Analysis and mitigation of high frequency harmonic interference in high voltage power line carrier coupling systems

Interference resulting from high-frequency power system harmonics in the band below 10 kHz has been previously reported to adversely affect high-voltage power line carrier coupling systems. Problems such as equipment failures and carrier signal interference have been experienced. Previous work by others has characterized the nature and origin of power line carrier coupling system problems caused by harmonic frequency interference. However, computer-based modeling of coupling systems suitable for frequency response analysis was not made available. Also not made available by previous work was an analysis of simple and inexpensive methods for mitigating harmonic frequency interference. The results of the study presented expand previous work by providing an additional resource on high-frequency harmonic interference. Frequency response measurements of three common types of coupling systems using typical coupling capacitance and drain coil inductance values are provided. Also presented are state-space models of the coupling systems suitable for estimating the frequency responses of the coupling systems in the harmonic frequency band. Finally, coupling system components that can be altered for problem mitigation are identified, along with an example of interference mitigation on a 230-kV coupling system that was severely affected by harmonic frequency interference.