Much more than an overcurrent relay

The introduction of the microprocessor into the design of power system static overcurrent relays has led to numerous advances in capability. The addition of functionality beyond nominal overcurrent protection is one of the more profound changes made possible by advanced technology. This paper describes those functions added to a relay developed for use on switchgear. Application of these relays can provide enhanced protection and diagnostic tools, while economically providing data for disturbance analysis, power system and energy management.