Generator frequency jumping on 50%+ load 1

[ViCH]

Hi everyone.. Please assist on my brainstorm...
DieselGenset 11kV 50Hz 3.3MVA
It was fully commissioned in 2011 and used for emergency cases and plant Turnaround activities. Working Load was about 1.1-1.2MW (40-45%).. Last year we got some new facilities, and load increased. So we noticed, that on 1.3-1.4MW frequency start jumping from 52 to 47 Hz.. If we add some more load - it trips by underfrequency. Fuel filters are clean, injectors replaced, valves clearness calibrated, electronic governor have no alarms.. on 1.1-1.2Mw frequency stable. It looks like "memory effect"... Any ideas? Please ask if any additional info required..

 

[ViCH]

Well I tried Window Watch software, please see this parameters in photos attached.. Any comments? I confuse about FUEL SMOKE LIMIT - why it is 140% ? In manual nothing explained about it parameter..

Viktor
Electrical Technician II

 

[ViCH]

I could not find any logic strings in software.. Ladder or block diagrams.. Nothing. Only parameters and settings.. How to check Woodward logic? Any experiences?

Viktor
Electrical Technician II

 

[FreddyNurk]

ViCH, you likely won't find any, unless its a very custom application, all of the configuration should be able to be done by predefined setpoints, and based on your description, there isn't anything unusual in the application.

Normally with an engine with an ECM, its either preconfigured to run at nominal speed, or its a variable speed setup and will go to idle unless an external device (in this case the Woodward governor) provides it with a speed request signal. All of the engines I've worked with have been fixed speed, with an external device used for synchronising or load sharing, although I don't doubt that its possible to achieve the same thing with a variable speed set.

waross, you're correct, droop should be more forgiving, I'd expect way more problems trying to get isoch systems to behave themselves, particularly without specific load sharing units. That said, I've never seen an isoch system that runs at 52Hz no load and drops to 50HZ when loaded.

I, and perhaps others, have presumed that this is a standby application, and that to transfer off the generator back to mains requires going black, is this correct?



EDMS Australia

 

[ViCH]

Its standby emergency generator, as I mantioned in first message. We use it for vital load during turnarounds, for plant startup, or to recover back plant, after power failure. We are using GasTurbine generators for our Normal operation.

Viktor
Electrical Technician II

 

[ViCH]

Sorry, misunderstand ur question. No, we can transfer back without interruption. Synchro check available.

Viktor
Electrical Technician II

 

[waross]

Isochronous would run at 50 Hz. On the application of a block load the frequency would drop as if it was in droop. It then correct the frequency back to 50 Hz.
On load loss, the frequency would rise as if it were in droop and then correct back to 50 Hz.
Have you checked the actual droop rather than the droop setting?
Droop, primarily a governor setting. Some AVRs may be configured to include droop to facilitate load sharing but that is another issue and another type of action.

AVR mode - load sharing.. Not droop.

This is confusing.
What is the standby generator sharing the load with?
I am talking about governor droop, not AVR droop.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

Would be helpful to know the part number of your Woodward control, based on the page you have provided it looks like you have a DSLC compatible unit, are you using a Woodward DSLC for sync control? Or are you just letting the ATS do a passive sync?

These are really good controls, but not very easy for someone not familiar with governing in general and how Woodward does their electronic controls, as you can see from going thru Watch Window, there are a lot of settings, and many are not active depending on how the configuration is setup.

So first off you need to make sure you have the correct manual for the control you have, there are a lot of 723 manuals, and there are a large number of "standard" configurations and if you have a custom control then it can even be more interesting.

So from your pictures, it appears something is driving speed reference up to 1039 RPM, so it is either getting a signal from a DSLC or from a device wired into one of the signal inputs.
Fuel Smoke Limit, is used if a manifold pressure sensor (typical) is installed and is used to limit fuel delivery until the turbo spools up, mainly used on propulsion units, setting at 140% usually means its just set out of the way to prevent it limiting fuel signal output.
Your settings show a droop bias, usually droop is controlled by a digital input (most standard 723's input A, if you have a custom configured unit could be different), a lot of single unit gensets either have Droop set to 0 in the configuration or have a jumper from B+ to input A to always keep it in ISOCH mode.

If this commissioned fine and has operated successfully for a period of time it is likely not a settings issue, these units just don't change their parameters, they pretty much work or fail, and I have found them to be very robust in a number of applications. Most failures I have seen have been due to power supply issues.

There is no user access to internal logic, on custom units there is a customer version of a programming tool, but it is expensive and used to require a training class to use, limited mostly to OEM's. It is possible you have some custom parameters since instead of driving a fuel actuator this is sending a signal to the injection control module. But without a part number hard to tell.

The only Woodward experts I know of in your part of the world is MAS Europe,

https://www.maseurope.com/

I think they have offices in Turkey and Pakistan.
MarCa Marine used to service GE diesel engines in your region,

http://www.marcamarine.com/contact-us/

not sure who else does in that part of the world anymore, haven't been there for a while.

Along with Watch Window Woodward had a trending software that was very helpful for troubleshooting, should still be available on their website.

MikeL.

 

[ViCH]

Viktor
Electrical Technician II

 

[ViCH]

1039 - its preset of 1000 plus 39 of droop bias.

