462 research outputs found
Power quality and electromagnetic compatibility: special report, session 2
The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems.
Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages).
The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks:
Block 1: Electric and Magnetic Fields, EMC, Earthing systems
Block 2: Harmonics
Block 3: Voltage Variation
Block 4: Power Quality Monitoring
Two Round Tables will be organised:
- Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13)
- Reliability Benchmarking - why we should do it? What should be done in future? (RT 15
A novel approach for assessing the impact of voltage sag events on customer operations
The business activities of the majority of industrial and commercial customers are dependent on some critical equipments that are susceptible to voltage sag events. Malfunctioning of sensitive devices against voltage sags has a detrimental effect on the operation of the customers. Although previous studies have proposed assessment methods to calculate the financial impact of voltage sag events on these critical devices but the approach of the methodologies are limited to specific case studies with particular customer operations and cannot be applied to diverse customers.
This thesis aims to propose a novel and generic evaluation approach for estimating the financial impact of voltage sag events on customer operations. The proposed technique is based on the event tree method. Using this approach, it is possible to consider the impacts of operational failure of various sensitive equipments involved in the customer operations on the financial losses expected from voltage sag events. A methodology, based on the developed approach, is also proposed for analyzing the effectiveness and practical viability of various voltage sag mitigation solutions. A quantitative case study is conducted in the thesis to illustrate the applicability of the purposed approach. Moreover, a comparative assessment was made to find out the applicability of various mitigation options. The method can be applied by customers to select the most economical mitigation option for their operation
A general mathematical model for LVRT capability assessment of DER-penetrated distribution networks
Low voltage ride through (LVRT) is one of the indispensable issues of recent decade in the context of grid codes. LVRT stands for the ability of a generation facility to stay connected during the voltage dip. Despite the numerous discussions in recent works, but they mostly concentrate on the LVRT-based control of distributed energy resources (DERs) integrated into a microgrid and its improvement. However, what has been hidden and not addressed any more yet is an index to measure the LVRT capability of a DER-penetrated distribution network (DPDN) under different voltage sags. This takes precedence when we want to evaluate the LVRT capability of DPDNs with consideration of various LVRT categories of DERs mandated in IEEE 1547 standard. This paper introduces a general framework for LVRT assessment of a DPDN by solving a system of differential algebraic equations (DAEs). Then expected LVRT capability of a DPDN is evaluated by a proposed LVRT index through the implementation of Monte Carlo simulation technique.This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/fi=vertaisarvioitu|en=peerReviewed
Harmonic Estimation Of Distorted Power Signals Using PSO – Adaline
In recent times, power system harmonics has got a great deal of interest by many Power system Engineers. It is primarily due to the fact that non-linear loads comprise an increasing portion of the total load for a typical industrial plant. This increase in proportion of non-linear load and due to increased use of semi-conductor based power processors by utility companies has detoriated the Power Quality. Harmonics are a mathematical way of describing distortion in voltage or current waveform. The term harmonic refers to a component of a waveform occurs at an integer multiple of the fundamental frequency. Several methods had been proposed, such as discrete Fourier transforms, least square error technique, Kalman filtering, adaptive notch filters etc; Unlike above techniques, which treat harmonic estimation as completely non-linear problem there are some other hybrid techniques like Genetic Algorithm (GA), LS-Adaline, LS-PSOPC which decompose the problem of harmonic estimation into linear and non-linear problem. The results of LS-PSOPC and LS-Adaline has most attractive features of compactness and fastness. . Our new proposed technique tries to reduce the pitfalls in the LS-PSOPC, LS-Adaline techniques. With new technique we tried to estimate the Amplitudes by Least square estimator, frequency of the signal by PSOPC and phases of the harmonics by Adaline technique using MATLAB program. Harmonic signals were estimated by using LS-PSOPC, PSOPC-Adaline. Errors in estimating the signal by both the techniques are calculated and compared with each other
Framework for assessment of economic feasibility of voltage sag mitigation solutions
Current practices of power quality mitigation in the industry are characterized by sub-optimal investment decisions where over compensation is often the norm such causing huge wastage in financial resources. Providing power quality management services to industrial customers in the form of power quality contracts could yield substantial return for the network operator. With better understanding of network parameters, and the option of installing network level mitigation devices, network operators could employ wider range of cost effective mitigation solutions. Tapping into the market however, entails bearing the risks for the customers which network operators are not always willing or encouraged to do. With potentially millions at stake, extensive risk assessments are crucial for any proposed power quality management scheme. This thesis investigates the voltage sag aspect of the problem as part of a larger power quality management scheme. The aim is to develop general framework for technical and financial assessments