The utility model discloses an overhead transmission line developments increase-volume device, it relates to the transmission line control technology field. It includes ARM core processing module, temperature measuring module, microclimate measured module, arc hang down measured module, data communication module and power module, and temperature measuring module, microclimate measured module, arc hang down measured module and data communication module all to be connected with ARM core processing module electricity, power module respectively with ARM core processing module, temperature measuring module, microclimate measured module, arc hang down measured module, data communication module is electric is connected. The utility model discloses the change of hanging down of detectable transmission line's temperature and arc has improved service reliability, increases the short-term transmission capacity of circuit effectively safely, ensures the circuit safe operation.