Why alternators are synchronized in power plant?

Why alternators are synchronized in power plant?

    In power stations, alternators are operated in parallel to supply the total load. The need for parallel operation arises due to the following reasons.

     1. The total load requirement cannot be met by a singe alternator.

     

     2. Parallel operation increases reliability of electric supply. An outage of one alternator will not              cause total power loss to the load

     3. If alternators are operating in parallel, one or more of them can be shut down for preventive     

         maintenance in turn.

     

     4. Parallel operation of alternators leads to economy in operating costs. The less efficient machine          can be shut down when the load requirement is less.