Parallel heating cable is limited to the using length, so there will be more intermediate power supply unit when parallel heating cable is used for long distance heat tracing. Therefore, it increases the expenses and the burden of maintenance. Series heating cable is especially suitable for long distance heat tracing. One power supply can be used as long as hundreds of meters. Moreover, series heating cable can uniformize the heat along the pipe. Connected with 380 voltage current, series heating cable can balance the power load. Temperature controller with PT100 temperature sensor and monitoring can realize accurately automatic temperature control.