Synchronizing Two Alternators

Usually one speaks of synchronization in terms of:

1. Live line, dead bus = the circuit breaker that ties the line to the bus can only be closed if the line has acceptable voltage (magnitude and frequency) and the bus is dead (no voltage).

2. Dead line, live bus = the breaker can only be closed if bus voltage is acceptable and the line is dead.

3. Live line, live bus = the breaker can only be closed if both the bus and line voltage are at acceptable voltage and frequency, and the AC waveforms are synchronized within a specified number of degrees of phase angle.

Dead = no present voltage as reference

Live is opposite with dead.

Dear Friend! What is Synchronising? It is manipulating the parameters of the incoming machine with respect to the bus to which it is to be synchronised. Isn't it? If so, how will you synchronise the first machine to the bus, with the bus being dead? The synchronsing scheme turns blind in such a situation and this is called "Dead Bus" Synchronisation. If the bus is already having voltage (i.e.) it is live, then the synchronisation of any incoming machine to this bus is called "Live Bus" Synchronisation.

In transmission systems, "synchronization" is not always a machine (generator) to a bus. It could be a line to a bus, and some of the conditions can be "dead line, live bus" or "live line, dead bus." Those are the terms used, even if you are not adjusting voltage magnitude, frequency, and phase angle between a live section and a dead one. Even live line to live bus synchronization generally doesn't have local adjustment possible, but that the synchronization relays need to supervise the closing to operate the breaker at a point when the waveforms are in sync.