Causes of faults in power systems: 1) Over voltages due to direct lightning strokes. 2) Over voltages due to switching surges. 3) Falling of external conducting objects, tree branches etc. on conducting lines. 4) Accumulation of dust, dirt etc. on exposed components as lines, insulators etc. 5) Perching of birds on lines, insulators or other components. 6) Ill-maintained sections of the power systems. 7) Heavy unbalanced loading on three phase lines even for short times. 8) Prolonged unbalanced loading conditions leading to overheating (due to harmonics). 9) Failure of joints. 10) Open circuited line or broken conductors. 11) Mechanical damage to components of the power systems. 12) Unusually severe atmospheric conditions as storm, rains, too high humidity, 13) Defective/improper selection of components used and faulty design of the power system sections. 14) Failure of insulation of components and equipment parts. 15) Accidents. 16) Over temperature. 17) Excessive internal and external stresses.
Effects of faults: 1) Heavy short circuits lead to damage to equipment mechanically and electrically. 2) Arcing during faults leads to fire hazards. 3) Heavy drop in the supply voltage to loads leading to their mal-operation. 4) Overheated machines due to unbalanced supply voltages. 5) Loss of revenue to supply agency owing to stoppage of supply. 6) Loss of system stability due to generators losing synchronism. 7) Distress load shedding.