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

Instrumentation For SCADA Transducers RTU Current Transformer Capacitor Voltage Transformer

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

TRANSDUCER TYPICAL RATING Transducer Input Output Voltage 0-110 V 0-10 mA Current 0-1 Amp 0-10 mA 0-5 Amp Frequency 4-20 mA MW 4-12-20mA MVAR 4-12-20mA

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.

RTU: MAIN FUNCTIONS SCADA Local Control Data Logging Process Control

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

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

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

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 = 32767 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)

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: 45-55 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

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

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.

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

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 .

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.

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