Hi,


We are currently in the shipyard, connected to shore power because our gensets are being overhauled.


Of course, frequency is now very stable at 50.02Hz.

Hi

Okay !

 

ControlsGuy25,

I think two things are going on here. First, the yacht is in drydock and gubavac111 is quite busy. Being in drydock also means the yacht is connected to shore power only, so the diesel gensets are not being used, AND he has said they are undergoing maintenance (probably changing oil, filter(s), testing compression, possibly even testing or replacing fuel injectors). It has been suggested that the problem could possibly be due to sluggish diesel governor response (or dirty fuel filters, etc.). So, it seems gubavac111 is kind of waiting to see how the units respond to islanded operation AFTER drydock, or maybe during some of testing before leaving drydock.

Second, I think gubavac111 is trying to find time to digest some of what's been written and try to apply it to his understanding and investigation of how the PMS on the yacht performs, and how the diesel governors are configured, etc.

And, all during drydock, which can be a very trying time--because time in a drydock is money, and so it's best to get in an get out as quickly (and inexpensively) as possible. Which leaves little time for reading and investigation.

But, it will end soon enough, and once the yacht is afloat and gets separated from shore power and needs to use the on-board generators we will get some feedback.

What I wish we knew was if this problem of frequency instability has been around since the original commissioning of the gensets, or if it's something which has started "recently" or has gotten worse with time since original commissioning. This would kind of point to either something with the diesel governors or fuel/air supply (dirty filters; bad injectors; loose or sluggish fuel rack(s); etc.), or to the PMS configuration and programming.

But, alas. Patience is a virtue, eh? And how many of us are virtuous?

 

CSA

I thank you for these notes
And I already understood anout drydock phase...

My question was regarding PMS ( If Gubavac111 had a time for a read on any Interesting documentation ...and if he got checked what we asked him to check like Parameters setted /tuned at this PMS...and if it is in accordance with any commissioning report /as builts .... OEM recommandations..

And as you clearly stated..that would be interesting to know if kind of problems ( as Gubavac111 explained ) are present since commissioning ...

ControlsGuy25

 

ControlsGuy25,

There is a suspicion this problem has been going on for a while--if only because the original poster said that a tech had made some adjustments "deep inside" the inverter (I think it was the inverter) to try to limit the issues they were having because of poor frequency control. But, that's just a SWAG (Scientific Wild-Arsed Guess).

 

Hi All.

So today still no updates from Gubavac111..
I keep mentioning to posters here, that we providing great efforts and good work/support... Help to them..
So give us some feedback on our work here would be greatly appreciated..

 

Ok so since more than 2 weeks that we did not hear from original poster ..
So we can say that this thread is closed...
Unfortunately we were ready to support and doing good efforts ..but sometimes here People just leave without any feedback....

 

S

Ok so since more than 2 weeks that we did not hear from original poster ..
So we can say that this thread is closed...
Unfortunately we were ready to support and doing good efforts ..but sometimes here People just leave without any feedback....

Sorry to disappoint you.

I have neglected this topic despite all your help.

My contract on the ship ended and I went home.

We stopped troubleshooting this problem and just left it as it is. It still persists, but we will do nothing about it.

That is the summary.

 

S

Sorry to disappoint you.

I have neglected this topic despite all your help.

My contract on the ship ended and I went home.

We stopped troubleshooting this problem and just left it as it is. It still persists, but we will do nothing about it.

That is the summary.

Thank you for you reply...
Much appreciated..
Any time!
James

 

I work onboard a yacht where we have 3 pieces of 765kVA diesel gensets composed of the engine MTU 12V2000 M51A and the alternator Stamford HCM634J2. The gensets are producing 3 phase 400VAC/50Hz.

First of all, I am not sure if there is even a problem with the gensets so here goes my first question:

1. What is the allowed frequency tolerance on these type of gensets or on diesel gensets in general?

Our frequency varies less than 1%, but even that is enough to cause problem with our Main UPS and Fire detection system which are sensitive to input power quality. Because of frequency variation, UPS does an automatic bypass (just transfers input immediately to the output) and Fire detection system has a Power input quality fault. Btw, UPS' tolerance to the input power can be adjusted and it is already at the max, although I don't know what the max is because it was done 2 years ago by the service technician on some potentiometer deeeeep inside the UPS.



So...this is the situation:

When gesets are working off the grid, their frequency is super stable.
When any of them is connected to the grid, there is a frequency fluctuation.
When 2 of them are connected, fluctuation is smaller and when all 3 are connected, fluctuation is smallest, but still bigger than when they are running off the grid.

