How to simulate 2 systems with different frequency in one file?

answered 2020-08-07 04:48:15 -0500

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In PSSE all network data are stored in pu.

It is possible to have one saved case combining a 50 Hz and 60 Hz system, but that saved case will only have ONE base frequency; 50 or 60 Hz. You can't assign base frequency to individual buses.

Before reading the raw data for the second system you must change the frequency at the first line in the raw data file to the frequency of the first system. Also, change the IC code to 1. Note, there is no need to recalculate any branch or transformer data.

The line capacitance in the second system will be shown wrong (in spreadsheets and reports) if transmission line input option is set to Ohms, since the capacitance is calculated with wrong base frequency. However, the pu value is correct and the load flow is correct.

That means it is just to pretend that, for example, the 60 Hz system is a 50 Hz system and add it to the 50 Hz system.

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Hi Perolofl, Thank you for your feedback. I get the idea but I couldn't comprehend completely. I am familiar with per unit system for power, current, voltage and impedance. But I never knew that frequency can be stated in per unit.

wibowo ( 2020-08-07 06:18:43 -0500 )edit

In load flow the base frequency is only used for conversion of susceptance in pu system base to capacitance in microFarad in the GUI if line option is Ohms. So, there is no problem to have 50 Hz and 60 Hz systems in the same saved case.

perolofl ( 2020-08-07 09:34:22 -0500 )edit

PSSE is using pu speed deviation, not Hz. At nominal speed (50 or 60 Hz) the pu speed deviation is zero. At under-frequency the pu speed deviation is negative.

perolofl ( 2020-08-11 15:01:31 -0500 )edit

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How to simulate 2 systems with different frequency in one file?

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