Cahier technique no 195 - Schneider Electric

Current transformers:specification errors and solutionsAfter a reminder of current transformers (CTs), the author highlights theerrors most often encountered when defining current transformers, anessential and little known link between the electrical network and theprotection relays.It explains how to find a way out of difficult situations: CTs that cannot bemanufactured, delays, additional costs, malfunctions, etc.This Cahier Technique should be useful for electricians designinginstallations, for protection specialists, panel builders and all CTmanufacturers. It is in the best interest of all to exchange all informationrequired for the safety and optimisation of CTs.This Cahier Technique is an operational addition to Cahier Techniqueno. 194 “Current Transformers: how to specify them”.Contents1 Specifying current transformers 1.1 Introduction p. 4properly1.2 Reminder of CTs p. 42 Examples of specification errors 2.1 Optimisation and safety p. 72.2 When CTs do not seem to be suitable… p. 82.3 The most frequent errors p. 92.4 And if the CT cannot be manufactured? p. 123 Equivalence of the various possible 3.1 How to move from P n1 -5Pk 1 to P n2 -5Pk 2 p. 15definitions of the same CT3.2 How to move from P n1 -5Pk 1 to P n2 -10Pk 2 p. 153.3 What is the V k of a CT: P n -XPk p. 163.4 How to move from class X (V k , R ct ) p. 16to a class 5P: P n -5Pk4 Conclusion p. 175 Bibliography p. 18Cahier Technique Schneider Electric no. 195 / p.3