IEEE Power & Energy Magazine - January/February 2014 - 95

5,000

35″

4,500
4,000

Power Losses (W)

3,500

22″
52″

3,000
Loss on Circuit with Wires at
Different Distances. Frequency
60 cycles, Slotted Armature,
Weston Wattmeter, Wires 15, 22,
35, and 52 in Apart.

2,500
2,000

15″

figure 18. A view of one of the transmission lines crossing the mountain
ridge above the timber line. It is easy
to appreciate the line construction
and maintenance challenges confronting the company (photo courtesy
of the Fort Lewis College Center for
Southwest Studies).

1,500
1,000
500

8 12 16 20 24 28 32 36 40 44 48 52 56 60
Thousands of Volts

figure 17. A graph showing power losses (watts) at different voltages and horizontal conductor spacing (image courtesy of Alan E. Drew).

Corona discharges occurring as voltages increased were observed and noted. Mershon concluded that there was
no advantage to porcelain over glass,
unless it was a slight increase in mechanical strength. He summarized that
glass insulators were cheaper, lighter,
more easily tested and less likely to be
shot at than porcelain. His theory on
gunshot vandalism was that the white
porcelain provided a more tempting
target than the green glass. Different
lightning arresters and choke coils at
line terminals were also the subject of
experimentation.
Up to that point, almost all theories of transmission line operation
had been predicated upon studies with
minimum testing conducted in laboratories. Based on these new tests, Mershon concluded that 40,000 V was a
perfectly conservative operating voltage to be utilized on properly designed
lines in the future. This clearly led to
january/february 2014

elevation of transmission voltages, as
the Telluride Power Company would
later construct a line in Utah operated
at-you guessed it-40,000 V.

System Expansion
The success of the initial installation at
the Ames plant led to expansion of the
system to other fuel-depressed mines
in the Telluride area. The Telluride
Power Company was officially established around 1895, with L.L. Nunn as
general manager and his brother Paul
N. Nunn as chief engineer. Westinghouse had gone on to develop the Tesla
system, which vastly improved the
efficiency of electric power for mining
with a three-phase system of generators, transformers, and motors.
In 1896, Nunn had the Ames
plant completely rebuilt with a new
three-phase system supplied by a pair of
two-phase generators directly connected
to the Pelton-style water wheels, which

were supplied by an increased flow
of water from a newly designed storage dam and penstock system. Twelve
100-kW generator step-up transformers
were connected to convert the generated
two-phase power to three-phase power,
elevating voltage to 10,000 V for transmission to various mines.
With a transmission voltage of
10,000 V, the Telluride Power Company now had the potential to serve
mines upwards of 20 mi (32.2 km)
from Ames. A majority of these mines
were located to the northeast of Telluride, in the high mountain areas. This
formidable obstacle did not stop these
pioneers as they proceeded to extend
lines to several mines, including the
famous Camp Bird Mine.
Extending the system to mines in
this area meant the lines would have to
traverse mountains at elevations up to
13,000 ft (3,962 m), where severe weather (including snowstorms, avalanches,
winds and ice) was commonplace. As
plans for expansion were in progress, it
became obvious that, to avoid damage
from heavy snows and avalanches, longspan construction eliminating the need
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