A SCADA System typically provides the following functions:
• Comprehensive monitoring of primary and secondary plant
• Secure control of primary plant
• Supervision of secondary plant
• Operator controlled display of non-SCADA data
• Alarm management
• Event logging
• Sequence of events recording
• Trend recording
All functions must be provided with a high level of security and reliability. The control system itself must be highly self-monitoring and problems brought immediately to the operator’s attention. Operator access must also be protected by a security system. In addition, certain performance standards are required, for both data acquisition and the user interface. For example, time recording of events to one millisecond resolution is now possible. Whilst user interface performance is less critical, operators expect that their actions will result in display delays measured in only a few seconds: for example, from the execution of a circuit breaker control, to the change of indications on the display.