Which situation is more likely to create ferro-resonance in a transformer bank?

Ferro-resonance is a phenomenon that can occur in electrical systems, particularly with transformers and long cable runs. This condition is typically associated with systems that have a combination of inductance and capacitance, leading to non-linear oscillations.

When considering the situation that is most likely to create ferro-resonance, feeding a transformer bank with a considerable length of underground cable from a riser stands out. Long underground cables have inherent characteristics, such as capacitance, which can interact with the inductance of the transformer. This interaction can lead to resonant conditions, especially if there are any non-linear components in the circuit, such as the transformer core itself, which can saturate under certain conditions.

In this case, the considerable length of the underground cable can increase the capacitance significantly and, when combined with the inductive nature of the transformer, sets the stage for ferro-resonant behavior. Such a configuration can result in voltage oscillations that can potentially harm equipment if not properly managed.

Short underground cables typically do not have enough capacitance to create the conditions favorable for ferro-resonance. High voltage overhead lines mainly deal with issues related to arcing and line inductance but are less likely to foster ferro-resonance compared to underground cables