Power system automation

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LECTURE 6: POWER SYSTEM AUTOMATION
6.1 Introduction:
Power System Automation is one of the important aspects in an electrical power network that needs
careful investigation. In power system automation, data acquisition system plays a major role as a
base of the power system automation. From the recent trends and developments in Power System
Automation, Computerized system Automation is most efficient compared to normal systems.
Computerized Power Network for Data Acquisition system helps the system and controller to meter
and monitor the values for further manipulations for full-scale power system automation and system
controlling.
The Computerized Data Acquisition for Metering and Monitoring of Power System Automation can be
divided into three general categories as Data collection, Metering & Monitoring. The Data collection
system collects the data from the Power system Network using the Digital Power Monitors through the
current transformers and potential transformers. The collected data will be Metered by the Digital
Power Monitor where the Monitor consists of a Micro Controller with the peripherals like memory, A/D
converter and Sample and hold circuitry. According to the programming done in the Microcontroller
the Power Monitor will store the parameters in the memory and it will do all the logical and arithmetic
calculations to manipulate the parameters and to calculate the different Power data’s like KWH,
KVAR, KVA, PF etc,. The collected parameters of the Power System and the calculated power data
can be monitored on the screen of the Digital Power Monitor. The values will be sent to the Computer
System using the Communication system like Serial Communication RS485 and RS 232 for n no of
Power Monitors using the Data Converter.
This section describes power system automation protection and control which is aimed at the
improvement of the management of power networks is being adopted by increasing by number of
supply authorities. Automation, Protection, Local control, Operator interfaces, Communication,
Remote control and Monitoring functions, most of which were previously utilized with relays or
modules for each function, are now integrated into multi-function PLC (programmable logic Controller)
based units and interconnected on various types of local area networks. The components of the
system will have a better communication with each other sharing information through the local area
network and systems work similarly because one sensor is enough to collect one network information
and transferred the information through out the network using LAN and communication mediums
instead of one sensor per each component as before. To achieve we need a better system apart from
different systems like protection, Communication, RTU’s, IED’s etc. called as Data acquisition system
with out the perfect data communication system the components of the total system cant perform the
right tasks at right time because of the disturbance in the collected. To overcome this problem we
have designed a better Data Acquisition system with the efficient technology and with the perfect
communication systems to transfer the data. The system is named as “Computerized Power Network
Data Acquisition and Monitoring for Power System Automation”. The system acquires the data from
the power network (data acquisition) for monitoring. The software was developed to do all the
manipulations and the parameters and data of the system can be viewed in different forms (analog,
digital, graphical). The software developed will be used to view the captured data’s from the Power
Monitor in different forms like Analog Metering, Digital data and in graphical form. The software will
generate the reports for all the different types of manipulations like power fail, CT or PT fail Low PF
etc, the software will save the data 6 times per day in form of reports.

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6.2 BENEFITS OF POWER SYSTEM AUTOMATION
Important benefits of automation can be listed as follows
1. Improved quality of service and reduced manpower requirements
2. Improved reliability with reduced system implementation costs
3. Maintenance/expansion of customer base and Reduced operating costs
4. High value service provider and reduced maintenance costs
5. Added value services with the ability to defer capacity addition projects
6. Improved customer access to information and also improved information for engineering
decisions
7. Enterprise information accessibility along with improved information for planning decisions
8. Flexible Billing Options and reduced customer outage minutes
6.3 POWER SYSTEM AUTOMATION
Power System Automation is a system for managing, controlling and protecting the various
components connected to the power network. It obtains the real time information from the system,
local and remote control applications with advanced electrical system protection. The core of power
system automation stands on local intelligence, data communications with supervisory control and
monitoring.
Structure of Power System Automation
The functional structure of power system automation will be as shown in fig 6.1.
 Electrical Protection
 Control
 Measurement
 Monitoring
 Data Communications
Fig 6.1 Functional structure of Power System Automation
Electrical Protection
Electrical Protection is the most important concept of the Power system Automation, to protect the
equipment and personnel and to limit the damage at fault. It is a local function and it has the capability
to function independently from the Automation if necessary, although it is a part of Power system
Automation the function of electrical protection never restricted in Power system Automation.
Control

