Proximity-Aware Calculation of Cable Series Impedance for Systems of Solid and Hollow Conductors

Wide-band cable models for the prediction of electromagnetic transients in power systems require the accurate calculation of the cable series impedance as function of frequency. A surface current approach was recently proposed for systems of round solid conductors, with inclusion of skin and proximity effects. In this paper we extend the approach to include tubular conductors, allowing to model realistic cables with tubular sheaths, armors and pipes. We also include the effect of a lossy ground. A noteworthy feature of the proposed technique is the accurate prediction of proximity effects, which can be of major importance in three-phase, pipe type, and closely-packed single-core cables. The new approach is highly efficient compared to finite elements. In the case of a cross-bonded cable system featuring three phase conductors and three screens, the proposed technique computes the required 120 frequency samples in only six seconds of CPU time.Comment: Update: This paper has been accepted for publication in the IEEE Transactions on Power Delivery. DOI: 10.1109/TPWRD.2014.233099

Variable Transmission Voltage for Loss Minimization in Long Offshore Wind Farm AC Export Cables

Connection of offshore wind farms to shore requires the use of submarine cables. In the case of long HVAC connections, the capacitive charging currents limit the transfer capability and lead to high losses. This paper shows that the losses can be substantially reduced by continuously adjusting the cable operating voltage according to the instantaneous wind farm power production.Calculations for a 320 MW windfarm connected to shore via a 200 km cable at 220 kV nominal voltage shows that an annual loss reduction of 9 percent is achievable by simply using a 15 percent tap changer voltage regulation on the two transformers. Allowing a larger voltage regulation range leads to further loss reduction (13 percent for 0.4-1.0 p.u. voltage range). If the windfarm has a low utilization factor, the loss reduction potential is demonstrated to be as high as 21 percent . The methodology can be applied without introducing new technology that needs to be developed or qualified.Comment: To be submitted to IEEE Transactions on Power Deliver

Industrial Relations in Norway

The Norwegian industrial relations system is marked by close co-operation between the state, the employers and the unions and by the high degree of institutionalization of labour relations in general and conflict resolution in particulilr. This co-operation arises partly from industrialisation at a time when democratic attitudes and processes were already established and from the need for national unity in the post-war reconstruction. This co-operation and institutionalization is illustrated by the highly centralised trade union movement and in the formal aspects of the bargaining and conflict resolution system such as the Labour Court and the committees and other bodies associated with the incomes policy and tripartite bargaining system

Passive Macromodeling: Theory and Applications

Offers an overview of state of the art passive macromodeling techniques with an emphasis on black-box approaches This book offers coverage of developments in linear macromodeling, with a focus on effective, proven methods. After starting with a definition of the fundamental properties that must characterize models of physical systems, the authors discuss several prominent passive macromodeling algorithms for lumped and distributed systems and compare them under accuracy, efficiency, and robustness standpoints. The book includes chapters with standard background material (such as linear time-invariant circuits and systems, basic discretization of field equations, state-space systems), as well as appendices collecting basic facts from linear algebra, optimization templates, and signals and transforms. The text also covers more technical and advanced topics, intended for the specialist, which may be skipped at first reading. Provides coverage of black-box passive macromodeling, an approach developed by the authors. Elaborates on main concepts and results in a mathematically precise way using easy-to-understand language. Illustrates macromodeling concepts through dedicated examples. Includes a comprehensive set of end-of-chapter problems and exercises. Passive Macromodeling: Theory and Applications serves as a reference for senior or graduate level courses in electrical engineering programs, and to engineers in the fields of numerical modeling, simulation, design, and optimization of electrical/electronic systems

Fast Computation of the Series Impedance of Power Cables with Inclusion of Skin and Proximity Effects

We present an efficient numerical technique for calculating the series impedance matrix of systems with round conductors. The method is based on a surface admittance operator in combination with the method of moments and it accurately predicts both skin and proximity effects. Application to a three-phase armored cable with wire screens demonstrates a speed-up by a factor of about 100 compared to a finite elements computation. The inclusion of proximity effect in combination with the high efficiency makes the new method very attractive for cable modeling within EMTP-type simulation tools. Currently, these tools can only take skin effect into account.Comment: Submitted for publication to IEEE Transactions on Power Delivery. Update: Published in IEEE Transactions on Power Delivery with the revised title of "An Equivalent Surface Current Approach for the Computation of the Series Impedance of Power Cables with Inclusion of Skin and Proximity Effects

Industrial Relations in Norway

The Norwegian industrial relations system is marked by close co-operation between the state, the employers and the unions and by the high degree of institutionalization of labour relations in general and conflict resolution in particulilr. This co-operation arises partly from industrialisation at a time when democratic attitudes and processes were already established and from the need for national unity in the post-war reconstruction. This co-operation and institutionalization is illustrated by the highly centralised trade union movement and in the formal aspects of the bargaining and conflict resolution system such as the Labour Court and the committees and other bodies associated with the incomes policy and tripartite bargaining system

Fast algorithm for broadband macromodeling of high-order frequency responses

The calculation of broadband macromodels from large tabulated frequency responses can be computationally demanding in terms of CPU time and memory, especially in the case of high-order frequency responses. To reduce the computational burden, a fast macromodeling technique is proposed. It applies a piecewise fitting strategy that makes use of a fast rational interpolation scheme to identify a representative set of data samples and an appropriate model order. This information is exploited by the Vector Fitting algorithm to extract the poles of the macromodel in a reduced amount of time. The calculation of the residues is solved as a linear approximation problem, and standard model reduction techniques can be applied as an optional step to remove possible pole redundancies. A cable case example shows that substantial savings are obtained in terms of computation time and memory requirements