Ptd By

Prasad Ghatikar,BE(E&C),MBA(IS)

Assistant Engineer,

Scada-1,Telecommunication Division(N),

KPTCL,Hubli

Introduction

Supervisory control and data acquisition (SCADA) system acquires data from remote substations to one or many control rooms and controls the major operations of substation equipments from the remote control room/s.

Electrical data can be instantaneous values of currents & voltages phase wise, real power (MW), Apparent power (MVAR), frequency, power factor, kwh(Export) & kwh(import) etc. Also the SCADA system transmits digital input data such as status indication of circuit breaker ON/OFF, Auto trip, Line/Bus/Earth isolator positions & Local/remote position in 11 KV class switchgears.

SCADA system enables the engineer sitting in the hub center to remotely charge/trip the circuit breaker of any control and relay panels or switchgears of any remote substation of KPTCL/ESCOMS.any remote substation of KPTCL/ESCOMS.

Thus SCADA system helps to acquire real time electrical data, status indication of equipments and have a supervisory control on desired station equipments of remote sub-stations.

Basic Block Diagram of

SCADA:

Substation

equipments

(C&R Panel

Tx. Media-----

Remote

Termi

TX Media

-----------

----------

SCADA CONTROL (C&R Panel

and

Switchgears)

-------------

(cables)-----------

--

Terminal

Unit(R.T.

U)

----------

---------(Satellite

communi

cation)

------------

------------

------

CONTROL ROOM

Basic Block Diagram of SCADA:� As shown in the above block diagram, the C & R

panels/switchgears housed in electrical sub-station send all the analog data, digital input and control data to remote terminal unit via cables and this inturn is to remote terminal unit via cables and this inturn is processed by processors at RTU. These processed electrical data are transmitted to SCADA control room through satellite communication.

SCADA - A TOOL OF EFFECTIVE ENERGY MANAGEMENT

AND AUDIT

SCADA CONCEPTSCOMPONENTSCOMPONENTSAPPLICATIONSCOST/BENEFITS

SCADA CONCEPTS

CONTROL CONTROLLEDCONTROL

CENTRECONTROLLED

PLANT

COMMUNICATION

SYSTEM

CONTROLLED PLANT

� Remote Terminal Unit (RTU)� Interfacing panels consisting of - transducers, relays,

contactors

� REMOTE TERMINAL UNIT (RTU)� REMOTE TERMINAL UNIT (RTU)

RTU 560A of make M/s.A.B.B. Private Limited is used in our SCADA system which can process 64 input/output ports. It has two processor cards called CMU units, of which one is master and another slave. This RTU unit is a ruggedised, specific application computer.

It is an equipment located at the controlled plant to:-to:-

� Implement the commands of the control center

� Perform data acquisition in respect of

� Analogs

� Breaker status

CB

Field

CT

PTPotential

Free Contact

Close Trip

Pannel control

Basic Data Acquisition

TRANSDUCER

RTU Ang In RTU Dig In

DAS NO Coil

for Close

NC Coil

for Trip

RTU Dig out

REMOTE TERMINAL UNIT (RTU)

IT HAS

� Analog input cards for acquisition of analog

� Parameters such as voltage, current.

� Digital input cards for sensing breaker status.

� Digital output cards for performing close / trip

� Operation of circuit breakers through Interposing relays .

� Analog output cards (optionally) to drive the Chart recorders

to have a continuous plot of Analogs.

HARDWARE CONNECTIVITY DIAGRAM FOR SCADA AT SUBSTATION /

GEN.STATION

MAIN

CPU

BOARD

PSU

COMMN

BOARD

A D C

REMOTE TERMINAL UNIT

TRANSDUCER O/P TERMINAL

MVAR VOLTMW

TRANSDUCER I/P TERMINAL P T

SEC

110VAC

CT SEC

1 AMPS

F

R

O

M

S

W

I

T

TRANSDUCER PANEL

RS232 PORT

A

N

A

L

O

G

I / P

D

I

G

T

A

L

I / P

C

O

N

T

R

O

L

O/P

TERMINAL

BLOCK

TERMINAL

BLOCK

TERMINAL

BLOCK

T

C

H

Y

A

R

D

-

F

I

E

L

D

EVENT LOGGER

PANEL

D

R

I

V

E

R

R

E

L

A

Y

TRANSDUCERS

TYPES

� Self powered

� Auxiliary Powered

� Convert inputs into low power signals (4-20 milli amps dc) that � Convert inputs into low power signals (4-20 milli amps dc) that

can be accepted by the RTU.

� Should have linear characteristics over the operating range.

INTERFACING

� The connection between the controlled plant and the RTU is termed as interfacing.

� Interfacing panel will house transducers, contactors and relays.

� Breaker status sensing is done by the auxiliary switch Normally� Breaker status sensing is done by the auxiliary switch NormallyOpen (NO) and Normally Closed (NC) contacts.

