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Michael Moroney

writes:

In alt.engineering.electrical Michael Moroney wrote:

| If these tap changers are rather expensive, I'm wondering what those
| pole pig "voltage regulators" I mentioned are. I thought they were just
| tapped autotransformers.

Sounds like they may be more of a voltage selector.

Probably.

One set of transformers I saw once had a voltage selector which also revealed
the voltage to me. Even those these huge things were well guarded behind a
chainlink fence with barbed wire on top, I could clearly read the instructions
on the voltage taps. It listed 5 or 6 different voltages in the 4160 volt
range (I believe that was a middle one). The secondaries were a thick bundle
of insulated wires not on insulator standoffs, so obviously LV, possibly 480V
or 208V. These were 3 single tank transformers in roughly the design style
of a pole pig (round tank) with a control panel on them with the tap control
and some gauge I guessed may be temperature (but I could not see it clear
enough at the distance I was at to be sure). The instructions did indicate
that the transformer must be de-energized (not just unloaded) when making the
change. So I'm guessing they were just to compensate for variations in the
delivered voltage. These transformers were about 1 meter wide and 2.5 meters
high, each (3 of them). I did not see any reference to a kVA rating. They
were also very old looking (pre-WWII). They were humming.

Interesting. Around here I see control boxes on the pole-mounted ones.
Maybe they have something to read. (I know some read SIEMENS in large
letters on some of them, apparently the manufacturer)

Long ago, during one of the past "oil crises" (1973 or 1978 or so) they
proposed cutting back the voltage delievered to one's home by 5-10% from
the normal voltage, a "brownout", "to save energy". I once wondered how
they may have done that, assuming any automated regulating equipment was
hardwired to provide 13.8kV or whatever, and that setting couldn't easily
be changed. Also, any automated regulators downstream would try to
compensate for the lower supply and raise their output voltage, so all
regulators would have to be adjusted. But if was done manually, for
equipment not tied to a particular voltage, they could do it on a
substation-by-substation basis, and ones "downstream" could have been
left alone.