The concept of transmission towers, transmission conductors are supported by sections of transmission towers. High voltage lines use “iron towers,” while low voltage lines, such as those seen in residential areas, use “wooden poles” or “concrete poles.” Together, they are collectively referred to as “towers.” High voltage lines require a larger safety distance, so they need to be erected at a greater height. Only iron towers have the capacity to support tens of tons of lines. A single pole cannot support such a height or weight, so poles are generally used for lower voltage levels.

There are generally two methods for determining the voltage level:

1.Pole number plate recognition method

On the towers of high-voltage lines, pole number plates are usually installed, clearly indicating different voltage levels such as 10kV, 20kV, 35kV, 110kV, 220kV, and 500kV. However, due to long-term exposure to wind and sun or environmental factors, the pole number plates may become unclear or difficult to find, requiring close observation to read them clearly.

2.Insulator string recognition method

By observing the number of insulator strings, the voltage level can be roughly determined.

(1) 10kV and 20kV lines usually use 2-3 insulator strings.

(2) 35kV lines use 3-4 insulator strings.

(3) For 110kV lines, 7-8 insulator strings are used.

(4) For 220kV lines, the number of insulator strings increases to 13-14.

(5) For the highest voltage level of 500kV, the number of insulator strings is as high as 28-29.