Vegetation encroachment alongside power lines in urban and rural areas are a common cause of interruption in power energy supply. A system based on Wireless Sensor Network (WSN) is proposed to support in the control of the vegetation growth. Sensors modules can be installed sequentially in transmission lines to monitor the vegetation encroachment in transmission lines. Embedded devices containing microprocessors and radio communication modules were used in practical experiments to prove it effectiveness in the detection of the vegetation in this scenario. The experimental results demonstrated that the system meets the requirements of the proposal, being a viable and reduced cost option for the monitoring of transmission lines.