Application of overvoltage protection to the Peruvian power system

In a sparse power system, the shunt capacitances and series inductances of long transmission lines can cause significant voltage variations between high and low load periods. Overvoltage relays in substations are used to protect power transformers from damage due to high voltage. In the Peruvian system, these relays are usually located only at power transformers or busbars. But sometimes it is better to trip selected long lines before tripping power transformers to mitigate temporary overvoltages. Tripping of power transformers and their connected loads exacerbates the temporary overvoltage leading to the possibility of a widespread black out. Another important issue is coordinating the overvoltage relay settings system wide. This paper describes a methodology to set overvoltage relays considering the overvoltage protection as a system protection more than a local protection. An application of the coordination done in the Peruvian power system is described.