Maximum load for medium voltage lines in N-1 conditions

•maximum value of the load connectible to an MV feeder is calculated•N-1 security criterion is fulfilled•Application to the whole distribution grid of Rome, Italy, is presented This paper proposes a methodology able to assess the maximum value of the load that can be connected to a medium voltage (MV) feeder in addition to the existing one without impairing the N-1 security criterion. A simplified approach is pursued, the original problem is split into several separate subproblems, and the maximum additional load is calculated solving multiple optimization problems. The proposed method is simple and practically applicable by distribution system operators (DSOs) that, after a request by a customer to connect a load, must know if an MV feeder is fit to host the additional demand or if a new infrastructure is needed. The application of the methodology to the whole MV distribution grid of Rome, in Italy, is presented; execution times show that the DSO can apply the model daily, to follow the load growth day by day.