Experimental Study of Magnetic Effects of Steel Tanks on Three-Phase Transformer Transients

This paper presents an experimental study of the magnetic effects of steel tanks on different three-phase transformers. Removable steel tanks are designed and built for transformers with distinct sizes and core topologies. Corresponding tanks of nonmagnetic materials are also built to study the effects of tank material. Zero-sequence tests, open-circuit (no-load) tests, ferroresonance, geomagnetically induced current (GIC), and energization (inrush current) tests are performed on the transformers with and without tanks. The results indicate that steel tanks have a significant effect on the zero-sequence impedance, ferroresonance performance, GIC, and no-load losses in steady state, while the tank has no appreciable effect on inrush currents.