Stone and Webster Project for Puget Sound Power Company on the Puyalup River

[Trade Journal]

Publication: Street Railway Review

Chicago, IL, United States
vol. 14, no. 9, p. 605-615, col. 1-2


The Stone & Webster Properties on Puget Sound. — III.

 

The Puyallup River Water Power Development Near Tacoma, Wash.


The cities of Seattle and Tacoma, Wash., and their suburban towns have in five years increased in population from 130,000 to upwards of 225,000; the growth of manufacturing industries and construction of street and interurban electric railways has kept pace with the increase of population, and to supply the consequent demand for electric power an unusually large generating plant of the most modern type has been constructed on the Puyallup River.

 

General Plan of Development.

 

The Puget Sound Power Co., the owner of the plant, was organized in the year 1902, for the purpose of developing water power for use by the Stone & Webster properties in Seattle and Tacoma. Before beginning the construction of the plant a careful investigation was made of the variations in the flow of the several rivers in western Washington and the other features which would affect the reliability of the service obtainable from each, and a general plan was then adopted for the development of this power on the Puyallup River with an initial installation of 20,000-h.p., the plans being made and the greater portion of the work carried out on the basis of continuing the initial installation to an ultimate development of 40,000 h.p.

The design consists of diverting the Puyallup River just below the junction with the Mowich and carrying the water by means of a flume ten miles to a reservoir located on a high plateau, and thence discharging by means of steel pipes against wheels in the power house under a head of 872 ft.; the water wheels so driven to be direct connected to electric generators and the electric current so produced to be transmitted at a pressure of 55,000 volts 48 miles to Seattle and 32 miles to Tacoma.

 

WEST VIEW OF POWER PLANT PUGET SOUND POWER CO. - FOUR GENERATORS IN OPERATION.
West View of Power Plant Puget Sound Power Co. - Four Generators in Operation.

 

All water rights and the necessary land abutting on the river from the point of diversion to point of return were secured, also all land necessary for flume and other structures, and actual work of development was commenced Mar. 1st, 1903. To facilitate construction a spur track 2 1/2 miles long was built from the Kapowsin Station of the Tacoma Eastern R. R. to a new station at Electron and continued a mile farther to the power house site. From Electron a standard gage cable incline was built to lift to an elevation of 950 ft. to the reservoir site above the power house, and a wagon road to the head works. The first generator unit of 5,000-h.p. was put into commercial operation delivering power to Seattle and Tacoma on April 14, 1904, less than fourteen months after work was commenced; the plant was put into complete operation for its initial installation of 20,000 h.p. on July 23, 1904.

 

Source of Supply.

 

The Puyallup River has its source in the glaciers of Mount Rainier, the highest mountain in the United States and one of the great mountain peaks of the world, covering 200 square miles and rising 14,500 ft. above the waters of Puget Sound. That part of the mountain higher than 5,000 ft. above sea level is covered with snow and ice, and the precipitation resulting from the moisture-laden air of the Puget Sound region coming in contact' with the glacial cold of the mountain sides is estimated to average 140 in. per annum. The fields of ice and snow which result from this precipitation are constantly moving down the mountain sides to the valleys about its base in the form of slowly moving glaciers of many square miles in extent, which fill the valleys to the depth of hundreds of feet, and are constantly being added to from above and melting away below.

 

Illustration

 

These great masses of ice increase in size and depth each winter and decrease by melting under the heat of summer, and the hottest and driest days of summer produce the greatest rate of melting. The Puyallup and Mowich Rivers drain a fan-shaped section of the mountain and five of the glaciers described, and thence flow through mountain ranges which add greatly to their volume, each for a distance of about 12 miles from the glaciers, and then join, the combined rivers being then known as the Puyallup. The water shed of these rivers includes a rough and heavily timbered country not covered with ice or snow and below the very high mountain range. The streams of this lower timbered country are fed by the copious rains of the Puget Sound country which occur during the fall, winter and spring months concurrently with cool weather. During such cool weather the rain and the run-off in this timbered section is heavy and at the same time snow and ice accumulate on the mountain and the run-off from it is comparatively small. When the warm weather conies the rain and the run-off from the timbered section is at a minimum and the melting of the snow and ice on the mountain and the rim-off from the same is at a maximum. This balance, or alteration of the heavy run-off from the timbered and ice sections, results in a remarkably uniform flow in the river at the point from which the water is taken for power purposes and makes the operating conditions in using this water ideal.

