Metrics

  • citations in SCIndeks: 0
  • citations in CrossRef:0
  • citations in Google Scholar:[]
  • visits in previous 30 days:9
  • full-text downloads in 30 days:4

Contents

article: 3 from 11  
Back back to result list
Insulation stresses of power equipment exposed to non-standard overvoltage waveforms
University of Belgrade, Electrical Engineering Institute 'Nikola Tesla'

emailranko.jasika@ieent.org, jovan.mrvic@ieent.org, stefan.obradovic@ieent.org
Abstract
During its operation, electrical equipment is constantly exposed to overvoltages of various waveforms, such as lightning discharges, switching operations, faults, etc. Therefore, adequate selection of overvoltage protection and equipment insulation withstand voltages are key factors in increasing system reliability. In general, insulation coordination is carried out by analyzing the insulation behavior for standard impulse and switching overvoltage waveforms. However, overvoltages that occur in operating conditions can significantly deviate from the standard waveforms of insulation withstand voltages, in terms of the front time, the duration of the wave, the existence of highfrequency components as result of reflections in the facility and other factors. This paper presents possible methods of assessing the behavior of equipment insulation for real voltage waves to which the insulation is exposed during exploitation and which deviate from standard waveforms, by analysis in the frequency domain. As there are different components in the overvoltage signal at different frequencies, which a different energy, the main goal of this paper is to analyze the insulation characteristics of a specific transformer from the point of view of the energy spectral density of the voltage wave that occurs at its terminals when an atmospheric discharge occurs. The analysis is based on the determination of the safety margin on the entire frequency spectrum of the overvoltage wave, that is, on the calculation of the so-called FDSF (Frequency Domain Severity Factor). The calculation results show that although the overvoltage amplitude is lower than the withstand voltage of the transformer insulation with an appropriate safety margin (the condition of the classic approach to insulation coordination is satisfied), the spectrum analysis of the voltage wave in the frequency domain shows that the insulation may still be compromised.
References
*** (2018) Insulation co-ordination: Part 2: Application guidelines. IEC 60071-2
*** (2013) Insulation coodination for UHV AC systems. in: CIGRE technical brochure, No.542; CIGRE WG C4.306
*** (2014) Electrical transient interaction between transformers and the power system. in: CIGRE technical brochure, No.577; CIGRE JWG A2/C4.39
*** (2005) Interaction between transformers and the power system with focus in high frequency electromagnetic transients. Brazil: Cigre - Brazilian Working Group, JWG A2/C4-03
*** (2008) Insulation co-ordination related to internal insulation of gas insulated system in SF6 and N2/SF6 mixtures under AC conditions. in: CIGRE technical brochure, No. 360; CIGRE WG C4.302
*** (2011) Insulation co-ordination: Part 1: Definitions, principles and rules. IEC 60071-1
Balaji, S.P., Krithika, G., Usa, S. (2011) Prediction od v-t characteristics of transformer insulation. in: XVII International Symposium on High Voltage Engineering, Hannover, Germany, August 22-26
Darveniza, M., Vlastos, A.E. (1988) Generalised breakdown models and the integration method for predicting non-standard waveshape impulse strengths. in: Proceedings., Second International Conference on Properties and Applications of Dielectric Materials, 1: 284-287
Krithika, G., Usa, S. (2013) Volt-time characteristics of OIP under non-standard impulses. in: International Conference on Condition Assessment Techniques in Electrical Systems
Lopez-Fernandez, Xose M., Alvarez-Marino, C. (2010) Frequency domain severity factor (FDSF): Transient voltage performance: Transformer outside/inside. in: Advanced Research Workshop on Transformers, Spain
Malewski, R., Douville, J., Lavallee, L. (1988) Measurement of switching transients in 735 kV substations and assessment of their severity for transformer insulation. IEEE Transactions on Power Delivery, 3(4): 1380-1390; October
Massaro, U.R.R., Antunes, R. (2009) Electrical transient interaction between transformers and power system: Brazilian experience. in: International Conference on Power Systems Transients (IPST2009), Kyoto-Japan, June
Okabe, S., Takami, J. (2008) Evaluation of breakdown characteristics of oil-immersed transformers under non-standard lightning impulse waveforms: Method for converting non-standard lightning impulse waveforms into standard lightning impulse waveforms. IEEE Transactions on Dielectrics and Electrical Insulation, 15(5): 1288-1296
Okabe, S., Koto, M., Kawashima, T., Ishikawa, T., Yamagiwa, T. (1999) Insulation characteristics of GIS for non-standard lightning surge waveforms: Part II: Gas gaps and spacer surface. in: Eleventh International Symposium on High Voltage Engineering, 3: 163-166
Okabe, S., Yuasa, S., Kaneko, S., Ueta, G. (2009) Evaluation of breakdown characteristics of gas insulated switchgears for non-standard lightning impulse waveforms: Method for converting non-standard lightning impulse waveforms into standard lightning impulse waveforms. IEEE Transactions on Dielectrics and Electrical Insulation, 16(1): 42-51
Sima, W., Lan, X., Yang, Q., Yuan, T. (2015) Statistical analysis on measured lightning overvoltage surges in a 110 kV air-insulated substation. IET Science, Measurement & Technology, 9(1): 28-36
Sun, P., Sima, W., Yang, M., Lan, X., Wu, J. (2015) Study on voltage-number characteristics of transformer insulation under transformer invading non-standard lightning impulses. IEEE Transactions on Dielectrics and Electrical Insulation, 22(6): 3582-3591; December
 

About

article language: Serbian
document type: Professional Paper
DOI: 10.5937/zeint32-41430
received: 28/11/2022
accepted: 05/12/2022
published in SCIndeks: 13/01/2023
peer review method: single-blind
Creative Commons License 4.0

Related records

No related records