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