 

MT. RAINIER FROM FLUME NEAR SPILLWAY - THE \"RESERVE SUPPLY.\"
Mt. Rainier From Flume Near Spillway - the \"Reserve Supply.\"

 

Although the dam and intake are located within 10 miles of the nearest glacier the elevation at this point of diversion is only about 1,700 ft. above sea level and the climate at this elevation is so uniformly mild and the water flows so rapidly that no ice comes clown the river nor is formed either in the flume or reservoir.

 

Utilization of Current.

 

The power is used for all branches of service—light, power and railway. It supplies the electric railway systems in Seattle and Tacoma aggregating 168 miles of trolley road, the multiple unit, third rail line between Seattle and Tacoma, two cable roads, one in Seattle and one in Tacoma, furnishes power for numerous factories, together with the shops of the Northern Pacific Ry., and the new pumping plant of the city of Tacoma, and supplies the greater portion of commercial and residence lighting and street lighting in Seattle and in the towns between Seattle and Tacoma.

 

INTAKE AND DAM, LOOKING EAST.
Intake and Dam, Looking East.

 

Much of the power is distributed as alternating current; two-phase for power and single phase for lighting, hut there is also connected 10.000-kw. of converting capacity for producing direct current, 2,000 kw. of which is used for light and stationary motor supply. The bulk of the converting machinery (7,300 kw.) being of the synchronous type, it is not necessary for the water power plant to generate or transmit idle currents.

The distribution of the current to the various localities and the transformation and conversion fin- various uses takes place at 11 sub-stations containing 26,000 kw. of transformer capacity. Six of these are designed for transforming the 55,000-volt current to lower voltage and eight contain machinery converting to direct current for railway use.

 

Dam and Intake.

 

At a point one-half mile below lie confluence of the Puyallup and Mowich Rivers and about 1,700 It. above sea level, is located the dam and intake of the Puget Sound Power Co. Here the water necessary for the operation of its plant is diverted by a low, solidly constructed dam, through a masonry intake to a flume which is constructed on the southwest side of the river for a distance of ten miles. The darn or converting weir is 200 ft. long and 5 ft. high and covers the bed of the river longitudinally for a distance of 60 ft., exclusive of the down-stream apron. It is built down to an impervious bottom of clay hardpan and is made tight by three rows of triple lap sheet piling set into hardpan bottom and bedded in concrete; it is faced with 6 x 12-in. timber covered at the crest with 1/4-in. boiler plates. While the whole dam is a spillway, there is a lower spillway 30 ft. wide to localize scour at the intake end. The intake is set at right angles to the darn and is constructed of concrete masonry. It is 62 ft. wide at the river bank and is protected by a screen grating made of iron bars ¼ in. x 4 in. x 6 ft., spaced 2 1/2 in.

Provision is also made for the insertion of flash hoards in grooves in steel frames in such manner as to regulate or entirely slut off the intake at a point between the river and the grating-. A radial gate of unique design is also installed at the junction of the masonry intake and the flume for the purpose of quickly controlling- the amount of water delivered to the flume.

 

Flume.

