This year, we celebrate a half-century of serving our electric-utility readers. The pages that follow document the highlights of major (and minor) technological developments in how our readers and their equipment suppliers brought progress to our industry. Sometimes getting an appropriate article has been frustrating, but, most of the time, it has been a whole lot of fun. We hope you enjoy this retrospective. The Editors
The 1950's... The Early Days of Transmission & Distribution With safety as a leading concern, most of the changes in our industry discussed in this decade's report are dedicated to better practices in line construction, including hot-line tools, helicopters and aerial devices. Progress in SF6 technology is shown in a new 230-kV circuit breaker, and the importance of good communication during both construction and system control is emphasized.
Safety Gets Major Consideration In the decade of the 1950s, a major step toward safety was reported in our October 1956 issue from World War II when safety hats worn by defense workers saved lives and prevented many injuries. At that time, Edison Electric Institute statistics revealed that approximately 8% of all contact fatalities were caused by head contacts. C.P. Shirey, system safety director, Gulf States Utilities, reported that his utility offered safety hats of reinforced plastic to employees all over the system on a trial basis. While some workers accepted them gladly, the majority found them too hot or too cold or heavy and uncomfortable. Now, however, they are standard gear.
Tension Wire Stringing Increases Previously used principally in stringing high-voltage transmission conductors, greater interest in tension stringing emerged in the 1950s. This was the preferred method from the standpoints of greater safety and lower costs for two general classes of work: jobs requiring an overhead pulling-in line and most reconductoring jobs. Use of such equipment resulted in an estimated savings of 25% in labor.
Vehicle Radios Hit the Scene In an article from 1956, E.A. Schultz, manager of electric operations, Illinois Power Co., discussed mobile radio for utility maintenance work. At the time, Illinois Power organized its radio system on a local service area basis with a central base station in each of the 15 service areas functioning as the controller for construction, line and trouble trucks in that sector.
"Radio makes the trouble men more conscious of their personal safety," Schultz said in the article. "Prior to getting two-way sets, the troubleshooter working alone used to fight the tough situations single-handedly, rather than leave the job to hunt down a telephone and call for assistance. Now they play it smart and radio the dispatcher for help from the nearest crew when they need another man".
Fiberglass Hot-Line Tools Take Center Stage Shortly after World War II, wood poles were introduced with a thin layer of plastic coating extruded over the wood. And, in 1954, Boden-dieck Tool Co. introduced tubular fiberglass hotsticks that were 5% lighter than wood, 20% to 30% stronger, and more resistant to abrasion and moisture absorption. According to the article, fiberglass dielectric was 25% greater than that of wood. Because of these excellent characteristics, fiberglass swiftly grew in popularity.
Helicopters Key to Construction Success In the April 1958 issue, the article "Flying Crane" described the history-making job that used a helicopter as the sole means to hoist and set poles for a 12-kV line that ran along inaccessible mountain ranges in California. Veteran Southern California Edison Co. line crews shook their heads in amazement as a Sikorsky S-58 helicopter planted 63 30-ft (9-m) wood poles, complete with crossarms, insulators and hardware, along an almost 3-mile (4.8 km) stretch on the 4200-ft (1280-m) Santa Ynez Mountain in less than two days. Normally, such a project would have taken more than two months. The helicopter gently lowered each pole into a previously dug hole while the ground crews who had dug the hole, fitted and tamped it, and the helicopter returned to the loading yard for another pole.
Capacitor Control Via Powerline Carrier In our April 1959 issue, D.D. Milne, engineer, Communications and Industrial Electronic Division, Motorola Inc., described how individual capacitors could be controlled from a substation to raise or lower the feeder voltages.
A large eastern utility built the proposed substation and added switched capacitors to its feeders. Repackaging a Motorola Handie-Talkie Radio Pager in a watt-hour meter housing for outdoor use made up the control device. Its receiver output was used to drive two Vibrasponder frequency-selective relays. It then remained to devise a substation control unit that would initiate and transmit the proper control tones in the proper sequence and, at the right time, to maintain uniform bus voltage.
