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What is the rationale behind dividing a line inductive reactance already in per unit (XL(pu)) by base angular frequency (2*pi*F) to get Lpu?

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By implementing Lpu = Xpu/(120*Nominal Frequency) in this video (https://www.youtube.com/watch?v=TfJmQTafwEI) confuses me because i think Lpu is not more longer in per unit and without dividing by this angular frequency my simulation does not give desired results. The procedure implemented in this link : (https://www.mathworks.com/help/sps/ug/per-unit-system-of-units.html) looks more standard but it does not work in my simulation unless i already divide Lpu by base angular frequency again.
PLEASE do assist me out.
Thank you

Answers (1)

Jack
Jack on 3 Apr 2023
The equation Lpu = Xpu/(120*Nominal Frequency) is commonly used to convert the reactance Xpu of a component from its actual value to its per-unit value with respect to the system base impedance. This equation assumes that the system frequency is constant and that the units of Xpu and Lpu are both in per-unit.
The reason for dividing by the base angular frequency is to convert the reactance from its actual value in ohms to its per-unit value with respect to the system base impedance. The base impedance is typically defined as the impedance of the system at the nominal frequency, which is why the nominal frequency is used in the denominator of the equation.
If your simulation requires the reactance Xpu to be divided by the base angular frequency again, it may be because the simulation is using a different definition of the per-unit system than the one used in the video or in the MathWorks documentation. It is important to ensure that all values in the simulation are in the same units and reference frame to avoid errors and inconsistencies.
To ensure that your simulation is using the correct per-unit system, you may need to consult the documentation of your simulation software or seek assistance from the software vendor or community. Additionally, you may need to verify that all values in your simulation are correctly scaled and referenced to the system base impedance and nominal frequency.
  1 Comment
Kamilu Sanusi
Kamilu Sanusi on 3 Apr 2023
@Jack Thank you so much for the response.
The reason for dividing by the base angular frequency is to convert the reactance from its actual value in ohms to its per-unit value ..PLS here, the reactance is already in pu and not actual.
Please look ATTACHED analysis and advise me accordinly. Thank you sir

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