Fault Level & Thévenin Equivalent Calculator

Calculate fault current and fault level from Thévenin equivalent voltage and impedance. Compare strong and weak source conditions for power-system fault analysis.

Input Parameters

kV
Ω

Results

Fault Current (If)
15.24 kA
Fault Level (Sfault)
3485 MVA
Equivalent Impedance
5.000 Ω
Source Strength
Strong

💡 Engineering Insight

Lower equivalent impedance allows the network to supply higher fault current (15.24 kA). This corresponds to a stronger source at the fault location.

Thévenin Equivalent Circuit

Vth132 kVZth5.00 ΩFaultIf = 15.24 kA

About This Calculator

This calculator helps you explore the relationship between Thévenin equivalent impedance, fault current, and fault level at a specific location in a power system. The tool supports two input modes:

  • Impedance in Ohms: Enter the system voltage and equivalent impedance directly in ohms. Optionally specify resistance and reactance components.
  • Impedance in Per-Unit: Enter the system voltage, base voltage, base power, and per-unit impedance. The calculator converts to ohms automatically.

Key Outputs

  • Fault Current (If): The maximum symmetrical fault current available at the fault location, calculated using If = VLL / (√3 × Zth).
  • Fault Level (Sfault): The three-phase fault MVA rating, calculated using Sfault = √3 × VLL × If.
  • Source Strength: An educational classification (strong, moderate, weak) based on the calculated fault level. Lower impedance allows higher fault current and indicates a stronger source.

Comparison Mode

Use comparison mode to evaluate two different cases side by side. This is useful for:

  • Comparing fault levels at different network locations
  • Assessing the impact of impedance changes on fault current
  • Understanding how network strength varies across a system

Engineering Context

The Thévenin equivalent representation simplifies a complex power network into a single voltage source and equivalent impedance as seen from the fault location. This approach is fundamental to fault analysis and helps engineers:

  • Size protective equipment and circuit breakers
  • Design earthing and grounding systems
  • Evaluate network strength for inverter integration
  • Assess voltage stability and transient response

Related Article

For a comprehensive explanation of Thévenin equivalent networks, fault level calculations, and source strength interpretation, see: Thévenin Equivalent, Fault Level and Source Strength.