Supraharmonics in the presence of static frequency converters feeding a 16 ⅔ Hz railway system

This paper presents measurements in the supraharmonic range at a 70 kV busbar feeding four static frequency converters used in the Swedish railway system. The voltage distortion was analyzed for different operational states of the feeding network and four distinct characteristics were identified. It was found that variations in the operational scenario mainly affected the waveform distortion up to about 5 kHz. As the number of converters in operation increased, a noticeable impact could be seen on the frequency characteristics above 10 kHz. Aside from steady-state measurements, several events were analyzed, and it was found that the waveform following disconnection contained significant distortion, albeit for a short period of time.