Impact of Untransposed Power Lines

Josifs Survilo

Abstract


Unbalanced power lines (the conductors of which are not arranged in the vertices of equilateral triangle) without overhead grounding wire (OGW) besides Fortesque impedances Z0 and Z1 = Z2 have mutual impedances Z01, Z10, Z02, Z20, Z12, Z21. At the end of the line negative sequence and in less degree zero sequence of voltage take place having increased with the load increasing. Flat phase arrangement 110 kV line with X/R = 4, loaded by active load with resistance tenfold of phase conductor active resistance generates 2.54 % of negative sequence and 0.79% of zero sequence. Inductive load generates less and capacitive–stillmoreasymmetry. Straycapacitancesandcorona losses do not have any influence. Under asymmetric short circuits impact on relay protection depends on location of special phase: it is located laterally or in the middle of the flat arrangement. Digital relay protection can easier cope with the phase unbalance effect when the line is untransposed. Balanced voltage at the end of untransposed unbalanced power line can be obtained loading the line with unbalanced load. 


Keywords:
current sequence of three-phase system, flat phase arrangement, mutual impedances, self impedances, untransposed power line

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References


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DOI: 10.7250/pee.2014.005

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