Power Quality in Electrical Power System - Report Example

Running head: POWER QUALITY IN ELECTRICAL POWER SYSTEM Power Quality in Electrical Power System Course Tutor Date Components of Power Quality According to the Institute of Electrical and Electronic Engineers power quality is defined as the grounding and powering concept of electrical power systems in a manner that is deemed compatible for the operational mode of the equipment and premises cabling. The components of power quality in a system include customer service, voltage quality and supply continuity. To begin with, the customer service component is associated with quantitative operational measures based on performance ratemaking schemes. Customer indicators include safety/ health, customer complaints/ satisfaction, billing accuracy, appointments met during a specified period, responses made to clients and emergency responses among others (Baggini, 2008). The supply continuity is periodically interrupted by a number of factors ranging from rain, introduction of new connections to lines and short circuiting among others. However there are several indicators that have been designed to gauge the continuity of power in an electrical system. Regulation of power supply aims at compensation of clients when power is interrupted for long periods beyond those documented in the local conventions. As a component of power quality, continuity should be monitored from time to time to reduce the interruptions and subsequent outages and related consequences (Baggini, 2008). Voltage quality also matters to the final attributes of an electric power system. As a component of power quality, voltage is a quantitative measure of the end user satisfaction in terms of the rated variations and impact due to loads. The voltage quality is affected by issues such as the recommended frequency of the electrical power appliance, imbalance in voltage, voltage flicker or sags, transient fluctuations, momentary interruptions and ambient harmonics. In order to quantify the variations in power quality, the Institute of Electrical And Electronic Engineers have come up with definitions for the mentioned parameters with an aim of setting standards on them to avoid any ambiguities (Baggini, 2008). Importance of Maintaining High Power Quality In order to satisfy the end user, an electrical system operator should be in line with the rated power requirements of the local conventions. Today’s end user is well informed about these conventions and is therefore aware on the effects of poor power quality on both domestic and industrial appliances. End user satisfaction is key since it is mainly brought about by the availability of quality power within a system. An average client regards quality power as power that is free from interruptions, flickers and sags among others. Failure to meet quality requirements is aggravated by the pending issues in law courts regarding the damages that end users incur from time to time (Dugan, McGranaghan, Santoso, & Beaty, 2003). Power disturbances through impacting factors such as harmonics, transients and frequency fluctuations may result to property losses. This mainly occurs through life shortening effects on electrical appliances such as the stress that is imposed on the capacitors and step down transformers among others. This might also lead to loss of revenue due to down times meant to cater for unexpected or emergency maintenance. In other areas such as industrial and allied, this might translate to loss making when the management has to replace an entire line of machineries due to overvoltage and other related power defects. Some equipment that is strictly rated may not work at a given rating especially when voltages are fluctuating due to outages. Further overloads might also result to undesired functioning of the utilities given the special nature of rating. An example of this is disoperation and shutdown which may cost a client time and money. This might also mean harm to the operator who might be on the receiving end of a faulty electrical power system. Applying mitigation measures and use of subsystems meant for achieving high power quality is mandatory in the current power systems as low power quality cannot be tolerated any more by the end user (Dugan, McGranaghan, Santoso, & Beaty, 2003). Factors Impacting Power Quality Power quality in electrical systems is mainly attributed to factors associated with interruptions, under-voltage and overvoltage. The transient of a power system for example is undesired when it produces distortions in short durations depending on the mechanism of source generation. The waveform characteristics of a source may be interrupted to cause poor amplitude, duration, frequency and capability to deliver quality energy. When the frequency changes suddenly, it causes unidirectional polarity and impulsive transient which are both undesired traits of power. It is important to note that the oscillatory transient that of course occurs when the appliance capacitor banks are switched off and on do affect the flow of current within an electrical system (Fuchs & Masoum, 2008). Variations in voltages heavily impact on the power quality due to voltage dips and interruptions that may fluctuate in terms of period of occurrence. The short period events include the instantaneous, temporary and momentary variations which are all categorized into sag, swell and interruptions faults. These variations are all due to lose connections, faulty circumstances and energization of huge loads. Interruptions are characterised by up to three minutes of energy blackout or cycle disturbance. On the other side, load transfer and starting of highly rated induction motors is considered as the main cause of voltage