10.3390/app10217769
ii. 10.1007/s11069-011-9754-3
b. Structural properties of wind turbines (blades) need to be more included.
i. 10.1088/1742-6596/1037/4/042027
ii. 10.3390/vibration4010001
2) It is recommended that this paper to be restructured to separate methodology and results in different sections. Results and discussion can be a separate section where all the results compiled and discussed in depth. It would help the readers to follow the flow easily.
3) Figure 13 consist of lines and only one point for validation. So, geometrically speaking, the lines pass close to these points but their slope is not validated. A justification for this figure is required.
Author Response
Response to Reviewer 2 Comments
Dear reviewers,
We appreciate your comments and suggestions and take them into account in the revised manuscript “atmosphere-2069203”. We have carefully considered all comments from reviewers and revised our manuscript accordingly.
Point 1: The review of previous works is not detailed enough to emphasise the difference between this study and the others. The paper has some new original investigation and deserves to emphasize its originality. For a more thorough review of the literature, I recommend the following;
- Lightning strike on structures and its hazardous effects need to be discussed in more detail. In this section I recommend referring to these papers as examples
- 10.3390/app10217769
- 10.1007/s11069-011-9754-3
- Structural properties of wind turbines (blades) need to be more included.
- 10.1088/1742-6596/1037/4/042027
- 10.3390/vibration4010001
Response 1: Those comments are valuable and very helpful, we have read through comments carefully and have made corrections. According to the reviewer’s comment, We add the description of the lightning strike on structures, its hazardous effects and structural properties of wind turbines (blades) in the updated manuscript: In the past studies, lightning strikes have caused serious damage to buildings. A lightning strike can cause partial damage or complete failure of structures. The lightning current that passes through the structure may cause heating of the roof system rapidly, and even fire [2]. Natural hazards such as lightning can cause major accidents in chemical and process installations [3]. And wind turbines are usually constructed on the top or the ridge of hills in hilly or offshore regions, and due to its geographical location effects, lightning strikes have also become main causes of wind turbine damages. For a wind turbine, the major parts that are exposed to the environment are the tower, the nacelle and the rotor. And the composite rotor blade is the most susceptible to direct lightning strikes as it is higher off the ground than the other components. Note that, blades usually are made of a strong and stiff shell as the skin and a stiffener web or lightweight core material. This structure reduces weight while preserving strength, and a rotor blade failure can have a significant impact on turbine downtime and safety [4,5]. However, the vigorous development of the wind power industry and the expansion of its capacity and scale are accompanied by the higher risk of wind turbines being struck by lightning [6].
Four references recommend by the reviewer have been cited in the updated manuscript.
- Tüfekci, M., Tüfekci, E., & Dikicioğlu, A. (2020). Numerical investigation of the collapse of a steel truss roof and a probable reason of failure. Applied Sciences, 10(21), 7769.
- Krausmann, E., Renni, E., Campedel, M., & Cozzani, V. (2011). Industrial accidents triggered by earthquakes, floods and lightning: lessons learned from a database analysis. Natural Hazards, 59(1), 285-300.
- Tüfekci, M., Genel, Ö. E., Tatar, A., & Tüfekci, E. (2020). Dynamic analysis of composite wind turbine blades as beams: an analytical and numerical study. Vibration, 4(1), 1-15.
- Ozyildiz, M., Muyan, C., & Coker, D. (2018, June). Strength analysis of a composite turbine blade using puck failure criteria. In Journal of Physics: Conference Series (Vol. 1037, No. 4, p. 042027). IOP Publishing.
Point 2: It is recommended that this paper to be restructured to separate methodology and results in different sections. Results and discussion can be a separate section where all the results compiled and discussed in depth. It would help the readers to follow the flow easily.
Response 2: We gratefully thanks for the precious time the reviewer spent making constructive remarks. According to reviewer’s comment, the description of the modified calculation methods of the the annual lightning flash number under the -CG/+CG lightning has focused on section 3, then, all the relevant conclusions and analyses are further discussed in the section 4. The corresponding chapter titles, the order of figures and tables have also been revised. The organisation problems of the paper pointed out by the reviewer have been corrected in the updated manuscript.
Point 3: Figure 13 consist of lines and only one point for validation. So, geometrically speaking, the lines pass close to these points but their slope is not validated. A justification for this figure is required.
Response 3: We gratefully appreciate for your valuable comment. It should be pointed out that there are few papers about observations of the annual total number of lightning strikes on the wind turbine at present. After a lot of searching, we found it that the observed value of the annual total number of lightning strikes on the wind turbine reported by the Garolera is the most most detailed and the most reliable. So, the data reported by Garolera is used as a comparison in our paper. However, we cannot find any data report on of the annual total number of lightning strikes on the other high wind turbines. Thus, in order to validate the slope of our figure and further verify the reliability of our model, the calculation results from the IEC 61400-24, the Eriksson model, the IEC (EGM) model, the Rizk model and the method presented in the updated manuscript are compared in Figure 14. (Page 11). The comparative results show that the results obtained in this paper can better reflect the downward lightning risk of the wind turbine, which not only has a great protection margin, but also does not overstate the lightning protection level.
If there are any more problem or questions about our paper, please do not hesitate to let us know. Thank you very much for your attention to our paper.
Sincerely,
The authors
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Since the revision recommendations I provided I incorporated, I have no further comments and would now recommend publication of this manuscript in its present form.
