The time synchronization schemes based on a Global Positioning System and a wide area communication network can be combined to synchronize {HEAD ~ the stationary clocks} of phasor measurement units of a wide area monitoring system to {TAIL ~ a central server clock} at a Network Control Center of the system 
The time synchronization schemes based on a Global Positioning System and a wide area communication network can be combined to synchronize { HEAD ~ the stationary clocks } of phasor measurement units of a wide area monitoring system to { TAIL ~ a central server clock } at a Network Control Center of the system
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH