IRSE Technical Meeting - Adelaide 22 July 2011

The Elephant and the Flea - Living with Traction Return Currents

Dwayne Allan

Siemens Ltd

“Distributed Architecture” is a term used to define control systems which have the ability to disperse system components in a decentralised manner, a centralised manner, or a mixture of the two.  Distributed control systems have their heritage in manufacturing, process or other forms of dynamic systems in which the control of sub-systems is distributed throughout the system but controlled by one or more programmable logic controllers (PLC’s) in a central location.  This philosophy is often applied in process environments with equivalent SIL requirements to railway signalling systems.

A railway signalling system and in particular the interlocking is essentially a dynamic process control which lends itself to the use of distributed architectures with PLC’s.  The use of such systems and the resultant system flexibility can lead to significant changes in system design and requisite cost implications for railway authorities.