Some of the PROS for application od hybrid GIS are: where space is a constraint, the substation is to be installed below an OH T. Line, fast-track projects, site heavily polluted, or harsh climatic conditions, pre factory tested among other benefits. Cost is somehow between conventional AIS and a GIS.
The acceptability of hybrid (AIS/GIS) varies significantly for different markets around the world.
Europe & IEC marketplaces: Hybrid GIS is getting acceptance in Europe and IEC marketplace and somehow suited for a common substation configuration such as double-bus bars and other arrangements. A major advantage is the integration of a circuit breaker, CT &PT with disconnect, and grounding switches in the same module assembly allowing significant space reduction for most AIS substations arrangements.
US & ANSI/IEEE Marketplaces: However, the hybrid approach is struggling with acceptance in the US utilities and other ANSI/IEEE marketplaces. Perhaps some of the reasons are:
1) The majority of the US AIS substations use relatively compact design with a dead-tank breaker technology with an already integrated breaker with CT on the bushing good for ring-bus configuration often used in the US.
2) The HV US safety operation practice traditionally likes to see visible open disconnect switch while hybrid & GIS equipment uses the external indicator and Inspection windows for switch connection status deemed to be unacceptable by many field operators.
3) Disconnect switch manufactured per the ANSI Std has historically acceptable reliability performance. ANSI switches are much stronger than the IEC switches but occupy significant space in the yard.
4) Land cost and availability has no been a major issue for the vast majority of substations particularly for non-metropolitan substations
