50Hz frequency difference is shown under synchronous conditions with the circuit breaker closed

The synchro check, synchro switch function needs a definition about the voltages to be compared. This definition is given by the parameter Voltage Select.

On the other hand, the relay uses a pre-defined frequency source for the frequency dependent protection functions. This definition is invisible for the EuroCAP master user and may be different from the Voltage Select parameter.

This means, that not only the synchrocheck function shall receive its analogue voltage inputs but also the voltage input used for frequency source of various protection functions shall be wired. 

In most cases, the protection functions are assigned to L1-N, so this input shall always be wired to the corresponding VT in order to avoid any malfunction. If the L1-N input and all inputs for the synchrocheck are wired and the indicated frequency difference is still 50Hz, please contact Protecta Support team.