Jelisaveta KRSTIVOJEVIC, Milenko DJURIC

A new algorithm for avoiding maloperation of transformer restricted earth fault protection caused by the transformer magnetizing inrush current and current transformer saturation

Owing to current transformer (CT) saturation caused by a decaying direct current component in the magnetizing inrush current, the restricted earth fault (REF) protection of a power transformer could maloperate during magnetizing inrush. This paper presents a new transformer restricted earth fault relay algorithm that can prevent false relay tripping and provide proper action during the energization of a faulty transformer. The integral of the product of the signals that are compared is calculated over 1 half-period of the signals. The performance of the proposed algorithm is tested and verified using a large number of transformer energization trials and fault cases. The signals required for testing of the algorithm were obtained by laboratory measurements, and then the algorithm was tested off-line. The influence of different levels of CT saturation due to different remanent fluxes in CT cores during power transformer energization was investigated. By applying computer simulations, the signals required for algorithm testing were generated. The investigation results presented in this paper show that the new algorithm provided sensitive protection for the power transformer for phase to ground faults and high security and stability during magnetizing inrush conditions in conjunction with CT saturation.

PDF

___

[1] Sezi T. A new approach for transformer ground differential protection. In: Industrial and Commercial Power Systems Technical Conference; 1116 Apr 1999; New Orleans, LA, USA. New York, NY, USA: IEEE. pp. 394-399.
[2] IEEE Standard C37.91. IEEE Guide for Protective Relay Applications to Power Transformers. New York, NY, USA: IEEE, 2008.
[3] Cosse RE, Nichols WH. The practice of ground differential relaying. IEEE T Ind Appl 1994; 30: 1472-1479.
[4] Stringer D. Ground differential protection: revisited. In: Industrial and Commercial Power Systems Technical Conference; 26 May 1999; Sparks, NV, USA: IEEE. pp. 1-8.
[5] Sutherland PE. Application of transformer ground differential protection relays. IEEE T Ind Appl 2000; 36: 16-21.
[6] Rockefeller GD. Fault protection with a digital computer. IEEE T Power Ap Syst 1969; 88: 438-464.
[7] Youssef OAS. A wavelet-based technique for discrimination between faults and magnetizing inrush currents in transformers. IEEE T Power Deliver 2003; 18: 170-176.
[8] Saleh SA, Rahman MA. Modeling and protection of a three-phase transformer using wavelet packet transform. IEEE T Power Deliver 2005; 20: 1273-1282.
[9] Ozgonenel O, Onbilgin G, Kocaman C. Transformer protection using the wavelet transform. Turk J Elec Eng & Comp Sci 2005; 13: 119-135.
[10] Pihler J, Grcar B, Dolinar D. Improved operation of power transformer protection using artificial neural network. IEEE T Power Deliver 1997; 12: 1128-1136.
[11] Tripathy M. Power transformer differential protection using neural network principal component analysis and radial basis function neural network. Simul Model Pract Th 2010; 18: 600-611.
[12] Perez LG, Flechsig AJ, Meador JL, Obradovic Z. Training an artificial neural network to discriminate between magnetizing inrush and internal faults. IEEE T Power Deliver 1994; 9: 434-441.
[13] Kılı¸c E, Ozg¨onenel O, Usta ¨ O, Thomas D. PCA based protection algorithm for transformer internal faults. Turk J ¨ Elec Eng & Comp Sci 2009; 17: 125142.
[14] Khorashadi-Zadeh H, Li Z. A sensitive ANN based differential relay for transformer protection with security against CT saturation and tap changer operation. Turk J Elec Eng & Comp Sci 2007; 15: 351-368.
