12.1.1   Base load

 

Under normal conditions, all high merit plant would be expected to operate in a base load regime. This involves long periods of continuous operation, with infrequent 'down times' to facilitate statutory testing, inspection and overhaul/maintenance periods.

Base load units do not normally accumulate a high number of hot or warm start cycles or load-following cycles. Figure 2.89 shows typical run-up curves for a cold start on a 660 MW turbine-generator. In this particular example, full-load is achieved after nearly six hours, excluding the time taken to achieve satisfactory steam conditions at the turbine stop valves. This long run-up time is not only to limit differential expansion rates and rotor eccentricities, but also to limit thermal stresses within the turbine.

Typical 660 MW turbine-generator run-up curves for a cold start from 15C metal temperature

 

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