Professional Answer: When multiple cables are grouped together in a single conduit, trench, or cable tray, they generate mutual heating. This leads to a cumulative temperature rise that restricts the heat dissipation of each individual cable. As a result, the ampacity of each cable must be derated to compensate for the reduced cooling efficiency. The derating factor applied depends on the number of cables, their spacing, and the overall installation method. We supply a variety of cable laying and stringing equipment designed to ensure proper spacing and arrangement, minimizing derating requirements and maximizing system efficiency.