Knowledge Base

How does Simulator convert transmission line flow between MVA and Amps?

Variables that are calculated by a power flow are the MVA flow leaving a bus along a transmission line and the bus voltage.

-The MVA flow is the total MVA flow on all three phases of the transmission line (S3-ø).
-The voltage is the line-to-line voltage (Vline-line)

Current is only defined for a single phase, so in order to determine the single phase current, solve

S1-ø = Vline-nuetral * I (where I = current)

To convert the values the power flow calculates to the ones in this equation, do the following

S1-ø = S3-ø / 3
Vline-nuetral = Vline-line / sqrt(3)

Thus we can write

S3-ø / 3 = Vline-line / sqrt(3) * I

Which simplifies to the equation used to determine the current on a transmission line

I = S3-ø / ( sqrt(3)* Vline-line )

Note: The same equation is true for a transformer.

Tags: ,,

July 5, 2012