High-Voltage SF6 Circuit Breaker Announced A sulfur hexafluoride (SF6) circuit breaker designed for 230 kV, 15,000 MVA, was presented in our June 1959 issue by R.E. Friedrich, section manager in power circuit engineering, and R.N. Yeckley, Westinghouse Electric Corp. The unit's development followed the first circuit interruption of SF6 in a load-break switch developed in 1953. Subsequently, a 115-kV, 1000-MVA power circuit breaker was developed in 1955; a five-cycle grounding switch in 1956; and a 46-kV, 250-MVA power circuit breaker in 1957.
Among the breaker's advantages were quiet operation, elimination of fire hazard, light foundation requirements, minimum auxiliary equipment and the elimination of any portions under high pressure.
Wide Reach Aerial Devices Extolled A photo of a two-bucket aerial lift being used for mid-span repair of a gunshot transmission line conductor appeared in our August 1959 issue. Without a closer look, it appears quite similar to 1999 aerial lifts.
D.K. Wilson, director of transportation, Niagara Mohawk Power Corp., discussed the high degree of flexibility and productivity available with aerial equipment. Older and more experienced men who were not physically able to climb day in and day out could continue to perform top-skilled work through the use of aerial apparatus.
Some of the aerial equipment pluses included streetlight replacement, tree trimming, line maintenance and repairing storm-damaged lines. In the substation, aerial devices brought bus taps and high-mounted disconnect switches within easy reach for installation and maintenance.
Prestressed Concrete Poles Arrive In America The first transmission line built in the United States using prestressed concrete was undertaken at Florida Power Corp., reported F.R. O'Brien, head of engineering and metallurgy at Southern Research Institute, in January 1957. This structure was designed and built by Finfrock Industries of Orlando, Florida, U.S., in conjunction with Florida Power Corp., which had been quite active in the design and use of reinforced concrete poles.
The potentialities of prestressed concrete as an engineering material had not been realized. All who reported on its use in pole structures remarked on its ability to withstand severe loading and deformation without cracking. The material was so different from ordinary reinforced concrete that new concepts of design had to be developed.
The application of prestressing procedures to the construction of concrete poles was suggested as a means of reducing weight and overcoming the disadvantages of cracking and spalling, which were noticeable in many reinforced concrete poles. Prestressing was ordinarily brought about through the tensioning or stretching of high tensile strength steel in the form of wires, straps, cables or rods. Concrete was then bonded to the steel. As it set, the steel was cut loose from the tensioning device, and the concrete was placed into compression.
Prestressed concrete behaves quite differently than reinforced concrete. It acts as a homogenous material and is very elastic. The elastic behavior of prestressed concrete is of particular interest in the design of concrete poles. The article noted that prestressed concrete generally would crack at bending moments that were six to seven times higher than those obtained with ordinary reinforced concrete.
Neoprene and Butyl Insulated Cables Replace Rubber A staff-written article provided an update on the cable practices in the mid 1950s. Rubber insulating compounds were being replaced to some extent by neoprene or butyl compounds with neoprene with resultant extensions of the former service ranges of such cables. As for conductors, aluminum was gaining in acceptance but copper, either annealed, tinned or alloy-coated, remained the most widely used conductor, doubtless due to its superior electrical characteristics and despite its (then) present scarcity and high price.
While lead sheaths remained the main protection for duct cables, the growing contamination of surface waters-particularly the increasing practice of ice and snow removal by salts of various types-posed severe corrosion problems. Hence, the popular practice was to protect lead and other metal sheaths with neoprene jackets. Similarly, another trend of metal-sheathed cables was the use of arsenical-tellurium alloys to provide better fatigue life under conditions of longitudinal expansion and contraction caused by wide swings in load factors.