sags (Fuchs & Masoum, 2008). Fluctuations and flickering of voltages also matter a lot towards the end user power quality. These are characterised by random cyclic and step-voltage load impedances that usually degrade equipment performance leading to instability. Fluctuations may be caused by pulsed power, heavy start-up drives, resistance welding and others that may arise from day to day. Flickers are on the other side due to low rapid variations in voltage in such a manner that cannot be deciphered by human eyes. Lastly the power frequency and harmonics variations are affected due to the normal power rating that have been set by the conventions around the operational area. Deviations are likely to affect the operational speed of the machines depending on the load characteristics. Electric noises are also considered among the issues impacting on electric power system quality for the superimposed phases and conductors that they do introduce (Fuchs & Masoum, 2008). Controlling and Improving Power Quality Controlling and improving of the quality of power entails customer education, introduction of mitigation measures and the last resort is the solution. For example, voltage sags should be minimized through disconnection of power appliances from the distribution generators. In order to control effect of overvoltage on equipment, it is advisable to limit voltage on sensitive insulations, block the surge current, divert the surge current, ground the equipment and prevent surge current. Voltage regulators should also be installed to serve as the bypasses by up for interruptions lasting 30 to 45s. Reconnection of distributed generation should be given up to five minutes in case the customers want to see any differences in power quality. The feeder should also be limited in terms of connected appliances (Chattopadhyay, Mitra, & Sengupta, 2011). The effect of harmonics should be mitigated by ensuring that all those items introducing equipment failure in a system are eliminated. Fuel cells are a good example of this and should be connected to inverters as a way of dealing with the inter-harmonics and harmonics. Resizing power systems and use of capacitor banks can also easily reduced stress under constant harmonic distortions. Reactors can also be used to reduce or cancel harmful resonance on exploring the main cause of problems (Chattopadhyay, Mitra, & Sengupta, 2011). In order to effectively improve the power system overvoltage problems and safety grounding shall be effective measure to put in place. Setting equipment to the ground prevents the high touch voltages in case of faulty end user equipment. All floating panels should be linked to a reliably grounded earth so as to eliminate any excess voltages that are likely to affect equipment depending on the outlet. This also improves device protection as draining low impedance electricity to the ground aids in eliminating the noise (Chattopadhyay, Mitra, & Sengupta, 2011). Description and Explanation of Working of the Power Quality Improving Subsystems To understand the working nature and description of the power quality improvement subsystems, it is important to learn the nature of the faults. Transient voltages are normally associated with lightning and capacitor switching. The transient voltage surge suppressor is used to limit voltages between one point and another. This is made possible through the basic understanding of surge absorption and diversion. Voltage across insulations must be kept safe at all times and as seen in the Kirchhoff’s law the surge current shall always flow to the direction of critical insulation. This subsystem is located as close to the critical insulation as possible in order to act as an arrestor (Chattopadhyay, Mitra, & Sengupta, 2011). Power variations and short-circuit in of power level may be approached during the design stage by introducing the static Var compensator. A static Var utilizes the flexible alternating current transmission system compensator through inclusion of synchronous motors and generators within the system. This aids in regulating the amount of energy that is being injected in the system. Reactive power is generated during low voltage period which results to increased reactive power on the load which relieves feeding lines too. This subsystem is normally connected to two parallel branches which are furnished with a capacitor bank on one of the lines. The load current is zero crossed during the phase resulting to a reactive current which achieves flicker attenuation on the process (Baggini, 2008). Semiconductors in source voltage converters are used in inverting voltage at any frequency. The semiconductor technology which is applied in this subsystem has become handy in assisting of magnitude and phase angle correction to emerge as the one of the best electric regulator. Inverter voltage regulation is commonly done through the pulse-width-modulated pattern through which the reactive power is injected into or absorbed from the main electric power system. Voltage source converter also contains forced commutation compensators which are meant for lo9w inherent delays as a means of dealing with voltage variations. This also deals with harmonics although it increases the value of the supply equipment (Baggini, 2008). References Baggini, A. (2008). Handbook of Power Quality. New Jersey: John Wiley and Sons, Ltd. Chattopadhyay, S., Mitra, M., & Sengupta, S. (2011). Electrical Power Quality. New York: Springer. Dugan, R. C., McGranaghan, M. F., Santoso, S., & Beaty, H. W. (2003). Electrical Power Systems Quality. New Jersey: McGraw Hill Professional. Fuchs, E., & Masoum, M. A. (2008). Power Quality in Power Systems and Electrical Machines. Sydney: Academic Press. Read More

