Transformer Protection - 'According to Impedance'

It is mainly for short circuit protection(other incidental advantages may be available at times).SC protection with inst.o/c element is set generally a little above through fault current.As such fault coverage is variable depending up on source impedance.For some systems it may become critical and in extreme cases there is a risk of fault remaining undetected by the inst. element. With the distance protection , in principle,this anomaly is eliminated since it can be set to have definite reach irrespective of source impedance.The main dis advantage is the measurement is complex and voltage dependent.Hence usually numerical o/c relay is specially configured for adequate coverage in all conditions.We usually give numerical relay oc protection and back it up by a distance relay when essential. Like any protection topic this will also require specific check in each instance.

hi Jans,

i need a few sample auto transformer projects,

if you have that can u send me as .pdf

thanks...

@Guest

I do not have anything ready made.If you could please furnish specific requirements i will try to prepare a sample scheme and try to forward .Generally auto transformers are huge

+50 mva and as such must be treated in detail to avoid any expensive error.

Hai Mr. Jans is absolutly correct.

Further more information see below links.

http://wwhttp://www.gedigitalenergy.com/multilin/notes/artsci/art11.pdf

www.ceerelays.co.uk/brochures/CEE%20PRAG.pdf

Hanu