Phase Magnitudes
Residual (Neutral)
For balanced 3-phase systems, the residual should be zero. Any imbalance will result in a non-zero neutral current/voltage.
Residual current is what an earth-fault element measures. Setting those elements against standing unbalance and fault levels is part of a protection study. Protection studies →
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Vector Diagram
3-Phase Vector Relationships
Phase Displacement: In a balanced 3-phase system, phases are displaced by 120° (2π/3 radians).
Vector Addition: The resultant is found by adding vectors tip-to-tail.
Residual Current: IN = IL1 + IL2 + IL3
Balanced System: When all phases are equal, IN = 0
Frequently Asked Questions
How is the residual calculated?
The three phase quantities are added as vectors 120 degrees apart: IN = IL1 + IL2 + IL3. The tool draws them tip to tail, and the residual is the vector that closes the triangle back to the origin.
Why is the residual zero on a balanced system?
Three equal magnitudes 120 degrees apart cancel exactly. Any difference in magnitude leaves a non-zero neutral current or voltage, which is what the tool shows.
Does the tool handle phase angle unbalance?
No. It takes magnitudes only and keeps the three phases 120 degrees apart, so it shows the residual from magnitude unbalance alone.