The problem of“dual power supply single meter”refers to the use of one energy meter for the terminal load requiring dual power supply, which makes it difficult to determine which transformer area the power consumption of this load is calculated in when the dual power supply is switched. In practice, due to the poor communication of marketing and distribution integration, the dual power supply switching of important loads in the transformer area can not be handled in time, resulting in unqualified line loss. A dual power supply switching sensing method based on power line carrier communication channel impedance is proposed. When dual power switching occurs, the network of the transformer area to which the load metering point belongs changes. The change of input impedance here is sensed through the frequency sweep signal injected by the dual power metering point, so as to realize the automatic identification of dual power switching. Through the active sensing method,the sensing function of dual power switching is increased while retaining the original metering function. By setting a reasonable decision threshold, several groups of confirmatory experiments proved the effectiveness and scientificity of the proposed method.