Why does the voltage in response of a short circuit oscillate for phasor and not for discrete phasor?

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Besrat T on 17 Feb 2022
Answered: Kothuri on 23 Feb 2024
Hello,
I simulated the power_turbine model and get different voltage response to the short circuit running it with phasor and discrete phasor. During the short circuit the voltage response does osciallate for phasor, while not for discrete phasor. (I added to the model a three phase VI measurement between the SM and the transformer and took the voltage from there.)
I understand that the discrete phasor and phasor calculate the response differently. The discrete phasor solver calculates the sum and creates the solution, while the phasor solver integrates the solution. But why does the phasor solution oscillate and the discrete phasor solution doesn't?

Kothuri on 23 Feb 2024
I understand that you want to know why the voltage response oscillate during short circuit for phasor and not for discrete phasor.
This is because:
• During “Phasor analysis”, the simulation directly represents the time-domain response of the system. So, if a short circuit occurs, the physical phenomena of the system can cause transient oscillations as energy is exchanged between the magnetic and electric fields. These oscillations are a natural part of the system's response to the sudden change in conditions and will be visible in the simulation until they are damped out.
• When using “discrete phasor analysis”, it effectively samples the system's response at discrete time intervals. If the discrete model includes simplifications that ignore certain high-frequency dynamics or if the sampling rate is not high enough to capture the transient oscillations, the resulting simulation might not show these oscillations.
Therefore, by ensuring that the sampling rate is high enough according to the Nyquist criterion you can capture the required dynamics.