Isolated Phase Busbars provide the permanent electrical connection between the power generator and the generator transformer and normally operate within the 3.6kV to 36kV range, with currents up to 40kA. Experience gained in a multitude of operating conditions ensure that GKW IPB meets every requirement for reliability and performance and provides a number of key factors:
- Minimum risk of phase-to-phase short circuits
- Ability to withstand high “through-fault” currents
- Sustained integrity of the dielectric medium
- Prevention of induced currents in adjacent metalwork
- Easy, safe and secure interfacing with circuit breakers and other fixed plant
The Isolated Phase Busbar design is a proven concept with a cylindrical aluminium conductor for each phase supported by insulators in both epoxy resin and porcelain within an aluminium enclosure. The conductor support systems are spring loaded to allow the conductor to expand during normal operation and to freely move radially to the magnetic centre of the IPB enclosure in the event of a fault, this preventing the insulators from being subject to potentially damaging stresses generated by the fault current. The enclosures of the three phases are bonded together at both ends with at least one end connected to the station earth. Where necessary, due to the long lengths, laminated expansion joints are utilised in the conductor and enclosure to allow for thermal expansion. The designs are fully type tested and designed to meet all up to date international standards.
GKW has carried out exhaustive evaluation of terminal connections and associated components, to both generator and the generator transformer terminals. Resulting from this work, GKW can provide cost effective terminal connections suitable for interface with all major equipment manufacturers. Matching voltage transformer cubicles, including types of transformer “on load” isolation, are routinely produced with the busbars to provide a complete and integrated system.
Design calculations for Isolated Phase Busbar systems assume that the heat generated in the conductor is dissipated by conduction and radiation, with the large diameter busducts capable of dissipating more heat than smaller busbars. The maximum temperature rise during operation at any point on the conductors does not exceeed 65oC over an ambient of 40oC at the rated current. For generators larger than 660MW GKW have type tested designs to combat the heat produced by installing complex and reliable Forced Air and Water Cooled systems. These have been developed to eliminate the complexities of some systems and ensure that the busbars operate in clean and dry conditions.