[1] Synchronizing AC generators -- Part 1 (introduction and sync lamps)
[2] Synchronizing AC generators -- Part 2 (strobe light view)
[3] Synchronizing AC generators -- Part 3 (sync and unsync)
[4] Synchronizing AC generators -- Part 4 (phase deviation)
The first video explains all the concepts and shows a sync, but the later videos bring additional conditions and detail.
[1] https://www.youtube.com/watch?v=RGPCIypib5Q [2] https://www.youtube.com/watch?v=sFohkp2aaU4 [3] https://www.youtube.com/watch?v=GRk_qJxaxh8 [4] https://www.youtube.com/watch?v=RT1ySBc-Bls