Diesel & Gas Gens Sync. Problem 3

[tamerbeeh]

We have two generators , One is CAT Diesel and Other is Gas , When we try to synchronize them together , a large fluctuation in voltage and frequency occurs in the Gas generator and power readings varies from (+ve to -ve) too , Any suggestion or even where's the problem ?

 

[ivymike]

what method are you using for load sharing (isochronous/droop/?), and what are you controlling with?

 

[mechanic6]

hi
assuming that your synchronizing controls and procedures are ok,then its likely the governors are not compatible.
the Cat genset probably has a very precise goveror,whereas the gas engine may not.

could you tell us what engines you are dealing with?

thanks

 

[catserveng]

You will need to provide way more information to get a usable answer. I work with gas and diesel prime movers in the same network all the time.

There are a large number of things that could cause the issue you're seeing, and without a better description of your system you won't be able to get many answers that would likely help.

How about to start, the make, model and rating of the engines, type of governor, type of real power load sharing controls, generator type, AVR type, reactive power sharing control type?
Details on the gas engine, type of fuel, NG, landfill, digester, etc, is it low emissions rated, is it carburated, charge density or mass controlled?

Is this an island mode system, parallel to a grid or a large or small network?

Is this a new system and these are intial problems, or did the system work ok after install and now has a problem?

Mike L.

 

[tamerbeeh]

Thanks so much for your replies , and here's the information you are asking about;

@ivymike; With all modes from Diesel CAT. Gen or Gas Gen. fluctuation occurs EXCEPT when we operate the CAT. on Droop mode and GAS on ISO. , In this case only there's no fluctuation and all systems are stable.

@mechanic6; I have read that Governor might be the problem as the one installed in GAS gen is Electronic while the Governor in Diesel CAT. is mechanic , but I need to be sure that this is the problem to start dealing with it , Also i want to say that there's another Waukesha GAS gen. which have the same governor (mechanical) (same model) when we sync. it with the CAT. diesel , all systems are stable but not with Guascor (The Gas gen which am asking about which have the electronic Governor).

@catserveng;
Engines; 1. DIESEL CAT ENGINE (1500KW) , 2. GUASCOR GAS ENGINE (450KW).
GAS Type; Natural gas.
Governor types: For diesel: Mechanical , For Guascor GAS; Electronic
Island mode: yes i think there's island mode
Problem type: yes it's initial , they didnt sync. normally ever before except when i put diesel CAT gen on Droop mode and Guascor on ISO. (Please read my comments to others engineers above)

Thanks and waiting your replies.

 

[tamerbeeh]

Where did you go guys?!

 

[ivymike]

the gas engine can't match the transient load (load acceptance) capability of the diesel...

not sure what your load sharing controller is, but if you can do it you probably want to baseload the gas genset and let the diesel handle the transients.

then again, if you have stable operation w/the pair as mentioned above, why change anything? (what are your goals, and are they being met?)

 

[tamerbeeh]

We need all of Gens to be operated in ISO. , Non in DROOP mode .. and Even when we put Gas gens on base load and diesel on ISO , Fluctuation occurs.

I told you , the only mode that the process is stable in it when Diesel gen is on DROOP and Gas gen is on ISO. mode.

So what do you think the suggested solutions for it ?! We need to solve it urgently , so whatever information you would like to get , just ask me and i can tell you.

and regarding to your reply "I didnt understand the part of the gas gen can't handle the load acceptance of diesel , could you say in details?"

Thanks and waiting yr reply.

 

[catserveng]

If the diesel truly has a mechanical governor, like a Woodward 3161 (most likely) or a UG8, then it will not parallel in isoch, it has to be in droop to share, this is why you get the instability. If the Waukesha with the mechanical (likely hydramechanical like a Woodward UG8) parallels ok with the diesel with the hydramechanical governor then likely the Waukesha governor has some droop dialed in.

To have an isochronus parallel system you will need an electronic governor, like a Woodward 2301A on the CAT diesel, and a load share system compatible with all three governors. That will take care of the real power sharing. Since these are all different tail ends as well you will also need to either do VAR share in voltage droop, or use an active VAR share system. A cross current compensation system will not likely work well in this case.

What kind of electronic governor is on the Guascor engine?

Ideally if you currently have a hydramechanical governor installed on the CAT then the best conversion option is a UGA actuator driven by a 2301A governor. The factory installed electroninc governor actuator for a 3500 CAT mechanical engine is an EG6 or EG10 (depends on vintage) and has a very different mechanical drive arrangement than the hydramechanical governor.

If the Guascor also has a Woodward governor then a compatible load share system could be fairly easy.

The gas engines have very different dynamic response rates than the diesel unit does. The diesel engine driven unit has the ability to much more quickly respond to load changes, as your system load changes the diesel will respond to it first, especially if it is in isoch, as it only wants to get back to rated speed as fast as it can. the gas engine driven unit tries to also maintain the rated speed set point, but ends up always being behind the diesel, so you get a load change back and forth as the two governors both try to make their engine run at rated speed with no means of telling each other what theya re tyring to do.

Sounds like you're new to this, try this link to Woodward publiations and search "Power Management" or publication 26260.

http://www.woodward.com/InteriorTemplate.aspx?id=826&terms=woodward publications

This is a very good explanation of how governing systems work especially with regards to parallel systems.

Hope that helps, Mike L.

 

[tamerbeeh]

Let me edit some information incase this would help , CAT Diesel doesn't use Governor but it uses "ECM" , and Waukesha gen uses "Electromechanical Governor" , and Gauscor uses "Electronic governor" , Please check if this information will change yr answer or not.

 

[catserveng]

The CAT unit using "ECM" means it's an electronic engine with a CAT embedded electronic governor. It will have to have some means of provinding a remote speed and droop reference, two most common ways, a CAT 'Speed Brick" or a Woodward Load Share Module (LSM).

On the Waukesha, what kind (make and model) of "electro-mechanical governor"?

On the Guascor, what kind of "electronic governor"?

Still need to answer the question, are you using any type of load control system overall? Load share lines, active controller like a DSLC or GCP? Something else?

Mike L.