Past Seminars
2007
Taming Transient Responses of Distribution Network Cell (DNC)
Dr Mustafa Kayikci
University of Manchester
25 April, 2007
Abstract
Presentation slides (in pdf)
Aging of HV Composite Insulators
Dr Yu Xiong
University of Manchester
27 June, 2007
The work presented is a characterisation of 15-year field-aged 400kV silicone rubber composite insulators. The aging of the insulators is be related to a range of different environmental and electrical factors, including; ultra-violet radiation, surface contamination and electrical surface discharges. The surfaces of the field-aged insulators are not uniform, varying according to the direction of the insulator, the position along the insulator string and the orientation of the surface of the insulator cnsidered. Electrical tests including flashover tests and partial discharge measurements are presented. Chemical surface analysis using FTIR and EDX are utilised to characterise the ageing of insulator surfaces. Analysis has shown that partial discharge measurements are a more sensitive tool to detect the ageing of insulators compared with flashover tests. The levels of the partial discharges can be used as a monitoring tool to determine the degree of aging of the insulators. Correlation between partial discharge measurements and chemical characterisation is also presented. Consideration is given to the sensitivity of the various techniques to the different aging processes present.
Presentation slides (in pdf)Optimal Investments in Generation Capacity under Uncertainty
Dr Raquel Garcia-Bertrand
Universidad de Castilla-La Mancha, Spain
5 October, 2007
Abstract: This work presents a model for assisting generation companies in dealing with planning decisions in a competitive framework. The optimal investments model is formulated as a bi-level problem including uncertainty in future demand and in the investment decisions of all other generation companies. The bi-level model allows the definition of different objective functions for the generation companies and for the market operator, as well as permitting objective function and constraints on the upper-level problem to be function of both the lower-level and the upper-level variables. Investment decisions by the generation company are determined in the upper-level problem, while the lower-level problem clears the market to decide power productions. The resulting linear mixed-integer bi-level programming problem is converted to an equivalent single-level mixed-integer linear program by replacing the lower-level optimization by its Karush-Kuhn-Tucker optimality conditions and by converting the complementarity conditions to linear equivalents. Uncertainty not only on the electricity demand but also on the investment decisions of other companies are represented using stochastic variables in the single-level mixed-integer linear programming problem. Results from a case study are presented and analyzed.
Presentation slides (in pdf)
Impedance Matching Circuit Design and Optimisation for Power Line Communication
Songnan Yang
University of Manchester
31 October, 2007
Abstract
Presentation slides (in pdf)
Modern Medium Voltage Switchgear Technology
Dr Stephan Goettlich
ABB
30 November, 2007
Abstract
Presentation slides (in pdf)
Partial Discharge Control In Power Electronic Modules
Ningyan Wang
University of Manchester
12 December, 2007
Abstract: High electric fields at the edge of substrate metallisation can give rise to partial discharge within power electronic modules and can lead to eventual failure. This research examines the use on silicon gels filled with barium titanate to reduce the electric field enhancement at the edge of substrate metallisation and therefore increase partial discharge inception voltages. The barium titanate filled gel produces a dielectric in which the relative permittivity can vary as a function of electric field but that is also significantly higher than that of an unfilled gel. The theoretical electric field reduction that can be achieved through the use of filled gels is demonstrated and matched to experimental measurements. As promising results are achieved, consideration is also given to the effect of the barium titanate filler on the viscosity of the gel and the thermal conductivity, two key manufacturing issues.
Presentation slides (in pdf)
Nano Transformer Oil and High Voltage Breakdown
Prof Markus Zahn
MIT
18 December, 2007
Abstract
Presentation slides (in pdf)
2008
Characterization of Virtual Power Plants
Guy Newman, PhD Candidate
University of Manchester
1 February, 2008
Abstract: The use of small-scale generation based on disparate new and renewable technologies is becoming more prevalent due to the imperative to reduce greenhouse gas emissions that are thought to be the chief cause of climate change. As penetration of these distributed resources increases, displacing central generation, there is growing need to understand the composite behaviour of groups of Distributed Generation (DG) devices, also known as Virtual Power Plants (VPPs). This seminar will present an overview of the challenges and progress made towards characterising the VPP, focusing on intermittent generation.
Application of FACTS in Distribution Network for Voltage Sag Mitigation
Yan Zhang, PhD Candidate
University of Manchester
Friday 29 February, 2008
Abstract: Voltage sags are regarded as one of the most harmful power quality disturbances due to their costly impact on sensitive load. The overall financial losses due to power quality disturbances, mainly voltage sags, in power systems are increasing with the increase in use of micro-electronic control devices in modern industry. Significant efforts have gone in both, reduction of number of sags and mitigation of the effect of sags in order to minimise high cost associated with equipment failure/misoperation due to voltage sags. Flexible AC Transmission System (FACTS) devices or their sub-derivative Custom Power Devices are efficient and often used and recommended power electronics based devices for mitigation of voltage sags in electrical power system. With FACTS devices installed, the overall system (and individual bus) sag performance could significantly change depending on the type of the device used. In order to assess this change in sag performance in realistic large power systems the classical, essentially static, fault calculation procedure should be amended to incorporate the effects of these devices on bus voltages.
