Working principles of Earth Leakage Circuit Breaker

Earth leakage circuit breaker (ELCB) is an electrical safety device that cuts power after detecting currents leaking to earth from an installation. In the absence of this vital device, there may be a high chance of electrical shock if a human or animal touches the installation. ELCB cuts the power by opening the associated circuit breaker. The two types of ELCB are voltage ELCB and current ELCB.  

History of Earth Leakage Circuit Breaker

The voltage earth leakage circuit breaker was introduced 60 years ago, while the current ELCB has been around for about 40 years. In the early years, the two devices were referred to as ELCB as the name was easy to recall, leading to confusion in the electrical sector.

Given that the two devices function differently, it meant installing the wrong device could not yield the expected results. The level of protection provided was less than expected when the wrong device was used.

To address this problem, IEC introduced the term Residual Current Device (RCD) to refer to current ELCB. Therefore, ELCB refers to voltage ELCBs.

Principles of Voltage Earth Leakage Circuit Breaker

The working principle of voltage earth leakage circuit breaker is quite simple. One terminal of the relay coil must be attached to the metal body of the equipment that you want to protect from earth leakage. The other terminal should be connected to the earth directly.

In case of insulation failure or when the live phase wire touches the metal, a voltage difference occurs between the terminals of the coil connected to the equipment body and earth. Consequently, there's the production of a current that flows the relay coil.

When the voltage difference exceeds a specific limit, the circuit breaker detaches the power. According to its typicality, this device detects and protects only the equipment it's connected to. In case of insulation leakage in other parts of the system, the device won't detect it.

Benefits of Voltage Operated ELCB

1.    They're less sensitive to fault conditions and hence have fewer nuisance trips.

2.    While current and voltage on the earth line is generally the fault current from a live wire, it's not always the case. There are circumstances in which an ELCB can cause an annoyance trip.

3.    When the installation of an electrical system has two earth connections, a nearby high current lightning will root a voltage gradient in the soil, presenting the ELCB sense coil with sufficient voltage to cause it to trip.

Weaknesses of Voltage Operated ELCB

1.    They do not detect faults that don't permit current through the CPC to the earth rod.

2.    Electrically leaky appliances like some water heaters might cause the ELCB to trip.

Current ELCB

Residual-current devices (RCD) refer to current-operated ELCBs, and they're used for protection against earth leakage. The supply and return circuit conductors run through a sensing coil. When the currents don't balance, the electrical device trips the contact.

When there's a fault, a small current will run into the earth too, and the magnetic flux will no longer be balanced. This will detect the outflow and direct signal to the tripping system.

Why Should You Consult a Licensed Electrician?

An electrical installation expert will take you through the entire process of installing an earth leakage circuit breaker. When you want to re-select the power cable, an expert will help you choose a high-quality product and do the necessary repairs.

Due to their experience, professional electricians know the best brands in manufacturing electric appliances. When you rely on their services, there are high chances that you'll get original products and quality service.