 

From head works to reservoir, a distance of about tell miles, the water is carried in a flume which as now constructed is 8 ft. wide and 5 ft. high inside measurements, but is framed for the addition of plank to make it 8 ft. high. The flume is supported on a low trestle work which follows the contour of the land, this trestle work is the same construction, and of equal strength to that usually used for railroads, and in fact during the construction heavy work trains were operated over its entire length. The flume proper is constructed of surfaced planks 2 1/4-in. in thickness and 12 in. wide, and the frames which surround it are placed 4 ft. between centers: the flume is built on a uniform grade of 7 1/2 ft. to the mile. Sand boxes and automatic spillways are provided at various points along the flume and a number of gates are also provided for emergency use, while a light railroad track for hand cars of standard gage is laid along the top of the flume to facilitate inspection and repairs.

 

FLUME LINE THROUGH ROCK CANYON OF PUYALLUP.
Flume Line Through Rock Canyon of Puyallup.

 

All danger timber along the line of the flume is being removed and the flume trestle is built on rock or hardpan foundation which protects it against trouble from slides. In constructing this flume the usual plan of building curves as a series of tangents was not followed, the bends ill the flume are made with true curves presenting a uniform and smooth interior surface and thus facilitating the flow of water.

 

Reservoir.

 

The flume discharges its water into a reservoir located on a high plateau, nearly 900 ft. above the power house. This reservoir serves as a relay to maintain the plant in continuous operation, in case of interruption of water supply, and also serves the very useful purpose of supplying, water for temporary overloads in excess of discharge capacity of flume, or in other words, for equalizing the daily fluctuations of load. The location of the reservoir is particularly well adapted for the purpose, the material excavated from the higher side of the site was used to form the embankment on the lower side of the reservoir. This material is a glacial boulder till of clayey consistency which required blasting before it could be handled with steam shovel; it paddled well and formed a water-tight fill which set hard in embankment almost like concrete.

 

RESERVOIR DURING CONSTRUCTION, SHOWING POOL ARRANGEMENT FOR OPERATING WITHOUT FILLING RESERVOIR.
Reservoir During Construction, Showing Pool Arrangement for Operating Without Filling Reservoir.

 

WAGON ROAD TO HEADQUARTERS.
Wagon Road to Headquarters.

 

The flume enters one end of the reservoir and, when the latter is drained, discharges into a concrete basin in front of the forebay. This arrangement permits the emptying of the reservoir for inspection or cleaning without interrupting the delivery of water to the power house, and distributes the water quietly to the penstocks tahout danger of carrying air into the pipes.

The forebay is of concrete and is constructed inside of the reservoir, being divided into compartments forming separate gate chambers for the main penstocks. Each compartment is provided with iron racks or screens with stop boards to permit inspection or repairs without emptying the reservoir. The gates are arranged for connecting tin electric motor drive to he controlled front the power house.

The depth of water in the reservoir is at all times shown at the power house switchboard by a Dibble automatic electrical indicating and recording water gage fitted with low water alarm. This gage is operated by three wires running from a float-actuated Dibble transmitter located in the reservoir.

 

Penstocks.

 

The penstocks, one for the two exciters, one for each of the four generating units now installed, and one for each of the remaining four units to be installed later, are carried through the reservoir embankment in the form of concrete protected wood stave pipes, joining the steel pipes just outside the reservoir embankment. Of the eight main pipes for the complete plant four, together with the exciter pipe, are now continued about 1,700 ft. down an incline of about 30 degrees to the power house on the river bank below. Each main pipe is of riveted steel 48 in. in diameter and 1/4 in. thick at the upper end, tapering to 36 in. in diameter and 3/4 in. thick at the lower end, and was furnished by the Risdon Iron & Locomotive Works. The penstocks are anchored by massive concrete abutments and till surface water is carefully drained away, and as a further security the pipes are protected with backfilling of earth on winch is phoned quick growing vegetation.

 

VIEW OF PENSTOCK LINES, LOOKING SOUTH.
View of Penstock Lines, Looking South.

 

 

Power House.

 

The power house is built in the bank of the river on a foundation ,It piling and rock; it is of massive concrete, brick and steel construction; the building for eight units will be about 100 x 266 ft. divided longitudinally into two parts, a generator house and a transformer and switching house. The generating units are arranged parallel to and along the riverside of the building, the penstocks being brought to them under the main floor from the rear. The transformers are grouped in isolated rooms of concrete in the basement of the switch house; the switching apparatus mid wiring being in compartments overhead.

