"A fault in an electrical circuit is defined as the defect in the electrical circuit because of which the current in the circuit is diverted from the intended path."For example suppose a circuit has two parallel paths, opening up of a path will divert the current to the other path and in the process it may damage the path or the conductor. Thus, faults can damage or disrupt the power system in many ways.
Causes:
In
a power system, the faults occur because of insulation failure which may be
because of a system over-voltage such as switching surges or lightning stroke.
Faults may also be due to a broken insulator or a conductor. Various other
reasons such as improper operating habits may also lead to a fault; for example,
loading a distribution transformer beyond its normal rated capacity.
Nearly one half of the faults occur on power lines which are widely branched, have greater length, operate under variable weather conditions and are more exposed to atmospheric disturbances.
Also read:
Nearly one half of the faults occur on power lines which are widely branched, have greater length, operate under variable weather conditions and are more exposed to atmospheric disturbances.
Also read:
Effects of fault
Faults
give rise to abnormal operating conditions. When a fault occurs at any point in
the power system large currents, large forces and or abnormal voltages are
developed. The excessive current because of the fault is determined by the
internal e.m.f.s of the machines in the network, their impedances, and the
impedance in the network between the machines and the fault.
Faults
currents, also called short circuit currents, are many times greater than
the normal currents. Large voltage stresses the insulation of the various
equipments, which are on the way, beyond their breakdown value causing the
failure.
Similarly large currents overheat the equipment or the element of the power system. Sometimes faults lower the system voltage below the permissible voltage limit causing unwanted and teasing interruption of various equipments and components. Faults can also cause a three-phase system to become unbalance.
Similarly large currents overheat the equipment or the element of the power system. Sometimes faults lower the system voltage below the permissible voltage limit causing unwanted and teasing interruption of various equipments and components. Faults can also cause a three-phase system to become unbalance.
Action to be performed during a fault
It
is necessary that the faults or the faulty section should be removed
immediately so that the normal operation of the rest of the system is
maintained. The protective relays employed in the power system or network
should immediately detect the faults or the faulty section without fail and send
trip signal for the operation of circuit breakers.
To
obtain proper setting of the protective relays and the interrupting capacities
of circuit breakers, the values of these fault currents and voltages should be
known with great accuracy. Short circuit studies and calculations provide
currents and voltages on a power system during fault conditions.
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