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Control application of a Power system Automation includes local and remote control. Local control
consists of actions the control device can logically take by it self (Bay interlocking, switching
sequences, and synchronizing check). Human intervention is limited and the risk was greatly reduced.
Remote control functions to control Substations remotely from the SCADA. Commands can be given
directly to the remote control devices (open and close of circuit breakers, relay settings, requests for
information from the SCADA station). This eliminates the personnel performance switching
operations, actions can be performed faster. A safe working environment is created for personnel and
the operator or engineer at the SCADA has a complete over view of the entire Power network.
Measurement
Measurement is one of important concept in Power system Automation. The real time information
about a substation or equipment is collected and displayed in the control center and stored in a data
base for further manipulations, It erases the personnel to go to substation or switching area collect the
information cutting down workloads. The information collected can assist in doing network studies like
load flow analysis, planning ahead and preventing disturbances in the Power network. Previously the
word ‘Measurement’ refer to voltage, current and frequency, and the word ‘Metering’ refer to power,
reactive power and energy (KWh). The different terms used because different instruments were used
for these applications, now the two functions are integrated in modern devices hence the terms are
used interchangeably in the text.
Monitoring
Monitoring is specified for the maintenance of the Power system Automation. It monitors sequence of
records, status and condition of the system, maintenance information and relay settings etc. The
information can help in fault analysis, what where when why it happened. It is used to improve the
efficiency of the system.
Data Communication
Normally Communication forms a core for any system, in Power system Automation Data
communication forms core of the power system Automation. With out communication the local device
and protection tasks can be performed individually. But with out data communication there is no
mean to say Power system Automation.
6.2 ARCHITECTURE FOR POWER SYSTEM AUTOMATION
Figure 6.2 shows the generalized architecture for Power System Automation. There are three levels
which are connected to each other through communication medium.

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Level 1: This level contains the field equipment and Switch gear, CTs, PTS, etc. Monitoring and
measurement of system parameters are carried out at this layer.
Level 2: This level contains the protection and control equipment. Protective relays, RTUS and IEDs
constitute this layer. The collected information for layer 1 is processed here.
Level 3: This level contains the Operator Display and Engineering Workstation for executing the
programs. This level is also called as the Energy Management Systems (EMS) Level or Layer, where
network analysis programs are run for operating the system
Power system automation is concerned mostly with levels 1 and 2. The RTUs and IEDs on receiving
information determine the tasks to be carried out for automation. The usual tasks in automation are
1) Switching (on or off) of Equipment like Capacitors, Reactors
2) Network Switching (on or off) or Reconfiguration of Transmission or distribution lines
3) Changing settings on equipment (Transformer on-load tap changing),
Fig 6.2. Architecture for Power System Automation

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6.3 Classification of Power system Automation
a) Substation Automation
b) Distribution Automation
Substation Automation
Substation automation is not a new concept. Substations have been equipped to perform automatic re
closing, bus sectionalizing, load transfers, capacitor switching, etc. for many years. In the past, these
and other functions were implemented using a combination of control panels, auxiliary relays,
switches, lights, meters, transducers and extensive wiring and cabling. In many applications today,
this perception is probably because developments in substation equipment have expanded the
potential capabilities of substation. Automation far beyond that which could previously be reasonably
accomplished. The principal development is generically defined as an Intelligent Electronic Device
(IED) which typically consists of one or more Programmable Logic Controllers and communications
ports; with the ability to transmit data and execute control commands, and frequently provide a local
user interface. Typical examples are relays, meters, and specialized sensors. Prior to the introduction
of Numerical relays, the protection and control of a very small substation consisting of one incoming
line, one transformer and two feeders would require four large panels filled with relays, switches and
lights. Only one panel is required when Numerical relays are used. Interestingly, at the same time the
space requirements are reduced by a factor of four, so the installed cost.
Advances in communications technology are used to tie everything together into a useful network.
Within the substation, a single high-speed Local Area Network (LAN) is used to transmit data and
control commands, replacing the extensive and costly cables that had been required. At the present
time, a number of different LAN techniques and protocols are in use. The industry is actively working
on development of a new standard LAN definition that will be based on the use of Ethernet and
Manufacturing Messaging Specification (MMS) and will be compatible with the Utility Communications
Architecture (UCA). There are already many techniques for moving data out of the substation to a
master station or to other substations. These include the use of leased or dedicated telephone lines,
dial-up phone lines, cellular telemetry techniques, satellite transmissions, various flavors of radio
techniques and fiber-optic networks. Basically, this variety of communications methods results in the
ability to transmit large amounts of information at a rapidly declining cost per bit. The combination of
PLC based devices and communications technology creates the ability to obtain more information
about the power system and the equipment being used. Power system variables include magnitude
and angle of voltages and currents, real and reactive power, frequency, power factors etc. Information
is available regarding the initiating event for relay operation, the location of faults, and fault analysis.
Specialized sensors and transducers are used to build a database relating to equipment condition and
use; so that analysis techniques can be used to determine equipment condition and base
maintenance activities on actual condition rather than time schedules. Within the substation, the use
of Programmable Logic Controllers or other types of computers opens up a vast array of automation
possibilities. Complex schemes for dead bus and dead line re-closing can be implemented, with the
sequence being based on actual power system conditions that exist at the time. Re-closing of circuits
can be modified based on cold load pickup requirements. Load transfers between busses and
transformers can be made to protect against transformer overloads. Bus voltages and power factors
can be tightly controlled to minimize losses or voltage variations. Supplementary measurements and
inputs can be used to initiate automatic equipment re energizing after a transformer or bus differential.
Distribution Automation
Distribution Automation systems have been defined as system that enable an electric utility to
monitor, coordinate and operate system components in a real time mode from remote locations the

