Cooper Power Systems developed advanced relay protection systems for electric arc furnace (EAF) power transformers that incorporate Rogowski coil (RC) current sensors and multifunction relays. In the past, differential protection schemes were not applied on EAF transformers due to the difficulty in providing conventional iron-core current transformers (CTs) of sufficient rating for the conductors carrying currents of 60 kA or more. Rogowski coils are low power sensors, linear (do not saturate), accurate, and immune to external electromagnetic fields. Rogowski coils may replace CTs in all metering and relaying applications, providing superior relay protection schemes to protect power transformers, generators, lines, and busbars. Several EAF transformer differential protection projects have been implemented. They have reliably operated since their installation (now over two years).
