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ing the safe overload or economical operating capacity of the machines remaining in service. For the purposes of this study it is assumed that each unit could operate economically when carrying an overload of 10 per cent continuously and the installed capacity of the substitute steam plant has been determined on this basis with one unit out of service.
The largest and most efficient steam power plant in southern California at present is the Long Beach No. 3 plant of the Southern California Edison Co., which is designed for an ultimate installation of four units of 100,000 kilowatts capacity each. The first unit of this plant was placed in service June 20, 1928, and a second unit is now being installed. The plant is equipped for using either natural gas or fuel oil and is arranged so that coal-burning equipment can be installed if later found that such fuel is more economical than fuel oil or natural gas. Sea water is used for cooling purposes, the steam pressure is 400 pounds, and the temperature of the steam is 700° F. At 100 per cent load factor this plant produces a little better than 490 kilowatt-hours net per barrel of fuel oil, corresponding to a fuel economy of 12,674 B. t. u. per kilowatt-hour. Data obtained from the Railroad Commission of the State of California and from the Southern California Edison Co. indicate that the cost of the Long Beach No. 3 plant, when the ultimate installation of four units is completed, will amount to $77.50 per kilowatt of capacity. Data submitted by the Los Angeles Gas & Electric Corp. show that the Seal Beach steam plant, which has an installed capacity of 75,000 kilowatts, cost $78.20 per kilowatt of capacity. In these estimates the cost of a substitute steam plant has been taken at $77.50 per kilowatt of installed capacity, the fuel consumption has been taken at 0.55 barrel per kilowatt of installed capacity per year plus 4600 barrel per kilowatt-hour generated, and the cost of operation and maintenance has been taken at $2.25 per kilowatt of required capacity per year corresponding to the actual figures for the Long Beach No. 3 plant.
Estimated cost of equivalent steam-generated energy
(Annual kilowatt-hours generated by equivalent steam plant, 3,249,000)
I With interest on investment at 4.75 per cent; depreciation, 2.25 per cent; amortization, 1.07 per cent; and general expense, 2 per cent.
2 Interest on investment, 7.5 per cent; depreciation, 1.9 per cent; Federal tax, 0.4 per cent; general expense, 2 per cent; State tax, 8.1 per cent on all other costs.
The substitute steam power plant would be located at tidewater and it is assumed that power would have to be transmitted an average distance of 25 miles to reach the terminal substations. The normal capacity of each 220 kilovolt circuit from the substitute steam plant to the terminal substations has been taken at 200,000 kilowatts and one spare circuit has been included so as to afford the same factor of safety as is used in connection with Boulder Canyon transmission. The capital cost and the annual cost of operation of each circuit of the back transmission lines from the substitute steam plant have been estimated on the same assumptions as used for the Boulder Canyon transmission lines except that no condenser equipment has been included with the steam-plant transmission, whereas with Boulder Canyon transmission there has been included sufficient condenser capacity for line regulation. State taxes have been omitted from the cost of substitute steam power and from the cost of Boulder Canyon power in the private corporation set-up, because this tax is calculated on the gross revenue which would be the same whether power is obtained from steam or from Boulder Canyon and it would therefore have no effect on the value of power at Boulder Canyon. Cost of back transmission from steam stand-by plant to Boulder Canyon Terminal
Estimated costs of transmission from equivalent steam plant to load center-public
1 Right of way, 50 feet for each circuit and at $5,000 per acre; line at same rate per mile as for line to Hoover Dam; terminal substation at $10 per kilowatt.
* Interest, 4.75 per cent; depreciation, exclusive of right of way, 1.25 per cent; amortization, 1.107 per cent; operation and maintenance of line, $125 per circuit mile and of terminal substation at 2 per cent; general expense, 2 per cent.
Interest at 7.5 per cent; Federal tax, 0.4 por cent; operation and maintenance, depreciation, and overhead, unchanged; State taxes, 8.1 per cent.
Boulder Canyon power will be transmitted about 280 miles to reach the load centers in southern California and it is assumed that transmission will be at 220,000 volts. With several circuits operating in parallel the safe carrying capacity of each circuit will be about 110,000 to 120,000 kilowatts delivered, with ample margin for stability. The number of circuits required for any particular size of installation at Boulder Canyon is determined by dividing the total peak power delivered by 110,000 kilowatts. Switching equipment for crossover and sectionalizing purposes at the mid-point of the transmission lines is included.
Terminal substations including sufficient condenser capacity for regulation of power factor would be required whether power is obtained from a steam plant or from Boulder Canyon and therefore the capital cost as well as the annual cost of these substations does not affect the value of Boulder Canyon power. Additional condenser equipment is required for line regulation, however, and the estimates of Boulder Canyon transmission include one kilovolt-ampere of condenser capacity for each kilowatt delivered.
Right of way for Boulder Canyon transmission lines will be largely over public land which will cost nothing; but some very expensive right of way will be required for these lines in the vicinity of Los Angeles. It is assumed that 60 miles of lines will traverse semi-improved land, the right of way for which is estimated at $250 per acre; and 33 miles will pass through highly improved territory, the right of way for which is estimated at $5,000 per acre, with a width of 50 feet per circuit.
