The Telluride Power Company

Development of High-Tension Transmission Line Insulators


Publication: The Telluride Journal

Telluride, CO, United States
vol. 24, no. 28, p. 2- 3




A Historical Record of its Origin and Development That "Is

As Interesting as the Traditional Romance of

Much Historical Value and of High

Technical Worth."

A paper read before the International Electrical Congress, at St. Louis, by Mr. P. N. Nunn,

chief engineer of The Telluride Power Company.

During the winter of 1890, the year preceding the famous Frankfort-Lauffen experiment, apparatus was installed for the first commercial, high-pressure, alternating-current power transmission of the world. From that beginning has grown The Telluride Power Company.

The mining district surrounding Telluride, San Miguel county. Colo., is at the same time one of the most rugged and one of the richest in the Rocky Mountains; but its inaccessibility and the consequent cost of producing power caused the financial failure of many important enterprises in the early days of its history. The statement made in the Annual Report of the Treasury of the United States, in 1901, that "For the growth of its mining industry, San Miguel county is indebted to the Telluride Power Transmission Company more than to any other agency." is borne out by the fact that at the present time all of the important mines and mills of the district are operated by power furnished by this company.

The Gold King mill, situated at an altitude of 12,000 ft., where the cost of fuel for steam power had become prohibitive, was the first to be operated by means of this power. This property had been attached in 1888 to satisfy a continued deficit in operations. Mr. L. L. Nunn, the attorney retained by the owners, found that this deficit was largely due to the enormous cost of power, and that there would have been a handsome margin if power could have been furnished at not more than $100 per hp-year. Down in a deep gorge of the valley, over 2000 ft. lower, but less than three miles away, two mountain streams formed at their confluence the South Fork of the San Miguel river, offering cheap and continuous power. A stay of proceedings was secured; and, as a means of transmitting this power, cable drive, compressed air and continuous-current electricity were all investigated. The limitations of each were apparent, while the advantages of alternating current and higher pressures became gradually recognized, and a decision was reached to attempt their use. This decision was due less to the immediate saving in copper, than to a keen sense of the limitation of continuous current, and faith in the final success and ultimate superiority of alternating current.

During the investigation which followed and while selecting apparatus, little but incredulity or ridicule was encountered. Eastern investors in the enterprise were annoyed by predictions of prominent engineers, and discouraged by their insistence, that the experiment would prove a miserable failure and the expenditure go for naught. It was said that there was no alternating-current motor, that oil insulators must be used, and that the line must be fenced in. However, a generator and a motor for 3000 volts and of 100 hp. each were ready for trial in the fall of 1890. Difficulties caused by ice at 40 deg. below zero, by speed control over unusually high water pressure, by avalanche, by blizzard, by electric storms unknown in low altitudes, and many other troubles, now generally forgotten, but then most serious, marked every step of progress. Notwithstanding all of these. unqualified success from the beginning caused gradual and constant growth, until at the present time the Telluride company and its allied industries have six power stations and nearly a thousand miles of line in Colorado, Utah, and Montana.

Following its pioneer power transmission, it made practical experiments as early as 1895 with pressures which have never, even yet, been exceeded, and for three years it operated commercially the highest pressure transmission of the world. Thus the record of its work becomes an important chapter in the history of power transmission; but it must readily be seen that the limit of this paper precludes the possibility of describing all, or even a substantial part, of its pioneer work.

The initial installation, purchased through Mr. F. B. H. Paine, comprised a generator installed in a rough cabin upon the site of the present Ames station and belted to a 6-ft. Pelton wheel under 320 feet head, and a motor at the mill 2.6 miles distant. The two were identical Westinghouse single-phase alternators of 100 horse-power, the largest then made. The generator was separately excited, while the motor was self-exciting. Each carried a 12-part commutator and was slightly compounded through current transformers upon opposite spokes of the armature. The latter were ironclad or "T"-toothed, wound with 12 simple coils in cells of fullerboard and mica. Switchboards were matched and shellaced [sic] shellacked pine sheathing, and the bases of instruments were dry hard wood. Only voltmeters and ammeters were used, both of the solenoid and gravity-balance type, in black-walnut cases with window-glass fronts. Circuits were closed with jaw switches and opened by arc-light plugs. The line carried two No. 3 bare copper wires, mounted upon short Western Union cross-arms and insulators. The copper cost about $700, or about 1 per cent of the estimated cost for continuous current.

