Overcurrent and earth fault protective equipment employing time grading and directional detection cannot provide correct discrimination on all power networks and in many cases clearing times for some faults would not be acceptable. Differential protection is an alternative overcurrent protective scheme, which is used to protect individual sections of networks or pieces of equipment, such as transformers, generators, e.t.c. Thus, where protection co-ordination is difficult using time delayed over current and earth fault protection, or where fast fault clearance is critical, then differential protection may be used. Kirchhoff’s first law, which states that the sum of the currents flowing to a node must be equal to the sum of the currents flowing out from it is the basic principle of the differential protection scheme. It detects the difference between the current entering a section and that leaving it. Under normal operating conditions, the current leaving the protected unit would be equal to that entering it at every instant. If the current flowing into the protected unit is the same as the current leaving, then the fault is not in the protected unit and the protective equipment or relay should not operate. If there is a difference in either the phase or magnitude between input and output, then the fault is in the protected unit and the protection should operate. This paper investigates how power transformers can be protected using the current-differential protection schemes.
T. Davies, Protection of Industrial Power Systems, Oxford: Newnes, 2001, pp 126-138.
IEEE, “IEEE guide for protecting power transformers,” IEEE Standard C37, 91, 2008.
IEEE, “IEEE guide for automatic reclosing of line circuit-breakers for AC distribution and transmission line,” IEEE Standard C37, 104, 2002.
C. Christopoulos, A. Wright, “Electrical Power System Protection”, Kluwer Academic Publishers, the Netherlands, 1999, pp 107-134.
G. Rockefeller, Transformer Protection Application Guide, Basler Electric, 2007, pp 12-14.
J.A. Kay, and L. Kumpulainen, “Maximizing Protection by minimizing arcing times in medium-voltage systems,” IEEE Trans. Ind. Appl., vol. 49, No. 4, pp.1920-1927, July-August, 2013.
AREVA T&D, Network Protection and Automation Guide (NPAG), AREVA T&D, Stafford UK, Chaps. 2, 9, 14, 23, 2011.
V. Rozine, and M. H. Adams, “Protective Device Problems and Solutions,” Proc. International Power and Energy Conference (IPEC) pp. 789-794, Singapore, 27-29 October 2010.
M. Mitolo, and M. Tartaglia, “IEEE Trans. Ind. Appl., Vol. 48, No. 1, pp. 211-217, January-February 2012
M.J. Slabbert, S.J. van Zyl, R. Naidoo, and R.C. Bansal, “Evaluating Phase Over-Current Protection Philosophies for Medium-Voltage Feeders Applying Let-through Energy and Voltage Dip Minimization,” Electric Power Components and Systems, Vol. 44 (2016), No. 2, pp. 206-218.
Dev Paul, “Failure Analysis of Dry-Type Power Transformer,” IEEE Transactions on Industry Applications, vol. 37, No. 3, May/June 2001, pp. 689-695.
M. T. Bishop, S. R. Mendis, J. F. Witte, K. L. Leis, “Considerations in the Selection of Primary Overcurrent Protection for Three-phase Transformers,” IEEE Transactions on Industry Applications, vol. 38, No. 3, May/June 2002, pp. 87-93.
E. R. Detjen, K. R. Shah, “Grounding Transformer Applications and Associated Protection Schemes,” IEEE Transactions on Industry Applications, vol. 28, No. 4, July/August 1992, pp. 788-796.
Yoke-Lin tan, “Damage of a Distribution Transformer Due To Through-Fault Currents: An Electrical Forensics Viewpoint,” IEEE Transactions on Industry Applications, vol. 38, No. 1, January/February 2002, pp. 29-33.
J. L. Blackburn and T. J. Domin, Protective Relaying Principles and Applications, 3rd Edition.
B. M. Weedy, Electric Power Systems, Second Edition, John Wiley& Sons, 1975, pp. 447-452.
http://electrical engineering-portal.com, Protective Relay.
AREVA T & D, U.K, Energy Automation & Information, pp. 10-13.
C. A. Gross, Power System Analysis, John Wiley & Sons, 1979, pp. 334-340
IEEE Std. C37.91-2000, IEEE Guide for Protective Relay Applications to Power Transformers.
ALSTOM, Publication & Commissioning Manuals, ALSTOM LTD. Chennai, India, chap. 2, pp. 8-12, 1999.
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