Utility
power issues at the Northern Utah WebSDR and surrounding communities For
reasons not (yet)
known to us, the electrical power at the WebSDR site and in surrounding
communities has been very
"dirty" for the past several weeks - with wild voltage fluctuations,
particularly during inclement weather.
In the past weeks the power fluctuations have destroyed a UPS (Uninterruptible Power System)
- likely with overvoltage - and have damaged other equipment, including
a power supply used for part of the RF infrastructure at the WebSDR
and at a nearby industrial site, industrial motor speed controls and
power supplies suffered damage, resulting in loss of production and
very expensive down time and damage.
What is happening?
At times, we are seeing our nominally 120-volt mains voltage exceed 140
volts - and this does not include the frequent excursions
below 90
volts: A primary fuse on a power transformer on some of the
gear was shattered by one
of these excursions indicating that a voltage far higher than the
observed
140+ volts that were seen. At a nearby site in town, a 120
volt
line was seen to exceed 180
volts for seconds at at time, giving a clue as to how
bad things might be getting when we aren't watching!
To be fair, our power comes from a service that is considered to be
"agricultural and industrial" which means that a waiver was signed with
the power company to indemnify them of equipment damage (either that or we don't
get any power from them!)
but it seems that something has recently changed in the infrastructure
and the problem is far worse than it had been in the past two years of
operation. We do
expect the situation to improve in the next few months, but the fact
remains that our power feed is at the "end" of a rather long
transmission line and will ALWAYS
be subject to voltage fluctuations and transients.
(Before you ask:
We've considered solar - but for the $5000-$8000 that it
would
cost - plus the running cost of maintaining/buying batteries - we can
buy a lot
of replacement equipment!)
What we are
planning to do:
Clearly, consumer-grade UPSs are NOT
able to handle these issues (we
are currently on our 4th UPS in two years!) so we are
looking at taking a different approach - one similar to large,
commercial/industrial "online" UPSs, which is:
Obtain two (for
redundancy)40-50
amp 24 volt "wide range" power supplies. These are the
power supplies rated for operation from 90 through 240 volts, designed
to be used anywhere in the world. Samlex has a number of
units
that are known to be fairly reliable and would fit the bill.
Use these to float a 24 volt battery bank. (We already have the batteries.)
Obtain a 1000-1500 VA sine-wave inverter and use that to
power
the critical gear. Again, Samlex America has 1000-1500VA sine
wave inverters that would fit the bill.
The power supplies and inverter will need to be placed in a
large
metal box to provide appropriate input/output filtering to prevent its
switching converters from causing interference: This is a
receive site, after all!
"What about a Sola regulator?" One option we have considered is a 1000-1500
VA
ferroresonant transformer such as the venerable Sola. While
this
would be an excellent option (they
are self-regulating and nearly indestructible)
they have the distinct disadvantage of being very
inefficient unless operated very close to their maximum rating:
A
1000 VA Sola run at half its ratings will consume a significant portion
of its rated power just
sitting there, doing nothing, and radiate quite a bit of heat in the
process. Because of limited ability to reduce summer heat (there is no air conditioning of
the server room, which can reach 130F) and the fact that
there's a power bill to consider, we are unlikely to implement a Sola
regulator.
"Why don't you use "wide range" power supplies for everything?"
These days "wide range" power supplies are
available,
capable of taking everything from about 90 to 250 volts AC - and most
of our gear uses them - but this still doesn't help us when the power
goes out - we still need a UPS that will
handle our "dirty" power.
"Why don't you use a surge protector?" While using a surge protection might seem like
a good idea, these devices are actually a liability:
When these devices fail, they short out, often destroying
themselves - but since they are considered to be "disposable" item,
this is part of their design. Clearly, we don't need to have
such
devices incinerate themselves on a regular basis.
It's worth noting that many communications sites - particularly those
on mountain tops - have banned
surge protectors as they have tired of racks of gear being knocked
offline by these devices after a heavy thunderstorm and filling the
equipment rooms full of the smell of burnt components!
We do
have an industrial L/C line filter that probably works better than a
surge protector in most cases - but it will happily filter 140 volts
applied to it, but will not protect the gear from that type of excess
voltage.
What you
can do: We are looking for high-quality 24 volt
supplies in the
40-50 amp range - preferably with active power factor correction -
that can handle 90-240 operating volts and a good-quality 24 volt
1000-1500 VA sine wave inverter. While there are many such
things
to be found on Ebay, unless they bear a known-good brand name, most are
of poor quality and durability.
If you are aware of a UPS that can take a 90-240 volt input range and
output a consistent 120 volts, please let us know.
If you don't have some gear that you might think work, you can still
help us out by donating - Go to our "Donate" page to find out
how.
Remember: We do
NOT need another "home" UPS:
Again, we cannot
use a standard consumer-grade "120 volt" UPS of the type typically
marketed for
home use: Three
of these units have already been damaged/destroyed - likely by excess
voltage - and there's no reason to believe that throwing another one at
the problem will help.
"I have
something that might work - or I'd like to donate some $$$ - how do I
contact you?
Again, if you
don't have some gear that you might think work but would like to help
you can still help us out by donating - Go to our "Donate" page to
find out how.
If you believe that you might have suitable gear on hand please contact
us as sdrinfo@sdrutah.org
and let us know what you have so we can determine if it will
help.
Thank you for your support. Additional information:
For technical information about this WebSDR system, go to
the technical
info
page(link).
For the latest news about this system, visit the latest
news page (link).
For answers to possible questions, visit the FAQ
page (link).
For more information about the WebSDR project in general -
including information about other WebSDR servers worldwide and
additional technical information - go to http://www.websdr.org
