Principles of AC production and transmission for safe use in suitable applications
The principles of electricity production and transmission are stipulated under the Environment, Health and Safety Guidelines document. These are referenced, with examples, in the Good International Industry Practice. The Environment, Safety and Health strategies for power generation, transmission, distribution and supply including relevant information between an electric power plant and the consumer, (Muller et al 2012).
The guidelines are categorized thematically into industry specific impacts, monitoring methods and management. Industry specific impacts of electric power production and transmission include environmental, the professional safety and health, community safety and health and hazardous vulnerabilities.
According to (Redl, R., & Balogh, L. 1992), the following are the environmental interference during the setting up power plants and transmission systems include:
- Minimal air pollution in the surrounding of all thermal power plant in terms of release of poisonous gasses such as hydrogen sulphide, carbon dioxide, dust and electromagnetic radiation.
- Measurements of levels of noise production both occupational and ambient noise at maximum operation of all thermal and geo-thermal power plants.
- Work-related health and safety practices in all the power plants are similar to those in any other large industries which include confined spaces, chemical hazards, dust, electrocution, fire and explosion, noise and ionizing radiation.
- Fire inspection and readiness for combating fire outbreaks in the power plants such as installation of water hose pipes, gas extinguishers and fire alarms.
- Discharge and effluent waste responsibilities, both solid and liquid wastes.
According to (Fawcett & Fore 2008), Occupational health and safety vulnerabilities are largely discussed in the EHS guidelines. These vulnerabilities include acquaintances to workers in the construction sites, electric generation plants and transmission systems. The dangers include:
- Great heights operations and falls which involve the high grid transmission lines or indoor installation of machinery equipment. This hazard is potentiated by working in confined spaces without support and anchoring mechanisms.
- Exposure to contaminants, corrosive substances and poisons that are used as raw material, produced as wastes and products of combustion such as ammonia, chlorine gas and hydrogen sulphide.
- Electromagnetic fields and radiation generated by generators, magnetic centrifuges for solid fuels and high voltage transmission lines.
- Live power lines and electrocution when in conduct with energized lines and equipment during installation, repair or maintenance.
- Occupational exposure to fire, explosion and heat from combustion units, pipes and other hot equipment. The heat is a potential hazard for development of burns.
Community health and safety guidelines as documented in the EHS guidelines include:
- Noise and air pollution during maximum operations of the power plants and its effects on the surrounding community in interfering normal life activities such as schools and learning, work and sleep.
- Electrocution due to conduct with live energized electrical equipment and power lines by the public.
- Electromagnetic interference and non-ionizing radiations emitted from the power plant or transmission system.
- Aircraft navigation interference in cases where transmission power towers are situated near airstrips, airports or known flight ways. They can interfere through physical impact and collisions or radar interference.
- Social concerns from the members of the community such as noise, traffic safety due to increase in traffic volume, socio-economic constraints such as bias in recruitment activities and degradation of moral values caused by expatriates working at the power.
Power produced by the power plants is distributed to consumers for use. The appliances can be grouped into major appliances and small appliances. The home appliances use electronic circuits to convert the AC power to regular direct current. The power generated must therefore be reliable and above all, safe. In most developed countries, the power delivered is 240volts in 50/60 hertz.
The principles of safety use are based on Ohm’s law of electricity. This is applicable from the physiology from a statement that “its current that kills not voltage.” Considering ohm’s law for voltage, current and resistance, the relationship I=V/R is generated. Where I is current is voltage and R is the body’s resistance. Therefore, the higher the amount of voltage, the higher current generated from the body’s resistance that can be hazardous. Depending on the body’s resistance, the amount of voltage from Ohm’s law is V=IR.
The main dangers to safety while using electrical appliances are:
- Electrocution, this happens when the user comes in contact with live energized wires in the electronic equipment.
- Fires that can be generated when the electric current sparks or induces burning due to the heat generated from flow of electrons.
Therefore, the principles applied are:
- Switching off of electric power lines before commencing works of maintenance, upgrade or repair.
- Use of signs, locks, barriers and education or public outreach forums to prevent the public from coming into contact with potential hazardous equipment such as transformers.
- Application of suitable engineering techniques such as high grid power lines, insulation of transmission cables suing special alloys and proper spacing to avoid electromagnetic fields being created and electrocution risks.
- The standard voltage chosen for safety 240 volts. This value is way below the threshold of 600 volts that can cause body damage.
- The home appliances are fused with appropriate sized fuse that blow in case there is a connection to the earth or there is large current flowing to the appliance.
- The AC power in the mains electricity is converted to low threshold voltages by the electronic equipment. Most home appliances operate under 12 volts’ direct current that is under the required threshold to reduce body damage.
- The electronic components such as electric wires are labeled and insulated to avoid direct contact with the high energized live components to reduce risks of shock.
