Question 4 ( 5 marks) (a) Explain the function of the 30 mA RCCB commonly found in the Distribution Boards (DBs) in households. (b) State ONE function of the voltmeter installed at the outgoing circuit of a consumer main distribution board. (c) Explain the difference between a Live-Earth short circuit and an earth leakage curren

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### (a) Function of the 30 mA RCCB in Distribution Boards

The 30 mA Residual Current Circuit Breaker (RCCB) is a safety device commonly found in household distribution boards. Its primary function is to detect and prevent electric shock hazards and electrical fires caused by earth faults. The RCCB continuously monitors the balance of electrical current flowing through the live (phase) and neutral wires. If it detects an imbalance of 30 mA or more, which indicates that some current is leaking to the earth (potentially through a person or faulty appliance), it quickly disconnects the circuit. This rapid disconnection helps to protect individuals from electric shock and reduces the risk of electrical fires caused by faulty wiring or appliances.

### (b) Function of the Voltmeter at the Outgoing Circuit of a Consumer Main Distribution Board

The voltmeter installed at the outgoing circuit of a consumer main distribution board serves the function of monitoring the voltage level supplied to the various circuits in the household. By providing real-time voltage readings, it allows users or electricians to ensure that the voltage is within the acceptable range for safe operation of electrical appliances. This monitoring can help identify issues such as voltage drops, overvoltage conditions, or other electrical problems that may affect the performance and safety of the electrical system.

### (c) Difference Between a Live-Earth Short Circuit and an Earth Leakage Current

A **Live-Earth short circuit** occurs when the live (phase) wire comes into direct contact with the earth (ground) wire or any conductive surface that is grounded. This creates a low-resistance path for the current to flow directly to the ground, leading to a sudden surge of current that can trip circuit breakers or blow fuses. This situation poses a significant risk of electric shock and can cause damage to electrical equipment.

On the other hand, **earth leakage current** refers to a small amount of current that unintentionally flows from the live conductor to the earth due to insulation failure, moisture, or other faults in the electrical system. This current does not create a direct short circuit but indicates a potential hazard, as it can lead to electric shock if a person comes into contact with the faulty appliance or wiring. Earth leakage currents are typically detected by devices like RCCBs, which can disconnect the circuit if the leakage exceeds a certain threshold (e.g., 30 mA).

In summary, a Live-Earth short circuit is a direct and dangerous fault that results in a high current flow, while earth leakage current is a smaller, potentially hazardous current that indicates insulation failure or other issues.
(a) The 30 mA RCCB in distribution boards detects and prevents electric shock hazards and fires due to earth faults by monitoring current balance and disconnecting the circuit if an imbalance is detected. (b) The voltmeter at the outgoing circuit of a distribution board monitors voltage levels to ensure safe operation of appliances and to identify electrical issues. (c) A Live-Earth short circuit is a direct contact between live and earth wires causing high current flow, while earth leakage current is a small current indicating potential hazards due to insulation failure.

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