Form-3 (Form of Separation) in Switchboards

This is the 3rd level of separation that comes in the Form of Separation called Form-3, in this Again it is divided into three categories.

Earlier we went through a detailed study about Forms of Separation, Form-1 & Form-2, now we move forward to understand another Form of Separation called Form-3.

In Form-3 there are three categories i.e. Form-3a, Form-3b Type-1 and Form-3b Type-2. Now, this is the level of live section separation from each other. We can say the Busbar and Functional Units including the Cable Connection going to be isolated from each other well.

(Whereas we use?‘a’?then it denotes the terminal is not separated from the busbar and when we use?‘b’?then it denotes the terminal is separate from the busbar.)

For the requirement to comply with Form-3 by any of three methods & these are totally specified by the customer/user and the manufacturer:-

Form-3a :-

In this form of separation, terminals are not separated from the busbar however functional units are separated by partitions and have barriers from terminals & busbars. (Refer to the figure above)

Form-3b 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 as well as from the functional units. (Refer to the figure above)

Form-3b Type-2 :-

In this criteria, the main Busbar is separated by metallic or non-metallic rigid barriers or partitions. Due to barriers or partitions on the above Busbars, terminals are separated from the busbars as well as from the functional units. (Refer to the figure above)

DO’s:-

1. Barriers and partitions should achieve a minimum IP2x level of Ingress Protection.
2. Although the standard does not show any protective covers over any cable connection area but needs to adhere to a mutual understanding between the customer and manufacturer.
3. Busbar Covering by Insulated material must be unique and with the identification of busbars.
4. A proper Gap should be there in between two cable terminations as all terminals come in one chamber.
5. Cable Arrangement must be according to the required cable sizes w.r.t. respective current rating.
6. Each and Every barrier or partition must achieve protection of ”Finger Touch Proof”.

DON’Ts:-

1. Do not forget to achieve an IP2x Level in each and every partition.
2. Covering over the busbar must not punch at any level to avoid any?accidents.
3. Metallic barriers should maintain minimum clearance and creepage from busbars or live parts w.r.t. IEC Standards.
4. Avoid direct termination over Switchgear, to avoid building stress and connection feasibility.