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# Fall-of-potential C2 distance

1. Junior Member
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## Fall-of-potential C2 distance

How do you figure out the distance required for a 3-point fall of potential test? I've heard you should drive your C2 anywhere from 3 to 10X the diagonal of the grid but I've seen other literature that give tables showing different values based on different distances.

To keep things simple, let's say we had a building that was 100' x 200', how far out would you take your leads?

This slide shows 10X diagonal.

This slide shows non-linear percentages.

2. Junior Member
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Apr 2018
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Originally Posted by marvinray
How do you figure out the distance required for a 3-point fall of potential test? I've heard you should drive your C2 anywhere from 3 to 10X the diagonal of the grid but I've seen other literature that give tables showing different values based on different distances.

To keep things simple, let's say we had a building that was 100' x 200', how far out would you take your leads?

This slide shows 10X diagonal.

This slide shows non-linear percentages.

Extract of IEEE Std 81.2-1991
it states to use 6.5 times the substation diagonal length/distance

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