Earth Leakage Protection is an electrical safety method designed to disconnect power immediately when current leaks from a live conductor to earth (ground). This protects people from electric shock and buildings from fire caused by insulation failure or faulty equipment.

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What is “earth leakage”?

Earth leakage occurs when some of the current leaves the intended circuit path(live → load → neutral) and instead flows to earth—often:

• Through damaged insulation
• Through metal enclosures
• Through a human body touching a live part

Even small leakage currents can be fatal to humans, far below the level needed to trip an MCB.

How earth leakage protection works (basic principle)

Modern earth leakage devices compare:

• Current is going out on Live
• Current returning to Neutral

Under normal conditions, these currents are equal.
If there’s a difference (called residual current), the device trips and cuts power within milliseconds.

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Main types of Earth Leakage Protection devices

1. RCCB / RCD (most common today)

RCCB (Residual Current Circuit Breaker) or RCD (Residual Current Device):

• Detects imbalance between live and neutral currents
• Trips when leakage exceeds a set value
• Does NOT provide overload or short‑circuit protection
• Must be used together with an MCB

Typical sensitivity:

• 30 mA – personal shock protection (homes)
• 100–300 mA – fire protection (industrial)

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2. RCBO (combined protection)

RCBO = RCD + MCB in one device

• Earth leakage protection
• Overload protection
• Short‑circuit protection

Used when individual circuit protection is required (e.g. socket circuits).

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3. ELCB (older technology)

Older voltage‑operated ELCBs:

• Detect voltage rise on the earth conductor
• Require good earthing
• Cannot detect leakage that doesn’t pass through the earth

They are largely obsolete and have been replaced by RCD/RCCB.

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Why MCB alone is NOT enough

An MCB detects current magnitude, not leakage.

Example:

• A person touching a live conductor may draw 30–50 mA
• This is lethal but far below a 10A–20A MCB trip level
• Only an earth leakage device will trip

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Earth leakage protection in Singapore (important)

According to Singapore authorities:

• Homes must have an RCCB/ELCB installed
• Homeowners without one may face fines up to SGD 5,000
• The device is usually located at the distribution board and has a “TEST” button

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Typical leakage ratings and use

Leakage rating	Purpose
10 mA	Special locations, very sensitive
30 mA	Personal protection (standard for homes)
100 mA	Equipment/fire protection
300 mA	Industrial fire protection