A question about this distance relay model MATLAB/Sumlink

[shingue]

Hello, Guys.

So, I've been looking into modeling and understanding the distance protection.
I checked many articals and stuff.
AND lately I decided to apply and test this distance relay model..

https://scholarworks.wmich.edu/masters_theses/589

I got the most of the parts, excpet the part of SLG model

I couldn't understand the R(K) and the I(K) over there.