ransient Overvoltages in Cable Systems Part 2 – Experiments on fast transients in cable systems
Abstract: In this thesis work, transient overvoltages in cable systems are characterized throughboth simulations in PSCAD and laboratory experiments on a system of limitedextension at medium voltage. The system includes a longer and a shorter cable, avacuum circuit breaker in between and two transformers, on the supply side and loadside, respectively. Modeling of the transformer for proper representation of highfrequency components is a key point, which is dealt with in detail in the report.For the laboratory setup, which includes two single-phase cables, an extensive analysisof the measurements done is presented. These include open and close operation of thevacuum circuit breaker at no load, with resistive load and inductive load, respectively.The experimental results are also compared with simulations made in the softwarePSCAD/EMTDC. A number of simulated cases for a similar system including threephasecables are also presented. It was found that certain conditions must be fulfilled inorder for the reignitions to occur. In opening operations, for example, reignitions aremore likely to happen if the contact separation starts just before the current zerocrossing. However, for the closing operation it has been difficult to determine an instantin which the reignitions are more frequent.
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