Increasing reliability of critical line feeder by upgrading protection using digital technology

Pilot Wire Relay and Pilot Monitoring Relay are electromechanical relays installed to protect long critical line feeder in PT Badak NGL. Pilot Wire Relay is a form differential relaying which protect longer lines through pilot wire, while pilot monitoring relay monitors the condition of pilot wire itself and gives transfer trip signal. However, Badak LNG has experienced two misoperations of auxiliary unit (TT) of pilot monitoring relay in 2009 and 2010. These misoperation was caused by activities of rack-in and rack-out vacuum circuit breaker at the same substation. Digital relay is the best solution to overcome this spurious trip problems because it is less sensitive to vibration and shock in addition to other several advantages such as: more compact in dimension, more complete protection, monitoring, metering and recording event.