Scada Report
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ANNEXURE – VII PROJECT REPORT (Project Semester January-June ) STUDY OF SCADA SYSTEM IN POWER MANAGEMENT Submitted by SACHIN GUPTA Roll No 1040556 AMANDEEP SINGH Roll No 1040544 Under the Guidance of 1
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Transcript of Scada Report
ANNEXURE – VII
PROJECT REPORT
(Project Semester January-June )
STUDY OF SCADA SYSTEMIN POWER MANAGEMENT
Submitted by
SACHIN GUPTA
Roll No 1040556
AMANDEEP SINGH
Roll No 1040544
Under the Guidance of
Mr. NIRBHAOJAP SINGH Department Of Electrical and instrumentation Engineering
THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY, PATIALA(Deemed University)
June/December 200ANNEXURE – VIII
1
DECLARATION
I hereby declare that the project work entitled (“Title of the project”) is an authentic record of
my own work carried out at (Place of work) as requirements of six months project semester
for the award of degree of B.E. (Civil Engineering), Thapar Institute of Engineering &
Technology (Deemed University), Patiala, under the guidance of (Name of Industry
coordinator) and (Name of Faculty coordinator), during June to December, 2003).
(Signature of student)(Name of Student)
(Roll No.)
Date: ___________________
Certified that the above statement made by the student is correct to the best of our knowledge and belief.
(Name & Designation) (Name & Designation)
Faculty Coordinator Industry Coordinator
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ANNEXURE – VI
CONTENTS OF THE REPORT
1. Cover page – on hard paper2. Inner page – same as cover page but on the soft paper3. Declaration4. Acknowledgement (if any)5. Contents
Summary Introduction Work Industry Review Details of the work including work programme & results Conclusions and Future Scope of Work References (if any)
6. Impediments/difficulties faced during project semester on project work; Suggestions related to work/project semester.
Please note the case of letters in the cover page. The 3rd. line is 16 pt bold and other lines are 12 pt. The page is centered. Department and Institute names are bold.
The matter contained in the report should be typed in MS word (1.5 spacing) Times New Roman, 12 pt or equivalent with other software.
Figures and tables may be inserted in the text as they appear or may be appended in order.
List of references shall be appended at the end.
Subject matter should be typed on both sides.
A total of THREE copies may be prepared – one for the student, second for the industry coordinator and third for the institute.
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INDEXINDEX
1. Summary2. Introduction 3. Work – 4. Industry - 5. Review6. Details of the work including work programme & results 7. Conclusions and Future Scope of Work8. References (if any)9. Impediments/difficulties faced during project semester on project work;
Suggestions related to work/project semester
1) INTRODUTION...........................................................................................................4
2) ABOUT SLDC (PATIALA).....................................................................................4
3) WHAT IS SCADA SYSTEM...................................................................................5
3.1) SUPERVISORY CONTROL.......................................................................................................5
3.2) DATA ACQUISITION................................................................................................................6
4) MAIN FEATURES.....................................................................................................6
5) LIST OF GRID SUB STATIONS AND THERMAL/ HYDRO GENERATING STATIONS COVERED UNDER SLDC PROJECT.................7
6) MAIN OPERATION OF SLDC.............................................................................9
6.1) Frequency Control....................................................................................................................9
6.2) Voltage Control.........................................................................................................................9
6.3) Line loading............................................................................................................................10
6.4) Operating manpower...............................................................................................................11
7) COMPONENTS OF SCADA...............................................................................11
7.1) Transducers.............................................................................................................................11
7.2) Potential Transformers and current Transformers..................................................................12
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7.3) Remote Terminal Unit (RTU).................................................................................................13
7.4) MODEM.................................................................................................................................18
7.5) Power Line Carrier Communication (PLCC).........................................................................19
7.6) FRONT END PROCESSOR..................................................................................................20
7.7) COMMUNICATION BETWEEN SERVER AND RTU:.....................................................20
8) DATA DISPLAYS....................................................................................................20
8.1) Sources & types of Data.........................................................................................................23
9) COMMUNICATION MEDIA...............................................................................25
10) SYSTEM CONFIGURATION..............................................................................25
10.1) RSCC hardware Subsystems description................................................................................27
10.2) Communication Front-Ends....................................................................................................28
10.3) ICCP servers...........................................................................................................................30
10.4) ISR servers..............................................................................................................................31
10.5) DTS server..............................................................................................................................33
10.6) Development server................................................................................................................34
10.7) Operator consoles...................................................................................................................34
10.8) DTS operator consoles............................................................................................................36
10.9) Network Management console...............................................................................................36
10.10) Development Console.............................................................................................................36
10.11) LAN and WAN equipment.....................................................................................................36
10.12) Remote VDUs.........................................................................................................................37
11) SCADA SUBSYSTEM............................................................................................38
11.1) Functional overview................................................................................................................38
11.2) Data acquisition.......................................................................................................................39
11.3) Host SCADA..........................................................................................................................39
11.4) Telemetry Front End...............................................................................................................40
11.5) Communication Front End......................................................................................................40
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11.6) RTU........................................................................................................................................40
11.7) Data flow.................................................................................................................................42
11.8) External data...........................................................................................................................42
11.9) Data processing.......................................................................................................................42
11.10) Data quality checking.............................................................................................................44
11.11) Supervisory control.................................................................................................................45
12) USER INTERFACE MANAGEMENT SYSTEM...........................................46
12.1) Menu Directory display..........................................................................................................47
12.2) System Directory display........................................................................................................47
12.3) Transmission System Overview display.................................................................................47
12.4) Interchange displays...............................................................................................................48
12.5) Substation Graphic Displays Menu display............................................................................49
12.6) Transmission Line Graphic Displays Menu display...............................................................49
12.7) Transmission Line Graphic display........................................................................................49
12.8) Abnormal summary display....................................................................................................50
13) HISTORICAL INFORMATION AND MANAGEMENT............................50
14) UTILITIES USED BY SCADA SYSTEM.........................................................52
14.1) Alarms: -.................................................................................................................................52
14.2) Tagging: -................................................................................................................................52
14.3) Trending: -..............................................................................................................................53
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1)1) INTRODUTION
Power Grid Corporation of India Ltd. has implemented the Unified Load Dispatch &
Communication Project for all the constituents of Northern Region and central sector. Under
this project computerized SCADA/ EMS (Supervisory Control & Data Acquisition/ Energy
Management System) has been installed at SLDC Patiala and two Area Load Dispatch
Centers (ALDCs) at Lalton Kalan (Ludhiana) and Jamsher (Jalandhar). 19 Nos. Remote
Terminal Units (RTUs) have been provided by PGCIL itself under this scheme.
PSEB has already implemented Interim SCADA scheme provided by M/s C-DAC
Bangalore, through which on line data is available at SLDC Ablowal from 15 Nos. RTUs
since 1997-98. On line data with NRLDC is also being exchanged through this scheme. 6
Nos. additional RTUs have recently been provided by PSEB. Thus in total data from 40
Nos. important Sub-Stations and Generating stations of PSEB are available for online
monitoring and Energy Management through SCADA/ EMS system at SLDC Patiala and at
the ALDCs.
From Remote Terminal Units to control center connectivity PLCC, Fiber optics &
Microwave communication network is used, whereas for inter control center connectivity,
wide band trunk line Microwave system is used.
2) ABOUT SLDC (PATIALA)
Power Grid of India Ltd is implementing the unified load DESPATCH &
communication project. For all the constituents of Northern Region & central sector projects
under World Bank funded scheme. Under this project SCADA/EMS (Supervisory Control
& Data Acquisition/Energy Management System) has been installed at SLDC Patiala & two
ALDCs (Area Load DESPATCH Center) at Lalton Kalan (Ludhiana) & Jamsher
(Jalandhar). 19 numbers of Remote Terminal Units are being provided by PGCIL itself
under this scheme.
PSEB has already implemented interim SCADA scheme provided by the M/S C-
DAC Bangalore, through which on line data is available at SLDC Ablowal from 15 nos.
RTUs since 1997-98. Online data with NRLDC is also being exchanged through this
scheme. 6 nos. additional RTUs are being provided by PSEB, thus total data from 40 nos.
important substations & generating stations of PSEB shall be available for monitoring &
Energy Management through SCADA/EMS system at SLDC Patiala.
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3) WHAT IS SCADA SYSTEM?
In the late 1960s and early 1970s SCADA came into existence. SCADA
stands for “Supervisory control and Data acquisition”. This system is
responsible forgathering, processing and displaying information about the state
of monitoring system. From a SCADA control center, operates and application
programs can oversee and change the operating state of monitored devices. It
enables operators to control field devices for their consoles. The system must
be able to acquire & present large amount of data securely, clearly &
coherently so that an operator can make appropriate decision. Thus both
current live data and list data is required here.
In a limited sense, the concept implies a remote controlling station,
which monitors & controls system situated at some distance, in the field of
electrical transmissions and distance networks i.e. multiple substations being
controlled from the control room. In the multi site system, one site is usually
designated as host site, while other are called remote or foreign sites. Host site
is the recipient of data transferred from remote sites. Each site communicates
to its remote terminal units by way of phone lines, microwave or fiber optic
cable.