of voltage sags prior to the introduction of power quality management service. The thesis focuses on five major aspects of voltage sag assessment: identification of customer requirement, financial loss assessment, network sag performance estimation, sag mitigation, and financial appraisal of mitigating solutions. The first part of the thesis gives a comprehensive overview of current power quality problems faced by industrial customers and provides ranges of typical financial losses incurred by different types of industries around the world. It then proposes robust methodology for assessment of typical financial loss, i.e., customized customer damage function (CCDF), for a given industry based on available survey data and taking into account characteristics of the assessed customer plant. For failure and financial risk assessments, the thesis introduces new customer models employing probabilistic methods to quantify risks induced by voltage sags and proposes generic models that incorporate full flexibility in failure risk assessment, taking into account the effect of unbalanced sags on equipment behavior. It further quantifies the error introduced by sag performance estimation using limited monitoring data with a case study on actual sag profile. It demonstrates how different estimation methods and different durations of monitoring period affect accuracy of estimation of voltage sag profile and associated risk of industrial process failure. Following this, the thesis presents new models for plant and network level sag mitigation devices. They include power injecting mitigation devices, devices that reduce number of faults in the network and devices that reduce the severity of faults. Developed models are then used to investigate the cost-effectiveness of sag mitigation at different levels. Finally, the thesis presents Genetic Algorithm based methodology for deciding on optimal investment scheme in voltage sag mitigation in the network. The sensitivity of the solution to various influential parameters, including plant type and size, sensitive equipment type, process characteristics, financial loss resulting from process interruption, cost and effectiveness of mitigating solution and network fault rates is also established.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Reliability Studies of Distribution Systems Integrated with Energy Storage
The integration of distributed generations (DGs) - renewable DGs, in particular- into distribution networks is gradually increasing, driven by environmental concerns and technological advancements. However, the intermittency and the variability of these resources adversely affect the optimal operation and reliability of the power distribution system. Energy storage systems (ESSs) are perceived as potential solutions to address system reliability issues and to enhance renewable energy utilization. The reliability contribution of the ESS depends on the ownership of these resources, market structure, and the regulatory framework. This along with the technical characteristics and the component unavailability of ESS significantly affect the reliability value of ESS to an active distribution system. It is, therefore, necessary to develop methodologies to conduct the reliability assessment of ESS integrated modern distribution systems incorporating above-mentioned factors. This thesis presents a novel reliability model of ESS that incorporates different scenarios of ownership, market/regulatory structures, and the ESS technical and failure characteristics. A new methodology to integrate the developed ESS reliability model with the intermittent DGs and the time-dependent loads is also presented. The reliability value of ESS in distribution grid capacity enhancement, effective utilization of renewable energy, mitigations of outages, and managing the financial risk of utilities under quality regulations are quantified. The methodologies introduced in this thesis will be useful to assess the market mechanism, policy and regulatory implications regarding ESS in future distribution system planning and operation.
Another important aspect of a modern distribution system is the increased reliability needs of customers, especially with the growing use of sensitive process/equipment. The financial losses of customers due to industrial process disruption or malfunction of these equipment because of short duration (voltage sag and momentary interruption) and long duration (sustained interruption) reliability events could be substantial. It is, therefore, necessary to consider these short duration reliability events in the reliability studies. This thesis introduces a novel approach for the integrated modeling of the short and long duration reliability events caused by the random failures. Furthermore, the active management of distribution systems with ESS, DG, and microgrid has the potential to mitigate different reliability events. Appropriate models are needed to explore their contribution and to assist the utilities and system planners in reliability based system upgrades. New probabilistic models are developed in this thesis to assess the role of ESS together with DG and microgrid in mitigating the adverse impact of different reliability events. The developed methodologies can easily incorporate the complex protection settings, alternate supplies configurations, and the presence of distributed energy resources/microgrids in the context of modern distribution systems.
The ongoing changes in modern distribution systems are creating an enormous paradigm shift in infrastructure planning, grid operations, utility business models, and regulatory policies. In this context, the proposed methodologies and the research findings presented in this thesis should be useful to devise the appropriate market mechanisms and regulatory policies and to carry out the system upgrades considering the reliability needs of customers in modern distribution systems
Impact of photovoltaic plants on voltage sags
Abstract:M.Phil. (Electrical Engineering in Power and Energy Systems
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