supervisory control and data acquisition

2.  As we know in the power systems faults can
occur at any time. Hence we have to interrupt
the fault currents.

3.  This interruption can be done by using circuit
breakers

4.  When the short circuit occurs at the power
system , the circuit breakers has to be
operated..
 The circuit breaker connected at the power
transformer protects the power transformer
from bursting due heavy current

5.  The operation of the circuit breakers is
necessary to protect the transformers in the
substations as they are so costly.

6.  In olden days this operation is done by the
human arm power. Whenever there is a fault
occurred in the power system, the man
should go there and should operate the CB.

7.  Until the man goes there and operate the
circuit breaker there will be a fault current
flowing in the transmission line. This may
damage the power system components.
 Hence this must be controlled quickly as soon
as the fault occurs.

8.  Also there is harm to the person who is
engaged to operate the circuit breaker.
 And if the man is not available there, the
costly equipment will be get damaged and
never cannot be repaired and to be replaced.

9.  The operation of the interrupters
through the man is developed by the
remote control operation.
 The first method to come into
existence of remote control is the
STROUGER SYSTEM...

10.  In the remote control system we use certain
components such as RTU’s(remote terminal
units),modems(modulators &
demodulators),RCC(remote control centres)
etc.
 Strouger system is also called as the
automatic telephone exchange system.

11.  This system uses the telephone signal
between the RTU’s and the field systems
 Hence when the two subscribers are on the
conversation, if the fault occurred at the
other subscriber it is not known to them until
the two subscribers stop their conversation
as they are engaged.
 This the drawback of the Strouger system

12.  To overcome this problem, the SCADA
system is come into the existence.
 In the SCADA system we use the
communication by using LAN
connection of the microprocessor
situated in each system.

13.  SCADA is nothing but the remote control of
the power system components to operate
when there is a fault
 It is the system to ‘supervise’, ‘control’ and
‘acquire’ field data
 SCADA is used in many industries for it
efficient control
 It can be used in electric traction

14.  Indian railways use 25kv ac supply run the
trains by electric supply and for other
purposes
 Though some of the trains are still running
through steam, the electric traction find the
better way of transport in railways
 The MMTS trains in the city run through the
supply connected to the pantograph of the
train at the time of starting.

16.  The 25KV ac supply from the traction
substation is given to the OHE line which
connects to the pantograph of the locomotive
 The return path of the current is through the
loco wheels.
 As the train is grounded there is no harm to
the people travelling by the train.

17.  The 25kv ac supply is stepped down and
rectifies and given to the traction motors.
 And the stepped down supply is used as the
power required to maintain the SCADA
system and the battery unit provided.
 The battery room is provided seperately to
operate even when there is a power failure

19.  In the SCADA control systems we can
communicate with each and every subscriber
through wireless communication.
 In this process we have two systems from
which the total operation is controlled. They
are HOST and STAND-BY SYSTEMS.
 SCADA software is installed in the above
systems and made to run 24hours.

21.  The railways always use a stand-by for every
component. The HOST and the stand-by are
connected to the FEP’s(front end processors)
through the LAN.
 The FEP’s connect to the modems to
modulate the signal given by the HOST
system.
 The modems are in turn connected to
modems available at RTU’s in the field
through wireless communication.

22.  For the operation of the circuit breakers and
the interrupters the 110v Dc supply is
provided along with the battery supply
system and the battery charger system
 The RCC’s in the scada system should be air
conditioned and should not exceed 40degree
celcius

24.  Modems at the HOST sends the signal to the
modems at the RTU’s by modulating the
signal and receives the signal from them by
demodulation.
 RTU’s at the field consist of converters,
alarms, sensors etc.
 It senses the fault signal and sends the
information to the modem present at the
HOST.

25.  HOST which is connected to the MMI(man
machine interface) through the LAN gives the
information to them.
 Hence the operator available at the MMI
disconnects the supply at the fault using a
mouse. This is called the remote control
system.

27.  The main equipment present in the RTU’s are
the alarms. As soon as the fault occurs the
alarm is activated and the message is sent to
the HOST by the modems to alert the
operators.
 RTU’s have analog to digital converters to
send the obtained analog signal to the MMI as
the digital one.

28.  RTU’s at various switching posts shall be
communicate with optical fibre wires or by
the VHF radio paths.
 RTU’s also have input modules and the
output modules to which the inputs and the
outputs are to be connected.
 The protocol used in railways is
SPORT(standard protocol of railway
traction)protocol

29.  The number of working stations in the SCADA
system will be two. However for the system
having less than 15 RTU’s the station must be
only one.
 There is a multi drop configuration between
the RCC and the RTU.

30. STAR
ONE TO ONE

31. MULTI DROP
COMMUNICATION BETWEEN RCC AND RTU