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