Quantcast Typical SCADA System Configuration

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reporting can ease maintenance and,troubleshooting diagnosis, as well as support emergency
planning.
9.1.2.2 Energy Management Systems. For large building complexes, a slightly different
version of the traditional SCADA system has emerged; that of the Energy Management System
(EMS). This equipment has been used extensively for large high rise office buildings and hotels,
as well as multi-building complexes typical of most Naval Facilities. The EMS generally has an
integrated central control and display panel that incorporates the building fire alarm system and
controls for the building's heating, ventilating, and air conditioning (HVAC) systems, and
controls for the building lighting system. As these are the major controllable building loads, and
are usually interruptible for short periods of time, the EMS monitors the building's main utility
meter and minimizes demand charges by shedding controllable loads for short time periods. The
time period is coordinated with the demand billing period of the electric utility (typically 5, 15, or
30 minutes). When the current demand period expires, the interrupted load is reenergized, with
the hope that in the intervening period the overall load has declined to a point that a new demand
peak will not occur. The EMS system is programmed to shed various loads by either fixed or
variable load priorities that are determined by the building management.
9.1.3 Typical SCADA System Configuration. The modern SCADA system generally
consists of a central station and three to over one hundred remote stations. The central station
generally consists of one or more computer consoles, with two or more central computers in a
redundant operating configuration. The computer consoles contain the computers,
communications equipment, power supplies, integral or separate data and alarm printers, and
depending upon configuration, the terminal strips that are necessary for connection to remote
equipment. The computer consoles have one or more Cathode Ray Tube (CRT) display devices,
with the means of operator communication: a touch-type keyboard, a touch screen, or a light
wand. The actual CRT displays, generated by specially written computer software, consist of
schematic multi-color representations of the various operating systems.
Electrical systems are usually represented in one-line diagram format with some geographical or
physical orientation of the various equipment rather than the top down style of a conventional
one-line diagram. Various system operating buses might be displayed in different colors to
reflect the different operating voltages. Circuit breaker status is indicated by red or green lights
to indicate closed or open status respectively. Bus power flows, voltages, and currents would be
displayed alongside the bus identification information. Transformers, circuit breakers,
disconnect switches, major circuits, and major utilization equipment are generally shown on the
display. The display may be broken down into more detailed screens to illustrate the details of a
complex system. All of the control conditions for generating units should be displayed;
frequency, load, voltage, watt or VAR control settings, power factor, and other information such
as unit alarm status. For a large boiler and steam turbine generator, this could involve several
subsystem displays (i.e., steam system, air system, fuel system, lubrication system, cooling
system, etc.). The remote units generally consist of one cabinet, each of which contains one or
9-3





 


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