Phase to Phase rating of cut-outs

[Mbrooke]

I semi often encounter distribution substations with paralleled secondaries or large end transformers with low relative Z. The secondary neutrals are always grounded through a 2, 3 or 5 ohm reactor limiting L-G current to 10ka or less. However 3 phase fault currents calculate higher with typical cutouts employed out on the line starting outside the substation. Are ratings higher when considering a phase to phase fault?

 

[waross]

Normally the source impedance will have risen due to line reactance out at the field cutouts, with lower fault currents.
It could be a problem with cutouts close to the sub.

Bill
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"Why not the best?"
Jimmy Carter

 

[Mbrooke]

I see them close to the sub however, first few poles after the riser. It doesn't make any sense to me, but it somehow works?

 

[waross]

Well.- Sometimes cross arms catch fire. That may be related to your observations. grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Mbrooke]

Perhaps, lol.