Health, Safety & Environmental Issues of Electrical Transformers - Case Study Example

 Health, Safety & Environmental Issues of Electrical Transformers 1. Introduction Technically, an electrical transformer feature as one of the fundamental equipment used in the supply lines of electrical power. As the name suggests, the main purpose of an electrical transformer is to transform the voltage parameter of an alternating current from low voltage to high voltage and back to low voltage. Transformers are the visible equipment assuming cuboids or cylindrical shapes suspended on local power lines, and grounded on power stations. Basically, transformers vary in size and function. Large transformers are used to achieve high difference in change of voltage parameters. Large transformers are found in power supply stations and industrial settings where large power input in needed, whereas medium to small transformers are scattered around household power lines (Gill, 2008). Besides the physical size parameter, transformers can be categorized according to their primary functions. Step-up transformers convert an alternating current from low voltage to high voltage for grid distribution (Lindsey, 2006). Contrarily, step-down transformers convert alternating current from high voltage to low voltage for industrial and household application. Prior to describing the nature and functions of an electrical transformer, it is worth comprehending the basics of electricity as a source of power. In physics classrooms, P = VI, where P is power, V is voltage, and I is current. In this case, the power is a product of electrical current and electrical voltage. Electricity results from the flow of electrons from one point of a conductor to another point, otherwise known as an electricity charge. In this case, current is the rate of flow of electrons across a conductor, while voltage is the difference in electron concentration between two points of a conductor (Kathy, 2015). During the flow of electrons, the atomic and molecular structures of a conductor produces resistance in a similar manner that rocks and boulders provide resistance to the flow of water down a river stream. Basically, resistance causes loss of electrical energy. In this case, electrical resistance is a conductor’s innate tendency to object the flow of current. Conceptually, current, voltage and electrical resistance can be related according to Ohm’s Law; V = I × R. Based on the equation P = VI, it is observable that the higher the current, the lower the voltage; and vice versa. With respect to Ohm’s Law, the higher the voltage, the lower the resistance. Therefore, a high voltage is necessary in long-distance distribution of electricity, while a lower voltage is suitable in the end application of electricity (Kathy, 2015). In this regard, electrical transformers are used in changing the voltage value of an electrical power from low to high, and also in a reverse manner. 2. Basic Physical Principle behind a Transformer The basic principle of an electrical transformer is electromagnetic induction. In essence, electromagnetic induction is the relationship between electric current and magnetism. Whenever a current passes through a conductor, a magnetic force spontaneously emerges around the conductor. When a conductor is wound around a static frame, the degree of magnetism caused by the flow of electrons intensifies. In principle, the more the number of coils, the higher the strength of the resultant magnetic field around a conductor. Therefore, current flow along a coiled conductor induces magnetism. Inversely, magnetic field from a magnetic material can be used to induce current along a coiled conductor (Anthony & Smith, 2009). Essentially, a static magnet placed inside a coiled conductor creates electric current and voltage along the coiled wire. On the other hand, a moving magnet inside a stationary coil induces current and voltage along the wire. Simply put, electromagnetic induction enables induction of varying magnitudes of voltage by manipulative interaction between magnetic fields and coiled conductors inside a closed circuit. This relationship between magnetism and electron flow is the basic principle behind the functioning of an electrical transformer. 3. Description and Functions of a Transformer An electrical transformer consists of a soft metallic core, and two conducting coils wound around the soft core. One of the conducting coils is a primary conductor, which supplies electrical voltage to the transformer structure. The other coil is a secondary conductor which takes away the voltage from the transformer set-up. When alternating current from the source flows around the primary coil, a magnetic field is induced on the soft metallic core. The induced magnetic field then flows to the secondary coil and cuts across the coiled conductor. As a result, an electric current is spontaneously induced on the secondary coil, and subsequently supplied away from the transformer (Kathy, 2015). The magnitude of voltage or current induced by a magnetic field is directly to the number of windings on the primary and secondary conductor coils. In this case, more number of windings on a secondary coil compared to the primary coil yields a higher output voltage than supplied by the primary source; a set-up that constitutes a step-up transformer. Contrarily, few windings on a secondary coil compared to the primary coil yields lower voltage compared to the primarily supplied voltage; a set-up that constitutes