At the control site, SCADA usually runs on computers. One performs
real time function i.e. gathering, processing and displaying of real time data.
This system is known as primary. The other computer acts as a backup and
referred as secondary. If primary computer fails it take over real time
operations.
3.1) SUPERVISORY CONTROL
SCADAs supervisory control function allows the operator and application
Programmer to control devices in the monitored systems. From the control
center the SCADA operator can issue control commands to change the state of
such devices as circuit breaker and switches.
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3.2) DATA ACQUISITION
Data Acquisition means to collect data and manipulate it or scanning of
data. Remote terminal unit sends the raw data to communicate the front ends
which perform some conversion and checking on the data before sending it to
the telemetry front end and thus to the host.
SCADA performs the following functions to acquire data for devices in the
monitored system:
1) Scan the monitored system at prescribed tomes and receive data from
RTU via CFE (Communication Front End).
2) Perform calculations on the data for other applications programs.
3) Determine the quality of data.
4) SCADA can acquire process and display data from three types of devices
in the monitored system. These device types are:
a) Analog state devices are used for numerical measurement such as
MW, MVAR etc.
b) Status devices have two conditions such as on and off such as
circuit breakers, isolators.
c) Pulse accumulator devices are used for measurement of energy.
4) MAIN FEATURES
The project involves the following main features:-
1) Establishment of a Computer based control center for SCADA/ EMS function at
Patiala (SLDC) and two Area Load Dispatch Centers (ALDCs) at Lalton Kalan
(Ludhiana) and Jamsher (Jalandhar).
2) On-Line acquisition of data viz. MW, MVAR, Direction of Power Flow, Voltage,
Frequency from 40 nos. stations including most of the Generating Stations situated
within Punjab state (List Enclosed)
3) Acquisition of Digital status of all circuit breakers, isolators, tap changers &
Sequence of Event (SOE) recording covered under the scheme.
4) On-Line display at SLDC & ALDCs on Operator Consoles and Magnified Video
Projection Screen at SLDC Patiala.
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5) Provision of Remote Video Display Unit for Head Office for Board Management
reporting purpose.
6) On line acquisition of weather data for load forecasting through a weather station
installed at SLDC
7) Control Operation from remote Control Centers on selective lines/ transformers as
and when required meeting the power system demand.
5) LIST OF GRID SUB STATIONS AND THERMAL/HYDRO
GENERATING STATIONS COVERED UNDER SLDC PROJECT
A) Under Interim SCADA Scheme:
Generating Stations:
1) 220kV sub-station at Ropar Thermal (GGSSTP) Power Station.
2) 220kV sub-station at Bathinda Thermal (GNDTP) Power Station.
3) 132kV sub-station at Shanan Hydel Power House (Joginder Nagar, HP).
4) 132kV sub-station at Anandpur Sahib Hydel Power House No. 2.
5) 132kV sub-station at Mukerian Hydel Power House No. 2.
6) 132kV sub-station at Mukerian Hydel Power House No. 4.
Sub Stations:
7) 220kV Ablowal, Patiala.
8) 220kV Lalton Kalan, Ludhiana.
9) 220kv Jamsher, Jalandhar.
10) 220kV Moga.
11) 220kV Malerkotla.
12) 220kV Gobindgarh-1.
13) 220kV Sarna.
14) 220kV Wadala Granthian.
15) 220kV Mohali.
B) Under Unified SCADA Scheme:
Sub Stations:
16) 220kV Sultanpur.
17) 220kV Patti.
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18) 132kV Verpal.
19) 220kV Verka.
20) 220kV Civil Lines Amritsar.
21) 132kV Batala.
22) 220kV Butari.
23) 132kV Bhogpur.
24) 132kV Mahilpur.
25) 220kV Dasuha.
26) 220kV Goraya.
27) 220kV Nawashahar.
28) 220kV Muktsar.
29) 132 kV Muktsar.
30) 220kV Dhandari Kalan.
31) 220kV Ferozepur.
32) 220 kV Sunam.
33) 220kV Barnala.
34) 220kV Gobindgarh-2.
C) Additional Stations Covered:
Generating Stations:
35) 220kv sub-station at Guru Hargobind Thermal Power Station, Lehra Mahobbat.
36) 220kV sub-station at Ranjit Sagar Hydel Power Plant, Thein (near Pathankot).
37) 132kV sub-station at Anandpur Sahib Hydel Power Plant-1.
Sub Stations:
38) 132 KV Substation, Pathankot.
39) 220 KV Substation, Rajpura.
40) 220 KV Substation, Mansa (near Bathinda).
41) 220 KV Substation, Jagraon (near Ludhiana).
42) 220 KV Sub station, Sahnewal (near Ludhiana).
43) 220 KV Sub station, FatehGarh Churian (near Amritsar).
44) 220 KV Sub station, Kartarpur (near Jalandhar).
45) 220 KV Sub station, Nakodar (near Jalandhar).
46) 132 KV Sub station, Chohal (near Hoshiarpur).
11
47) 132 KV Sub station, Kangra (H.P.).
48) 132 KV Sub station, Sarna (near Pathankot).
6) MAIN OPERATION OF SLDC
One of the main assumptions of the power system planner is that the system
parameters viz. frequency, voltage remains close to nominal values. This section lists the
measures to be adopted by the system operators at SLDCs / ISGS / substations for frequency
and voltage control.
6.1) FREQUENCY CONTROL
All the regional constituents would make all possible efforts to ensure the
maintenance of grid frequency within the normal band i.e. 49.0 to 50.5 Hz. This would be
ensured by adhering to the following steps:
1) Each SLDC shall regulate the load / own generation under its control so that it may
not draw more than its net drawl schedule during low frequency conditions and less
than its drawl schedule during high frequency conditions.
2) Sudden reduction in generator output by more than one hundred (100) MW unless
under an emergency condition or to prevent an imminent damage to the equipment
shall be avoided, particularly when frequency is falling below 49.0 Hz.
3) Sudden increase in load by more than 100 MW by any SLDC, particularly when
frequency is falling below 49.0 Hz. and reduction in load by such quantum when
frequency is rising above 50.5 Hz. shall be avoided.
6.2) VOLTAGE CONTROL
As defined in the IEGC section 6.2 (g), the operating range of the voltage at various
voltage levels of grid are as follows:
Voltage in KV (RMS)
Nominal Maximum Minimum
400 420 360
220 245 200
132 145 120
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The maximum and minimum values in the above table are the outer limits and all the
constituents would endeavor to maintain the voltage level well within the above limits.
1) In the event of high voltage (e.g., 400kV bus voltages going above 410kV), the
following specific steps would be taken by the respective grid substations /
generating station at their own, unless specifically mentioned by NRLDC otherwise;
a) The bus reactors be switched in
b) The manually switchable capacitor banks be taken out
c) The switchable line/ tertiary reactors be taken in
d) Operate synchronous condensers for VAR absorption
e) Operate hydro generators / gas turbines as synchronous condenser for VAR
absorption wherever possible
f) Opening of the lightly loaded lines in consultation with NRLDC, keeping in
view the security of the balance network.
2) In the event of low voltage, (e.g., 400kV bus voltages going down below 390kV),
the following specific steps would be taken by the respective grid substations /
generating station at their own, unless specifically mentioned by NRLDC otherwise;
a) The bus reactors be switched out
b) The capacitor banks be switched in
c) The switchable line / tertiary reactors be taken out
d) Operate synchronous condensers for VAR generation
e) Operate hydro generators / gas turbines as synchronous condenser for VAR
generation, wherever possible
f) Closing of lines which were opened to control high voltage, in consultation
with NRLDC
6.3) LINE LOADING
In addition to frequency & voltage control measures outlined above, each system
operator would also have before him the thermal loading limits, surge impedance loading
and the loading permitted from stability considerations for each line listed under important
elements. Each system operator at SLDC / substations would endeavor to keep the line/ ICT
loadings within limits and inform NRLDC in case of overloading of any element. Special
emphasis would be paid by each system operator in identifying credible system
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contingencies & continuously evaluating the system under his control against these
contingencies.
6.4) OPERATING MAN POWER
The control rooms of all SLDCs, power plants, grid substations as well as any other
control centers of regional constituents shall be manned round the clock by qualified and
adequately trained manpower who would remain vigilant and cooperative at all the times so
as to maintain the system safety and security and operate it in a most optimum manner.
7) COMPONENTS OF SCADA
The SCADA system used in the SLDC project consists of:
1) Transducers
2) Potential and Current Transformers
3) Remote Terminal Unit (RTU)
4) MODEM
5) Power Line Carrier Communication (PLCC)
6) Front End Processor
7) LAN
8) Main Server
7.1) TRANSDUCERS
Transducer is a device, which provides a transformed output in response
to a specific measured value given as input.
The basic functions of transducer are:
1) To measure/ to sense the change in parameters.
2) To convert the measured values from one form into another form, that is
useful for further processing.
