Friday 8 September 2017

UNSYMMETRICAL FAULT CALCULATIONS – PART – 11

DELTA-CONNECTED WINDING
In delta connected winding no zero sequence currents flow in the lines because there is no return path for these currents.
STAR-CONNECTED WITHOUT NEUTRAL WINDING
In a three-phase, a three-wire system without a neutral network, the zero sequence line currents are zero.
STAR-CONNECTED WITH NEUTRAL GROUNDED
Three phase with neutral return zero sequence currents can flow both in the phase and windings as well as in the lines.
If the neutral is solidly grounded Zn = 0.
Total zero sequence impedance from point Ground to P is equal to the Total zero sequence impedance from Neutral to P.
The voltage to neutral or voltage to ground is the same in the case of positive and negative sequence systems.
For solidly grounded system zero sequence impedance is infinity.

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