Forward(This introduction is not part of IEEE Std C37.110-1996@ IEEE Guide for the Application of Current Transformers Used for Protective Relaying Purposes). This guide was prepared by the Guide for the Application of Current Transformers for Relaying Working Group of the Relay Inputs Sources Subcommittee of the IEEE Power System Relaying Committee. The guide is intended to assist relay engineers in understanding the operation of current transformers and their selection and application to specific relay protection schemes. At the time this guide was approved@ the working group membership was as follows: M. W. Conroy @ Chair B. D. Nelson @ Vice Chair B. Bozoki J. W Chadwick@ Jr. G. K. Clough P. R. Drum L. L. Dvorak I. O. Hasenwinkle J. D. Huddleston@ III W. C. Kotheimer J. R. Linders M. J. McDonald G. P. Moskos C. C. Parr R. Ryan E. Sage D. W. Smaha K. A. Stephan J. Stephens J. T. Uchiyama S. E. Zocholl The following persons were on the balloting committee: Mark Adamiak John Appleyard E. A. Baumgartner Barbara L. Beckwith R. W. Beckwith G. Benmouyal David C. Blackburn@ Jr. John Boyle B. Bozoki James A. Bright J. Burnworth H. J. Calhoun Carlos H. Castro Thomas W. Cease John W. Chadwick@ Jr. S. R. Chano Graham Clough Stephen P. Conrad Mark W. Conroy Carey J. Cook Albert N. Darlington Douglas C. Dawson R. W. Dempsey C. L. Downs Paul R. Drum Lavern L. Dvorak Walt Elmore A. Elneweihi J. Esztergalyos H. G. Farley E. C. Fennell C. W. Fromen Jonathan D. Gardell Jeffrey Gilbert A. T. Giuliante S. E. Grier Edward M. Gulachenski E. A. Guro R. W. Haas R. E. Hart Irwin Hasenwinkle C. F. Henville J. W. Hohn J. D. Huddleston@ III J. W. Ingleson J. A. Jodice Edward W. Kalkstein Mladen Kezunovic K. J. Khunkhun W. C. Kotheimer P. A. Kotos John R. Linders W. J. Marsh@ Jr. J. E. McConnell M. J. McDonald J. L. McElray M. Meisinger William M. Mello R. J. Moran Charles J. Mozina K. K. Mustaphi George R. Nail B. D. Nelson C. C. Parr Robert D. Pettigrew Arun G. Phadke Alan C. Pierce John M. Postforoosh M. S. Sachdev Evan T. Sage Miriam P. Sanders James E. Stephens W. M. Strang M. J. Swanson Richard P. Taylor James Teague John T. Tengdin James S. Thorp Demetrios A. Tziouvaras Joe T. Uchiyama E. A. Udren Vid Varneckas Charles L. Wagner William P. Waudby Thomas E. Wiedman P. B. Winston K. Zimmerman J. A. Zipp Stan Zocholl John A. Zulaski When the IEEE Standards Board approved this standard on 18 April 1996@ it had the following membership: Donald C. Loughry @ Chair Richard J. Holleman @ Vice Chair Andrew G. Salem @ Secretary Gilles A. Baril Clyde R. Camp Joseph A. Cannatelli Stephen L. Diamond Harold E. Epstein Donald C. Fleckenstein Jay Forster* Donald N. Heirman Ben C. Johnson E. G. Al Kiener Joseph L. Koepfinger* Stephen R. Lambert Lawrence V. McCall L. Bruce McClung Marco W. Migliaro Mary Lou Padgett John W. Pope Jose R. Ramos Arthur K. Reilly Ronald H. Reimer Gary S. Robinson Ingo Rusch John S. Ryan Chee Kiow Tan Leonard L. Tripp Howard L. Wolfman *Member Emeritus Also included are the following nonvoting IEEE Standards Board liaisons: Satish K. Aggarwal Alan H. Cookson Chester C. Taylor Rochelle L. Stern IEEE Standards Project EditorScopeThis standard describes the characteristics and classification of current transformers (cts) used for protective relaying. It also describes the conditions that cause the ct output to be distorted and the effects on relaying systems of this distortion. The selection and application of cts for the more common protection schemes are also addressed.