Generator Paralleling Problem

GA... made perfect sense when I re-read the situation with your comments in mind!

Thanks CI I got the T-shirt for this one, it's usually seen as load sharing problems between generators at almost full load and the Electrician is called to fix his speed controller on the one that's not carrying the load.

While he does some stability, gain and droop adjustments and maybe swaps some cards the mechanic has noticed the pressure on his fuel filters and switched over, the problem goes away and no one knows what fixed it.

With the new electronic fuel injectors you can't send the Mechanic out to see where the rack is on the MG that's not carrying the KW's of the others so it's harder to convince them it's a fuel problem. If Marine5 had gone ahead and just opened the breaker on the MG that still had load the other would have lost cycles and maybe tripped off, the captain doesn't like going in the dark, glad he didn't do that. But if he did and it didn't trip off he's got a fuel delivery problem from the day tank, he doesn't have enough fuel being delivered to run 2 MG's but enough to run the load on one.

THAT'S IT and why his problem moves from one MG to another.

HE HAS A FUEL PROBLEM BETWEEN THE DAY TANK AND THE MG SETS. Enough fuel being delivered to run his hotel load on one engine but not enough for two to run at the same time.

You reading this Marine5? Check your day tank pump and/or filter.

What I have found most useful on the rigs is to have digital Mv scales on each generator control bay indicating the true power or signal being sent to the governor.

This at a quick glance will tell you (or at least point you) to the problem

Absolutely no disputing your GA by any means... As the TC on the rigs I have mediated this argument with electricians and mechanics time and time again.

Tim

The best thing that can be done for the Mechanic and Electrician Tim but a Ma meter is better for the first one, governors being and electric over hydraulics we read Ma's for seeing a better picture of what the speed regulators are doing in relationship to each other. Mv meters wouldn't be useless, Ma's are just better.

Now if you put both a Ma and Mv meters on each speed regulator output to the governors you can tune the stability and gain (like on the old analog 2301's and GEM's) pots for the highest Ma and lowest Mv and be within 10% of optimal for response and load sharing. Then you can stop troubleshooting that start on the voltage regulator and/or exciter when you have generator loading problems and you don't have to use a hammer on the rack so much to see recovery.

A long white wood stick wire-tied to each governor arm helps a lot for looking down a row of MG's and seeing the position of each on as they run, especially the CAT's and EMD's where the actuator is down in the hole and the rack linkage under covers.

The fuel seems a reasonable solution, though if this does not remedy the fault, then the issue may well be simple load start weight - most electrical items draw a vast amount more at start up than when running even a simple air conditioner or fridge draws more than double at start up. Refrigeration or starting compressor units is often a cause of such issues. we see the problem with inversion all the time. the 490kw really is small for a 200kw running draw for start ups, you would be very close to the line.

I don't know what sort of ship you have, but if it is running refrideration or freezers then you may want to do a simple amperage test of the units at start up.

Synchronized change-over does not invoke start-up or inrush loads.

It's 99% "fuel starvation".

GA belongs to kwcharlie.

it looks you have a problem with block loading of engines,you need to know the block loading charters of engines form engine manufacturer's,then program engine governors and your synchronising module accordingly you could solve your problems

murali ex-caterpillar application engineer.

Have you every tried the other way round by starting #1 and #2 and then changing the load to #3. As 'crm' said there might me problem with the block loading of engines. until the above is confirmed we can't come to a clear conclusion.

Hi guys

Sorry for late reply.. was in the engine room n back in my cabin for lunch..

Even I was suspecting some blockage in fuel line of #1 or 2 but on moitoring the F.O pressure I found that there wwere no fluctuations in the fuel oil pressure when generator started, came on load and during normal running. The pressures of all the 3 geenrators are equal.

I would like to point out that i found the governor actuator of #3 stuck ..

It was supposed to be moving in the slow direction ( anticlockwise) so that fuel goign in #3 reduced

While the governor actuator of # 1 went on turning in fast direction thereby increasing the fuel going in #1. Probably some sensor sensed that #1 was still not sharing equal load on busbar and kept giving signal to the governor actuator to turn in fuel increase ( fast) direction.

Could this be because,, the governor actuator of #3 was stuck and so the fuel going in the generator wasnt decreasing .. so generator wasn`t shedding any load when it should have?

