Re: voltage transformer protection

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Anthony Jarmie

Hello there,


The 10VA & 110VA are called steady state ratings. Find out the transient kVA requirement from this transformer. This will be the aggregate of the inrush VA of all the components – that are expected to be simultaneously switched ON – connected to the control transformer secondary winding. Find out transient current from: Transient kVA/Secondary Voltage. Find out the duration of this inrush current. Whatever fuse you select, find out the trip time from the I-t curve of the fuse – for this transient current. You should select such a fuse that the tripping time of the fuse for the transient current should be more than the inrush duration.



Anthony Jarmie