{TAIL ~ U0} and {HEAD ~ P0} are a nominal voltage and nominal active power, respectively, as measured prior to the contingency 
{ TAIL ~ U0 } and { HEAD ~ P0 } are a nominal voltage and nominal active power , respectively , as measured prior to the contingency
TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH