We are going to perform an electronic overspeed test on our GE 6B CT with MARKV controls. At issue is that we want to perform this after a run because GE recommends the test when the machine is warmed up for a period of time. Any issue with opening the 52G breaker at 3MW's? We can not preselect the unit down to a negative load so that we trip on reverse power. Thought about giving the unit a "STOP" and then after breaker opens give a "START" but was not sure if this releases the 94 shutdown relay.

 

There would be no problem opening the generator breaker at 3 MW.

You can use the LOWER SPD/LOAD button/switch/target to lower the load to 0 MW, or even to lower it to allow the reverse power relay to trip the unit, but that would take some time, so best to open the breaker manually when the load is at about 0 MW.

You could also initiate a STOP and then give the unit a START immediately after the generator breaker opens to abort the STOP (that works on every unit I've ever worked on, but it's not guaranteed on every unit). But if you don't give a START before 14HS drops out (usually 94.5% speed or somewhere therabouts) and if it does then you would have to wait for the unit to shutdown and then re-start it, because once it drops below 14HS you can't re-start it even if flame is still present.

 

Why Are you doing all this for overspeed test????
pascal