The main motor was brought to synchronous speed by a single-phase induction starting motor, which received its current at full line voltage. The current taken was more than full-load current of the main motor. This starting motor, even, required starting by hand, its torque being zero at starting, and so feeble at low speeds that when cold it could only with the greatest difficulty be persuaded to pull up to speed its belt and loose pulley. Nor could it at speed start the main motor without help, and even then it became so hot that its short-circuited secondary frequently burned cut.

Another motor of 50 horse-power was soon added. While in other respects similar to the first, this motor was intended to be self-starting, with armature and field in series through a current transformer; and on account of its frightful flashing, it was fitted with a special eight-part commutator of non-arcing metal. This feature, however, proving a failure, was soon replaced by a separate starter.

The need of a wattmeter or power-factor indicator not having been at that time recognized, the motor field charge was adjusted for least main current. This current was accepted as having unity power factor, and, therefore, as the measure of actual power.

Everything was extremely simple from water wheels to motors; and, except for lightning, the plant ran smoothly and steadily 30 days and more without a stop. The report made in the East by associates of the enterprise that at Telluride 100 horse-power was being successfully transmitted nearly three miles over No. 3 copper, wires with less than 5 per cent loss, was received with the utmost incredulity.

During the autumn of 1892, a 600-hp generator of the same characteristics was installed, and a 250-hp motor for the mill on Bear Creek, 10 miles from the generator. Early in 1894, a 50-hp, and during the fall, a 75-hp motor were placed in Savage Basin, 14 miles from the power-house. The former was soon replaced by a 100-hp motor, and in 1895 a 100-hp motor was set up at Pandora.

Except as to size these motors were substantially identical. The 250-hp motor was badly designed, and the pole pieces were of cast-iron. Its starting motor was insufficient, and was, therefore, soon replaced by one having split-phase secondary with external resistances. Marble with brass trimmings replaced wooden-base instruments, and such elegance demanded highly-polished slat switchboards of paraffined oak. Imposing marble rheostats were mounted-at switchboards like keyboards upon grand organs. Fuse blocks, the only protective device, became marble slabs with duplicate aluminum strips. The first synchrophone came with the 75-hp equipment.

Owing to its altitude and geographic position, the Telluride district is peculiarly subject to atmospheric disturbances. Over 100 distinct discharges have been counted within a single hour, and lightning caused more discouragement than any other obstacle. A neighboring continuous-current plant, transmitting a little more than a mile. carried several extra armatures ; and even then it was so frequently compelled to close down during the daily storms of the rainy season, that the company was eventually bankrupted. The alternating plant might have suffered a similar fate had it not been for its "T"-toothed armatures and replaceable coils, eight of which were successively burned out and replaced on one motor within a single week. To get a coil into place, and its oak keys driven home, required such bending, clamping, and pounding as inevitably resulted in injury to insulation, and only by the greatest care could replaced coils be made to stand a test adequate to the 3000 volts employed. For protection from lightning, several types of manufactured arresters, then various original devices were tried, ending with a simple gap in series with a score or more of fuse blocks in parallel, arranged about a radial commutator switch, turned from point to point as the fuses were blown by successive discharges. From the first these conditions caused the greatest apprehension as to the commercial success of electric-power transmission, until Mr. Alexander J. Wurts, during a stay of several months with the company, gave the protection of the now well-known non-arcing arrester.

No transformers were used between machines and line, the largest transformers at first being 2-kw, or 40-light. Aside from the effects of lightning, even to-day 3000 volts upon the winding of small highspeed armatures requires first-class insulation. Frequent grounds were prevented by deep insulating foundations of paraffined wood. To prevent short-circuits within the coils, their cells, just before placing, were poured full of shellac, and the entire armature afterward baked for several days. By this means the 50-hp motor ran a full year without trouble in a room dripping with moisture.

A lighting transformer received in 1891 was rated at 5 kilowatts. Theretofore transformers had been rated in lights, and generators in horse-power. This transformer was immersed in engine oil, and marks an epoch in the company's history. Lightning frequently punctured it, causing its fuses to blow, but without other apparent injury. It remained in service for years. All others were soon likewise immersed. Four 500-light, dry Stanley transformers, purchased in 1892 for lighting Telluride, were broken down by the thunder storms of the following spring. When repaired these also were immersed in engine oil, and gave no further trouble during the three years they remained in service.

Alternators were paralleled at Telluride in the spring of 1893, and thereafter they were so operated with full load upon the smaller, and regulation upon the larger machine.

Manipulation at switchboards or at brushes involved direct handling of 3000 volts, a rather high switchboard pressure even now. It was a rule that every attendant keep one hand in his pocket while working with the other. It is pleasant to record that during these years no loss of life and but few accidents occurred.

