Warning 107 | [PSS®E] | Thévenin source impedance abnormally low

Relevant software:

PSS®E

Emitted message:

Detected abnormally low infinite generator source impedance

tip

If your PSS®E Dynamic results appear stable you can ignore this warning.

Description:

This warning indicates that the PSS®E model contains an Thévenin source with an abnormally low source impedance.

Possible impact:

• We have seen SMIB PSS®E models with R Source (pu) and X Source (pu) equal to 0 have unstable frequency responses (see below).
• We have also seen PSS®E Dynamic initial conditions with extremely large initial reactive power values which had similar instability.
  • For example, in the psse_log.log file generated by gridmo below, the ***** indicates that the number is too large to render in the space available.

Potential fixes:

• Review the Thévenin source's internal impedances - a minimum R Source (pu) value of 0 and a minimum X Source (pu) value of 0.0001 is recommended.