Microprocessor based control of photovoltiac cathodic protection system

The objective of a cathodic protection system (CP) is to protect the buried metallic structure against corrosion caused by chemical reaction between the buried structure and the surrounding medium, such as soil. Due to rains and humidity variations, soil resistivity varies, and consequently, the current supplied by a d.c. supply changes. To resolve this problem in conventional systems, the d.c. voltage of the supply is adjusted manually from time to time to keep a constant d.c. current. An elaborate automatic control system using a microprocessor is proposed in this work. Two alternative techniques are discussed. The first technique, like the conventional system, depends on measuring the voltage between the buried structure and a copper-copper sulphate cell at the assigned test points. The microprocessor controlled system proposed keeps the maximum and minimum voltages at the assigned test points within the allowed limits by changing the d.c. supply voltage. The second technique depends on sensing the d.c. load current. If the current changes due to environment variations, the microprocessor system adjusts the d.c. supply voltage in such a way that the d.c. load current is kept constant, regardless of environmental variations.