Earth leakage protection in low voltage installations

We all should know that low voltage circuit breakers and fuses operate in the event of excess current arising from overload conditions and faults.

As the statistics say, the most common fault type in LV installations is an earth fault, but… We’ve often seen the cases that the current flowing due to earth faults is too low to operate the overcurrent protection devices.

It’s important to note that the overcurrent protective device will not operate in the event of somebody making direct contact with a live conductor.

Why? because the current which flows through the body to earth will be too low to operate the devices but will often be high enough to use fatal electric shocks.

So, we should use ELCB or earth leakage circuit breaker. 

ELCB (Earth Leakage Circuit Breaker):

The ELCB is used to protect the circuit from the electrical leakage.

When someone gets an electric shock, then this circuit breaker cuts off the power at the time of 0.1 sec for protecting the personal safety and avoiding the gear from the circuit against short circuit and overload.

ELCB is a security device used in electrical system with high Earth impedance to avoid shock.

It notices small stray voltages on the metal fields of electrical gear, and interrupt the circuit if an unsafe voltage is detected.

The main principle of Earth leakage protectors is to stop injury to humans and nature due to electric shock.

This circuit breaker is a specialized kind of latching relay that has structures incoming mains power connected through its switching contacts so that this circuit breaker disconnects the power supply in an unsafe condition.

The ELCB notices fault currents from live to the ground wire inside the installation it guards.

If enough voltage emerges across the sense coil in the circuit breaker, it will turn off the supply, and stay off until reset by hand.

A voltage-sensing earth leakage circuit breaker doesn’t detect fault currents from exist to any other ground body.

Characteristics of ELCB:

• This circuit breaker connects the phase, earth wire and neutral

• The working of this circuit breaker depends on current leakage

Why are over head power lines loose on electric poles and towers?

Overhead power lines appear loose on electric poles and towers due to a few key reasons:

1. Expansion and Contraction: Power lines are made of materials like aluminum or copper, which expand when heated by the current they carry or by the sun, and contract when they cool down. To accommodate this expansion and contraction without causing damage, the lines are strung with some slack.

2. Safety and Maintenance: Having some slack in the lines makes it easier for utility workers to perform maintenance or repairs without having to deal with taut lines, which could be dangerous or difficult to manage.

3. Weather Conditions: In cold weather, the lines contract, and if they were initially strung tightly, this could lead to breakage or other structural issues.

Loose lines can sway in the wind without snapping.

4. Structural Integrity: The poles and towers themselves need to support the weight of the wires. If the lines were too tight, it could put undue stress on these structures, potentially leading to their failure.

5. Sag and Tension: The design of power lines takes into account a certain amount of sag, which is necessary for maintaining consistent tension across different temperatures and loads. This sag helps in evenly distributing the mechanical stress.

6. Regulations and Standards: There are specific engineering standards and regulations that dictate how much slack or tension power lines should have, balancing safety, functionality, and longevity of the infrastructure.

This slack or looseness is a designed feature, not a flaw, ensuring the reliability and safety of the power distribution system under varying conditions.