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distribution automation is modular and may be implemented in phases to include remote monitoring
and control of substation, feeder and consumer devices and loads.
The goals of Distribution Automation are:
 Reduced costs
 Improve service reliability
 Better consumer service
 Enhance government relations

Distribution Automation system postulates are:
 Deferred capital expenditures
 Reduced operations and maintenance expenses
 Improved outage response and restoration
 Enhanced system efficiencies
 Enhanced consumer satisfaction
 Improved data information
 Positive public image

Distribution Automation system de postulates are:
 Prevent outages
 Alleviate the need for a sound maintenance program
 Replace good operation practices
 Eliminate the need for appropriate planning
As utility managers and engineers interested in effective approaches to increasing efficiency and
productivity the latest “high tech” developments must be continuously reviewed by the utility.
Increased competition has led large existing and potential commercial consumers to carefully
evaluate both the direct cost of electric service and the monetary value of reliable electric service.
These activities in conjunction with increased awareness by residential consumers of even the
shortest loss of electric service have resulted in increased emphasis by regulatory agencies in
qualifying the cost to consumers of outages. It is important to identify the costs and benefits of each
project including the value of improved reliability to the consumer.
1.4 Problem Description
The problem at hand is to develop a better Data Acquisition System. This involves the hardware and
the software used in a Data Acquisition system and Power System Automation. This paper focuses on
developing the hardware and software for the system. The software component can be considered
the soul of the data acquisition system as it is the very presence of software as the decision making
entity in the system that makes the system unique. All existing data acquisition systems had to
undergo hardware changes in order to change the settings or functional parameters. This involved the
tedious task of rewiring the existing system. The fact that data acquisition system makes the base of
the power system automation in all the causes of various applications and simple software to monitor
the total system with the acquired data makes the problem at hand simple. For instance, earlier, if the
data to be collected from the system or from the components of the system the controller or engineer
should go to the field with a large equipment and the time take for the collection of data will be very
high and where the data collected data is not accurate it will not matches with the calculated values
and the decision making for any thing is to difficult where the data what we have is not sufficient to do
some thing these are the problems exists in the previous data acquisition system.
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

