High voltage busbar trunking system is a type-tested switchgear and control gear assembly in the form of an enclosed system. HV bus bar system is used for transporting power between HV Generators, transformers and the infeed main switchgear of the main HV switchgear.Generally three types of bus ducts namely non segregated, segregated and isolated phase bus duct shall be used.

Non-segregated bus ducts:

The non-segregated bus ducts consists of three phase busbars running in a common enclosure made of steel or aluminium. The enclosure shall provide safety for the operational personnel and reduces chances of faults. The enclosures shall be effectively grounded.

Segregated bus ducts:

Segregated phase bus duct are similar to non segregated phased duct except that metal or insolation barriers are provided between phase conductors to reduce chances of phase to phase faults. However, it is preferable to use metal barriers.

Isolated bus ducts:

In the case of isolated bus ducts, each phase conductor shall be housed in a separate non-magnetic enclosures.

The bus duct shall be made of sections which are assembled together at site to make complete assembly. The enclosure shall be of either round or square shape and welded construction. The enclosures of all phases in general to be supported on a common steel structure. Provision of fire protection shall be provided in all openings in accordance with Part 4 ‘Fire and Life Safety’. Fire separation in openings shall be provided using materials having 2h fire resistance rating.