TELECOM Digest OnLine - Sorted: Re: Keokuk Dam & 25Hz Power

Re: Keokuk Dam & 25Hz Power

Robert Bonomi (
Tue, 14 Mar 2006 03:25:14 -0000

In article <>, John McHarry
<> wrote:

> When I was young I was told that the dam at Keokuk, IA generated 25Hz
> power. Since construction was completed in 1913, this may well have
> been true.

I can confirm that the hydro at Keokuk was 25 Hz. into the 50s, residential
service (at least in part of the area) was still being delivered at 25Hz.
Caused problems for some consumer-grade gear where line transformers
'saturated', overheated, and burned out.
, overheated, and burned out.

> I was also told that the power was by then converted to 60Hz and fed
> into the grid.

That was a relatively _late_ change. Keokuk was isolated from the
grid for a long time.

> Whether I was told so, or figured out later, this must have been done
> with rotating machinery. I would guess, unless there is a cute hack I
> am unaware of, this would give a nasty waveform, but would probably be
> smoothed out by the rest of the grid.

Nope; no 'nastier' than any other 'motor generator' set.

Or any other generator driven by a rotating shaft, for that matter.

> The dam is still generating electricity, but the old generators and
> converters have probably long ago been replaced by native 60Hz
> generators.

The 25Hz facility was completely off-line and cold by the mid 70s.

If it has been re-activated, I'd agree it is virtually certain to be
using native 60Hz generators. The superior efficiency (and lower
maintenance) of modern gear vs the old stuff (generator and
motor-generator) would pay for the 'upgrade' in fairly short order.

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