Analysis and Design of a Modern SCADA System

CHAPTER TWO

Introduction to SCADA systems and Modern Networking

Technologies

2.1 SCADA and its Functions

SCADA is a technology that enables a user to collect data from
one or more distant facilities and/or send control instructions to those
facilities. Using SCADA, it is not necessary for a user to attend or visit
remote locations in the normal system operation [ 22 ].
A SCADA system (hardware and software) should implement
one or more of the following functions [ 22 ]:

1. Alarm function—the capability of a supervisory system to perform
   a predefined action in response to an alarm condition.


2. Analog function—the capability of a supervisory system to accept,
   display, and record analog quantities sensed by transducers or
   external devices.


3. Control function—the capability of a supervisory system to
   selectively perform manual or automatic operation (singularly or in
   selected groups) of external devices. Control may be either analog or
   digital.


4. Indication (status) function—the capability of a supervisory system
   to accept, record, or display the status of a device.


5. Accumulator function—the capability of a supervisory system to
   accept total digital pulses and make them available for display or
   recording.


6. Sequence of events function—the capability of a supervisory
   system to recognize each predefined event, associate a time of
   occurrence with each event, and present the event data in the order of
   occurrence of the events.