Novel relay protection systems using low-power sensors (part ii)

The novel PCB Rogowski coils (RC) with new multifunction relays and communications can improve substation protection schemes, and make possible protection schemes that in the past could not be implemented using conventional current transformers. The RCs were tested in a high power laboratory. To verify the application for the arc furnace transformer differential protection. RCs were tested at 60 kA secondary current, representing an arc furnace load current. Test results demonstrated that the relay operates reliably at low fault currents of 3% of the rated current, allowing much lower setting than used in traditional differential protection schemes.