Forms of Separation for Panel (PART-2)

(C) Form 3

• This is more complicated but safer than Form 2.
• In form 3a, each device is isolated in a compartment that protects it from the effects of any incidents that may occur on another Part / Switchgear.
• Busbars and functional units are segregated. Functional units are also separated from each other in cubicles, and terminals are then separated from functional units, but they are not segregated from other functional units’ terminals.
• Busbar and Switchgear: Bus bars are separated from the Switchgear units,
• Busbar and Termination: Bus bars are not separated from any incoming or outgoing terminations.
• Switchgear and Switchgear units: Switchgear units are separated from each other.
• Switchgear and Termination: Switchgear units are separated from any incoming or outgoing termination.
• Termination and Termination: Incoming and outgoing terminals are not separated from each other
• This is further classified into 2 categories.

FORM 3A

• External cabling terminals are not segregated from busbars.

FORM 3B

• External cabling terminals are separated from busbars

FORM 3B TYPE 1

• As from 3 but: Busbar separation is achieved by insulated coverings, e.g. PVC sleeving, wrapping or coating.
• Terminals are therefore separated from the busbars, but not from each other.

FORM 3B TYPE 2

• As form 3 but: Busbar separations is achieved by metallic or non-metallic rigid barriers or partitions.
• Terminals are therefore separated from the busbars, but not from each other. 

 Advantages:

• The advantages include safety, ease of maintenance and reliability because it’s possible to isolate and perform maintenance on each starter without having to power down the whole switchboard.
• Serious faults within a starter are also more likely to be contained within a cubicle meaning adjacent starters are unaffected and can operate normally.

Electrical Safety:

• More reliable and safer than Form-2 due to separation between live parts (Busbar and Switchgear, Switchgear and Switchgear).

Cost:

• All these advantages come at a cost as a Form 3 board is significantly bigger and more expensive than a Form 1 or 2 board.

Application:

• Form 3 segregation is typically used for Big projects and larger operations that have a greater number of loads, motors and critical processes.
• They are utilised when safety, reliability and limited downtime are crucial.

(D) Form 4

 This is the highest form rating, as specified by AS/NZS / IEC 61439.1.

• Busbars are separated from functional units
• Functional units are separated from each other
• Terminations to functional units are separated from each other
• Busbar and Switchgear: Bus bars are separated from the Switchgear units,
• Busbar and Termination: Bus bars are separated from any incoming or outgoing terminations.
• Switchgear and Switchgear units: Switchgear units are separated from each other.
• Switchgear and Termination: Switchgear units are separated from any incoming or outgoing termination.
• Termination and Termination: Incoming and outgoing terminals are separated from each other
• This is further classified into 2 categories.

FORM 4A

• External cabling terminals are within the same cubicle as the corresponding functional unit.

FORM 4B

• The external cabling terminals are not in the same cubicle as the corresponding functional unit, and they are separated from the terminals of other functional units.

• The major difference between Forms 3 and 4 is the separation of the terminals of each functional unit the terminals of other units.

Advantages:

• The main advantage of this model is the ability to safely connect and disconnect outgoing cables while the rest of the switchboard remains in operation.
• In Large Panel access is required for inspection, to reset an auxiliary function. If the point of isolation and termination are each in their own individual box this can be deemed safer than if all the devices and connections are behind a single door

Electrical Safety:

• More reliable and safer than Form-4 due to separation between live parts (Busbar and Switchgear, Switchgear and Switchgear, Termination and Termination).
• Due to internal segregation is to limit the effects on adjacent circuits if something goes wrong. An external fault should cause a device to trip but this must not have any effect on any other circuits.

Cost:

• Form 4 board is significantly bigger and more expensive than a Form 3 board.

Applications:

• used in hospitals or for critical industrial processes.

SUMAMRY OF FORM OF SEPERATION OF PANEL

Forms of Separation for Panel (PART-1)

Introduction:

• Forms of segregation have great importance in electrical Panel designs.
• Form of segregation is the rule for provide separation from a one energizes function part to other energize function pant and access to a part of the assembly while other parts may remain energized. This can be achieved by using metallic or non-metallic physical barriers or insulation.
• The form of segregation provides protection against four objectives.

1. Protection against direct contact with live dangerous parts of adjacent functional units.
2. Protection against the entry of solid objects from one unit of an assembly to an adjacent unit.
3. Limitation of the effects of the spread of electric arcs.
4. Facilitation of panel maintenance operations.

Type of Separation:

• As specified by AS / NZS / IEC 61439, There are four main categories outlined by the standard for internally separating the switchgear units and busbars of a Panel are

1. Form 1 (No segregation between busbar, terminals and Switchgear units)
2. Form 2 (Separation between switchgear units and the busbar)
3. Form 3 (Separation are between switchgear units and the busbar and Separation between Switchgear unit to Switchgear Unit)
4. Form 4 (Segregation between busbar, terminals and Switchgear units)

• The complexity of the forms increases with the numbers.

(A) Form 1:

• A Form 1 Panel has no internal separation among busbar, switchgear and outgoing Cable Terminations.
• All functional units are installed in one central section to provide protection against contact with any internal live parts.
• Busbar and Switchgear: Bus bars are not separated from the Switchgear units,
• Busbar and Termination: Bus bars are not separated from any incoming or outgoing terminations.
• Switchgear and Switchgear units: Switchgear units are not separated from each other.
• Switchgear and Termination: Switchgear units are not separated from any incoming or outgoing termination.
• Termination and Termination: Incoming and outgoing terminals are not separated from each other

Advantage:

• Simple Design and Less Space Required.

Electrical Safety:

• Less due to No separation between live parts.
• This form construction is rarely used.

Cost:

• Less Cost

Application:

• For small, low power switchboards.

(B) Form 2

• Form 2a is the simplest for protecting against accidental contact with any internal live parts or components like the busbars, which are considered to be the most dangerous components.
• In FORM-2, Busbar is Separate from the Switchgear units but may or may not be separate from Cable terminal.
• Busbar and Switchgear: Bus bars are separated from the Switchgear units,
• Busbar and Termination: Bus bars may or may not separate from any incoming or outgoing terminations.
• Switchgear and Switchgear units: Switchgear units are not separated from each other.
• Switchgear and Termination: Switchgear units are not separated from any incoming or outgoing termination.
• Termination and Termination: Incoming and outgoing terminals are not separated from each other
• This is further classified into 2 categories.

FORM 2A

• Terminals are not separated from the busbars or each other.

FORM 2B

• Terminals are separated from the busbars

FORM 2B TYPE 1

• As form 2 but Busbar separation is achieved by insulated coverings, e.g. PVC sleeving, wrapping or coating.
• Terminals are the therefore separated from the busbars, but not from functional units or each other.

FORM 2B TYPE 2

• As from 2 but Busbar separation is achieved by metallic or non-metallic rigid barriers or partitions
• Terminals are therefore separated from the busbars, but not from functional units or each other

Advantages:

• There are several advantages to segregating functional units and busbars.
• This model allows circuit breakers to be reset when the switchboard is live because the operator is not exposed to a live busbar.

Electrical Safety:

• More than Form-1 due to separation between live parts (Busbar and Switchgear).

Cost:

• More Costly than Form-1

Application:

• For small, low power switchboards.