The process of connecting an AC generator (alternator) to other AC generators is known as synchronization and is crucial for the generation of AC electrical power.
Operation Modes of Alternator
An alternator is an AC generator used mostly at power stations. The alternator is technically known as a synchronous generator. There are two modes of its operation:
Stand-alone operation: The alternator is operated isolated or connected to a DC supply via a rectifier. There is no need for synchronization in a stand-alone operation. An isolated example is a diesel engine-driven alternator used as a standby generator. An automotive alternator is used to recharge the battery with the aid of a three-phase diode rectifier.
Parallel operation: The alternator is connected with other alternators. This mode of operation takes place at power stations where many generators run in parallel. The generators are connected together via transformers and busbars and so a power network or grid is formed. The power grid is like a water pool and the generators are like pipes that supply the pool with water. The water is analogous to energy. The power grid is sometimes referred to as a power pool. The grid is also referred to as infinite busbar as far as synchronization is concerned. However, the infinite bus implies fixed voltage, frequency, phase sequence and phase angle. The grid is composed of different voltages and frequencies. Hence, it is technically said that an alternator is synchronized with the infinite bus.
Conditions
There are five conditions that must be met before the synchronization process takes place. The alternator must have equal line voltage, frequency, phase sequence , phase angle and waveform to that of the infinite bus.
In the past, synchronization was performed manually using three-lamp method. Nowadays, the process is automatically operated and controlled with the aid of synch relays and micro-electronic systems.
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