There being no other circuit-breakers, it was necessary, when a motor dropped out of step, to break the circuit with the single arc-light plug. This always drew a heavy, vicious arc, which on the big motor frequently held to the full length of the 6-ft. cable, and then sometimes required a whiff from the attendant's hat. When not broken promptly it frequently involved the entire switchboard and shut down the plant.

Duties of this nature required considerable skill and cool heads, and in order to operate the plant continuously, night and day, fifteen or twenty competent attendants were required. To fit young men for these positions a course was arranged during which they were taught something of machinery, of shop-work in metal and wood, and of wiring, insulating, and repairing, while receiving such assistance in daily study as conditions permitted. A technical library, including the electrical papers, and a conveniently-fitted testing-room were always open. Each student was then given a short laboratory course in graphic treatment of alternating-current theory. This is said to have been the first systematic effort made by a corporation to train its employees for responsible positions.

Although the plant as a whole was an unqualified commercial success, no explanation need here he made as to why it was replaced by the induction system as soon as the latter had been perfected. This marks the limit of the most extensive single-phase, synchronous plant ever operated. With but one or two motors its operation was not difficult; but each motor added to the system brought increased demand for care and skill. The causes of difficulty were not understood then as now, nor was the effect of power factor fully appreciated. Lack of both wattmeters and power-factor indicators left the adjustment of field charges to the judgment of the operators. The power factor of each motor being dependent not only upon its own adjustment but upon that of all, the closest attention and co-operation were necessary, in marked contrast with the simplicity of operation of induction motors. Disturbances due to starting motors were especially trying; and the unqualified success attained, notwithstanding defects of apparatus and system, is attributed now, far more than then, to the skill and vigilance of the operators in this new and fascinating field.

The Tesla system, substituted for the synchronous in 1896, comprised two 600-kw, 60-cycle, 500-volt, two-phase generators, direct connected to wheels under 600 and 900 feet head, respectively, and an equal capacity of raising and reducing transformers and of two-phase, 220-volt induction motors. The 12 100-kw, step-up transformers were connected in pairs, two-phase—three-phase, for three-phase, 10,000-volt transmission. These transformers were worthless; all broke down within a year, and one or more were always undergoing repairs. Break-downs occasionally caused sufficient explosion to lift a cover, or splash the oil. The woodwork soon became saturated, and hot metal from the near-by main fuses frequently started fires, endangering the wooden power-house. A masonry transformer-house in two compartments was, therefore, constructed, and into it the transformers were moved, — this being the first known case of isolation of oil transformers on account of fire risk.

The power-house at Ilium, situated six miles below Ames on the same stream and using the same water, was built in 1900, and contains one 1200-kw, revolving-field, General Electric generator, direct connected to two impulse wheels under 500 feet head. Transmission lines extend both to the Ames station and to points of distribution, providing the insurance of duplicate transmission. Any section of line can be cut out for repair, or either power-house shut down, without interrupting the service. Junctions, other than generating and distributing points, are equipped with open-air switches, mounted upon standard line insulators and operated from platforms similarly insulated, and have proven invaluable.

Junction-houses at distributing centers provide for a branch line to each customer, which is equipped with switches, fuses, and a set of five record-making instruments — a voltmeter, 2 ammeters, and 2 wattmeters. The power company thus secure upon its own property a continuous, accurate, and satisfactory record of each load.

The long spans crossing canyons and divides surrounding Savage .Basin may be worthy of note. These divides are bare ridges at an altitude of 13,000 ft., inaccessible in winter and swept by frequent snow slides. Spans up to 1150 ft. are used in order to reach safe points for supports. A number of these supports, although simple and inexpensive, have stood for years without repair. The longest span is of No. 1, hard-drawn copper, supported by 4-in. plow-steel cable, both being carried by the same insulators. The deflection is approximately 35 ft. on a slope of 31 deg. Another is of Fin. soft-iron cable 1120 ft. long, and has been in service five years. A third, 660 ft. long, is of hard-drawn copper only, having 25 ft. deflection. The strain insulators in all cases are a series of the usual line insulators and pins upon a longitudinal arm hinged to permit adjustment to span motion. They are simple, inexpensive, and entirely successful.

A 10,000-volt, underground transmission was put in operation at the Gold King mine in 1896. Power was carried through an unused tunnel 1300 ft. long, upon bare copper conductors 12 in. apart on standard line insulators, to a deep mining hoist equipped for electric power. The tunnel was always dripping with water, but no trouble was experienced during the several years of operation, although slight brush discharge or halo was at time