Intern turn winding fault can be easily detect by differential protection relay.
Also detect by buchholz relay (gas operated relay), cause buchholz relay is used to detect the internal fault of transformer.
Maximum permissible load = Rated MVA rating*fraction of rated kVA
Maximum permissible load = 15*1.25
Maximum permissible load = 18.75 MVA
The magnitude of earth fault current for a given fault position within a winding demands upon the winding connections and method of neutral grounding.
Earth fault protection for an electric motor is provide by instantaneous relay having a setting of approximately 30% of motor rated current in the residual circuits of two CTs and with ground wire.
For single phase induction motor,
P = VIcosφ
P = 400*30*0.7
P = 8400 W
Q1 = P*tan(φ) = 8400*1.020
Q = 8568.82 VAR
Now power factor change to 0.9
So, φ' = 25.84 degree
Q = 8400*tan(25.84)
Q = 4067.95
Qnet = Q - Q'
Qnet = 8568.82 - 4067.95
Qnet = 4500.8
C = V²/(2ᴨf)
C = (400*400)/(2ᴨ*50)
C = 8.95*10⁻⁵
C = 89.5 μF