NorPower were Principal Contractor on the refurbishment of approximately 7 km of the 132kV DC PL16 based design Dunoon-Whistlefield overhead line. The works were required due to the condition of the existing earthwire being poor, steelwork galvanising deterioration and the line experiencing repeated ‘trips’ which was thought to relate to the condition of the existing insulator sets and varying arc gaps.
Under double circuit outage a total of 29 towers were re-insulated and the earthwire replaced on a ‘like for like’ basis with 60 mm2 SKUNK ACSR. Under the same refurbishment scheme a total of 31 towers, including the 360 foot (111 m) high tower at the Loch Long crossing, were re-painted under single circuit outage. Other associated works, such as muff replacement, were carried out on an as required basis.
This line passes over very arduous terrain, with some of the structures in very isolated locations which, following risk assessment, led to a helicopter being utilised to transport not just materials but also personnel to those most isolated areas. The use of helicopter substantially reduced the safety risks associated with personnel walking to and from work sites, thereby also reducing the overall project programme to less than 3 months.