If one of the two poles will trip for some reasons in a regular bipolar HVDC transmission without a return conductor, it is necessary to block the other pole temporarily during the transition to a monopolar operation with metallic return, this procedure will take 1-2 seconds and will affect the connected AC networks by extra disturbances. The object of this survey has been to answer the question if it is possible to have a balanced bipolar transmission without a return conductor and during a trip of one pole control it as an HVDC transmission with series connected converters by adding the by-pass switches and the logic for a series connected HVDC converter system which means that a shutdown of the transferred power during the transition phases is not necessary. The survey has been performed with the software PSCAD where an already existing series connected converter circuit had been modified to a bipolar system and the control logic for the transition phases has been created. There were some problems with various control signals between the software HiDraw and PSCAD, this was solved by different methods and the result shows that it is possible to have a transition between bipolar operation and monopolar operation with metallic return without the need to totally shut down the power transfer completely. But this requires a large capacitor.

No description available.

Abstract not available

<p><strong></strong>The aim of this Project is to study the influence of high return temperatures in district heating on the costs for heat and power production in a CHP plant.When the temperatures of the water coming back to the heating plant are so high, the overall performance of heat and power production is decreased and, consequently, also the production costs. Along the project, the influence of this temperature on the different parts of a CHP plant are analysed as well as the economical impact it has. At the same time, some general impacts on the entire network are mentioned.</p><p> </p><p>A real network is used in this project, and it is the net of district heating in Gävle (Sweden), and the most of the study is focus in its bigger combined heat and power production plant (CHP), called Johannes.</p>

We consider how the optimal decision can be made if the optimality criterion of maximizing profit changes to that of maximizing return on investment for the general uncapacitated facility location problem. We show that the inherent structure of the proposed model can be exploited to make a significant computational reduction.

This thesis studies the sources of the returns from the momentum strategy and attempts to find some hints for the heated debate on the market efficiency hypothesis over the past twenty years. By decomposing the momentum returns from a mathematical model, we investigate directly the contributors and their relative importance in generating these momentum returns. Our empirical results support that autocorrelation of own stock returns is one of the driving forces for the momentum expected returns. The magnitude of the autocorrelation decreases as the ranking period becomes more remote. The second important source comes from the cross-sectional variation of the expected returns in the winner and loser portfolios at a given time. The third important source is the difference of the expected returns between the winner and loser portfolios. To our surprise, the cross-autocovariance does not contribute much to the momentum expected returns. Thus, the lead-lag effect can cause momentum returns, but its impact is not as significant as we had anticipated. More importantly, by changing the weights of the winner and loser portfolios, we find that the own-autocovariance of the winner portfolio is almost negligible, compared to that of the loser portfolio. The returns of the winners are much more random than those of the losers. This asymmetric own-autocovariance found in the return decomposition provides another underlying explanation to the recent finding that the contribution of the winner and loser portfolios to the momentum returns is asymmetric, and it is the losers, rather than the winners, that drive the momentum returns. Therefore, the market may not be as efficient as we believed before.

Thesis (M. A.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

The finding of reversals in weekly returns has been attributed to a combination of microstructure issues and overreaction to information. I provide new evidence eliminating overreaction as a source of reversal. I show that well-known weekly contrarian profits are followed by a long run of momentum profits. In fact, these profits are strong enough to produce a significant momentum effect over the full year following portfolio formation. Thus, the market does not appear to view extreme weekly returns as excessive, as implied by an overreaction story. To the contrary, this return continuation is consistent with underreaction to the news driving extreme weekly returns. This is supported by cross-sectional tests in which I find this week's news is positively related to next week's returns. The evidence presented here is consistent with growing evidence that underreaction to firm-specific information is a pervasive feature of price formation. Therefore, if any short-run contrarian profits can be realized, they are better viewed as compensation for providing liquidity than as a reward for arbitrage.

Syftet med den här magisteruppsatsen är att undersöka hur tillkännagivandet av företags-förvärv påverkar aktieavkastningen på ett uppköpande bolaget. Testet är begränsat till före-tag som enbart är listade på Stockholmsbörsen under perioden 1996 till 2005. För att testa onormal avkastning användes marknads modellen. Resultatet visade att tillkännagivandet av företagsförvärv har en signifikant effekt på avkastningen för aktien för det bolag som ska förvärva. Majoriteten av uppköpande bolag upplevde en negativ onormal avkastning under test perioden (100 dagar före tillkännagivandet och 100 dagar efter). / The purpose of this master’s thesis is to examine the effect a corporate takeover an-nouncement has on share prices for acquiring companies. The test will only involve com-panies listed on the Stockholm Stock Exchange during the period 1996 to 2005. To test the effect an announcement has, abnormal return for a period before and after the takeover announcement was calculated. The findings from the testing showed that takeover an-nouncements have a significantly impact on shareholder return. The majority of acquirers in the sample had negative average abnormal returns during the event period (100 days prior to the announcement and 100 day after).

A takeover announcement does not necessarily mean good news for stockholders of the acquiring firm. In fact, for a majority of takeovers it means losses in share prices. Motives that can explain this trend are agency and hubris. This thesis is an event study of 28 acquir-ing firms in Sweden between the years 1997-2005, and the purpose is set to see whether stock prices are affected or not. This has been done by the help of the market model. The empirical results show that the takeovers are on average value decreasing operations which indicate that agency and hubris are the primary motives even though one can not for cer-tain exclude synergy.