Sizing transformer

[HienN]

Hi all,

Today, I bring a new question that hopefully it is worth for a while thinking.
We got a new project of a Cryogenic plant. This is also my very first big project. The electrical equipments specification is as was following:
Air compressor (02 sets): 6.6kV_2056kW_Reactor starting
Recycle air compressor: 6.6kV_3500kW_Reactor starting
Oxygen compressor: 3sets; 6.6kV_800kW_DOL starting
Three options: Transformer with 6.6kV_15_17_20MVA (Z%=7)

During this very first phase, information is quite unclear. These motors will be started one after the other and could be explained as followed: AC 01; AC 02; and RAC (and then 03 Oxygen compressors).

The question come up is how to determine the initial transformer capacity to avoid the voltage drop to allowable value?

As the presence of many of experienced people here, theoretically and practically, I look forward to receive your suggestions to get forward.

Regards,

HienN

 

[HienN]

Thank you for all of your useful posts.

I confirmed that the base capacity of 110/22kV Transformer is 40MVA. Z% is at 13 percent. The next step is how to calculated the short capacity at the source?

Is that SC capacity at the source is ~300MVA?

When sizing the transforme capacity, why we need SC capacity? Is it just needed to base on the total capacity of motors?

Any suggestion?

Attached pls. refer to the SLD.

 

[rbulsara]

Your questions have been answered earlier. You should be able to take it from here. I or this site cannot be responsible for your design.

Rafiq Bulsara

http://www.srengineersct.com

 

[HienN]

Rafiq Bulsara,

Many thanks to you for the valuable supports. I will do it myself.

Regards,