Consequences of occurrence of Faults

Consequences of occurrence of Faults

Faults are of two type

·                    Short circuit fault- current

·                    Open circuit fault- voltage

In terms of seriousness of consequences of a fault , short circuits are of far greater concern than open circuits, although some open circuits present some potential hazards to personnel Classification of short circuited Faults

• Three phase faults (with or without earth connection)

• Two phase faults (with or without earth connection)

• Single phase to earth faults

Classification of Open Circuit Faults

• Single Phase open Circuit

• Two phase open circuit

• Three phase open circuit

Consequences

•  Damage to the equipment due to abnormally large and unbalanced currents and low voltages produced by the short circuits

•   Explosions may occur in the equipments which have insulating oil, particularly during short circuits. This may result in fire and hazardous conditions to personnel and equipments

•    Individual generators with reduced voltage in a power station or a group of generators operating at low voltage may lead to loss of synchronism, subsequently resulting in islanding.

•  Risk of synchronous motors in large industrial premises falling out of step and tripping out. The general layout of a protection system may be viewed as given in the following figure