Traditional power systems rely on fossil fuels, which considerably harm the environment. A smart grid is an infrastructure that allows for the integration of renewable resources into the distribution system, as well as the possibility of establishing a two-way flow of energy and data between network management and subscribers to optimize energy consumption. However, attackers may use this data flow to compromise security and generate power network imbalances. With the ever-growing advancements in computing, cyber security concerns are also escalating, where a Smart grid (SG), being a networked distributed control system and exchanging electricity and consumption information with a high frequency, is also in jeopardy. Nevertheless, there is a notable lack of substantial efforts towards the development of practical secure solutions for power grids. This paper proposes a lightweight protocol designed to address security challenges in smart grid networks. The scheme integrates an authentication mechanism with ECC to securely generate session keys. The proposed protocol security has been evaluated through informal security analysis against a range of potential attacks in SG environment. The proposed protocol computational efficiency and suitability for smart grid devices are demonstrated by performance analysis.