Answer / pravin borkar

The choice of 25 kV was related to the efficiency of power transmission as a function of voltage and cost, not based on a neat and tidy ratio of the supply voltage. For a given power level, a higher voltage allows for a lower current and usually better efficiency at the greater cost for high-voltage equipment. It was found that 25 kV was an optimal point, where a higher voltage would still improve efficiency but not by a significant amount in relation to the higher costs incurred by the need for greater clearance and larger insulators.

Answer / senthil nathan

as per load requirement(TRACTION MOTOR, DC SERIES WOUND
MOTOR 782V, 250AMPS) They have selected this 25kv. because
using transformer power can not be varied voltage or
current may vary but power remains same.

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