 

Water Wheels.

 

Each "unit" consists of two overhung Pelton water wheels, 10 ft. 6 in. in diameter, mounted on each end of the shaft of each five thousand horsepower two-bearing generator; the nozzles are of the needle type arranged for automatic deflection by Lombard "Type L" governor for speed control, the operation of the needles being only for economical adjustment of the discharge to the load of the machine; each nozzle is also provided with a motor operated gate valve for cutting off the water supply. The wheels have a maximum capacity of 7,500 h.p. for each unit.

The wheels are arranged to be started and stopped and adjusted for speed from the main operating switchboard at one end of the generator room; motor driven pumps provide oil supply for ordinary lubrication, pressure oil for forced lubrication in starting, and circulating water for cooling bearings.

 

INCLINE CABLE RAILWAY - MAXIMUM GRADE 68 PER CENT.
Incline Cable Railway - Maximum Grade 68 Per Cent.

 

The rotors and wheels of each unit are hydraulically forced onto a 24-in. hollow nickel steel fluid compressed shaft. The spray from the wheel discharges collecting in the water wheel housing enters this hollow shaft and automatically serves to cool the bearings. At the date of their installation these were the largest impulse wheel units ill the world.

 

Electrical Equipment.

 

There are four General Electric revolving field generators of 3,500 kw. capacity each, with an overload capacity of 25 per cent for two hours, wound for three-phase current at 2,300 volts and a frequency of 60 cycles per second.

Two 150-kw. 125-volt 600 r.p.m. shunt wound exciters are provided, each direct connected to an overhung Pelton water wheel and to a 2,080-volt 200-h.p. three-phase induction motor. The wheels driving exciters are not provided with automatic governors, and the direct connected induction motors serve this purpose, operating either as motors or generators according as they run below or above synchronous speed. The motors also afford a relay source of power for excitation in case of failure of an exciter-water-wheel or its water supply. Each exciter is capable of exciting six generators under all conditions.

 

CROSS SECTION LOOKING EAST, SHOWING CIRCUITS NOS. 1 AND 4.  Circuit No. 1 - From Generator to Low Tension Bus Bars A-B.  Circuit No. 4 - From High Tension Bus Bars C-D to Line.  Main Low-Tension Bus in Use, Auxiliary Bus Disconnected..
Cross Section Looking East, Showing Circuits Nos. 1 and 4. Circuit No. 1 - From Generator to Low Tension Bus Bars A-B. Circuit No. 4 - From High Tension Bus Bars C-D to Line. Main Low-Tension Bus in Use, Auxiliary Bus Disconnected..

 

There are three banks of transformers installed at the power station, each bank consisting of three 2,333-kw. water cooled, oil insulated, General Electric transformers with 25 per cent overload capacity for two hours. Each bank has a capacity equivalent to two generators, the third bank being spare, so that the failure of even a complete bank would not diminish the capacity of the station. The transformers arc connected delta on both the high and low tension sides and the arrangement of the windings is such that with 2,300 volts on the low tension side, high tension voltages of 27,500, 45,000, and 55,000 may be derived. These transformers have been operated at 55,000 volts from the beginning.

Water for cooling is derived from a spring above the power house, supplemented by connection with the reservoir. The transformers are piped so that the oil can be removed from the case into large storage tanks, and an emergency blow-off valve is arranged to discharge the oil quickly into the river.

Before filling these transformers with oil they are dried out at a temperature of 80° C. under a vacuum of 26 in. for 10 hours. No oil was used that did not stand a potential test of 40,000 volts between 1/2-in. flat electrodes placed 2-10 in. apart. After filling and allowing the oil to thoroughly settle, samples of oil from bottom and top of each transformer were subjected to this potential test and no transformer was put into service before the oil passed this test satisfactorily.

