A novel noise reduction method applied in negative pressure wave for pipeline leakage localization

Noise in pipeline pressure signal is a small noise of which the amplitude is much smaller than that of signal. But it affects recognition of pressure drop and results in inaccurate leakage localization or false alarm. Thus, a small noise reduction method based on empirical mode decomposition (SNR-EMD) is proposed to reduce the noise in pipeline pressure signal. SNR-EMD removes the noise considered as small fluctuations in signal around the mean line calculated by signal's upper envelope and lower envelope. Meanwhile, end effect of SNR-EMD is restrained by extrema mirror extension (EME). Then tested by pressure signal in field, SNR-EMD can reduce small noise well through making the denoised signal smooth and conserving the mutation characteristics of the original signal. Finally, negative pressure wave (NPW) combined with SNR-EMD is used to locate pipeline leakage. The case study indicates that pressure drop can be well recognized and leakage can be accurately located.