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EA-I. (G eorge W. Rathjens)

POWER PLANT DEVELOPMENT AND ELECTRICAL TRANSMISSION AND DISTRIBUTION SYSTEMS

       

CONTENTS

	Page
Hydroelectric Power	1
Transmission Lines	3
Electrical Distribution	4
Electrical Grounds	5
Bibliography	6

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EA-I. Rathjens: Power Plant Development

       

LIST OF FIGURES

		Page
Fig. 1	Precipitation, Fairbanks, Alaska 1904-1946. From records Fairbanks Station U.S. Weather Bureau	2-a
Fig. 2	Temperature, Fairbanks, Alaska 1904-1946. From records Fairbanks Station, U.S. Weather Bureau.	2-b
Fig. 4	Lifting forces from swelling of ground because of freezing	3-a
Fig. 5	Collars or muffs around pole to assist in preventing lifting of pole	4-a
Fig. 6	Lifting of pole because of freezing water at foot of pole	4-b
Fig. 7	Pole anchor in permafrost	4-c

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PHOTOGRAPHIC ILLUSTRATIONS

        With the manuscript of this article, the author submitted 4

photographs (Figs. 3, 8, 9 & 10) for possible use as illustrations.

because of the high cost of reproducing them as halftones in the printed

volume, only a small proportion of the photographs submitted by con–

tributors to Volume I, Encyclopedia Arctica , can be used, at most one or

two with each paper; in some cases none. The number and selection must

be determined later by the publisher and editors of Encyclopedia

Arctica . Meantime all photographs are being held at The Stefansson

Library.

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EA-I. (G. W. Rathjens) ✓

       

POWER PLANT DEVELOPMENT AND ELECTRICAL TRANSMISSION AND DISTRIBUTION SYSTEMS

        Since the problems of power development and electrical transmission and

distribution systems in the Arctic and Subarctic have much in common with

those in more temperate zones, no attempt will be made here to give a full

treatment to the problem, but rather only those phases peculiar to the

arctic and subarctic regions will be discussed.

        It is first of all to be emphasized that, in these regions, solutions to

problems will vary with local conditions to a much greater extent than is

general in more temperate zones. Much of the discussion in the article

“Construction for Placer-Mining Operations” is applicable to power plant

development and electrical transmission and distribution systems. Power plant

development as used in this article contemplates the generation of electrical

energy by one or more of the following methods: ( 1 ) hydraulic turbines and

the development of water power; ( 2 ) internal-combustion engines; and ( 3 )

steam turbines or steam engines (this is discussed in article “Analysis of

Design Factors for Power, Heating, Ventilating, and Refrigeration Systems

for Alaska”).

       

Hydroelectric Power

        In the development of hydroelectric power, the extent of stream flow

which it is practical to develop requires careful and special study in each

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EA-I. Rathjens: Power Plant Development

locality. The exposure of an arctic river and storage or pondage area

are extremely important. Much water will have to be stored as ice and the

exposure of such masses of ice will largely determine whether or not the

water so stored will be available when required. The writer has in many

instances seen flowers blooming on one hillside of a valley while ice was

still present in relatively large quantities on the other side of the same

valley, or over the crest of a small hill.

        The amount of water stored in the moss and tundra and above the permafrost

area will not only depend upon the rainfall, character and details of the

surface and its ability to retain moisture, but also upon the timing of the

fall rains with respect to the freeze-up of the surface of the ground, moss,

or tundra, and depth of seasonal thaw with respect to the upper limits of

permafrost; also whether or not the water available in thawed lenses or

pockets of gravel in the permafrost can be used at critical seasons of the

year.

        From a study of Figures 1 and 2 and Table I, it will be apparent that

storage or pondage and deep seepage present quite a different problem than in

a temperate zone, requiring careful detailed study of each individual area.

In most cases such studies will indicate that the capacity of development is

considerably less than for like stream flows and precipitation in milder

climates and that relatively large installations of supplementary or auxiliary

power will, in many cases, have to be given consideration.

        In areas where permafrost and frozen much are present, any change in the

thermal equilibrium of the materials may result in releasing from confinement

large volumes of much which, because of the particle size of the solids, are

readily carried in suspension in moving water. When the water with such solids

reaches storage areas serious silting problems may result.

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        Anchor ice and ice forming on permafrost must be considered when design–

ing intakes. Such ice is frequently released in large blocks, carrying with

it sand and gravel.

