译文：
Supervisory Control and Data Acquisition(SCADA)
The principal function of data acquisition iS the collection of raw data from the remoteterminal units(RTUs)，conversion of analog data to engineering units and storage of data in the database．The data collected may include circuit breaker status，transformer tap positions，MW and MVAR flows，frequency，branch currents，bus MW and MVAR injections，energy metering and miscellaneous data such as weather data and various substation equipment status and alarms．The RTUS may be scanned every tWO tO three seconds for status data and for certain analog data with the remaining data scanned at one of more slower scan cycles tO reduce load on the data acquisition subsystem in the control center，alternatively data may be}ransmitted spontaneously by each RTU following the recognition of an
event such as a status change of the crossing of an event—delta by an analog value．The cost of RTUs will represent a major portion of the capital cost of a new control center．
Supervisory control of remote device is performed through the dispatcher consoles using cursor and keyboard control for selection of device tO be controlled via colour—coded starion line diagrams and other station oriented displays．The devices controlled invariably include main system circuit breakers and transformer taps but may also include voltage reduction transformers and circuit breakers for load shedding／load restoration．