Earth Fault: Causes, Effect & Protection Devices
Before we get to discussing the causes and effects of an earth fault or possible solutions to protect against earth fault, it is important to first know what exactly is an earth fault. An Earth Fault is an Open Circuit fault where any live conductor or power-carrying cable breaks and gets into contact with the earth's surface. In other words, it is a situation where the current-carrying conductor comes directly in contact with the earth's surface.
Causes of Earth Fault
Earth Faults may occur due to a number of reasons but the most common one being the failure of the insulator. Insulators provide insulation between a live conductor and metallic towers that are already connected with the earth’s surface. When the insulation of the insulator fails, the current flows directly through the live conductor and metallic tower to the earth creating Earth fault.
Other reasons for Earth Faults could be overloaded or unusual loads on the line, due to which overhead transmission lines break and fall on the earth's surface. Or due to damaged insulation, damaged cable sheath, or damaged module back sheet.
Effect of Earth Fault
When an earth fault occurs, the electrical system gets short-circuited and the short-circuited current flows through the system to the earth’s surface. The fault current returns through the earth or any electrical equipment, interrupting the continuity of the supply and damage to the equipment. A large amount of current flowing to the earth causes the voltage to drop which can affect the other loads and may cause the burning of the phase or line. It may also cause an electric shock to the user, which might be fatal to one’s life.
Protection Devises to protect against Earth Fault
The most essential protection tip is to identify any earth leakage fault. Megger readings come in handy in such cases. One terminal of the megger is connected to the live conductor and the other terminal is connected to the earth. The zero reading indicates that the conductor is earthed, if not then these devices can be useful in providing protection to your equipment:
- Earth Fault Relay (EFR): It is a protection device that can detect any stray voltages on the metal enclosures of electrical equipment. In case a dangerous voltage is detected, it provides safety by interrupting the circuit. EFR provides protection to electrical equipment and is used in electrical installations with high earth impedance.
- Earth Leakage Circuit Breaker (ELCB): It is a voltage-sensing device that detects the leakage current and provides protection against electrical shock. It is used in electrical installation with high earth impedance. It is a special type of latching relay that is connected to the main power supply. When the fault current flows from the live wire to the earth wire within the installation, the coil of ELCB senses the voltage and switches off the power. Once when it tripped then it requires a manual reset process to work again normally.
Earth Fault can cause serious damage or even loss of life. Use protection relays to ensure the safety of your family and equipment!