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