Why the earthing transformer primary voltage is 16.5 kV rated in main generator even though actual voltage during the E/F is root 3 times less?

Why the earthing transformer primary voltage is 16.5 kV rated in main generator even though actual voltage during the E/F is root 3 times less?
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1 Answer

Answer :

The transformer should not saturate during E/F otherwise it will cause ferroresonance with the GT winding capacitance. Dangerous O/V and neutral shifting will occur. During loss of load or field forcing conditions, the transformer voltage increases to cause saturation. Saturation can also occur due to point on wave of application causing flux doubling. 
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