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Option 1 : Symmetrical fault
Symmetrical Faults:
- In such types of faults, all the phases are short-circuited to each other and often to earth as shown in the figure.
- Such fault is balanced in the sense that the systems remain symmetrical, or we can say the lines are displaced by an equal angle (i.e. 120° in a three-phase line).
- It is the most severe type of fault involving the largest current, but it occurs rarely. For this reason, a balanced short-circuit calculation is performed to determine these large currents.[ alt="F6 Madhuri Engineering 30.06.2022 D6" src="//storage.googleapis.com/tb-img/production/22/06/F6_Madhuri_Engineering_30.06.2022_D6.png" style=" width: 267px; height: 145px;">
Unsymmetrical faults:
Unsymmetrical faults involve only one or two phases. In unsymmetrical faults the three-phase lines become unbalanced. Such types of faults occur between line-to-ground or between lines. An unsymmetrical series fault is between phases or between phase-to-ground, whereas an unsymmetrical shunt fault is unbalanced in the line impedances.
- Single line-to-ground fault (LG).
[ alt="F2 Madhuri Engineering 04.07.2022 D24" src="//storage.googleapis.com/tb-img/production/22/07/F2_Madhuri_Engineering_04.07.2022_D24.png" style="height: 217px; width: 358px;"> - Line-to-line fault (LL)
[ alt="F2 Madhuri Engineering 04.07.2022 D25" src="//storage.googleapis.com/tb-img/production/22/07/F2_Madhuri_Engineering_04.07.2022_D25.png" style="height: 200px; width: 346px;"> - Double Line-to-ground fault (LLG)
[ alt="F2 Madhuri Engineering 04.07.2022 D26" src="//storage.googleapis.com/tb-img/production/22/07/F2_Madhuri_Engineering_04.07.2022_D26.png" style="width: 264px; height: 173px;">
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