Depending on the type of the output from the first function, the conversion function
(i.e. conversion into engineering units) may or may not be present. The various
parameters involved in the Power System analysis are: -
1) Active power
2) Reactive power
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3) Voltage
4) Current
5) Status of circuit breakers
Out of these the current and the voltage are stepped down to a value
suited to the respective transducers. The status of the circuit breakers are
sensed using energized relays connected to either the OPEN or CLOSE position
of the circuit breaker. While selecting a transducer for any specific measuring,
one should consider the following criteria.
Type of measuring
1) Number of measurements
2) Sensing element
3) Transduction element
4) Range of measurement
The Conversion is a process, which involves presentation of measured
value in a specific format to the user. They convert the analog input to digital
input to be interfaced to the computer directly. The Transducer Panel at SLDC
has 11 Transducers, out of which 8 are the main Transducers and 2 are voltage
Transducers, and one is frequency Transducer. The main Transducer consists of
4 CTs (only R & B phases), 3 PTs, 1 neutral point, 1 earth point, 2 points for
dc supply (48 V, to energize the T/D), 2 points of Ms, and 2 points for MVARs.
15
7.2) POTENTIAL TRANSFORMERS AND CURRENT
TRANSFORMERS
Instrument transformers find a wide application in protection circuits of
power system for the operation of over current, under voltage, earth fault and
various other types of relays. In all these applications the instrument
transformers are used for scaling down the values to an acceptable range. As in
power system, current & voltage handled are very large and therefore the direct
measurement of these quantities is not possible using measuring devices.
Transformers used for the measurement of voltage are called potential
transformers. The primary winding is connected to the voltage being measured
and the secondary winding, to a voltmeter. The PT steps down the voltage to
the level of voltmeter specification used in the project. Here this is 110 KV/
110V.
Transformers used for the measurement of current are called current
transformers. The primary winding of a current transformer is so connected
that the current being measured passes through it and the secondary winding is
connected to an ammeter. The CT steps down the current to a lower level. The
current transformer is used with its primary winding in series with the line
carrying the current to be measured and, therefore the primary current is
dependent upon the load connected to the systems and is not determined by the
load connected on the secondary winding of the CT. The primary winding
consists of very few turns and therefore, there is no appreciable voltage drop
across it. The secondary winding of the CT has large number of turns, the exact
number being determined by the turn’s ratio. The ammeter or wattmeter current
coil is connected directly across the secondary winding terminals.
current transformer a) wire lead b) split core
frequency – 50 -400 hz
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Thus the CT operates with its secondary winding nearly under short
circuit conditions. On the terminal of the secondary winding is earthed so as to
prevent damage to the equipment and personnel in the vicinity in the event of
insulation failure in the CT. Specification used in the substation is 230 KV/
110 KV. The output of PT should be zero when the supply is zero. In order to
nullify the output when the supply is zero, auxiliary supply is used.
Specifications used at SLDC are 600 KV/ 1000 KV.
7.3) REMOTE TERMINAL UNIT (RTU)
Typical RTU has a network interface (usually either Ethernet,
proprietary, or both), a simple processor, some environmental sensors, some
override switches, and a bus, which it uses to communicate with devices and/or
interface, boards. This bus is sometimes called a device bus or a field bus.
Standards include the ISO Controller, Area Network, MODBUS, and others.
Sometimes a device or field bus standard can be used to interconnect RTUs and
host systems as well as field devices and RTUs.
17
RTUs are basically distributed SCADA based systems used in remote
locations. They are rugged and should be able to work unattended for a long
duration. There are two modes in which RTUs work:
i. Under command from central computer.
ii. Stand alone mode.
Since these RTUs have to operate for a long duration unattended the
basic requirements would be that they consume minimum power and have
considerable self-diagnostic facility. The main parts of RTUs are:
MAJOR COMPONENT OF SCADA REMOTE TERMINAL UNIT
The RTUs consist of process module, analog and digital input modules and
communication interface, power supply unit and screw termination on the rear of the panel
for field connections. The data is acquired form various stations with the help of RTUs.
The various parameters, which are to be acquired, are first taken from the sub
station/generating station through current transformer and potential transformer and
brought to the control room in the control panels. From these control panels the
connections are taken and given to the transducers, which lower down the energy levels of
the signals. These signals are of two types- digital and analog. RTU support data
transmission at the rate of 50 to 9600 bits per sec.
The basic functions of RTU are:
1) Collect power system data
2) Filter and process the system data
3) Transmit data to control center
4) Receive the control commands
HARDWARE
The general arrangement of sub-system inside the RTU panel is given in figures.
All the sub-systems have been designed in standard 19” rack. The sub systems are
modulated in construction facilitating easy maintenance.
The power supply unit is placed at the top of the panel. The Circuit breakers with
indication lamps are provided for 230V, 48V DC and 24V DC power supplies. A fan tray
is provided below the power supply unit. The 6U rack containing the processor and I/O
module is placed below the fan tray. The 6U rack has a motherboard, which can
accommodate up to 12 I/O modules in addition to processor module (PCU). The sub rack
consists of following hardware modules:
18
1) Process control unit (PCU)
2) Digital input card (DI)
3) Analog input card (AI)
19
FRONT VIEW OF RTU
20
1) PROCESS CONTROL UNIT (PCU)
The PCU module contains a powerful 32-bit processor (CPU), memory, serial
channel interfaces and I/O bus interface. The processor T805 has a built in 64-bit Floating
Point Unit (FPU), 4K bytes of on-chip RAM, 32 bit timer and a micro coded scheduler.
The processor supports multiple CPUs to be connected through links in case higher
computing power is required. Provision has been made to add processor modules in the
TRAM sockets of the PCU board.
The board has 2Mbytes of EPROM to store the program for scanning, limit
checking and engineering unit conversion. It has 4Mbytes of static RAM for storing the
data.
The board supports 4 serial channels, which can be configured as RS232/422/485
to facilitate multi-master communication. It has a real time calendar clock circuit providing
timing for time stamping.
SPECIFICATIONS
1) T805 32 bit CPU with 64-bit Floating Point Unit (FPU).
2) 2MB EPROM.
3) 4MB RAM (Static).
4) Real time calendar clock.
5) 2- RS 232C ports for communication to the master stations.
6) 1-RS 485 / RS 422 port for communication to the console.
7) 1-RS 485 port.
8) 1 parallel port for printer.
9) Power requirements: 5V, 3A.
10)Board size: 220mm x 233.5mm.
2) DIGITAL INPUT CARD
The digital input modules have fully isolated 16 channel digital inputs. All inputs
are protected against high voltage surges. Constant over voltage protection is provided for
all inputs. Input noise suppression and filtering allows reliable operation in hostile
conditions. Galvanic isolation of the field signals from the logic circuitry is obtained
21
through the OPTO couplers. A ground line running through the center of optocouplers on
both sides of the PCB physically separates the field bus from the logic circuits and the
front bus. This protects the rest of the systems in case any hazards occur in high field
circuitry. The block diagram is given in figure.
LED indication is provided on the front panel for each channel. It lights on a high
input to the respective channel. The detail of the front panel is given in front panel
diagram.
The processor can access any of the 16 channels through the front I/O bus.
3) ANALOG INPUT CARD
The 16 channel isolated analog input module is a complete fully isolated input
system containing 16 different channels on a 6U Euro board. It is ideal for industrial
applications requiring measurement of non-isolated transmitter signals in the presence of
high common mode voltages and ground loop noise. Each input channel consists of a
highly reliable flying capacitor multiplexer utilizing mercury wetter/dry read relays. These
input channels feed a stable instrumentation amplifier and conversion is accomplished by a
12 bit A/D converter. The result is an input signal having noise immunity up to 100CMV
(Common mode Voltage).
The board accepts 16 channel of analog signal as its input. Depending upon the
particular channel selected, it provides an equivalent 12 bit digital data as output. The
block diagram is given in figure.
The signals are connected to the font D 37 female connecter of the board. When the
board and a particular channel are selected, all the relays are actuated. The capacitor,
which was connected to the selected relay, will now be connected to the input by the
multiplexer ADG508. The change over contacts thus provides necessary isolation during
analog to digital conversion. The output of INA is fed to the input of ADC, which operate
at 0-10V range. The ADC converts this0-10V to its equivalent digital value and store it in
a buffer inside ADC.
COMMUNICATION THROUGH MODEMS:
The Communication at SLDC is possible in two ways:
1) Communication Media like PLCC microwave.
2) Modem
Here I am explaining the Communication through Modems.
22
7.4) MODEM
The term MODEM is an acronym for Modulator-Demodulator. The primary
modem function is to convert digital data into analog form, which is suitable for
transmission on common carrier circuits. Modulation is the D/A conversion in which the
digital data is placed on the transmission line by modulation of a tone or carrier
Demodulation is the reverse process. In a data communication system, transmitting and
receiving modems are necessary at each end of the analog transmission line. The output
transmitting circuits and receiving circuits are networks required for transmitting and
receiving analog information to and from the transmission line.
