Over-current protection relay NA011

ACfor feederfor transformers

The relay type NA011 can be used in radial networks as feeder or power transformer protection. In solidly grounded systems the residual overcurrent protection can be used on feeders of any length, while in ungrounded or Petersen coil and/or resistance grounded systems, the residual overcurrent protection can be used on feeders of small length in order to avoid unwanted trippings due to the capacitive current contribution of the feeder on external ground fault. The NA011 protection relay may be shipped with traditional CTs or low power (LPCT) current inputs. For both versions, the residual overcurrent protection can use the measured (CTs or balanced transformer) or the calculated residual current. STANDARD PROTECTIVE & CONTROL ELEMENTS • Phase overcurrent side H and side L • Maximum Residual Overcurrent • Automatic Recloser • Breaker Failure