01 May 2004 By Patrick McCurdy Ins and outs of surge protection
devices. Today's process control environment is rich with
advanced electronic technology that brings benefits such as
faster data acquisition, real-time control, and fully automated
factories. Unfortunately, a trade-off of the increased
performance is the increased susceptibility of these electronic
devices to voltage and current transient events. Such power
surges are often the work of Mother Nature. Lightning, which by
some estimates strikes nearly 40 million times annually in the
U.S., is a leading cause of failure in process control systems.
Although the most devastating source of transient voltage and
current activity is lightning, other sources include static
buildup, human error, inductive load switching, and utility
capacitor switching. Companies typically pay attention to
protecting the alternating current (AC) power from such damaging
power surges, but often the pathway to sensitive electronics
lies with the signal and data lines. We th