Faults Close to Neutral in Wye winding of Transformers

[NickParker]

Why faults close to neutral in solidly grounded and resistance grounded systems behave differently? The fault currents in resistance grounded systems are linearly increasing depending on the fault location while the fault currents in solidly grounded systems are not linear.

[highlight #8AE234]Solidly grounded:[/highlight]

[highlight #8AE234]Resistance grounded:[/highlight]

 

[mparenteau]

Zero sequence impedance dominates initially...then as distance is increased, the positive sequence impedance dominates (for solidly grounded systems).

 

[cuky2000]

BACKGROUND: Transformer winding neutral can be solidly or impedance grounded with the purpose to reduce the ground-fault current.

1)Solidly grounded: the fault current in a start winding is limited only by the transformer winding reactance, which varies nonlinearly with the fault distance to the winding. For the vast majority of transformer winding the range is estimated as follow: [highlight #FCE94F]2 ≤ I_f/I_nominal ≤ 5.[/highlight]

2)Impedance grounded: the If is limited by the grounding resistor or reactor. The source impedance can be generally disregarded due to its relatively small magnitude compared to the magnitude of the neutral grounding Impedance. Therefore, the cable and the earth impedance associated with the fault location is not the dominant factor in this case.
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_{mparenteau, please help us to understand better your comment regarding the impact of the zero-sequence with the location of the fault.}

 

[cranky108]

Is your transformer producing C2H2 gas?