Engine Governor Control 2

[HamidEle]

A couple of basic questions about Diesel engine Governor control:
The speed droop is adjustable from 0 to 10% or 5% . Is 10% better ?
What is the steady state frequency regulation ? I was told it is 0.33%. It doesn't sound right.
Any input would be appreciated.

 

[waross]

3% Droop, Hamid. The governor should be set at 61.8 Hz at no load, dropping to 60 Hz at full load. Most users won't know the difference. Some UPS units may not like the frequency variation and synchronous motor type electric clocks may run fast. Other than that, the frequency variation is unnoticeable.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TheBlacksmith]

If the generator is stand alone, you should be able to run isochronous/0% droop. If paralleled with another power source, 3% droop seems to be the most common. Ten percent would be very noticeable and in my opinion, unnecessary. My units are adjustable to only 5%, but we are using 3%.

 

[waross]

Isochronous still has 3% droop. The first response of the governor is proportional based on the droop setting. The governor/controller then detects the frequency error and corrects back to the set frequency. Droop implies a method of describing the settings on a proportional controller that is easy to use for generator control.
Droop is proportional, isochronous is proportional plus integral.
3% droop is a good compromise between tight control and stability.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HamidEle]

Thanks for the reply. You were saying frequency variation of 0.33% is acceptable under steady states since they are unnoticable?

 

[HamidEle]

I often see 0.5% of speed ( frequency ) variation on Diesel generator specifications. Some vendor indicated you can do with 0.33%. Should i choose the one with 0.33%?

 

[waross]

What size set is this and what is the load?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HamidEle]

2.5MW to 3MW. Load is ~2MW

 

[HamidEle]

100% redundant. 2 Gen-sets will be operating in parallel with one taking only ~%50 loads.

 

[waross]

I was wondering what type of loads so as to anticipate any issues that may arise running on generators. For an industrial site running both sets at 3% droop should work fine.
If there are offices with a lot of computers and small UPSs you may have some frequency issues.
You can consider a load control panel to run both sets in isochronous mode. You may still get some momentary beeping from the UPSs when a heavy load hits.
Catserveng is more familiar than I with load control panels.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

I guess I'd start with "it depends" on the droop setting. Usually 3% is considered pretty standard, I have recently setup some larger units at 2% per the customer request, a newer design digital governor allowed very good tracking after getting it adjusted so for that application it appears to have worked quite well.

Larger droops are usually applied to industrial drives and engines driving equipment, typical on-hiway truck engines with hydra-mechanical governors had droop from 6 to 10%, about the same with marine propulsion engines.

I rarely apply speed droop settings in systems I work on as they are all isochronous load share systems using a Woodward, Basler, ComAp or similar load control systems, especially on engines with integrated governing in their ECM's. In some cases if required and the controls are setup for it we apply 3% speed droop for a manual control mode if the engine controls can use an input to switch in and out of droop.

On the steady state frequency, the spec usually comes from ISO 8528-5, performance class (grade) 3 is at 0.5% for steady state frequency. Depending on engine size and things like fuel systems and turbo's, steady state frequency can be improved but usually at the expense of poorer transient response, at least in my experience.

Hope that helps, Mike L.

 

[powerjunx]

well said, cat!
i've seen marine diesel generator-set attains 3-5% droop max.(woodward governor) however; 10% droop is unusual for generator application.



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