Pomona electric plant, oil insulators originally proposed


Publication: The New York Times

New York, NY, United States
vol. 44, no. 13,731, p. 20, col. 1-3

Power Brought from San Antonio

Cañon, Thirty Miles Away.


When the Plant Was Installed, in 1891,

Little Practical Work Had Been Done in

This Direction — Its Success.


POMONA, Cal., Aug. 24. — This town is famous for many things, but for nothing is it better known than for the fact that it receives its supply of electricity for commercial purposes from a plant at San Antonio Cañon, thirty miles away - an electric power transmission ten miles longer than that of Niagara, and in some respects the most remarkable In the world.

Pomona is in so many ways typical of the new order of progress that has set in in Southern California that it deserves a moment's attention in passing. It is the boast of this little valley town of some 6,000 inhabitants that, agriculturally, it is the greatest all-around producer in the world. It is "the home of the orange, the olive, and the vine," and of an extensive array of other semi-tropical fruits, and many northern deciduous fruits as well. Its people maintain that there is a greater diversity of fruits produced commercially in and about Pomona than at any other point in Southern California. Its orchards produce annually about 2,500 tons of apricots, 1,000 tons of peaches, and nearly 1,000 tons each of prunes and grapes, while pears and nectarines are grown to a less extent. The State looks largely to Pomona for its supply of young olive trees of the best varieties.

Besides the fruit interests, the community has along its southern boundaries, a belt of moist land which, without irrigation, produces as regular crops 10 tons of alfalfa hay, 100 bushels of corn, and from 12 to 20 tons of beets to the acre. It is this comprehensiveness of producing energy that makes Pomona illustrative of the best possibilities of Southern California. To the tourist it is a paradise. Its views of mountain and valley are exquisite. Sitting on its hotel porches in genial sunshine, with the snow-capped mountains towering 10,000 feet above, the visitor is fascinated by the contrast between the icy peaks and the semi-tropical fertility around him.


Distributing Station/Electric Power Plant, San Antonio Canon, Cal.
Distributing Station
Electric Power Plant, San Antonio Canon, Cal.


The electric current is distributed throughout the town from a sub-station of the power company. San Antonio Canon is one of the most frequented Summer camping grounds in Southern California, and the scenery combining massive cliffs and desert-like stretches and groves of maples, sycamore, and oaks or manzanita, mountain mahogany and pine, through which the bright waters of the restless river flash every now and again along the winding path, is famous even in this picturesque country.

The San Antonio Light and Power Company, the plucky corporation that undertook single-handed, to demonstrate for the first time in electrical annals that a commercial transmission of electricity over a thirty - mile wire was feasible, was organized in 1891, with a capital stock of $240,000, for the purpose of utilizing the water power of San Antonio Cañon. The promoter, of the enterprise was C. G. Baldwin, President of Pomona College. He acquired from the Pomona Land and Water Company the option of the water rights for power purposes. After considering what would be the best way of carrying out his Ideas. Mr. Baldwin became convinced that electricity was the only thing for the purpose. What he wanted was something that would afford him light, heat, and power without the need of using fuel, which in this neighborhood is very expensive. Having decided on the electrical transmission of the power, Mr. Baldwin intrusted the preparation of the plans to A. W. Decker, the electrical engineer of the company, and A. W. Burt became Secretary and General Manager.

It must be remembered that those were the early days of long-distance transmission, and comparatively little original work had been done. Virtually, Lauffen was the only transmission that could in any way serve as a model for a practical scheme. The Lauffen - Frankfort circuits were 110 miles long, but the power transmitted was small and since then the work, which was purely experimental, has been dropped. It was never on a commercial basis, but was carried through by public subscription, the 1st being headed by the Emperor of Germany himself. The San Antonio Company had a scheme of a very different order to engineer, and was under the serious disadvantage of extreme distance from the manufacturing centres to which it had to look for new and entirely novel apparatus.

Almost sixteen miles due north of Pomona is the point on the San Antonio River where the melted snow and warm rains of the mountain were intercepted and put into harness. Gorge and waterfall combine to make the region picturesque, but the interest for the engineer lies in the tunnel excavated through the ridge at the lower end of the valley. This tunnel is l,320 feet long, and draws off the water by means of a canal. Where the tunnel emerges into sunlight, on the hither side of the ridge, it is met by a pipe line, which extends down the mountain slope in full view, for all the world like an elongated and stiffened boa constrictor.

This pipe line, plunging downward to the power house, gives a fall of no leas than 395 feet in a length of 2,000 feet. The pipe consists of 800 feet of 24- inch and 1,400 feet of 30-inch diameter, and the various sections range in thickness from No. 10 up to No. 6 steel. The capacity represents just about 1,000 horse power, at 390 feet effective head, assuming a wheel efficiency of 85 per cent. Special precautions were taken against rust and leakage, and also to protect the pipe from the great changes in temperature that occur in the mountains between the blazing heat of midday and the cool stillness of the night. Other measures were necessary to protect the pipe from shock by sudden increase of pressure There is a 24-inch gate valve at the lower end of the pipe. as well as a relief valve, and the water is emptied into a steel receiver. 20 feet long and 43 inches inside diameter. This large receiver avoids loss in head due to eddies in it, and prevents air being drawn into the discharge pipes.


