Upgrading a 1970s-era generator control system to new millennium technology in 12 days during a three-week shutdown would require careful planning and teamwork under any circumstances. The quick replacement of the governor and control system at the PT Inco smelter’s hydroelectric generation system is even more impressive because the facility is located in the middle of an Indonesian jungle.
PT Inco, an integrated mining and smelting nickel producer that is a subsidiary of Vale Inco Ltd., operates a smelter in the central part of Sulawesi, Indonesia. The facility is located literally at the end of the road and in the middle of the jungle. However, the remote site has one strong attraction: three large lakes located near the smelter’s power generation system.
The key competitive advantage that PT Inco has over other nickel producers is that it owns and operates its own hydropower stations to produce the large quantity of electric power required by the smelting process. The three nearby lakes supply water to the reservoir that is next to the power station.
Jungle Generation
The generation system at the PT Inco smelter originally consisted of the Larona Power Station, commissioned in 1978 (Figure 1). The station was equipped with three Sulzer Francis turbines coupled to 65-MVA Hitachi generators. Due to the lay of the land, there is a 7-kilometer-long (4.2-mile-long) intake canal equipped with two radial intake control gates. The head pond at the end of the canal feeds three 1.3-km-long penstocks, which are large pipes that connect the head pond to the generators. The Larona units are equipped with bypass valves to protect the penstocks during load rejections.
1. Larona Unit 1's open bypass valve. As shown, the generator bypass valve will open to relieve pressure surges in the penstock in the event of a large loss of load. Courtesy: PT International Nickel Indonesia
In 1999, the Balambano Power Station was commissioned (Figure 2). It was equipped with two GE Francis turbines coupled to 80.6-MVA GE generators. In 2002, Larona Unit 3 was upgraded with a 68-MVA GE generator. The new unit has significantly higher inertia than the original unit.
2. Balambano Power Station. The power house where the two generators are located is shown in the lower right. The two 90-m (295-ft) penstocks can be seen in the middle right portion of theimage. The three spillways in the middle left are used to allow water to bypass the generators during times of high rainfall or maintenance. Courtesy: PT International Nickel Indonesia
These five units constitute "dirty" power, whose frequency will swing between 47 and 52 hertz in what is typically a 3-minute cycle. Recent recording showed swings between 45 and 55 hertz over a two-day period, without a trip. The primary loads on this grid are four electric arc furnaces and other loads that can handle this type of power.
In contrast, "clean" power at the facility is provided by five 8-MW diesel generators, 32 1-MW diesel generators, and one 28-MW steam generator. Two DC links enable the transfer of up to 38 MW between the clean and dirty power grids.
In summary, the types of power available at the site are as follows:
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Dirty power: 2 x 65 MW + 1 x 68 MW + 2 x 68.5 MW = 335 MW
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Clean power: 5 x 8 MW + 32 x 1 MW + 1 x 28MW = 100 MW
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Transferable power: 2 x 19 MW = 38 MW (as a portion of totals above)
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