Re: I National Electric Code

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "davep by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davep-at-quik-dot-com>


> > One of the reasons why the clearances are so big for the higher voltage
> > stuff is probably so you can work on it (potentially while energized)
> > without worries of flashovers.  When I started looking at the OSHA rules, I
> > couldn't figure out why they wanted such big clearances for seemingly low
> > voltages.  Then, I found an "opinion letter" in the OSHA web site (such
> > letters are issued to clarify or interpret an OSHA reg for a specific
> > instance).  It indicated that the guidelines were developed considering a
> > nominal length for a worker's arm, how far they might move inadvertently,
> > etc.

	Just so.  I did a similar set of (informal) research re safety
	specs for RR Catenary.  Spark over is an inch or so.  Safety rule
	is 3 feet, which allows for human arm, plus tool (wrench, etc...).

	Also allows for 'traveling surges' (as noted) which can peak much
	higher.

	best
	dwp