Wireless Sensor Networks (WSNs) security plays an intrinsic role to guarantee efficient data transmission, stable network topologies, and robust routing algorithms. In this paper, we propose a modified Stackelberg game of a previous work for high assurance of data trustworthiness in a Power Grid Network (PGN). The proposed approach is presented to mitigate a more severe attack scenario compared to that considered in the previous work; this attack scenario frequently manipulates sets of the deployed nodes in the PGN, which cannot be treated using the previously proposed approach. Our proposed scheme reduces the required number of nodes to be protected to achieve the desired data trustworthiness. Simulation results prove efficient detection for corrupted transmitted data based on limited number of nodes as compared to the previously proposed approach.