Now wat I dont undertsand is that.. if the fuel to #1 went on increasing.. what is this extra fuel being used in? Is the KVAr increasing, or is #3 drawing current from #1 .. whats happening?

What do you guys say..

I`ll try to upload a pic of the governor actuator motor that I am talking about in the evening.. taking my cam with me right now to the engine room.

Not sure if we can upload pics in posts in this forum.

Problem: If the fuel increase on #1 keeps going to full rack, then your #1 speed (rpm) should have increased and drive the gen set out of sync.!? or take over the load from the #3.

Load sharing is not just an electronic device that does the sharing by some magic. the engine rpm must be kept steady at the required frequency, within a narrow error ( the other engine will pull or get pulled so that both engine will run in sync.....

Therefore, something is wrong with the mechanism controlling the fuel supply. The rack lever maybe going to maximum but the fuel is not getting to the engine otherwise you should have had a high speeding engine!, and a frequency increase... the #3 will also be driven up the rpm since its rack is also increasing without a load increase...? We need more info and details: rpm readings, voltages and amps independent from the kW readings, ...

Check your fuel supply lines (valves, filters...) and the racks linkages to the actuators, also the rack lever to the injector pumps...

Exactly LAA Lucke

That is what I have failed to understand:

If #1 fuel rack is increasing to maximum , why don`t I see an overspeeding engine? And if the engine is not overspeeding that means the fuel is being consumed to generate power..

This is what happened the last time I tried paralleling #1 while #3 was already on load:

. Started #1

. Pressed auto synchro- #1 got synchronized and ACB closed.

. The load was about 200 KW

. #1 slowly started taking load while #3 started shedding load.

( I am sure you must have heard a set of sounds from the switchboard when we parallel 2 generators.. the tak- tak sound, corresponding to the signal sent to two governor motor actuators. We hear the same sound when the frequency of the generator has to be corrected when the frequency has either increased or decreased due to starting or stopping of a large load. )

. When #1 was about 90 KW and #3 was 110 KW, both the KW readings got stuck on 90 and 110 KW respectively. The set of Tak Tak sound ( i dont know how else to explain this) stopped.. Instead there was only one Tak sound coming from #1 generator panel .. No sound from #3 panel.

. At this time, the fuel racks of #1 read 17.

. The KW readings remained stuck at 90 and 110 respectively. The Tak sound still only coming out of #1 panel.

. The fuel racks of #1 increased to 19 and then 20.. went on increasing..

. now I didnt notice the frequency increase on #1 panel at that time. i should have.

. I hurried to #3 and noticed that the governor actuator knob is neither turning in the slow direction ( fuel decrease direction) nor in the fast direction ( fuel increase direction.)

. At this point of time I heard the knocking sound coming from #1. If you know The sound that you hear when you push too much, the fuel rack of any unit. its a knocking sound.. n I have heard it in generators when too much fuel is going in.

. I manually tried to turn the knob in slow direction as #3 was still to shed about 20 KW for both the generators to share equal load.

. i found the knob stuck when i tried to turn it.

. I applied more force in the slow direction and was able to turn it.

. but the moment the knob became free.. i experienced force, turning the knob in oppositte direction i.e fast direction.

Do you think this force in the fast direction was applied cuz the generator #3 got pulled to increase its frequency to match the busbar frequency?

. Now I didn`t notice the frequency of #1 when its rack started increasing cuz I hurried to #3 to check on its governor actuator. I should have checked the frequecy increase on #1.

. What would happen if #1 speeds up in this situation, while the KW readings are stuck, but #3 fuel racks remain stuck and the fuel input neither increases nor decreases?

. When I reached the control room I saw that now, after the governor actuator of #3 had turned in fast direction.. #3 was sharing 150 Kw and #1 was sharing 40 KW.

. I put both the generators to manual mode and manually offloaded #1.

. Now suppose the fuel is not getting to the system: The fuel pressure gauge would show it right? The pressure gauge measures the pressure between the fuel oil filters and Fuel oil injection pump inlet line.

I saw that the fuel pressure remains steady throughout. at 6 Bar.

. I let the generators run for sometime and then pressed auto-synchro again. This time the #1 ACB closed and the generator came on load without any problem. #1 and #3 KW readings settled at equal values..

. Then I offloaded #3.. n everything happened normally.. no problems.

