Industrial distributed control continues the move
toward networks at all levels. At lower levels, control networks
provide flexibility, reliability, and low cost, although perhaps the
simplest but most important advantage is the reduced volume
of wiring. Powered fieldbuses offer particular notable benefits in
system wiring simplification. Nevertheless, very few papers are
dealing with the potentials and limitations in power distribution
through the bus cable. Only a few of the existent fieldbus standards
consider this possibility but often simply as an option without
enough technical specifications. In fact, nobody talks about it, but
power distribution through the bus and conducted noise disturbances
are strongly related. This paper points out and analyzes
these limitations and proposes a new low-cost fieldbus physical
layer that enlarges power distribution capability of the bus and
improves system robustness. We show an industrial application
on water desalination plants and the very good results obtained
owing to the fieldbus. Finally, we present electromagnetic compatibility
test results that verify improvements against electrical fast
transients on the sensor/actuator connection side as disturbances
usually encountered in harsh-environment industrial applications
