In this subchapter the following definitions shall apply unless the context otherwise clearly demands:

(1) "Interruption" means a loss of service to one or more customers.

(2) "Interruption duration" means the period of time, in minutes, between the time an electric utility first becomes aware of a service interruption and the time of restoration of service to the customer(s).

(3) "Major event" means a catastrophic event that:

(a) for regulated electric utilities that have adopted the Institute of Electrical and Electronic Engineers Guide for Electric Power Distribution Reliability Indices, meets the definition of "major event day," standard 1366-2003; or

(b) for regulated electric utilities that have not adopted the Institute of Electrical and Electronic Engineers Guide for Electric Power Distribution Reliability Indices:

(i) exceeds the design limits of the electric power system;

(ii) causes extensive damage to the electric power system; and

(iii) results in a simultaneous sustained electric service interruption to more than 10% of the customers in an operating area.

(4) "Operating area" means a geographical subdivision of an electric utility's Montana service territory that is a distinct area for administration, operation, or data collection. These areas may also be referred to as regions, divisions, or districts.