## When to use SP, DP, TP, 4P, SP+N, TP+N Circuit Breakers

1. SP or 1P– Single Pole
2. SP + N – Single Pole and Neutral
3. DP or 2P – Double pole
4. TP or 3P – Triple Pole
5. TP + N – Triple Pole and Neutral
6. 4P – Four Pole

1.     Single Pole (SP):

• In a Single Pole CB, switching & protection happens over only one phase.
• AC Voltage in SA is 220/230V between Phase and Neutral.
• Application: Single Phase Supply, CB is used to break the Phase only.
• Used for Lighting circuits, plug points, etc..

2.     Single Pole + Neutral (SP + N):[Single Pole + Neutral ABB circuit breaker: S201-C NA]

• In a Single Pole + Neutral MCB, the switching  happens over the Phase and Neutral. However, no protection is incorporated over the Neutral Phase.
• AC Voltage in SA is 220/230V between Phase and Neutral.
• Application: Single Phase Supply, CB is used to break the Phase and Neutral.
• Used for AC, Heaters, Dryers, etc..

2.     Double Pole (DP):

• In a Two Pole or Double Pole MCB, the switching & protection happens over phase-phase or the phase-neutral.
• AC Voltage in SA is 400V between Phases.
• Application: Single Phase Supply, CB is used to break the Phase and Neutral.
• Used for AC, Heaters, Dryers, etc..

3.     Triple Pole (TP):

• In a Three Phase or Triple Pole CB, switching & protection happens over all three phases. The neutral is not switched or protected.
• As in the image above, the phase indications are often represented as Red-White-Blue.
• AC Voltage in SA is 400V between Phases.
• Application: Used in a system with a three Phase Supply.
• Used for machinery, motors, welders, etc..

4.     Triple Pole Plus Neutral (3P+N):

• In a 3P+N CB, Neutral phase switching takes place within the CB as a separate pole. However, no protection is incorporated.
• TPN for Y (or star). The connection between ground and neutral is in many countries not allowed. Therefore the N is also switched.
• AC Voltage in SA is 400V between Phases.
• Application: Three Phase Supply with Neutral.

5.     Four Pole (4P):

• In a 4P CB, Neutral phase switching takes place within the CB and protection is incorporated.
• In 4-Pole MCCBs the neutral pole is also having protective release as in the phase wires.
• AC Voltage in SA is 400V between Phases.
• Application: Three Phase Supply with Neutral.
• Used in application where the neutral is to be isolated from the earth in case of an earth fault, photo-voltaic installation, UPS, Generator suppler etc…

## Difference between TP+N and 4P

• For TP+N, protection applies to the current that flows through only 3 poles (Three Phase) only; there is no protection for the current flow through the neutral pole. Neutral is just an isolating pole.
• For the 4 pole breakers, protection applies to current flow through all poles. However when the breaker trips or is manually opened, all poles are disconnected.

## Where to Use TP, TPN and 4P in a Distribution Panel:

• An MCB is used for protection of the system if fed from a transformer. If the board is fed from a Minisub or is a sub-distribution board, the main incomer can be an Isolator, as the protection takes place up stream.
• TP MCB: It is the most common type of breaker used in ordinary three phase supply.
• TP+N MCB: It is generally used where there are dual incomers to the panel (utility source and emergency generator source).
• 4P MCB: It is used where there is the possibility of high neutral current (due to unbalance loads and /or 3rd and multiple of 3rd harmonics current etc) and Neutral / Earth Protection is provided on Neutral.
• Normally in a 3 phase + neutral system, it is common practice to use a 3 pole CB while the Neutral is connected to a common Neutral Link.  However, if the application of a 3pole will affect the operation of a protective relay then a 4 pole CB is used.