What causes asymmetrical current in a substation?

Asymmetrical current in a substation is primarily caused by a large amount of inductance from reactors and transformers. When inductive components are present in a power system, they can create situations where the current is not evenly distributed among the phases. This occurs because inductors resist changes in current flow, which can lead to phase shifts and imbalances in the currents.

When the inductance is high, it can cause the current waveform to deviate from the ideal sinusoidal shape, leading to asymmetry. This can occur in scenarios such as single-phase loading on a three-phase system or during fault conditions, where the reactance of the transformers and reactors may further contribute to the imbalance.

In contrast, conditions such as low inductance or balanced loads do not contribute to asymmetrical current; balanced loads would distribute the current evenly among the phases, ultimately resulting in symmetrical currents. The absence of equipment might suggest a simple system with minimal complexity, which is unlikely to generate asymmetrical currents. Therefore, the presence of significant inductive elements is the main factor contributing to asymmetrical current in a substation.