The origins of short circuit in network are accidental disturbance caused by undesired contact between the conductors, dielectric breakdown of insulation due to overvoltage's, breaking of cable, falling of trees, contacts with animal or human errors. The effect depend on the architecture of the power system. Short Circuit Analysis is performed to determine the currents that flow in a power system under fault conditions. The purpose of studying a network configuration subject to a short circuit is to :
1. Identification of risk situation that can possibly causes destruction of devices due to electrodynamic forces,excessive temperature rise and overvoltage.
2. Accessing the risk and assist in making basic design decision to limit the effect of fault concerning system earthing design, suitable sizing of devices.
3. If the short circuit capacity of the system exceeds the capacity of the protective device, a dangerous situation exists. Since growth of a power system often results in increased available short-circuit current, the momentary and interrupting rating of new and existing equipment on the system must be checked to ensure the equipment can withstand the short-circuit energy. Fault contributions for utility sources, motors and generators are taken into consideration. The results of a study are also used to selectively coordinate electrical protective devices.Arc flash analyses is important to know the actual level of danger. It is helpful to decide proper personal protective equipment (PPE) required for electrical equipment operator or employee.
Electrical systems are dynamic in nature and change over time due to internal modification, adding new equipment and changing of the load characteristics.It can affect the level of arc flash energy. A study is normally recommended for every time the system changes.
Following parameter should be validated during study :