Abstract
This paper describes current and voltage instrument transformer connections that are not physically conventionally connected as portrayed in ANSI Standards and Guides or relay manufacturers' literature. A three-line diagram of a basic conventional current transformer connection for a two winding delta wye power transformer differential relaying is presented. Then, we present scenarios of (1) one set of CT's being reversed or 'rolled out', then (2) the other set reversed and, finally, (3) both sets rolled out from the conventional connection with proper connection of the unconventional connected CT's. Also, the effect of reversed voltage transformer connections on directional overcurrent and directional power are presented. An example of how symmetrical component metering screens of a numeric relay were used to diagnose an incorrect voltage transformer connection is also presented. This paper is a primer on analyzing unconventional instrument transformer polarity connections and how to obtain the right connection to achieve the desired direction of operation or polarity as indicated in protective relay manufacturers' literature.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