a step-down transformer (Kathy, 2015). The sketched graphical illustrations below are examples of ideal step-up and step-down transformers. Figure i: Step-down Transformer Figure ii: Step-up Transformer 4. Manufacturing Process Production of an electrical transformer involves three basic procedures; the primary and secondary windings, development of the magnetic iron core, and assembly of the windings and the core. Besides these primary steps, other auxiliary steps involved in development of a transformer include; vacuum drying, fabrication, and tank-up stages. First, winding is achieved by twisting or coiling an excellent conductor on a spiral reference frame. A good conductor like copper is preferred for its low resistance properties (Hurley & Wolfe, 2013). Both primary and secondary windings should be performed in a gentle manner likely to reduce axial stress on the resultant coil, but with stiff tension so as to foster rigidness of the coil. After the windings, a soft core is developed. One material preferably used in construction of the core is magnetic silicon steel, a material that optimally reduces energy loss from eddy currents. Technically, the core is not a solidly compacted rod of fabricated steel. Rather, the soft core comprise of multiple plates of silicon steel laminated closely and clamped together to form a rectangular geometrical shape with visibly corrugated faces (Hurley & Wolfe, 2013). Finally, the two windings together with the core are assembled together, and necessary connections are made. Below is an image of coil winding in the process of transformer manufacture. Figure iii: Winding Process As aforementioned, the winding, core development, and assembling are basic steps in the development of a transformer. These three steps form a skeletal structure of the electrical equipment. However, other steps like structural fabrication, drying and tanking-up are essentially necessary. Fabrication involves covering the assembled skeletal core with aesthetically appealing flesh of corrugated walls (Lindsey, 2006). Fabrication not only improves the physical appearance of a transformer, but also ensures that the equipment is leak proof and air tight. Prior to performing further manufacturing steps, the fabricated assembly is first vacuum dried. Vacuum drying removes any moisture and dust particles from joints. After the drying, joint bolts and welded edges are reinforced properly. Finally, the assembly is tanked-up. Tanking-up involves filling the fabricated transformer with transformer oil. Transformer oil is the main component used to achieve cooling inside the equipment (Kathy, 2015). The oil is filled up until the entire assembly of core and coils are fully immersed. After all the basic and auxiliary steps are completed, the transformer is painted and sold, ready for installation. Below, there is an image illustrating the process of fabrication. Figure iv: Fabrication Process 5. Installation Prior to installation of transformers, proper tests and safety procedures should be performed. One of the important testing steps prior to installation is assurance of National Electrical Code (NEC) standards. NEC standards are international reference guidelines used in measuring and ascertaining the safety and performance levels of electrical equipment. In addition, transformers must be gauged according to the National Electrical Manufacturers Association (NEMA) standards. NEMA is one of the leading associations of electrical equipment safety; hence its standards are not only objective but also reliable (Kathy, 2015). Technical tests that should be performed include insulation resistance, excitation current rates, and polarity for multiple phase transformers. Other special requirement standards maintained by these safety codes include transformer’s efficiency in form of load loss, and impedance from short circuiting. All these performance and safety tests should be performed by a qualified and experienced electrical engineer. After testing and approval of the equipment, the actual installation process begins with site selection, followed by development of foundation and support structures. Site selection is a paramount element in environmental safety contexts. Transformers should be installed in locations that will not impede and endanger the normal movement of persons. In this case, transformers cannot be installed in the middle of school playgrounds or in the middle of recreational parks (Anthony & Smith, 2009). Rather, transformers are installed in remote locations, especially along fences or adjacent to empty spaces along highways. After site selection, proper soil tests should be performed. Transformers are considerably heavy; hence sites with compressible soils like clay and seismic instability should be avoided. After selection and approval of installation site, support structures, preferably concrete or steel poles are erected and mechanically reinforced to offer maximum support. Subsequently, the transformer is lifted carefully, preferably by a lifting crane, and clamped to the erected support structure. Transformers should always be clamped in an upright position (Lindsey, 2006). Finally, the necessary electrical connections are performed, and grounding made to prevent either the buildup of static charges, or to provide earth insulation should the windings or the soft core accidentally come to contact with adjacent conductors. 