Power disturbances through impacting factors such as harmonics, transients and frequency fluctuations may result to property losses. This mainly occurs through life shortening effects on electrical appliances such as the stress that is imposed on the capacitors and step down transformers among others. This might also lead to loss of revenue due to down times meant to cater for unexpected or emergency maintenance. In other areas such as industrial and allied, this might translate to loss making when the management has to replace an entire line of machineries due to overvoltage and other related power defects.

Some equipment that is strictly rated may not work at a given rating especially when voltages are fluctuating due to outages. Further overloads might also result to undesired functioning of the utilities given the special nature of rating. An example of this is disoperation and shutdown which may cost a client time and money. This might also mean harm to the operator who might be on the receiving end of a faulty electrical power system. Applying mitigation measures and use of subsystems meant for achieving high power quality is mandatory in the current power systems as low power quality cannot be tolerated any more by the end user (Dugan, McGranaghan, Santoso, & Beaty, 2003).

Factors Impacting Power Quality Power quality in electrical systems is mainly attributed to factors associated with interruptions, under-voltage and overvoltage. The transient of a power system for example is undesired when it produces distortions in short durations depending on the mechanism of source generation. The waveform characteristics of a source may be interrupted to cause poor amplitude, duration, frequency and capability to deliver quality energy. When the frequency changes suddenly, it causes unidirectional polarity and impulsive transient which are both undesired traits of power.

It is important to note that the oscillatory transient that of course occurs when the appliance capacitor banks are switched off and on do affect the flow of current within an electrical system (Fuchs & Masoum, 2008). Variations in voltages heavily impact on the power quality due to voltage dips and interruptions that may fluctuate in terms of period of occurrence. The short period events include the instantaneous, temporary and momentary variations which are all categorized into sag, swell and interruptions faults.

These variations are all due to lose connections, faulty circumstances and energization of huge loads. Interruptions are characterised by up to three minutes of energy blackout or cycle disturbance. On the other side, load transfer and starting of highly rated induction motors is considered as the main cause of voltage sags (Fuchs & Masoum, 2008). Fluctuations and flickering of voltages also matter a lot towards the end user power quality. These are characterised by random cyclic and step-voltage load impedances that usually degrade equipment performance leading to instability.

Fluctuations may be caused by pulsed power, heavy start-up drives, resistance welding and others that may arise from day to day. Flickers are on the other side due to low rapid variations in voltage in such a manner that cannot be deciphered by human eyes. Lastly the power frequency and harmonics variations are affected due to the normal power rating that have been set by the conventions around the operational area. Deviations are likely to affect the operational speed of the machines depending on the load characteristics.

Electric noises are also considered among the issues impacting on electric power system quality for the superimposed phases and conductors that they do introduce (Fuchs & Masoum, 2008). Controlling and Improving Power Quality Controlling and improving of the quality of power entails customer education, introduction of mitigation measures and the last resort is the solution. For example, voltage sags should be minimized through disconnection of power appliances from the distribution generators.

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