TELECOM Digest OnLine - Sorted: Various Power Issues, was: Gas Refrigerator (was 25 Hz Power)

Various Power Issues, was: Gas Refrigerator (was 25 Hz Power)

Danny Burstein (
Sat, 18 Mar 2006 02:00:51 UTC

In <> writes:
[ misc snips ]

> T wrote:

>> Unfortunately for me I've never heard a live electromechanical
>> switch.

> Telephone switches have a distinctive sound. The clicks and clacks are
> very sharp and distinctive.

The closest you'll find to this nowadays is in older elevators.

Prior to 1980 or so the controllers on automatic (as opposed to
manned) elevators used bunches of Big and Loud relays.

Next time you get into one, especially in older buildings, listen for
the clicekty-click-CLANG-clap-click-SNAP as they determine the fate of
that little box you're riding.

(These are, of course, getting phased out by electronic controls, but
since they last just about forever and it's still quite expensive to
replace them, many of the older ones are still around).

> Places with critical functions likes hospitals and nursing homes have
> backup power generators. They are tested every so often. Sometimes
> power failures result from failure of the switchgear to transition
> from one source to another. One of my employer's location had a
> backup source and they did a test; they were out of commission the
> whole day due to failures of the control circuitry.

A hospital complex with which I'm acquainted in NYC had an executive
director who took emergency planning seriously.

( details slightly changed both due to memory fade and to protect the

Early one afternoon, when they were throwing a "nurses and EMS and
local police/fire thank you" day, this director walked into the
basement and bumped into a Big Red Switch, knocking out all the
primary power. And then watched what happened.

( She chose this day deliberately since there would be plenty of extra
personnel [most of whom would still be sober this early] around just
in case emergency power didn't kick in the way it was supposed to...)

Most stuff did ok, but lots and lots of issues showed up.

> failure. I believe it was caused by surges in an Ohio system that
> rippled to other systems. I don't know if there is a protection
> against such "rippling". That's why I wish there were some kind of
> "buffers".

There's a simple (well, not quite so simple ...) way of significantly
reducing the risks of the specific problems related to the recent
blackout. It's called using High Voltage Direct Current (HVDC)
transmission lines instead of the legacy AC ones.

A hefty percentage of new circuits are, in fact, using direct current,
and older ones are often switched over when they're upgraded/replaced.

(No doubt we'll find other failure modes ...)
Knowledge may be power, but communications is the key
[to foil spammers, my address has been double rot-13 encoded]

Post Followup Article Use your browser's quoting feature to quote article into reply
Go to Next message: John Stahl: "In NY, ILEC Wireline Rates May Go Up Due to Competition!"
Go to Previous message: Paul J. Gough: "Madness: Net Hit With Record Traffic Flow"
TELECOM Digest: Home Page