Re: NEWCASTLE ACCIDENT

[pierson@gone.enet.dec.com (dave pierson)]

In article <366EA2D9.E1C@acay.com.au>, Michael Van Baast <vanbaast@acay.com.au> writes...

>> The power was probably off within seconds of the accident.  It wasn't
>>officially "isolated" until the earths were up.

>how do you effectively earth a train?,

	Procedures will vary, they will be documented in the safety rules
	of the relavant RR.  Usually defined as to be executed by a trained
	employee.

>weld thumping great big bits of copper between the body and the rail?

	The ones typical in the US are roughly:
		Using approved cables, connect between grounded metal
		structure or rail and wheels or bodywork of vehicle.
		Ground end to be connected first.
	[prevents the ground being completd thru the groundor.  If the
	train is dead, it makes no differnce, if its 'live', then it
	saves a life.]

	Cables will have heavy spring jaws and/or screw type clamps,
	and be of sufficient size to carry tripping current, forcing
	a fault to open the breaker if necessary.  Fitted to allow insulated
	operation.

	'grounding' is common in power industry, with standard practices,
 	Electric RRs are simply a special case.  There are two issues requiring
	grounding (more?):

		The circuit might NOT be off, thru misoperation, or chance.
		An off_but_ungrounded circuit can have lethal voltage &
		current levels induced from live ones, especially with long
		parallel runs (eg: RR OHLE).

thanks
dave pierson                        |the facts, as accurately as i can manage,
Compaq Computer Corporation         |the opinions, my own.
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Shrewsbury, Mass USA                 pierson@gone.enet.dec.com
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