Which variable must be determined by the employer or utility prior to selecting grounding equipment?

Selecting grounding equipment for a substation involves understanding the types of fault conditions that the equipment will need to handle. The maximum time fault current can flow is crucial in this context. It directly influences the design and specifications of the grounding system since the equipment must be able to safely carry the fault current without overheating or causing damage.

If the fault current flows for too long, it could lead to equipment failure or unsafe conditions. Therefore, determining the maximum time the fault current can flow allows the employer or utility to select appropriate grounding conductors, connectors, and protective equipment that can withstand these conditions adequately. This consideration ensures that the grounding system is both effective and reliable during fault events, enhancing the safety and integrity of the electrical system within the substation.

While other options also relate to grounding equipment, they do not have the same direct impact on the specifications necessary for safe fault current management.