The 9689 generator rotor earth fault protection device is suitable for water turbine whose capacity is not exceeding 10MW and the turbine generator whose capacity does not exceed 100MW of generator rotor earth fault protection,The protection device has the function of rotor one point earth protection and rotor two point earth protection.At the same time has 485 communication,Ethernet communication, fiber communication and other variety communication interface.constitute a complete protection of the generator together with the 9698 (differential protection of the generator) and the 9688 (generator backup protection) .
Rotor one point earth fault protection: the protection mainly reflects the rotor circuit a little ground fault.
By solving two different earth circuit equations, the rotor earth resistance and earth position can be calculated in real time by using the principle of ping-pong switch.Schematic diagram is shown below.
Calculate and memory the earth position and memory is to determine the rotor earth for two points.In order to prevent the malfunction of the protection and the calculation of the overflow, the set start criterion:E > 50V.
When the RD is less than or equal to the fixed value of the earth resistance, the time delay is sent to the rotor one point earth signal or acting on the trip.The rotor earth resistance and earth position can be displayed on the unit management machine in real time.
④ earth resistance low fixed value time delay setting range: 1.0~10s, the setting value error is not more than 5%.
③ High fixed value of earth resistance can be set as 10K following delay (1~4s) action in the hair trip.