Funny... Over the last 3 years we've had problems due to no neutral from
the pole into the house. The last time we had very few appliances/lights,
etc. powered on. One floor fan sounded like a jet plane. I measured the
voltage across one side and it shot up to 170 VAC when the refrigerator
compressor started and loaded down the other side. Like a shot I pulled the
main switchs to my two distribution panels.
Both times the culprit was a squirrel. It seems those critters like to eat
aluminum wires but they won't eat copper. Our power company said that if I
could find it, they would replace the run from the pole to my house with
copper wire. The trouble is that I can't find hard drawn copper to use in a
triplex. If anyone knows where I might find it, please let me know.
For now, if you have voltage fluctuations be very alert to the possibility
of squirrels...
Jerry, I've considered making up a little circuit which will rectify the
voltage from both sides of the line and then take those two outputs to a
voltmeter. If there is an imbalance, the meter would show it right away.
Is there a more common method to do this?
73, Mike -N4NT-
----- Original Message -----
From: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
To: <tentec@contesting.com>
Sent: Friday, October 24, 2003 10:31 AM
Subject: Re: [TenTec] Latest BPL events...
> Jason W0JSB:
>
> Your residential distribution is single phase. Much of the ground wire
> current is in the earth.
>
> The 75 stands for 75 KVA transformer rating. The primary voltage might
> be 4160, might be 2400, might be 7200, might be 7500, might be 14.4 KV,
> might be 15 KV. Probably line to neutral. 220 is still single phase. One
> wire has 120 volts to ground, the other wire has 120 volts phase angle
> 180 degrees to ground, so between them there's 240 volts.
>
> If your 120 volt loads are wandering about, its likely you have a poor
> neutral connection and are experiencing neutral shift from changing
> (like refrigerator and furnace) 120 volts. That's not a good sign. The
> bad connection in the neutral can be in your main panel, the wires from
> the pole to your house (overhead or underground, more often a problem
> with buried aluminum wires) or out on the pole. On the pole its a
> utility problem (and may show at your neighbor's as their changing loads
> contribute to the neutral shift), but the service drop and main panel in
> the house are your problem. A good electrician can find the problem and
> fix it or get it fixed. It will get worse and start damaging stuff from
> high voltage, lamps first, electronics later.
>
> Signaling on the power line using audio tones has been going on for at
> least 75 years. Sometimes its used to control fixed loads for peak
> reduction or to change capacitors correcting system power factor.
>
> My graduate work was applying communications in the audio range to power
> lines. Some places when checking for background level, I found volts of
> trash from SCR operated induction heaters.
>
> Noises from arcing switches should show up with strong 60 Hz spectral
> components because the arcing only happens near the peaks of the line
> voltage. That hash could be a poorly RFI protected aquarium thermostat.
> Their switches are notorious for slow opening and opening a tiny gap to
> arc. The heat of the arc forces them to open better so they get quiet.
> If that aquarium heater is on the same side of the transformer as your
> transmitter power supply, transmitting may be lowering the line voltage
> to cause the heating to be a little slower.
>
> Then it could be a bad door bell transformer with a thermal protector
> that opens at intervals making hash as it opens.
>
> And those noise sources could be anywhere in a couple blocks. But as it
> seems to be voltage sensitive, it may be in your house with the neutral
> shift.
>
> 73, Jerry, K0CQ
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