Publication: Electrical World
New York, NY, United States
Hydro-Electric Development in Maine.
At a meeting of the Massachusetts Street Railway Association held in Boston on Feb. 10, Mr. John R. Graham, president of the Bangor Railway & Electric Company, Bangor, Maine, read a paper entitled "The Electrification of a Part of the State of Maine." In the course of his address special consideration was paid to the recent important hydro-electric developments in Maine.
The history of the Bar Harbor & Union River Power Company is typical of the usual course of hydro-electric developments in Maine. The project of combining the water powers in use on the Union River, at Ellsworth, Maine, had been in mind for about 30 years. The originator of the plan finally succeeded in interesting a fellow townsman sufficiently to employ an engineer to investigate the feasibility of the project. The report was favorable, and plans were drawn for the installation. As the Union River is in a somewhat remote portion of the country, had never been mapped by the government and was so little known that the numerous engineers who investigated the project for various capitalists could not be convinced that sufficient power was available, it was difficult to secure the money needed to develop the work. Finally, in 1907, the Bangor Railway & Electric Company interests decided to buy the property. Although the project was condemned by many engineers, it is a fact that during the past year, when water was the lowest on record, the Ellsworth plant was about the only plant in Maine which had an abundant supply of water. With the enlistment of capital the third step was completed, but much remained to be done. Detailed plans were to he drawn, contracts for construction were to be let, property rights to he obtained, highways to be relocated, buildings were to be moved from the area to be flooded, and new bridges had to be erected. Actual construction was begun on March 1, 1907. The first three months were occupied in removing sawmills with their accompanying dams, which had occupied the site of the plant for many years, installing the contractors' plant necessary for the rapid and economical construction of the work, and in blasting out the rock required to be removed from the tailrace and canal. On June 9, 1907, the actual construction of the dam was begun, and the work proceeded so rapidly that on Jan. 1, 1908, the plant was practically completed.
The Ellsworth dam is located between two granite bluffs rising 100 ft. above the bed of the river. The dam is of the Ambursen steel and concrete construction, rising 71 ft. above the river bed, and is probably the highest dam in New England. The power house is built of concrete blocks. At one side of the building is a heavy concrete wall forming one side of a canal, the latter having been blasted out of a solid ledge and serving as a forebay from which the water is drawn through penstocks 8 ft. in diameter, which carry the water to the turbines located 60 ft. below. At intervals of 15 ft. in the interior of the dam, which is hollow, buttresses of concrete were built parallel to the flow of the stream. These buttresses were built A-shaped, being about 100 ft. wide at the base and from 60 ft. to 71 ft. high. They vary from 16 in. in thickness at the top to 36 in. at the base, and are stiffened by concrete beams reinforced by steel bars placed at right angles to the flow of the stream. These buttresses form the supports of a deck or slab of reinforced concrete extending from buttress to buttress entirely across the stream. The deck ranges from 36 in. in thickness at the bottom to 18 in. near the crest. This is the highest dam of this type that has so far been built, and is to all indications thoroughly satisfactory.
The Bar Harbor company has secured practically the control of the whole river with its water supply. The Union River drains a basin covering 525 sq. miles, included in which is a lake area of 40 sq. miles. The annual rainfall of the region is about 34 in. The average temperature is about 42 deg., and as the amount of evaporation is governed by the temperature, this low average is of great value, leaving as it does a large amount of water for the run-off. It is a fact that at no point except in North China does the isotherm of 42 deg. approach so near the equator. Within two miles of the present power station it is possible to construct another dam, thereby raising the present level of the river at that point by about is ft. and forming a reservoir which will impound 5,000,000,000 cu. ft. of water that can be used at the power plant at a head of 6o ft. This arrangement would insure about m000 hp continuously.
The present development is for 1500 kw. The power station contains two units; one consists of two S. Morgan Smith turbines rated at 1700 hp and directly connected on a horizontal shaft to a 1000-kw, 2300-volt, three-phase, 60-cycle General Electric alternator; the other consists of two turbines rated at 850 hp, driving a 500-kw generator. The e.m.f. is increased to 33,000 volts for the transmission of energy to Bar Harbor and Bangor. One of the novel futures of the work is that the transformers and all of the high-tension apparatus are placed in one of the hollow compartments of the dam, in what would otherwise be wasted space.
Energy is transmitted for operating the trolley cars of Bangor, both in passenger and freight service; street lighting in Bangor, Ellsworth and Bar Harbor, industrial service and pumping water for many communities. At Ellsworth, a town of 5000 inhabitants, the company lights the streets and houses, furnishes energy to several local industries, and owns and operates the local water supply system. The energy for the local service is transmitted at the generator voltage of 2300, the e.m.f. being decreased to 500 volts for the motor service and 105 volts for lighting.
The Bar Harbor transmission line is 21 miles long. Use is made of cedar poles placed partly on the highways and partly on private right of way purchased by the company. The three conductors are placed in the form of an equilateral triangle, with the apex on top of the pole, and the two lower wires near the opposite ends of a cross-arm 7 ft. long, the spacing of the wires being 4 ft The insulators are of brown porcelain, of the Locke type, having double petticoats; they are carried by steel pins covered with porcelain sleeves to guard against short-circuit from the conductors to the pin.
Use is made of six-strand aluminum wire which, thus far, has been very satisfactory. Aluminum as a conductor, in the company's experience, seems to have taken the place of copper perfectly and has the advantages of lower first cost and considerable decrease in the cost of erection.
It was necessary to cross an arm of the sea, called Mt. Desert Narrows, between Ellsworth and Bar Harbor. These are navigable waters and the government authorities required that the lowest wires should be at a minimum height of 125 ft. above mean tide. This action necessitated the erection of two steel towers 160 ft. high and about 900 ft. apart. These towers are erected on opposite shores, on concrete foundations, and carry three conductors of No. 2-0 hard-drawn copper, strung with a sag of 40 ft. at the center of the span. At the shore ends of the spans, and 400 ft. distant, the wires are dead-ended on steel poles 60 ft. high, these being strongly guyed with galvanized steel cables 3/4