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 large amounts of digital and analog data routinely. This provides data processing capabilities
that were only dreamed about less than twenty years ago. Advances such as fiber optic cables,
enhanced the reliability of the communications path. The advent of Local Area Networks
(LANs) has provided the development of systems which allow each of the RTUs to communicate
with other units; outdating the old system that allowed only the MCU to communicate with
individual remotes.
9.1.2 SCADA Applications for Electric Utilities. Electric utilities have used SCADA
systems mainly to control generation plant output and to monitor and remotely control their high
voltage transmission systems. In recent years, SCADA systems have become more economical
for monitoring and controlling electrical distribution systems of voltages no less than the 15 kV
class. Most utilities have few, if any, distribution systems in the 5 kV class, as load growth has
forced the upgrade or elimination of these systems. Utilities monitor the load on various
distribution circuits, monitor the status of circuit breakers, monitor the voltage and power and
VAR flows on transmission circuits, and monitor and control the power and VAR flows from
power generating stations. The concentration of data points to be monitored at typical utility
substations makes installation of SCADA systems easily justifiable. The standardization of most
utility substation designs allows utilities to more readily design and install SCADA equipment
than the typical commercial or industrial user, whose distribution system is unique in
configuration, and generally has a lower concentration of data points at any one substation.
9.1.2.1 SCADA System for Electrical Distribution. Since the typical NAVFAC electrical
distribution system is similar to the typical industrial electrical distribution system, the economic
justification for a dedicated SCADA system is often difficult, as the concentration of data
points is usually relatively low and the configuration at any one site is unique. This does not
preclude the use of a SCADA system, it means that the SCADA system used will have to serve
other applications, just as in most industrial plants, where the SCADA system is installed to
control the plant process, monitoring the electrical system is one of the side benefits.
Unless an electrical distribution system is quite large and complex, the use of a SCADA system
alone, for monitoring and controlling the electrical distribution system, cannot be economically
justified. In most plants, the SCADA system is used to control the plant process. The SCADA
system, as used on an electrical distribution system, should monitor and control the same
conditions as those discussed for an electric utility (i.e., the monitoring of power flows, voltage,
and current for major circuits, the monitoring and control of circuit breakers, and the monitoring
and control of generation units). The electrical system configuration can, therefore, be changed
remotely by closing or opening various circuit breakers and switches. Trouble can then be
detected immediately, as alarm conditions and automatic protective device operations are
reported to a central location. The SCADA system can also accumulate the information
necessary for utility load shedding and energy conservation. Historical data, for use by
management and engineering personnel, is readily available. Automatic alarm and trouble
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