Sound intensity of the Comerford HVDC converter station

The author demonstrates acoustic intensity for in situ sound power measurements of converter-type transformers and rank-orders all other noise sources at the Comerford high-voltage DC converter station. The sound intensity measurement uses two closely-spaced, phase-matched pressure-sensitive microphones to approximate one component of the intensity vector. Measurements made at the Comerford station are used with geometrical considerations and Gauss´ law to compute individual noise source strengths despite interference and reverberation. The data and analyses show that over 84% of the noise is radiated by harmonic filters. Another 12% can be traced to the converter transformers. The analysis also shows that noise levels increase in loaded vs. unloaded converter transformers by nearly four times. The results support the claim that sound intensity has applications in the power distribution industry as a diagnostic tool for quantifying transformer noise. The results also indicate where noise reduction efforts should be concentrated at the Comerford station