Primary Ohms to Secondary Ohms Conversion

Convert a primary impedance value to a secondary impedance value by :

1. multiply the primary impedance value by the CT ratio.

2. divide this number by the PT ratio.

Secondary Ohms to Primary Ohms Conversion

Convert from secondary to primary by:

1. multiply the secondary impedance value by the PT ratio

2. divide this number by the CT ratio.


Many times the line impedance data might be specified in primary values.

A good relay tech can easily verify or derive the secondary impedance value that will be used to set impedance relays.