 

CROSS SECTION LOOKING EAST, SHOWING CIRCUITS NOS. 2 AND 3.  Circuit No. 2 - From Low Tension Bus Bars A-B to Transformers.  Circuit No. 3 - From Transformers to High Tension Bus Bars C-D.  Main Low-Tension Bus in Use, Auxiliary Bus Disconnected..
Cross Section Looking East, Showing Circuits Nos. 2 and 3. Circuit No. 2 - From Low Tension Bus Bars A-B to Transformers. Circuit No. 3 - From Transformers to High Tension Bus Bars C-D. Main Low-Tension Bus in Use, Auxiliary Bus Disconnected..

 

 

Electrical Arrangement.

 

For connecting each generator and transformer bank to the low tension bus bars, and each transformer bank and transmission line to the high tension bus bars, a full complement of remote control, motor-operated oil switches is provided.

There are two sets of 2,300-volt bus bars, designated as the main and auxiliary busses. The main bus is for regular operation while the auxiliary bus is for emergency operation, and for relaying the main bus in case of repairs to the latter. Both sets of bus bars are identical and any generator and any transformer bank can be connected to either set.

Between each generator and each set of 2,300-volt bus bars there are two sets of disconnecting switches and a triple pole General Electric "Type H" 1,200-ampere, motor-operated oil switch, a set of disconnecting switches being on either side of the oil switch. Between each set of bus bars and each transformer bank there are two sets of disconnecting switches and a "Type H" 3,000-ampere motor-operated oil switch, the arrangement being similar to that of the generator switches. The purpose of the disconnecting switches is to remove the potential from the oil switches that inspection of or repair to the oil switches may be safely made. The disconnecting switches are not to be operated when carrying current except under emergency conditions. All ordinary switching is done by means of the oil switches which simultaneously open and close the three legs of the three phase circuit. In addition to the single pole double throw switches mounted on the operating panels, for opening and closing these switches, when cutting in or out a generator or transformer bank, there is for each oil switch a clock type time limit relay actuated by secondary current from current transformers in circuit with that switch, these relays operating the motor connected to the oil switch in case of an overload or short circuit lasting the period for which the relay is set. These relays can be set for overload periods of 4 seconds down to a small fraction of a second, it thus being possible to automatically localize short circuits on the system, and in apparatus, without completely shutting down the system. The electrical arrangement of the motors driving the exciters is the same as that of the generators.

There is one set of high tension bus bars, divided into three sections by sectionalizing switches, each transformer bank being connected to a corresponding section, and one line to each of the end sections.

Between the high tension bus and each hank of transformers there are two sets of disconnecting switches and one triple pole General Electric 60,000-volt, 400-ampere, motor-operated oil switch, a set of disconnecting switches being on either side of the oil switch. There are two outgoing high tension lines and each line is controlled as just described for the transformer banks. All the high tension oil switches possess the automatic features as described for the low tension oil switches.

Lightning arresters without reactance coils are provided for each outgoing line.

Static dischargers are provided for the low tension side of each transformer bank. These static dischargers consist of three 2,500-volt S. P. lightning arresters connected in star, the neutral point grounded. They limit the potential of the low tension winding to 2,500 volts above ground, and would come into action in case of grounding of one side of the transmission line or transformers.

The control of all the oil switches is from operating panels erected on a gallery in the east end of the generator room, at an elevation of 14 ft. above the generator room floor. The arrangement of panels from left to right is : Exciter panels, generator end; exciter panels, motor end; generator panels; totaling panel; generator panels; transformer control panels; high tension line panels.

The generator and exciter field rheostats are hung below the gallery and are operated from pedestals by means of shafting and bevel gearing, the contact plates being on the rheostat boxes.

The highest alternating current potential on the switchboard panels is 115 volts derived from potential transformers and the highest direct current potential is 125 volts derived from the exciters.

