In addition, manual functions for governor control, synchronous closing, and ACB (air circuit breaker) control are normally available at a minimum in case the automatic functions fail to operate.
In contrast, the distributed control system is composed of multiple controllers and a management device; the controllers independently controls individual generating plants and the management device performs comprehensive control tasks such as stand-by generator selection. In this control system, any failure of a controller have not effect on functions of other controllers (including automatic synchronous closing function). The distributed control system is also provided with manual operation mechanism to enable generators to be manually operated in parallel.
3. Features of the Distributed Control
A main reason why the centralized control was so far adopted is probably limited to its low cost due to only one CPU and power supply unit required. This control system, however, have disadvantages that a system failure may affect all generators (resulting in low reliability of power supply) and that it takes large installation space in a switchboard.
The distributed control system have the following features:
(1) Enhances the reliability of power distribution system.
(2) Accommodates an increase in the number of generators (superior in expandability).
(3) Is easy to install in switchboards because individual controllers decentralize may be decentralized.
(4) Saves wiring among switchboards, improving reliability of switchboards.
Although the distributed control system costs of itself more than the centralized system, the rationalization in switchboard design have allowed the price of switchboards with distributed system to be nearly the same as the price of those with centralized ｓsystem.
