Generator Issue Continued...

zzzzzzz...synopsis please..

It still doesn't work right.

He's desperate and I don't blame him. New gen sets are expensive.

No clue here. (Does that surprise anyone)

LMAO, I really am Lyn! Not winning here with what we have tried so far....

Sorry, I really hope you get it solved, and that it doesn't cost a bazillion dollars.

Yes indeed! Put it this way, if we don't sort this out soon and we get nailed by a tropical depression, we are going to find ourselves up the creek with no paddle lol!

Sounds like you need a better troubleshooting technique.....as a passing comment.FWIW

Link to previous post http://cr4.globalspec.com/thread/84977

Rip out all the expensive electronics and go back to a good old fashioned all mechanical governing system.

At least then you have real screws to turn that make it 'better or worse'.

Now for the system you have has anyone ever checked the sensor that measures the actual RPM's or line frequency to see if it is getting any interference or drift that shows up after running for a while?

I made a mental assumption that they were monitoring the output/load.

That should be day-one stuff for any contractor (in-house electricians/engineers for that matter). How would they know the whole story if they don't know the demand? (rhetorical)

Part swappers....haha...good one (we call them 'black-box-technicians').

Have you added any bulk load recently (like fire hydrant pump) or high capacity DOL operated compressor etc. These bulk loads could even be 1/5th the capacity of the DG set but on starting these loads, the D.G may not have the capacity to maintain the starting current requirements until the load achieve the full speed. Is the D.G rated for prime duty or standby duty? Please consult with the D.G manufacturer regarding performance of D.G with these high inertial loads if such a situation is present at site.

Otherwise I will go with RAMConsult answer.

Hi Guys,

You have all given me some very interesting and useful information here, I am going to hand this over to our Chief Electrician and see if he has checked the points mentioned and try what you have suggested.

Thank you all for you time and responses. I hope you are all well.

-Rob

The question to be clarified here is the generator protection system prematurely or properly trying to prevent the generator from being damaged? Under frequency conditions imply to me that the engine cannot provide enough energy for the mechanical load applied to it. There are engine related things (water in fuel, sticking throttle, dirty air cleaner) that might be a mechanical problem here but tracking the electric load will quickly clarify which side of the equation is the problem.

Troubleshooting can be a b*tch. Without some kind of logging capability that you can revert to and examine data for a periodic or random failure it can be a whole lot bigger b*tch. You don't need too much time resolution or detail, you just have to determine between two events every time, which happens (or starts happening) first. That's more likely to be the cause, or a step closer to cause. Finding an obvious or not so obvious pattern of events that triggers the failure is also a good hint. Exchanging parts can help ONLY if you are certain that any adjustments are correct. My two (euro) cents. S.M.

The reason the Cummins engineer told you to do a fuel pressure reading at two different speeds was for a very good reason.

Diesel fuel acts as a sort of lubricant. In consistency, it is more oily than gasoline, although it does act as a sort of mild solvent.

Diesel engines more often than not operate on compression of the fuel/ air mixture, rather than combustion from a spark.

This requires a very, very high fuel pressure, in *all* of the cylinders.

Water inherently makes a poor lubricant.

This is why water in the crankcase can lead to a seized engine (I have seen it before).

Water in a modern, sophisticated high pressure diesel fuel pump will do the same thing. If it seizes due to lack of lubricity, or even rust, the starter motor will break it free- but it will forever be down on much needed fuel pressure. Which is why diesel engineers are so careful to put water seperators in their fuel systems.

If your high pressure fuel pump was damaged by the water/fuel mixture, the engine is going to have a hell of a time getting up to proper speed, or staying there under load.

Write to agents/manufacturers to rectify,if they refuse/fail sue them.

Emulsified water in the injection pump.

Sorry to say, that the notes since Ramconsult have all a likelihood of validity.

If ever there was a need to break out sensors and do longer term recording of events, this is it. From experience, in hindsight, the recordings are all logical.

Otherwise, we all keep wild guessing. THAT is then expensive.

Hi Robotech,

We had a similar experience, which we overcame.

I tried to post a response but it seems I am blocked for some reason. maybe my reply was too long!

Owen

Hi Owen,

Thanks for the reply, I have sent you a message with my email. Your help is greatly appreciated.

Hi Everyone,

One of our guys just found a wire that was disconnected, our ATS is now functioning properly, however the genset is still not able to run for prolonged periods of time.

Thanks once again for all your help guys.

My experience is in the automotive repair industry for 33 years as Master ASE certified Tech, shop owner and manager. The most wierd and difficult electrical problems to diagnose and repair were poor continuity on clustered ground wires connecting computers, sensors and power systems. I would recommend checking resistance on all your ground circuits. Any high resistance causes sensor readings to go off scale and trigger shutdown events, phantom fault codes and erattic performance. Hope this helps. E. Green.

Thanks Mr. Green, I will check that out.

My vote goes with "Just an Engineer" - system overload, protection kicks in.

(1) make sure all groundings are done properly, we seem to get these so-called labelled "ground faults" on some of our gas turbine gensets, and they can induce a trip condition.

(2) verify that all equipment connected to this is designed for the output of the generator as to frequency, voltage, etc.

(3) you need to have enough monitoring equipment on this to be able to see average and instanteous load, and try running a test with various sectors in the plant on shut-down.

If the generator always indicates an under frequency fault after all the work you have done so far, I would suspect the devices that are used to determine frequency i.e. a tach or circuit board monitoring the generators sine wave to be at fault. Perhaps it is temperature related as you seem to experience many different run times.

Good Luck !

Don't know if this would help...we had a similar problem..small diesel generator. Experts stripped the engine and put it back together..three times. Until I noticed the exhaust stack outside above the generator room. There was hardly any smoke. The muffler and extended pipe were choked with soot. The moment they were disconnected the engine was back to running normal. Perhaps back pressure. regards.