6. Operation and Maintenance In power distribution systems, transformers are costly equipment that should not only be operated precisely, but also maintained to enhance performance and durability. Essentially, all maintenance and operation of transformers should be performed by a qualified and experienced electrical technician. In operation of transformers, three basic considerations that are prioritized include proper insulation, proper installation of lightning rods, and automatic switch protections from excessive load and harsh weather conditions. Primarily, protection circuits play an instrumental role in protection of transformers (Howard, 2013). In case of power surge or lightning strikes, protection switches automatically disconnects and power off a transformer, preventing further damage. In this case, switch and relay mechanisms must be installed and linked precisely. With respect to insulation, harsh weather conditions like strong winds, salty moisture and snow may lead to gradual deterioration of external insulation caps. Therefore, non-degradable and durable insulators that resist the effect of harsh weather should be used. With respect to installation, proper procedures should be undertaken so as not to present mechanical blows to the transformer. Maintenance of transformers is divided into two categories; emergency maintenance, and condition maintenance. Emergency maintenance is performed whenever there is an unexpected underperformance or breakdown of a transformer. Occasionally, transformers can experience physical damages from a heavy storm. After a heavy storm, transformer poles may fall down together with the transformer, or the transformer tank may be broken, leading to partial or total leakage of the transformer oil. In such cases, emergency maintenance becomes necessary in repairing damaged parts, and restoring performance to optimal levels (Anthony & Smith, 2009). Contrarily, condition maintenance is performed on regular basis, particularly once a month or annually. Condition maintenance of transformers involves checking and subsequent restoration of oil levels, mechanical inspection of the equipment, and cleaning of dusty parts to ensure performance efficiency. In essence, both emergency and condition maintenance are necessary in ensuring safety and optimal performance of electric transformers. 7. Health and Safety Instructions In workplaces and social settings, health and safety concerns on transformers should be explicitly defined to prevent any accidents. Primarily, accidents involving transformers are mostly fatal; hence necessary precautions must be taken to prevent and minimize their occurrences. One practical approach used in ensuring health and safety standards is issuance of health and safety instruction manuals (Howard, 2013). In the context of operation and maintenance of transformers, basic health and safety instructions include but not limited to; i. DANGER! WARNING! CAUTION!: posters to indicate the high potential for personal injury, or even death if specified situations are not immediately avoided ii. Do not operate this equipment until all energized and high voltage terminals have been grounded iii. Only qualified and experienced electrical technicians allowed to operate and maintain this equipment iv. Wear protective equipment prior to operation v. Check for internal and external damages prior to installation and operation of transformers and related accessories vi. Tighten bolts evenly during operation to ensure that the equipment is secured properly in the required position vii. WARNING! De-energize the external connection and other connected accessories prior to operation. Otherwise, damage to property, severe personal injury or death may occur. 8. Transformer Accidents in the United Arab Emirates In power distribution, accidents resulting from careless handling and improper installation of transformers are not uncommon, especially in the United Arab Emirates. In November 02, 2012, eight Emiratis citizens died tragically in Oman after a transformer on transportation fell of a power truck into an oncoming traffic. Allegedly, the electrical transformer had been loosely restrained inside the truck, causing it to slip off the trailer. Unfortunately, those killed included women and children. As if that transformer accident was not enough, a fire broke out in Musaffah power plant, located within an industrial hub in Southern Abu Dhabi, destroying equipment and goods worth millions of United Arab Emirates dirhams. The Musaffah fire broke out in the afternoon of April 18, 2013. According to the UEA’s deputy prime minister, the fire was caused by a short circuit fault that occurred inside one of the large step-up transformers (Gulf News, 2013). Actually, the Musaffah power plant fire of April 2013 completely burned up three major transformers each worth 40 million UAE dirhams, and partially destroyed six adjacent transformers of equal value. Below is an image of the Musaffah fire. Figure v: Transformer Fire Accident Fortunately, the Musaffah transformer fire was contained in a swift manner; hence no casualties or injuries were reported. However, the Oman transformer accident led to sudden termination of eight Emiratis lives. Undeniably, such accidental cases involving transformers are preventable (Lindsey, 2006). For example, short circuiting inside a transformer results from improper installation and limited maintenance of the equipment. First, short circuiting inside transformers results from one of these causes; deterioration in the quality of transformer oil, penetration of foreign