Sparky, most Main ground fault systems are shipped from the factory set at the lowest possible level for sensitivity and time. It is the responsibilty of the owner/engineer to decide what is an acceptable level of coordination.
For Square D main breakers from the factory, are usually set about 200A and .1 sec. A Square D 20A QO breaker will hold 200A for about 1 sec. There is no ground fault coordination unless the main breaker is adjusted.
Redsy,
Non-electronic trip circuit breakers are almost impossible to selectively coordinate, for short circuits above 10,000A regardless of whether they are series rated or not.
Fuses, on the other hand are relatively easy to coordinate, if they are drastically different case sizes (400A can coordinate easily with 60A, but a 100A will almost never work with a 60A).
From an engineer's point of view, selective coordination is not usually feasible, if there are no strict controls on component substitution. If I plan a job using Shawmut Amp-trap fuses there is nothing to prevent a future substitution of Bussmann Fusetrons, resulting in the loss of coordination.
