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Q) Explain how paralleling of generator’s carried out.

Ans:- Parallel Operation of Generators:-

  • Depending upon the capacity and the electrical load, more than one alternator can be connected to the common Bus bars. The connecting process is called ‘Synchronising’ i.e. enabling the parallel operation of the alternators.
  • Following conditions must be fulfilled for paralleling the Alternators:
    • Voltage must be same.
    • Frequency must match.
    • Phase sequence must be correct.
  • In short, the incoming alternator should have the same parameters as the running alternator(s). If the speed of the incoming machine is different, the ‘governor control switch’ should be used to adjust the speed.
  • Departure from the above conditions will result in the formation of power surges and unwanted electro-mechanical oscillation of rotor which will damage the equipment.
  • To carry out the paralleling operation, following devices are provided:
    • Synchroscope
    • Lamps (Dark/Bright)
  • Following are the steps to carry out with paralleling using a synchroscope:
    • Check voltages are same.
    • Check frequency of incoming generator is same as running generator.
    • Put on synchroscope and see that pointer turns slowly in clockwise direction (may require to adjust speed of incoming generator using the ‘governor control switch’ for this).
    • When the pointer is at 11 o’clock position, close the breaker of incoming generator.
    • Now the load is equally distributed among the generators.
  • Advantages of Parallel Operating Alternators
    • For maintenance or inspection, one machine can be taken out from service and the other alternator can keep up for the continuity of supply.
    • Load supply can be increased.
    • During light loads, more than one alternator can be shut down while the other will operate in nearly full load.
    • High efficiency and operating cost is reduced.
    • Ensures the protection of supply and enables cost-effective generation.
    • Reliability of the whole power system increases.