Oil-saturated paper was still the preferred insulation for high-voltage, underground cables and, as such, was widely used for low-pressure gas and high- and low-pressure oil-filled cables. Some aluminum was used to sheath such installations. Another noticeable trend was the wider use of nonmetallic and semiconducting tapes and braids, which effectively shielded against corona discharges both between conductors and insulation, and between insulation and metal shield or surrounding environment.
Neoprene-jacketed cable, suitable for installation in ducts and conduit and for direct burial in the ground, was procurable for many types of service.
Relay Replaces Tubes with Transistors and Diodes Ohio Power Co. installed and tested a new relay system that responded to line-to-ground, phase-to-phase and three-phase faults on its 138-kV Muskingum-Philo line. The static phase comparison relay was designed by General Electric for use with transitory carrier current equipment to protect transmission lines from faults. It was capable of operating at speeds faster than conventional electromechanical designs. The new relay provided high-speed, simultaneous tripping of transmission line breakers for all internal faults by comparing phase relationships of currents entering and leaving a line section.
Design flexibility permitted the use of the relay on multi-terminal transmission lines. The addition of new terminals to existing lines was possible without major changes to the relaying system. High-sensitivity allowed the relay to detect lower magnitude faults and permitted heavier line loading with an equivalent protection level. The relay incorporated transistors, stabistors, diodes and reference diodes, completely eliminating the need for tubes and their related maintenance problems. All transistor circuits were equipped with positive temperature stabilization to give consistent performance over a wide range of temperatures.
The relays were operated by comparing the phase position of currents entering and leaving the transmission line section. Carrier current equipment served as the communication channel between the relays, which were located at each end of the line to be protected. The relays detected and measured the fault. Upon occurrence of a fault, local fault information was compared with remote fault information to determine if the power circuit breaker should be tripped.
Waterproof Glue Spurs Development of Laminated Crossarms At the 1958 Annual Meeting of the Forest Products Research Society, E.J. Holmes, wood products engineer with Bell Telephone Company of Canada, reported on tests and trials undertaken to address the shortage of suitable stocks of crossarm lumber.
Back in 1946, the Bell Laboratories began investigating the potentialities of laminated crossarms. They were made in three laminations of approximately equal thickness (about 1.375 inches) cut with the flat grain, and the flat grain surfaces were glued together with a resorcinol resin glue.
Some of the arms were erected in two U.S. test plots for outdoor exposure tests, 10 were installed at Chester, New Jersey, and 10 at Limon, Colorado. Five arms at each test plot were mounted in the usual manner, and five arms were loaded with 60-lb (27-kg) concrete blocks at each pin position, a total load of 600 lbs. (272 kg) per arm. After three and a half years of exposure, the arms were examined carefully, and it was found that there was less surface and end checking in the laminated arms than in standard creosoted southern pine solid arms. The glue joints were firm and, in several instances, there was evidence of weathering of the glue at the ends of the arm. The weathering extended inward not more than a quarter of an inch, and in no case was there any separation of the laminations.
All-Aluminum Substation Raised in Six Hours The world's first prefabricated all-aluminum electrical substation was erected in the spring of 1958 in Alma, Michigan, U.S., for Consumers Power Co. It took six hours to raise the prefabricated structure. As the last horizontal truss swung into the air, engineers watched critically. This truss would test the engineering precision that had gone into the structure's component parts.
The truss swung high over the gleaming aluminum lattice work, hovered momentarily, then descended slowly, maneuvering for position. Finally, it settled easily into its proper place for a perfect fit. There was no need for mechanical adjustments.
It was a perfect first use of the new substation design, known as Alrectic, that was assembled entirely from standard truss beams, fixtures and other parts made of a No. 6060-T6 alloy aluminum resulting in a built-in strength that could carry the same loads as steel.
