Re: water spark gaps + oil info

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: "Bert Hickman" <bert.hickman-at-aquila-dot-net> 

Tesla list wrote:
> 
> Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net>
> 
> Hi Sundog,
> 
> Oil will also degrade under arcing. I have seen this happen at work as both
> a failure mode and a controlled test.
> For the controlled test we had a spark gap apparatus that was designed
> specifically for dielectric strength testing of oil. The electrodes looked
> like they were spaced about 1/8" apart. They had a flat arcing surface, were
> 1" in diameter and were made of brass.
> Normal, good clean Shell Diala AX broke down at 40 kv. This would hold true
> for about 20 or so discharges, but then after further discharges, the
> breakdown voltage would decrease. During an arc, a stinky gas bubble is
> released and carbon particles form in the oil. No one at work could tell me
> what the gas is... 

<SNIP

Sue and all,

It took a bit of digging to get the answer (beyond simply hydrogen and
methane gases). Per Frank Clark ("Insulating Materials for Design and
Engineering Practice", John Wiley & Sons, 1962, 1218pp), mineral oil
when subjected to electrical breakdown (via a 60 Hz arc), tends to
liberate approximately the following mixture of gases (in addition to
generating carbon particles):

	hydrogen gas	68%
	carbon monoxide	  9%
	acetylene 	  8%
	methane 	  7%
	ethane		  3%
	Others (mix...)	  5%
        Total:		100%

Some byproducts within the "Others" group can be a bit "stinky"
(toluene, vinyl acetylene, benzene, butadiene, propane...). It may be
some of these that account for the odor. 

There's no doubt that it's the hydrogen gas that accounts for much of
the desireable quenching action that utilities rely upon for proper
operation of distribution cutouts and oil circuit breakers. The arc is
extinguished during current zeroes by the quick recovery of the hydrogen
gas and the cooling effects of the surrounding oil envelope. However, in
addition to hydrogen, most of the other liberated gases also look to be
flammable (some explosively) when combined with oxygen.

-- Bert --