The clearance requirements for HV and LV terminals in the air are as follows:
For 66 kV side, the phase-to-phase and phase-to-earth clearance should be 700 mm, and 660 mm respectively.
For 12 kV side, the phase-to-phase and phase-to-earth clearance should be 280 mm, and 140 mm respectively.
The following points should be noted for designing winding of the transformer
The winding conductor shall be of electrolytic grade copper of 99.90% purity.
The insulating spacers, and the barriers are used to ensure a free circulation of the oil in the windings.
The dielectric strength of winding insulation shall confirm to values given in IS: 2026.
All threaded connections in the winding shall be provided with locking facilities.
The winding conductors are transposed at sufficient intervals to minimize eddy currents and to equalize the distribution of currents and temperature along the winding.
The following points to considered for designing tap changer of the transformer