Solar Transformer By V. S. Engineering

As the grid voltage is at 11kV, the output power from the LTPDB which is at 270V to 415V has to be raised to
11kV for grid synchronization. Hence 1 no of 1MVA 3-phase ONAN transformer is used. This will be oil filled transformer and will be placed on constructed plinth in
switch yard area. It is constructed of ventilated metal enclosure, removal type, and outdoor duty operating
under direct sunlight as per IS2026. However, marshalling box will be provided with IP 55. Winding material
is of electrolytic grade copper for both HV and LV windings with insulation class A.

Transformer will be having off circuit tap changer having 5 taps which ranges from -5% to +5% in the ranges
of 2.5% and these taps are helpful for adjusting according to the grid voltage against its fluctuations. Oil in
the tank also getscirculated through radiator tubes such that the natural air flow between the tubes cools
down the oil circulating in tubes and hence it is an Oil Natural and Air Natural (ONAN) system. From LTPDBs
power is fed to Transformer LV side in LV cable box and from HV cable box, power is taken and fed to
HT panels for relaying and protection. HV sealing kits are used for terminating the cables on HV
side of the transformer