Three modulation techniques are commonly used:
1) Amplitude modulation
2) Frequency modulation
3) Phase modulation
Modems operate with one functioning as an originate unit and the other as an answer
unit. The originate modem transmits on a low frequency channel, using 1.27 KHz for a mark
and a 1.07 KHz for a space. It receives on a high frequency channel using 2.225 and 2.025
KHz respectively for a mark and space. The answer modem transmits on the high frequency
channel and receives on the lower frequency channel. The timing circuit provides the basic
clocking information for both the transmission as well as reception of signals. A crystal
oscillator to within about 0.05% of the normal value usually controls the internal timing.
Modem is used to adjust the output level of data the computer data is converted to
analog waveforms as carries and this composite signal passes through our common
telephone lines to reach the destination, where the carriers is removed and the original data
is given to the computer. Modems are generally used to convert various nodes of data
network. This is connected between computer and telephone lines, in the information
technology industry, computer is known as data terminal equipment (DTE) and modem is
known as data communication equipment (DCE). Modems are classified by their data rates
or by V. (V.DOT) standards. Modem data rates are the number of bits transferred per second
over the communication line. It does not refer to the data rate at which DTE communicate
with DCE.
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7.5) POWER LINE CARRIER COMMUNICATION (PLCC)
Carrier current provides a means of conveying speech; metering indications, control
impulses etc. from one station to another by existing transmission lines without interfacing
with their normal function of transmitting power. The main elements of carrier channel are
sending terminal assembly including line matching and tuning, a coupling capacitor,
receiving station coupling, terminal assembly and the power line.
1) COUPLING CAPACITOR
Coupling capacitor is the most widely used for coupling means. The typical units
range in voltage and capacitance from 46 KV, 0.015 micro farads to 765 KV, 0.004 micro
farads. The capacitor is mounted on a metal base to provide convenient installation and
space for connection to its lower terminal. The base contains 60 Hz drain coil and may also
contain protective gaps, grounding switches and a part or the entire coupling network.
2) LINE TUNING
Line tuning is required to tune out the reactance of a capacitor with a suitable
inductance; the simplest application involves the coupling of a single frequency between a
single line conductor and ground using a single coupling capacitor. It provides an efficient
path for coupling the carrier signal to the line conductor.
Carrier terminal with it co-axial is matched to the impedance of the power line by an
adjustable impedance matching transformer. Impedance matching of the transmitter,
receiver and the transmission line is required to allow maximum transfer of energy.
Therefore where there is more than one transmitter coupled to the line at a common
point there should be a resonant path for each frequency. The practical Upper limit of
resonant tuning is two frequencies. Above this, broadband tuning provides a most
satisfactory solution. Where future expansion is expected, it may be preferable initially to
design the circuit with broadband tuning, since a reasonable number of additional carrier
circuits may then be introduced at any time without disturbing the existing circuits.
3) LINE TRAPS
Line Traps are used to make the transmission line appear as simple two terminal line
used in telephone circuits. They direct the carrier wave over a given circuit, increase the
efficiency, smoothes the frequency characteristics, minimize the interference, prevent the
interruption of the communication channels when the ground switches are closed, block off
he supply lines and allows the transmission during a nearby external fault.
4) ATTENUATION
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Attenuation is the measure of the loss of energy between the transmitting and the
receiving terminals and depends upon many factors like frequency, conductor size and
spacing, line configuration, presence of ground wires or parallel circuits, transpositions,
ground sensitivity and weather conditions. The type of coupling used and the phase to which
it is applied affects the total attenuation from terminal to terminal.
7.6) FRONT END PROCESSOR
1) COMMUNICATION FRONT END
The communication equipment and software that links the computer to RTUs is
referred as communication front end. One RTU is located at the site and other at the
remote station.
Functions of CFE: it drives the serial communication lines connected to the RTUs.
The CFE hardware configures consists of Ethernet controller’s card several serial
communication cards. The number of communication card depends on the number of
RTUs connected to where each card can support up to16 communication lines with RTUs.
2) TELEMETERED FRONT END
The software that communicates between the data server and CFE is called
telemetric front end. In addition to this, TFE also maintains information regarding the
configuration of the communication components and facilitates interfacing with devices
having a variety of communication protocols.
7.7) COMMUNICATION BETWEEN SERVER AND RTU
In SCADA system, each control site has two host computers. There will be two
redundant TFEs, which will both be in communication with operational SCADA. Each
telemetry front end and communication front end functions as independent unit. Host
computer will continue scanning. The host may switch communication from one path to an
alternate path that is on another CFE or TFE without requiring a host failure. The CFEs
communicate with RTUs and performs several functions to minimize data processing on
the host computer.
8) DATA DISPLAYS
There are two types of displays:
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1) Online Display
2) Tabular Display
In a one line or single line display whole network is made up of single
lines and graphical symbol are used for different components. One-line
diagrams give the current state of the operating devices and also give on line
data. We can give command from one line diagram to control the state of the
devices and can change the way of displaying the data.
ONLINE DISPLAY
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Tabular display also gives the state of the operating devices and current
data. But in this case information is in the tabular form i.e. in the form of rows
and columns. Tabular usually contains more information the one line displays.
TABULAR DISPLAY
8.1) SOURCES & TYPES OF DATA
Each piece of data that SCADA acquires has a source from which it is
normally acquired. The normal source of data is the RTU. However, SCADA
may also get data from another SCADA site, a calculation, an operator entry or
another process eternal to SCADA system.
The system has three different types of data:
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1) ANALOG DATA
Analogs are numeric values representing the state of variable-state
devices, such as power lines, transformers and pumps. Analog measurements
are stored in analog records. In the monitored system a transducer usually
measures a physical variable and the output of transducer is passed through an
analog to digital converter in the RTU. The A/D converter produces a number
that the host computer can process. All analog values are converted to host
computer floating-point numbers and adjusted by the host computer to
represent the physical measurements in MWs
For example: Voltage and Current.
2) STATUS DATA
Status values represent the state of discrete state devices, such as C.Bs,
tap changers and valves. SCADA can accept I/Ps represent a simple on/off or
Open /closed input, or a combination of inputs from a three-state device. All
status point values are stored in POINT records in the SCADA database.
For example: Status change of Circuit Breaker.
3) COUNT DATA
A count measurement is a value from pulse accumulator. Pulse
accumulators are often used to measure the total amount of energy, liquid or
gas that has passed by a specific location in the monitored system. The
detection device alternately opens and closes a contact each time a unit of the
measured matter passes by it. The pulse accumulator counts the contacts
changes and passes the count to SCADA, which stores the total accumulation
of counts since the last time the count was reset.
For example: MWH.
DATA QUALITY
Data quality is a catch all term relating to information the SCADA
operator may want to know about the values SCADA is displaying for
monitored devices. So to provide the operator with answers of certain
questions, SCADA has five groups of data quality indicators:
1) Data source flags
2) Detailed data quality flags
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3) Composite data quality flags
4) State estimator flags
5) Data attribute flags
9) COMMUNICATION MEDIA
The data is required from various stations with the help of RTU. The
various parameters, which are to be acquired, are first taken from the
substation/generating station through current transformers and potential
transformer and brought to the control room in the control panels. From these
control panels the connections are taken and given to the transducers, which
lower down the energy levels of the signals. These signals are of two types-
analog and digital. Analog signal comprise of voltage, current, frequency,
active power and reactive power while digital signals are the circuit breaker
position, isolators position and tap changing position. Analog and digital
signals are given to the digital and analog cards. These analog signals are then
converted in to the digital signals. Finally these signals are fed to the modem
and transmitted. This transmission can be done in number of ways such as PLC
and VSAT depending upon the distance and Economy involved.
VSAT - Very Small Aperture Terminal, Communication through antenna.
PLC - Power Line Communication
MICROWAVE - Communication through Satellite.
FIBER OPTICS – Communication through Co-axial cables
10) SYSTEM CONFIGURATION
The purpose of this presentation is to introduce the hardware composing the
SCADA/EMS system for the Northern region. The presentation is made only to the extent
necessary to understand the functioning of the system, and in particular to detail the major
hardware subsystems and the functions assigned to each. The complete and detailed
information on hardware configurations are described in the release C of the document
‘Hardware Configuration for all control centers (ref. NR-A/N-G00-1-A05)’.The hardware
configuration overview is presented successively for each level of the Northern Region
SCADA/EMS hierarchy:
1) RSCC system configuration.
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2) SLDC systems configuration. Minor differences existing between the SLDCs are
also introduced here.
3) Sub-LDCs and CPCC systems configuration.
The distributed hardware configuration of the RSCC SCADA/EMS system includes
the following subsystems:
1) The SCADA/EMS servers that support the following system functions (SCADA,
Real-time Dispatching, Power System Analysis and Operation Scheduling
functions). The SCADA/EMS servers operate in a primary-standby relationship for
redundancy purposes. SCADA/EMS software is active only on the application server
assigned the primary role.
2) The Communication Front-ends that drives the serial communication lines
connected to the RTUs.
