1. In the transmission line, on the top of the tower of the transmission line is two thin ground wires (also known as lightning conductor), and the one below the ground wire is called the conductor. Usually, the AC line wire has 3 phases, so when the wire is a multiple of 3 for the AC line, 3 lines called single loop, 6 lines called double loop, 12 lines called four loop; A DC line usually has a two-phase conductor, so a multiple of two is a DC line. Therefore, the most direct way to distinguish between AC and DC is to count whether the wires are multiples of 2 or 3.

2. According to the shape of the tower to quickly identify AC and DC.

Most towers on direct current transmission lines are shaped like "T" or Chinese word: "干".

There are various types of iron towers for AC transmission lines, including glass type, cat head type, upper type, drum type, pull V-type, and other structures.