Non-conventional instrument transformers enabling digital substations for future grid

Non-conventional instrument transformers (NCIT) have now reached a level of maturity and performance that enables implementation of fully digital current measurement in high-voltage substations. State-of-art fiber optical current sensor (FOCS) solutions are presented together with Rogowski coil and electronic voltage transformer (EVT) in innovative solutions that deliver significant operational performance, environmental, safety and substation engineering benefits supporting future smart grid substation investments. Conventional HV instrument transformer using iron cores and analogue outputs have performance limitations in adapting to digital process bus substations that NCIT solutions can inherently avoid. Applications such as integrating DCB with FOCS, stand-alone FOCS and other non-conventional instrument transformer solutions for GIS substation based on using ECT (Rogowski coil) and EVT as well as aspecial application for using FOCS for Pump-storage Water-plant (PSW) are described in this paper.