RECTIFIERS OF CATHODIC PROTECTION STATIONS FOR UNDERGROUND STEEL PIPELINES AS SOURCES OF POLYHARMONIC SIGNALS

Abstract

Purpose. Research of the spectral power distribution of the output signal of the cathodic protection stations’ rectifiers for underground steel oil and gas pipelines. Methods. The methods of theoretical analysis are used to study the means of electrochemical protection of underground steel pipelines used in Ukraine and abroad. The cathodic protection system is decomposed into a number of subsystems. In the process of analyzing the influence of the identified components, assumptions were synthesized and formalized regarding the influence of the nature of the output signal waveform of rectifiers as part of cathodic protection on its effectiveness. To concretize the assumption, using modeling and mathematical analysis with the Fourier transform a model of the output signal of idealized rectifiers of cathodic protection stations was synthesized. The results of spectral analysis for different types of rectifiers and their operating principles have been compared. Results. The results of the spectral analysis of the output signals of the rectifiers demonstrate the presence of power up to 0.1 mW in the high frequency range. Since even a small current of 4.5 μA flowing from the pipeline into the environment during a year is sufficient to carry away a mass of metal equivalent to a through hole of 1 mm2 in the wall of an underground steel pipeline, this power can cause a weakening of corrosion protection at some points of the pipeline. To avoid this effect, attention should be paid to studying the effect of the output signal waveform on the distribution of the protective potential along the pipeline. Originality. The impact degree and the range of interdependence between the operating mode parameters of the electrical system elements of cathodic protection and the electrical parameters of the object of protection are specified. Practicality. The results obtained confirm the expediency of a more detailed study of the influence of highfrequency signal components of cathodic protection stations on the effectiveness of cathodic protection.