275KV SWITCHING STATION

Each phase of the 275kV double bus is 200 metres long and rated 6000amps at a maximum continuous operating temperature of 90ºC.

The Powerlink Queensland Greenbank 275kV switching station located on the outskirts of Brisbane has been a high profile project in Queensland. In February 2005, Powerlink placed an order with United Group Infrastructure to design, construct and commission the Greenbank Switching Station. This augmentation of the Powerlink high voltage transmission network is required to be completed by October 2006

Each phase of the 275kV double bus is 200 metres long and rated 6000amps at a maximum continuous operating temperature of 90ºC. At design stage, United Group Infrastructure considered several alternatives for the heavy current busbar, but settled on thick wall aluminium tubular section as being the best cost/benefit option. United Group Infrastructure’s decision typifies the trend towards larger bus sizes with greater spans between supports, and
is a similar approach to the way stations are being constructed in Victoria, and now, South Australia.

FACTORY PREFABRICATED BUS SYSTEM
At Greenbank, six line bay diameters are fully constructed, and provision has been made for future addition of transformers and additional line bay diameters. Using an Electropar supplied 200mm x 10mm WT aluminium alloy factory prefabricated bus system to minimise welding and fabrication at site, United Group Infrastructure are close to completion of the project, and commissioning the site will begin shortly thereafter.

CUSTOM ENGINEERED BUS SUPPORTS
The buswork was delivered in two open-top 40-foot containers maximising the busbar lengths available for shipment, while placing the welded busbar splices at the point within spans between insulators where mechanical stress was lowest. All weld preparation, fitment of damping conductor and fitment of bus welded splices was completed in Electropar’s Auckland plant before the system was shipped to the Greenbank site. One interesting aspect of the mechanical design of the busbar system was that bus supports were custom engineered to match the 12.5kN strength rating of the 275kV station post insulators.

Particular attention was paid to Quality Assurance for the Greenbank bus system both in terms of chemical/mechanical properties of the alloy and with the Aluminium welding needing to be in accordance with AS 1665.

Trevor Pieterse, Operations Manager for United Group Infrastructure in Queensland, says that “Electropar met all our expectations and delivered an excellent product which complemented the rest of the project.”