Interference on Mark VI vibration sensor

Hello Team,
I am experiencing a peculiar issue on a GE Frame 5 machine using MARK VI (TMR) control system. The unit was overhauled (repaired- The exhaust diffuser had a catastrophic failure) ,prior to this the issue was never experienced.
When the unit is started to FSNL there is no fluctuation in the vibration reading on the HMI or at local(Handheld vibation sensor has been used to confirm it) , but immediately the unit is synchronized and the breaker closed the Vibration reading(Load gear, Generator -NDE and DE) start spiking.
the Loadgear vib sensor= Vitec 4033-400
Gen NDE /DE- Metrix 5485c
We have been able to ascertain that ;
1-There is no physical vibration on the turbine,
2-The vibration spike starts only when the generator breaker has been closed., immediately it is opened the fluctuation stop. Hence the conclusion that there might be magnetic ,voltage or some sort of interference on the vibration sensors

Has anyone experienced this, or have any solutions??
 
Hello Team,
I am experiencing a peculiar issue on a GE Frame 5 machine using MARK VI (TMR) control system. The unit was overhauled (repaired- The exhaust diffuser had a catastrophic failure) ,prior to this the issue was never experienced.
When the unit is started to FSNL there is no fluctuation in the vibration reading on the HMI or at local(Handheld vibation sensor has been used to confirm it) , but immediately the unit is synchronized and the breaker closed the Vibration reading(Load gear, Generator -NDE and DE) start spiking.
the Loadgear vib sensor= Vitec 4033-400
Gen NDE /DE- Metrix 5485c
We have been able to ascertain that ;
1-There is no physical vibration on the turbine,
2-The vibration spike starts only when the generator breaker has been closed., immediately it is opened the fluctuation stop. Hence the conclusion that there might be magnetic ,voltage or some sort of interference on the vibration sensors

Has anyone experienced this, or have any solutions??
Hello Team,
Cheede,

Is there any work have been done on 52G ,,,? Or other auxilliary /equipment/instrumentations prior to this event?

Can you tell us :
The sensor in question ? Tag name? type( axial radial vibration, sismic ..) and what values are displayed on HMI/I???as you saying that vibration reading are ( load gear, generator NDE/DE) can you be more precise like by sharing a screen shot for example??

Do you have opportunity to do "52G dead bus Closing"?? It can give you gathering /valuables datas for check if these "peak vibrations" occurs when troubleshooting.

As you mentionned it could be an interference issue , but there can be other origin problem...

We can try to support you by adding to the forum bit more precise datas.

ControlsGuy
 
Hello Team,
Cheede,

Is there any work have been done on 52G ,,,? Or other auxilliary /equipment/instrumentations prior to this event? No work was done on 52G

Can you tell us :
The sensor in question ?
Tag name? - BB7,BB10,BB11 (39V-5 , 39V-6A, 39V-6B)
type( axial radial vibration, sismic ..) - Seismic Sensor
what values are displayed on HMI/I???as you saying that vibration reading are ( load gear, generator NDE/DE) can you be more precise like by sharing a screen shot for example??

Do you have opportunity to do "52G dead bus Closing"?? It can give you gathering /valuables datas for check if these "peak vibrations" occurs when troubleshooting. Not at the moment, unit is presently synchronized to live bus, Unit has been closed to dead bus and the issue was still there

As you mentionned it could be an interference issue , but there can be other origin problem...

We can try to support you by adding to the forum bit more precise datas.

ControlsGuy
 

Attachments

Thanks for sharing the screenshots.
Thats quite impressive !

Did you ever perform noise test/measuring around or close to the mentionned devices??

It could be some CEM issue...

According to your statements 52Gclosing command or 52G closed feedback... can make such disturbances?
Can you tell us if wiring for 52G closing/feedback signals are close to the wiring of the sensors??

Where are these sensors physically installed??

Controls Guy25
 
Thanks for sharing the screenshots.
Thats quite impressive !

Did you ever perform noise test/measuring around or close to the mentionned devices?? No, I haven't done this

It could be some CEM issue...

According to your statements 52Gclosing command or 52G closed feedback... can make such disturbances?
Can you tell us if wiring for 52G closing/feedback signals are close to the wiring of the sensors?? No, its not close to the sensor

Where are these sensors physically installed?? The Load gearbox vibration sensor is installed on top the load gear. The GEN -DE is located as the name specifies ,(about 1ft from the Load gearbox vib sensor). The GEN-NDE vibration sensor also located as the name specifies , (about 8ft from the GEN-NDE vib sensor)

Controls Guy25
 

Attachments

Did you ever perform 52 closing/opening command when unit at standstill???

