Verbenets B.Ya.

Dzhala V.R.

Melnyk M.I.

Senyuk O.I.

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The direction of electric current is important in electrochemistry, in the problem of metal corrosion in an electrically conductive medium. The flow of current from the medium to the steel surface (cathodic polarization) inhibits corrosion, while the flow of current causes the metal failure. Electrochemical protection is carried out by cathodic protection installations. A rectified pulsating electric current is applied to the metal. The direction of this current is taken into account to control the correctness of cathodic protection and determine the protective current density. The known contact and contactless methods for determining the direction of current are analyzed, and their shortcomings are revealed. A new method for contactless determining the direction of rectified current is proposed, the physical grounds of which are the presence of periodic pulsations with harmonic components, the asymmetry of pulsations relative to the average value, and the unambiguous relationship of current components with the polarity and magnitude of electrical signals from the magnetic field receiver. The time dependences of the harmonic components of the current for two- and one-half-wave rectification are analyzed. The essence of the method is explained by graphs of the time dependences of the rectified current and its harmonic components for forward and reverse currents. The maximum values of the first harmonic correspond to the smooth extrema of the forward rectified pulsating current. For the reverse current the maxima of the same first harmonic correspond to the sharp extrema of the rectified current. This asymmetry of ripples is used for the recognition of forward and reverse rectified currents proposed in this method (Dzhala's method). Informative signs of the direction of the rectified current along the direction of the second harmonic current at the moments of maximum values of the first harmonic were identified. Schemes were developed and a prototype of the device was manufactured and its operation was tested in the laboratory and on the route of main pipelines. The elimination of the influence of interfering currents and fields, which increases the reliability and accuracy of determining the direction of the rectified current in hidden conductors are the method advantages compared to the known methods. The method can be used to detect and determine the direction of rectified pulsating current regardless of the presence of other external direct currents when monitoring electrochemical corrosion protection currents in underground pipelines, as well as in control systems, electrical automation, and radio electronics.

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