Part2: Minimum clearance of live parts

[tulum]

Hi Again,

Let me take the "Minimum clearance of live parts" post a little further.

I have the following splitter trough in my plant. It was made by a local switchgear manufacturer. The specs are given below:

Phases: 3
voltage: 600v
Current: 800A
Bus: Copper, non-insulated 1/2" x 1 1/2"
Phase to Phase spacing: 3"
Phase to ground Spacing: 1"
RMS sym Rating: 25KA
Insulator spacing: 7" (4 Insulators/phase, 33" bus,i.e. 6" overhang on ends)

This splitter was never tested. However, the manufacturer says that based on it's calculations, the KA rating is good (it's always good until a fault occurs...).

Does anyone think the above Fualt rating seems reasonable... maybe a formula...

Thanks again

Tulum

 

[stevenal]

T=(0.0857*A/I)^2

A is copper cross sectional area in circular mils. T is time in seconds.

25kA gives a 10s clearing time. Maybe the switch contacts are the limiting factor?

 

[jghrist]

The bracing may be the limiting factor instead of the thermal rating. You could try to apply the equations in IEEE Std 605, IEEE Guide for Design of Substation Rigid-Bus Structures.