If yes do the isssue is still there?

I do not know if you swapped sensors and get same results??

By now it would be difficult to give more guidance as we are not present at site.


Let see if somebody on the forum had similar issue ...

ControlsGuy25.
 
Do you observing continuous "vibrations"peaks", or intermittent or just on the time period for 52G closing when this phenomen occur??

It can ben a noise signal, as you stated that turbine and load gear & generator have no vibrations constated ??

Controls Guy25.
 
Did you ever perform 52 closing/opening command when unit at standstill???

If yes do the isssue is still there?

I do not know if you swapped sensors and get same results?? Yes, the vibro sensor was changed and the issue persisted

By now it would be difficult to give more guidance as we are not present at site.


Let see if somebody on the forum had similar issue ...

ControlsGuy25.
 
Do you observing continuous "vibrations"peaks", or intermittent or just on the time period for 52G closing when this phenomen occur??

It can ben a noise signal, as you stated that turbine and load gear & generator have no vibrations constated ??

Controls Guy25.
The vibration peaks are continuous as long as the machine is running and the 52G is closed
 
Coud you try to respond to this post ..
Did you ever perform 52 closing/opening command when unit at standstill???

If yes do the isssue is still there?

I do not know if you swapped sensors and get same results?? Yes, the vibro sensor was changed and the issue persisted

By now it would be difficult to give more guidance as we are not present at site.

So we can go forward and try to support you on this case..
 
Coud you try to respond to this post ..
Did you ever perform 52 closing/opening command when unit at standstill??? When the unit is at standstill, you wont have synchronization permissive to close the 52Breaker, tried it there was no response. Vibration values was zero

If yes do the isssue is still there?

I do not know if you swapped sensors and get same results?? Yes, the vibro sensor was changed and the issue persisted

By now it would be difficult to give more guidance as we are not present at site.

So we can go forward and try to support you on this case..
 
Ok
I know that during standstill there is no permissive for synchronization, anyway there should be a method /operation to do for simulating synchronization at standstill, Maintenance crew at power plant do that during outages, for 52G functionnality tests.

If vibration peaks are not occuring at standstill , you may have a serious issue/problem on that "false vibrations peaks" during synchronization & loading.

I have heard that sometimes you can add a low /High pass band filters , but for me these sensors are protected against such phenomena...as they got already such filters along with device kits (transducers)...

This issue is very difficult to troubleshoot remotely, lets see what the guys are saying about this issue.


Controls Guy25.
 
I would be checking to ascertain if any of the wiring from the generator PTs and CTs that return to the turbine controller are near the signal wiring from the vibration sensors. Generally these circuits are kept isolated from each other in different junction boxes and conduits.
 
I would be checking to ascertain if any of the wiring from the generator PTs and CTs that return to the turbine controller are near the signal wiring from the vibration sensors. Generally these circuits are kept isolated from each other in different junction boxes and conduits.
In the event that the PT /CT and the Vibro sensor junction boxes are close and this is the cause , what are the likely solutions to fix the problem ?
 
The exhaust diffuser had a catastrophic failure is the reason I suggested the wiring may have been moved. Years ago a contractor made wiring path changes at a large coal facility during repairs. The AC supply power for large motors and the vibration signal wiring for those large motors were merely placed in the same 4 foot wide cable tray. Although the signal wiring was nearly 4 foot from the supply voltage, induced voltage into the cable tray itself caused problems with the signal wiring. Signal wiring must be completely isolated from AC voltages. Signal wiring shield grounding rules come into the equation as well. Check P core closely the ct/pt feeds the protective core.
 
The exhaust diffuser had a catastrophic failure is the reason I suggested the wiring may have been moved. Years ago a contractor made wiring path changes at a large coal facility during repairs. The AC supply power for large motors and the vibration signal wiring for those large motors were merely placed in the same 4 foot wide cable tray. Although the signal wiring was nearly 4 foot from the supply voltage, induced voltage into the cable tray itself caused problems with the signal wiring. Signal wiring must be completely isolated from AC voltages. Signal wiring shield grounding rules come into the equation as well. Check P core closely the ct/pt feeds the protective core.
This is the most likely culprit, new wires had to be laid and rerouted. I'm also partially covinced that the new cables not being twisted pair is also a contributory factor.
 
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