Form-2 (Form of Separation) in Switchboards

Form of Separation is classified into four categories as well as further drill down to next levels of separation with its types as Form-2, 3 & 4 with their respective types and categories (classified as ‘a’ & ‘b’).

As we already discussed Form-1 in the previous blog so here, we discuss Form-2 & its categories, Form-2 is defining complete assemblies from the protection against contact with any internal parts/components and also busbars from the functional units where there is internal separation.

(Whereas we will use ‘a’ then it denotes terminal are not separated from the busbar and where we use ‘b’ then it denotes terminal are separate from the busbar.)

For the requirement to comply of Form-2 by any of three methods and this is totally specified by the customer/user and the manufacturer:-

FORM-2 (Form-2a)

In this form of separation, terminals are not separated from the busbar however functional units are in one chamber and having barriers from terminals & busbars. (refer figure above)

FORM-2 Type-1 (Form-2b Type-1)

In this criteria, the main Busbar is separated by the insulation applied on it e.g. PVC sleeving, wrapping, or coating. Due to covering over Busbars, terminals are separated from the busbars but not from the functional units. (refer figure above)

FORM-2 Type-2 (Form-2b Type-2)

In this criteria, the main Busbar is separated by a metallic or non-metallic rigid barriers or partitions. Due to barriers or partitions of Busbars, terminals are separated from the busbars but not from the functional units. (refer figure above)

DO’s :-

1. Barriers & Partitions should achieve a minimum IP2x level of Ingress Protection.
2. Busbar Covering by Insulated material must be unique and with the identification of busbars.
3. Cable Arrangement must be according to the required cable sizes w.r.t. respective current rating.
4. Each and Every barrier or partition must be achieved protection of ”Finger Touch Proof”.

Don’ts :-

1. Covering over the busbar must not puncher at any level to avoid any accidents.
2. Metallic barriers should maintain minimum clearance & creepage from busbars or live part w.r.t. IEC Standards.
3. Avoid direct termination over Switchgear, to avoid building stress and connection feasibility.