Query on Low Voltage Switchgear Form 4b construction requirement as per IEC

[krisys]

I have a Low Voltage (LV) Switchgear constructed complying to IEC Form 4b construction. We need to carryout a site modification in the switchgear to install an 800A ACB feeder by combining three (3) nos. of spare 63A MCCB feeders in the switchgear.

Due to the constraints, ACB feeder outgoing side conductors (copper bars) are required to pass thru the live bus bar dropper compartment.

In order to maintain the Form-4b integrity, we provided two layers of insulation (one layer is with Reychem heat shrink sleeves and the other with rigid film polyester insulation material).

The LV Switchgear in question is Schneider Make, Okken type and about five (5) years old.

The question is : can this arrangement be technically acceptable as complying to Form-4b construction?

 

[ScottyUK]

No, it won't be a Form 4b design - in fact an Okken board in this configuration wouldn't meet any of the recognised standard forms.

BEAMA's guide explains the requirements for each form quite clearly, and it's a freebie instead of buying BS EN 61439.

 

[krisys]

ScottyUK,

Thanks for your quick views. Attachment is very useful.