In November 1994, a Klohn Crippen Berger joint venture was awarded the contract to carry out a feasibility study and to provide comprehensive engineering services and environmental evaluations for proposed hydroelectric power generation facilities on the Lower Larona River in Sulawesi, Indonesia. The new plants supplements power from thermal and diesel stations and an existing hydroelectric station on the Upper Larona River. Together, the existing and proposed power plants providepower for P.T. Inco’s Expansion Project at their nickel laterite processing facility near Soroako on the island of Sulawesi, Indonesia.
Options for partial (137 MW) and full development (212 MW) of the Lower Larona River were studied and a decision was made to first develop the hydro potential of the Lower Larona River at a dam site upstream of the village of Balambano. An important design issue for the proposed Balambano plant was the requirement to respond rapidly to the extreme load and frequency swings in the P.T. Inco generating system resulting from normal operation of the arc furnaces used in the nickel processing operation.
Subsequent to power system modeling and other engineering analyses, the design of the Balambano facility to achieve a rapid, yet stable response to the delivery of power under highly variable demand conditions was accomplished using a design that minimized flow velocities, utilized short power conduits with rapid water starting times and incorporated high inertia generators with long mechanical start times. To supply 20 kV power for the construction of the 2 x 75 MW Karebbe hydro project 8 km downstream, we designed and oversaw the construction of the three-bay 150-20 kV, 20 MVA Balambano Switchyard extension. After Karebbe is commissioned, this extension will then supply Karebbe black-start power and rural electrification power at 20 kV to the district of Luwu Timor and PLN.
For the Balambano dam structure, a Roller Compacted Concrete (RCC) dam was selected as the best alternative as it resulted in both the lowest cost and shortest possible construction schedule for this dam site.
The site comprises ultrabasic, granitic rock that has been highly fractured due to tectonic activity. An active fault within 6 km of the site required a seismic design of the dam structure based on a peak horizontal acceleration of 0.6g (maximum credible earthquake). The powerhouse has two vertical Francis turbines with high inertia generators. The turbines, generators, exciters and governors for Balambano were supplied by GE Canada. The project was successfully completed and commissioned in December 1999.