9689 Generator rotor earth fault protection relay
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
rotor two point earth；
Excitation voltage: UL;
The 485 communication,
Optical fiber communication,
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.
among：S1、S2 is electronic switch controlled by microcomputer,RD is earth resistance,E is rotor voltage,4 dropping resistors R,A measuring resistor R1.when When S1 is closed, S2 is disconnected (state 1).measured the voltage on the U1 is R1，when S1 disconnect, S2 is switched on (state 2) then measured the voltage is U2.△U=U1-U2,The earth resistance and earth position are calculated as follows:
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.
b Technical index
① High fixed value setting range of earth resistance：1~50k,The setting value error is not more than 5%;
② earth resistance low fixed value setting range: 0.1~20k, the setting value error is not more than 5%;
③ earth resistance high fixed value time delay setting range: 1.0~10s, the setting error is not more than 5%;
④ earth resistance low fixed value time delay setting range: 1.0~10s, the setting value error is not more than 5%.
c Setting calculation
① The setting value of the earth resistance depends on the insulation level of the rotor circuit during the normal operation;
② The high fixed value of the earth resistance can be adjusted to 10K and the above time delay (4~10s) action to send the signal;
③ High fixed value of earth resistance can be set as 10K following delay (1~4s) action in the hair trip.
d Fixed value setting list
Rotor two-point earth protection
The function is realized on the basis of one point earthing protection, when the change of the grounding position is larger than a certain value, the two points are considered to have two grounding points, and the instantaneous trip is protected:
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