Download Power Transmission by Direct Current by Dr.-Ing. Tekn. dr.h.c. Erich Uhlmann (auth.) PDF

By Dr.-Ing. Tekn. dr.h.c. Erich Uhlmann (auth.)

The direct present transmission scheme linking the island of Gotland to the most­ land of Sweden via a submarine cable less than the Baltic Sea is the 1st advertisement realisation of a latest procedure for the transmission of electric power. it truly is not at all unintentional that this pioneering initiative used to be disbursed to the Gotland scheme. quite a few viewpoints could be offered concerning this, however the crucial issue pertains to the situations that approved the value ofthe transmitted energy to receive a price which might now not were technically or economically possible for the other undertaking. the ability, at the one hand, was once small enough to justify the chance linked to this type of new enterprise, for it fell inside of limits applicable either to ASEA because the producer and to the Swedish nation energy Board because the patron. nevertheless, the ability was once big enough to illustrate the technical and monetary features of the hot approach and to supply the possibility of gaining priceless event that may be utilized to destiny large-scale transmission structures. In 1954 a crew below the course of Dr. Uno Lamm effectively commissioned the Gotland scheme, representing the end result of a long time of extensive improvement work.

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It is particularly important to note that, in conjunction with our definitions, DiO must be calculated from the alternating voltage corresponding to the large ellipse axis. 3 relative to its value in the absence of the ground fault. c. 1 100 kFig. 00 kFig. 11 Fig. 10. Direct voltage for Cases a and b with rx(P)=O. Fig. 11. Third current harmonic IN3 on the valve side due to asymmetrical network voltages. IN! Fundamental network current with symmetrical network voltages; ax, bx Phase x of the valve side in Cases a and b; x Phase according to Fig.

Converter Performance under Special Conditions Harmonics with frequencies given by Eq. 6) can however originate from the other end of the transmission system, if the converter at that end is connected to a network having a different fundamental frequency. If we denote the two sides ofthe transmission system with 1 and 2, then, in accordance with Eqs. 9) F or example, this condition is fulfilled in the case of h= 60 Hz and f2 = 50 Hz smce (6 - 1) x 60 = 6 x 50. Fig. 3. Direct current induced flux in the transformer core caused by direct current harmonics with different phase positions if!

The asymmetry in the firing control, as assumed here, is also not the only reason for the presence of abnormal harmonics. We will also encounter other causes and we must consequently accept that such harmonics may be present. C. 2. An example of harmonics in an asymmetrical network current (p=6, A=2°, L\A= la, K=O). In the last column values for the symmetrical network current. 2 are strongly reduced, even if not completely eliminated. The presence of abnormal harmonics is one of the reasons why one does not set about introducing the previously mentioned complication with pulse numbers higher than 12 (Chapter 2).

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