L Colla

Steady-state operation of very long EHV AC cable lines

Technical improvements in the construction of EHV cables have made possible the installation of very long EHV AC cable lines; with a sufficient degree of voltage control such lines can retain a large part of their theoretical power transmission capability. Quick, accurate expressions for the evaluation of cable length-loading relationships are given to that purpose. Appropriate choice of shunt compensation by standard, fixed-type shunt reactors, aimed at solving most steady-state constraints on the operation of very long EHV cable lines as well as temporary overvoltages, is discussed. Analysis of the operating envelopes of very long EHV AC cable lines shows that line losses play a very limited role. A simple criterion for optimal utilization of real, lossy cable lines is also proposed.

Mediterranean high voltage submarine cable links technology and system challenges

The growing interest in international interconnection lines as well as offshore-located energy generation has led to the improvement of high voltage submarine transmission technology. The paper deals with the technology and system challenges typical of submarine cable links in the Mediterranean Sea. Recent developments in HVDC converters technology and submarine cables are summarized. An overview of the state-of-the-art for submarine transmission technology is provided and major issues concerning DC and AC connections, taking into account both HVDC and recent AC advances, such as large cross-section, XLPE-insulated three-core cables are outlined. Attention is focused on the assessment of actual limits of transmissible power and length of AC links and calculation of losses in HVDC and HVAC systems, aiming at the evaluation of the most convenient choice. In particular, the effect of reactive power and current profiles along AC cables is studied.

Insulated cable systems with high current ratings, case studies and practical applications

Current rating computations for HV and EHV insulated cables play a crucial role in the planning phase of a new undergrounded line for both an entirely cable link and a mixed or hybrid (cascade connection of overhead and cable line) one. The paper gives a wide overview of the technical solutions which allow very high current ratings in undergrounded insulated cables. These solutions are examined from a theoretical standpoint and practical applications are shown and explained. The paper demonstrates that in underground insulated cables current rating up to 2500 A can be reached.