Outlet of Tunnel./Electric Power Plant, San Antonio Canon, Cal.
Outlet of Tunnel.
Electric Power Plant, San Antonio Canon, Cal.


The massive power house is a splendid example of solid construction, equal to any emergency of atmospheric disturbance, or any torrent raging down the valleys, which range upward toward the summit of the mountain. It sits in a hollow scooped out of the hard mountain side, and its foundations are kin with the eternal bedrock beneath them. The walls are of the toughest concrete, six feet at base and two feet at the top. The location was, of course, determined by the purpose securing the maximum fall in the minimum distance. Here, at an actual difference in level between the mouth of the tunnel and the floor of the power house of 412 feet, the water is discharged upon a double-nozzle waterwheel of a well-known California type, the stream impinging upon the cup lips of the series of buckets ranged radially around the circumference of the wheel. In one instance, wheels of this form for generating electricity are used under a head of 1,700 feet, the installation being that in the Chollar Mine on the Comstock lode.

A description of the waterwheel mechanism in the San Antonio power house will be of interest. The differential governor consists of four mitre wheels geared together. Two of them are loose on the same shaft and driven by pulleys working in opposite directions — the motion of these two wheels being communicated to the wheels placed between them — turning loosely on a crosshead. One of the pulleys is driven by an independent motor, running at a constant speed. The other pulley is connected with the waterwheel shaft, either directly or by means of a countershaft. When the waterwheel is running at its proper speed, the revolutions of both governor pulleys are the same, although running in opposite directions, and the crosshead on the shaft is at rest. When any variation in the speed of the waterwheel occurs, either above or below the normal, the change in speed will cause the two wheels on the crosshead to turn the shaft, which communicates the motion by means of a pinion and quadrant to the rock shaft, operating by connecting levers either deflecting nozzles or balanced valves, and thus controlling the flow of water on the wheel. In general practice, a small water motor is used to drive the constant-speed pulley; but in the San Antonio plant it is run from the separately driven "exciter" shaft, the "exciter" being coupled direct to an independent thirteen-inch wheel. The governor is also provided with an adjustable automatic stop, which so limits its action on the deflecting nozzle or valve as to throw it out of gear in case of necessity. The need of such provision against accident is evident, as it will readily be understood that if the jet strikes the centre of the bucket squarely, and the speed is still slow, the governor will still attempt to raise the nozzle. This will not increase the speed, as the jet is at the point of maximum effort. The nozzle, therefore, strikes a stop to prevent further raising, and, should the governor continue to act, an accident would ensue. This is provided against by the automatic stop.


Power House/San Antonio Canon, Cal.
Power House
San Antonio Canon, Cal.


The station was built to accommodate four 120-kilowatt, 7,200 alternation 12-pole single-phase alternators, with their full complement of raising transformers and switchboard apparatus, and two exciters. The first installation consisted of one generator, with one 90-ampere, 125-volt, an exciter, capable of exciting the four alternators, and of 120-kilowatt capacity of oil transformers in 21 units of 6 kilowatts, one of those units being kept as reserve. It may be explained in passing that the kilowatt, or 1,000 watts, is an electrical unit the value of which is about one and a third horse power, 740 watts being the exact equivalent of a horse power. Last your another 12"-kilowatt generator, with adequate transformers, was added. Each transformer is contained in a cast iron box provided with vertical outside ribs, which serve to stiffen it, and also to cool the oil with which the box is filled and which entirely covers the transformer. The box is covered by a cast iron lid, which has conducting and radiating ribs both outside and in, the inner ones dipping into the oil at its hottest part and helping to cool it. The oil when heated rises through open spaces around the coils, and spreads out in all directions, guided by the ribs on the lids. It then sinks slowly down between the core and the sides of the box, thus having ample opportunity to become cooled.

Each box is provided at the bottom with a petcock by which to draw off the bottom layer of oil should it become too thick for evaporation. It also has an oil gauge to show whether the tops of the coils are completely covered, without having to raise the lid. The boxes are supported upon a substantial timber frame, upon the top of which two iron bands serve incidentally to protect the wood, but chiefly to connect metallically the boxes to each other and to the earth. In order to dissipate the static charge received by the boxes, which is very unpleasant. The core of the transformer is connected to the box by a copper strip fastened around a block of wood upon which the core rests in the box; and, to provide against the danger which would result from accidental connection between the primary and secondary coils, an insulated sheet of copper is placed between the latter and close to the dynamo coil, and is connected to the core by a tongue which is stuck between the plates. The oil here mentioned is employed as an insulator. It has great virtue in confining currents of high potential to their proper paths, a spark finding it extremely difficult to pass through it from adjacent wires. The current is generated in the alternators above spoken of at a potential of 1,000 volts, and being passed through these transformers is at once raised or intensified to the really enormous pressure of 10,000 volts, at which speed it starts out from the power house for its work, nearly thirty miles away.

