In this paper, the task was to describe the basic principles of a cathodic protection system. In the second chapter, we explained: electrochemical corrosion, the process of cathodic polarization, the strength of the corrosion current, the electrolytic potential, the imposed protective potential that is needed to protect the structure from corrosion, and the conditions under which they must be met for the use of the cathodic protection system. In the third chapter, we described two cathodic protection systems, the system with an induced current and the system with sacrificial anodes, and gave their basic characteristics and areas of their use. We analyzed the potential distribution along a pipeline of limited length. We examined the type of anodes used in each of them, analyzed the time and efficiency of the anode operation, and the strength of the protective current. In the case of the induced current system, the power stations that provide the protective current are described. At the end of the chapter, we compared both systems for the purpose of their selection. In the fourth chapter, an example of the use of cathodic protection with an induced current for the protection of a steel pipeline is reviewed. The chapter describes the necessary measurements on the basis of which a decision is made on the technical solution and the basic elements of the system. The selection of anode bed, feeding station and operating mode for the selected example is presented. This chapter is intended primarily to gain insight into the necessary protective current and potential values that ensure pipeline protection. The cost of pipeline maintenance, with and without a protection system, is also compared.