SCADA Systems for Power Grid
Ozan Cakmak
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Electric power generation,
transmission and distribution:
Electric utilities detect current flow and
line voltage, to monitor the operation of
circuit breakers, and to take sections of
the power grid online or offline.
Buildings, facilities and
environments: Facility
managers use SCADA to
control HVAC, refrigeration
units, lighting and entry
systems.
Manufacturing: manage parts
inventories for just-in-time
manufacturing, regulate
industrial automation and
robots, and monitor process
and quality control.
Mass transit: regulate electricity to
subways, trams and trolley buses; to
automate traffic signals for rail
systems; to track and locate trains
and buses; and to control railroad
crossing gates.
Water and sewage: State and
municipal water utilities use
SCADA to monitor and regulate
water flow, reservoir levels, pipe
pressure and other factors.
Traffic signals: regulates
traffic lights, controls traffic
flow and detects out-oforder signals.
SCADA control
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SCADA Systems for Power Grid
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A SCADA system performs four functions:
1. Data acquisition
2. Networked data communication
3. Data presentation
4. Control
These functions are performed by three kinds of SCADA
components:
1. Remote terminal units (RTUs)
2. Master Station / RCC (Region Control Center)
3. The data telecommunications network
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Example: Lamp indication(SCADA)
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SCADA - Other Advantage
SCADA systems other advantage is the ability to limit the
amount of data transferred between Master Station and RTU.
This is done through a procedure known as exception
reporting where specific data is sent only when the data
changes that exceed the limit setting, such as the frequency
value can only be changed if there is a change of 0.05 Hertz.
if there is a change whose value is very small there will be no
change in frequency. This is to anticipate the hysteresis
properties of the system so that the actual frequency value
can be read clearly.
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When operation is performed from Master Station, the first to
do is confirm that the equipment selected is appropriate,
followed by the selection of the operation to be performed.
Master Station Operators in the action based on a procedure
called the method "select before execute (SBXC)", as shown
below:
1. Dispatchers at Master Station choosing RTU.
2. Dispatchers choose the equipment that will be operated.
3. Dispatchers sends the command.
4. Remote Terminal Units to know the equipment to be
operated.
5. Remote Terminal Units perform the operation and send a
signal back to the Master Station indicated by color
changes on the VDU(Video Display Unit) screen and
prints a message on the printer logging.
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If an interruption in the RTU, message will be sent from
RTU that is misbehaving earlier to the Master Station,
and the normal scan will be delayed long enough for
Master Station prioritize messages and nuisance alarms
turned on in order operators can take the necessary
action as soon as possible.
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At other times, in most cases, the status of all equipment
on the RTU can be monitored every 2 seconds, giving
information system condition which is going on at the
operator control center (RCC).
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References
http://en.wikipedia.org/wiki/SCADA
http://www.powersystem.org/scada
http://nrldc.org/docs/documents/Articles/SCA
DAinIndianPowerSystem_PKA.pdf
http://en.wikipedia.org/wiki/Power_generation
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