Talk:Arc flash

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Electrical engineering Low‑importance

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Untitled[edit]

First, see Casey Harmon. Second, everything else. — Preceding unsigned comment added by 204.61.48.20 (talk) 23:20, 22 November 2013 (UTC)[reply]

I made some changes to make shorter/cleaner and remove some of the concrete statements that are not always true. ~Bajarider — Preceding undated comment added 22:57, 2 October 2007 (UTC)[reply]

Took out the paragraph that states breakers don't reduce the hazard - Thousands of calcs on 100's of different devices - They make a difference and so does almost any fuse. Fuses are generally quicker on higher fault currents and breakers are generally quicker on lower faults. ~Bajarider — Preceding undated comment added 22:57, 2 October 2007 (UTC)[reply]

Changed the note that said 480v is not usually a hazard to 240v according to the appendix in 70E and the IEEE1584 notes. ~Bajarider — Preceding undated comment added 22:57, 2 October 2007 (UTC)[reply]

I don't like the last paragraph;What OC is going to let 20KA through for 10 cycles? Very unusual. ~Bajarider — Preceding undated comment added 02:07, 3 October 2007 (UTC)[reply]

Could happen - 20 kA could easily be the current let-through by a 1000 kVA 5% 480 V 3 phase transformer, and though we'd like to believe breakers always open in 5 cycles, 10 cycles is not inconceivable. Sometimes it's the backup breaker that clears the fault. --Wtshymanski (talk) 13:54, 17 April 2008 (UTC)[reply]

Assuming a circuit that with a 100 amp circuit breaker (which is the main breaker for the motors in my shop), I have difficulty seeing current zooming up to 20,000 amps before the breaker trips. What kind of circuits are you talking about where it can zoom up to 20,000 amps? What amperage breakers do they have upstream? My house has a 200 amp circuit breaker. I have had instances where I have plugged in defective appliances and have had nothing described in this article. We even had a stove with a defective burner that 'popped' when we plugged it into the 220 volt socket. Perhaps some time I should try putting an amp probe for an osciloscope around a piece of wire and then plug it into a 30 amp breakered socket and see what my current peak is??? Allyn (talk) 13:00, 13 May 2009 (UTC)[reply]

Very late reply - Suppose your power transformer has 5% impedance, which is typical for a moderately large oil filled transformer. If it can deliver 1000 amps at normal full load, that means if shorted it can momentarily pass 20,000 amps.

it's not at all unusual to see unit substations in industry with 2000 or 3000 kvA transformers feeding them. You're not going to see 20 kA fault levels on a residential panel board because utility practices make sure that can't happen - they restrict the size of feeder transformers, otherwise householders would have to upgrade past the code minimum interrupting rating for their panel boards. --Wtshymanski (talk) 15:57, 29 November 2009 (UTC)[reply]

Voltage[edit]

There is a problem with this: "...systems operating at less than 240 volts phase to phase (120V to ground) when fed by...".
Either the phase to phase voltage is 240V and the phase to ground is 138V, or the phase to ground is 120V and phase to phase is 208V.
$V_{line-line}={\sqrt {3}}\cdot V_{line-neutral}$
— Preceding unsigned comment added by 12.216.36.105 (talk) 13:38, 17 April 2008 (UTC)[reply]

Consider a three wire single phase circuit, 120/240 V. True, I don't like calling the energized conductors of a single-phase circuit "phases", but not everyone is as fussy as I. --Wtshymanski (talk) 13:54, 17 April 2008 (UTC)[reply]

protection[edit]

Needs a paragraph covering containment once an arc has been initiated, both GE & Moeller (Eaton Corp) have solutions to extinguish an arc, once initiated in under 10ms. —Preceding unsigned comment added by 80.195.94.134 (talk) 18:03, 23 December 2009 (UTC)[reply]

External Link Spam[edit]

This article has several external links which appear to violate Wikipedia's External Link policy. Njivy (talk) 16:45, 29 September 2011 (UTC)[reply]

Suggest merge[edit]

Breakopen is a one-line definition that needs the context provided by this article. --Wtshymanski (talk) 21:31, 26 January 2012 (UTC)[reply]

Support - Merging the one-line article Breakopen to this article, then redirect the "Breakopen" article to this one. Northamerica1000^(talk) 02:23, 30 January 2012 (UTC)[reply]

Link to info about arc-fault interrupters?[edit]

This is one of those "probably-not" suggestions. GFI's are commonplace, but arc-fault interrupters (for household and small-office circuits) are not, yet, partly because of cost. Thought is to provide a brief link to discussion[s] of arc-fault interrupters, with a concise description (if that's possible).

A neighbor has photos of a dime coin that dropped onto the prongs of a (U.S.) domestic power-cord plug that was not fully inserted. There was an arc fault, and it burned notches into the edge of the coin. European wall outlets seem better designed to make such an event less likely. He probably still has the coin, itself.

Regards, Nikevich 14:03, 19 July 2012 (UTC)[reply]

Are you thinking about Arc-fault circuit interrupters? These are now required for bedroom circuis in the current editions of the Canadian and US electrical codes. --Wtshymanski (talk) 18:13, 19 July 2012 (UTC)[reply]

Recent copy edits to main article[edit]

In my opinion, the article is superbly written, good enough to serve as a reference in a legal case. One instance of jargon, introducing the best variety of protective fabric, however, used the word "solution", which seems to be the current fad, as "system" was, a few decades ago. The sentence needed cleaning up. No big deal, but expressing this in the edit description was a challenge.

Why the author didn't use [²] for superscripts is mildly puzzling. Perhaps the text editor or word processor made it too clumsy to type. (It definitely was, for me, until I loaded it into the Clipboard!) Superscripted 2's were just too big. they didn't look really bad; this was just an enhancement.

Best regards, Nikevich 14:03, 19 July 2012 (UTC)[reply]

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Example[edit]

I think that the given example provides a wrong impression. ("As an example of the energy released in an arc flash incident, in a single phase-to-phase fault on a 480 V system with 20,000 amps of fault current, the resulting power is 9.6 MW.") In reality, the cables that supply power to the electric arc do have a resistance and at 20 kA there will be significant voltage drop over the cables. So the resulting power in the arc might still be high but significantly lower than the given 9.6 MW. Also, the circuit should usually be equipped with a fuse that shuts down the short-circuit current in a much shorter time than the 10 cycles given in the example. --136.8.33.70 (talk) 16:19, 17 November 2017 (UTC)[reply]

I hope you never have to deal with the consequences of an arc flash incident. Even if you allow 5% reactance in the transformer and 5% impedance in the wiring up to the point of the arc (that's conservatively high), that means your source transformer could be as small as 1000 kVA - that is a common as dirt size for a power transformer in an industrial or commercial plant. It will lively be served by a utility source with much higher fault level, so you will not get any limitation there. The power level is quite feasible and illustrates the magnitude of the power available in an arc. --Wtshymanski (talk) 17:21, 17 November 2017 (UTC)[reply]