3) The ICCP (Inter-Control centres Communications Protocol) servers that support
intersite exchanges with the SLDCs and the CPCC.
4) The ISR server that is used to perform Information Storage and Retrieval functions.
The ISR servers also operate in a primary-standby redundancy.
5) The DTS (Dispatcher Training Simulator) server and its associated DTS
operator consoles that provide the dispatcher’s training capability.
6) The Development Server and its associated development console that provide
software utilities used to develop and maintain the SCADA/EMS software, displays
and databases.
7) The Operator consoles that handle the man-machine interface for system control
and supervision operations.
8) The Network Management Console that provide the Configuration management,
fault management and performance monitoring capabilities.
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9) The WAN routers, in a redundant configuration, that allow several connections with
the other Northern Region control centres (SLDCs and CPCC) and with the Remote
VDU (Video Display Unit) located in PGCIL Headquarters.
10)The Peripheral equipment such as printers, Video projector, satellite time receiver
system, CD/ROM servers. This architecture is presented in the following schematic
diagram:
RSCC HARDWARE CONFIGURATION OVERVIEW
10.1) RSCC HARDWARE SUBSYSTEMS DESCRIPTION
The RSCC hardware subsystems are interconnected through a high-speed (100 Mbps
between the SCADA/EMS servers and 10 Mbps between all other equipments) Local Area
Network (LAN) that uses a dual Ethernet as the interprocessor backbone.
The state of all hardware subsystems is monitored and reported to the configuration
management utility running on the real-time SCADA/EMS servers. This utility provides
synthetic displays that give an instantaneous view of the state of the overall hardware
system. For maintenance purpose, manual failovers can be initiated from these displays by
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supervising staff. The way monitoring is performed vary according to the hardware type. A
node state for example can be determined by periodically checking that it can respond to a
network (DECNET or TCP/IP) request.
The following section details the hardware components of each subsystem:
1) The real-time SCADA/EMS servers form the central core of the system. They
consist of two high performance Digital 64-bit RISC based AXP machines (“Alpha
servers”) in a dual redundant configuration (Primary and Stand-by). Only one of the
two is required to be operational in order for the subsystem functions to be
operational. The configuration management utility is running on those SCADA/EMS
servers. The failure of one of the two servers is immediately detected. If the failed
machine had the primary role, the configuration management utility notifies the
SCADA/EMS applications on the standby server to assume the primary role, and the
standby becomes the primary server.
2) Each SCADA/EMS server is configured with 512 Mbytes of main memory.
3) Application servers use SCSI (Small Computer System Interconnect) disks. Total
Disk capacity is 12 Gbytes (4 GB + 4 GB + 4 GB) per server.
The disk storage is allocated as follows:
1) System disk. This disk contains the OpenVMS operating system files.
2) Backup of global sections. The EMP databases are resident in host CPU memory as
global sections and exist on disks as global section backing files. In addition, they
are duplicated by data transfers using the EMP BACKUP utility to the standby
server (see after).
3) Files - they store non-HABITAT database data (such as historical data, snapshots of
application databases - also called savecases, display definitions and executable
code).
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10.2) COMMUNICATION FRONT-ENDS
The RTU communication function is handled by two Communication Front Ends
(CFEs) linked to the SCADA/EMS servers through the Ethernet LAN.
The CFE hardware configuration consists of a VME chassis containing an Ethernet
controller card and several serial communication cards from Performance Technology
Incorporation (PTI). The chassis is connected to the local area network via the Ethernet
controller card so that TCP/IP can be used to communicate between the Communication
Front End and the chassis.
The CFE communication cards contain an intelligent communication processor. On
each card there are serial I/O ports for communication with RTUs. They handle requests and
responses at the bit and byte level, doing checks and converting responses into a protocol
independent form and passing them to the SCADA/EMS server. A single request from the
SCADA/EMS server can cause the CFE to scan all its communication lines, check for
changes in the reported data, and report back the results.
The number of communication cards depends on the number of RTUs to connect.
Each card can support up to 16 communication lines with the RTUs. The RSCC will need
three communication cards per CFE.
The standard time Interface to the supplied GPS clock for the RTU synchronisation
is provided by a True Time VME bus card installed in the VME chassis, with the IRIG-B
protocol.
The IRIG time codes are a group of rate-scaled serial time formats containing up to
three coded expressions. The first is time-of-year in Binary Coded Decimal (BCD) and
includes days, hours, minutes, seconds, tenths of seconds, and hundredths of seconds. The
second is a set of elements reserved for encoding various identification, control and other
specific functions. The third is a time-of-day code word in Straight Binary Seconds (SBS).
The IRIG time code formats are serial, width modulated codes which can be in either DC
level shift or amplitude modulated (AM) form.
IRIG format B, Signal B000, is mainly composed of:
1) Frame reference marker
2) Binary coded decimal time-of-year cod word (30 bits)
3) Control functions (27 bits)
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4) Straight binary time-of-day code word (17 bits).
Failures of the Communication Front End or of a communication line appear as
communication errors on a particular path to one or multiple RTUs. When any component in
the communication path to an RTU fails, SCADA assigns scanning of the RTU to any other
alternate path available, using if necessary the other Communication Front End .
Each serial port (V24/V28) on each Communication Front End is directly connected
to the data communication network equipment. Each communication line may be accessed
from two different Communication Front Ends. The following schema presents RTUs
connexion to the CFE, for each type of communication link.
DATA COMMUNICATION NETWORK INTERFACE OVERVIEW
Since the communication network is not part of the scope of this contract, it is not
described in this document.
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10.3) ICCP SERVERS
The ICCP servers are used to handle the inter-centre communications functions with
the SLDCs and the CPCC. ICCP servers operate in a master/standby relationship similarly
to real-time SCADA/EMS servers. Data preservation under failure conditions is insured by
the EMP BACKUP utility.
Two Digital DPWau workstations with 128 Mbytes of RAM and 4 Gbytes of disk
storage are used to ensure a redundant configuration.
Each ICCP server is equipped with a CD-ROM drive, and a Digital Audio Tape
(DAT) drive which allows backup/restore operations.
One processor terminal is delivered with each ICCP server. This processor terminal
is a 15” colour monitor, with dedicated keyboard and mouse.
ICCP SERVERS
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10.4) ISR SERVERS
The ISR servers are used to perform historical data archival and data retrieval
functions. Data sampling is performed from the real-time SCADA/EMS servers. A link is
automatically established between the Primary SCADA/EMS server and the Primary ISR
server when the ISR function is initialised. In the case when a failover occurs, either
between the SCADA/EMS servers or between the ISR servers, the data link is automatically
re-established between the two primary servers.
The ISR servers consist of two high performance Digital 64-bit RISC based AXP
machines (“Alphaservers”) in a dual redundant configuration (Primary and Stand-by). They
are configured in a cluster using the Small Computer System Interconnect (SCSI). SCSI
provides shared storage between the two ISR servers. Only one of the two ISR servers is
required to be operational in order for the subsystem functions to be operational.
Each ISR server is configured with 256 Mbytes of main memory.
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OVER VIEW OF OTHER EQUIPMENTS
The disk configuration for the redundant ISR servers is:
1) One local 4 Gbytes system disk for each server
2) Six 4 Gbytes data disks in a RAID-1 configuration shared by the two servers,
offering a redundant disk capacity of 12 Gbytes per ISR server.
Each data server is equipped with a CD-ROM drive, and an Digital Audio Tape
(DAT) drive which allows backup/restore operations.
One processor terminal is delivered with each ISR server. This processor terminal is
a 15” colour monitor, with dedicated keyboard and mouse.
In addition to the storage capacity detailed above, the ISR servers are also equipped
with an optical disk juke-box offering a total capacity of 80 Gbytes.
10.5) DTS SERVER
The dispatcher training simulator (DTS) function resides on a separate server. In
addition to the system layer and to SCADA/EMS functions identical to those implemented
on the SCADA/EMS servers, it includes the DTS specific functions (Power and Hydro
system model, instructor functions), with a similar man-machine interface. This is an off-
line machine. Software in the DTS is started and run under the instructor (or trainee) control.
Data exchanges with real-time applications is performed by the operator through the use of
HABITAT savecases. Data preservation is performed through manual backup on tapes.
The DTS server consists of one high performance Digital 64-bit RISC based AXP
machine (“Alphaserver”).It is equipped with 512 Mbytes of main memory and 12 Gbytes of
disk storage (4 GB + 4 GB + 4GB).
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DATA SERVERS
10.6) DEVELOPMENT SERVER
The Development server provides the software utilities used to develop and maintain
the system software, displays and databases. This includes a DTS, used as a test tool for
software, database and display modifications.
The Development server consists of one high performance Digital 64-bit RISC based
AXP machine (“Alphaserver”).It is equipped with 512 Mbytes of main memory and 12
Gbytes of disk storage (4 GB + 4 GB + 4GB).
The Development server is equipped with a CD-ROM drive, and an Digital Audio
Tape (DAT) drive which allows backup/restore operations.
