ENTSO-E final draft of the Network Code on Operational Security
Each TSO shall include Internal and External Contingencies in the Contingency List. External Contingencies shall be defined in line with the methodology developed according to the provisions in the [NC OPS]. Each TSO shall differentiate between Ordinary, Exceptional and Out-of-Range Contingencies, taking into account their probability of occurrence. In the treatment of so classified Contingencies, each TSO shall apply the following principles:
a) each TSO shall classify Contingencies for its own Responsibility Area;
b) when and as long as conditions significantly increase the probability of an Exceptional Contingency, the TSO shall include this Exceptional Contingency in its Contingency List. The TSO shall determine the Remedial Actions necessary to maintain its Transmission System within Operational Security Limits or to mitigate the impact of Exceptional Contingencies as far as reasonably practical and economically efficient;
c) when and as long as out of the ordinary conditions increase the probability of an Out-of-Range Contingency, the TSO shall use all available economically efficient and feasible means under its control to prepare Remedial Actions to mitigate the impact of these very exceptional conditions;
d) each TSO shall determine the Ordinary and Exceptional Contingencies based on the up-to-date topology;
e) in order to account for Exceptional Contingencies with high impact on its own or neighbouring Transmission Systems, or with a high probability of occurrence, each TSO shall include such Exceptional Contingencies in its Contingency List. The included Exceptional Contingencies shall be reassessed and if necessary the Contingency List readjusted in the case of significantly changed operational conditions; and
f) each TSO shall contribute to the development of a common methodology and criteria for coordination and, as far as technically feasible and economically efficient, harmonization of the key principles for establishment of Contingency Lists across the Synchronous Areas.