Each generator panel contains three ammeters, one voltmeter, a polyphase indicating wattmeter, a polyphase intrograting wattmeter, and a field ammeter.

Each outgoing line panel contains three ammeters, and the totaling panel contains a power factor indicator, a frequency indicator, a curve drawing voltmeter and three curve drawing ammeters. The curve drawing instruments belong to a type lately developed by the General Electric Co., giving a record of 3 in. long per hour.

The control of the plant is completely from the switchboard gallery, a water wheel may be started or stopped, a generator brought up to voltage, synchronized with other generators on either bus, a transformer bank cut in on either bus and a transmission line connected in circuit without the presence of a person in the room where the actual switching is done, the lighting of a red lamp indicating the closing of a switch and a green lamp the opening of a switch.

 

Switch House Arrangement.

 

Two of the illustrations show sections through the generator room and switch house. The transformer rooms are at the same level as the generator room but isolated from the latter by rolling steel doors. On floor No. 2 are the low tension disconnecting switches, the generator and transformer cables going to the sets of disconnecting switches installed between the oil switches and the bus; being on the outer walls and immediately below the bus bar compartments which are above on floor No. 3. In the center of floor No. 3 are the low tension oil switches corresponding to a generator or transformer hank being arranged back to back and facing their corresponding set of bus bars. The bus bars are of the laminated type consisting of flat copper bars with expansion joints and supported on marble slabs set on edge which in turn rest on concrete slabs forming barriers between adjacent bus bars. The compartments formed by the concrete slabs arc to he covered by insulated fireproof doors.

The oil switches are installed in brick cells with soapstone bottom and top slabs and doors. Each pole of a switch is separated from the other poles by brick harriers.

 

SWITCH HOUSE.  5th Floor - H. T. Bus Bar at Left - Transformers at Right.  4th Floor Instrument Transformers - H. T. Disconnecting Switches.  3d Floor - 2,300-volt Bus Bar - 2,300-volt Oil Switches.  2nd Floor - Disconnecting Switches.
Switch House. 5th Floor - H. T. Bus Bar at Left - Transformers at Right. 4th Floor Instrument Transformers - H. T. Disconnecting Switches. 3d Floor - 2,300-Volt Bus Bar - 2,300-Volt Oil Switches. 2nd Floor - Disconnecting Switches.

 

The same general scheme is used for both the low and high tension disconnecting switches and oil switches, except that only one set of high tension bus bars is at present installed, provision being made for the later installation of the second set. The high tension disconnecting switches and current transformers are on floor No. 5, while the high tension oil switches are on floor No. 6. Above floor No. 6 are the two outgoing high tension line towers, 'in the north end of which are the high tension lightning arresters, each pole being separated from its adjacent pole by brick harriers extending the full length of the arrester. The lines emerge from the wire tower centrally through an extra heavy 30-in. sewer tile covered by a glass plate.

 

INTERIOR OF POWER HOUSE, JUNE 8, 1904.
Interior of Power House, June 8, 1904.

 

 

Transmission Line.

 

Front the power house two parallel transmission lines run a distance of 22 miles to Bluffs, a station on the line of the Puget Sound Electric Ry., 9 miles from Tacoma and 25 miles front Seattle. From Bluffs one line runs for a great part parallel to the transmission line of the Puget Sound Electric Ry. to Seattle and one to Tacoma, also parallel to the transmission line of the Puget Sound Electric Ry.

 

RIGHT ANGLE TURN IN TRANSMISSION LINE AT ORTING.
Right Angle Turn in Transmission Line at Orting.

 

WIRE TOWERS - HIGH TENSION LINES LEAVING POWER HOUSE.
Wire Towers - High Tension Lines Leaving Power House.

 

The transmission line of the Puget Sound Electric Ry. is at present operating at 27,000 volts but the line is designed for operating at double this potential, so that when this line is changed over to a 55,000-volt basis there will be two complete and independent pole lines from the power house to Seattle and Tacoma. At Bluffs there are erected junction pole switches by which the two transmission lines may be cut through independently, one to Seattle and one to Tacoma, or both lines put in multiple, or any section isolated without interfering with the operation of the other sections.