One processor terminal is delivered with the Development server. This processor
terminal is a 15” colour monitor, with dedicated keyboard and mouse.
10.7) OPERATOR CONSOLES
There are three types of operator consoles: consoles with 2-CRT, consoles with 1-
CRT and operation scheduling consoles with 1-CRT. Those operator consoles contain the
Man Machine Interface (MMI) software that allows operators to interact with the EMP
functions running on the servers.
Operator consoles with 1-CRT.
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OPERATOR CONSOLES
There are 2 operator consoles with one CRT. Each operator console is a Digital
DPWau AXP workstation, with a 21” colour monitor. Each workstation has a redundant
connection to the LAN. Input is accepted via a mouse device, function keys or alphanumeric
keys.
Each workstation is delivered with 64 Mbytes of main memory, and 4 Gbytes of disk
storage. It is also equipped with one CD-ROM drive.
Operator consoles with 2-CRT.
There are 5 operator consoles with two CRTs. Each operator console is a Digital
DPWau AXP workstation, with two 21” colour monitor. Each workstation has a redundant
connection to the LAN. Input is accepted via a mouse device, function keys or alphanumeric
keys.
Each workstation is delivered with 128 Mbytes of main memory, and 4 Gbytes of
disk storage. It is also equipped with one CD-ROM drive.
Operation Scheduling console
This console is dedicated to the Operation Scheduling activities. Besides the
standard Man Machine Interface (MMI) software, it contains a dedicated software for the
Hydro Thermal Coordination Analysis functions (HTC2).
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The Operation Scheduling console consists of one Intel Workstation, delivered with
64 Mbytes of main memory and 4 Gbytes of disk storage.
This Operation Scheduling console is equipped with one 21” colour monitor; one
3.5” floppy drive and one CD-ROM drive. The complete and detailed hardware
configuration for Operation Scheduling console is described in the release C of the
document ‘Hardware Configuration for all control centers (ref. NR-A/N-G00-1-A05)’.
10.8) DTS OPERATOR CONSOLES
Two operator consoles with 2-CRT are dedicated to the DTS functions. Those
consoles are exactly the same as the 2-CRT operator consoles already described.
10.9) NETWORK MANAGEMENT CONSOLE
The Network Management Console is used to monitor and manage the hardware
equipment interconnected to the LAN. In particular it handles the Network Management and
the performance monitoring functions.
The Network Management console consists of one Intel Workstation, delivered with
128 Mbytes of main memory and 4 Gbytes of disk storage.
This Network Management console is equipped with one 21” colour monitor; one
3.5” floppy drive and one CD-ROM drive.
10.10) DEVELOPMENT CONSOLE
This console is used to develop and maintain the system software, displays and
databases.
The development console consists of one Intel Workstation, delivered with 64
Mbytes of main memory and 4 Gbytes of disk storage.
This development console is equipped with one 21” colour monitor; one 3.5” floppy
drive and one CD-ROM drive.
10.11) LAN AND WAN EQUIPMENT
1) LAN and WAN equipment are integrated into the same platform: the Digital
Multiswitch900 chassis. The main characteristics of this chassis are the following:
2) Contains 8 slots than can be used to plug a full range of LAN hub and switches,
WAN routers, Terminal servers.
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3) Includes a built-in SNMP chassis management agent.
4) Accept up to four power modules, in order to provide N+1 redundant AC power.
5) In order to provide a redundant LAN and WAN configuration, two Multiswitch900
chassis are delivered, each one with the following modules:
6) Two LAN switch modules (Digital Multiswitch 612EX), each one offering twelve
Ethernet 10 Mb/s (10baseT) ports and two 100 Mb/s (100Base TX) ports.
7) Three WAN modules (Digital RouteAbout Central EW routers) allowing
connections with the SLDCs, with the CPCC and with the remote VDUs. Each
RouteAbout Central EW router accommodates up to eight serial ports. Thus the total
number of communication lines available for the RSCC is 24 per chassis. The data
transmission speed is 64 Kbytes/sec per communication line. Each WAN module is
connected to the LAN via an Ethernet interface, thus communication between the
ICCP servers and the WAN routers is accomplished via standard Ethernet
connections.
8) One terminal server (Digital DECserver90M) to connect the loggers, the line printers
and the processor terminal to the LAN. Each terminal server provides up to eight
connections
10.12) REMOTE VDUS
The Remote Video Display Units (VDUs) are remote console used for monitoring
purpose only. They will be installed at the headquarters.
Two remote VDUs are delivered with the RSCC system. They consist of Intel
Workstations, delivered with 64 Mbytes main memory and 2 Gbytes disk storage. They are
also equipped with one 21” colour monitor; one 3.5” floppy drive and one CD-ROM drive.
They use the HABConnect software to access to HABITAT databases on the
SCADA/EMS servers. In order to communicate with the SCADA/EMS servers connected to
the LAN, a Digital RouteAbout Access EW router is delivered with each remote VDU. This
router offers two 64 Kbytes/sec communication lines and is connected directly to the remote
VDU via an Ethernet interface.
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11) SCADA SUBSYSTEM
11.1) FUNCTIONAL OVERVIEW
The purpose of the SCADA subsystem is twofold:
1) It maintains an up-to-date picture of the state of the monitored system in its database.
This allows operators to observe the state of the monitored process by simply
examining the database via CRT displays. The SCADA database also provides other
programs in the system access to the real-time SCADA data.
2) It allows operators (and other programs) to interact with the monitored process by
transmitting controls to the process.
3) Besides, the SCADA subsystem provides the following additional functions:
4) The Tagging function permits the placement and removal of tags from devices in the
system.
5) The Loadshed function (load shedding and restoration) is used in emergency
situations to automatically shed load from the power system. It is also used to restore
load manually, breaker by breaker, or on a group basis, after the system returns to
normal.
6) The Historical Data Recording (HDR) function records all changes to selected data
in journal files both during normal and disturbance conditions. Each file contains an
initial snapshot and then a journal of data changes. HDR can optionally reconstruct a
snapshot of any point in time, at a negligible processing cost. HDR also supports
scan-by-scan reconstruction of data and allows the use of any SCADA displays
(including schematic one-line diagrams) for viewing data.
7) The Sequence of Events function provides information (status changes,
instantaneous measured values) with highly accurate time for devices monitored by
suitable RTUs. This information is normally used by operators to determine what
took place during a system disturbance.
8) The Generalized Calculation (GENCALC) function provides a means for the
operator to derive calculations in a real-time environment , with SCADA analog and
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status points as input and output to the calculation, using any combination of logical,
arithmetic, and comparative operations.
SCADA SYSTEM OVERVIEW
11.2) DATA ACQUISITION
Data is retrieved from the monitored network by an integrated combination of
hardware and software in the real-time application server (“host SCADA”), Telemetry Front
End, Communication Front End and the RTUs. The system maintains a communications
statistics database that keeps a record of all communication failures for assisting
maintenance personnel in detecting deteriorating communications facilities.
11.3) HOST SCADA
The Host SCADA runs the code that is responsible for data processing and operator
interface. It maintains the SCADA database as a coordinated overall picture of the
monitored system for use by the operator and by other programming functions. The Host
SCADA maintains the SCADA database, performs conversion to engineering units, checks
limits, processes alarms and performs special calculations. Status data, analog data, and
pulse accumulator data are maintained in the SCADA database. The host SCADA also
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performs reasonability checks on the incoming data, and sets data quality flags to indicate
the reliability of the source of the data.
11.4) TELEMETRY FRONT END
SCADA supports a Telemetry Front End handling the normal data retrieval
function and sending only data changes to the real-time application server (using NETIO).
The primary purpose of the Telemetry Front End is to distribute communication processing
to allow the RTU protocol specific communications to take place without affecting the host
SCADA computer bus. The Telemetry Front End manages communications with
Communication Front Ends and provides communications with Host SCADA on the real-
time application servers.
11.5) COMMUNICATION FRONT END
The Communication Front End is the lowest level of the Telemetry Front End
SCADA system. It is responsible for all communications between the Telemetry Front End
and the RTUs. The Communication Front End consists of a single board VME based
communications processor using a UNIX "STREAMS" kernel from UconX. STREAMS is a
standard I/O interface definition that exists in UNIX System V and is supported in OSF.
The Communication Front End performs two main functions:
1) It translates the RTU communications protocol into a standard protocol to the
Telemetry Front End. This keeps the host SCADA and Telemetry Front End
software standard across any number of different RTU protocols.
2) It concentrates a number of communications lines into a single interface to the
Communication Front End. This greatly reduces the communications loading on the
real-time application servers, freeing computing power for other more important
uses.
11.6) RTU
The Remote Terminal Unit (RTU) is the interface with the monitored process. It
collects three primary types of data: the status of process devices (digital inputs), measures
process variables (analog inputs) and accumulators (pulse inputs). These three types of data
are transmitted to the Communication Front Ends using standard data communication
techniques.
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The first data retrieval function that the Communication Front End requests from its
RTUs is an "Initialization Scan" called also Integrity Scan or General Check. This causes
each of the RTUs to return all of their data. This initialization function allows the
Communication Front End and the host SCADA to initialize their databases with the latest
information available.
