CONSTANT CURRENT CATHODIC PROTECTION SYSTEM

Abstract

The cathodic protection system is an economical and effective method for protection of metallic structure in electrolyte against corrosion caused by chemical reactions between the structure and the surrounding medium. The variation in the surrounding medium conditions (temperature, moisture ... etc.) results in soil resistivity variation and consequently the current supplied by a DC supply to the structure changes and the structure may be under or over protected most of the time. To resolve this problem in conventional (constant voltage) systems, the DC voltage of the supply is adjusted depends on the experience of the technicians, and the interval between two successive adjustments. The manual adjustment offers a perfect protection only at the moment of adjustment since the operating conditions are subjected to continuous variations. An automatically regulated constant current cathodic protection system utilizing either DC to DC converter or microprocessor to control the regulation is proposed m this thesis to overcome the above mentioned difficulties. This system measures the DC current supplied to the structure and changes the DC voltage of the supply to keep the current constant regardless ofthe environmental conditions.