A method for defining one or more ANM zones in an electricity network that has at least one energy producing/consuming device that has an output that has to be regulated. The method comprises determining the maximum power and/or current transmittable to or from a node or branch in the network at which an energy producing/consuming device that has to be regulated is to be added; determining the maximum capacity of power and/or current transmittable through that node or branch; and defining a zone (zone 1, zone 2) including the node or branch and regulated energy producing/consuming device that requires to be actively managed, in the event that the maximum power and/or current transmittable to the node or branch exceeds the maximum capacity of power and/or current transmittable through it.