A probabilistic criterion to set interconnection ratings

Nowadays each Independent System Operator checks that in the interconnection lines the scheduled power flows do not exceed the operating limits. These limits are generally fixed to ensure a given level of security in the power system. In a deregulated system, such limits may represent a barrier to the free trade of energy due to the possible rising of zonal prices. Today the problem is simply solved by verifying that, after that an interconnection line has gone out of service, the remaining lines are able to transport the power that was flowing in the faulty line (first contingency security criterion). In the present paper, a different approach is proposed, based on probabilistic assumptions. The methodology developed under this approach is based on the consideration that the total costs for the customers (energy, system auxiliary services and undelivered energy) must be minimized. The methodology is applied to a case study where two zones linked by two interconnection lines are present and a sensitivity analysis in respect to economic parameters is carried out.