If an electrical system does not have a fault protection system and proper grounding in place, electrical faults pose a substantial risk of injury. An electrical fault occurs when there is an abnormal electrical current, such as an over current, under voltage, unbalance of the phases, reversed power, and high voltage surge. A fault can be very dangerous and destructive causing fire, explosion, or electrical shock to persons nearby. These dangers to people are in addition to the damage faults may cause to the electrical system itself.
Electrical faults may be caused over time by a deterioration of the insulation protecting the electrical equipment. Additionally, electrical faults may also be caused by a sudden storm, vehicle collision, or aircraft collision. Finally, electrical faults can occur during switching surges when there is a sudden interruption in the circuit.
A protection device can eliminate the dangers that are associated with electrical faults. Fault protection systems detect fault conditions and remove the voltage on conductors, if there is an unwanted connection. Common protection devices include a circuit breaker or a fuse.
A circuit breaker interrupts the current flow after a fault is detected. This type of protection system is the most common. One specific type of circuit breaker is the automatic circuit recloser. Automatic circuit reclosers are high-voltage circuit breakers and they are used for overhead powerlines. Automatic circuit reclosers are equipped with a mechanism which automatically restores service after a momentary outage by closing the circuit that was opened due to a fault. They are favored by electric power companies, because they help reduce permanent faults by allowing the service to be restored before the fuse is blown.
A fuse protects against the dangers of faults by opening the circuit whenever a fault exists in the system. A fuse consists of a thin copper wire enclosed in a glass or a casing with two metallic contacts. The high fault current rises the temperature of the wire causing it to melt and thereby interrupting the current. A fuse may require the manual replacement of wire each time it blows.
In addition to fault protection systems, it is important that electric power companies have a proper grounding system. A grounding system provides an alternative route for the electrical current to follow back to the ground, if there has been an electrical fault. If there is a proper grounding system in place, a ground fault will result in a simple shutdown instead of a fire, burning, or electrical shock to nearby workers. The National Electrical Code provides requirements for grounding systems that must be followed by electric power companies.
The dangers of electrical faults are very serious. It is critical that electric power companies maintain fault protection systems and proper grounding to protect against electrical shock hazards.