I am trying to plot phasors (A-,B-,C-phase voltages) in Mathcad 14 on the same polar plot. When I try to add more than one voltage to the plot, it shows the symbol at the origin but will not plot it correctly. Anyone else run across this problem?
I was having a conversation with a vendor today and he stated that you could layer FR clothing to get the desired FR rating. For instance, if the arc flash hazard is 59 cal/cm2 then you could wear 12 cal/cm2 coveralls and a 55 cal/cm2 suit (12 + 55 = 67 > 59).
I have never heard this and...
We received an arc flash study from a contractor & I have been asked to review it. The contractor did not model any of the protective devices (PD), but made these assumptions.
1) That the first PD will operate in 6-cycles.
2) That the backup PD will operate in 1-second if the first fails.
I...
Hello all,
Anyone have a TCC curve for the Westinghouse CO relay in the picture? The model number we have been given is 1271071-A. It appears to be an 'old' relay. Thanks.
Any information will be helpful if you have even seen this one before.
I have already contacted my local GE rep, but no response from him yet. I was hoping that someone could help me with information on a GE IAC11 relay. Specifically I am looking at coordination and I really need the TCC for such relay.
Thanks in advance for any assistance with this - hoping...
I am trying to find a cost difference for 1/O EPR cable from 2006 as compared to today. Anyone have/know the cost difference?
I know copper has went up significantly, but I am unsure as to how much in that time. Any help is greatly appreciated. I have asked a vendor, but no reply yet.
I have tried searching Eng-Tips, and the GE website, but I haven't been able to find information for a GE AK-2-50 circuit breaker. Specifically, I am looking for the interrupting ratings of the breaker.
GE support thus far has not been of any use - they seem as lost as me.
Thank you in...
Ok, I am fairly new to the arc flash issue so I am hoping to get some assistance from the more experienced engineers out there.
In the table notes, it mentioned clearing times of 0.03sec (2-cycles). What devices clear in 2-cycles (other than fuses)? Does this include breaker operating time?
I...
I am looking for a kind of poll on this. My question arises out of a conversation about whether to perform an arc flash analysis or to use the NFPA table. The electrical system is a small facility with a single utility feed.
The 480V system is my main concern. Are people just assuming the NFPA...
I have checked the Siemen's website and can't find it. Anyone know where I might find it.
I wish manufacturers would learn that even though a product has been 'obsoleted' that the material (i.e. IM's) should still be left out on the web.
I was hoping to get everyones help on this. I see that several manufacturers offer arc suits up to 100 cal/cm^2 but my understanding of the NFPA70-2004, Table 130.70(c)(11) is that anything above 40 cal/cm^2 can not be worked on energized.
My understanding is at above 40 cal/cm^2 the blast...
First, let me say I ahve a deep respect for our brethern with Engineering technology (ET) degrees. This is important in this discussion.
My former employer is now using a electrical technician and ET engineer to perform arc flash hazard analysis for customers.
They claim that the owner (a...
Hello all. I am trying to gain a better grasp of K-factor as associated with breakers and MCCs. It was mentioned to me by an associate that he had 15kV equipment being operated at 6.9kV so the K-factor would affect the short-circuit current available. This is a new subject to me so I am hoping...
I am new at this and still learning so I thought I would ask for the commmunities help here. Field data was given to me for a 14.4kV-480/277V, 1000kVA, Balteau Standards transformer using tap D (12.47kV). It has always been my understanding that the standard taps are +/- 2.5% and +/-5%. I figure...
I keep coming across this problem and I am hoping to find out what everyone else is doing. I have a pad-mounted 12.47kV/480V, Wye-Wye, 500kVA transformer with a C12 bay-o-net fuse on the primary.
My arc flash analysis shows that the hazard exceeds category 4 between the transromer secondary and...
I am having a disagreement on NFPA70E and IEEE1584-2002 with a collegaue. He believes that arc flash boundaries apply AT ALL times (i.e. no maintenance, inspection, or electrical work). I believe that the arc flash requirements only apply while performing 'live' electrical work.
Can I please...
