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Generator modelling assumptions for power systems

Hi,

I have a scenario where there is a CAT synchronous generator that is rated at 700 kVA. The machine is operating at an off-shore oil platform. We were to model the machine in ETAP to perform a power system analysis. However, the impedances (in pu) and the time constants that we have got for modelling this generator is of a 717 kVA machine. Is it fair to assume this machine's (717 kVA) impedances in pu (per unit) for the other (700 kVA) machine? If yes or no, why?

This is my first post in the forum and I am eagerly looking forward for some brillian replies as I see in the other conversations here. If my question is not clear, please let me know.

Regards,

Bala

Super Contributor

Re: Generator modelling assumptions for power systems

If the arrangement number of the actual generator and the arrangement of the data you have match or are compatible arrangements then the data should be good, although I would use the data sheets rating for your modeling.

 

CAT tends to use a single frame and base arrangement for multiple applications and rating, however if you are dealing with a tailend specfically designed for oil field applications its application and ratings range will not be as broad.

 

If you post the serial and arrangement numbers in your request you might have someone with CAT TMI access who can take a look and make sure the data actually matches what you have.

 

Hope that helps, MikeL.

 

 

Visitor

Re: Generator modelling assumptions for power systems

Mikel,

 

Thanks very much for the input. The Seriel number and the arrangement number are very much blurred. However, from what I could read, it must be- L7A03398 or L7A03308 (Seriel number) and 371-1766CY (arrangement number). It is made in Czech Republic. Frame: LC7024F.

Looking at your reply, "CAT tends to use a single frame and base arrangement for multiple applications and rating", should I assume that the impedance values in ohms could be the same even for machines with different power ratings that are very close (690 kVA, 700 kVA, 710 kVA)?

 

Regards,

Balaji