There exists characteristic differences between single/double circuit lines

such as line to line mutual inductance

cross line fault

etc. Which seriously restrict the application of single loop distance measurement principle in double circuit lines. This paper presents a research scheme of two terminal asynchronous fault location suitable for single/double circuit lines

or for single circuit and double circuit line at the same time. First

derive the fault location equation of two terminal asynchronous fault using double ended voltage amplitude ratio based on single loop network structure. Then

according to the amplitude ratio of voltage on both ends

a new location equation is given. Proceed from the network structure of double circuit line and asymmetric parameter and

based on equivalent transformation and six sequence transformation

relate single circuit line to double circuit line to enable the algorithm based on single circuit line to be used in double circuit line. Simulation results show that the proposed fault location method

even without synchronous sampling of two terminals

still has the advantages of two-terminal location of high precision on single and double circuit line. This work is supported by National Natural Science Foundation of China(No. 51477090).