Emerging Technologies in High Voltage Gas Insulated Switchgear-Clean Air GIS and NCIT

Presently, the Gas insulated switchgears (GIS) are used extensively in the power transmission and distribution systems worldwide. The compactness and durability of Gas insulated switchgear is the key reason for their popularity. The compactness is mainly because of presence of SF6 gas, having the best characteristics as an insulating and quenching medium. SF6 gas, though provides a good insulation resistance, it is also considered harmful to the environment because of its greenhouse effect. Though it is not a major contributor to global warming, it has got long term footprints on the environment. Thus, it has become a necessity to have a solution which protects environment and provides resource efficiency without comprising the operational benefits. Clean air & vacuum technologies in high voltage switchgears have been developed in recent times as an alternative to the existing SF6 technology. This provides a completely environmental friendly solution. Secondly, there is a recent trend of digitalization globally. Power systems and substations are assimilating this technology rapidly. Taking into consideration the above requirement Non Conventional Instrument Transformer (NCIT) emerges as a promising & potential solution. The new proposed NCIT provides an advantage over the conventional instrument transformer as it has less copper cabling and thus a door opener to digital substations having better measurement functionality for metering and protection. Special electronic units for preprocessing and merging of sample values are introduced to convert the outputs (low power or optical) to the compiled standard IEC 61850-9-2-LE.