Viktor
Electrical Technician II

 

[ViCH]

Regarding comissioning time - yes, it was tested, but load was not dynamic, it was static.. Now we dont have load banks at site, and we cant prove is it ok.. Our loads - mostly dynamic, so maybe still settings issue.. I download plenty of Woodward software, testing now.. Wanna find sth logical.

Viktor
Electrical Technician II

 

[ViCH]

Found Fault statuses for solenoids 1 and 6, right side.. If so, it can be root cause.. But last wednesday our engine pass monthly vibration test. Shouldnt 16V engine have abnormal vibration, if 2 cylinders not getting fuel??

Viktor
Electrical Technician II

 

[ViCH]

Found two fuel injection pumps (solenoids) with high resistance coil (measured from EFI control board).. Local test shows coil is healthy. Found field connector - opened and close back, re-tightened, resistance become OK.
Solenoids - Bosch 132X1825.
Also found inside Woodward settings that expected version of software is 2.0, but actual is 20.0.. I know its very minor issue, but I made it equal and saved.
Continue troubleshooting.. Hope next week can make service for fuel line.

Viktor
Electrical Technician II

 

[catserveng]

So your Woodward governor looks to be part of the GE PowerStar control system, I'd assume its mounted in an enclosure with 2 or 3 digital input and output modules and a controller identified as the ECU. By part number it is a standard control cage with a custom program developed for GE Transportation for their PowerStar controls. Most of these that I'm aware of had a common schematic with features added per job spec. Only schematic I can find is from a job for Marinsa in Panama in 2009, should be similar to yours but likely not exact. GE was pretty good about sending a documentation package with these units, do you have it?

Most of the GE PowerStar controls used analog output 4 for the "Fuel Demand" reference to the ECU, so if you measure that signal it can give you an idea of what the 723 is telling the injection control it wants for fuel, then you can see if the fuel demand signal is driving the instability or following it. Also check to see if your remote speed setting input is changing, not sure on your unit what drives it, but had a loose connection on one a few years ago that only seemed to be a problem at higher loads.

When you did your vibration testing, was the engine load stable? If you have an intermittent problem you may not see a missing cylinder or two at lower loads. If you have cylinder exhaust port temperature monitoring you may be able to catch some cylinders temperatures dropping when the load goes unstable.

Hope that helps, MikeL.

 

[ViCH]

Well.. You are right, we have temperature sensors on each cylinder.. Funny thing, it is not connected, and even not projected to connect. Cost saving... Vibration test done without any load. Your ideas make sence, thanks a lot.
Regarding documentation, - I have schematic pack, and some AVR manuals, but nothing on engine side.. Tried to find in internet - but fail.. We do not have GE support, because genset was projectedin Italy, by Intergen company.. Comissioning also done by them.. After that, we only get third parties vendors for separate maintenance, but never woodward specialist... Looks like we have to become this specialist....

Viktor
Electrical Technician II

 

[catserveng]

If you'd like I have a folder for Woodward 723 material, including a set of training power point presentations here,

https://www.logmeinusercontent.com/links/13285dda435ed49a9ae2b119abc448ffd

I have also attached a basic governor class presentation that covers some of the terminology you appear to have had some issues with, hope you find it helpful.

I have only done a few project with the newer GE engines, even fewer with the V228 series. A couple things I found when reading thru some old notes,

Cylinder temperature monitoring is your friend, apparently these engines, at least early versions, had problems with the Bosch pumps, mainly the internal valves controlled by the solenoids, as I remember most problems were found with the cylinder temperature monitoring, the diagnostics for the solenoids didn't always detect the problems.

We had a dredge project several years ago with 2 12 cylinder V228's, after a long layup we found an issue with the fuel supply pressure at higher loads, that led to a similar problem you seem to be seeing, turned out to be a sticking pressure relief valve in the fuel supply pump. Installing a pressure gauge on the fuel supply and suction lines may be a benefit if not already installed.

I do have a GE Installation manual for 12V228's that was for a larger project, have found that most of the info also applies to the 16 cylinder engines, if you think that would help let me know and I'll post it.

Good luck in your troubleshooting,

MikeL
www.pactectric.com

 

[ViCH]

I will be very happy if u send me manual, thanks!
Thanks a lot for sharing Your experience!

Viktor
Electrical Technician II

 

[catserveng]

Here is GE manual I had.

Regards,

MikeL.

 

[ViCH]

Hi everyone. Long time pass, and I still did not get problem solved. Our engineers looking forward to purchase load banks, but it is also long time issue will be.

catserveng, I have checked the signals for Fuel Demands and its changing while starting, then drop to minimum on idle. I still did not get chance to monitor it during load condition. But I notice, that connections of fuel demand signals and manifold air pressure are quite strange. Please see photos attached. Why not Fuel Demand connected just direct to Output +- on 723plus? And manifold pressure also not connected to input +-... Why it using Discrete Input power? So many whys, and nobody on my site can answer. Any experience on that, guys?

Viktor
Electrical Technician II

 

[ViCH]

BTW, should AVR be in same droop mode, as governor? How it can reflect to load efficiency, if for example AVR has no droop, but governor is 4% droop?

Viktor
Electrical Technician II