When lightning struck and damaged one of the transmission lines critical for Broadcast Australia’s radio and communications tower in Far North Queensland, Zinfra mobilised a team to the remote location in five days.
The works took four months and involved the replacement of 6km of conductor across 11 transmission towers. Located 60km south of Cairns, the broadcasting transmission tower is at the top of Mount Bellenden Ker, the second highest peak in Queensland. Not only is the site remote, the rain gauge at its summit records an annual average rainfall of 8312mm, making it the wettest meteorological station in Australia.
The broadcasting facility at the top of Mt Bellenden Ker receives power via an existing overhead high voltage transmission line. The overhead line is located on the eastern face of the mountain, running from the Ergon Energy HV network connection point at the bottom station to the transmission facility located at the top station.
The 22kV HV transmission line is approximately 6km in length and consists of overhead conductors supported on a series of steel H-frame towers. The line consists of the original conductors and insulators installed in the early 1970s, but the support towers were replaced in 1997 due to heavy corrosion. The facilities at the summit are serviced by a privately owned cable car, which runs almost parallel with the 22kV line and/or via a walking track.
Given the tropical and wet conditions at Mount Bellenden Ker, the transmission line is vulnerable to the effects of the environment and accelerated decay.
Broadcast Australia required inspection of the tower structures to establish trends in structural decay and to determine the extent of structural upgrade required.
Zinfra was engaged to inspect the upper part of each tower within 4m of the insulator attachment height. Replacement of structural pins, bolts, corroded items and the installation of corrosion control measures made up this portion of the works.
Re-conductoring of existing overhead structures
Zinfra undertook refurbishment, replacement, installation and testing of the conductors, surge arrestors and insulators on the H frame towers. In addition, Zinfra supplied and installed a new earthing system to each structure tower.
Access, or lack thereof
The broadcasting facility is located about 60km south of Cairns, on top of a mountain, in the remote reaches of Far North Queensland. Once on the mountain, access to the towers is only via the private cable car and by foot through dense rainforest. The crew was required to carry in all their tools, equipment and supplies to complete the job.
Rain, rain and more rain
Wild weather was a hallmark of this project. Wind, rain and poor visibility made this work particularly difficult and excluded the use of helicopters for conductor stringing.
Minimising disruption to all Broadcast Australia customer services was a priority, so Zinfra was required to undertake some of the works in limited five-hour windows. Planning, resourcing and timing were critical factors to deliver under these circumstances.