This presentation starts with description of a new approach for quasi static sag analysis using system impedance, Zbus, matrix that incorporates FACTS devices. Three types of FACTS devices, that are most often used in practical applications, are considered in this study: Static Compensator (STATCOM), Static VAR Compensator (SVC) and Dynamic Voltage Restorer (DVR).
The second part of the presentation focuses on describing approach to optimally select and allocate FACTS devices in distribution network in order to minimize the number of voltage sags at network buses. The method proposed is based on optimization of pre-selected objective function using simple and Niching Genetic Algorithms (GA). The objective of the optimization is to achieve the improvement in overall system sag performance of the network. Using proposed GA based optimization, the location, the type and the rating of FACTS devices are optimized simultaneously.
Finally, the presentation discusses an approach for comprehensive assessment of financial benefits to the network resulting from the use of FACTS based devices for voltage sag mitigation. The annual financial losses of the entire network due to voltage sag are used as the ‘savings’ target. The financial losses in the entire network due to voltage sags are first assessed and FACTS devices are then optimally placed in the network using Nitching Genetic Algorithm (NGA) with the aim to reduce overall financial losses in the network due to voltage sags. The cost of individual FACTS devices, their installation costs and annual maintenance are taken into account in optimization procedure. The methodology is largely based on economic evaluation of the solution using several conventional economic analysis methods.
The Development of HVDC Schemes up to 800 kV
Dr Noman McLeod
Areva T&D
March 26, 2008
Understanding Microshocks and its Impact on National Grid's Personnel
Mr Yasir Ahmed, EngD Candidate
University of Manchester
April 11, 2008
Abstract: Overhead line workers become exposed to high electric and magnetic fields in regular basis as a result of working close to High voltage (HV) power lines which occasionally subjects them to receive spark discharges or what also known as microshocks. This presentation will touch upon the experimental activities that have taken place to further our understanding of the phenomena and will briefly discuss the results of a recent survey which has been conducted among National grid linesmen teams in England and Wales. The survey provided some valuable information which will assist the future development of the mitigation techniques.
Reconciling Power System Security and Economics: Mission Impossible?
Dr François Bouffard, Lecturer
University of Manchester
April 25, 2008
Abstract: The electricity pool is a fundamental coordination mechanism for scheduling short-term forward electricity markets. It is fundamental theoretically in the sense that its main goal is the best use of society's resources subject to basic reliability criteria. However, the pool scheduling and its associated marginal pricing procedure may not be able to unambiguously coordinate its self-interested participant generators. In other words, the centrally-determined operation and marginal price schedules may not lead to a competitive equilibrium. Several out-of-market mechanisms have been proposed to bridge the objectives of the pool with those of the market players. Among them are uplifts whose current use still does not induce true competitive equilibria. In this talk, generalized uplifts are proposed as an alternative to traditional uplifts. An innovative mechanism to compute the uplifts is developed. A simple illustrative example is presented.
Partial Discarge Under Nonstandard Conditions
Mr Faisal Alrumayan, PhD Candidate
University of Manchester
May 16, 2008
Abstract: Modern electrical systems including those within aerospace application tend to use higher voltages at high frequency. These will become increasingly common in the future. The forms of system that are being used operate under frequencies/waveshapes other than 50/60 Hz and the testing regimes are relatively undeveloped in comparison to the other standardised tests available for aerospace components. The testing techniques required to measure PD activity are discussed in this presentation. This presentation presents two issues; firstly, the suitability of using standards testing techniques (such as 50/60 Hz) on testing equipments being used for non standard voltages. Secondly, if using non-standard testing waveshapes, the ability to recognise of partial discharges initiated by them using techniques other than the standard phase resolved analysis (PRA) technique.
Monitoring of Power System Oscillations Using Prony Analysis
Mr Deyu Cai, PhD Candidate
University of Manchester
May 30, 2008
Abstract: In this presentation, the application of the Prony estimation method for estimation of dominant low frequency oscillation modes in large power systems will be presented. The objective is to present the methodology for implementing the Prony method and to verify its results by applying the classical eigenvalue analysis. The presentation is consisting of two main stages. In the first stage, the basic theory of the Prony estimation method is reviewed, and two typical test signals are utilized to show the accuracy of the method. In the second stage, simulation signals (e.g. rotor speed and active power) from a single-machine connected to infinite bus, a 22 bus system with 10 generators are respectively analyzed. In addition, the dominant oscillation modes extracted by the Prony method are compared with those obtained by eigenvalue analysis.