The First Three-Phase Transmission Plant in the United States

The first water power in Southern California to be utilized for the distribution of power, as well as lights, is that situated at the mouth of Mill Creek Canon, nine miles from the city of Redlands, one of the most flourishing of the younger cities of the State. Less than two years ago a few of the public spirited citizens of Redlands saw the chance of utilizing the fine Mill Creek power and organized a company, and the enterprise was rapidly pushed forward and about nine months ago a contract was closed with the General Electric Company for the necessary apparatus.

Mill Creek is a fine and unusually reliable mountain stream that springs from the slopes of mountains San Bernardino and Grayback, the two loftiest of the Sierra Madre range. The main body of the stream and a convenient intake were found near the mouth of the canyon and, by a comparatively small deflecting dam of masonry 40 feet long and head works it was possible to turn the water into a tunnel 160 feet in length, cut through the rock, and thence into a heavy steel pipe line, which was brought down the stream a distance of 7,250 feet, where was obtained a convenient site for a power house. At the end of the tunnel is a sand box 75 feet long by 25 feet wide to catch any sediment before the water can enter the pipe line. At this point the fall is in the neighborhood of 353 feet, giving exactly 160 pounds pressure to the square inch in the receiver that terminates the pipe line, which can deliver 2,400 cubic feet of water per minute.

The power house is for the most part an excavation not far from the bank of the creek. The roof is erected on very low side walls and under the lean-to, on the right. is the wheel pit with the receiver and Pelton wheels. The wheel shafts extend through iron shutters, set in windows in a massive rubble retaining wall that bounds the wheel pit into the dynamo room, where they are directly coupled to several machines. This dynamo room contains the following apparatus, as may be seen from the cut, which gives an excellent view of its interior: Two 250-kw. ten-pole three-phase generators delivering current directly to the lines at 2,500 volts between lines: two D-10 exciters, each capable of energizing the fields of both generators, and one 50-light, 2,000-c. p., ThomsonHouston are dynamo. With the stream at its lowest 800 h. p. is developed at the generators. Room is left and foundations are in place for a third three-phase generator and a second similar are machine. The large generators run at 600 revolutions, give 6,000 alternations per minute, and have a rated output of 100 amperes at 2,500 volts. The general arrangement of the station was planned before the contract for the apparatus was let (and in fact, before the character of the machinery was determined) substantially according to the designs of the late A. W. Decker, whose recent death was a serious loss to the electrical interest of the Pacific Coast.

To each of these large machines just mentioned a Pelton wheel is directly coupled, the three-phase generators being supplied with 200-h. p. double wheels, each operated by a double nozzle.

The regulation of the hydraulic power is by the ordinary differential nozzle operated by Pelton differential governors driven from one of the exciter shafts. A second small differential governor, driven from the other exciter shaft, steadies the action of the first by regulating the exciter wheels. The water having done its work is discharged into a ditch and utilized for irrigation purposes.

On the side of the dynamo room opposite the dynamos are located the switchboards. The chief interest of these lies in the three-phase switchboard for the two big generators. This is elaborately devised to meet every condition or combination that it might be desired to make with the two machines, and the two circuits that run from the power house. Either machine can be thrown on either circuit and both machines in parallel on either or both circuits. At present the parallel connection is chiefly used in shifting over the load to obtain perfect continuity of service. A six-ton traveling crane permits ready handling of any of the machinery. The interior of the station is a model of its kind. Particularly to be noted are the excellent foundations, and a result is an excellent alignment of shafts, the large generators running without even a tremor at the bearings.

From the power house are run two three-phase circuits, each composed of three 00 B. & S. wires. One of these runs to the company's office at Redlands, a distance of seven and a half miles, and from thence is distributed over the city for lighting and power purposes. On a substantially built pole line the other extends to Mentone, four and a half miles, where is located the artificial ice plant of the Union Ice Company.

In this plant is installed a self-starting 150-kw., triphase, 750-revolution, 6,000-alternation synchronous motor, belted through the medium of a countershaft to two large compressors for the ammonia, a circulating pump for the compressor jackets, a force pump to supply water for the ice, and a small elevator for handling the ice. In order to ascertain the point of synchronism, a Thomson acoustic synchronizer is employed, and gives unqualified success. The ice plant is of the so-called "pipe" type, and the freezing room and condenser contain nearly 20 miles of three-quarter inch iron pipe, in testing which the motor was stopped and started at short intervals for several weeks. The operation of the ice plant is continuous, the load being on the motor 24 hours a day, and, barring accidents, 365 days a year, The motor plant at this point is likely soon to be increased to keep up with an increase in the plant.

From the main Redlands circuit a number of lines are taken off from the ice plant and also for the neighboring town of Mentone. There are now in operation 30 arc lamps, besides over 1,000 16-c. p. incandescent lamps distributed over three legs of the circuit. A number of small induction motors without commutators or collecting rings are to be installed before the beginning of next year, to meet the demand already created by the success of the plant. The transformers are very similar to the ordinary General Electric type of transformer, except that they are designed for 50 cycles per second, and to reduce the pressure from 2,200 to 110 volts. So far as possible rather large transformers are used with comparatively long secondaries. These are used only directly at the point where light and power are delivered.

No trouble whatever has been experienced from any unbalancing of the lighting lines. In fact, shortly after the plant was started up the largest single block of lighting in the city, wired for three circuits, had these circuits worked for several nights on two legs of the triphase generators pending the setting up of the third transformer; and, although the lights from these two legs were set in adjacent rooms where both would be seen at once, not the slightest trouble from unbalancing was evident.

The first generator reached Redlands Sept. 1, and Sept. 7 incandescent lamps were turned on in Redlands, where are lamps had been previously working since the latter part of July. Sept. 13 the motor at the ice plant went into commercial operation. The whole plant has been running steadily and doing good service ever since.