earthing system

[hasanhadi]

hi
how calculated rated power for
1- zagzag transformer with 10sec,30sec,1min,10min
2- NGR with 10sec,30sec,1min,10min
3- reactance with 10sec,30sec,1min,10min
4-star-delta closed with 10sec,30sec,1min,10min
i need equation for calculated
this informaton is very importment
please and thanks

 

[7anoter4]

See:
IEEE 32/1972 "Neutral Grounding Devices”
or:
Westinghouse "Electrical Transmission and Distribution Reference Book" published in 1964
ch.XI Grounding Transformers
But the maximum time rating is only 5 min.
Srated=Urated*K3*Irated
K3 from table 12 for time rated from 10 sec up to 5 min.
For NGR see [for instance]:

http://www.postglover.com/Literature/NG112-06_Tech_Info.pdf

http://www.postglover.com/neutralground.html

or Google "Neutral Grounding Devices"

 

[hasanhadi]

hi
how calculated rated for time
example if NGR=38 OHM for 10 sec but i need calculated for value NGR if time 1min or 10 min

also if rated for transformer 100kvA FOR 10 SEC WHAT RATED for 1 min
i need how calculated or i need equation

 

[davidbeach]

You pretty much have to contact the manufacturer. A lot depends on when thermal equilibrium occurs, and that is strictly a function of the enclosure design.