A Study of Characteristic Signal Propagation Buried Pipeline 1
The propagation constant measurement system was developed for long distance pipelines based on a distributed constant theory for the purpose of maintenance and management of long distance pipelines buried underground, and it was applied for the first time to a 14-killometer pipeline buried underground. This system is based upon the application of the distributed constant theory, and includes facilities to apply an ac signal from the central part of the pipeline, and measure the actual values and phases of voltage and electric current of the ac signal running through the pipeline, at either both ends or between them. In order to accurately measure the phase difference between the two separate points, a reference signal fabricated at 1 PPS (1 pulse per sec) in a GPS (Global Positioning System) was used. With this system, direct measurement of the propagation constant and characteristic impedance of a pipeline buried underground was realized for the first time.
Yusaku Fuji and Koichi Maru
H. Oohira and S. Seiichi, "A Study of Characteristic Signal Propagation Buried Pipeline 1", Applied Mechanics and Materials, Vol. 36, pp. 381-386, 2010