What is difference between symmetrical and unsymmetrical bending?
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1)Symmetrical fault increases the symmetrical current where as unsym increases the
2) Symmetrical & Unsymmetrical Faults
Normally, a power system operates under balanced
Faults that occurs in transmission lines are broadly classified as
Symmetrical faults
Unsymmetrical faults
Symmetrical faults
In such types of faults, all the phases are short-circuited to each other and often to earth. Such fault is balanced in the sense that the systems remain symmetrical, or we can say the lines displaced by an equal angle (i.e. 120° in three phase line). It is the most severe type of fault involving largest current, but it occurs rarely. For this reason balanced short- circuit calculation is performed to determine these large currents.2
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 unsymmetrical shunt fault is an unbalanced in the line impedances. Shunt fault in the three phase system can be classified as;
Single line-to-ground fault (LG).
Line-to-line fault (LL).
Double Line-to-ground fault (LLG).
Three-phase short circuit fault (LLL).
Three-phase-to-ground fault (LLLG).
In single line-to-ground fault, one conductor comes in contact with the ground or the neutral conductor. A line-to-line fault occurs when two conductors are short circuited. A double line-to-ground fault occurs when two conductors fall on the ground or come in contact with the neutral conductor. LG, LL, and LLG are unsymmetrical fault while LLL and LLLG are the symmetrical faults. For this reason, balanced short-circuit calculation is performed to determine these large currents.2
2) Symmetrical & Unsymmetrical Faults
Normally, a power system operates under balanced
Faults that occurs in transmission lines are broadly classified as
Symmetrical faults
Unsymmetrical faults
Symmetrical faults
In such types of faults, all the phases are short-circuited to each other and often to earth. Such fault is balanced in the sense that the systems remain symmetrical, or we can say the lines displaced by an equal angle (i.e. 120° in three phase line). It is the most severe type of fault involving largest current, but it occurs rarely. For this reason balanced short- circuit calculation is performed to determine these large currents.2
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 unsymmetrical shunt fault is an unbalanced in the line impedances. Shunt fault in the three phase system can be classified as;
Single line-to-ground fault (LG).
Line-to-line fault (LL).
Double Line-to-ground fault (LLG).
Three-phase short circuit fault (LLL).
Three-phase-to-ground fault (LLLG).
In single line-to-ground fault, one conductor comes in contact with the ground or the neutral conductor. A line-to-line fault occurs when two conductors are short circuited. A double line-to-ground fault occurs when two conductors fall on the ground or come in contact with the neutral conductor. LG, LL, and LLG are unsymmetrical fault while LLL and LLLG are the symmetrical faults. For this reason, balanced short-circuit calculation is performed to determine these large currents.2
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