Modern Instrument Transformer Technologies for UHV AC and HVDC Networks

This paper presents Non-conventional Instrument Transformers (NCIT) being suitable for current and voltage metering as well as protection applications. The NCITs are providing a modern digital secondary interface. They are using the optical technology to realize a galvanic separation as well as their intrinsic advantages for reasons of electromagnetic compatibility by their dielectric insulation properties. With the standardization of the IEC61850 protocol a widely accepted and by most of the manufacturers supported secondary interface is now available. Examples of some practical applications are used to present this modern solution.