 

SHOWING CURVE CONSTRUCTION - NEAR SEATTLE.
Showing Curve Construction - Near Seattle.

 

From the power house to Bluffs a private right of way has been secured, the two pole lines being from 50 to 80 ft. apart. When passing through wooded sections all dangerous timber has been cleared well back on the land adjacent to the right of way on both sides, so as to completely protect the transmission line.

The minimum length of poles used was 45 ft. with a minimum top diameter of 10 1/2 in. The standard spacing is 125 ft. on straight line and 90 to 100 ft. on curves.

The main cross arm is 5 in. x 7 in. x 7 ft. 4 in. Washington fir, boiled in raw linseed oil, giving it a much longer life than an untreated arm. This arm is bolted to the pole by two galvanized iron bolts and braced by a combination wood and galvanized iron brace. At the top of the pole is an arm 5 in. x 7 in, x 18 in. supported by an angle iron frame bolted to the pole by two galvanized iron bolts.

The main arm supports two insulators and the top arm one insulator giving an equilateral triangular spacing of 72 in. between wires.

The pins on one line from the power house to Bluffs and from Bluffs to Seattle and Tacoma are galvanized malleable iron, cast hollow and circular in cross-section and having a shank diameter of 2 ½ in. The pins on the other line are of the same general exterior form and dimensions but turned from eucalyptus wood and treated with linseed oil. The iron pins and eucalyptus pins are entirely interchangeable in all parts of the construction.

The insulators are of dark brown glazed porcelain, a small portion being furnished by the Locke Manufacturing Co. and the greater portion by R. Thomas & Sons, Fast Liverpool, O. The insulators are a special design adopted after tests on a number of samples of varying design. The insulator consists of a broad umbrella shaped top 14 in. in diameter and three inner shells cemented together and to the iron pins by neat portland cement. They weigh about 22 lb. and stand a potential of 90,000 to 100,000 volts before arcing over under an artificial rain test. The separate parts of the insulators were given a dry potential test at the factory before shipment, and after assembly in Tacoma and before shipping out on the line they were again tested to a potential corresponding to the dry arcing over voltage. So far the behavior of these insulators under the weather conditions that have existed since the plant was put into operation and under a line potential of 55,000 volts, has been entirely satisfactory.

The line wire on both lines from the power house to Bluffs and from Bluffs to Seattle is 19-strand No. 0000 semi-hard drawn copper cable, and from Bluffs to Tacoma is solid No. 0 semi-hard drawn copper wire. The wires are transposed, making a third of a turn about every four miles.

The telephone line is supported on cross arms 7 ft. below the main arm and consists of two No. 10 hard drawn copper wires, transposed every tenth pole, the glass insulators being double petticoat deep groove on locust pins. The operation of the telephone line with this construction has been entirely satisfactory. The company also has an independent telephone line leased from the Sunset Telephone Co. and constructed over another route.

 

Sumner and Puyallup.

 

Eighteen miles from the power house and along the transmission line from the power house to Bluffs is the town of Sunnier. In Sunnier has been built a sub-station to accommodate two 100-kw. 50,000 to 2,300-volt transformers for local power and lighting. At present only one transformer has been installed, furnishing current for lighting Sumner.

A 2,300 volt line will be built from Sunnier to Puyallup, a distance of three miles, for supplying the city of Puyallup with current for lighting and power, taking the place of the steam plant at present in operation.

 

Massachusetts St. Sub-Station.