        [ 3 we be hold is used. ?] It must be borne in mind that the capacity of pipes and other similar

hydraulic structures may be materially reduced by the formation of ice on

the interior walls. Figure 3 illustrates a 60-inchs pipe which collapsed

during cold weather. An ice plug had formed at the intake and when one of

the lower valves was opened to drain the pipe, portions of the pipe collapsed

because the provisions for admitting air into the pipe failed to work.

       

Transmission Lines

        In designing transmission lines (pole or tower) for the distribution of

electrical energy in areas where permafrost is present, especially if the

permafrost extends upward so it makes contact or nearly a contact with the

lower limit of seasonal thaw, additional factors other than those usually

evaluated in the development and design of transmission lines should be given

consideration.

        The reconnaisance survey for a line should include an investigation of

( 1 ) the character of the cover which acts as an insulator to the permafrost

immediately below such cover, ( 2 ) the depth of seasonal thaw, ( 3 ) the character

and packing of the materials in place, immediately above the upper limit of the

permafrost, ( 4 ) the relationship between freeze-up and rainfall, and ( 5 ) the

general characteristics of the terrain, giving special attention to the possible

movement of water on the surface in the zone of seasonal thaw and the zone

between the seasonal thaw and permafrost.

        The freezing and swelling of the materials in the “frost zone” may develop

forces which tend to lift a pole as illustrated in Figure 4. The effect of

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[ ?] such lifting forces can be materially reduced by placing collars or muffs

Fig. 5 around the pole as illustrated in Figure 5 or by providing a weak or slip

plane around the pole.

        In the setting of poles, consideration must be given to the surface

water as indicated by arrows in Figure 6, and the groundwater from b which

may seep along the contact between the pole and the ground until it reaches

the foot of the pole where it freezes, lifting the pole. Successive layers

of ice at the foot of the pole results in successive lifting of the pole.

        Adhesion between a pole and permafrost may be assisted, to overcome the

Fig. 6, 7 lifting force a (Fig. 6), by fastening an anchor near the base of the pole

in the permafrost as illustrated in Figure 7. Where this construction is

used, care must be taken when back-filling the excavation to avoid the

development of a contact surface at a (Fig. 6), which may permit the migration

of groundwater. Wherever practical, the writer recommends that this type of

anchorage be avoided.

        In the Arctic, tripod construction over the tundra has been effectively

used for temporary and semipermanent telephone lines where first cost and

time are the governing factors. This construction is especially applicable

in areas where small native timber is available.

        In using tripod construction at angle points, it may be advisable to

suspend a rock or basket of rocks from the tripod or from the legs of the

tripod in order to assist in the prevention of overturning. The tripods are

usually set on the tundra during cold weather when the surface is frozen.

       

Electrical Distribution

        Consideration must be given to the large range of temperatures in the

Arctic in the calculation of sags and spacing of wire when designing electrical

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distribution lines. Because of the high cost of properly preparing foundations

and maintaining them, long spans are indicated. Large temperature ranges re–

sulting in relatively great sags require careful consideration of resulting

tensions (1; 2; 3; 4).

        Careful study of local weather conditions in any particular area is

recommended because wind and ice conditions vary greatly in different section.

The writer has experienced local winds in Greenland which were greater than

any winds of which he has knowledge in either the temperate zone or Alaska.

When investigating the corona limit of high-tension lines in the Arctic, the

investigation should not be limited to the fair-weather value. Local and

seasonal conditions at which it will operate should be considered.

       

Electrical Grounds

        In permafrost areas the grounding of electrical equipment is not as

readily accomplished as in a temperate zone. It has been the writer’s prac–

tice, wherever practical, to carry the grounds to a zone of assured and

continuous groundwater movement; otherwise, the system was treated as

ungrounded.

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BIBLIOGRAPHY

1. Copperweld Steel Company, Glassport, Pa. Sags and Tension Charts for

Conductors in Overhead Lines .

2. General Electric Company. “Performance charts for 60 cycle transmission

lines,” Gen.Elect.Rev . Oct., 1932.

3. Graybar Electric Company. Calculations by Direct Use of the Catenary

Curve .

4. Pender, Harold, and DelMar, William. Handbook for Electrical Engineers .

N.Y., Wiley, 1922.

       

G . eorge W. Rathjens