INTRODUCTION TO POWER SYSTEM AUTOMATION

1. POWER SYSTEM
AUTOMATION
Mohammed Naser
Automation and Control Engineer

2. Power-system automation
is the act of automatically controlling the power system via instrumentation and control devices. Substation automation
refers to using data from Intelligent electronic devices (IED), control and automation capabilities within the substation, and
control commands from remote users to control power-system devices.
Electrical substation
is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low,
or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric
power may flow through several substations at different voltage levels. A substation may include transformers to change
voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different
transmission voltages.
Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial
customer. Generally substations are unattended, relying on SCADA for remote supervision and control.
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3. Intelligent electronic devices (IED)
is a term used in the electric power industry to describe microprocessor-based controllers of power system equipment,
such as circuit breakers, transformers and capacitor banks.
circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused
by excess current, typically resulting from an overload or short circuit. Its basic function is to interrupt current flow after a
fault is detected.
transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic
induction.
capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field
microprocessor is a computer processor which incorporates the functions of a computer's central processing unit
(CPU) on a single integrated circuit (IC), or at most a few integrated circuits. The microprocessor is a
multipurpose, clock driven, register based, digital-integrated circuit which accepts binary data as input, processes it
according to instructions stored in its memory, and provides results as output. Microprocessors contain both combinational
logic and sequential digital logic. Microprocessors operate on numbers and symbols represented in the binary numeral
system.
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4. Power-system automation is composed of several tasks.
- Data acquisition
Data acquisition refers to acquiring, or collecting, data. This data is collected in the form of measured analog current or voltage
values or the open or closed status of contact points. Acquired data can be used locally within the device collecting it, sent to
another device in a substation, or sent from the substation to one or several databases for use by operators, engineers,
planners, and administration.
- Supervision
Computer processes and personnel supervise, or monitor, the conditions and status of the power system using this acquired
data. Operators and engineers monitor the information remotely on computer displays and graphical wall displays or locally, at
the device, on front-panel displays and laptop computers.
- Control
Control refers to sending command messages to a device to operate the I&C and power-system devices. Traditional
supervisory control and data acquisition (SCADA) systems rely on operators to supervise the system and initiate commands
from an operator console on the master computer. Field personnel can also control devices using front-panel push buttons or a
laptop computer.
power-system integration
which is the act of communicating data to, from, or among IEDs in the I&C system and remote users. Substation integration refers to combining
data from the IED’s local to a substation so that there is a single point of contact in the substation for all of the I&C data.
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5. 1-( Data acquisition )
The instrument transformers with protective relays are used to sense the power-system voltage and current. They are
physically connected to power-system apparatus and convert the actual power-system signals. The transducers convert the
analog output of an instrument transformer from one magnitude to another or from one value type to another, such as from
an ac current to dc voltage. Also the input data is taken from the auxiliary contacts of switch gears and power-system
control equipment.
2- ( Main processing instrumentation and control (I&C) device
- Remote Terminal Unit (RTU)
is an IED that can be installed in a remote location, and acts as a termination point for field contacts. A dedicated pair of
copper conductors is used to sense every contact and transducer value. These conductors originate at the power-system
device, are installed in trenches or overhead cable trays, and are then terminated on panels within the RTU. The RTU can
transfer collected data to other devices and receive data and control commands from other devices. User programmable
RTUs are referred to as “smart RTUs.”
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Hardware structure of the power-system automation

6. - Meter
is an IED that is used to create accurate measurements of power-system current, voltage, and power values. Metering values
such as demand and peak are saved within the meter to create historical information about the activity of the power system.
- Digital fault recorder
digital fault recorder (DFR) is an IED that records information about power-system disturbances. It is capable of storing data
in a digital format when triggered by conditions detected on the power system. Harmonics, frequency, and voltage are
examples of data captured by DFRs.
- Programmable logic controller (PLC)
can be programmed to perform logical control. As with the RTU, a dedicated pair of copper conductors for each contact and
transducer value is terminated on panels within the PLC. It is like a work-horse which work upon the command given by their
master.
- Protective relay
A protective relay is an IED designed to sense power-system disturbances and automatically perform control actions on the
I&C system and the power system to protect personnel and equipment. The relay has local termination so that the copper
conductors for each contact do not have to be routed to a central termination panel associated with RTU
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7. 4- Controlling (output) devices
- Load tap changer (LTC)
devices used to change the tap position on transformers. These devices work automatically or can be controlled via another
local IED or from a remote operator or process.
- Recloser controller
Recloser controllers remotely control the operation of automated reclosers and switches. These devices monitor and store
power-system conditions and determine when to perform control actions. They also accept commands from a remote
operator or process.
5- Communications devices
Communications processor
A communications processor is a substation controller that incorporates the functions of many other I&C devices into one
IED. It has many communications ports to support multiple simultaneous communications links. The communications
processor performs data acquisition and control of the other substation IEDs and also concentrates the data it acquires for
transmission to one or many masters inside and outside the substation.
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8. 1- Overcurrent protection
All lines and all electrical equipment must be protected against prolonged Overcurrent. If the cause of the overcurrent is
nearby then automatically that current is interrupted immediately. But if the cause of the overcurrent is outside the local area
then a backup provision automatically disconnects all affected circuits after a suitable time delay.
2- Supervisory control and data acquisition
(SCADA) transmits and receives logic or data from events of controls, metering, measuring, safety and monitoring of
process devices such as Electrical equipment, Instrumentation devices, telecommunication on industrial applications. Power
system elements ranging from pole-mounted switches to entire power plants can be controlled remotely over long distance
communication links. Remote switching, telemetering of grids (showing voltage, current, power, direction, consumption
in kWh, etc.), even automatic synchronization is used in some power systems.
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Applications

9. THANK YOU
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