An interface arrangement configured to couple an alternating current, AC, power system with a direct current, DC, power system, the interface arrangement lacking additional auxiliary equipment and comprising: at least one converter (104, 105, 108; 140) for conversion of AC power to DC power, wherein the at least one converter comprises a DC side for coupling of the converter to the DC power system and an AC side for coupling of the converter to the AC power system; a transformer comprising a primary side for coupling of the transformer to the AC power system and a secondary side for coupling of the transformer to the at least one converter; a circuit breaker arranged in a current path between the transformer and the AC power system, the current path comprising a multi-phase current path comprising a plurality of conductors for coupling the AC power system with the DC power system and the circuit breaker being configured to controllably effect discontinuation of flow of current in each of the plurality of conductors of the current path upon opening of contacts of the circuit breaker independently of the other ones of the plurality of conductors; a fault sensing unit configured to sense a fault occurring in the interface arrangement; and a control and processing module communicatively coupled to the fault sensing unit; the control and processing module being configured to control operation of the circuit breaker at least with respect to opening of the circuit breaker, wherein the control and processing module is configured to open the contacts of the circuit breaker if there is determined to be a fault occurring in the interface arrangement; and characterized in the control and processing module being further configured to, if a fault in the interface arrangement as sensed by the fault sensing unit occurs in a current path in a predefined portion of the interface arrangement for a conductor of the plurality of conductors, delay opening of the contacts of the circuit breaker by a selected delay time period for the conductor for which a fault is sensed so as to effect discontinuation of flow of current in the conductor by a selected delay time period compared to if the fault would have been within a portion of the interface arrangement different from the predefined portion and without delay for the other conductors, wherein the fault in the interface arrangement as sensed by the fault sensing unit is a phase to ground fault and the selected delay time period is between about 20 ms and 100 ms and the delay is implemented through the control and processing module being configured to send an instruction issued after the detection of the fault that is delayed by the selected delay time period and the predefined portion of the interface arrangement is a current path between the secondary side of the transformer and the AC side of the at least one converter. at least one converter (104, 105, 108; 140) for conversion of AC power to DC power, wherein the at least one converter comprises a DC side for coupling of the converter to the DC power system and an AC side for coupling of the converter to the AC power system; a transformer comprising a primary side for coupling of the transformer to the AC power system and a secondary side for coupling of the transformer to the at least one converter; a circuit breaker arranged in a current path between the transformer and the AC power system, the current path comprising a multi-phase current path comprising a plurality of conductors for coupling the AC power system with the DC power system and the circuit breaker being configured to controllably effect discontinuation of flow of current in each of the plurality of conductors of the current path upon opening of contacts of the circuit breaker independently of the other ones of the plurality of conductors; a fault sensing unit configured to sense a fault occurring in the interface arrangement; and a control and processing module communicatively coupled to the fault sensing unit; the control and processing module being configured to control operation of the circuit breaker at least with respect to opening of the circuit breaker, wherein the control and processing module is configured to open the contacts of the circuit breaker if there is determined to be a fault occurring in the interface arrangement; and characterized in the control and processing module being further configured to, if a fault in the interface arrangement as sensed by the fault sensing unit occurs in a current path in a predefined portion of the interface arrangement for a conductor of the plurality of conductors, delay opening of the contacts of the circuit breaker by a selected delay time period for the conductor for which a fault is sensed so as to effect discontinuation of flow of current in the conductor by a selected delay time period compared to if the fault would have been within a portion of the interface arrangement different from the predefined portion and without delay for the other conductors, wherein the fault in the interface arrangement as sensed by the fault sensing unit is a phase to ground fault and the selected delay time period is between about 20 ms and 100 ms and the delay is implemented through the control and processing module being configured to send an instruction issued after the detection of the fault that is delayed by the selected delay time period and the predefined portion of the interface arrangement is a current path between the secondary side of the transformer and the AC side of the at least one converter.