Voltage regulation, bus and back- up protection, and generator protection are applications for overvoltage protective relays. Protective Relay Definition: A protective relay is an automatic device that senses abnormal conditions in electrical circuits and triggers actions to isolate faults. These devices act as an investment "insurance," ensuring that equipment and systems are. Effective designs use a combination of protection components like MOVs, TVS diodes, and GDTs across multiple stages. Proper PCB layout and component selection is essential for optimal. Protection relays are indispensable components of modern power systems, ensuring the reliability, safety, and stability of electrical networks.