OMICRON Magazine

crane work that would otherwise be necessary for an external testing transformer. IEC 62271-203 compliant testing “Once a system has been commis- sioned, the final test – dielectric testing of the system – is carried out. The Power VT is used for this high-voltage test,” explains René Müller. With this Power VT, the induced voltage was applied to the primary conductor of this GIS system and the test voltage conformed to the rated voltage of the switchgear. The rated voltage was 170 kV. The test was carried out in line with the relevant IEC 62271-203 standard with a voltage of 270 kV. The 270 kV was applied between a conductor and the system enclo- sure. The test cycle was specified by the GIS manufacturer. Every GIS manufacturer has its own test cycle for conditioning its systems. In this system with Power VT, conditioning was carried out in several stages. The first stage took five minutes, followed by a three-minute stage and finally by a one-minute stage. The test has been passed if there is no behavior of the transformer, an increased test frequency (approx. double the nominal frequency) must be selected. Therefore, it is necessary to use specially adapted voltage trans- formers for this type of test. In addition to heightening the wind- ing cross-section and altering the winding structure, finding suit- able connection options for the high-test currents is also essential. This modification guarantees that the measurement accuracy and long-term stability of the voltage transformer is not affected by the high currents. Therefore, the new method allows tests to be carried out quickly with fewer personnel. The testing system for the voltage withstand test is connected directly to the voltage transformer that is inte- grated in the GIS system, which eliminates the need for venting and refilling it with SF6 gas. As the voltage transformer is integrated into the system, it is also easy to repeat tests for maintenance purposes. The specially designed VT (Power VT), which is already in- tegrated in the GIS in the factory, eliminates the need for complex an offshore wind turbine thanks to a test transformer (Power VT) that was integrated in the GIS system," explains René Müller. On-site testing in difficult locations The greatest challenges in this project in particular were of course the structural conditions. In this case, it was not possible to use a conventional procedure with an external testing transformer. The lack of space and limited lifting equipment called for a tailor-made solution. The corresponding power unit (Power VT), combined with the OMICRON’s CPC 100 and CPC Sync, made it possible to carry out the required tests without the need for structural changes. Integrated Power VT When it comes to high-voltage testing, the voltage transformer is operated in reverse. Voltage is supplied to the secondary side (low-voltage side) in order to generate the required test voltage on the primary side. Therefore, the transformer must be able to transmit the energy required to generate the test voltage at the capacitive load – the GIS. In addition, due to the saturation