This provides the SCADA system with the best starting point. Once the initialization
scan is complete, the periodic scanning functions begin. Data from the RTUs is received by
the host SCADA, processed, and put into the database.
RTU database can be downloaded on operator request, from a PC using the SIM900
software.
RTU protocol chosen for this project is the IEC 870.5.101 unbalanced protocol and
the SINAUT FW-8 protocol for existing SINAUT RTUs.
The software package delivered with S900 RTU allows handling both digital and
analog inputs/outputs. The entities and related functions controlled by the S900 RTU
include:
1) I/O capacity
2) Multiple master station communications
3) Local data logging
4) Archiving
5) Local alarm
6) Synchronization
In addition, the following software tools are delivered:
1) GBD900: It is a Database generator running in a PC environment and using
ORACLE
2) SIM900: It is a master station simulator running in a PC environment.
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11.7) DATA FLOW
The most important role of the RTU is to interface with the monitored system. This
is done through three types of input data: digital inputs, analog inputs, and pulse
accumulator inputs. This data is collected and stored for transmission to the Communication
Front End.
As data is received from the RTUs by the Communication Front End, it is placed in a
buffer for transmission to the Telemetry Front End. The valid reception of the data is the
joint responsibility of the RTU and the Communication front end. Message numbers, error
detection codes, acknowledge and negative-acknowledge codes are exchanged along with
the data to securely transfer the information to the Communication Front End. The
Communication Front End translates the data from the formats returned by RTUs to the
RTU protocol independent format used in the Communication Front End to Telemetry Front
End protocol. The data is sent to the Telemetry Front End for transmission to the host.
Data received from the Telemetry Front End by the host SCADA is entered into the
RTU hierarchy as a 'raw' value. Engineering unit’s conversion is then done, followed by
limit checking. At each step of the processing, quality codes are set, and alarms may be
issued. If the value is valid and not manually overridden, it ends up in the substation
hierarchy (in the "DISPLAY" field). All operational displays run off the substation hierarchy
of the database.
Once the data is in the host, processing into the SCADA database begins.
11.8) EXTERNAL DATA
SCADA also provides an Application Programming Interface (API) that allows
external application programs to provide data to the SCADA system. This allows external
programs to provide SCADA data and have it undergo all of the data processing features
described in the Data Processing section. This includes limit checking, alarming, quality
checking, calculation triggering.
The external program requires no specific knowledge of where the SCADA system
resides since the API provides a consistent interface regardless of the configuration.
11.9) DATA PROCESSING
The major function of the data processing module is to place the data retrieved from
the RTUs in the database. All data is placed into the database in a standard form: digital
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status in a standard two-bit configuration, analog and accumulator data as single-precision
floating point in engineering units. Three types of information are maintained in the
database:
1) Status values, such as circuit breaker position (tripped/closed)
2) Analog values, which are process variables measured by the RTUs (temperature,
pressure etc.)
3) Pulse accumulations, which usually represent quantities delivered (such as
megawatt hours of electricity)
A combination of the RTU identity and the point identity is used for the scanner
module to locate quickly each point in the SCADA database without searching. This method
enables SCADA subsystem to avoid excessive processing overhead. Once located, each
point (status bit or analog value) is processed according to the directions established for that
point.
The following basic data processing functions are provided:
1) Analog value processing - The retrieved values are converted to engineering units
and placed in the database. The system designer can designate a linear or non-linear
conversion method for each individual analog point. The value is checked against
reasonability limits for the point. If the reasonability limits are exceeded, the data is
marked "unreasonable". If the analog is marked for Historical Data Recording
(HDR), the analog value is saved in a Historical Data file with a time tag and a data
quality flag.
2) Pulse Accumulator processing - Pulse Accumulator processing differs somewhat
from normal analog processing. The last retrieved accumulator value is subtracted
from the current reading and adjusted appropriately if the value is negative (a
negative accumulator difference indicates counter wraparound). The difference is
then converted to floating point and scaled using a multiplier.
3) Status processing - The status processing detects the existence of status changes,
and generates alarms accordingly. If no status changes have occurred, no processing
is necessary. However, if an unauthorized (uncommanded by the operator) change is
detected, the state of the point in the database is changed and an alarm is generated.
The point is also checked for a defined "normal" state. If none exists, no further
processing occurs. Otherwise, an abnormal condition either just occurred or was just
cleared. If an abnormal condition occurred, a new message is added to the abnormal
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summary; if an abnormal condition was cleared, the abnormal message is removed
from the abnormal summary. Status points may also be marked for inclusion in the
Historical Data Recording file.
4) Limit Checking - The analog value is compared against the limits (modified by a
deadband), and if a limit is violated, then an alarm is generated. A set of "dynamic
limits" is placed around an analog value by the scanner module, so that, in most
cases only one pair of limits must be checked when an analog value changes, thereby
increasing limit processing efficiency. The limit deadband prevents the generation of
meaningless limit alarms when an analog is subject to slight variations when close to
the limit. Any number of limits can be applied to an analog value as long as space is
available.
11.10) DATA QUALITY CHECKING
For each status point, analog value, or pulse accumulator record, the scanner module
maintains a number of data quality flags which give information about the value(s) stored in
the record. Generally, a data quality flag indicates something about the source of the data or
tells how reliably the value represents conditions in the field. The User Interface
Management System controls the use of the data quality codes in presenting the data to the
operator.
CALCULATED VALUES
SCADA subsystem provides special processing capabilities that support a wide
range of applications. Any analog or status value can be used in calculating other analog or
status values. The result of a calculation is stored in a status or analog record which can be
subjected to the full range of data processing available, i.e. limit checking, alarming,
logging, etc. Calculations can be defined to be performed periodically or automatically
whenever any of the input arguments change.
These calculation functions generally mark the calculated value with the flag of the
worst-quality value used in the computation. This reflects the fact that computed data is only
as valid as the least valid piece of data used to compute it.
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TOPOLOGY PROCESSING
SCADA subsystem features a topology processing capability that is independent of
that provided by the network analysis applications. This allows real-time determination of
the electrical connectivity and energization state of power system devices. These results are
available for SCADA displays, Alarm and Mapboard interfaces.
Topology processing is triggered by switching element status changes.
Each power system device is represented in the topology model as a one or two
terminal segment. Each device may be classified as live, dead, unknown or ambiguous. The
live determination is made using voltage analog measurements. Each terminal of a device
may be classified as open, grounded, or connected. Each substation may be classified as live
(there are islands, or parts of islands with live status present in the substation) or not live
(there are no islands or parts of islands with live status present in the substation).
The sorting algorithms used to determine bus and island assignments, as well as
island energization status, are efficient and completely general. Any sort of bus structure can
be reliably processed and identified. The modelling of the topology is incorporated in the
SCADA database.
11.11) SUPERVISORY CONTROL
Supervisory Control is the SCADA function used to issue control commands to field
equipment (digital devices, set points) under the supervision of the RTUs, from the operator
or from another application through a user-callable Application Programming Interface
(API).
SCADA subsystem supports two types of control commands:
1) Multiple-step command
2) Single-step command
Single-step commands are typically used when inadvertent or erroneous operations
have minor or no ill effects on the operation of the system. Multiple-step commands are
used by the operator to control devices in the field. Multiple-step commands require positive
operator verification for security.
CONTROL COMMAND PERMISSION CHECKS
Several conditions are checked before a requested control action is actually allowed
to be sent to a RTU. When the operator has completed the external command sequence by
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issuing the EXECUTE command, the host performs a number of checks to see if it is valid
to transmit the command to the RTU:
1) RTU Availability - If the RTU is unavailable to perform the requested operation, i.e.
it has been placed out of service
2) Control/Status Point Availability - If the control point is unavailable because it has
been placed out of service, the command is rejected. If the status point used to
monitor the control results is out of service, a warning message is issued that
verification of the control is not possible, but the command is transmitted to the
RTU.
3) Tagged - If the point is tagged to prevent control action, the command is rejected.
4) Command Interlock - A status point can be associated optionally with a control. If
the associated status point is not in the required state, the control is rejected (e.g., a
device can only be operated when the associated device is in a specified state). This
provides a means to interlock controls.
12) USER INTERFACE MANAGEMENT SYSTEM
This section briefly describes the SCADA user interface, focusing primarily on
SCADA displays and alarm functionality.
TYPES OF DISPLAYS
Data in the SCADA database and indications of changes are presented to the
operator through the following major displays:
1) Menu Directory Display - A display that lists all the menu displays.
2) System Directory Display - A display that lists all the SCADA system displays.
3) Transmission System Overview Display - A graphic overview display of the
transmission system (provided by PGCIL)
4) Interchange Displays - A schematic diagram showing power transfer between all
Constituent power systems in the Northern Region, plus four other interchange
displays (provided by PGCIL)
5) Substation Graphic Displays Menu Display - A graphic display which lists all the
existing substation graphic displays.