It is understood that the cost of operation and maintenance of the Big Creek 220-kilovolt lines of the Southern California Edison Co. amounts to $150 per circuit mile per year. These lines pass through country which is very different from the desert country through which the Boulder Canyon lines will pass. The right of way of the Big Creek lines must be cleared of brush every year at considerable cost to prevent fires, whereas a large part of the Boulder Canyon lines will be free from brush. The Edison Company has in the past spent large amounts for the patrol of its Big Creek lines to find the cause of flashovers, and after finding the cause additional money has been spent on corrective measures such as bird guards. The Boulder Canyon lines would be designed in the light of the experience gained from the Big Creek lines and the result would doubtless be improved reliability as well as a lower cost of operation and maintenance. The annual cost of operation and maintenance of the Boulder Canyon transmission lines has therefore been taken at $125 per circuit mile per year.
Transmission lines, Boulder Canyon to load center
Number of circuits
Capacity, delivery to terminal, kilowatts.
440,000 550,000 660, 000 Construction cost: 1 Line 2
$20, 176, 000 $25, 097, 000 $30, 018, 000 Sectionalizing station 3
860, 000 1, 044, 000 1, 228, 000 Terminal substation 4
7, 676, 000 9, 594, 000 Right of way-
11, 514, 000
3, 667, 000 4, 583, 000 5, 500,000 Total...
32, 379, 00040, 318, 000 48, 260, 000
Public development 5
2, 628, 000
3, 275, 000
3, 917, 000 5, 323, 000
1 All items include 15 per cent for engineering, overhead, and contingencies, and 4 per cent for interest during construction.
: Consist of 542 towers at $1,066 each; conductors at $7,033 and insulators at $1,443 per circuit mile; telephone, roads, bridges, and patrol stations at $414,000.
: Station at $154,000 per circuit and $103,000 for buildings, camps, oil system, etc.
* Interest, 4.75 per cent; amortization, 1.107 per cent, depreciation, exclusive of right of way, 1.25 per cent; operation and maintenance, $125 per circuit mile for line, $5,000 per pair and 2 per cent of cost for sectionalizing station, and 2 per cent for terminal station; general expense, 2 per cent.
o interest, '74 per cent; Federal tax, 0.4 per cent; State tax, 8.1 per cent; and other items as for public development.
It is generally considered that some amount of steam stand-by should be provided in connection with long-distance transmission, such as will be involved in the case of transmission of Boulder Canyon power to southern California, in order to provide reliable and satisfactory service. Several circuits will be required for the transmission of Boulder Canyon power and when one of these circuits is out of service for any reason it will be possible to transfer a part of the power normally carried by that circuit to the other circuits. For the purposes of this study, it is assumed that the circuits remaining in service can be operated at a capacity of 120,000 kilowatts delivered, at times when one circuit is out of service. The amount of steam standby is then determined by the normal capacity of one transmission circuit less the overload capacity of the circuits remaining in service.
Average power generated at Boulder Canyon,
kilowatts. | 411, 000 Load factor.
55 Peak generated.
kilowatts 747, 000 Delivered peak, 12 per cent loss
-do.---657, 000 Circuits
6 Total capacity, 1 line out.
kilowatts. 600, 000 Stand-by needed at terminal.
---do. 57, 000 Stand-by needed at steam plant, 2 per cent loss
411, 000 411,000
80 632, 000 514, 000 556, 000 452, 000 5
4 480, 000 360,000 76, 000 92, 000
The cost of the steam stand-by plant has been taken at the same cost per kilowatt as used for the cost of the substitute steam plant. A steam plant built purely for stand-by service would sacrifice high efficiency for low capital cost and while the proposed stand-by plant is of relatively small capacity it is believed fair to assume that it could be built for the same unit cost as the larger plant. Actually the stand-by capacity would, no doubt, be provided as part of a large plant, in which case the cost per kilowatt would be the same as for the substitute steam plant, or $77.50 per kilowatt.
The annual cost of the stand-by plant has been taken on the same unit basis as for the larger substitute steam plant except that operation and maintenance has been reduced 50 cents per kilowatt per year and fuel cost includes one barrel per kilowatt capacity for stand-by fuel only. The annual cost is then practically independent of oil cost.
Public develop- Private development
Capital cost 1
$2, 725, 000
125 miles of line at $19,000 per mile and 150-foot right of way at $5,000 per acre. ? On basis previously outlined for Boulder Canyon lines.
Total annual cost of steam stand-by plant and line
Cost of fuel oil per barrel
Total annual cost exclusive of
Total annual cost exclusive of
Total annual cost exclusive of
Load factor, 55 per cent, total annual
cost. Load factor, 65 per cent, total annual
cost.. Load factor, 80 per cent, total annual
VALUE OF BOULDER CANYON POWER
The estimated value of Boulder Canyon power as determined by the cost of substitute steam power generated near the load center, both with and without steam stand-by, is derived in the tables immediately following for both public and private steam-plant construction, with fuel prices of 70, 75, and 80 cents per barrel of fuel oil, and for load factors of 55 per cent, 65 per cent, and 80 per cent. These tables are based on the Government providing the Boulder Canyon Dam and power house but assume installation and operation of the machinery and equipment by the lessee.
Curves D, E, and F, on Plates 1 and 2 show graphically the estimated value of power at Boulder Canyon for fuel-oil prices of 80, 75, and 70 cents per barrel, respectively, and for various load factors.