ABSTRACT

A short-circuit fault takes place when two or more conductors come in contact with each other when normally they operate with a potential difference between them. The contact may be a physical metallic one, or it may occur through an arc. In the metal-to-metal contact case, the voltage between the two parts is reduced to zero. The voltage through an arc will be of a very small value. Short-circuit faults in three-phase systems are classified as: balanced or symmetrical three-phase faults; single line-to-ground faults; line-to-line faults; double line-to-ground faults. Short-circuit and protection studies are an essential tool for the electric energy systems engineer. The task is to calculate the fault conditions and to provide protective equipment designed to isolate the faulted zone from the remainder of the system in the appropriate time. Balanced three-phase generators and motors have only positive sequence-generated voltages. The negative sequence network model will not contain voltage sources associated with rotating machinery.