#formofseparation

[sandeepbishla]

Form 4 in Switchboards (Form of Separation)

INTRODUCTION The Main & primary function of Switchgear assembly partition/separation is to protect the maintenance or installer personal from any electrical risks (i.e. Internal Arc Flashes). It must be very well verified the IP level in line with international standards IEC60529. Related to my own journey in switchboards manufacturing, I personally experienced without knowing fundamental of Ingress Protection, it's very difficult to achieve From of Separation in Switchgear Assembly. ABOUT SELECTION OF FORM-4 The higher the form of separation level leads to more barrier and partition implant in switchboards but it again leads to poor ventilation, block airflow, and cover more space in the switchboard. At a higher level of separation restrict the maintenance area in switchboards and tracking of fault becomes more stringent to a quick resolution. Form-4 level of switchboards needs experienced electricians or engineers to access the zones in resolving any issue by removing multiple-barrier or partitions. In many applications, I personally experienced that Form-3b will perform better for ease of maintenance or accessibility of functional units, busbars, and cable chambers. Form-4 is highly recommended due to its property of inherently safe switchboard. Selection of Form-4 is very critical in many areas or applications where mass transportation or use in severe applications i.e. METRO, Shopping Malls, Gas Stations, Airports, Hospitals, etc. Although maintenance at this level is very stringent but very safe to do activities Functional unit wise which is having separate cable chambers. FORM-4 in DETAILS There are 7 ways for achieving Form-4 in switchboards by implanting barriers and partitions according to the design in two categories 4a & 4b. These barriers can be metallic or non-metallic area wise w.r.t. the live part protection. For the requirement to comply with Form-4 by any of 7 methods & these are totally specified by the customer/user and the manufacturer's mutual agreement w.r.t. IEC standards:-

FORM-4a in Details

FORM-4b in Details (Whereas we will use ‘a’ then it denotes terminal are inside the functional unit separated from the busbar and where we use ‘b’ then it denotes terminal outside the functional units separated from the busbar.)

FORM-4a explanation with relevant Pictures FORM-4a Type-1 Here 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 inside the functional units. (refer figure above) FORM-4a Type-2 Here the main Busbar is separated by a metallic or non-metallic rigid barriers or partitions. Due to barriers or partitions above Busbars, terminals are separated from the busbars but inside the functional units. Cable glands outside the panel and termination in the functional unit area. (refer figure above) FORM-4a Type-3 In this criteria, the main Busbar is separated by a metallic or non-metallic rigid barriers or partitions. Due to barriers or partitions above Busbars, terminals are separated from the busbars but inside the functional units. Cable glands and termination inside the functional unit area. (refer figure above)

FORM-4b explanation with relevant Pictures FORM-4b Type-4 Here 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 and functional units also separated by a metallic or non-metallic rigid barrier or partition. Cable glands outside the panel and termination in the functional unit area with a boot applied on cable termination. (refer figure above) FORM-4b Type-5 Here the main Busbar & Functional Units are separated by a metallic or non-metallic rigid barriers or partitions. Due to barriers or partitions above Busbars, terminals are separated from the busbars as well as from the functional units. Cable glands outside the panel and termination in the functional unit area with a boot applied on cable termination. (refer figure above) FORM-4b Type-6 Here the main Busbar and Functional Units with its individual Cable Chambers (Cable Connections Boxes) are separated by a metallic or non-metallic rigid barriers or partitions. Cable glands outside the panel and termination in its Individual Connection Box. (refer figure above) FORM-4b Type-7 This is the highest form of separation, here the main Busbar and Functional Units with its individual Cable Chambers (Cable Connections Boxes) are separated by a metallic or non-metallic rigid barriers or partitions. Cable glands are over the Individual Cable Connection Boxes inside the panels for cable termination inside it. (refer figure above) DO's Minimum IP2x level of Ingress Protection or achieve protection of ”Finger Touch Proof” in Barriers & Partitions.Epoxy/PVC Based Boots with Higher Temperature co-efficient must be used in Type 4 & 5.Busbar Covering by Insulated material must be unique and with the identification of busbars.Proper Gap should be there in between two cable terminations as all terminals come in one chamber in Type-4 & 5.Cable Chamber Boxes design must be in accordance with Cable Sizes & Arrangement w.r.t. respective current rating.Inside Cable Glanding required more space so it needs to take care of in design in Type 3 & 7.Cable chamber Gland Plates must be of a Higher thickness (Min.2.5mm or more) in Type 3 & 7.Gland Plates must use non-ferrous in the case of Single Core Cables.Except Type 3 & 7, Cable Chamber cover plates for cable entry must be cross-cut in between cable runs entry. DON'Ts Do not forget to achieve IP2x Level as well as protection of "Finger Touch Proof" in each and every partitions.Covering over the busbar must not puncher at any level to avoid any accidents.Metallic barriers should maintain minimum clearance & creepage from busbars or live part w.r.t. IEC Standards.Avoid direct termination over Switchgear, to avoid building stress and connection feasibility.Don't under design the Cable Chambers in Type 3 & 7.Boots sizes in such a way that it should cover the whole termination area.Cable Chamber Sizes should not oversizes than functional units sizes. Read the full article

