Generator From Grid

Question 1

What is the critical speed range for Turbine Vibrations? What is done to prevent damage?

Answer 1

IF Vibration >15mils through critical speed range of 1400-1700 rpm then throttle open Turb. Vacuum breaker to drop vacuum approx 2 inches - will slow turbine sufficiently

Question 2

What is importance of Zeroing VARs prior to tripping turbine?

Answer 2

If VARs are not zero when turbine tripped, the 5 second reverse power time delay setpoint will change substantially. The Generator will trip on high excitation after 15 seconds

Question 3

What is the operation scheme for the Generator Output Circuit Breakers (OCB) including where they can be operated?

Answer 3

If generator on grid, can only open OCBs from 923-2 and close from 902-8
If only field breaker trips open, open OCBs from 923-2 (no time delay)
Once reverse power relay picks up, able to trip OCBs from 902-8

Question 4

If the Generator Field Breaker Trips Open, what actions must be taken?

Answer 4

Immediately Open 345kV Breakers 1-2 and 1-7 (9-10 and 10-11);
Verify generator Trips and OCBs auto trip on reverse power;
If generator fails to trip on reverse power then:
Verify generator output digital display on 902-5 indicates 0 MWe - wait 90 seconds then open 345kV CBs from 923-2 panel

Question 5

What actions are required if Generator does not trip on reverse power?

Answer 5

Verify digital display on 5 panel is 0 MWe
Wait 90 seconds
Trip 345kV Breakers on attached buses if generator still not tripped.