Phase Drop in Distribution System.
Phase Drop in Distribution System. There may be the situation when one of the phases is not available to distribution transformer, may be due to operation DO-Fuse, Opening of jumper or purposely for load shedding etc. In this condition voltage on LV side is disturbed. Consider 11000/400 Volts Delta-Star distribution transformer. Out of three phase 11000 volts supply, one phase is open as shown in the figure. There are three primary coils P1, P2 and P3 and three secondary coils S1, S2 and S3 assembled on three cores of transformer limbs A, B and C. B is centre limb whereas A & C are side limbs as shown in figure. Case 1 When one phase say Y phase is open, primary P2 has normal line voltage V RB across it whereas primaries P1 and P3 are in series across line voltage V BR . The path of magnetic flux induced in the core is as shown in figure. As seen the flux p...