Electric Power At Bingham, 1940

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Role of Electricity in the Utah Copper Enterprise

Mining Congress Journal. May 1940, page 12

(Note: The power ratings of some electrical equipment are expressed in kW, or kilowatts; and some are expressed in kVA, or kilo Volt Amperes. Both values express power, but they are actually different. kVA is known as the "apparent power" of a particular circuit or electrical system. In direct current circuits, kVA is equal to kW, because voltage and current do not get out of phase. However, "apparent power" and "real power" (which is expressed as kW) may differ in alternating current circuits. kW is simply the amount of actual power that does valid work. Only a fraction of kVA is accessible to do work, and the rest is an excess in the current.)

The methods of mining, purifying, and fabricating of copper are among the oldest of the arts, but, from the very beginning, inefficiencies were so obvious as to indicate continuous improvements in the crude appliances and methods of that early time. As new occurrences of copper ores were discovered and developed, and the metal became more plentiful, competition increased correspondingly, resulting in many notable and some startling betterments in practices, and, as in other progressive industrial pursuits, most advances in process required more motive power.

Power Requirements for Mining, Transporting and Concentrating

Power requirements of the Utah Copper Company may be roughly divided between digging-loading, transportation, and concentration of ore.

The digging and loading operation at the open-cut mine at Bingham is performed by 29 electric shovels. Most are of the standard railway type, and the remainder are the full-revolving model, both using caterpillar traction. All shovels are equipped with 4-1/2-yard dippers.

Transportation of ore from the pit to the mine's assembly yards is performed by a fleet of 61 electric locomotives, each of which weighs approximately 85 tons.

Transportation of ore from the mine's assembly yards to the concentrators is handled by the ore delivery department over an 18-mile, single-track railroad having six passing sidings. For this service, nine mallet-type steam locomotives, weighing approximately 315 tons each, are used. Automatic block signals, together with a centralized traffic-control system, serve to direct all train movements.

Main line assembly yards are located adjacent to the concentrators, and haulage therefrom to the car dumpers at the mills is performed by two electric locomotives weighing approximately 80 tons each.

Two concentrators, known as the Magna and Arthur mills, receive ore from the mine for concentration. Both use practically the same flow-sheet, and in many cases identical equipment. The basic process consists of dumping, crushing, and grinding the ore; thickening the pulp and floating the valuable minerals, and de-watering and loading the concentrate. All equipment used in these various processes is electrically driven and constitutes the major electrical load.

Growth of Power System

Power for the original Utah Copper Company enterprise was generated in a steam plant built for this purpose. This plant had an installed capacity of 8,500 kilowatts (kw) and supplied power to the Magna plant and the Bingham mine. After acquisition of the Boston Consolidated Mining Company's property, which included the Arthur mill, the power problem became one that was, for that period, quite serious, inasmuch as increasingly large tonnages had to be treated to promote maximum economies and revenues. This large contemplated tonnage required much more power than could be economically generated by the original power plant; consequently, this plant was abandoned in favor of purchased hydro-electric power.

It is interesting to note the growth of the primary power system during the 33 years between the use of the original 8,500-kw. plant, then considered adequate, and the present 62,000 kilo volt amperes (kva). power requirement which has been hardly sufficient during high tonnage periods since 1929.

Jump in Secondary System Equally Spectacular

Growth of the secondary system has been equally spectacular and interesting. The original Magna mill substation, equipped to handle 5,250 kva., has been replaced by four sub stations having a total capacity of 29,850 kva.

The first substation of the Arthur mill had an installed capacity of 3,000 kva., which has been increased to 12,000 kva., and is now supplemented by two substations, the three having a combined capacity of 24,375 kva.

When mining operations were commenced, the "G" level substation at the mine had a capacity of 1,950 kva., which has been replaced by two combination shovel and railway substations with a total installed capacity of 14,400 kva.

364 Million KWH Maximum Yearly Consumption

From a power plant originally designed to furnish approximately 75,000,000 kilo watt hours (kw-hr) per year, power consumption has increased to a maximum of 364,000,000 kw-hr per annum, while yearly tonnages have increased from 6-1/2, to 23 million.

Practically all prime movers at the concentrators use alternating current, while at the mine the direct-current haulage system constitutes about half the power load. To furnish power for this entire industry, as it is now operated, required the installation of 62,000 kva. in transformer capacity. These transformers are located at a central receiving station adjacent to the Magna mill.

Generating, Transmitting and Transforming the Power

Power received from the Utah Power and Light Company's system is generated in hydro-electric plants in Idaho and Utah, supplemented by two steam-electric plants located in Utah. Transmission lines from the various generating plants terminate at the power company's central receiving and regulating station located about 7-1/2 miles northeast of the Utah Copper Company's concentrators.

Power from the Idaho system is transmitted a distance of 135 miles at 130,000 volts and is received at approximately 120,000 volts. These lines terminate in a common bus, and voltage regulation is maintained by synchronous condensers. From this common bus, two lines, each. 7-1/4 miles long, owned and operated by the Utah Copper Company, transmit power to the central receiving station. Here it is transformed from 120,000 volts to 44,000 volts by three transformer banks. Each mill is served by a 25,000-kva. bank and the mine by a 12,000-kva. bank.

Transformer banks, primary oil circuit breakers, and lightning arresters are installed outside; while the secondary oil circuit breakers, control and metering equipment are located inside the central receiving station building.

All primary lines and transformer banks are arranged for parallel operation. Secondary feeders are taken through a ring bus provided with sufficient sectionalizing switches to permit maximum flexibility.

Minimizing Delays from Power Interruptions

Continuity of service is a vital necessity in an operation of this kind; therefore, rather elaborate precautions are taken at all stations to provide spare equipment that can be quickly placed in service in an emergency. A well-trained operating crew is on continuous duty at the central station and has direct charge of all switching operations.

Power interruptions are handled with minimum delay to operation by means of a special communicating system between the central station and all substations.

Secondary energy from the central station ring bus is distributed over two-circuit steel-tower lines to the principal substations. Each of the mills and the mine receive power at two substations. At the concentrators the 44,000-volt energy is transformed to 440 volts and distributed through three conductor cables to the various load centers.

At the mine the 44,000-volt energy is both transformed and rectified. Each of the shovel substations has a capacity of 2,4000 kva. divided between two transformer banks, which reduces the 44,000-volt energy to 5,500 volts for transmission to the electric shovels. The railway substations, which are of the full automatic type, have a capacity of 4,800 kva. each. The 44,000-volt energy is transformed to approximately 565 volts, and rectified by means of four 1,000-kw. synchronous converters, to 750 volts direct current for distribution to the trolley system.

The cost of power for the Utah Copper Company enterprise represents the second largest item of classified direct operating expense, and is said to require approximately 40 per cent of the Utah Power and Light Company's widespread hydro-electric output.

The progressive attitude of the management toward electrification has resulted in many economies otherwise unattainable.