Don't hesitate. Tell us what you like and what we can do better. Share your thoughts and experiences. 

Dear Walter,

I would like to point out that in this history article you are completely missing another principle for field failure protection developed and used by former ASEA (now ABB).

Namely ASEA has successfully used Directional Current principle for such protection from the middle of the sixties. I attach the following pdf document published in 1969 as supporting info (see pages 14-15):

Note that this principle is then used in COMBIFLEX generator protection packages supplied by ASEA and now by ABB. It has a very good track record and if required more info can be provided. It is also used today in many existing installations.

Zoran Gajic, Global Product Manager

ABB AB, Vasteras, Sweden

PAC World: Hello Zoran,

Thanks for the valuable amendment. I know that it might happen to miss certain principles and approaches. I am very interested in every hint and will include it in further publications (as my history of PAC consisting of 3000 references on 300 pages).

One of the next issues will cover the step from single relays to combined devices in generator protection. Here I will mention the COMBIFLEX solution. The RYGIA is one of the first steps. Do you have a picture to be used?

I am also very interested in the next steps up to the REG  at ABB. Please contribute if you want to.

Walter Schossig, PAC World


PAC World:  Below is the solution of the June 2010 Sudoku puzzle.

The Sudoku puzzle in the June 2010 issue triggered the competitive spirit of some of our readers. These are the first seven (in the order that we received them):

Brian Gibson, Alan Guo, Robert Spreng,  Rick Taylor,  Dane Parker, Daniel Aberer, Masha Alaupovic


I am very happy to read the excellent protective relaying magazine. I teach the class "Protective relaying" in Tsinghua University, China  and will be happy to introduce the magazine to all my students.  And of course, I will submit the experience and opinions to the editors.  I also would like to do some volunteer work to push up the growth of the magazine.

Bin Wang, Tsinghua University, China

PAC World: Dear Bin, we will appreciate any contributions that you or your students can make. Please do not hesitate to send us articles, event reports, power and general pictures or tell us about the interesting hobbies of the PAC professional in China.


Hi, I really like PAC World. Thanks for this magazine.

I'd really like to read the whole thing electronically without having to click on separate PDFs - that way I can take it with me and file it for future reference.

Any chance of this in the near future?

Daniel Mulholland

PAC World: Dear Daniel, we will try a PDF version of the magazine in normal PDF quality. It is just a matter of what size this file will be and if it will be convenient to download.

Power. Flexible. Easergy.
BeijingSifang June 2016