Surge protection trip for V64.3A model Ansaldo make Gas Turbine

A

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any author

In valthur Gas Turbine power station has V 64.3A model ansaldo make GT. It has been tripped on surge protection tripping in many times due to grid frequencies variation from 50Hz to 49.2Hz. When grid frequency reduced from 49.65Hz to 49.2Hz, the load more than 52MW, the GT got tripped on surge protection.

As per logic If UP stm compressor of the DP switches 2 out of 3 below set value of 23mbar reached and GT speed above 4560, the GT got tripped on surge protection tripped occurred. Instrumentation side the following remedial measure has been taken. The above DP switches calibrated and their impulse line piping cleaned through instrument air, IGV calibrated and mechanical angle, bearing checked and found normal. But suction of the Up steam compr. DP transmitter value GT running 11.5mbar and compr discharge pr has been reads 1.5 bar. No variation at the time of surge protection tripping. Recently year 2014 6 times tripping has been occurred at the time anti impulsion door cannot opened as per trend shown.

pl explain and trouble shooting procedure and permanent remedial measuring report for avoiding of the above nonsense trip pl.
 
any author,

The first question is:

What does the OEM (Original Equipment Manufacturer: Ansaldo) say about the problem?

The second question is:

Has the OEM made any recommendations or suggestions (other that what you've described)?

The third question is:

Have you implemented any of the OEM's recommendations or suggestions?

The fourth question is:

Have the frequency excursions worsened in the last year or so, either the magnitude of the excursions or the period of the excursions increased? (In other words, are the low frequency dips more pronounced than in the period prior to the last six or eight months? Is the rate at which the frequency changes (the "frequency" of the frequency variations) more than in the last six or eight months?

I'm going to guess the OEM is using these sensors and the additional data (including turbine shaft speed) to protect the axial compressor from a stall/surge condition, which is pretty common for many larger heavy duty gas turbines (protecting against stall/surge conditions which can seriously damage the unit).

Unfortunately, you are most likely going to have to present hard actionable data (graphs; recordings; archival data) of the frequency excursions and the changes in sensor input the control system is experiencing during these events to the OEM and ask for their help and assistance. They are the ones who would have the most insight into what the axial compressor is capable of withstanding at or near rated speed, or when the frequency is unstable and less than rated. They may make changes to parameters, or even to the way in which the sensor data is filtered or used during frequency excursion such as you are experiencing.

If you believe all of the instrumentation is working correctly, and that sensing/impulse lines are clean and free of obstructions, and that operating parameters in the Control System are properly set per OEM recommendations, then you are going to have to get the OEM involved in helping to resolve the problem.

I will add just one more thing. I have frequently seen "re-"calibrations of instruments result in even more problems. And, I'm specifically referring to so-called "SMART" sensors which have been "re-calibrated" soon after commissioning. Often, instrument technicians "erase" all settings in these instruments when re-calibrating them, including any filters which might have been enabled and set by commissioning personnel causing the instrumentation to be even more sensitive than previously--even though the setpoints didn't change at all. In the old days, we used to use needle valves in the sensing/impulse lines and would "throttle" slightly with these valves to smooth the changes which the sensors were monitoring. New-fangled SMART sensors have filtering/smoothing capabilities built-in.

However, many of the new SMART sensors are rather slow to begin with (response time to "stimuli") so there is some inherent filtering/smoothing just due to the speed of response.

Again, your best course of action would be to work with the OEM to a resolution. They may have empirical data from other units which can help in the "relaxation" of the surge control parameters, or they have already dealt with this at another site (or sites) and may have a work-around or solution.

Please write back to let us know how you fare in the resolution of this issue.
 
A
> The first question is:
> What does the OEM (Original Equipment Manufacturer: Ansaldo) say about the problem?

Air intake filter replaced by OEM filter

>The second question is:
> Has the OEM made any recommendations or suggestions (other that what you've described)?
No

> The third question is:
> Have you implemented any of the OEM's recommendations or suggestions?
No

> The fourth question is:
> Have the frequency excursions worsened in the last year or so, either the
> magnitude of the excursions or the period of the excursions increased? In
> other words, are the low frequency dips more pronounced than in the period prior
> to the last six or eight months? Is the rate at which the frequency changes (the
> "frequency" of the frequency variations) more than in the last six or eight months?
49.97 to 49.02Hz
 
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