the one line diagram on power distribtion line

This is how the electrical line goes on see the following list.

1. The 138 kilo volt - 138 kilo volt or 138 kv is the inter connected
lines from different source like hydro, diesel, coal power plant. etc.
most of this line are installed across the forest using a tower with
a span between tower approximate 300 meters if it is in straight line.
The main purpose of this is to supply the step down transformer from
138 kv to 69 kv.

2. The 69 kilo volt - is the source needed to convert 69 kv primary
side to 13.8 kv secondary of the transformer 69 kv can be seen along
the highway or across the forest also but some utillty they did not
install across the forest for the reason that cannot attain immediately
in time of broken pole or construction the spanning of 69 kv between line
approximately 150 meters and erected and concrete pole 75 footer, with
no. 4/0 acsr or 336.4 acsr.

3. The 13.8 kilo volt - 13.8 kv is the output voltage of a three phase
Power transformer from what we called substation sometimes only one
transformer but it produced three to five feeders. This feeders is 13.8
or 13.8 kv 3 phase line can supply 3 transformer or 3 phase single
transformer but if you need single phase transformer 7620/240 volt much
better bacause you can tap only one line of a three phase line.