A natural outgrowth of the move to static-trip devices has been to provide
devices that can display the quantities they are monitoring. This trend has come
in response to user’s concerns regarding the convenience in monitoring loads
and in troubleshooting a given distribution system. Low-voltage switchgear
generally has space constraints within its breaker cubicles; consequently, mounting
space (if any) for additional current transformers is limited. Manufacturers
are beginning to offer monitoring packages that take advantage of the signals
already made available by the protection devices. The information can be displayed
on the trip device or sent to a cubicle door mounted display. Automated
data processing centers and cogeneration sites have set up elaborate monitoring
systems by taking advantage of the communications functions that are now
offered. Almost every feeder at a user’s site can be monitored and all of its electrical
performance data sent back to a central system. The trend in interfacing this
basic electrical monitoring with communications to fi eld programming units
(FPUs); remote terminal units (RTUs), programmable controllers (PLCs) used as
sequence controllers, data collectors, or concentrators; and sequence control and
data acquisition (SCADA) systems is expected to continue. Many of the elements
used in these systems are now installed directly in the switchgear.