1910.269 does not make a distinction between transmission and distribution systems, but important potential safety differences do exist between them. For the benefit of those who do not work in Transmission and Distribution (T&D), the following information is provided:

• Transmission lines and equipment are used to move large quantities of power from generating facilities to substations. Transmission conductors are normally large to carry the high power and are installed on taller structures than distribution lines and equipment.

• Transmission system voltages are typically from 69KV up to 765KV.

• Distribution systems typically operate in a voltage range of 4KV to 46KV. However, distribution also includes secondary voltage systems, which operate at less than 1,000v, that typically connect to electric customers' homes and offices.

• Substations are considered to be both transmission and distribution facilities in 1910.269.

Work on T&D systems is frequently done with the lines and equipment energized. This is often because the system loading or its configuration, or both, makes it impossible to deenergize the system, or because continuity of customer service must be maintained. Working safely on energized T&D lines and equipment requires very specific work techniques that are unique to power generation, transmission, and distribution; these are addressed throughout the "269" standard and this eTool.

Substations
Generation vs. Transmission/Distribution
Energized vs, Deenergized Work