The Gas Insulated Switchgear (GIS)

·         The Gas Insulated Switchgear (GIS) shall be a complete unit comprised of main equipment, all control, monitoring, protection, measuring and auxiliary devices and systems including interconnections, all termination

·         Joints at interfaces, mechanical linkages, couplings, SF6 gas piping, cabling, wiring, grounding materials etc. required for proper and satisfactory operation.
·         The GIS shall be of compact and modular design with individual equipment modules connected together to form a complete assembly. However, combined disconnect switch and grounding switch, cable termination, PT, exit bus duct and CT (with cores located within gas compartment) shall be in separate gas tight compartment. If, CT is installed in breaker gas compartment; insulation class for CT shall be class F. of either single-phase enclosure type or three-phase enclosure type for voltage levels of 230kV and below. of single-phase enclosure type for voltage level of 380kV. Installed on suitable pads or supporting frames/structures with provision for leveling, including fasteners to foundation, which shall also be included in the supply. Support-structures shall be designed and fabricated to withstand the short circuit forces of the ground fault current.
·         GIS shall having expansion joints and flexible connections, where several enclosures are connected in the longitudinal direction, such as main bus. Expansion joints provided for installation alignment shall be locked in place when alignment is complete. Expansion joints for compensation of thermal expansion and erection tolerances shall have
·         the means to preserve mechanical integrity of the enclosure and the plug-in contacts for the conductor. Provided with galleries, stairways, movable platform or walkways for accessing the equipment above two meters for maintenance and operation.
·          All structures, movable platform, galleries, stairways and walkways shall have grounding provision and shall conform to the relevant Occupational Safety and Health Administration (OSHA) regulations.
·         For single-phase type GIS, creation of single gas zone by external piping connection between the phases is not acceptable. Also, external piping connection (with normally open valve) to create common gas zone (between same phase) in single-phase type GIS is not acceptable.
·         The GIS enclosure shall be safe to touch and fully ensure operational security and personnel safety under all normal and fault conditions with the maximum allowed induced voltage in the enclosure of 65 volts.
·         The switchgear and all its components and accessories shall be designed for minimum maintenance during service. The manufacturer shall state the minimum interval between minor inspections (which will be restricted to visual checking and adjustments of external parts only) and major inspection/overhaul, including refilling or replenishment of gas and cleaning of the contaminant or filter in the circuit breaker chamber(s).
·         Suitable openings shall be provided in the circuit breaker, disconnect and grounding switch modules for major inspection/adjustments.
·         All motors shall be in accordance with IEC 60034. The bearings and other such parts shall be permanently lubricated for the entire service life. Padlocks shall be made of stainless steel or brass.
The GIS interface points shall be carefully coordinated with other equipment such as overhead lines, cables, transformers, reactors, capacitor banks, etc., supplied by other manufacturers in order to ensure full compatibility. The design criteria for outdoor