POWER QUALITY Lecture notes

International Journal of Physical Sciences, 2010

Voltage sag is one of the most common power quality disturbances in electric networks. It is necessary to investigate voltage sag due to consumers' vulnerability. Faults are the main cause of voltage sags in distribution networks. Fault in distribution networks according to its specifications (its location, duration and time) can cause an interruption or a voltage sag at the nodes of the network. By making random faults, the voltage sag in such networks can be investigated. In this paper, the effect of protective devices performance such as recloser and fuse in voltage sag due to distribution network faults using MATLAB Software has been evaluated.

2021

Power Quality is playing an increasingly significant role both at supply and demand sides. With the advent of participation of private player’s in distribution systems, the power quality is expected to be the pivotal decisive factor before the consumers. The types of Power Quality problems that a customer may encounter classified depending on how the voltage waveform is being distorted. There are transients, short duration variations (sags, swells and interruption), long duration variations (sustained interruptions, under voltages, over voltages), voltage imbalance, waveform distortion (dc offset, harmonics, inter harmonics, notching, and noise), voltage fluctuations and power frequency variations. Various techniques applied to mitigate the different Power Quality problems are also presented for consideration Keywords—Power Quality; voltage sag; voltage swell; Micro grid; I.INTRODUCTION Nowadays, reliability and quality of electric power is one of the most discuss topics in power in...

2016

By quick technological advancements in industrial control processes, major industries demand higher power quality. According to IEEE 1159-1995 standard, any problems in voltage, current or freq‌ue‌ncy that lead to the error or malfunctions in electrical equipment are considered as a power quality problem. Among the power quality phenomena, voltage sag has been an important problem for power systems in meeting advanced industries. This phenomenon happens continuously both in transmission and distribution levels. In this paper, following a general review on the voltage sag phenomenon, short circuit faults, starting big inductive motors and energizing of the transformer are considered as the main factors of providing this event. Then voltage sag characteristics are presented. And then the suggested strategies to reduce this event are evaluated. Applying conventional methods for voltage sag compensation is not able to meet this event completely. In recent years, with rapidly developing ...

Voltage sag is regarded as one of the most harmful power quality disturbances due to its costly impact on sensitive loads. The vast majority of the problems occurring across the utility, transmission and industrial sides are voltage sags. The source of sag can be difficult to locate, since it occurs either inside or outside facilities. So, this paper analyses some aspects of voltage sag such as the cost of voltage sag, their characteristics, types of voltage sag, its occurrence, percentage of sag present in power system, acceptable level of voltage sag curve, voltage sag indices, its economical impact, ways to mitigate the voltage sag and finally few devices used to mitigate voltage sag.

Bulletin of Electrical Engineering and Informatics, 2012

Voltage sags are short duration reductions in RMS voltage caused by short circuits, overloads and starting of large motors. Voltage sag has much a global problem. For proper analysis and mitigation of voltage sag, their characterization is important to be analized. The magnitude and duration are the main characteristics of voltage sag. In this paper voltage sag and their characteristics have been presented in a comprehensive way. This paper analized how voltage sags occur, what their characteristics are and the impact on equipments behavior for different conditions. Through voltage source converter, it is possible to compensate for the drop in system voltage or even to temporarily take over the supply completely. The shunt and series controller are based on power-electronic voltage source converters. For a full compensation both reactive and active power are needed. Not only for deep voltage sags but it is also possible to compensate the drop in voltage magnitude by injecting reactive power only.

IET Generation, Transmission & Distribution, 2010

This study presents a new approach for voltage sag assessment based on the concept of 'area of severity' (AOS). The network regions, where the fault occurrences will simultaneously lead to voltage sags at different sensitive load points, can be determined by performing an AOS analysis. The impact rankings of the network lines and buses are also addressed. The impact rankings are determined according to the contribution degree of each line and bus faults to the total expected number of voltage sags in the power system. The concepts of AOS and the impact ranking are useful in establishing efficient planning for the mitigation of voltage sags, and for evaluating the relationship between sensitive load points and system voltage sag performance. 2 Overview of voltage sag assessment 2.1 Stochastic assessment of voltage sags Typically, the stochastic assessment of voltage sags estimates the annual ESF by using the concept of the area of vulnerability and the expected system fault performance (i.e.

Due to rapid technological advancements and rise in world population, quality and reliable electrical power demand has increased significantly recently which is roughly estimated to double by next decade. This heavy burden on the present traditional power systems leads to many power quality problems , less reliability, frequency fluctuations .Out of these many problems being faced in transmission and distribution is Sag

IEEE Transactions on Industry Applications, 1997

Circuit theory models are used to estimate the number of voltage sags in the supply to a paper mill. For every voltage level, the radius of the exposed area (the critical distance) gives the expected number of sags. As the main sensitive load is formed by large adjustable-speed drives, a classification of sags into four types is used. The conclusion of the paper is that the equipment should first be made resilient against sags due to single-phase faults at 400 kV. These faults cause the majority of sags. Sags due to three-phase faults are more severe (especially due to faults at 11 kV), but are less common.