Kyushu Electric Power Co., Inc., in constructing the recently completed first phase of the No. 1 Group of Shin-Oita Power Plant, Oita Prefecture (Kyushu Island), achieved further improvements over previous combined cycle plants, especially in the area of plant overall operation. It is composed of six combined cycle power units of the single-shaft, non-reheat type, based on Hitachi-GE MS7001E gas turbines, with a total output of 690 MW.

Trial operations of the first unit began in May, 1990. Commercial operations of the first unit began in November 1990, and the last unit in June, 1991.

The NO.1 Group incorporates two major advances over previous combined cycle plants.

The first advance is a two-stage multiple nozzle dry-type low-NOx combustor. This combustor is a new development for keeping the level of NOx emissions below 62.5 ppm (16% O2 at gas turbine exhaust).

The second advance is a new functionally and hierarchically distributed digital control system. By the control system, the plant was designed to bring the following notable features:

1 The individual units can be started and stopped automatically from the load dispatching directive center at the head office.

2 The plant can be operated for high efficiency with short starting and stopping time and large load variations.

3 Plant operating characteristics for emergency operations can be improved remarkably, for instance, load run back operations and fast cut back operation, etc.

The results of trial operations have shown that the output per unit is about 0.5 to 4.2% higher, and the unit efficiency about 1.9 to 3.7% higher, than the planned values (all percentages relative), and tangible improvements and starting characteristics and load fluctuation are also satisfactory with the specified target values in the overall operation of the plant over that of previous combined cycle power plants.

This plant has satisfactorily been operated since the start of commercial operation.

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