[time-nuts] Line Voltage - USA
herbert3 at centurytel.net
Mon Jan 2 16:37:37 EST 2017
Another one of those fascinating "threads!" I have lived through the claimed 110, 117 and 120 volt periods and have been apparently lucky enough to not have suffered any device damage. At present I live on a hill and do worry about lightning strikes to ham radio antennas. The last time I counted I had over 20 standard eight foot plated ground rods driven at various places and the entrance point of these antennas to the house is protected by an additional 6 rods. All wiring in the house is either thin wall tubing or other armored cable. Thus I effectively have building perimeter protection as well. All grounds are tied together along with the power neutral. I also have an automatic transfer backup alternator with separate ground also tied to the entire system. I do disconnect antennas during storm threats but in the past thirty years have yet to have any "over voltage" damage. From time to time I do check the line voltage but not with any NBS standard voltmeter and have found that it does "drift" between 120 and 126 which I feel is outstanding given the general circumstances which include being several miles from the distribution point along a rural road and the possibility of some fairly demanding motor starting loads that I deal with. My input panel is over 200 ft. from the farmer's electric co-op transformer which I used to share with two neighbors but now I have "my own." Yes, I do have lightning rod protection.
----- Original Message -----
From: Poul-Henning Kamp <phk at phk.freebsd.dk>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>, Chuck Harris <cfharris at erols.com>
Sent: Mon, 02 Jan 2017 12:55:58 -0500 (EST)
Subject: Re: [time-nuts] Line Voltage - USA
In message <586A8B40.4050806 at erols.com>, Chuck Harris writes:
>Back in the dark ages of ~220V electrical distribution systems in
>Europe, the reaping due to unintentional grounding of a ~220V wire
>was so common and extreme, whole house ground fault interrupters
>were mandated for all residential/small business power systems
Close, but no cigar.
The main problem was that in many countries outlets did not have a
protective ground terminal.
That meant that an internal fault in your appliance had a 50/50
chance of lighting up some exterior metal part you could touch.
The "obvious solution" isn't obvious in countries where the geography
does not allow you to obtain proper "protective ground". Norway being a
But even countries with the "obvious solution" of protective ground
in all outlets saw problems, because it took 10-16 ampere misdirected
current to blow the fuse, and you can light most flameable stuff
with a lot less energy than that.
The "Residual Current Device" solved both problems.
RCD's even protect you from internal faults where proper protective
ground is not available, by providing neutral from "outside" the
RCD as PG in the installation. You'll still be (horribly!) exposed
of an accident in the distribution grid (or lightning!) fires up
the neutral, but that's simply life - or death - without a grounding
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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