[sandeepbishla]

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.

FORM-3 Classification Chart (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 :- Barriers & Partitions should achieve a minimum IP2x level of Ingress Protection.Although standard not shown any protective covers over any cable connection area but need to adhere by mutule understanding in between customer & Manufacturer.Busbar Covering by Insulated material must be unique and with the identification of busbars.Proper Gap should be there in between two cable terminations as all terminals come in one chamber.Cable Arrangement must be according to the required cable sizes w.r.t. respective current rating.Each and Every barrier or partition must be achieved protection of ”Finger Touch Proof”. DON'Ts :- Do not forget to achieve IP2x Level in each and every partitions.Covering over the busbar must not puncher at any level to avoid any accidents.Metallic barriers should maintain minimum clearance & creepage from busbars or live part w.r.t. IEC Standards.Avoid direct termination over Switchgear, to avoid building stress and connection feasibility. Read the full article

[sandeepbishla]

Form-1 (Form of Separation) in Switchboards

Form of Separation is categorized in many types, w.r.t. partitions & cable termination. We have to better understand that each & every partition must comply IP2x which is commonly denoted as Finger Touch Proof. Also, refer to the IEC Standard Guidelines. In any form of Separations, partitions play the main role to achieve that level. These partitions can be made of metallic or non-metallic, but in case of metallic there should an earth connection to make it shockproof. Form-1 of Separation always achieved without any extra efforts or we can say this is the form which is by default achieved whenever Switchboard manufactured. As there is no Separation and no need to cover any part from nearby functional units or we can say no barrier as well as Separation required in this Form-1. Although the outer enclosure must be there to collaborate/ fix all parts on a single plate. Here we have to understand that in Form-1 all incoming, outgoing, busbar area and cable termination area doesn't have any barrier or partitions in between, means cable terminations for incoming as well as outgoing both are in the same chamber. (See Figure)

Meter Board Wall-mounted DB Showing Form-1 Arrangements under preparation Form-1 is the common form of Separation where we need to lesser load capacity or small DBs (mainly wall mounted DBs). Normally these DBs ratings are up to a maximum of 200-250A due to Cable Connection capabilities. Although more this rating/capacity is not manufactured But in some countries (Like Korea, Japan etc.) they are utilizing it up to 630A, which are very stringent special applications.

FORM-1 (Form of Separation) in Switchboards There are major safety concern with this Form-1, but the major part play is Size of Switchboard, means in this lower rating if we are going to achieve next level of separation than each & every functional unit to be fixed in different-different feeders which makes the bigger size of Switchboards. As there is no separation/partitions so safety concern is bigger, so to minimize that below are do's and don't's:- DO's :- 1. The enclosure must be achieved IP2x Level of Ingress Protection. 2. There should be a proper gap between incoming and outgoing Terminals. 3. Top shrouding needs to fix on and above all functional units to prevent from direct touch. 4. Proper legends and marking must be provided for identifications of units and areas. 5. Ease of maintenance should be taken care of individual units on s single plates. DON'T's :- 1. Power connection & control connection must not be mixed in each other or not too closer to each other. 2. Incomer must not be mounted except than top most or bottom-most portion for better separation. 3. Don't forget to isolate Busbar Connections properly to prevent direct intact. 4. Avoid direct touch of live connections in case of Metallic Shrouding. Read the full article