HVDC Power Re: Water sparks (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Mon, 11 Aug 2003 16:16:55 -0400
From: davep <davep@xxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: HVDC Power Re: Water sparks (fwd)


>>From: davep <davep@xxxxxxxx>
>>	I guess it depends on the definition of 'pure'.
>>	Where PURE (technical definition) water is
>>	used or insulators (eg the 1 MV DC Line
>>	that (helps) power my neighborhood...) it means
>>	99.9999 (++) % pure.

> Whoa!  What?  You have a DC line in your neighborhood?

	They all have to be somewhere.  8)>>

> You have a 1MV line near your neighborhood??

	about 10 mi away, depends on the definition of 'near'.
	One end 'here' (outside Boston, MA, USA,
	'tother in Quebec, Canada.)

> I thought such things were only used for long-haul major

> network balancing tasks.

	...or for exporting bulk power.  It WILL
	work both ways, but doesn't, i think, get
	used that way.

> The highest voltage lines in North America are supposedly

> five inter-network load balancing lines,
> just air-insulated towers, which run at 750kV / 60Hz.
	This is +/- 500KVDC.


> As for water insulation, since it so easily ionizes after a

> voltage

	Its what they use.
  	(It was an IEEE Tour...)

> has been placed across it for a short time,

	Doesn't seem to bother its use.  Its used to
	'cool' the inverter stacks (LOTS AND LOTS)
	of solid state devices (i forget which....)
	stacked in series.  Top end is at + (bottom -)
	500KVDC, at 100 A (if i recall....).
	Line and etc are set up to allow temporary
	operation at 1MV to ground, in case of need.
	Thus (since its the inverter) there is a pulse
	component, but lotsa DC.  Like most any
	insulator, if 'enough, plus margin' be used
	its OK...


> I was under the impression it was only used for pulse

> work.  I have never heard of high voltage transmission

> lines being insulated with water.

	The _lines_, being outside are air insulated.
	The indoor bits, notably the inverter stacks,
	are water...  Very Pure Water...


> I am very, very skeptical that this is being done,

	It's being done.
	8)>>
	ASEA (as was) engineered it, if i recall.
	May have been a technical paper on it, eg
	IEEE proceedings?
	My visit was on an IEEE Boston Section Tour,
	perhaps a decade back.  Plant is still there.


> but I'd be interested to be proved wrong.
	I've not got a nice IEEE paper, tho one may

	exist.  I do recall there is continuous, on

	line, real time, monitoring 'filtering' to
	maintain.

	best
	 dwp

...the net of a million lies...
	Vernor Vinge
There are Many Web Sites which Say Many Things.
	-me
...for he has read everything, and written nothing...
	A J Raffles