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Dry type transformer for rectifiers

Dry type transformer for rectifiers

Dry type transformer for rectifiers

(OP)
Hi

I'm working for engineering services.
I just started a new project,
and my main duty is to set relay setting values applied on the primary side of dry type transformer. The load only consists of rectifiers which for motor vfd starting.
My main question is which value is recommended or common for 51 pickup.
I have tried to search and read some IEEE Standards, can't decide yet so I need your advice. IEEE standard says 50 pickup can be chosen as 140% of the secondary fault current. But there wasn't recommendation for 51 pickup and just 'can be set lower due to harmonic load currents'. As I know, 51 pickup on the primary side of transformer is commonly set in a range of 125 to 150%. If I choose 150% for the 51 pickup, there will be an any problem?
Waiting for kind advices, Thank you.

RE: Dry type transformer for rectifiers

You should be coordinating your relay settings with the transformer damage curves. See Link.

xnuke
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