[NLRS] New Iowa noise source proposed.

[Barry VE4MA]

Good Morning Jerry,

I do not want to get drawn into a long thread. I don't think you have much
to be concerned with this planned line.

Manitoba Hydro, my former employer for 37 years, has operated 2 HVDC lines
since 1971 carrying 80% of our power on +/-450 aand +/- 500 kV lines from
the far north of VE4 near Gillam down to a site near Winnipeg some 1000 km
distant.  The lines are designed for low conduction losses ( ~2000 A) (in
our case have an 8 ohm loop resistance) but also are designed to minimize
corona loss by using multiple conductors spaced to give the effect of a much
larger conductor.  By lowering the corona loss the radio noise is
substantially reduced.  Our HVDC lines can be hear as you pass underneath in
your car, but are much quieter tha 230 kV AC lines in the same area.  The
noise is also reduced by using DC as there is no voltage peaking and no
continuous cycling of course.  Power flow is normally ramped by changing the
current.

The stations can be very large or small depending on how they are designed
to operate. Of course there are thyristors generating an AC waveform from
the DC or rectifying the AC  incoming energy. Living close to one of these
stations is probably not going to be good from a weak signal perspective,
however I don't think at VHF it will be significant if you are outside the
station fence. 

The switching equipment is normally in shielded rooms and the conductors are
usually filtered to stop harmonics of the switching from radiation out the
conductors.

Stations in Canada are built to external standards for audible and radio
noise emissions, as are transmission lines.  I cannot recall the standard
names and whether it is CSA  or even now IEEE but new or modified stations/
lines have to be comply accordingly. These are not distribution lines that
snake through residential areas and are not regularly maintained!

I know in 1980 we built a 500 kV AC line that goes to Duluth MN and later
Chisago station N of Minneapolis.  This line passed right beside a VHF
repeater radio site operated by the RCMP ( who objected strongly) and we
promised to move their site if there was deterioration in their site
performance.  There was no apparent deterioration in the site !

HVDC lines can have taps but that is incredibly complicated to design &
operate. Manitoba Hydro can parallel 2 HVDC systems onto one line in an
emergency.

Manitoba Hydro is presently moving towards installation of a third HVDC
system called Bipole III.

There is a lot of interesting stuff on the Manitoba Hydro website
www.hydro.mb.ca and search on HVDC

Best 73
Barry VE4MA

-----Original Message-----
From: nlrs-bounces at mailman.qth.net [mailto:nlrs-bounces at mailman.qth.net] On
Behalf Of Dr. Gerald N. Johnson
Sent: Thursday, June 23, 2011 8:53 PM
To: NLRS Reflector; newsvhf at mailman.qth.net; 'Badger Contesters';
'microwave at lists.valinet.com'
Subject: [NLRS] New Iowa noise source proposed.



There is a company proposing to build a +/- 600 Kv (two wire, not 
depending on a ground return like the one from Washington to Los Angeles 
out west) from NW Iowa to northern Illinois to provide a path for power 
from a couple thousand more wind mills. It won't have taps, just is 
planned to run power from NW Iowa to Illinois. Each converter station is 
expected to cost about a quarter billion bucks. I'm concerned that RF 
noise through microwave frequencies may turn its path into a noisy place 
unsuited for radio communications. AC lines are a bother but the noise 
happens only at the voltage peaks, 360 times a second for 3 phase lines, 
sometimes 720 times a second near a delta-Y connected transformer that 
introduces a 30 degree phase shift on the voltage waveforms. And noise 
blankers working on the noise peaks can be effective at shutting off the 
receiver during each noise burst. The trouble with a DC line is that 
there are not peaks, the RF noise is continuous and so the noise blanker 
is not effective at allowing reception. And at VHF and up, there's no 
significant propagation along the line so there's no correlation between 
the corona spikes from one pole to the next which makes cancellation by 
using two antennas not work. At an open house last week the engineer 
admitted AM radios along the line were bothered, he hasn't learned about 
ham and VHF communications, but if I can keep up on the project, I just 
might educate him at some Iowa Utilities Board hearing in the future.

73, Jerry, K0CQ
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