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Thanks Bill for the added information!

Thanks for the fast response! So, why would it be safer to just keep the neutral connected? Because the neutral provides a reliable path to ground?

Hello all, I am wondering if there are any advantages to using a 4-pole contactor when switching 3 single phase loads that operate phase to ground. I have a lighting circuit branch that is fed by a contactor. The lights are connected phase to ground on a 600V three phase system (e.g. lights...

Hey all, Been a while since I have posted or been on this forum. I was contacted by a contractor who has already installed grounding infrastructure for an islanded 600/347V system supplied by a 2MW generator. The island system has a section of 27.6kV overhead line to reach the far side of the...

Hi, I have a question regarding line-ground currents and artificial neutrals. I am modeling a solar power plant. The PV arrays' generated power is inverted and transformed onto a 27.6kV collector system which is then stepped up to 115kV to the grid. The main transformer is a 20MVA...

Thanks for the help Skogsgurra and Cranky. I am required to use EasyPower in the analysis, which has a limited number of fields to enter data. It includes Full load rating and KVA of the inverter plus short circuit rating (based on a multiple of FLA) and the duration. Just as you were stating...

Hello, I am performing an arc flash study of a PV plant with EasyPower and noticed something curious during analysis. If a DC bus is faulted, there is no contribution from the AC-side of the inverters that I have modeled. This wouldn't be true though as far as I can reason, since if the IGBTs...

Thanks for the input both Mike and desrod. The harmonic study requested scope in the bid document only had about four sentences in it. I would imagine this is because harmonic studies haven't had the same level of scrutiny as arc flash studies in recent years (there were five pages of...

Hello, I have been requested to perform an harmonic analysis for the very first time (always exciting to learn new stuff [smile]). I have some training in this study area but to date have never applied these concepts. Specifically I am going to be performing an analysis at a water treatment...

Does anyone perform power system studies (short circuit studies specifically) in Canada? I do many studies in Canada (being that I live here) and I have come across something I probably should have asked earlier in my career: are UL 508A and NEC 2005 Standards and Rules regarding SCCR applied in...

Series rating is highly theoretical... that let-through energy, up-over-and-down, or what ever approach might be attempted won't be accepted unless validated through recognized third party testing. That is my understanding with series ratings (and applying CLF as well). The idea of increasing...

The cable limiter would only do you any good if you can find a Listed series rating combination where the bus duct was tested by an NRTL with the cable limiter and found to be suitably protected. But don't hold your breath while you look for that wild goose. Thank you very much davidbeach. I...

I apologize eddunnpe, the value at the beginning is 27kA. I erred in the first posting.

Hi 7anoter4, It is actually the Square D CP bus duct with the 22kA withstand I am worried about; I am not concerned about the cable. That was the issue: can cable limiters be used to protect the bus duct, or would it be better to look at a typical current limiting fuse (i.e. class J, RK, etc.)

Hi everyone, I am doing a short circuit analysis on a manufacturing plant in the U.S. and have come across some bus duct runs in the plant that are under-rated for the calculated short circuit currents (22kA rms rated withstand, vs 27kA momentary short circuit, calculated at the end of the 100'...

Got a hold of St Leonards Works this morning. Talk about the easiest technical support service to get in touch with ever! Thank you very much for that tip ScottyUK. Tim

Thanks ScottyUK. It is a little late in the day to phone today, but I will try giving them a ring on Monday when I am back in the office. Tim

Hi there, I have some data for a power system model I am creating and I have come across a GEC low voltage breaker with a CTZ relay on it. Does anyone know of a source I can go to to find information on this relay, specifically TCCs? I have tried the internet and my typical manuals site, but to...

Thanks dpc. I suppose it would not be relevant since like the fuse, current will not actually go through the switch in the case of line side faults. Is there any generally accepted practice with regard to line side faults or is this something that is typically neglected?

Hi everyone, I have a question that is nagging me about short circuit ratings of LV fused disconnect switches. On many low voltage disconnect switches two short circuit ratings will be given. One will be given as 5 or 10kA with the statement "when installed fuses are Class H or Class K"; the...