scada

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

Introduction

This interruption can be done by using circuit breakers

Introduction

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

Introduction

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

SCADA

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.

Operation before SCADA

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.

Operation before SCADA

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.

Operation before SCADA

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...

Advanced control

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.

STROUGER SYSTEM

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

STROUGER SYSTEM

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.

MORE ADVANCED TECHNOLOGY

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

SCADA is the acronym of supervisory control and data acquisition

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.

ELECTRIC TRACTION

Electric traction

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.

ELECTRIC TRACTION

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

ELECTRIC TRACTION

TRACTION SUBSTATION

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.

SCADA

SCADA SYSTEM BLOCK DIAGRAM

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.

SCADA

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

SCADA

MODEMS

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.

MODEMS

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.

MODEMS

MMI AT THE RAILWAYS

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.

RTU’s

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

RTU’s

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.

RTU’s

STAR

ONE TO ONE

COMMUNICATION BETWEEN RCC AND RTU

MULTI DROP

COMMUNICATION BETWEEN RCC AND RTU