The power transmission line is one of most critical components in electrical power system. In order to enhance the reliability of the large power systems, an advanced and efficient Wireless Sensor Network (WSN) must be employed along power transmission line. However, time delay has emerged as one of the most critical issues in the design of WSN-based monitoring network of transmission lines. This paper proposes a new model for WSN for monitoring High Voltage Transmission Line (HVTL) which improves the needed time delay to transmit the measured quantity from transmission line towers to the control center. The proposed design considers the broadband power line communication (BPLC) technologies to transmit the collected data from group of towers to the nearest substation. To evaluate the performance of proposed model, the maximum time delay in data flow for the proposed model is determined in mathematical form and compared with other common models. The results of this paper demonstrate that the maximum time delay of proposed model less than the other common models, especially when advanced wireless communication, such as 4G and 5G, is used between the relay nodes. Based on the simulation results, the proposed WSN-based transmission line monitoring is efficient, powerful, reliable, and applicable to meet the smart grid requirements.