1. TYPICAL SCADA SYSTEM FIELD UNIT SCADA H/W & S/W C TX O RX M E M Q N P
T P
R A
A N
N E
S L D U C E R
C & R
PANEL
MEDIA
FIELD UNIT
CONTROL
CENTRE
COMMN
MEDIA
SUBSTATION / GEN STATION

3. Instrumentation For SCADA
Transducers
RTU
Current Transformer
Capacitor Voltage Transformer

4. TRANSDUCER Device converts one form of energy to another form.
Energy form viz. electrical, mechanical, chemical etc.
Transforms High level to Low level
Input – Hundreds of volt
Output – Few milliamperes
Measures field parameters like voltage, frequency, current, 3 phase bi directional active & reactive power and transformer tap position
Accuracy : +/- 0.2% class for frequency transducers and +/- 0.5% class for other transducers

5. TRANSDUCER TYPICAL RATING Transducer Input Output
Voltage V mA
Current Amp mA
0-5 Amp
Frequency mA
MW mA
MVAR mA

6. Remote Terminal Unit
The RTU performs the data acquisition and supervisory control over the substation for the SCADA system.
As a minimum, the RTU collects, processes and transmits the data from the substation to the control-centers.
The following data are generally acquired from the sub-station:-
Analog- Power, Reactive Power, Voltage, Frequency, Current.
Digital- Circuit Breaker Status, Isolator Status,SOEs
The RTU also receives and processes digital and analog commands.

7. RTU: MAIN FUNCTIONS
SCADA
Local Control
Data Logging
Process Control

8. HARDWARE CONNECTIVITY DIAGRAM FOR SCADA AT SUBSTATION / GEN.STATION
RS232 PORT
REMOTE TERMINAL UNIT
TRANSDUCER PANEL F R O M S W I T C H Y A D - E L
P T
SEC
110VAC
TRANSDUCER I/P TERMINAL
MAIN
CPU
BOARD
COMMN
BOARD
PSU MW
MVAR
VOLT
CT SEC
1 AMPS
TRANSDUCER O/P TERMINAL A N L O G
I / P D I G T A L
I / P C O N T R L
O/P
EVENT LOGGER
PANEL D R I V E R E L A Y
TERMINAL
BLOCK
TERMINAL
BLOCK
TERMINAL
BLOCK

9. SCADA HARDWARE CONNECTIVITY WITH COMMUNICATION SYSTEM(PLCC) AT SUB-STN/GEN ST
RTU N S K 5
modem
RS 232 CONNECTIVITY
PLCC T x / R x
SPEECH / DATA
PANEL
PLCC
INDOOR EQUIMENT

10. TRANSDUCERS CLASSIFICATION INPUT OUTPUT OUTPUT IMPEDANCE ACCURACY
SELF POWERED/AUXILARY POWERED
INPUT
VOLTAGE/CURRENT/POWER/POSITION
OUTPUT
0-10mA, 4-20mA, 0-5mA 0-5v,0-10v
OUTPUT IMPEDANCE
500Ω,1000Ω,2000Ω
ACCURACY
0.2 CLASS, 0.5 CLASS, CLASS 2 AND ABOVE

11. A/D CONVERSION AT RTU LEVEL (16 BIT ADC).
FOR MW / MVAR TRANSDUCER:
INPUT: PT SEC PHASE TO PHASE : 110VAC
CT SEC TWO PHASE CURRENT (R & B): 1 AMPS.
OUTPUT : 4 – 20mA(TRANSDUCER OUTPUT)
IN ADC:
AT 4mA = 6553 Count
AT 20mA = Count
12mA IS THE CENTRE POINT.
(+/- 0.1% IS THE ACCEPTABLE RANGE OF ERROR ON FULL SCALE)
( Ref Calculation Sheet for all type of Measurand)

12. TRANSDUCERS
Measures field parameters like voltage, frequency, current, 3 phase bi directional active & reactive power and transformer tap position.
Rating
Vol: 110/115 volts phase to phase
Current : 1 A
Frequency: Hz
Output : 4 – 20 ma / 500 ohms
External power supply
IEC 688
Accuracy : +/- 0.2% class for frequency transducers and +/- 0.5% class for other transducers

13. SALIENT FEATURES OF ULDC RTU
A small rugged computer
CPU, volatile & non-volatile memory, power supply module, I/O module
Communication ports & maintenance ports
Allows the central SCADA master to communicate with the field devices
Acquires the data from the field devices/equipment and transfers the data to the SCADA system
Distributed Processing Technology
Main processor is 32-Bit 16Mhz and sub modules are 8-bit.
Real time clock
Access via PC-Based Configuration.
Password Protected.
Database configured via a PC and can be downloaded

14. SALIENT FEATURES OF ULDC RTU
Switch mode converter power supply module which provides power for mother board, VME cards, I/O modules and peripherals. Input voltage – 241 V AC, 50 Hz. Outpit voltage +/-5V DC, +/- 12 V DC, +/- 24 V DC
32 Analog inputs per module ,15 bit resolution .
Conversion rate 660 ns for all 32 inputs.
64 status inputs per status module,1ms scan time for 64 inputs,1ms SOE resolution. A simple status input/SOE input/accumulator input can be connected. LED indicators for each input. Contact wetting voltage supplied by power supply module.
32 control output per control module. Two master relays for each output. One for close and one for trip.
Through the maintenance port, we can download the database, view data and Communications specific to each peripheral board and trouble shoot .
Advanced diagnostic capabilities
Time synchronisation of RTU done at every 1 minute.

15. Scan Cycles All the analog data are scanned every 10/12 seconds
Status information are reported by exception
All status information are scanned for integrity check every 10 minutes
The SOE datas are time stamped at 1 ms resolution
Time synchronisation is done every 10 minutes

16. Current Transformer
A current transformer is a measurement device designed to provide a current in its secondary coil proportional to the current flowing in its primary .
The current transformer isolates measurement and control circuitry from the high voltages typically present on the circuit being measured .
Common secondary are 1 or 5 amperes. For example, a 4000:5 CT would provide an output current of 5 amperes when the primary was passing 4000 amperes .

17. Capacitor Voltage Transformer
Capacitor Voltage transformers (CVTs) are used for metering and protection in high-voltage circuits. They are designed to present negligible load to the supply being measured and to have a precise voltage ratio to accurately step down high voltages so that metering and protective relay equipment can be operated at a lower potential.

18. Basic Function Of the CVT
Where CHF is the equivalent rated capacitance for carrier communication
* C1 : High Voltage capacitor
* C2 : Intermediate Voltage
Capacitor
* C1 / C2 ratio is such that the required intermediate voltage can be achieved
L : Inductance of the choke which is designed to
* Prevent carrier signals from flowing into the transformer circuit.
* Resonate with the capacitor unit at 50 Hz which is the rated frequency.
D : Damping burden which is provided across one of the secondary windings to prevent terroresonance oscillations.
Tr : Transformer designed to provide the required output voltage at the desired burden HV Tr L C1 1a
Metering
CHF 1n 2a C2
Protection D 2n