Induction Generator - Rotating Machinery Characteristics

[LFG2E]

We could use some help with a 273 KVA induction generator w/capacitor bank that we are installing on a landfill gas-to-electricity project. The local utility, is requesting the following information:

Direct Axis Transient Reactance, X'd
Direct Axis Unsaturated Transient Reactance, X'di
Direct Axis Subtransient Reactance, X"d
Generator Saturation Constant (1.0)
Generation Saturation Constant (1.2)
Negative Sequence Reactance
Zero Sequence Reactance

Our problem is that we cannot locate this information. I've attached a photo of the generator name plate that shows "Induction Technologies, Inc." and "Unisine". We've exhausted all efforts to track down these companies. The original motor apparently has been re-engineered and reworked by these companies and that neither are now in business.

Can anyone help?

 

[esee135]

If you're in desperation, you could always pay a current manufacturer that sells a similar product to perform testing/simulation results for your unit. For synch-generators the manufacturers don't really mind providing studies for non-OEM machines so long as you have the money to pay for their engineering. May not be the cheapest option, but it is a decent option if you are unfamiliar with performing tests to extract the 'model' data.

 

[LFG2E]

Thanks esee135, we do have a budget line item for testing. We disassembled the unit as far as possible looking for clues as to the original manufacturer but did not come up with anything. We noticed that at least two interconnection applications for other utilities contain the statement below the "Rotating Machines Characteristic" data:

Note: Please contact the Utility prior to submitting the Interconnection Request to determine if the specified information above is required.

We're spoken with a few power distribution engineers and hear that for such a small generator this data is pointless anyway. Any thoughts on this?

Thanks again!

LFG2E

 

[rbulsara]

Only the generator manufacturer can provide this information.

Alternative is to use typical values found in power analysis softwares. But the utility co. may or may not accept those.


Rafiq Bulsara

http://www.srengineersct.com

 

[esee135]

For synchronous machines, they have the ability to simulate a non-OEM machine, there will be accuracy issues, the OEM always knows their product better.

 

[ters]

I would find typical values for a similar machine (same speed/number of poles, same voltage, comparable output, etc) and submit. And let them prove than numbers are not very accurate, if they can

Utilities typically ask such questions when doing a System Impact Assessment (SIA), to determine as how your generator is going to impact their system, and then will make you pay for modifications, if there is an impact they don’t like.

On several occasions I have dealt with similar requests, when our Clients wanted to build a small hydro generating station and after having only a conceptual design which determines basics such as machine speed, output power and voltage level at the best, they than apply for SIA to see what sort of surprise will face when connecting to the grid. At which time they face the same questions as what is Subtransient Reactance X"d of a machine which doesn’t exist yet (has not been even ordered yet), nor make and model is known. This is a situation when only typical vales can be submitted.

I cannot picture that, if in your case typical numbers are off even 50%, it could make a big difference as how a small machine of less than 300 kVA will have a very different grid impact, unless you are connecting to a low voltage network. What is operating voltage there?

 

[wolf39]

LFG2E:

Testing this unit for obtaining the reactances required by the utility would certainly cost more than the unit is worth. I would recommend to scrap this generator and look for a second-hand unit in the marketplace with known characteristics and known history. But contact the local utility before purchase.

Regards

Wolf

http://www.hydropower-consult.com

 

[waross]

May these values be estimated from the characteristics of the machine when started as a motor?

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

 

[Kiribanda]

LFG2E,

May be you are planning to generate elect energy using this Ind. motor by running it as an Ind. generator and connected to the Utility grid.Therefore,you will find the above mentioned parameters in your Utility interconnection contract forms.

To my knowledge the sub transient and transient reactances for direct & quad axes are related ONLY to syn machines.Your name plate shows that it is an Ind. machine working on completely different principle.Therefore, those parameters are not available for an Ind. machine.You will have only the impedance of the motor which even you can find out from a text book or can be estimated by the starting current.

Any comments please.

 

[esee135]

'Kiribanda' has a point. Xq is an method for mathematically explaining the effects of saliency of a pole (interpole air gap).

As another note, the service for modeling an induction generator should be available since there are several cases of wind energy machines. In fact, doubly-fed induction wind generators are arguably more popular for master thesis' than the fuzzy-logic power system stabilizer.

Anywho, every form of induction machine seems to make it's way into wind energy implementations, and I could only assume that someone provides a modeling service, especially since generator modeling is such a hot topic with compliancy these days.

 

[LFG2E]

Thank you all for sharing your perspectives. We will be connecting this unit to the AEP grid and selling power. We're very close to concluding that much of the information that is being requested on the interconnection application does not apply in this case. Before we try "explaining" this to AEP we will be doing a bit more research. And by the way can anyone identify the motor OEM from these photographs? Our best bet (at this time) is Toshiba.

 

[LFG2E]

Photo 1

 

[LFG2E]

Photo 2

 

[wolf39]

LFG2E:

How can I open the photo files?

Regards

Wolf

http://www.hydropower-consult.com

 

[LFG2E]

Thanks Wolf, I believe you can find the photos at

http://www.eng-tips.com/viewthread.cfm?qid=260876&page=1

Steve