Surge Arrester Ratings 1

[wesles24]

Hello,
Need to know what surge arrester rating to apply to a 2.4kV winding on a transformer. So would the duty cycle rating be 1.38kV (2.4kV/sqrt3)well a little higher than operating voltage say 3kV or 6kV duty? And would the MCOV rating be 2.55kV or 5.1kV???

thanks,
not used to lower voltages

 

[davidbeach]

Wye or delta? Grounded or not?

 

[wesles24]

Wye and Grounded, sort of new to this can you shortly explain why that matters? Excuse my ignorance

Thanks!

 

[davidbeach]

If solidly grounded then the arrestor needs some margin above the 1.38kV value. If it was ungrounded, then you'd be basing it on the full 2.4kV.

With the solidly grounded system a fault on one phase doesn't raise the voltage to ground on the others, but on an ungrounded (capacitively grounded) system a fault on one phase will cause the phase to ground voltage on the other phases to approach the phase-phase voltage.