Question

Given are the classifications of unsymmetrical faults that occur in transmission and distribution lines. Select the odd one from the following.
1. Double line fault (LL fault)
2. Double line to ground fault (LLG fault)
3. Triple line to ground fault (LLLG fault)
4. Single line to ground fault (LG fault)

Answer 1

Correct Answer - Option 3 : Triple line to ground fault (LLLG fault)

Concept:

Symmetrical faults:

• A symmetrical fault is a fault where all phases are affected so that the system remains balanced
• A three-phase fault is a symmetrical fault
• As symmetrical faults result in balanced conditions, they may be analyzed using per-phase analysis
• LLLG fault is symmetrical fault

 

Unsymmetrical Faults:

• Unsymmetrical faults are the faults that lead unequal currents with unequal phase shifts in a three-phase system
• The unsymmetrical fault occurs in a system due to the presence of an open circuit or short circuit of transmission or distribution line
• It can occur either by natural disturbances or by manual errors
• The natural disturbances are heavy wind speed, ice loading on the lines, lightning strikes and other natural disasters.
• LG, LL, LLG faults are asymmetrical faults.

 

Explanation:

From the given options LG, LL, LLG faults are asymmetrical faults whereas LLLG fault is symmetrical fault so LLLG will be odd one out.