Ratio Z2 / Z0
Ratio Z2 / Z1

Inspector

Hover over the chart to see fault details.

Legend

Line-to-Line (Green)
Double Line-to-Ground (Yellow)
Single Line-to-Ground (White)
3-Phase (Gray)

Z1 is normalized to 1.0 p.u.
Z2 derived from X-axis ratio.
Z0 derived from Y-axis ratio.

Fault Current Calculation Formulas

3-Phase Fault
|I3P| = V / Z1
Line-to-Line (L-L)
|ILL| = (√3 · V) / (Z1 + Z2)
Single Line-to-Ground (SLG)
|ISLG| = (3 · V) / (Z1 + Z2 + Z0)
Double Line-to-Ground (DLG) (Max Phase Current)
|IDLG| = (V·√3 · √(Z0²+Z0Z2+Z2²)) / (Z1Z2 + Z1Z0 + Z2Z0)
Note: Calculations assume V = 1.0 p.u. and Z1 = 1.0 p.u. (normalized). Z2 and Z0 are derived dynamically from the chart's axis ratios.

Real-World Scenarios by Zone

Generator Terminals (Line-to-Line)

Why: Close to synchronous generators, the Negative Sequence Reactance (X2) is often lower than the effective Positive Sequence Reactance (X1), causing this ratio to drop below 0.732.

Grounded Transformer Secondary (SLG)

Why: Close to a solidly grounded Delta-Wye transformer. The Zero Sequence impedance is very low (just the transformer), while Z1 includes the upstream source impedance, making Z0 ≪ Z1.

Effectively Grounded Systems (DLG)

Why: Common in systems where Z0 is low (effectively grounded) but not zero. It represents a transition zone often found near grounded generation or specific neutral reactor sizing configurations.

Transmission Lines / Ungrounded (3-Phase)

Why: Far out on transmission lines, Z1 and Z2 are roughly equal, and Z0 is typically much larger (Z0 ≈ 3Z1). Also applies to ungrounded or resistance-grounded industrial systems where Z0 is infinite or high.