<p>Energy reserve becomes major concern in developing high security and economic power distribution networks that have rapid expansion in electricity demand. Providing energy reserve from conventional generators is very challenging due to their physical constraints and high variation in loads. Therefore, this paper provides an optimization technique to procure spinning reserve through demand response aggregators DRA. The proposed model allows the DRA to interact with independent system operator ISO and end-user customers to trade energy in the electricity market. The proposed DRA robust model is designed based on multiple energy bidding prices and variable spinning reserve quantities to allow the enrollment of various participants. The mixed-integer linear programming method is used for the DRA model to merge the energy consumption cost and the spinning reserve cost in one linear optimization problem. The linear optimization problem allows the DRA model to contain high number of parameters, variables, and indices to reach the optimal economic decisions within a short time. The mathematical DRA model creates opportunities to maximize the possible energy reserve with the minimum accumulated operation cost. The operation of the existed generators and the availability of the spinning reserve are examined during high congestion of the transmission lines to ensure the effectiveness of the proposed model. Case studies of a power network with 10 generating units are used to inspect the availability of the spinning reserve provided by DRA.</p>