What is a factor in selecting between 100%, 133%, and 173% Medium voltage cables?

Choosing between 100%, 133%, and 173% medium voltage cables primarily involves considering the ground fault clearing time. In the context of medium voltage systems, the ground fault clearing time is crucial as it relates to the ability of the cable insulation to withstand potential fault conditions.

When a ground fault occurs, the insulation must be able to handle the stress induced during the fault until the protective devices can isolate the fault. The percentage ratings correspond to the cable’s ability to withstand these transient conditions, with higher percentages typically offering more robustness against faults.

When selecting cables, factors such as current capacity and voltage rating are also important but are more related to system design and load handling capabilities rather than directly addressing safety and performance under fault conditions. Similarly, the length of the installation is relevant to voltage drop and overall system efficiency but does not dictate the specific rating needed to manage ground faults.

Thus, ground fault clearing time stands out as the critical factor in the selection process when evaluating the percentage ratings of medium voltage cables.