Lug-Insulation Gap

[salgant]

I am trying to find a standard showing what the maximum gap can be between a lug and insulation. My cable size is 350mcm. The conductor is inside of a closed and lockable disconnect box in a PV array.

 

[Elect117]

Insulation is used to avoid arcing, flashing over, and faults to grounded equipment. I am unsure if you are asking about wire insulation being stripped or the insulations between landings to avoid arcing inside of the disconnect.

In either case, it is a rather complicated answer.

The resistivity of free air, distance to the point of difference of potential, the peak difference of potential, etc.

Maybe the equipment manufacturer can help you out?

 

[salgant]

Insulation is used to avoid arcing, flashing over, and faults to grounded equipment. I am unsure if you are asking about wire insulation being stripped or the insulations between landings to avoid arcing inside of the disconnect.

In either case, it is a rather complicated answer.

The resistivity of free air, distance to the point of difference of potential, the peak difference of potential, etc.

Maybe the equipment manufacturer can help you out?

Insulation is used to avoid arcing, flashing over, and faults to grounded equipment. I am unsure if you are asking about wire insulation being stripped or the insulations between landings to avoid arcing inside of the disconnect.

In either case, it is a rather complicated answer.

The resistivity of free air, distance to the point of difference of potential, the peak difference of potential, etc.

Maybe the equipment manufacturer can help you out?

Do you recommend a product, either electrical tap or cold shrink to rectify this other than retermination? gap up to 1/2"

 

[petersonra]

I am trying to find a standard showing what the maximum gap can be between a lug and insulation. My cable size is 350mcm. The conductor is inside of a closed and lockable disconnect box in a PV array.

Simple answer is if it bothers you get some insulation and insulate it. Black tape or heat shrink comes to mind. This is not rocket science.

Note that this answer would not apply if you are dealing with MV conductors. That would complicate things. But for under 600 Volts, the answer is simple.

 

[jaggedben]

Yeah, what is the voltage?

 

[jaggedben]

Honestly if we are just talking about a DC conductor at under 1500V that's been stripped back 3/8" of an inch farther than it needed to be from a lug in a properly rated disconnect I suspect this is much ado about nothing.

 

[jim dungar]

As long as the conductor still 'sticks past' the insulation around and between the lug assembly there is no issue at all, along as the voltage is less than 1000V.

I have always been amazed at the people that think the conductor insulation needs to be touching an uninsulated lug.

 

[pv_n00b]

There will generally be strip lengths provided by the termination manufacturer and using those is the way to go. Without that, a general rule of thumb is that the exposed conductor should not be more than the diameter of the conductor. For 350kcmil that gives you a little over a half inch, 0.681". As a fix for too much being exposed, as has been discussed, some type of applied insulation to close the gap.