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 Post subject: Question about table 410-2 ieee.c2. vs arcproPosted: Thu Mar 15, 2018 2:02 am

Joined: Wed Nov 01, 2017 6:09 am
Posts: 27
For my understanding of this tables:
It is used some kind of distance from arc:"Calculated by using minimum approach from Table 441-2 and subtracting two times the assumed arc gap length"
Does this mean that for instance the 161 to 169 kV calculation is done wirth the following input:
Ik= 20kA(assumed single phase)
Arc Gap distance 161kV/10=16.1 inch
Distance to gap: (From table 441-2): 51 inches(10ft3inch,use T=3)-2*16.1 inches=19 inches
If I do calculation with arcpro(is was told that this tables where made by using arcpro?), input shown in picture. I get a result of 11.9 cal/cm2 and not 4cal

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 Post subject: Re: Question about table 410-2 ieee.c2. vs arcproPosted: Thu Mar 15, 2018 8:27 am
 Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 566
The table uses line to line voltage, but when finding arc length the note 1 says to divide the line to ground kV by 10. Your calculated arc gap should be divided by sqrt(3).

When I've looked at this in the past, I found the tables did not necessarily correspond to the MADs in the same revision of the NESC. Looking back a revision or two produced better results.

Why 9.3 cycles? Tabulated value is 11.9.

Might try changing the electrodes; I forget which gave better results.

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