A short circuit current can be very large. If unusually high currents exceed the capability of protective devices (fuses, circuit breakers, etc.) it can result in large, rapid releases of energy in the form of heat, intense magnetic fields, and even potentially as explosions known as an arc blast. The heat can damage or destroy wiring insulation and electrical components. An arc blast produces a shock wave that may carry vaporized or molten metal and can be fatal to unprotected people who are close by.
A Short Circuit Analysis will ensure that personnel and equipment are protected by establishing proper interrupting rating of protective devices (circuit breaker and fuses). If an electrical fault exceeds the interrupting rating of the protective device it needs to be replaced with one having adequate capacity, otherwise the consequences can be devastating. It can be a serious threat to human life and is capable of causing injury, extensive equipment damage, and costly downtime.
Relay coordination study and analysis is performed to make sure that safety operation of the system is functioning correctly and to avoid the nuisance tripping, as protection is a major concern in any industry, and they rely on protective devices for the same. The reason for nuisance tripping is modification of protective devices and their settings at the time of upkeep without performing suitable study and analysis
The aim of a coordination study is to determine the characteristics, rating, and settings of overcurrent protective devices which will ensure that minimum unfaulty load is interrupted when protective devices isolate a fault or overload anywhere in the system.
An electric arc is a luminous bridge formed in a gap between two electrodes. An Arc Flash occurs during a fault, or short circuit condition, which passes through this arc gap. The Arc Flash can be initiated through accidental contact, equipment which is underrated for the available short circuit current, contamination or tracking over insulated surfaces, deterioration or corrosion of equipment and, or parts, as well as other causes. An Arc Flash event can expel large amounts of deadly energy. The arc causes an ionization of the air, and arc flash temperatures can reach as high as 35,000 degrees Fahrenheit. This is hotter than the surface of the sun.
The result of the arc flash analysis will categorize the hazard at specific equipment based on the incident energy, as well as identify the Arc Flash Protection Boundary (this is the closest approach allowed before PPE must be worn). Inside the Arc Flash Protection Boundary, a worker must be wearing the proper clothing, or Personal Protective Equipment (PPE). The main objective of the PPE is to limit the burns to the body resulting from an arc flash event, to a survivable level.
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