Ipsa 2 Fault Level


  • Balanced and unbalanced faults
  • Full D-Q axis machine model calculations
  • IEC 60909 calculations also included
  • Fault waveform graphs


  • Simple data entry 
  • Included in all versions of Ipsa
  • Accurate results used by the nuclear and defense sectors
  • Calculate switchgear and busbar ratings

Fault level calculations are a critical consideration in power system studies and therefore both the fully detailed D-Q axis machine model and IEC 60909 calculation methods are included as standard with all versions of Ipsa.

Full D-Q Axis Machine Fault Level Analysis

This calculation method is based on full D-Q axis machine models including saturation effects, saliency, sub-transient and transient decays and second harmonic effects.  

This technique is applied to all rotating equipment providing accurate and proven fault level results. The underlying calculation algorithm has been in use for many years and has empirical validation.

Fault currents for the following fault types can be calculated at any specified fault time:

  • Three phase, L-L-L
  • Single phase to ground, L-G
  • Phase to phase, L-L
  • Phase to phase to ground faults, L-L-G

 The following results can be displayed on the network diagrams or viewed in a results spreadsheet:

  • Peak, asymmetric and symmetric RMS fault results
  • Individual phase current results
  • Sequence currents and voltages
  • Retained busbar voltages
  • Fault waveform plots
  • User defined fault times
  • Fault Waveforms
    Fault Level Waveform Graphs in Ipsa

Circuit breaker duty (pass/fail) calculations can be undertaken for busbars and circuit breakers. The peak current and break current ratings are compared at the correct fault times and the percentage DC component at break time  is also checked.

Zero sequence networks and components such as neutral earthing resistors and transformers can be modelled for representation of earthing systems. Transformer vector groups are specified to provide accurate calculation of  through fault and earth fault currents.

Pre-fault loading is accounted for and flat voltage profiles can be applied before calculation.  The X/R ratio can be calculated from the driving point voltage or obtained from a full DC decay method.


IEC60909 Fault Level Analysis

The calculation is a robust implementation of the IEC 60909:2001 standard.

Voltage correction factors can be specified and default synchronous machine power factors can be set.

All three methods of calculating the X/R ratio (A, B and C) are provided.

Full results are provided for all fault types.