On 22-April-2012 GT (94.2-Siemens) was running at 125 MW in load control mode. There was frequency changes IN Grid from 49.8 to 48.8 Hz and GT tripped on surge protection. Pls. share your experience.

N. Sandru

[email protected]

 

Dear Sekar,

though i have not experienced any such type of tripping so far, but surging in GT based power plant or cogen plant is due to surging in compressor part which is a condition of low flow. When grid frequency reduced from 49.8Hz to 48.8Hz, the air flow to the inlet to the compressor will reduce as flow is directly proportional to speed or frequency. so low flow operation leads to surging at reduced speeds. For that matter bleed valves are provided which remain open during turbine starting. Now you should see the characteristics of compressor at 48.8Hz speed. I don't think it will matter a lot whether a unit is in LCM or Base mode or in Float as far as Surging is concerned b/c the fuel flow is very less compared to compressor discharge. May be some other ppl like CSA, PV can describe and share more in detail and in a better way.

Thanks nd regards,
Ashish

 

Sekar... can you identify the Protective Relay(s) that initiated shutdown?

Regards, Phil Corso

 

Dear sandru,

The following activities are needed to be carryout to find out the problem.

Calibrate the DP switches for used surge protection MBA11 CP001, 002 & 003.

Pressure TX to calibrated MBA11CP004 and monitor the trend of the pressure TX while tripped, then you can find out actual surge occurred or not.

IGV actual angle as same as position feedback to be confirm.

Monitor IGV position and command during grid frequency changing.

regards,
raju.