Study on the Unusual Misoperation of Differential Protection During Transformer Energization and its Countermeasure

The differential protection of the transformer, generator, or transmission line under normal operating conditions may misoperate when the adjacent transformer is switched-on. To research the cause of the misoperations, impacting factors, such as magnetizing inrush, sympathetic inrush, and current-transformer saturation are analyzed based on the field-recorded fault data and the simulation results in this paper. It is disclosed that the CT transient or CT local transient saturation, which are caused by the long-lasting dc component from the magnetizing inrush current, will lead to misoperation. To solve this problem, a new CT saturation detection algorithm based on the dc component in secondary current is proposed to prevent this sort of misoperation, and the effectiveness of the proposed algorithm is proved by the field-recorded fault data and simulation results obtained under different conditions.

[1]  D. Jiles,et al.  Theory of ferromagnetic hysteresis (invited) , 1984 .

[2]  Randy Hamilton,et al.  Analysis of transformer inrush current and comparison of harmonic restraint methods in transformer protection , 2012, 2012 Petroleum and Chemical Industry Conference (PCIC).

[3]  Xiangning Lin,et al.  Analysis of Electromagnetic Transient and Adaptability of Second-Harmonic Restraint Based Differential Protection of UHV Power Transformer , 2010, IEEE Transactions on Power Delivery.

[4]  S. F. Huang,et al.  A New Algorithm to Avoid Maloperation of Transformer Differential Protection in Substations With an Inner Bridge Connection , 2012, IEEE Transactions on Power Delivery.

[5]  Xiangning Lin,et al.  Studies on the Operation Behavior of Differential Protection During a Loaded Transformer Energization , 2007, IEEE Transactions on Power Delivery.

[6]  C. D. Hayward.  Prolonged inrush currents with parallel transformers affect differential relaying , 1941, Electrical Engineering.

[7]  M. S. Sachdev,et al.  Online identification of magnetizing inrush and internal faults in three-phase transformers , 1992 .

[8]  L. F. Kennedy,et al.  Harmonic-current-restrained relays for differential protection , 1938, Electrical Engineering.

[9]  Zhiqian Bo,et al.  Analysis of a Sort of Unusual Mal-Operation of Transformer Differential Protection Due to Removal of External Fault , 2008, IEEE Transactions on Power Delivery.

[10]  H. J. Altuve,et al.  A Current-Based Solution for Transformer Differential Protection Part II: Relay Description and Evaluation , 2002, IEEE Power Engineering Review.

[11]  Mladen Kezunovic,et al.  Mathematical models for current, voltage, and coupling capacitor voltage transformers , 2000 .

[12]  R. Yacamini,et al.  Phenomenon of sympathetic interaction between transformers caused by inrush transients , 1995 .

[13]  M. Suzuki,et al.  Digital protection method for power transformers based on an equivalent circuit composed of inverse inductance , 1988 .

[14]  Xj Electric,et al.  Analysis on Mal-operation of Differential Protection Caused by Sympathetic Inrush , 2007 .

[15]  B. Kasztenny,et al.  Generator protection and ct saturation problems and solutions , 2005 .

[16]  Liu Wan-shun.  A New Algorithm Based on Time Differential Method to Identify Sympathetic Inrush of Transformers Connected in Wye-delta Mode , 2007 .

[17]  D. Jiles,et al.  Theory of ferromagnetic hysteresis , 1986 .

[18]  R. Yacamini,et al.  Harmonic analysis of transient currents during sympathetic interaction , 1996 .

[19]  W. E. Glassburn,et al.  A Transformer Differential Relay with Second-Harmonic Restraint , 1958, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[20]  Li De-jia,et al.  Physical Mechanism of Sympathetic Inrush of Transformer and Its Influence on Differential Protection , 2005 .