Description
This applies when creating subnetwork controllers or importing subnetwork controllers.
The subnetwork name must be unique for the entire utility network. The only exception is when the subnetwork controllers exist within the same tier.
See Create a subnetwork and review the requirements section and the Subnetworks table to see the properties for existing subnetwork controller.
Solution
Ensure that the subnetwork name is not used for another tier in the utility network.