What mechanical issue can arise due to high currents in substations?

High currents in substations can create significant mechanical forces as they flow through conductors and other equipment. These forces can result from electromagnetic effects, specifically the interaction of electrical currents with magnetic fields, which can induce high mechanical stress. When the currents are exceptionally high, these forces might exceed the mechanical limits of certain components, such as grounding clamps, leading to physical damage or failure.

Grounding clamps are particularly vulnerable to these forces because they are designed to secure grounding conductors but may not be engineered to withstand excessive mechanical loads induced by high currents. This can result in the weakening or breaking of these clamps, which compromises system safety and reliability.

The other options focus on different potential issues related to high currents, such as electrical burns, overheating of transmission lines, and damage to voltage dividers; however, they do not specifically address the unique mechanical stress and forces that high currents exert on components like grounding clamps, making this option the most pertinent regarding mechanical issues caused by high currents.