Generation vs. Transmission/Distribution Transmission vs. Distribution
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
Substations are considered to be both transmission and distribution facilities
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.