What is the cause of asymmetrical current in substations?

Asymmetrical current in substations can primarily be attributed to the large amount of inductance present from transformers and reactors. Inductance plays a crucial role in the behavior of current and voltage in alternating current (AC) systems. When a fault occurs or when there are sudden changes in load, the inductive components can cause a lagging effect in the current, resulting in an imbalance. This can create conditions where the current does not flow uniformly, leading to asymmetrical waveforms that deviate from the ideal sinusoidal shape. This phenomenon is particularly significant in transformers and reactors because their design and operation inherently contribute to this inductive behavior.

In contrast, high resistance in circuits can lead to voltage drops but does not predominantly cause asymmetrical current. Similarly, while capacitors can influence current flow and system stability, they are generally associated with leading currents rather than asymmetry. Finally, low voltage from feeders can affect overall system performance but does not directly cause asymmetry in the way inductive components do. Thus, the presence of substantial inductance is the key factor that leads to the phenomenon of asymmetrical currents.