Impact of Grounding Modeling on Lightning-Induced Voltages Evaluation in Distribution Lines
, Rodolfo Antônio Ribeiro de Moura 2,*,†, Renato Procopio 1,† and Marco Aurélio de Oliveira Schroeder 2,†Round 1
Reviewer 1 Report
The methodology is sound and the conclusion is reasonable.
In the captions of Table 1 and 2, “Passive” had better be dropped, as the equivalent circuits contain negative resistance.
Please display lightning current waveforms or current parameters to improve readability.
How is the difference in induced voltages if the closest point of DL to the stroke location is in the mid span?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1. Any circuit requiring a distributed parameters analysis is termed
"Transmission line" in scientific literature;
the context may be that of Transmission systems (TS) or Distribution Systems (or TLC); the terminology adopted, limiting the use of "transmission line" to lines part of a TS is very unusual and misleading.
2. Often, the order of words in sentences appears ensuing from a literal translation instead of an English construction; sentences are sometimes too long. Readability must be improved.
3. Lines 59-63: the solution may be fast only if a recursive convolution is adopted; however the expressions considered for the ground transient impedances are not in exponential form, so that the recursive convolution cannot be implemented directly. Other formulations are available and convenient.
4. Line 79: Insulators should be modeled by means of their parasitic capacitance.
5. The test case is not clear (or wrong): with a span of 300 m, an height (maximum, at the tower) of 10-12 meters is not sufficient; the sag of the conductors is several meters (with that cross section of conductors)! Please explain clearly what you have done, why and limits.
6. Line 138: "distance" means horizontal distance ?
7. Line 143: the propagation velocity of EM fields along the tower is generally reduced with respect to c according with extensive experimental data: add a comment.
8. Give all geometrical data of the tower.
9. Add units in figure 2 and the tower position (sketch in 3D)
10. Lines 151 and ff.: this is the main part of the paper and, in my opinion, should be more detailed. In fact, number of branches, i.e. criterion/a for its choice, passivity enforcement and check of the accuracy must be explained and discussed. It is very strange that in the low frequency limit the equivalent conductance is negative in the second case. Some errors in the signs should be present.
As a general comment, in any scientific paper it is requested that approximations, along with their limits of applicability and expected accuracy, are clearly stated. No mention at all about this fundamental aspect is made (while it is adequate a reference for the formulation).
Moreover, very likely, the overall numerical accuracy of the proposed procedure is of the same order of magnitude (or worse) than results variations reported in table 5, the validity and usefulness of which is questionable.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper calculates the induced voltage in the shield wire and conductors of a 3-phase transmission line due to indirect lightning. The paper compares the cases where the wideband impedance of the grounding electrodes has been used vs. the case the low-frequency value of the grounding of the electrodes The computation model consists of the following components that are all well-known and existing:
- Transmission line: represented by Telegrapher’s equations using constant, frequency-independent PUL parameters
- EM fields due to lightning: available in [24]
- Field-to line coupling: Agrawal’s model [26]
- Tower: Single piece of transmission line with Zc given by (3)
- Grounding electrodes impedance: calculated using HEM [19]
- Incorporation in a EMT simulator: Vector Fitting
All of these components are well known and their validity has been verified. However, in the opinion of the reviewer, some major components have been ignored that the authors have to prove not considering them will not cause a significant error. The simplifying assumptions and missing components are:
- The coupling between the tower and the induced electric field by the indirect lightning strike has been ignored.
- The string of the insulators has been replaced simply by a gap, that is the capacitance of the string of insulators has been ignored.
- The coupling between the indirect lightning and the grounding electrodes
- Frequency-dependence of the soil parameters has not been considered
Notwithstanding the above, it is not clear whether the results are still valid or not.
Editorial:
Line 13: “Direct events occur when the lightning directly strikes the line; such events are hazardous but rare and are typically studied and analyzed in the framework of Transmission Lines (TL).” “framework of Transmission Lines (TL)” in this sentence is not clear.
