Double-ended asynchronous polarity test system and method for high-voltage transmission line

The invention provides a double-ended asynchronous polarity test system for a high-voltage transmission line. The double-ended asynchronous polarity test system applied to a connecting cable between two substations comprises two sub-test systems and a data processor. One end of each of a first switch and a second switch of each sub-test system is connected with the connecting cable and the other is grounded. A current rising instrument arranged at each sub-test system, the first switch, and the second switch form a communication loop to provide a primary-side heavy current in a direction sameas the load current direction of the connecting cable. A first current transformer and a second current transformer that are arranged at each sub-test system is connected to different lines of the loop in a sleeving manner and the primary-side heavy current is converted into two to-be-measured secondary-side currents. A vector testing device arranged at each sub-test system is connected with linesof the first current tran