Power electronic equipment widely used in the new power system with renewable energy as the main body has introduced new fault characteristics and raised higher requirements for the performance of protective relaying. Traditional protective relaying technology is not sufficient. Active detection protection uses controllable power electronic equipment to generate specific detection signals, and introduces clearer fault characteristics, from which one can construct more simple, sensitive, and reliable protection principles. The disturbance-based fault analysis method provides a theoretical basis for active detection protection, and the development of power electronic technology provides an application basis for active detection protection. For a specific implementation scheme of active detection protection, the key technologies of detection signal selection, generation, injection timing and processing are analyzed in detail, and the applications of active detection protection in typical scenarios such as a DC system and renewable energy power generation are summarized. Future research directions and possible problems in engineering practice are summarized and commented on, and it is expected that this will provide a reference for further research on active detection protection.