Power Quality Report - Lecture notes 1 PDF

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UNDERSTANDING POWER QUALITY3 rd Technical Webinar – Student EditionPower is an important aspect in electrical field which is defined as the rate per unit of time at which the electrical energy is transferred. It is evaluated through its power quality and power reliability. Power reliability is the p...

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UNDERSTANDING POWER QUALITY 3rd Technical Webinar – Student Edition

Power is an important aspect in electrical field which is defined as the rate per unit of time at which the electrical energy is transferred. It is evaluated through its power quality and power reliability. Power reliability is the probability that a system or component will perform a required task or mission for a specified time in a specified environment. It is the ability of a power system to continuously provide service to its customer. A 100% power reliability means zero power interruption or outage which is only ideal and impossible to be done even if the grid is 100% underground. However, a high reliability performance does not translate to quality of a supply. For instance, a customer may not experience power interruption for a given period of time but the plant operation may still be affected with voltage sags. Power quality pertains to the quality of the voltage, including its frequency and the resulting current, that is measured in the Distribution System during normal conditions. Furthermore, power quality is clearly associated to the electromagnetic compatibility of a device. When we talk about the its electromagnetic compatibility, it deals with four significant points. First, equipment operates within its environment without causing disturbance either to itself or other equipment, or back to utility source. It is necessary to achieve the highest efficiency of an equipment when working in order to pull out its highest performance. All of this could be done if the power quality and the equipment’s electromagnetic are both compatible. For the second point, the end-use equipment rating matches supply voltage rating and variation. Mismatch of equipment rating to its supply voltage rating and variation could lead us to a lot of power disturbances or interruptions and could not be able to bring out its potential efficiency. Next, the third point about electromagnetic compatibility is about utility standards must be considered

before purchase of end-use equipment for compatibility of ratings. More likely, it is a practical thinking about electromagnetic compatibility. We could avoid the mismatching of its compatibility as well as double spending if our equipment failed. It is a wise choice to have options inclined with the power quality and electromagnetic compatibility. Lastly, a mismatch is costly in terms of bridging incompatibility. Like what the third point tells us, it would cost us a lot of money to adjust the equipment’s compatibility. For instance, some people buy other equipment to support the incompatibility of their first equipment just to produce and use its best power compatibility. As an advice by the professionals, calculation for equipment’s compatibility should always be done to ensure the best power quality in full efficiency, no disturbance, and cost-wisely. Moreover, Energy Regulatory Commission (ERC) released on April 2006 through ERC Resolution 11 the “Guidelines For Monitoring of Power Quality Standards For Distribution Facilities” requiring all the utilities to conduct annual voltage measurement at two predefined measuring points (nearest and farthest customers) in all primary feeders during the month with the highest system demand and to conduct random voltage measurements on the distribution network, calculate the probability of voltage violation occurring, and the report on monthly basis both the measurement month and the year to date cumulative results. It is all done for the ensure a safe, reliable, and efficient distribution system. For the scope of the guidelines, “Each Distributor shall ensure that no under-voltage or over-voltage is present at the Measuring Point of any user during normal operating conditions. In order to define this, we use SARVI (System Average RMS Voltage Violation Index) for calculating the average number of RMS value of the voltage variation measurement over the assessment period per feeder, where the measured RMS values are those with magnitude of less than or equal to 90%, or is greater than or equal to 110% of the nominal voltage. In evaluating power quality, we will always encounter problems in terms of different points. For instance, voltage unbalance in the maximum deviation from the average of the three-

phase voltages divided by the average of the three phase voltages. This may result to unbalance distribution of single phase loads, unstable system neutral, and one phase out of power supply. Another one is total harmonic distortion which is defines the potential heating value of a component. High harmonic distortion may result on overheating of a component and lower the power quality. Voltage swell in a system affects the power quality in terms of switching off of large loads, switching on of capacitor bank, remote system faults, and lightning. Moreover, over voltage and under voltage is consider to be major points affecting power quality. Over voltage and under voltage both produce inappropriate transformer tap setting. Also, over voltage results on load dropping and continuously on capacitor bank while under voltage de-energized capacitor bank and over-load facilities. Like the earlier problems, voltage transient results on lightning, load switching, and capacitor switching. A sustained interruption is defined as a decrease of supply voltage to zero for a period of time in excess of 1 minute. This may result to tripping of circuit breaker and greatly affect the power quality of the system. Lastly, voltage sag is a major factor affecting both power quality and power reliability. Voltage sag produce starting of electric motors, switching on of large loads, and fault on either distribution, transmission, or generating systems. Voltage sags usually occurs because of natural phenomena and manmade failure. Some of these are internally induced plant events and line-to-ground or line-to-line faults occurring on the utility system due to weather, trees, public interference, and animals. Although the utility can reduce the number of events that could lead to voltage sags, it is impossible to eliminate all the voltage sags. Professionals invented solutions associated to these power quality problems in utility. Some example are insulators washing, animal deterrence, DU equipment and materials for improvement of supply, installation of automatic voltage regulators (AVR), installation of automatic circuit reclosers, installation of tripsaver, installation of fusesaver, and use of Meralco distribution transformer monitoring system. In assessing power quality problems of end-user,

some solutions are proper grounding practices, surge protective device, automatic voltage regulator, uninterruptable power supply, sag correctors, and flywheel energy storage.

REFERENCE: https://www.electronics-notes.com/articles/basic_concepts/power/what-is-electrical-powerbasics-tutorial.php http://www.erc.gov.ph/Files/Render/issuance/18935 Pelago, E. V. (2021, March 6). Understading Power Quality. Metro East, Philippine...