[15] Wiszniewski A, Kasztenny B. A multi-criteria differential transformer relay based on fuzzy logic. IEEE T Power Deliver 1995; 10: 1786-1792.
[16] Shin MC, Park CW, Kim JH. Fuzzy logic-based relaying for large power transformer protection. IEEE T Power Deliver 2003; 18: 718-724.
[17] Ashrafian A, Rostami M, Gharehpetian GB. Characterization of internal disturbances and external faults in transformers using an S-transformbased algorithm. Turk J Elec Eng & Comp Sci 2013; 21: 330-349.
[18] Jia S, Wang S, Zheng G. A new approach to identify inrush current based on generalized S-transform. In: International Conference on Electrical Machines and Systems; 1720 Oct 2008; Wuhan, China. New York, NY, USA: IEEE. pp. 4317-4322.
[19] Guzm´an A, Zocholl S, Benmouyal G, Altuve H. A current-based solution for transformer differential protection Part I: Problem statement. IEEE T Power Deliver 2001; 16: 485-491.
[20] Rahman MA, Jeyasurya B. A state-of-the-art review of transformer protection algorithms. IEEE T Power Deliver 1988; 3: 534-544.
[21] Sharp RL, Glassburn WE. A transformer differential relay with second-harmonic restraint. IEEE T Power Ap Syst 1958; 77: 913-918.
[22] IEEE Power Engineering Society. Transient response of current transformers. IEEE T Power Ap Syst 1977; 96: 1809-1814.
[23] IEEE Standard C37.110. IEEE Guide for the Application of Current Transformers Used for Protective Relaying Purposes. New York, NY, USA: IEEE, 2008.
[24] Wentz EC, Sonnemann WK. Current transformers and relays for high-speed differential protection, with particular reference to offset transient currents. Electr Eng 1940; 59: 481-488.
[25] Guzm´an A, Altuve HJ, Benmouyal G. Power Transformer Protection. In: James H. Harlow, editor. Electric Power Transformer Engineering. Boca Raton, FL, USA: CRC Press, 2004. pp. 353-381.
[26] Hunt R. Impact of CT errors on protective relays case studies and analysis. IEEE T Ind Appl 2011; 48: 52-61.
[27] Labuschagne C, Merwe IV, Enterprises E. A comparison between high-impedance and low-impedance restricted earth-fault transformer protection. Tech Pap Schweitzer Eng Labs 2007; 1: 1-9.
[28] Kasztenny B. Impact of transformer inrush currents on sensitive protection functions How to configure adjacent relays to avoid nuisance tripping. In: 59th Annual Conference for Protective Relay Engineers; 46 April 2006, College Station, TX, USA. New York, NY, USA: IEEE. pp. 103-123.
[29] Krstivojevic J, Djuri´c M. A new method of improving transformer restricted earth fault protection. Adv Electr Comput En 2014; 14: 41-48.
[30] Davarpanah M, Sanaye-Pasand M, Iravani R. Performance enhancement of the transformer restricted earth fault relay. IEEE T Power Deliver 2013; 28: 467-474.
[31] Stojanovi´c Z, Djuri´c M. The algorithm for directional element without dead tripping zone based on digital phase comparator. Electr Pow Syst Res 2011; 81: 377-383.
[32] Elmore W. Protective Relaying Theory and Applications. 2nd ed. Boca Raton, FL, USA: CRC Press, 2004.
[33] Liu P, Malik OP, Chen D; Hope GS, Guo Y. Improved operation of differential protection of power transformers for internal faults. IEEE T Power Deliver 1992; 7: 1912-1919.
[34] Zubi´c S, Djuri´c M. A distance relay algorithm based on the phase comparison principle. Electr Pow Syst Res 2012; 92: 20-28.
[35] Stojanovi´c Z, Djuri´c M. An algorithm for directional earth-fault relay with no voltage inputs. Electr Pow Syst Res 2013; 96: 144-149.
[36] Brunke JH, Fr¨ohlich KJ. Elimination of transformer inrush currents by controlled switching Part I: Theoretical considerations. IEEE T Power Deliver 2001; 16: 276-280.
[37] Duro MM, Denis R. Parameter uncertainty assessment in the calculation of the overvoltages due to transformer energization in resonant networks. In: CIGRE 2012; 2631 Aug 2012; Paris, France. CIGRE 2012: C4-204. pp. 1-12.