LOAD DISTRIBUTION OF TRANSFORMER DURING PARALLEL OPERATION
How To Compute The Load Distribution of Transformer During Parallel Operation?
If parallel operated transformers have the same voltage ratio but different short circuit impedance, then the load is distributed among them in such a way that each transformer accepts a specific level of load for which the short-circuit impedance becomes the same for all the parallel operated transformers.
When none of the parallel operated transformers is permitted to be overloaded, the transformer with the minimum short-circuit impedance must operate at maximum under its rated power. Consequently, the load distribution is given by the following equation:
Example 1.8
Let us assume that three transformers operate in parallel. The first transformer has 800 kVA rated power and 4.4% short-circuit impedance.
The rated power and the short-circuit impedance of the other two transformers is 500 kVA and 4.8%, and 315 kVA and 4.0%, respectively.
Calculate the maximum total load of the three transformers.
Solution
From the above, it is concluded that the maximum total load (1460 kVA) represents 90.4% of the total installed power (1615 kVA).
It should be noted that, in order for the maximum total load to be equal to the total installed power, the transformers must have the same short-circuit impedance.
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