This paper analyzes the effect of dominated and dominating contingencies on the operational cost of the wholesale power market in Colombia. This type of analysis is important because the expansion of the power grid has been limited due to environmental constraints and, therefore, new operational procedures has been proposed to maximize the use of the exiting network. These new procedures impact the market so that a careful assessment of the impact is recommended before implementing. Numerical results shows that dominated contingences are an interesting approach with no major impact on the market.