Simple Power flow calc 3

[advidana]

Hello :
I need information on performing a small power flow from a 3000 ft radial underground 12kv line to two small office bldg 5000 sq foot each. The client wants the study done with software.

I don't think he wants to model the complete utility system serving this bldg but maybe so. But I don't normally do load flow on small systems. I have done load flow on utility to many bldgs before using Dapper and Capper and Etap. but I don't have a license to use them any more.

What I specifically need to know is suggestions of any accepted industry practice of how to model the source if the source is unknown. If that is possible.

I also need information on an getting inexpensive software that is as easy to use as dapper and Capper( I also need to do some coordination curves)and Etap but except for small systems.

thanks

 

[advidana]

I forgot to add that I will ask client for the sending end (swing bus)deliver apparent power. Client own the local 12Kv distribution line and HV transmission line feeding it.

 

[davidbeach]

Sorry, but either you have the tools and can do the work or you don't have the tools and can't do the work. If the customer's contract states that the engineering service should include certain items, no matter how uncustomary, it is your obligation to come to agreement with the customer regarding those items prior to signing the contract. Perhaps you could sub that work out to someone with the tools desired by the customer.

On the other hand, I have heard of, but don't remember the name of, nor know the capabilities of, an open source and/or freeware power system analysis package. So what you are looking for may exist, but whether or not it will be acceptable to the customer depends on their requirements.

 

[ijl]

For freeware, see

http://pp.kpnet.fi/ijl

http://www.dpannhorst.de/

http://www.interpss.org/

 

[advidana]

Thanks for the advise and free software sites. I will recommend that my boss either buy the software needed or out source the load flow calcs.

I still need to know any accepted industry practice of how to model the source if the source is unknown. If that is possible.

 

[advidana]

Found out that if source is unknown just use the tranformer kva size I will put in to serve the build and it's X/R ratio.

I hope this will help someone else with thier design calcs.

Thanks all

 

[advidana]

Typo for "build" on last entry should be "building".

 

[DanDel]

You will need a source on the line side of that transformer. This is necessary, and using a maximum value ('infinite bus') will not give you the correct (conservative) results for a LF study. You need the actual value from the Utility; you should ask for the lowest value (minimum fault) for the LF study, and use the maximum for a SC study.

 

[advidana]

Yes I will ask for that and also the X/R for the utilities. But I may not get it. Thanks again