Evening star. [volume] (Washington, D.C.) 1854-1972, 1894-08-22
The Proposed Plan to Utilize the
Great Falls Power.
HOW IT IS ACCOMPLISHED


man campag na, to q distributing station at
Porta Pia, on the outskirts of Rome. The
Great Falls of the Potomac, which are pro-
posed as the site Of the plant for the Dis
trict system, are fifteea miles from the
city, or three miles nearer .han the Roman
electric plant The present electric light
system Of Rome was established In July,
1892, and has been in successful operation
ever since. Mir. Jones says that Rome is
the first city in the world 10 be lighted by
electricity brought rom a long distance.
His report gives @ detailed description Of
the plant and apparatus. by which 1000
horse power Is transmitted a distance of
eighteen miles, together with a technical
account Of the switchboard at Tivoh and
the distributing board at Porta Pia.
The power Is generated at the fall Of the
river Teverone. or Anio, at Tivoli. The wa
ter has q total fall Of Ito meters, and Is
much more than sufficient for the transmits
sion Of electric energy 10 the Roman CAPT.
tai by the establishment of plant for an
alternating and highly potential current
with transformers. Separate chapters OF
the report are devoted to the power house
at TivOn where the current is produced, the
transforming and distributing station at
POria Pia and the setting up of the lights
in the city. Nine pipes are used in carrying
the water to as many turbines in the sta
ton house, where a fall Of { bout fifty me-
tiers is utilized.
Operating the Turbines.
Special arrangements are made for the
decantation of the water that drives the
governors Of the turbines. and for the auto
matte closing CT the necessary derivation
pipes leading from the main supply pipe.
The turbines are Of the Giraud type, with
horizontal and differential ayes. There are
three groups Of three machines each. Two
large turbines are coupled directly to two
Zipernowsky aiternators, and between them
is q small one that drives a direct current
dynamo that moves two lateral alternators.
This system is duplicated in the other tur-
bines. The principal turbines are of $50
horse power, and make 10 revolutions a
minute, normal speed. The water-wheel is
consists of a cylinder with six small holes
In the bottom and with five series of three
COCKS each in the top The small turbines
are OF nifty horse power and have normal
speed of 315 revolutions q minute.
The alternating current dynamos are d.
rectly coupled to the turbines by means Of
an electric joint. The machines, although
Of the usual Zypernowski type, develop a
difference of potential of more than 5000
volts, and require exceptional insulation.
The terminals of the high potential dyna-
mos are situated in the lower part of the
immature. They are mounted on separate
discs Of porcelain on two posts. one of ebon-
lite and the other of paraffined wood. The
plant can be divided into three sections,
each comprising two alternators and one
exeter. Consequently there are three
switch board Each groove incloses twelve
conductors-four conveying the primary
current Of two distinct alternators, and
four the respective exciting currents; two
conveying currents from the exciting dy-
ramos. and two others conveying the ex-
citing current Of the EXETER. This makes
three sets of twelve conductors each, repre-
scented on the switch board. They are COM
,l.,k-
switch board Is Of wood and is 2050 meters
long by $50 meters high. 1t stands sixty
centmeters from the wall, so that there is
ample space to keep clean the conductors
that run along its back.
Protection for the Wires.
The line Of transmission from TivoM to
Porta Pia is 24s5S meters in length 1t
follows the Roman aqueduct which runs
in a straight line between the two places
Where the line crosses the Rome-Sulmone
railroad and the telegraph wires. the poles
are high enough to leave the lowest cable
at $50 meters above the ground. A metal
lie net Is stretched between the poles and
extends across the railroad tracks to pre-
vent the cables from falling to the ground
In case Of accident. At this point the tele-
graph wires are underground. The same
precautions are taken at the points where
the line crosses the river Aino and the rail-
road near Porta Pia- About half way be-
tween Tivoli and Rome. at point known
as the Campannacce, q small stone house
has been erected which serves as quarters
for the men who watch the cables, as a
depot for stores, as point Of communica-
ton between the two extreme stations, as
center Of electric measurements and final
ly as the interrupting point of the line.
The eight cables composing the line pass
through an upper room In q tower that
surmounts this house and are there united
two and two. by means of mercury inter-
ruDterS- -Four wires of ha hnnoo
on the opposite side through four insulators
The supporting poles are made Of two dou-
BILE irons. meters high. The four COD
per cables that transmit the current are
held up by insulators. AS a rule each pole
carries eight insulators. with eight con-
ductors. and is $50 meters high. The mean
distance between the poles Is So meters,
except at railroad crossings and at the
river. There are 707 of these poles. The
four cables are respectively ESQ. $40, $40
and $50 meters above the ground. High
insulation has been obtained by the use Of
a well-devised porcelain insulator with oil
cup. The conductivity of the copper wire
was found by experiments to be 90 per cent
that Of chemically pure copper. The wires
are 2.6O nm. in diameter and each cable Is
composed Of nineteen such wires. At a
temperature Of o. the cable presents q mean
resistance Of $3.50 ohms.
Currents Of Varying Power.
The electric current generated at Tfvon is
received in a small building at Porta Pia,
where 1t is ingeniously transformed from a
high potential to a lesser potential. The
potential. however, is not less than 1900
volts. and feeds twelve concentric Siemens
cables. which run through the principal
streets Of the city of Rome. All the cleo
trio apparatus is placed on the ground floor
Of the building. and thirty-two transform
ers Of about $4,000 volts each are located In
one room. In another room are the distrib-
uting switches Of the currents, the auto
matte regulators and control. The DISPOSE
ton Of the apparatus is entirely subordinate
to the system Of plant to be supplied, and
circuits for arc lamps, as well as derivativc
circuits for use Of private parties, leave
this building. These circuits, in SERIES
have a constant intensity and a difference
Of potential. that varies with the number of
lamps lighted They are formed by concen-
trio Siemens cables Of 12x12 m.m in diane
ter, each of which is fed directly by the
secondary Of a transformer at this building
The plants of private parties in the city
that connect with the derivative circuits
are not fed directly by the 1900 volt cur
rent derived from the secondaries Of a spe-
cial battery Of transformers, but by that
current reduced to 80 or 100 volts by means
Of other transformers located near the place
Of consumption. The communication be-
tween these plants and Porta Pia is had by
means of other similar Siemens cables of
200 or 300 MN. in diameter. BY an In
genious mechanical arrangement, 1t Is pos