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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.
In order to overcome the situation digital technology has been adopted for the better data acquisition
system. The digital system will have a sampling rate where it samples each data collected from the
systems, takes the average of the data and gives the perfect accurate value of the system value
which can be useful to do any manipulations at the effective. The computerized power network uses
the PLC based Data Acquisition technology which collects the data from the Power system through
the sensors and transducers and sends the data to the PLC the system will manipulate the data and
sends the data to the human interface system. The controller will have the better understand on the
system situation and he can take perfect decision at right time. The Digital systems are programmable
so they have the capability to understand the situation of the system and they can take the pre
commanded decisions without the interference of the human, which increases the efficiency of the
total system.
Monitoring
The word monitoring in Data Acquisition means the over view of all the system. The acquisition
system will collect the data from the Power system network and store the online data in the main data
base, and it will be monitored at the controller section on the HMI. As the acquisition system is self
programmed the decisions can be made by the system also where normally the controller won’t have
that information. So the system monitoring will have the complete view on the total system means the
online system parameters, decisions taken by the system, time of system shutdown, switch on relay
trip fault location, type of fault, power drawn by the bus bars etc. where using this the controller can
say that what the system is doing at any particular time while he have the perfect command on the
total system
. Meter Placement
The placement of meters also plays a role in the Power system Automation and Data Acquisition
system. If the meters are placed as such with out any perfect survey some of the meters m ay be over
loaded and some of them may ideal so unnecessary things will arise in the system. The solution is to
have optimal placement of meters using the developed software for the optimal placement of meters
we can find out where the meters to be placed from the n number of nodes where the system will
have the better working part and cost effective.
1.5 IMPLEMENTATION OF POWER SYSTEM AUTOMATION AND PROTECTION USING SCADA
The Computerized power network data Acquisition and monitoring for Power system Automation have
been implemented using part of software and hardware. The hardware involves different type of
digital, communication equipment with a Computing system. The software involves the data collection
and monitoring software with the AMP (Automatic Meter Placement).
5.1. Hardware Development
The Computerized Power Network for Data Acquisition Metering & Monitoring System for Power
System Automation have been adopted to a small proto type substation model as shown in fig.6.3a
and fig 6.3b. The details of Data Acquisition Metering & Monitoring System are shown in fig.6.4a and
fig 6.4b. The Power Monitors were connected at the Generation and Distribution end. The data will be
collected by the system using the Data Converter and the RS 485 and RS 232 serial Communication
systems.

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Main Source Reserve Source
IS1IS2
PT1
PT2
CT1 CT2
CT4
CT5 CT6
MHTBB RHTBB
CT3
CB1
CB2
CB3
CB4
CB5 CB6
HTBB
LTBB
TRANSFORMER
LOAD 1 LOAD 2
Main Source Reserve Source
IS1IS2
PT1
PT2
CT1 CT2
CT4
CT5 CT6
MHTBB RHTBB
CT3
CB1
CB2
CB3
CB4
CB5 CB6
HTBB
LTBB
TRANSFORMER
LOAD 1 LOAD 2
Fig 6.3(a). 33/11 KV Substation Fig. 6.3(b). 33/11 KV Proto type Substation
The selected 33/11 KV substation single line diagram. In the Computerized Power Network for a scale
down Substation model, the Power monitors were connected at the 33KV Bus Bar and at 11KV Bus
Bar. The two meters were connected to the Data Converter through RS485 Connectors and the Data
converter is connected to the Computing system through RS232 connector the RS232 and RS485 are
the two types of different Serial Communication Systems used in the Power Network
Fig. 6.4(a) Data Acquisition System For SCADA Model Fig. 6.4(b) Data Acquisition System For SCADA Model
The Power Monitors will collect the data from the Power Network and the data will be manipulated
and different power system data’s will be calculated the data can be viewed on the LCD display of the
Power Monitor. The data will be sent to the Computing system through the Data converter and
RS485, RS232 two way Communication systems.
The simplified model for the Computerized Data Acquisition is shown in fig 6.5a. A simplified model
corresponding to figure 6.3a was developed in hardware and information for CT and PT were

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collected and sent tp the computer for processing. Fig 6.5b shows the digital meter which transmit
and receive information from the hardware model to the computer and vice versa
Fig .6.5(a) Schematic of Hardware Setup Fig .6.6(b) Monitoring and metering interface.
5.2. Software Programming
The Software is developed using Visual Basic and the Micro Soft access is used as the data base for
the software. The software consists of two parts one is automatic meter placement AMP and the
second one is Data Acquisition. Using the Data Acquisition software we can do all the manipulations,
report generations and we can view the same parameters and data in the software as an analog and
digital meters as shown the software will generate the failure reports daily schedule online reports and
the data reports for 6 times in a day. The online parameters and data can be viewed as analog and
digital data as shown in fig 6.7a and fig 6.7b
Fig 6.7(a) Three phase parameters in graphical view Fig. 6.7(b) Three phaseparameters in icon view
5.3. Control through Automation
Control refers to sending command messages to a device to operate the control instruments and
power system devices the meters. Traditional supervisory control and data acquisition (SCADA)
system relay 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.
1.6Simulation
The simulation is done using the developed hardware for 2 power monitors with the proto type
33/11KV substation model in the presence the Human Machine interface (HMI) and software and the

