Double bus failure protection based on zero negative sequence power directional element discrimination

After the fault circuit breaker at the end of the long line of the large mode operation system fails, the composite voltage sensitivity of the 220 kV and above double bus connection failure protection is insufficient, and the line release complex voltage locking function needs to be switched on and off manually, which cannot be automatically adapted after the system mode changes. To solve this problem, the compound voltage locking logic is cancelled, and the zero negative sequence power direction discrimination is used to simplify the startup failure circuit, which improves the adaptability and reliability of line failure discrimination under various operating conditions.