A fault occurs when two
or more conductors come in contact with each other. these faults may be due
to Sudden failure of equipment
- Accidental damage
- Short Circuit
- Insulation failure
The faults in 3-Phase
Power System are classified into two main categories
- Symmetrical Faults
- Unsymmetrical fault
Symmetrical Faults
The fault which gives rise to symmetrical fault currents (i.e.
equal fault currents with 120 displacement) is called a Symmetrical fault. The
most common example of symmetrical fault is when all three conductors of three
phase line come together simultaneously into a short circuit condition, more
clear picture is shown in figure.
Unsymmetrical faults
Those faults which give rise to unsymmetrical currents (i.e.
unequal line currents with unequal displacement) are called unsymmetrical
faults. The unsymmetrical faults may take one of the following forms:
a) Single
line to ground fault b) Line-to-Line
fault c) Double
line-to-ground fault
The majority of faults on power system are of unsymmetrical
nature; the mist common is short circuit form one line to ground fault. more
clear picture is shown in figure.
