A New Technique for Monitoring and Protection of Distribution Transformer during Single-Phasing Situation

The distribution transformer serves a significant purpose in the existing distribution grid. The distribution transformer may quickly switch from a three-phase to a two-phase power source in the event of a phase disruption or blown fuse from the primary side. In this instance, the secondary voltages may differ from the nominal phase voltage where LT consumers are connected. This is because the total secondary voltage depends on the actual primary voltages. This indicates that one voltage stays at the nominal level, but the other two do not. The magnetic permeability in each core limb, ampereturns, and core size all affect the voltage induced on the secondary side. The complex interactions between the elements above are considered when calculating these voltages using a comparable magnetic circuit. Under the worst unbalanced voltage condition on the secondary side due to single phasing on the primary side, this results in severe heating, power quality issues, losses, and transformer failure. Hence, this paper proposes a protection scheme against the single phasing condition of the transformer in the distribution system. An overvoltage relay, connected to the open delta-connected PT secondary detects the unbalance voltage condition on the distribution system.