HenryOhm
Electrical
- Jun 22, 2005
- 59
Hi All,
I was just curious if anyone has any better or contradictory information on transformer inrush probability than this excerpt I found (out of a PhD thesis by Jinsheng Peng, "Assessment of Transformer Energisation; Transients and Their Impacts on Power Systems", Pg. 174):
"Furthermore, it was found that the probability of reaching the worst case dip magnitude (estimated by the commonly agreed worst case energisation condition) is lower than 0.5%, indicating that the worst case scenario is unlikely to occur in a system; in fact, about 80% of the dips are likely to be with magnitudes lower than 0.6 pu of the worst case."
I'm on a project involving an islanded power system. We have a couple of transformers that will be powered by either one or two generators. The transformers are fairly large relative to the size of generators so we are planning on some inrush testing before start-up.
The purpose of our testing is not to find the 0.5% worst case condition. If the above probabilities and my math is right, we'd have to energize one of these transformers 138 times to have a 50/50 chance of seeing that 0.5% level of inrush. However, if testing one of them 10 times has a really good chance of seeing the 0.7-0.9 pu type of inrush, that's what we really want to see. We want to measure voltage dip magnitude and duration during this testing and imagine some sort of distribution as indicated by the 5 x 4 grid of 20 inrush curves, Figure 6, about 2/3 down the page of this link:
Thanks for any and all help!
I was just curious if anyone has any better or contradictory information on transformer inrush probability than this excerpt I found (out of a PhD thesis by Jinsheng Peng, "Assessment of Transformer Energisation; Transients and Their Impacts on Power Systems", Pg. 174):
"Furthermore, it was found that the probability of reaching the worst case dip magnitude (estimated by the commonly agreed worst case energisation condition) is lower than 0.5%, indicating that the worst case scenario is unlikely to occur in a system; in fact, about 80% of the dips are likely to be with magnitudes lower than 0.6 pu of the worst case."
I'm on a project involving an islanded power system. We have a couple of transformers that will be powered by either one or two generators. The transformers are fairly large relative to the size of generators so we are planning on some inrush testing before start-up.
The purpose of our testing is not to find the 0.5% worst case condition. If the above probabilities and my math is right, we'd have to energize one of these transformers 138 times to have a 50/50 chance of seeing that 0.5% level of inrush. However, if testing one of them 10 times has a really good chance of seeing the 0.7-0.9 pu type of inrush, that's what we really want to see. We want to measure voltage dip magnitude and duration during this testing and imagine some sort of distribution as indicated by the 5 x 4 grid of 20 inrush curves, Figure 6, about 2/3 down the page of this link:
Thanks for any and all help!