Power system faults - Part2


Fault Effects :

The fault must be cleared as fast as possible. Many equipments may be destroyed if the fault is not cleared rapidly. The dangerous of the faults depends on the type of the fault, as example the three phase short circuit is the most dangerous fault because the short circuit current is maximum. Some of the effects of short circuit current are listed here under.
  1. Due to overheating and the mechanical forces developed byfaults, electrical equipments such as bus bars, generators,transformers will be damaged.
  2. Negative sequence current arises from unsymmetrical faults will lead to overheating.
  3. Voltage profiles may be reduced to unacceptable limits as a result of faults. A frequency drop may lead to instability
    Fault Types :
    • The fault can be classified due to the NATURE of the fault to
    1. Permanent
    2. Transient
    • Or due to PARTICIPATED PHASES as
    1. Phase-Earth
    2. Phase-Phase
    3. Phase-Phase-Earth
    4. Three-Phase or Three-Phase-Earth

    Symmetrical Components and Fault Types :

    Every type of fault contains different components, Table1 below shows some of these types:-