Paralleling 2-cycle and 4-cycle diesel eng gen sets

[meihm]

"Facts"
Existing facility has three 400 KW 2 cycle diesel engine generator sets and wants to add a fourth 400 KW 4 cycle engine generator.

Pitch of new generator is not same as existing generators, but is "compatible".

Question:
Because 2 cycle engine has a much faster recovery time (from lump loads dropped on paralleled system) than the 4 cycle engine, am I facing circulating current problems?

What problems are likely?

 

[PwrCntEE]

I do not have much hands-on with generators, but have reviewed some layouts. With proper monitoring, protection, and syncing before allowing them to close together, as with any multiple source system. I do not see a problem with engine type.

 

[alehman]

The generators probably will not share load transients equally due to the different behaviour. It is not unusualy to operate units of different rating in parallel so I doubt your situation would be a problem. The difference in winding pitch would concern me more. That can lead to circulating harmonic current.

 

[jbartos]

Suggestion: Contact the Diesel Generator Set manufacturer(s) for tech support.
There are various items that do count during the genset paralleling, e.g.
1. Speed governor control parameters that influence the genset transient and steady state characteristics
2. Automatic Voltage Regulators (AVRs) that influence voltage dips.
3. GenSet Protective relaying schemes
4. Etc.

 

[dpc]

I don't see 2-cycle vs. 4-cycle being any kind of problem for normal operation. As for the winding pitch, if this is a low-voltage solidly-grounded system, you should get assurances from generator supplier as to expected level of third-harmonic currents and any necessary derating of the generators.