contaminants into the transformer especially rain water, and unnecessary tension of winding coils caused be effects of abnormally high temperatures. According to reports from governmental investigations, the Musaffah power plant fire was caused by excess oil temperature inside the transformer, which triggered ignition (Gulf News, 2013). Undeniably, temperature protection systems were inefficient, thus the transformer lacked an automatic protection response. In addition, breakage of terminals coupled with improper grounding may have initiated further deterioration of the transformer’s oil. Therefore, proper insulation, checking or oil levels, and grounding were necessary in prevention of the Musaffah transformer fire. Besides prevention of fires from short circuiting, transformers must also be transported with heightened precautions. Particularly, medium and large power transformers require extra safety transportation measures. Commonly, large transformers are transported by rail road. NEMA and NEC standards discourage transportation of heavy transformers on busy highways like the Oman four way system where the transformer on transportation fell of the truck (Lindsey, 2006). In case of road transportation, special permits must be acquired from relevant authorities prior to the exercise. Such special transportation permits allows for clearance of normal traffic until the wide and heavy load has passed. Apparently, the Oman truck which was transporting ill-fated transformer failed to exercise due caution, leading to the tragic accident. These two case studies underscored the importance of safety requirements in handling, installation and transportation of power transformers. 9. Implications and Improvements after the UAE Transformer Accidents Before the Musaffah fire accidents, the Abu Dhabi Civil Defense Department, which is in charge of power production and distribution, mandated periodic maintenance of transformers. According to the spokesperson Col Al Dahmani, every power station was required to conduct maintenance procedures once every two years. After the Musaffah fire accident, the period for maintenance of transformers was reduced to once every six months. Technically, frequent operation and maintenance of large transformers is not only expensive, but also time consuming. However, potential dangers and losses resulting from lack of transformers’ maintenance outweigh the costs involved in execution of frequent maintenance exercises (Lindsey, 2006). Therefore, one modification implemented after the Musaffah transformer accident was reduction of maintenance period for power equipment, especially large electric transformers. Currently, transformers in Abu Dhabi power stations and other sub stations across the United Arab Emirates are inspected once every six months. Among the parameters examined during the frequent inspection exercises include but not limited to; evaluation of insulation oil quality, checking of mechanical damages on bushings, inspection of oil leaks, and maintenance of alarmed thermometers. In addition, tight safety measures are currently in force in transportation and handling of hazardous industrial equipment, including transformers along UAE roads. 10. Conclusion In conclusion, it emerges that transformers are essential components in the power distribution system. Actually, the role of transformers in voltage conversion is indispensible. Since the times of Michael Faraday and Ohm, there have been no other inventions and discoveries that can improve the business of voltage step-up and step-down. In this case, the use of transformers will at least remain in effect for the foreseeable future. In practical contexts, especially in the contexts of health and environmental safety, understanding the basic principles of transformer functioning, together with essential procedures like installation and maintenance of transformers is justified (Gill, 2008). Technically, understanding the basic functioning of transformers is instrumental in acknowledgement of potential health risks associated with the electrical equipment. Moreover, analyzing real-life accidents related to transformers in the United Arab Emirates helps in highlighting the actual degree of health detriments associated with improper handling and operation of transformers. In this regard, deep and wide comprehension of transformers is necessary in appreciating the health, safety and environmental concerns related to the electric equipment. References Kathy, D. (2015). Electrical Physics for Scientists and Engineers: Foundations and Connections. 2nd Ed. Pittsburg: Cengage Learning. Anthony, J. & Smith, L. (2009). Electricity: Electrical Transformers and other Power Equipment. London: Fairmont Press, Inc. Hurley, W. & Wolfe, R.T. (2013). Transformers and Inductors for Power Distribution: Theory, Design and Applications. New York: John Wiley & Sons. Gill, P. (2008). Electrical Power Equipment: Safety in Operation and Maintenance. 2nd Ed. Indianapolis: CRC Press. Lindsey, S. (2006). Occupational Health and Safety: Electrical Safety Guidelines for High Voltage Systems. Indianapolis: CRC Press. Gulf News. (April 2013). Musaffah fire started by short circuit in transformer. Gulfnews.com. Retrieved from http://gulfnews.com/news/uae/government/musaffah-fire-started-by-short-circuit-in-transformer-1.1172289 Howard, I. (June 2013). Instructions: Installation, Operation, and Maintenance of Medium Power Substation Transformers. HI Document 2.4.06, Revision 4. Read More