6) Substation Displays - The major operations displays (provided by PGCIL)
7) Transmission Line Graphic Displays Menu Display - A graphic display which
lists all the transmission lines which can be viewed via a graphic display.
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8) Transmission Line Graphic Displays - A graphic display which shows the entire
line and all of its connections (provided by PGCIL)
9) Abnormal Summary - A compilation of all existing abnormal conditions.
10) Out of Service Summary - A listing by substation of all points removed from
service.
11) Tag Summary - A listing by substation of all tagged devices.
12) Inhibit Summary - A listing by substation of all devices inhibited from generating
alarms.
The Transmission System Overview display gives the operator quick overview and
access to the information describing the entire system. The operator can use it to access the
substation, power station and transmission line displays for detailed information to analyze
and direct operations.
The abnormal summary displays are of particular interest to operators. They give
structured overviews of conditions of interest and unusual conditions in the system. The
remainder of the summaries, the tag summary, the inhibit summary, and the out of service
summary, are useful for reviewing the processing status of the SCADA system itself.
12.1) MENU DIRECTORY DISPLAY
The Menu Directory display lists all the menu displays and provides for each of them
a button for calling up the menu display.
The organization of this display is driven by the database of the MENU application
(tabular display). This organization is made of groups, sub-groups in the group and
functions in the sub-group. Once you select a group button, the sub-groups are listed with
their functions definitions which provide the way to call up the relevant menu display.
12.2) SYSTEM DIRECTORY DISPLAY
The System Directory display lists all the SCADA system displays of a particular
function, and provides for each of them a button for calling up the SCADA system display.
12.3) TRANSMISSION SYSTEM OVERVIEW DISPLAY
The Transmission System Overview display is the most convenient starting point
whenever a new sequence of operations is begun.
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The Transmission System Overview display is a graphic overview display of the
transmission system with substations, power stations and transmission lines. Lines are color
coded by voltage level, and highlighted in case of loading limits exceeded. Substations and
power stations are depicted by symbols in case of alarm presence.
Real and reactive power flows are displayed (a value and a direction arrow) for lines
and power stations. For the power stations, the maximum real power output is also
displayed.
The functionality of this display is carefully designed to give operations personnel a
comprehensive overview into the system. This allows them to analyze quickly system state.
Using the Transmission System Overview display, the operator can see at a glance the
general condition of the entire system by panning and zooming to navigate through the
display. Once the operator has determined what to look at in more details, he can quickly go
to the relevant displays, by selecting a substation, a power station or a transmission line.
12.4) INTERCHANGE DISPLAYS
These displays are the major displays for power transaction control. The following
displays are used:
1) Interchange Display - This is a display that contains the schematic diagram
showing power transfers between all Constituent power systems in the Northern
Region. Each power system is represented by a block. Inside the block, the actual,
scheduled and deviation values of power flows are shown for total generation and
load. Outside the block, the actual, scheduled and deviation values of power flows
are shown for the net interchanges, with direction arrows.
2) Tie-line Display (Generation Tie-line Status) - This is a tabular display that contains
tie-line boundary and exchange data. The tie-line names and voltage levels are
shown, as well as the measured or manually entered real power flow and boundary
values (limits).
3) Transaction Schedule Display (Start/Stop Transaction Schedules) - This is a
display that provides the ability to enter and display constituent hourly interchange
transaction schedules.
4) Central Sector Shares Display - This is a display that provides the ability to enter
and display the Constituent percentage shares for each Central Sector project as
allocated by employer.
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5) System Frequency Display - This is a display that contains the schematic diagram
showing the geographical location of the tie-line substations. For each of them,
telemetric frequency buses are shown, and the frequency value displayed.
12.5) SUBSTATION GRAPHIC DISPLAYS MENU DISPLAY
The Substation Graphic Displays Menu display lists all the Substation Graphic
displays and provides for each of them a button for calling up the Substation Graphic
display.
The organization of this display is driven by the SCADA database (tabular display).
SUBSTATION DISPLAYS
These displays are the major operating displays for dispatching personnel. They
contain the most detailed information about the system and allow control operations to
change the system. These displays are organized by substation, and each substation's
displays are closely linked together as a coherent group. The following general display
layout is used:
1) Substation Graphic Display - This is a display that contains the detailed graphic
one-line diagram of the substation. It contains most of the information known about
the substation. Controls may be issued from it.
2) Substation Tabular Display - Accessible from any other substation display, this is
generally the most complete listing of the data known about the substation. Although
controls can also be issued from here, they are generally used for entry of operational
data (limits for example).
12.6) TRANSMISSION LINE GRAPHIC DISPLAYS MENU DISPLAY
The Transmission Line Graphic Displays Menu display is a tabular display that lists
all Transmission Line Graphic displays. Several views of the display are available,
according to the voltage level. In a voltage level view, the data are driven by the SCADA
database, and show the tie-line and the associated substation names. These names are
displayed inside buttons, and allow the navigation to the relevant displays (Transmission
Line Graphic displays and Substation Graphic displays).
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12.7) TRANSMISSION LINE GRAPHIC DISPLAY
The Transmission Line Graphic display is a graphic display of a transmission line. It
presents telemetric, manually entered and calculated power system data on a one-line
diagram that shows the entire line and all of its connections. At each end of the line, the
diagram shows the line breakers and the bus to which the breakers are connected, plus the
substation name.
The substation name button provides the way to call up the relevant substation
graphic display for more detailed information.
The user is able to perform any user interaction with the power system data and the
line breakers (e.g., manual replacement of a value, or control of a breaker).
12.8) ABNORMAL SUMMARY DISPLAY
These summaries are lists by substation and by time of the conditions in the system
that are unusual (abnormal). This is an important list for the operator for several reasons.
First, the system was engineered to operate in a specific manner (e.g. some switches should
be open and some switches should be closed). The operator has a picture in his mind of the
normal operating configuration of the system. The abnormal summary updates the
operator's mental picture about the configuration of the system.
Second, when an operator comes on shift, the abnormal summary helps inform the
operator of the changes that have taken place in the system since last viewed.
The following data is shown as a part of the abnormal summary:
1) Time and Date - The time and date that the abnormal condition occurred.
2) Identity - The identity of the device in an abnormal condition.
3) Status - The current state of the device. Although this is somewhat redundant, the
actual state of the device is shown (e.g. open/closed for example).
13) HISTORICAL INFORMATION AND MANAGEMENT
Historical information and management is also called HIM. HIM consists
of two data servers. One is real time data server and second is informational
storage & retrieval or ISR server.
Real time data server stores data of all substations after each 10-second.
One file can store data for approximately 37 minutes. Real time data server can
store data for maximum of 4 months then it will delete. So back up is necessary
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ISR server stores data of all substations after each 15 minutes. It can store data
for maximum two years.
The whole Database is Oracle based. Real time data server collects data
periodically, changes it in to specified database and sends it to the HIM
recorder. ISR can achieve and restore data. One can store data in magnetic tape
and jukebox or optical disc as backup data. Data can be restored from tape and
jukebox to the relational database on users demand.
Data files like HDR, HABITAT databases; SAVECASES can be
restored on the server on users demand. ALARM application on real time data
server send the alarm & events data to the ASCII files. Then these files are
stored in ISR server and restored in relational database. Then these files are
removed from real time data servers. One can check the data history for load
forecasting. Sequential query language interacts between operator consoles and
HIM.
Operator console is the key with which operator interacts with the
database
HISTORICAL DATA RECORDING
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REASONS FOR FAILING THE CONTROL
1) RTU may not in service
2) Device is in local control mode
3) Control point is not in service
4) Control point is attached with safety tagged
5) A Control request is already pending on the device
14) UTILITIES USED BY SCADA SYSTEM
There are various utilities used by the SCADA system. But main utilities
are:
14.1) ALARMS
If there is abnormal condition in the monitored system, it can respond by
taking various actions to alert the operator of the condition. The response of
SCADA to a specific condition occurring on a specified point is defined in the
database. When a normally closed circuit breaker trips, system causes an
audible alarm to be issued for that breaker, SCADA can detect problems that
occur for status, analog and count points, RTU and other equipment in the
communication system and software. SCADA can issue alarm when status point
returns to normal form an illegal state or an abnormal state or a communication
path to a SCADA site comes up or goes down. Alarm is also issued when
scanning of data fails.
Each alarm belongs to a category. There should be a proper location of
an alarm in the SCADA system. For other alarms, typically designated the
name of the EMS subsystem that issues the alarm. Alarms should be grouped
per area i.e. transmission area, distribution area etc.
14.2) TAGGING
A tag is placed on a device for both safety and informational purposes.
Tagging enables us to place tags on status devices modeled in SCADA. These
tags can prevent a device from tripping and display a comment about the
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device. Its tag type determines the effect of a giving tag on a device. Tags of
different types prevent device from tripping.
TAGGING
14.3) TRENDING: -
The purpose of trending is to reconstruct the post status of SCADA data.
One should select the point for trending and define sampling rate and scale
values also assign the point to a console for trending. It shows us how the
different parameters behaving in the system.
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