Originally posted by: westonpa
The tertiary winding is installed for several main reasons and thus you just need to prove that the transformer is being used for applications which do not require it, i.e., those things the winding seeks to solve are not an issue for that particular application. Thus you really need to look at, and understand, the applications. Alternatively you need to prove that there is another method for solving the application problems which does not require the tertiary winding.
However do appreciate that if you were for example producing 5000 transformers and 4750 were for applications which did require the tertiary winding and 250 were for applications which did not require it albeit it did not cause a problem for those applications by being fitted, then it would likely be uneconomical to change the production processes for such a short run.
Suggest you get this book:
J & P Transformer Book (Thirteenth Edition)
You can either view part of it via Google books......use IE and Firefox browsers because they allow you to access different pages and thus you get to view more. Alternatively you can access it via Science Direct at:
Either you would need to join or check if your university/college has educational access. Most UK universities do and thus UK students can access the book at no cost to themselves.
Thanks for your reply, i really appreciate it.
For the J&P transformers hand books, i already have the 12th edition and i hope there is no major different between the 12th and the 13th one. I haven't finish the books yet, especially the 6th chapter that explain the operation and maintenance of the transformers. I'll read and try to understand it soon..
as far as i know, some main reason to provide the tertiary winding on a transformers are:
1. Improve voltage regulation if there are unbalanced line-to-ground loads
2. Protection of the system and transformers from excessive third harmonic voltages.
3. Facilitate the relaying of system faults
and from further study and discussion, i've some answer for those reason..
>for the first reason, because the transmission line do not supply any load directly, i assume there is no unbalanced line-to-ground loads.
>for the second reason, in those paper i've mentioned above, they had tested the harmonic on transformers without tertiary winding and the result shows that the 3rd harmonic voltage are less than 3%. So if we can accept those small ripple on the transmission line (the 150kV line do not directly supplying any load, and the distribution transformers always have the tertiary winding) we don't need the tertiary winding.
>for the third reason, my mentors say there is a method for detecting the earth fault current without tertiary winding. but i'm forget the method's name. It use the tank as a ground and the earth fault current detector is installed between the tank and earth (the tank is act as a tertiary winding)
please let me know if i have wrong perception.. by the way, is there any weakness of Star-Star Transformers?
and please share the common design for inter bus transformers in your country for my references..