Single phase Voltage Transformer (VT) connected at one phase to ground.Single core cables installed over long distances in a flat or otherwise non-trefoil formation.Transmission lines that are not transposed which results in unequal impedances (both inductance and capacitance).These unbalances can arise due to different reasons such as: As mentioned above, the cause for neutral inversion or neutral shift is unbalanced impedances on different phases to ground. Hence there will be no potential difference between neutral point of supply transformer and neutral point of the ungrounded system. In a perfectly transposed line or a three-phase cable in perfect trefoil formation, each phase conductor will have the same capacitance to ground. Stated in other words, neutral inversion or neutral displacement can occur in a system with unbalanced impedance to neutral in system with balanced set of three phase voltage. When the line to ground impedances (usually capacitive impedance) is not equal between the phases, the position of neutral inside the voltage triangle could change or in the worst case fall outside the triangle. The ungrounded system could be delta or wye with neutral ungrounded. Delta System showing capacitively coupled neutral
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