Below table shows readings when only one of the gensets was connected to the grid. So, for example, when just Centre genset was connected, genset frequency (which is in that case grid frequency as well) varies between 49.67 and 50.33 Hz, current varies fluctuates around 50A and power around 25kWA.

f, kW & A readings (Analog meters)​	Port generator​	Center generator​	Starboard generator​	Time frame measurement​
Frequency on power analyzer​	49.75 to 50.15 Hz​	49.67 to 50.33 Hz​	49.63 to 50.28 Hz​	30 sec​
Ammeter readings on the main switchboard​	50 A fluctuation​	50 A fluctuation​	50 A fluctuation​	18 sec​
kW readings on the main switchboard​	25 kW fluctuation​	25-30 kW fluctuation​	25 kW fluctuation​	25 sec​
Voltage fluctuation on all three generators is from 400 to 402 VAC​

2. Do you have any idea what might be causing this kind of behavior?

You sure paralleling with Grid?
Normally one needs to get consent from utility company to do so, and they may impose some sorts of protections/decoupling controls to address safety and operational concerns.

Have you verified the shore supply ( or in your case you refer it as Grid) is stable of its voltage and frequency.

I been to certain small size ship building yards, and ship repairing yards in this part of the world, noticed some facilities distribution system lack of proper design. In those facilities often seeing many arc welding sets in service, sometime can expect noticeable flickering problems.

Have you ever used the "Grid" supply alone to power onboard system to check quality of power supply, such as voltage stabilities, harmomic distortions to identify the problems come from the source, or only present during paralleling between onboard generators and Grid.

Also interesting to find out how is the system grounding done onboard generators.

When parelling with Grid, both Grid and onboard generators neutral connected together, or only one source of Neutral is connected.

 

CH Lee,

gubavac111 took the vessel to shipyard, and they did nothing about the issue and his contract was over. He's moved on to other endeavours. This thread is "closed."

And if you read through the whole thread you will see we had a discussion about terms and usages.

 

Dear CSA,

Thanks for pointing out.

What an embarrasement to reply the post without realizing not reading through whole series of exchange of communications.

From the communications, I can see the sincerity and generosity from both of you to share the knowledge and help people out.

God blessed.

 

ControlsGuy25,

I think two things are going on here. First, the yacht is in drydock and gubavac111 is quite busy. Being in drydock also means the yacht is connected to shore power only, so the diesel gensets are not being used, AND he has said they are undergoing maintenance (probably changing oil, filter(s), testing compression, possibly even testing or replacing fuel injectors). It has been suggested that the problem could possibly be due to sluggish diesel governor response (or dirty fuel filters, etc.). So, it seems gubavac111 is kind of waiting to see how the units respond to islanded operation AFTER drydock, or maybe during some of testing before leaving drydock.

Second, I think gubavac111 is trying to find time to digest some of what's been written and try to apply it to his understanding and investigation of how the PMS on the yacht performs, and how the diesel governors are configured, etc.

And, all during drydock, which can be a very trying time--because time in a drydock is money, and so it's best to get in an get out as quickly (and inexpensively) as possible. Which leaves little time for reading and investigation.

But, it will end soon enough, and once the yacht is afloat and gets separated from shore power and needs to use the on-board generators we will get some feedback.

What I wish we knew was if this problem of frequency instability has been around since the original commissioning of the gensets, or if it's something which has started "recently" or has gotten worse with time since original commissioning. This would kind of point to either something with the diesel governors or fuel/air supply (dirty filters; bad injectors; loose or sluggish fuel rack(s); etc.), or to the PMS configuration and programming.

But, alas. Patience is a virtue, eh? And how many of us are virtuous?

Hello again!

I just wanted to give a small update since I am back on the yacht.

So, the gensets overhaul didn't help - the issues still persists.

CSA, you understand very well what dry dock is!

Looking through handovers of my past colleagues all the way to 2014, there is no mention of this issue.

That, however, doesn't mean the issue didn't exist, it might mean it was simply unnoticed because it didn't cause any real trouble in day-to-day operation.

I would LOVE to dive into this issue and just tackle it for 4-5 days, but that is just not possible with so many things going on in here.

When a guest pays 1.5 million USD for a one-week charter, the service must be superb and the tiniest detail must be taken care of - and this takes time.


Perhaps, there will be an opportunity in the future to work on this issue.


One more time, thank you for your generous help!

 

gubavac111,

We don't know exactly what was done during the overhaul of the gen-sets, so it's difficult to say if anything which might have positively affected the operation was done.

And, you mentioned that some tech was onboard and made some adjustments to some other piece of equipment.

Anyway, you seem to like this position--so ENJOY! And, if you get some time to work on this and get more data for us we'd be glad to try to help as best we can.

 

Hello again!

I just wanted to give a small update since I am back on the yacht.

So, the gensets overhaul didn't help - the issues still persists.

CSA, you understand very well what dry dock is!

Looking through handovers of my past colleagues all the way to 2014, there is no mention of this issue.

That, however, doesn't mean the issue didn't exist, it might mean it was simply unnoticed because it didn't cause any real trouble in day-to-day operation.

I would LOVE to dive into this issue and just tackle it for 4-5 days, but that is just not possible with so many things going on in here.

When a guest pays 1.5 million USD for a one-week charter, the service must be superb and the tiniest detail must be taken care of - and this takes time.


Perhaps, there will be an opportunity in the future to work on this issue.


One more time, thank you for your generous help!

Hi

All the best with this issue at your.. site...


Cheers
James