A method and apparatuses for handling delayed zero crossing in fault current through a circuit breaker (110) are disclosed. An interface arrangement (100) is configured to couple an alternating current, AC, power system (102) with a direct current, DC, power system (103), or vice versa. The interface arrangement (100) comprises at least one converter (104, 105, 108) for conversion of AC power to DC power, or vice versa, which comprises a DC side for coupling of the converter (104, 105, 108) to the DC power system (103) and an AC side for coupling of the converter (104, 105, 108) to the AC power system (102). A circuit breaker (110) is arranged in a current path between the AC side of the at least one converter (104, 105, 108) and the AC power system (102). There may be a risk of delayed zero crossing in fault current occurring in case a fault occurs in a predefined portion of the interface arrangement (100). If a fault is sensed to occur in the interface arrangement (100) within the predefined portion of the interface arrangement (110), opening of contacts of the circuit breaker (110) can be delayed by a selected delay time period, compared to if the fault would have been within a portion of the interface arrangement (100) different from the predefined portion.