Impressed current cathodic protection system and a method of operating the system

A marine impressed current cathodic protection system having an electrical circuit comprising a control unit for controlling the impressed current cathodic protection system, voltage sensors detecting an output voltage impressed on the circuit and measuring polarized potential of the protected structure, current sensor detecting a current supplied to the circuit and a source of electrical power from at least one direct current power source;

• wherein the electrical circuit comprises a primary circuit and a secondary circuit;
• the primary circuit comprising:
• at least one first electrode connected to a positive terminal of the at least one power source to act as an active anode;
• and
• at least one second electrode connected to a negative terminal of the at least one power source to act as a cathode, wherein at least one metallic component to be protected forms said cathode;
• and the secondary circuit comprising:
• at least one passive electrode normally disconnected from the electrical circuit and arranged to act as back-up protection, the at least one passive electrode being a sacrificial anode;
• the at least one second electrode connectable to the at least one passive electrode;
• wherein
• the at least one passive electrode is connectable to the positive terminal of the at least one power source by a controllable switch in the secondary circuit;
• the control unit is operable to control the marine impressed current cathodic protection system such that the at least one passive electrode is connected to the at least one power source if a detected output voltage in the primary circuit reaches a maximum value and if a determined polarization potential for the cathode is insufficient;
• wherein
• the control unit is operable to control the output voltage supplied to the primary and secondary circuits separately;
• in order to supply an individual output voltage to each circuit.