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Question

Which safety device is designed to detect cable electrical leakage and disconnect the circuit?

This question was previously asked in
RRB NTPC 2025 Graduate Level CBT 1 Question Paper (25-Mar-2026) (Shift 3)
The correct answer is

Earth leakage circuit breaker

Detecting leakage relies on the principle that, in a healthy circuit, the current leaving through the live conductor exactly returns through the neutral; any difference means current is escaping to earth.

An earth leakage circuit breaker continuously compares the live and neutral currents, and when it senses an imbalance, indicating current is leaking to earth through faulty insulation or a person, it trips and disconnects the circuit within milliseconds.

A fuse simply melts when the current exceeds a set value, so it reacts only to overload or short-circuit, not to a small leakage that never raises the total current.

A miniature circuit breaker likewise trips on overcurrent, whether overload or short-circuit, and cannot recognise the balanced-versus-unbalanced condition that signals leakage.

A relay is a general control and switching element operated by another signal; on its own it is not designed to sense earth leakage.

Only the device that measures the live-neutral imbalance responds specifically to leakage, making it the correct protective device here.

Hence, the answer is Earth leakage circuit breaker.

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