Calculate the insulation resistance value HV side for 1600 KVA, 20 KV/400 V three-phase transformer. Let the value of constant (C) be 1.5 for the oil-filled T/C with the oil tank at 20°C.
1. 187.5 mega ohm
2. 18.75 mega ohm
3. 15 mega ohm
4. 750 mega ohm