Everything for the Alma station was assembled on the ground, including switches, insulators and controls. Ground assembly took less than one week. The aluminum's light weight eliminated the need for heavy lifting equipment. The construction crew did not have to move the single portable crane at all during the erection. After the vertical columns and cross beams were assembled and bolted together with aluminum-alloy fasteners, the crane lifted each arch onto the concrete piers where it was securely bolted. Horizontal trusses were lifted into place between the arches to form the station subwings. Once lifted by the crane, all subassemblies were pushed manually and with ease into proper position.
All aluminum parts were developed by Handley-Brown Co., Jackson, Michigan, U.S., with design and engineering assistance from Consumers Power Co. and Kaiser Aluminum & Chemical Sales Inc., Chicago, Illinois, U.S.
Pole-Top Resuscitation Although hardhats were not mandatory, that doesn't mean that lineworkers were not intimately connected with safety. G.E. Tatum, personnel and safety officer of the Department ofPublic Utilities for the city of Tacoma, Washington, U.S., reports on a method to resuscitate linemen.
Pole-top resuscitation is a method of applying artificial respiration without delay to an employee aloft who, while working on a pole, received an electric shock that suspends normal respiration. Aid can be given immediately without having to wait for the victim to be lowered from the pole in preparation for applying back-pressure arm-lift respiration. This method is, therefore, of special value in treating cases of this type because the chance of reviving the victim decreases rapidly after the first two minutes following the shock. It also should be remembered that electric shock victims sometimes recover only after several hours of effort in giving artificial respiration.
The first consideration of the rescuer is to make certain that he is not in contact with grounded wire, cable or strand before attempting to rescue a victim of electric shock who is, or may be, in contact with high voltage circuits. If such precautions are not taken, the rescuer may unwittingly become another victim.
In general, it is desirable to get the victim down from the pole as soon as it is possible to do so safely and without delay. Pole conditions and also the condition of the victim would determine the length of time resuscitation efforts should be continued before lowering. In any event, where the victim shows signs of recovery and pole conditions are favorable, resuscitation should be continued in original position on pole.
Network Analyzer Fills Room One of the world's largest network analyzers can simulate most existing electric power systems. This system has been installed by I-T-E Circuit Breaker Company in an air-conditioned room at its Philadelphia headquarters plant. Valued at more than US$300,000, the analyzer can handle all types of power system problems, including studies of load flow, short circuit effects and transient or steady-state stability. I-T-E rents the services of the huge computer-like analyzer on a daily fee basis to those wishing to simulate and thus study the behavior and equipment needs of different systems.
Consisting of three banks of 7-ft high equipment whose combined width is 50 feet, the analyzer incorporates 24 generator units, 406 circuit elements and 300 buses. New concepts and radical advances in design characterize the huge machine. Four major design advances are: control simplicity and flexibility, high-impedance base, five-degree phase-shift and automatic-adjusting load units.
An electrical network is established through use of a programming patchboard which, when plugged in, automatically connects the analyzer's elements in the manner needed to simulate the system to be studied. The board is removable and spares can be programmed in advance. The console control center, separate from the banks of analyzer racks, incorporates all metering and associated switching controls and basic power controls for the entire analyzer. Precise metering accuracy is provided through use of precision-one-fourth of 1% full scale-laboratory-type instruments and permanent, built-in shunts in each circuit. The analyzer has an impedance base of 4000 ohms and a current base of 25 mA, resulting in a voltage base of 100 V. This low-current base affords compact design without component overheating and permits greater per-unit current ratings.
Five degrees of phase shift on a Cartesian frame of reference affords apparent zero-loss reactor units. This design compensates for the unwanted but inevitable loss in the resistance components of simulated inductance units. Load units on the new analyzer automatically hold watts and vars power absorption constant, according to settings made by dial controls. No operator intervention is required to maintain a properly balanced system. All circuit elements are contained in front-drawout type drawers for complete accessibility from the front of the analyzer. Each load may be set directly in per cent watts and per cent vars.