Celilo-Sylmar plusminus 400 kV line RI correlation with short test line

Radio interference data collected from the 1360 km (845 miles) ± 400 kV Celilo-Sylmar HVdc line (dc Intertie) since operation began on May 21, 1970 is reported here and compared with previous results from a 2.02 km (1.26 mi) dc test line section with similar conductors. Fair weather measurements of RI lateral profiles at 834 kHz and frequency spectra from 20 kHz to 1.5 MHz are presented. An empirical RI formula based on experience from these lines is included.