If the service is a solidly grounded wye of more than 150V to ground but not more than 1,000V phase to phase, each service disconnect of 1,000A or more must have ground-fault protection [230.95]. This does not mean you can’t provide such protection for service disconnects rated under 1,000A; it’s just not required by Code that you do so.
Don’t try to “save money” if you can get by without such protection and still meet Code. Evaluate the system from an engineering best practices perspective rather than a “cheaper is always better even if it ultimately costs more” perspective.
In some cases, you are not going to want this protection. For example, if the application is a continuous industrial process where a nonorderly shutdown will introduce new hazards or increase the existing ones. The NEC grants an exception for that particular circumstance.
The maximum rating of the ground-fault protection is 1,200A [230.95(A)], with a maximum time delay of one second where ground-fault currents are 3,000A or more.
