Impact Of Voltage Sag Research Articles

Investigation of voltage sag impact on wind turbine tower vibrations

AbstractTo study the effect of voltage sag on the mechanical vibration of a wind turbine structure, a detailed model that considers the combined electrical, mechanical and aerodynamic aspects of the wind turbine must be used. A drawback of many previously published works in the area of wind turbine simulation is that they study either a very simple mechanical model with a detailed electrical model or vice versa. Therefore, the interactions between electrical and mechanical components are not accurately taken into account. In this paper, three simulation programs—TurbSim, FAST and Simulink—are used to model the wind, mechanical and electrical parts of a wind turbine and its controllers in detail. Simulation results obtained from the model are used to observe the interaction of all three factors affecting the operation of a wind turbine system. The focus of the paper is on the effect of the voltage sag on tower vibration, considering different power system characteristics (i.e. short circuit level and X/R ratio), mechanical parameter (i.e. mechanical tower damping) and wind turbine operating conditions. Copyright © 2008 John Wiley & Sons, Ltd.

Quantitative Evaluation of the Impact of Repetitive Voltage Sags on Low-Voltage Loads

Automatic reclosing is a typical protection method to clear temporary faults in power distribution systems. However, it has a weakness in regards to voltage sags because it produces repetitive voltage sags. In this paper, we explored the repetitive impacts of voltage sags due to the automatic reclosing of power distribution systems. The actual tests of low voltage loads were carried out for obtaining the susceptibility of voltage sags. The final results of the tests yielded the power acceptability curves of voltage sag, and the curves was transformed the 3-D Computer Business Equipment Manufacturer Association (CBEMA) format. For the quantitative evaluation of the impact of repetitive voltage sags, an assessment formulation using the voltage sag contour was proposed. The proposed formulation was tested by using the voltage sag contour data of IEEE standard and the results of the test. Through the case studies, we verified that the proposed method can be effectively used to evaluate the actual impact of repetitive voltage sags.

An Effect of Fault Current Limiter to Distributed Generator Shaft Torque Increase under Voltage Sag

Voltage sags originated at the transmission level can have a very adverse effect on distributed generators running at distribution levels. A fault current limiter (FCL) can be an effective means to limit the voltage sag impact. This paper presents the main results of a research based on digital simulation and aimed at studying the effectiveness of a FCL to limit the impact of voltage sag on the shaft torque of distributed generators. The sensitivity of the shaft torque to parameters of the FCL, the power system and the fault is analyzed.

Voltage Sag Studies in Distribution Networks—Part II: Voltage Sag Assessment

This paper is the second part of a joint paper aimed at predicting the voltage sag performance of distribution networks by estimating voltage sag indices. This part explores the characteristics of voltage sags caused by faults in a distribution network considering the effect of the protective devices installed in the network. The work is based on a Monte Carlo procedure implemented in a time-domain simulation tool. Several scenarios with a different coordination between protective devices have been analyzed. As expected, the main conclusions are that the protection system can have a significant influence on voltage sag characteristics and proper coordination between protective devices can reduce voltage sag impact on end-user equipment.

Power Quality Solutions to Mitigate the Impact of Voltage Sags in Manufacturing Facilities

ABSTRACT The dominant power quality problems in industrial manufacturing applications are short duration voltage sags and momentary interruptions. For ‘normal’ grid customers, the EPRI Distribution Power Quality study clearly demonstrated that the vast majority of power line disturbances are of short duration. For customers connected to ‘premium’ grids, realized with dual independent distribution feeds with high-speed make-before-break ATS systems, connection to transmission grids, or use of highly meshed grids, short duration voltage sags represent essentially 100 percent of the power disturbances they experience. Power quality solutions, which protect against all short duration power line disturbances, provide protection against virtually 100 percent of all the events experienced by those customers who have the highest cost of downtime, the ‘premium’ grid customers. With the increasing demands for minimizing downtime in manufacturing operations, facilities managers have been challenged to identify cost-effective solutions to address power quality related problems. This article will provide an overview of the power protection issues faced by industrial facilities, based on a review of utility PQ problems, typical plant power distribution systems, and sensitivity of various equipment and processes. Select applications' experience of power electronics-based PQ solutions, such as the Dynamic Sag Corrector® (DySC®—pronounced ‘disk’), in critical manufacturing operations will be presented. The selection criteria will be highlighted to demonstrate how the solution configuration, rating and placement within a facility impacts its economic viability. The pros and cons of ‘facility wide’ versus ‘point of use protection’ will be discussed. Finally, the issues related to ROI for manufacturing processes will be discussed.

Distributed Generation: A Tool for Power Reliability and Quality

Distributed generation technologies are entering a changing NorthAmerican utility landscape that is being shaped on one side of the meterby restructuring and on the other by increasing customer demand forhigher-quality, more reliable power . Whatever form restructuring takes,it will likely provide opportunities for more companies, including endusers, to develop small-scale generation capabilities. If established utili-ties can't deliver dependable, high-quality power, the growing numberof users that expect better service will either find different suppliers ordevelop their own generation capabilities.This changing situation is having two immediate impacts. On onehand, some utilities, their unregulated offspring, and independent en-ergy service providers are beginning to offer distributed generationcapabilities at energy users' sites. At the same time, a growing numberof energy users are starting to show a preference for generating theirown power to improve both power quality and power integrity.Distributed generation can improve power quality and reliabilityin several ways: it can serve as a second or redundant source of power;it can isolate sensitive loads by letting them operate independently fromthe grid; and it can minimize the impact of voltage sags. Overall gridquality can also improve, because the impact on other energy users fromharmonics (generated by, say, a nearby industrial user) would be reduced.