motor starting simulation 1

[TusharB]

I am using SKM software for performing Transient Motor Starting analysis. Actually I have modeled the same network in ETAP software also but I am getting different results for P.U. volatages on Motor buses & Generator buses. Now on which software I should rely? Please guide me..

 

[davidbeach]

First, are you positive that you are modeling exactly the same thing in both software packages? If so, it sounds like it is time for some detailed hand calculations.

 

[dpc]

How different are the results?

 

[TusharB]

Thanks Davidbeach & DPC. Yes I have correctly modeled the network with same data in SKM & ETAP. The difference in P.U. Voltage is 0.6 PU on motor bus. Even one of my friend also modeled the network in PSAF software from CYME & he also getting same results as in SKM. Now I dont know which are giving correct results?

 

[rbulsara]

Look for differences in default data that programs assume if you do not fill them out.

What is the % difference. 0.6 pu out of how much?

 

[dpc]

If you're just looking at the initial voltage dip at locked rotor, this is "relatively" easy to calculate manually.

The other thing I would do is to do fault calcs at the closest bus to your motor in both models. If networks are modeled identically, your fault currents should be nearly the same.

Next, I'd run a normal power flow without this motor starting or running and check results in both programs.

If SC and PF results are in agreement, the difference must be in the locked rotor model of the motor under start.

I'm not familiar with either program, but they have to make assumptions on starting power factor or this data must be input by the user.

Lastly, look at the kw and kVAR flow into the motor under start in both models.

Let us know what you find. It's an interesting problem.

 

[redha123]

HI
You can test the two software, by using a known exempel, try a simple circuit with one source and one self (if you want R+jX) but constant R and X.
compare with your calculation note !
still use P.U .

 

[DanDel]

0.6 pu would be 60%? Are you saying that in ETAP you have a 60% lower motor bus voltage at start than in SKM? What are the actual values for each, at pre-start and at start? Are you using the Static Motor start module or the Dynamic Motor start module in ETAP?