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Operational Experience of Load Shedding and new Operational Requirements on Frequency Relays

This paper summarises experience and analysis of under-frequency load shedding and power generator islanding. Most power systems can withstand the loss of a single generating unit or a single transmission line. Simultaneous loss of several power system components may cause a severe deficit in active and reactive power. The action of overexcitation limiters on the remaining generators may further a

Algebraic Properties of Ore Extensions and Their Commutative Subrings

This thesis deals with a class of rings known as Ore extensions. An Ore extension can be described as a noncommutative ring of polynomials in one variable. A special focus of the thesis is the study of commuting elements in Ore extensions. In the first two papers in the thesis we prove that commuting elements of Ore extensions are in many cases algebraically dependent. In doing this we extend a

Constrained Pole Placement Using Transformation and LQ-design

A new procedure for constrained pole-placement is presented. The poles of the closed loop system are placed within a circle in the left half plane. The design procedure is noniterative and the solution is obtained via linear quadratic (LQ) design for a transformed system. The circle can be chosen in order to obtain good transient properties of the closed loop system. The method combines the proper

Real and virtual photon structure

The structure of real and virtual photons has been studied in electron-proton scattering processes producing di-jet events at HERA by the H1 and ZEUS collaborations. Data have been compared to next-to-leading order QCD calculations and to the predictions of Monte Carlo generators based on the DGLAP and CCFM formalisms for describing the parton dynamics.

The need of information in public transport

Popular Abstract in Swedish Utforskar äldre och funktionshindrades behov av planeringsinformation i kollektivtrafiken och diskuterar huruvida information kan bidra till tillgängligheten. En omfattande enkätundersökning genomfördes för att validera tidigare genomförda fokusgruppsintervjuer om äldre och funktionshindrades informationsbehov. Resultaten visar att det finns ett behov av information blaExplores elderly and disabled people's travel information requirements when planning a journey by public transport and discusses the potential of information to improve access to the public transport system. Quesionnaire study in order to validate an earlier focus-group interview study about elderly and disabled people's travel information requirements. Results show a need for travel information t