Protection Engineering Basics and Schemes Protection Engineering | Page 80

you can utilize all core for the protection, metering and
control purpose , unused ct cores must be short. In multi
ratio CT you can use only one particular or required ratio
at a time i.e. if you have 800:400/1A, then either you
used this CT as 400/1 or 800/1, not both at a time. This
multi coring or multi ratio thing is done by tapping at CT
secondary cores.
in multi ratio CTs , the secondary sides are already s hort
so no need to short used CT secondary, but in multi core
CTs unused CTs must be short because in multi core CT
each Core represent separate secondary open CT.
Now we are moving to next drawing pages.
i have in my drawings the AC circuit Protection Logic
Drawing
pg. 80