HV AC Testing of Super-Long Cables

A modern, reliable and ecological energy transfer from power producers, such as power plants or wind parks, to the sometimes far-off energy consumers, like industrial plants, large cities or off-shore oil platforms, can be realized efficiently by HV and EHV AC as well as DC cable systems or through gas- insulated transmission systems (GIL). These cable systems replace traditional overhead transmission lines more and more. One can experience that the general tendency for the manufacturing of cable systems at factories goes towards longer manufacturing units, especially with regard to the production of submarine cables. However, not only at the manufacturing of cable systems but also at the installation of these cable systems on site, the system lengths increase continuously. For the quality assurance after the manufacturing at the factories as well as after the installation on site, or also for the off-line monitoring of installed systems, a high voltage test is essential. Hereby, modern insulations can be tested sufficiently with alternating voltage only. This requires some 10 MVA testing power for the testing of super- long cables (SLC) and GIL. The generation of such enormous testing power through independent and mobile test systems at a justifiable technical effort can only be guaranteed by resonant test systems. This effort is optimized by the physical reasonably chosen resonant frequency. Therefore, frequency-tuned HV AC resonant test systems (ACRF) are the best solution for these special test applications. Based on elementary physical principles the right choice of test voltage, test frequency and testing power is demonstrated and clarified on some examples. The compliance of the test procedure with international test standards and recommendations is presented. Finally it is considered, what reserves can be raised for a further increase of the testing power to be expected in future.