Intermountain Power Project carrier interference study

The authors summarize the results of an interference study performed for the Intermountain Power Project. Interference by noise generated at the converter stations to open-wire carrier telecommunication lines and to power-line carrier systems is investigated. The frequency range considered is 10-200 kHz. The noise level at the converter stations is estimated using a detailed high-frequency digital computer model and measurement of the noise current from a single thyristor position. The highest interference to open-wire communication lines adjacent to the DC line is for exposures along the electrode section of the DC line where the noise current was found to vary little in amplitude along the section. Interference which may be harmful was found for power-line carrier systems operating on two HVAC (high-voltage AC) lines sharing the right of way with the DC line. In this case, the interference is caused by bipolar noise current, with the effect that one of the lines is affected in spite of the fact that it is located far from the converter stations. For AC lines crossing the DC line, the induced noise is so low that no problems are expected. In the AC systems connected to the converter stations interference is not expected beyond one switching station away from the converter stations