🚀 go-pugleaf

In article <A%Yxd.11991$ry.7228@fed1read01>, HawkCW4 <HawkCW4@cox.net> 
wrote:

> Howard Berkowitz wrote:
> > In article <cq95c6$5lf$1@reader2.panix.com>, 
> > EskWIRED@spamblock.panix.com wrote:
> > 
> > 
> >>In ne.general Howard Berkowitz <hcb@gettcomm.com> wrote:
> >>

> >>
> >>It is crucial that the interconnecting generator be matched to the 
> >>system 
> >>it is connecing to.  How could it be otherwise?

Of course. But with an AC grid, this matching is much more complex than 
with DC.
> > 
> > 
> > If you connect with DC, there's no issue of phase and frequency match.
> 
> Howard, you really got my curiosity up now.  Maybe I miss the point you 
> are making, but are we not talking about moving power (electricity) from 
> the source to the market?  I believe you could run DC power and 
> accomplish everything you do now with AC but everyone is geared up for 
> AC and it would cost billions to convert everything to DC only.

Exactly.  DC power and supporting equipment avoids the potential for 
phase/frequency mismatch that has been a component of failures of 
interconnected AC grids. Traditionally, the grid has been AC, and you 
correctly observe converting would cost billions.

The conflict here is, to some extent, between the cost sensitivities of 
the commercial energy-selling market, and the need to protect critical 
national infrastructure both from natural disasters and terrorist 
interference.  If terrorists could infiltrate electrical power 
operations at grid interconnect points (especially AC interconnects), 
they could cause far more massive failures than the classic image of 
blowing up transmission towers, substations, or even generating plants.
> 
> 
> > 
> >>
> >> Newer, extremely high voltage systems are direct 
> >>
> >>>current (DC) with solid-state switching and no frequency or phase to 
> >>>match. DC also lends itself better to computer control.  
> >>
> >>DC?  Where?  For what?
> > 
> > 
> > A number of new, extremely high voltage (e.g., 750 KV and above) 
> > transmission facilities are DC, not AC. Since my experience is more 
> > with 
> > computer electronics, I was surprised, but heard from multiple trusted 
> > sources, that there have been reliable breakthroughs in semiconductors 
> > that operate in these voltage and power ranges.
> 
> It sounds like you are suggesting that AC and DC be transmitted on the 
> same transmission lines. I think that is doable as the AC will just ride 
>   along on the DC level.  But somewhere you will have to separate the 
> two for use at the subscriber level.  In that event, you will still have 
> AC entering the grid which must be phase aligned with what is on the 
> grid.

No, DC only, and principally on the highest-power lines that 
interconnect between different generating companies.  Subscriber 
distribution would remain conventional AC. The critical issue is at 
high-power interconnect points. 

> 
> In Palm Springs, I saw all those wind generators and wondered how the 
> heck they could be generating all that AC and then pour it onto the grid 
> to be sent down the line for use.  How do they synchronize that AC?  It 
> turns out to be simple.  They first excite or inject the AC from the 
> grid to the components of the Wind Gen and the resuling output is 
> already in sync.  But how does your system work?

Thyristors and extremely high-power rectifiers do the conversion between 
AC and DC, that in the past might have called for huge motor generators. 
Right now, AC grid interconnection often requires expert manual 
operation for phase and frequency match.  

By the time the power reaches subscribers, the AC matching issues have 
already been handled.
> 
> Ed
> USA Ret
> > 
> >>>Unfortunately, to upgrade the North American grid interconnection 
> >>>system 
> >>>will have a cost in the tens of billions, at a time where competitive 
> >>>utilities are extremely sensitive to cost.  Incidentally, some 
> >>>upgrades 
> >>>will also harden the grid against high-tech terrorism.  So far, we 
> >>>haven't seen major deliberate attempts, but there was a warning in one 
> >>>of the more recent Northeast blackouts. While the Supervisory Control 
> >>>And Data Acquisition (SCADA) networks for the power grid should be 
> >>>totally isolated from the Internet, we had at least one incident of a 
> >>>bored contractor attaching a SCADA computer to the Internet with 
> >>>personal equipment, which allowed a virus to get into the electrical 
> >>>SCADA system. 
> >>
> >>Do you have a cite?  I searched Google News for SCADA Virus and found 
> >>no 
> >>articles.

Try SCADA+electrical+worm.  Over 4000 hits.  One link, 
http://www.computerworld.com/securitytopics/security/story/0,10801,84519,
00.html discusses how Slammer and other worms leaked from corporate 
servers into SCADA.
> > 

There have been discussions that spawned from the Clinton Administration 
Presidential Decision Directive 63 on critical infrastructure. I worked 
with the critical infrastructure people in the Federal Y2K Information 
Center, and the idea of government subsidy to harden the grid was 
definitely discussed.  

I have to give the disclaimer that my professional expertise in the 
engineering of critical systems is in the routing and transmission 
architecture of the Internet and other communications networks. 
Nevertheless, some of my work has involved looking at the multiple 
systems of critical infrastructure that can affect communications.