Line 15: Use “On the other hand” not “On the other side”.
Avoid using “thanks to” in lines 53, 61, and 169.
Line 172: “this” must become “these”.
Line 174: The sentence “Hence …” is incomplete.
Figure 6: “Beginning” not “Beggining”
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I still have some doubts about the values reported in Table 2: in DC, we have an equivalent conductance which is negative, being the sum of all negative quantities and of a negligible positive one.
I know very well all the discussions about the (possible) negative quantities yielding from the Gustavsen-Semlyen method and the overall passivity, but, unfortunately, this is not the case.
Of course, having fixed all the previous problems, comment #10 has been automatically "fixed", apart from the above mentioned issue.
The accent in the word Cigré is wrong (Line 84): usually it is capitalized, like IEEE, never seen ieee or Ieee.
Author Response
Comment: I still have some doubts about the values reported in Table 2: in DC, we have an equivalent conductance which is negative, being the sum of all negative quantities and of a negligible positive one.
I know very well all the discussions about the (possible) negative quantities yielding from the Gustavsen-Semlyen method and the overall passivity, but, unfortunately, this is not the case.
Of course, having fixed all the previous problems, comment #10 has been automatically "fixed", apart from the above mentioned issue.
Answer: We are very grateful and would like to thank the reviewer for the detailed analysis that he/she has presented. Indeed he/she is right. For low resistivity and considering the soil’s parameters as constant, disregarding the complex pole obtained by the vector fitting was a plausible approximation. However, in the second version, where we considered the soil’s frequency-dependence, this was not an adequate approximation leading to a possible not-passive circuit. Thus, we would like to thank the reviewer and let him/her know that we have changed the equivalent circuit and all results and analysis. Now it is considered both real and complex poles. All the modifications are in blue. Please check the final version of the revised paper.
Comment: The accent in the word Cigré is wrong (Line 84): usually it is capitalized, like IEEE, never seen ieee or Ieee.
Answer: We thank you for this observation and inform you that we have made the necessary correction. Please check this correction in the revised paper.
Reviewer 3 Report
Thank you for addressing my comments and revising the manuscript.
One more comment:
End of second last paragraph of the Introduction: Please make it clear to the readership the assumptions you are making that are neglecting the coupling between the tower and lightning channel, and neglecting the coupling between the lightning and the grounding electrodes. Also, in the Conclusions you may include the incorporation of the coupling between the lightning channel and the electrodes as a proposed future work considering papers such as the following.
M. Nazari, R. Moini, S. Fortin, F. P. Dawalibi and F. Rachidi, "Impact of Frequency-Dependent Soil Models on Grounding System Performance for Direct and Indirect Lightning Strikes," in IEEE Transactions on Electromagnetic Compatibility, vol. 63, no. 1, pp. 134-144, Feb. 2021, doi: 10.1109/TEMC.2020.2986646.
Author Response
Comment: Thank you for addressing my comments and revising the manuscript.
Answer: It was our pleasure to address all the reviewer's comments. Indeed we would like to thank you for all your comments.
Comment: End of second last paragraph of the Introduction: Please make it clear to the readership the assumptions you are making that are neglecting the coupling between the tower and lightning channel, and neglecting the coupling between the lightning and the grounding electrodes. Also, in the Conclusions you may include the incorporation of the coupling between the lightning channel and the electrodes as a proposed future work considering papers such as the following.
M. Nazari, R. Moini, S. Fortin, F. P. Dawalibi and F. Rachidi, "Impact of Frequency-Dependent Soil Models on Grounding System Performance for Direct and Indirect Lightning Strikes," in IEEE Transactions on Electromagnetic Compatibility, vol. 63, no. 1, pp. 134-144, Feb. 2021, doi: 10.1109/TEMC.2020.2986646.
Answer: We thank you for this indication and inform you that we have made the necessary correction. Please check this correction in the revised paper. Just a piece of additional information that all modifications are in blue.