- The electronic equipment is earthed from their casing to reduce the risks of shock when a loose live energized wire comes into contact with the metal case and the user makes contact to the case in times of operations.
Electric is generated into primarily two forms, alternating current(AC) and direct current(DC).
Alternating current is produced in waveforms. The waves are expressed in amplitude. The distance from the zero mark to the highest point of the wave is referred to the peak voltage. The distance from the highest positive value to the lowest value of the wave is called the peak to peak voltage of the alternating current.
The root-mean-spare of a current is defined as the amount of voltage required to pass through a resistor of known resistance over a specific period of time to generate a known quantity of heat. In AC power, the RMS can be described as the square root of means of squares of instantaneous values. Root Mean Square is the actual value of an alternating quantity which tells us an energy transfer capability of an AC source. In DC power, the voltage stipulated, is the RMS. for example, the domestic single phase AC supply is 240 volts at 50hertz where the value 240 volts is the RMS of the alternating current. With this knowledge therefore, the ammeter records the RMS current of the AC power while the voltmeter records the RMS of the alternating voltage.
RMS and peak values of AC electricity
This is according to (Kouwenhoven 2014). Procedure and practices are as follows.
Electricity is a form of energy. Along with its benefits powering technology and being a driving force behind innovation, electricity is among the highest causes of morbidity and mortality worldwide and therefore the need to observe safety when working with electricity. The following are procedures and practices used to minimize risks:
Use of danger signs and hazard signs to avoid conduct with electric equipment such as high voltage lines, live wires and transformers.
Grounding good conductors of electricity such as metallic structures using electricity or installed near power lines to minimize the risk of shock.
Only allowing trained and certified electrical engineers and personnel to install, maintain and repair electrical equipment.
Use of protecting gears during working with electricity, that is use of non-conducting material such as plastics and rubber when working on electrical components.
Use of internationally certified electronic equipment such as properly insulated cables, labeled and earthed home appliances.
Installation of residual current devices to reduce the risk of receiving a fatal electric shock.
Administrative controls comprising of safe work practices to control the risk, for example
establishing exclusion zones, use of permits and warning signs.
Ensure power circuits are protected by the appropriate rated fuse or circuit breaker
to prevent overloading.
Alternating current |
Direct current |
Has a frequency of 50 or 60 hertz |
Has no frequency |
Power factor lies between o and 1 |
Power factor is always 1 |
Flow of electrons is bidirectional |
Flow of electrons is unidirectional |
Their load is resistive, inductive and capacitive |
The load is usually resistive |
The direction of current reverses periodically in wave form |
The direction of current remains the same. |
Generated by alternators |
Stored and produced by batteries or solar energy |
Its passive parameter is impedance |
Passive parameter is resistance. |
Can be transmitted over long distances and converted to direct current |
More substations are required for transmission and can be converted to alternating current |
Similarities.
- AC and DC both kinds of electron flow are harnessed to produce current
- Both AC and DC re measured using volts.
- Both AC and DC are used to provide power, volts multiplied by current, measured in watts.
- Both AC and DC have electrical resistance, measured in Ohms.
- Faults which could cause fires
In a local environment with flammable or explosive atmosphere, ignitions and sparks caused by electricity can create fires that destroy human, animal and plant life and cause destruction of property.
- Contact with live parts causing shock and burns.
Electric current affects the human body when it flows through. This is made possible by the presence of electrolytes in the human body. Depending on the current strength and the amount of voltage dissipated. The maximum accepted amount of current is 5 mill amperes. As the strength of current increases, from lowest to highest, the affected individual experiences tingling sensation with low current and arrhythmias, muscular contractions and death with very strong currents. Unfluctuating currents too small to induce muscle contractions and freezing on the live wire circuit can be strong enough to interfere with the heart’s pacemaker neurons, causing the heart to flutter death occurs to the hearts inability to pump blood to meet the needs of the body.
As electric current flows through the body tissues, there is some form of resistance that generates heat. Depending on the RMS of the current and voltage, the amount of heat generated by the resistant can be vast to cause burns of the tissues.
References
Hambley, A. R., 2017. Electrical Engineering: Principles & Applications. Pearson.
Muller, R. S., Kamins, T. I., Chan, M., & Ko, P. K. ,2012. Device electronics for integrated circuits.
Fawcett, T. J., & Fore, N. S. ,2008. U.S. Patent No. 6,243,652. Washington, DC: U.S. Patent and Trademark Office.
Redl, R., & Balogh, L. ,1992. RMS, DC, peak, and harmonic currents in high-frequency power-factor correctors with capacitive energy storage. In Applied Power Electronics Conference and Exposition, 1992. APEC’92. Conference Proceedings 1992., Seventh Annual (pp. 533-540). IEEE.
Kouwenhoven, W. B. ,2014. THE EFFECTS OF ELECTRICITY ON THE HUMAN BODY. Bulletin of the Johns Hopkins Hospital, 115, 425-446