You are correct: the next time this happens.. I am going to record the changes in RPM, frequency and current.

But I am quite sure that the governor actuator of #3 was stuck when I tried to turn the knob by hand. I had to apply some force to turn it.. and it suddenly got free.

Thanks, Mariner5. Some of us have little knowledge about generator synchronizers, and maybe this is a chance to ask some questions and learn something. You have three 490kW generators with #3 running, delivering 200kW to your load. You auto-sync add in a second generator, #1, and the two balance to equal RPMs, and nearly equal phase relationships, delivering nearly-equal 100kW power, except off by 10kW or within 2% of nameplate, which seems good enough.

You try to manually over-ride the servo on #3, and it resists (sticks) - that sounds good. Isn't the servo supposed to make them continue sharing (as it thinks they're doing)? Thinking it's stuck you turn harder and force #3 to take over much more than half of the load. Which is does. Everything's still OK, right?

Q. If at any point after the 10kW 2% near-equality was reached, or even after your intervention, you were to off-line the 1st generator, #3, the new second generator, #1, would immediately deliver the full 200kW load, because it's already at the proper speed, and it would no longer have the first generator competing to have the most-advanced 60Hz AC phase to deliver more power, right? It'd see the extra 2x load and start slowing down, with rotary inertia helping to maintain speed, and the servo would sense a slight frequency drop and push it back so there'd only be a nominal blip effect, right? Normal operation, right?

I don't understand the fuel-rack scene, but isn't the multiple-generator synchronizer working properly? Doesn't 90+110kW qualify as "equal" within spec, like 100+100kW?

#3 actuator couldn't have been 'stuck' since it came up to speed to go on line to start with held its own until it was paralleled with another unless you have an interment actuator problem but that defies Occam's razor and the KISS principle so lets not go changing out actuators yet.

Still thinking about it, still thinking you have a fuel problem BUT not sure now.

What do you have running your actuator Mariner5, a 2301?

Hi Kwcharlie

I only face this problem of KW readings getting stuck when #3 is already running and I am trying to put onload #1 or #2.

This time also #3 was already running. #1 was the incoming generator.

The governor actuator is a dc motor which recieves a signal from the switchboard to

either increase the governor rotation or decrease it. The motor does so by either turning in the fast direction or the slow direction. When the motor turns a spring is either compressed or decompressed which in turn increases or decreases the fuel to the generator engine.

Besides this dc actuator motor, there is a knob which can be manually turned and does the same job of compressing or decompressing the spring in the governor.

OK, thinking electrical now. It's not the actuator since it drives the engine to speed but it could the signal into the #3 that tells it how many amps are coming from it. If the wire was broken, or that CT bad in the switchboard, #3 may think the load has been shead and not lower the rack anymore. The actuator works in island (no other gen's on line) because it just looks at frequency to slave the actuator to. In load sharing it has to see the current. That doesn't explane why you get full rack on the others UNLESS your going into reverse power.

If all that fuel was going to KVAr's you should have warmed up your generators at least, fuel equals KW that's why I don't think you "really" had a full rack worth of fuel going to the engine. If you were driving the other generator with that fuel you should have tripped out on reverse power, even the old MMS makes you test your reverse power relay.

Now be careful checking the CT, NEVER NEVER NEVER disconnect the wires on a CT that's on a bus that's hot, you'll draw a LONG spark as the circuit opens and the CT acts as one side of a big step-up transformer.

Do what they taught me in the USAF to check in this order:

1. VISUAL

2. MECHANICAL

3. Now check the electrical stuff.

Look at everything inside the switchboard, check it mechanical for broken wires, burned spots, parts operation BEFORE getting out your meter.

BE SAFE

It certainly sounds like the problem is associated with generator #3 - either a mechanical obstruction (could be fixed eg a burr, rough patch or other damage, or movable, eg debris, some swarf, a nut or washer, or even a loose guide, or wear allowing too much movement in an unintended direction) or an electrical control issue preventing it shedding load.

If I remember correctly, a generator can also act as a load to some extent if there is more power on the line than it is generating.....

I have same issue here. Just now. If i synchonize #1 generator, with other genset, it reached only 15% load. And fuel index start increasing to full. But rpm drops making a knocking noise. Turns out to have smokey exhaust. I was suspecting a fouled turbocharger.

Please help guys. I need a quick response from professionals.