Parallel Operation of a Transformer


Parallel Operation of a Transformer

Parallel Operation of a Transformer is when their primary windings are connected to a common voltage supply, and the secondary windings are connected to a common load. For supplying a load in excess of the rating of an existing transformer, two or more transformers may be connected in parallel with the existing transformer. The transformers are connected in parallel when load on one of the transformers is more than its capacity.

The reliability is increased with parallel operation than to have single larger unit. The cost associated with maintaining the spares is less when two transformers are connected in parallel.

Necessity For Parallel Operation

  • When load is increased and it exceeds the capacity of existing transformer, another transformer may be connected in parallel with the existing transformer to supply the increased load.
  • If there will be any breakdown of a transformer in a system of transformers connected in parallel, there will be no interruption of power supply, for essential services.
  • For expansion of a substation to supply a load beyond the capacity of the transformer already installed.
  • If multiple transformers are running in parallel, and a fault occurs in one transformer, then the other parallel transformers still continue to serve the load. And the faulty transformer can be taken out for the maintenance.
  • If we run numbers of transformers in parallel, we can switch on only those transformers which will give the total demand by running nearer to its full load rating for that time. When load increases, we can switch none by one other transformer connected in parallel to fulfill the total demand. In this way we can run the system with maximum efficiency.

Condition for Parallel Operation of Transformer

  1. Same phase sequence
  2. Same percentage impedance
  3. Same Voltage Ratio
  4. Same polarity

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