� If the only one contact (NO / NC) is used for sensing the statusof breaker / isolator, it is called as single bit indication.

� In double bit indication both the NO and NC contacts aresensed.

Multifunction

transducers(MFTs) :-Multi function transducers convert all the

electrical data into the form of output of 4-20 mA. This output is transmitted in MODBUS protocol to RTU unit, which inturn processes and sends across to hub center. It is which inturn processes and sends across to hub center. It is called multifunction transducer as it acts as voltage, current and frequency transducer.

The secondary side of current transformer(CT) connections and potential transformer (PT) connections are terminated into the MFT, & these current and voltage data of all three phases are transmitted to processor cards of RTU by this very MFT.

INTERFACING

� The connection between the controlled plant and the RTU is termed as interfacing.

� Interfacing panel will house transducers, contactors and relays.

� Breaker status sensing is done by the auxiliary switch Normally� Breaker status sensing is done by the auxiliary switch NormallyOpen (NO) and Normally Closed (NC) contacts.

� If the only one contact (NO / NC) is used for sensing the statusof breaker / isolator, it is called as single bit indication.

� In double bit indication both the NO and NC contacts aresensed.

• Keep sufficient (at least 20%) over range for transducers

• Ensure that the cable lengths between the PT, CTs and RTU

kept as short as possible to avoid excessive drop.

• Ensure perfect earthing of substation

INTERFACING CONSIDERATIONS

• Ensure perfect earthing of substation

• Connect SCADA earth to the substation earth to avoid

differential voltages occuring during faults which are likely

to damage the sensitive electronic equipment.

TYPES OF PROTOCOLS

� Proprietary Protocol

� Open Protocol

� Proprietary protocols are vendor specific. So followingthis, we’ll get tied down to only one vendor which isundesirable.undesirable.

� Open protocols are based on ISO’s Open SystemInterconnection (OSI) model.

� Most commonly followed OSI model is a 7 layer model.

� Different types of Protocols used are.

� Modbus : Each device intended to communicate using Modbus is given a unique address. In serial and MB+ networks, only the node assigned as the Master may initiate a command. On Ethernet, any device can send out a Modbus command, although usually only one master device does so. A Modbus command contains the Modbusmaster device does so. A Modbus command contains the Modbusaddress of the device it is intended for. Only the intended device will act on the command, even though other devices might receive it (an exception is specific broadcastable commands sent to node 0 which are acted on but not acknowledged). All Modbus commands contain checksum information, to ensure a command arrives undamaged. The basic Modbus commands can instruct an RTU to change a value in one of its registers, control or read an I/O port, as well as command the device to send back one or more values contained in its registers.

� DNP� UCA

IEC 61850IEC 61850

� IEC 61850 is the new Ethernet-based internationalstandard for communication in power generationfacilities and substations. The goal of this standardfacilities and substations. The goal of this standardis to integrate all of the protection, control,measurement, and monitoring functions within asubstation, and to provide the means for high-speedsubstation protection applications, interlockingand intertripping.

COMMUNICATION SYSTEMCommunication system selected should have

� Expandability & flexibility

� Reliability

� Two way communication capacity

� Ability to meet data requirement

� Transmission Media (V-SAT very small aperture terminal): � Transmission Media (V-SAT very small aperture terminal):

INSAT 3A satellite is used for communication and MFT DMA technology is used to transmit and receive data.

1.8 Mtrs. Diameter Antenna of parabolic reflector type is housed on top of every substation for communication to satellite. 9 Mtrs. Diameter Antenna is placed at Master control centre, A.R.Circle, Bangalore. The 11.5 MHz bandwidth is used and approval for additional 8 MHz bandwidth is received for SCADA communication

As the star topology is used, the data from every station is received individually and unhealthiness of one node (station) does not affect the data transmission of another node(station). The sub-stations are located in diverse geographical locations & their physical connections using optical fiber or PLCC is cumbersome, complex and uneconomical. Hence satellite communication network is used which is economically viable and at the same time technologically competent.

SCADA APPLICATIONSi) Helps in decision making.

ii) Provides instantaneous to energy exchanges thus helping in energy billing.

iii) Optimum distribution of power.

iv) Maintaining grid discipline and in turn better grid management.

v) SCADA system helps in running energy management system (EMS), v) SCADA system helps in running energy management system (EMS), distribution management system & likewise energy software packages. Also helps in making a smarter grid.

vi) Load forecasting and monitoring.

(vii) Adherence to availability based tariff (ABT), open access & avoidance of UI (unscheduled interchange) charges.

(viii) Catering to the functional requirements of SRLDC, CERC, KERC, CEA & other state government Power utilities.

(ix) Better co-ordination between different Govt/Private agencies, bringing in transparency and thus helpful to every stake holder including general public.

THANK YOU