Partial Discharge Characteristics of C3F7CN Gas Mixture Using the UHF Method
, Lujia Chen 1,*, Qiang Liu 1, Mark Waldron 2, Gordon Wilson 2, Roberto Fernandez Bautista 3 and Malcolm Seltzer-Grant 3Round 1
Reviewer 1 Report
Please, refer to the attached document. Thanks!
Comments for author File: 
Comments.pdf
Author Response
Please find attached our response to Reviewer 1's report.
Author Response File: Author Response.pdf
Reviewer 2 Report
This paper investigates the PD characteristics of 20% C3F7CN / 80% CO2 gas mixture 65 and SF6 gas under AC voltage using external ultra-high frequency (UHF) sensors. However, some issues need to be addressed. Below are the concerns:
1. In the Introduction part, the review work concerning this area should be presented more detailedly. Besides, the shortcomings of the previous work, the advantages of your work, the challenges to be solved and the novelties should be clearly explained. In the current version, the main work of the authors' is focused on, but the superiority or improvement is not clear.
2. The text in Figure 1 is too small to read.
3. In Section 2, simulation setups should be given clearly. Besides, the significance of simulation should be given. What are the simulations results related to your research in the latter sections?
4. What are the differences between the experimental setups introduced in this paper and the other studies? If the differences are significant, please show comparative explanations. Otherwise, Section 3 only introduces the experimental results, which is not appropriate.
5. What are the experimental results helpful for in practice?
Finally, the contents in all parts are not sufficient. It is highly recommended to enrich the contents. At least 16 pages are welcome.
Author Response
Please find attached our response to Reviewer 2's report.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article discusses the issue of evaluation of partial discharges generated by model systems placed in the atmosphere of the C3F7CN gas mixture. The problem of replacing the commonly used SF6 insulating gas with other alternative gases / mixtures that are more environmentally friendly is a very current issue and widely commented by scientists. Replacing gas in existing installations is difficult because it requires comprehensive research and adaptation to new conditions that are not entirely identical. Especially the behavior of the new insulating medium over a longer period of operation and its usability values are of key importance for the replacement process. For this reason, it should be considered that the topics presented and the achievements achieved are important and up-to-date. The subject matter is also in line with the profile of the MDPI Energies journal and contains the required scientific knowledge for this type of publication.
Generally I can say, that the language used in the work is correct and understandable, and the graphics are at an appropriate level. I only have a few debatable comments asking for a comment from the authors. I have also found a few editorial mistakes.
Below is a detailed list of questions or suggestions for possible improvement, which I hope will increase the quality of the article.
11) Figure 3 shows the recording from the UHF probe in the case of discharge detection and to show the noise level. Unfortunately, the results are located on one scale and shifted relative to each other, which, in the author's intention, was certainly supposed to improve the readability of the drawing, but unfortunately, the readers may have the impression that the waveforms contain a constant component (offset), which makes it difficult to assess their parameters.
22) Figure 7 shows the recordings obtained for pure CO2 and CF7CN at different pressures to show the effect of each gas on the obtained result. The authors' intention is to reflect the overall situation for the results shown in the previous figures. Unfortunately, it seems to me that it is impossible to justify the observed phenomena in this way, because the principle of superposition does not work here. We probably see a synergy phenomenon here, because overlapping the obtained waveforms will not give us a situation like the one in Figures 6. Please comment it.
33) There were slight editorial errors in the work in three places:
- in line 439 and 441, quantity f should be in italics
- in line 446, number 6 should be written as a subscript.
Author Response
Please find attached our response to Reviewer 3's report.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear Authors,
there was probably an error or forgetfulness in uploading my review. If you check my review some of my questions highlighted in yellow in the text that I am attaching have not received an answer so I can only make partial considerations and it does not seem ethical. However, at the moment I see that the article has been thoroughly restructured and better organized, the answers, even if partial, have helped this reviewer.
Comments for author File: Comments.pdf
Reviewer 2 Report
No more comments.
