What are Protective Devices?

Electrical power systems are complex networks of electrical components that supply power to homes, businesses, and industries. These systems are designed to deliver electricity safely and reliably, but they are also subject to a variety of hazards that can cause damage to the system and threaten the safety of personnel. Protective devices are therefore a crucial part of any electrical power system, as they help to prevent damage and ensure safety in the event of abnormal conditions.

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Circuit Breakers

Circuit breakers are perhaps the most common type of protective device in electrical power systems. They are designed to interrupt the flow of electrical current when an abnormal condition is detected, such as an overcurrent or short circuit. Circuit breakers can be installed at various points in the system, including at the main distribution panel, sub-panels, and individual outlets. They typically consist of a switch mechanism that opens and closes the circuit, along with a protective mechanism that detects abnormal current flow and trips the switch.


Fuses are similar to circuit breakers in that they are designed to protect against overcurrent conditions. They consist of a thin wire that melts when the current exceeds a certain level, causing the circuit to break. Fuses are often used in conjunction with other protective devices, such as circuit breakers or surge arresters, to provide an additional layer of protection.

Surge Arresters

Surge arresters are used to protect the system against voltage surges caused by lightning strikes or other external sources. Voltage surges can cause significant damage to electrical equipment, so surge arresters are often installed at strategic points in the system to absorb the energy of the surge and prevent it from reaching the equipment. Surge arresters typically consist of a metal oxide varistor that absorbs the energy of the surge and dissipates it as heat.

Ground Fault Interrupters

Ground fault interrupters (GFI) are designed to protect against electric shock. They detect imbalances in current flow between the hot and neutral wires and trip the circuit if a ground fault is detected. GFIs are often used in areas where water is present, such as bathrooms, kitchens, and outdoor outlets.

Protective Relays

Protective relays are another type of protective device used in electrical power systems. They are designed to detect abnormal conditions in the system, such as overcurrent, under voltage, or overvoltage, and trip the circuit breakers or other protective devices as needed. Protective relays are often used in high-voltage systems, such as transmission lines and substations, where a fault can cause significant damage to the system.

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