New non-conventional instrument transformer (NCIT) - a future technology in gas insulated switchgear

Different solutions for non-conventional instrument transformers have been developed in the last decade and are now available for HV gas insulated switchgear. Manufacturers have integrated Rogowski coil into high voltage GIS for current measurement and capacitive principle for voltage measurement. These concepts were realized in different types of products such as RC voltage dividers, external Rogowski coils in electronic current transformers (eCT), etc. Special electronic units for preprocessing and merging of sampled measured values have been developed to convert the outputs (low power or optical) to the standard IEC 61850-9-2- for each NCIT technology. This ensures the compatibility as well as interoperability of any protection device with the appropriate digital interface. Installed NCIT technology will provide many benefits for utilities and manufacturers, including reduction of SF6 insulation gas (environmental benefit), simplified wiring, and efficiency in manufacturing and engineering. Additional technical benefits include seamless-unified measurement and higher accuracy. The paper describes NCIT technologies, integration in high voltage gas insulated switchgear, benefits and qualification processes with customer/utilities, which lead to reliably and accepted products.