In order to set the amplitude matching for the protected object, a reference power - identical for all windings - needs to be defined. For two-winding arrangements, the nominal power will usually be the reference power. The individual reference currents for each winding of the protected object are then calculated by the P632 on the basis of the set reference power and the set primary nominal voltages of the transformer.

: reference power

, : reference current of winding a or b, respectively

, : nominal voltage of winding a or b, respectively

The P632 calculates the matching factors on the basis of the reference currents and the set primary nominal currents of the system transformers.

with

, : amplitude matching factor of end a or b, respectively

, : primary nominal currents of the system transformers

Reference currents and matching factors are displayed at the P632.

The P632 checks that the reference currents and matching factors are within their permissible ranges. The matching factors must satisfy the following conditions:

Should the P632 calculate reference currents or matching factors not satisfying the above conditions then an alarm will be issued and the P632 will be blocked automatically.

The measured values of the phase currents of the windings of the protected object are multiplied by the relevant matching factors and are then available for further processing. Consequently, all threshold values and measured values always refer back to the relevant reference currents rather than to the transformer nominal currents or the nominal currents of the device.