How is a system impedance of 10-20% considered a strong grid? How is this value determine and where is it being measured from. The generator up to the bus of the grid?
AIM... the impedance of an infinite (source bus) is always taken as zero, but it doesn't have to be.
The bus in your example could be considered "infinite" if the generator connected to it had a relatively large impedance compared to the source bus, say 10-20 times that of the source impedance.
As I have often said, it is difficult to explain with words, i.e., like defining what a ratchet is without using your hands.
I believe your dilemma can be easily solved with a diagram. If you want one contact me.
I guess I'm a tad bit confused. How can the impedance of an "infinite bus," the grid in this case be taken as 0 and not a very large value?
Also, how can a generator connected to a source bus ever be very large compared to an infinite bus with many other generators present on that bus.
When one measures system impedance at a plant, is it the generator up to the grid or the grid itself being measured?
I know plants have done step tests with excitation systems to verify system impedance by using the differences in field voltage and terminal voltage and dividing the two. How is this determining system impedance?
