a protective relay for producing {TAIL ~ a breaker opening command} when {HEAD ~ a fault} occurs on a load side of the breaker 
a protective relay for producing { TAIL ~ a breaker opening command } when { HEAD ~ a fault } occurs on a load side of the breaker
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH