Power Generators of high KVA rating especially that of hydropower plant are very much prone to the ground faults. Stator ground faults are the most common winding failure in generators. During stator ground faults, short circuit currents flow from the damaged phase to ground through the stator core. Experience has shown that stator ground fault damages are proportional to phase-to-ground fault current as well as fault duration. For that reason, Generator Neutral Grounding must be appliedin order to;
Limit phase-to-ground fault current.
Provide a means of stator ground fault detection.
There are various generator grounding classes and types available. In this paper, high-resistance grounding has been chosen. High-resistance generator neutral grounding scheme based on a grounding transformer with a secondary resistor. The advantage of the distribution transformer resistor combination is that the resistor used in the secondary is of comparatively low ohmic value and of rugged construction as compared to obtaining the same result by installing a high-ohmic, low-current resistor directly in the generator neutral. This research introduces some important and applicable practices which came from few years of practical as well as theoretical studies and discussions with some national and international power system experts. The research was made on the hydro power plants installed at Tarbela generating unit. The important parameters concerning the high impedance grounding of the generator were calculated. These results will be a kind of ready references for neutral grounding transformer design calculations and analysis.
Muhammad Bais Abdul Basit Said Ali Muhammad Sadiq and Israr Ahmad Design and Analysis of Neutral Grounding Transformer for Hydro Alternators International Journal of Engineering Works Vol. 6 Issue 10 PP. 374-378 October 2019
[1] M. Gilany, O. Malik and A. Megahed, "Generator stator winding protection with 100% enhanced sensitivity", International Journal of Electrical Power & Energy Systems, vol. 24, no. 2, pp. 167-172, 2002. Available: 10.1016/s0142-0615(01)00018-7.
[2] B. Ravindranath and M. Chander, Power system protection and switchgear. New Delhi: New Age International, 2011.
[3] D. Reimert, Protective relaying for power generation systems. 2017.
[4] Y. Hase and Y. Hase, Handbook of power systems engineering with power electronics applications. Hoboken, NJ: John Wiley, 2013.
[5] The 10th IET International Conference on Development in Power Systems Protection (DPSP 2010). [Stevenage, Hertfordshire]: Institution of Engineering and Technology, 2010.
[6] L. Hewitson, M. Brown and B. Ramesh, Practical power systems protection. Amsterdam: Elsevier, 2008.
[7] S. Horowitz and A. Phadke, Power system relaying. Chichester, England: Wiley/Research Studies Press, 2008.
[8] M. Kezunovic, J. Ren and S. Lotfifard, Design, modeling and evaluation of protective relays for power systems. 2015.
[9] J. Martínez-Velasco, Transient analysis of power systems. Chichester: Wiley, 2015.
[10] Y. Paithankar, Fundamentals of power system protection. Delhi: PHI Learning Private Limited, 2014.
[11] W. Rebizant, J. Szafran and A. Wiszniewski, Digital signal processing in power system protection and control. London: Springer, 2011.
[12] L. Singh, Advanced power system analysis and dynamics. New Dehli: New Age International (P) Ltd., 2007.
