we are having steam turbine with 220 Mw capacity. the turbine is single shaft turbine with HP turbine than IP turbine than LP turbine which is than connected to generator.

Our turbine was running smooth but due to some electrical disturbance it tripped. when we restarted the machine the differential expansion was steady but after 1hr of rolling is started going to negative saturation value and turbine tripped on differential expansion high. after tripping of the turbine Diff Exp value came to normal. differential expansion probe is mounted between LP turbine and generator. during this problem there was no diagnostic alarm found in mark-v. we have chenged the cable from mark-v to proximeter, proximeter and extension cable from proximeter to sensor. before startup the value of Diff Exp remains normal but as soon as the rolling is started after 1hr it starts going to negative value and goes to saturation level. we have not changed Differential exp sensor as it should only be done when rotor is in cold position.

the connection from DE probe to Mark-v is coming to the DS200TBQDG1AFF terminal board. control system is MARK-V TMR configuration.

can this be a problem from MARK-V board or it is a problem of Diff Exp sensor? can anybody help me in this regard.

 

Check the signal cable shield is only point connected and a proper isolated connector betwen sensor cable and cable extensión, check isolated proximitor bottom surface.

Best regards
Javier

 

tmr, what was the electrical disturbance that caused the initial trip?

Regards, Phil Corso ([email protected])

 

initial trip was due to tripping of service station transformer. due to the distuebance our Cooling water pumps tripped and on low vacuum STG tripped. i have checked for proper shield and found it ok.

 

Tmr, if a master trip occurred (not just a breaker trip) then:

1) Can you produce a chart showing the temperature vs time for each journal or thrust bearing during run-down and subsequent run-up periods?

2) Repeat for lube-oil temperature?

3) Repeat for lube-oil temperature

4) Total duration of down time?

Phil Corso ([email protected])