Why are 600-Volt rated cables often over-insulated?

The reason 600-Volt rated cables are often over-insulated relates primarily to their application in ungrounded electrical systems. In such systems, the potential for elevated voltage stress occurs, especially during fault conditions. Over-insulating these cables helps to mitigate the risk of electrical breakdown or insulation failure, which is crucial for maintaining safety and performance in ungrounded systems.

Ungrounded systems can see a significant increase in voltage to ground during a fault condition, so having thicker insulation on the cables is a proactive measure to ensure they can safely handle these abnormal conditions without compromising their integrity. Proper insulation helps prevent incidents such as flashover, which can lead to serious safety hazards and equipment damage.

Other options refer to specific technical standards or different operational characteristics, but the primary concern for the use of over-insulation in the context of 600-Volt cables revolves around the unique challenges presented by ungrounded electrical systems.