Ship Generators Problem Running In Parallel - KVAR Unequal

Recently been having problems on ship with our 2 Caterpillar 3406c Generators. Both generators are identical and both using EMRI CAT v2.3 AVRs.

When both are running in Parallel, both generators seem to be sharing load (kW) equally, but we are noticing these things:

Generator 1 has a much higher KVAR reading and lower power factor (around 0.5-0.6 ish) compared to the other generator. The main breaker for this generator is also showing much higher current values, sometimes even nearing 100% load on the breakers trip unit.

Generator 2 is reading close to 0 KVAR and sometimes it’s even going to around -3 KVAR, and it also has very close to 1.0 p.f. The current values on the breaker for this generator are much lower compared to the other.

We recently replaced the AVR and Rectifier Diode Bridge on Generator 1 as we had a problem with one of the exciter fuses blowing, which we don’t 100% know the cause for.

Any solutions or explanations as to why this is the case would be appreciated.

Thanks
 
Gregorb6
In all probability, and depending on the ship's age, the cause is related to a common, but simple, paralleling control-function called "Reactive-Current-Compensation", or just "Cross-Current-Compensation". I suggest you use the FORUM's "Search" feature for it as well as "Unequal Generator Load Sharing."
The problem is also relatively easy to trouble-shoot, at least in my day before the digital age.
Regards, Phil Corso
 
Recently been having problems on ship with our 2 Caterpillar 3406c Generators. Both generators are identical and both using EMRI CAT v2.3 AVRs.

When both are running in Parallel, both generators seem to be sharing load (kW) equally, but we are noticing these things:

Generator 1 has a much higher KVAR reading and lower power factor (around 0.5-0.6 ish) compared to the other generator. The main breaker for this generator is also showing much higher current values, sometimes even nearing 100% load on the breakers trip unit.

Generator 2 is reading close to 0 KVAR and sometimes it’s even going to around -3 KVAR, and it also has very close to 1.0 p.f. The current values on the breaker for this generator are much lower compared to the other.

We recently replaced the AVR and Rectifier Diode Bridge on Generator 1 as we had a problem with one of the exciter fuses blowing, which we don’t 100% know the cause for.

Any solutions or explanations as to why this is the case would be appreciated.

Thanks
Hi all,

First as suggested by Phil Corso , you should have some read if not yet on cross current compensation/droop mode compensation for Gensets operating in parallel.

Here is a link for a well explained principle of cross current and droop compensation:
http://www.pecplc.com/index.php/articles/control-of-synchronous-generators-with-droop-and-cross-current-compensation.

When you saying that fuses blowing , can you clarify .. is that Permanent Magnet generator called also PMG that you are talking about?

When fuses are blowing it is an indication that something is not good /operating properly.
That can be a burned diode, a short circuit, or something else...

Without be able to check the system drawing and alarms /trip log of controls system, it would be difficult to give more support.

Do you get any alarms /trip annunciated ?

I will have a better read on the original post and see if I add more comments for best troubleshooting.

Hope this can help,
Controls Guy
 
Check this very useful document to have better overview of what the system should do/work in smooth manner:

https://fr.slideshare.net/Otorongosabroso/cdvr-service-manual-renr794100-sis-caterpillar
It may not use the same AVR but philosophy remains the same!

The manual explaining lot of operations/tests method to get your system working properly according to the respective load .

Can you share a SLD ( single line diagram) of your electrical system, and also geenrator wiring ( exciter/field ...)
With these drawing we can have better overview and give better advices.

I am sure that can highlight you some points that you are looking for .

ControlsGuy25.
 
Gregorb6...
The simple trouble-shooting test I alluded to earlier was to short-circuit just the two CT's involved ! If load-sharing returned via manual-control then the cause was the Cross-Current-Compensation, or CCC function!
Regards, Phil Corso
 
Check this very useful document to have better overview of what the system should do/work in smooth manner:

https://fr.slideshare.net/Otorongosabroso/cdvr-service-manual-renr794100-sis-caterpillar
It may not use the same AVR but philosophy remains the same!

The manual explaining lot of operations/tests method to get your system working properly according to the respective load .

Can you share a SLD ( single line diagram) of your electrical system, and also geenrator wiring ( exciter/field ...)
With these drawing we can have better overview and give better advices.

I am sure that can highlight you some points that you are looking for .

ControlsGuy25.
Can the original poster give us some feedback....
 
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