 

The receiving station in Seattle is built on Massachusetts St. near the southerly city limits. Here the high tension current is stepped down to 2,300 volts for local distribution to the stations of the Seattle Electric Ry. Co. Control is provided for the two incoming high tension lines by means of high tension motor-operated oil switches, and for two 4,000-kw. banks of transformers and for three outgoing 2,300-volt feeders. The control of the transformers consists of a motor-operated 60,000-volt 400-ampere oil switch on the high tension side of each bank of transformers and a motor-operated 2,500-volt 4-pole oil switch on the low-tension side of each bank. The control of the 2,300-volt outgoing feeders is by motor-operated 4-pole oil switches similar to the transformer low tension switches, differing only in capacity, the former being 800-ampere and the latter 1,200-ampere capacity. All of the oil switches have time limit relays for automatically opening the switches in case of overload or short circuits. There are installed four 2,000-kw. transformers in two banks of two each, transforming from 50,000 volts three phase to 2,300 volts two phase. The arrangement of the winding is such that 50,000, 40,000 and 25,000 volts can be used on the high tension side, and low tension voltages of 13,800, 6,900 and 2,300 volts may be obtained. The two transformers constituting a bank are connected T but using the full winding in the teaser transformer rather than 87 per cent as in the usual Scott three-phase-two-phase connection. This produces only 1,990 volts on the low tension side of the teaser transformer with 2,300 volts on the main transformer, and in order to boost this to normal a 200-kw. transformer called a compensator having the full ampere capacity, in the boosting coil, of the 2,000 kw. transformer and ratio of transformation of 1,990 to 310, is installed. This makes it possible to admit all 87 per cent taps on the high tension winding of which there would be a number, for the three primary voltages above stated, and simplifies the transformer construction.

 

HIGH TENSION WIRING AND DISCONNECTING SWITCHES - MASSACHUSETTS ST. SUB-STATION, SEATTLE.
High Tension Wiring and Disconnecting Switches - Massachusetts St. Sub-Station, Seattle.

 

All the transformers, including the compensators, arc water cooled, the water for cooling being primarily derived from the city service, but recooled by a cooling tower to effect economy by the reuse of water.

There are in addition to this apparatus two 500-kw. transformers in this station with a ratio of transformation of 25.000 to 2,200 volts installed for connection to the transmission line of the Puget Sound Electric Ry.

For measuring the input of power into the 2.3.m-volt busses a graphic recording- -voltmeter, ammeter and wattmeter are provided in addition to the integrating wattmeter.

Lightning arresters identical with those at the power house are provided for each of the incoming lines. Marble barriers between adjacent poles of the arresters are installed to prevent the traveling of an arc from one leg to another.

Four-pole static dischargers are installed on the low tension side of each transformer bank, their purpose being the same as those at the power house.

For controlling the voltage of the 2,300-volt outgoing feeders there is installed in each feeder a motor-operated induction regulator each of a capacity of 340 kw. These regulators boost or lower equally each leg of each phase.

 

Seattle Electric Co's. Distribution.

 

The power is transmitted at 2,200 volts, two phase, from Massachusetts St. sub-station to Post St. station and from there also at 2,200 volts two phase, to James St. station and Fremont sub-station.

Post. St, station contains nine 500-kw. rotary converters each with two 300-kw. transformers, five giving 500-volt current for railway and four 250-volt current for lighting, also six 50-kw. tub transformers for street lighting. This station is a steam relay station and contains two 2,500-kw. overload capacity, 60 cycle, 2,200-volt, two phase, alternators, each driven by a vertical compound engine, also a 1,000-kw. lighting and a 500-kw. railway battery. The station contains the general switchboard for controlling the whole distribution in Seattle.

James St. station contains two 300-kw. induction motor generator sets giving 500-volt railway current. It is also a steam relay station with three 150-kw. railway generators driven by a double corliss engine. When operated on a water power basis the railway generators are used as motors to operate the James St. cable road.

Fremont sub-station contains two 300-kw. motor generator sets, one induction and one synchronous, the motor end of each being 2,200-volt, two phase and the generator end 500-volt direct current. There is also installed a 300-kw. railway battery.

The Seattle Electric Co. has in addition to these, two steam relay stations not used as sub-stations. These are equipp