Classification of Diploma Thesis – opponent
Author of classification: Ing. Jan Veleba, Ph.D.
Supervisor: Ing. Petr Kačor, Ph.D.
Opponents: Ing. Jan Veleba, Ph.D.
Title: AC Arc Flash Analysis
Thesis version: 1
Student: Iuliia Volodina
1. Meeting the requirements of the thesis assignment.
The student familiarized herself with the arc flash analysis according to IEEE 1584-2018 and NFPA 70E-2018 standards. She provided the overall theoretical background to this topic including detailed formulas, approaches for arc flash calculations, recommendations for mitigation measures and design of arc flash labels. The student also did calculations for real-life power system with respect to arc flash analysis. For these calculations, ABB Excel calculation tool and an alternative web-based program jCalc.NET were used. The arc flash analysis is quite a new topic, which is not well-known on academic soil. Moreover, arc flash standard (IEEE 1584) was updated 3 years ago by introducing a much complex and advanced approach for providing key arc flash results. Due to these reasons, not many relevant sources are available yet and those existing ones are only available in English. Despite of this highly complex topic, the student fulfilled all points in her thesis assignment and provided her thesis on a very high quality level.
2. Thesis technicality evaluation.
The thesis is well structured, the chapters logically follow each other, own calculations and solutions are in balance with the theoretical background. The thesis seems to have a compact and high quality format. The student kept in mind to show results in form of tables and figures and also to show all relevant formulas, coefficients and other sources belonging to the calculation model. Text part of the thesis contains 45 pages divided into seven chapters and subchapters including introduction and conclusion. The thesis further contains the lists of references, symbols and abbreviations, tables, images and charts. In terms of the content, the conclusion is fully sufficient. English language used is on a high quality level, no mistypes were found. All tables, charts and graphs are transparent and clearly readable.
3. Results evaluation of the thesis.
The thesis shows that the results from Arc flash calculation tool, the alternative tool jCalc.NET and from IEEE 1584-2018 / NFPA 70E-2018 are comparable and in all calculation cases identical.
Remarks on the thesis:
page 52: It is mentioned that 10 ms safety reserve is used for REA+UFES solution. However, on page 53 there is only 2.5 ms + 2.5 ms (i.e. no extra safety reserve used). Therefore, the results would not be so optimistic, but a bit worse in value.
4. Evaluation of the new findings contribution.
This thesis complements the previous thesis (Bc. Petr Vavricek, Arc Flash Hazard Analysis, 2015), which was focussing on arc flash calculations according to IEEE 1584-2002 and NFPA 70E-2012 standards. The benefit of this thesis is in the detailed overview of formulas and of methodology for arc flash hazard evaluation based on up-to-date IEEE 1584-2018 and NFPA 70E-2018 standards. The formulas are more complex and the overall calculation process more laborious than the process in the old -2002 standard. Currently, the thesis can be used for students and workers, who start doing arc flash calculations and seek for compact source of information to this topic. Next logical step would be to compare the results from Arc flash calculation tool with the results provided by commercial softwares used in ABB Ostrava office (SKM Power Tools for Windows, ETAP, DIgSILENT PowerFactory). Also, it would be beneficial to record the differences in the results from IEEE 1584- 2018 and IEEE 1584-2002 standards (whether the results are close to each other, or not; which results are with which input data more pessimistic or optimistic, etc.).
5. Utilization and selection of information sources.
The student selected suitable sources for her thesis. She refers to them throughout her thesis and by
this it is obvious which information is gathered from the sources and which belongs to student's own results, comments or conclusions.
6. Question for the defense of the thesis.
1) Please, explain, why conservative arc flash calculations are not the best practice all the time. To be on the safe side by using pessimistic input data and assumptions might be generally a correct
approach, but also may provide certain operational risks. Which?
2) Mitigation measures are listed in chapter 5.1. Can something be proposed as a mitigation measure with respect to working distance? Can you provide some real examples?
7. Summary evaluation.
According to my personal opinion, the thesis is on a very high quality level. It fulfills all requirements and therefore I recommend it for approval.
excellent Overall classification:
Ostrava, 09.05.2021 Ing. Jan Veleba, Ph.D.
