During which condition is a transformer bank likely to experience issues related to ferro-resonance?

A transformer bank is likely to experience issues related to ferroresonance primarily when it is under lightly loaded conditions on the secondary side. Ferroresonance occurs when the nonlinear magnetic characteristics of the transformer interact with the capacitance in the system, which is more pronounced under low load conditions. In situations where the transformer is not supplying significant current, the capacitive effects can dominate, leading to unexpected resonant frequencies.

This condition often manifests when circuit elements such as cables and switches are connected, and the inductance of the transformer combines with the system capacitance to create a resonant circuit. As the secondary loading decreases, the susceptibility to ferroresonance increases. This can result in over-voltages and erratic operation, which can damage equipment or cause instability in the circuit.

Understanding the operational characteristics of transformers, especially in relation to load conditions, is vital for preventing such phenomena in power distribution systems. In practical terms, maintaining a sufficiently loaded transformer helps to mitigate the risks associated with ferroresonance.