Form-3 (Form of Separation) in Switchboards

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

Earlier we have gone through the detailed study about Form 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 Busbar and Functional Units including Cable Connection going to be isolated from each other well.

(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-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 having barriers from terminals & busbars. (refer 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 figure above)

Form-3b 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 on above Busbars, terminals are separated from the busbars as well as from the functional units. (refer figure above)

DO’s :-

1. Barriers & Partitions should achieve a minimum IP2x level of Ingress Protection.
2. Although standard not shown any protective covers over any cable connection area but need to adhere by mutule understanding in between customer & Manufacturer.
3. Busbar Covering by Insulated material must be unique and with the identification of busbars.
4. 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 be achieved protection of ”Finger Touch Proof”.

DON’Ts :-

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