The restructuring of the electricity supply industry that normally accompanies the introduction of competition provides a fertile ground for the growth of embedded generation [
12]. For the country like India, owing to the enormous gap between the generation and demand, and lack of transmission corridor to import power, the generation companies can show its dominance on the market. This anti-competitive practice may prevent competition in the electric power industry, especially in generation in the form of market power [
13]. Market power exists in restructured power systems when any of a generation companies exerts its influence on market pricing or on the availability of electric power. Market power may be defined as owning the ability by a seller, or a group of sellers, to drive price over a competitive level, control the total output or exclude competitors from a relevant market for a significant period of time [
13]. It reduces the competitiveness, quality and the impact of development in the field of technology. There is always a doubt that market power is being exercised regularly in many electricity markets [
14]. Many researchers have come out with various indices to measure market power. Herfindahl-Hirschman index (HHI), Lerner index, must-run ratio (MRR), must-run share (MRS), nodal must-run share (NMRS) and expected nodal must-run share (ENMRS) are some of them. Each index has its own limitations. MRS, NMRS and ENMRS are the indices which reflect the impact of load variation, transmission constraints and random failures on the market power respectively. In this paper MRS and NMRS are used to measure the market power.