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different outputs have been verified and generated for the implementation and simulation studies like
report generation, power factor control and relay coordination etc.
6.1. Report Generation
The software will save the online data as a text file in the form of report for further reference, the
software will generate daily reports at 6 different timing in a day to plot the load curve and etc,. Fig
6.8(a) and 6.8(b) show the graphical view and on line reports by the software. The online parameters
and data can be viewed as a comparison chart. The online parameters can be viewed as a graphical
representation for different parameters as three phase parameters line parameters power factor
power KWH, KVA, KVAR. It will give the report generation in different forms for different fault
conditions or any abnormal conditions. Failure reports like online reports, power fail, CT fail, PT fail
and Low PF can be viewed as shown in fig 6.9a and 6.9b
Fig 6.8(a) Three phase currents in graphical view Fig 6.8(b) Online reports
Fig 6.9(a) Failure reports data base Fig 6.9(b) Failure reports

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Fig .6.10(a) low power factor reports data base Fig .6.10(b) low power factor reports
6.2. Power factor Control
The power factor can be controlled using the meter and software developed whenever there is a low
power factor i.e., below 0.6 the meter will give alarm with a report saying that low pf as shown in fig. 9
6.3. Relay Coordination
The software and the meter hardware have the availability to control or operate the relays from the
HMI using the meter as the hardware. Whenever a fault occurred in the system the software will send
signal to the relay to trip

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6.7 SCADA Based Model for Automation and Digital Protection
A SCADA based power system automation model has been developed as a part of the course. A
laboratory based model for EMS-SCADA was used to supplement the course. . The stage by stage
development of the SCADA system which is used for EMS applications and SCADA testing is
presented and discussed.
Fig.6.14 SCADA based model for Automation and Digital Protection
Fig 6.14 shows the complete model of the SCADA based Automation and Digital protection System.
The schematic for the hardware is shown in fig 6.15.
Fig. 6.15 Schematic diagram for SCADA based model for of Automation and Digital Protection

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Local and remote monitoring and control were achieved from this model. Bothe Ethernet based
communication and fiber optic based communication were employed for automation and protection
respectively
Fig. 6.16 Integrated SCADA Hardware Model
Fig 6.16 shows the complete model and panels for Power System Automation, which consists of four
phases and Digital protection System,
1. Real time monitoring and Data Acquisition
2. Control, Automation ad switching of circuit breakers, capacitors and loads
3. Numerical Relaying and Protection
4. Web based remote monitoring and control
Fig. 6.17a Data Acquisition System For SCADA Fig. 6.17b Numerical Relay and Protection Panel

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Fig 6.17a shows the Data Acquisition System, (DAS) through digital meters. Fig 6.17b shows the
panel for numerical relaying and protection. The SCADA interface, operator setting and two numerical
over current relays can be observed.
Fig.6.18 Modular development of the Hardware model of SCADA System
Fig 6.18 shows the local and remote control modules housed in different locations. Real time
monitoring and decision making by the operator can be achieved by this system.
This complete model of SCADA based automation and numerical protection can be effectively used
by integrating numerical algorithms develop in house and testing them on the hardware model.
Several digital and numerical protection relaying algorithms have been developed by the students and
integrated into this model.

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References
1. A study on IEC 61850 based communication for intelligent electronic devices - Gwan-Su Kim,
Hong-Hee Lee; Science and Technology, 2005. KORUS 2005. Proceedings. The 9th Russian-Korean
International Symposium on; 26 June-2 July 2005 Page(s):765 – 770
2. Overview of IEC 61850 and Benefits - Mackiewicz, R.E.; Power Systems Conference and
Exposition, 2006. PSCE '06. 2006 IEEE PES; Oct. 29 2006-Nov. 1 2006 Page(s):623 - 630
3. IED Modelling for IEC61850 Based Substation Automation System Performance Simulation -
T.S. Sidhu, Fellow, IEEE and Yujie Yin, Student Member, IEEE; Power Engineering Society General
Meeting, 2006. IEEE;18-22 June 2006 Page(s):7 pp.
4. Remote Data Monitoring and Data Analysis for Substations - A Case Study in Implementation -
Dolezilek, D.; McDermott, B.;Power Systems Conference: Advanced Metering, Protection, Control,
Communication, and Distributed Resources, 2006. PS '06,14-17 March 2006 Page(s):496 - 500
5. Advanced SCADA concepts - Sciacca, S.C.; Block, W.R.; Computer Applications in Power, IEEE
Volume 8, Issue 1, Jan. 1995 Page(s):23 – 28

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