For amplitude matching, the nominal power of the transformer end should first be set as the reference power. The reference current is then calculated by the P632 on the basis of the set reference power and the set primary nominal voltage of the transformer end.

: reference power

: reference current of the ground differential protection function, end a

: nominal voltage, end a

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

with

am: amplitude-matched

: primary nominal current of the main current transformer

: primary nominal current of current transformer in the neutral-point-to-ground connection

Reference currents and matching factors are displayed at the P632.

The P632 checks that the reference current and matching factor are within their permissible ranges. The acceptable range for the reference current can be read out from the operating program. The following applies to the matching factors:

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

The measured values 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 current rather than to the transformer nominal current or the nominal current of the device.