MCCB – Moulded Case Circuit Breaker
· Protection against Overload (Thermal Tripping) and Short Circuit (Magnetic Tripping)
- Thermal tripping (overload) normally can set at 50%, 75%, 100%
- Magnetic tripping (short circuit) can set for Icu, Ics
· Standard Rating: 16A, 20A, 25A, 32A, 40A, 50A, 63A, 80A, 100A, 125A, 160A, 200A, 250A, 320A, 400A, 500A, 630A, 800A, 1000A, 1250A, 1600A
· Pole: 1, 2, SPN, 3, 4, TPN
· Category: A (no short circuit trip delay), B (in built time delay maybe adjustable): 125A to 1600A
· Breaking Capacity:
- Icu: Ultimate short circuit capacity
- Ics: Service short circuit breaking capacity
- Icw: Short time withstand current (0.05 – 0.1 – 0.25 – 0.5 – 1s)
· Energy liminating class: 1 (no limit), 2 (370 kA²s), 3 (110 kA²s)
· Example write-up in the drawing:
MCB – Miniature Circuit Breaker
· MCBs provide overcurrent and short-circuit protection only and are unable to detect residual current (earth leakage current) unless it is large enough to be classed as an overload or short circuit.
· IEC 60898 (domestic/unsupervised) & IEC 609947-2 (industry/supervised)
· MCBs provide overcurrent and short-circuit protection only and are unable to detect residual current (earth leakage current) unless it is large enough to be classed as an overload or short circuit.
· IEC 60898 (domestic/unsupervised) & IEC 609947-2 (industry/supervised)
· Standard Rating: 0.5A, 1A, 2A, 3A, 4A, 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A, 80A, 90A, 100A, 125A
· Breaking Capacity: 3 – 25kA
· Pole: 1, 2, 3, 4
· Magnetic Trip Type: B (socket), C (lighting, fan), D (Aircond, motor, sodium lighting)
· Type B MCBs react quickly to overloads, and are built to trip when the current passing through them is between 3 and 4.5 times the normal full load current. They are suitable for protecting incandescent lighting and socket-outlet circuits in domestic and commercial environments, where there is little risk of current surges of a magnitude that could cause the MCB to trip.
· Type B MCBs react quickly to overloads, and are built to trip when the current passing through them is between 3 and 4.5 times the normal full load current. They are suitable for protecting incandescent lighting and socket-outlet circuits in domestic and commercial environments, where there is little risk of current surges of a magnitude that could cause the MCB to trip.
· Type C
MCBs react more slowly, and are recommended
for applications involving inductive loads with high inrush currents, such as
fluorescent lighting installations. Type C MCBs are built to trip at between 5
and 10 times the normal full load current.
· Type D
MCBs are slower still, and are set to trip at
between 10 and 20 times normal full load current. They are recommended only
for circuits with very high inrush currents, such as those feeding transformers and welding machines.
Type K MCBs
are designed to trip at between 8 and 12 times normal full
load current, placing them between the traditional
Type C
and Type D breakers. In most cases,
they allow improved cable protection to be provided in circuits that include
motors, capacitors and transformers, where it would previously have been
necessary to use Type D devices. This enhanced protection is achieved without
increasing the risk of nuisance tripping.
· Energy liminating class: 1 (no limit), 2 (370 kA²s), 3 (110 kA²s)
· Example write-up in the drawing:
RCD – Residual Current Device
· Intended
principally to minimise the risk of injury from electric shock, RCCBs provide protection against residual (earth leakage) currents only, and are not sensitive to overloads or short circuits. For this reason,
they must never be used as the sole protection device for a circuit.
Circuits with RCCB protection must
always include separate protection against overloads and short circuits. This is most often an MCB, but it
could, for example, be a fuse.
· Like MCBs,
RCCBs are available in various different types that are designated by letters.
This is a potential source of confusion so it’s worth remembering that a Type B
MCB, for example, is not related to a Type B RCCB.
· RCCB (Residual Current Circuit Breaker)
· RCBO (Residual Current Breaker with Overcurrent)
· Pole: 2, 4
· Tripping current: 6mA, 10mA, 100mA, 300mA, 500mA
· Standard Rating: 10A, 13A, 16A, 20A, 25A, 32A, 40A, 63A, 80A, 100A, 125A
· Type: G, S (time tripping can be delay)
· Class: AC, A (recommended), B (3ph inverter), F (1ph inveter)
· Example Write-up in the drawing:
The earth fault protection system is designed as below:
The earth fault protection system is designed as below:
· Each incoming power for DB and SSB up to 100A is protected by RCCB (Residual Current Circuit Breaker).
· Each incoming power for DB and SSB within 125A and 300A is protected by Earth Leakage Relay (ELR),
· Each incoming power for DB and SSB above 400A and above is protected by Earth Fault (EF) Protection Relay.
· As additional protection by client, all the outgoing circuit from the MSB and ESSB must be protected by the Earth Fault (EF) Protection Relay.
· Refer to Energy Commission (ST), the sensitivity for RCD shall be as following:-
- All installation (1 phase & 3 phase): 100mA (0.1A)
- Final switch socket: 30mA (0.03A)
- Wet area, i.e. toilet & wet kitchen: 10mA (0.01A)
