A maintenance coordination algorithm is proposed in this paper in which, the natural gas network constraints and uncertainties are taken into account. In this way, new communication lines between natural Gas Network Operator (GNO), Independent electricity Market Operator (IMO) and Independent electric System Operator (ISO) are created to coordinate the mid-term planning of the electric and the gas networks. The coordination process is an iterative process in which, initially, the GNO generates a complete set of non-electrical gas load scenarios. Then, the scenario-based maximum available gases for generating units are calculated and sent to the IMO and the ISO. The IMO declares the interval electricity prices in scenarios for the period of concern. The Generation Companies (GenCos) would then provide the ISO and the IMO with their maintenance proposals; considering their own objectives, constraints, scenario-based prices, and scenario-based maximum available gases. The ISO would evaluate the impact of maintenance proposals and scenario-based maximum available gases on reliability indices and assign some penalties/rewards to the GenCos, in proportion to their contribution in reliability index violation from a desirable level. On the other hand, the GNO would calculate the new scenario-based maximum available gas for the generating units, considering new maintenance proposals. Then, the IMO would provide new electricity prices, based on new maintenance proposals. These signals would be used by the GenCos to review and modify their maintenance proposals. The procedure is repeated until an equilibrium point is reached. For convergence assurance, a memory rate is introduced by which the GenCos earlier experiences in providing the ISO with maintenance proposals are, somehow, taken into account. The capabilities of the proposed algorithm are assessed and evaluated on IEEE-RTS.

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