This project report proposes a design and construction of model of protection equipment for three-phase transmission line by voltage relay for protect. By protection equipment can protect the transmission line from over voltage and under voltage on the transmission line The objective of design and construction model of protection equipment for three-phase transmission line. The objective for construction model of protection equipment for three-phase transmission line. For understand power system protection principles. And understand using to protection equipment for three-phase transmission line correct. From experimentation model of protection equipment could protect over voltage and under voltage on the transmission line