It is needless to say that great care, was taken with the pole line, or running track, for this lightning sprinter. There are, in reality, two transmission lines, one 13 3/4 miles to Pomona, and the other 28 ¾ miles to San Bernardino. Each is built of No. 7 B. & S. gauge of copper wire. At first it was intended to use insulators with oil in their curled rims, but the builders of the line fell back on a double-petticoat, flint glass form, which has answered admirably. As a matter of fact, the oil would not last long in the blistering sun of that region. The poles are Santa Cruz redwood, 23 feet long, and set 125 feet apart.

In the substations at Pomona and San Bernardino, to which the current is delivered for local commercial use, the form of transformer is identical with that found at the station. The method of connecting up is also similar, excepting, of course, that the primaries and secondaries are respectively reversed, in order to effect stepdown transformation. A potential of 9,500 volts is delivered at Pomona, while at San Bernardino, the present loss in transmission is 10 per cent. The potential maintained on city lines is l,000 volts.

As might be expected in such an exceptional installation, several interesting and noteworthy experiences have been met with. Among these may be mentioned the violent induction in the Pomona circuit when the San Bernardino circuit alone is operated, the Incessant oscillation of the substation voltmeter needles through a considerable arc, while the lamps remain unaffected, the pleasant humming of the current, that has served as a guide to the station attendants; the static charges on the line, due to atmospheric electricity, etc. Observations made on the Pomona line during hot, dry, and cloudless weather, prove the line, for example, to be heavily charged by the mere wind; and the rate in which the line was electrified in this way was actually governed by the rate at which the wind was blowing. This curious method of obtaining electricity from wind power may have nothing practical in it, but it is one of those side openings or suggestions of which electrical investigation to-day is so full. It is also noted that the substances blown against the wires at such times, dust, etc., give up their charges to it no less than the air. Of recondite electrical phenomena connected with "capacity," "induction," "impedance," "condenser effect," &c., there are not a few occurring incessantly; but they do not hinder the plant from being a thorough success in every respect.

The substations at Pomona and San Bernardino are small brick buildings, one story high, with flat, tin roofs, and numerous windows. The Pomona building contains two rooms connected by a door near the switchboard. The front room is used as the office of the company, and the other as a transformer room. The 10,000-volt circuit enters over the door, and is connected directly to the bank of lowering transformers, no switches or other appliances being used on the high-tension lines either there or at San Bernardino. The switchboard appliances are a regulator, marble fuse-blocks, with double plugs and fuses; a jaw-switch, 160-ampere ammeter, compensating voltmeter, compensator, and converter. The San Bernardino station is longer than that at Pomona, and is not divided by a wall. The transformers are placed in a row along a side wall, and along part of the end wall next the switchboard. The transformers near the switchboard heat the most. This is probably due to the slight drop in wiring between them and the more distant converters.

During the first year of operation a little new oil was put into the converters about every four months to make up for that evaporated, but none of the old oil was drawn off. The switchboard apparatus is like that at Pomona. The two stations are doing a regular and increasing commercial business, and yet the work has already reduced itself to mere routine to such an extent that there are now no substation attendants at all, either at Pomona or at San Bernardino, to deal out the 160 or 200 horse power for local consumption. Each station is fed by its own independent circuit from the power house, where the one engineer is in charge, after the solitary fashion of a lighthouse keeper; and where, by a touch he determines in an instant conditions in places so far away that it would take him six or seven weary hours to reach them in person.

A striking test, bearing on the work at Niagara, was made in May, 1893 when the Pomona line was connected in series with the San Bernardino line, making- a continuous circuit of 85 miles over a distance of 42 ½ miles, and when 100 horse power was sent over en bloc. This was the longest and largest transmission of power electrically since the famous Lauffen-Frankfurt trials, and it is conspicuous as being the only one on a commercial line of any such length. It was entirely successful. It may be pointed out also that this same current carried 30 miles will not only run lights and small stationary motors, but can be manipulated also as to operate street railway systems or even steam railway services. Work of this kind is already being done in several places, and at this moment there is not a single valid reason, except that of the initial cost of the change, why the New-York Central should not operate electrically every one of its trains within at least 30 miles of Niagara Falls, dispensing once and far all with the grime and smoke of the steam locomotive. Many changes of this nature are certainly imminent when we see examples like those of Pomona and San Bernardino.


Keywords:Power Transmission : Pomona : CD 244
Researcher notes:The "double-petticoat, flint glass insulators" are CD 244's nicknamed "The Pomona"
Supplemental information: 
Researcher:Bob Stahr
Date completed:March 30, 2008 by: Bob Stahr;