A bipolar DC power transmission scheme comprising: first and second DC poles, each DC pole including a respective power DC transmission medium (40,42) extending between two ends; a plurality of first converters and a plurality of second converters, wherein each end of the DC power transmission medium of the first DC pole is respectively operatively connected to at least one of the plurality of first converters, and each end of the DC power transmission medium of the second DC pole is respectively operatively connected to at least one of the plurality of second converters; wherein each converter (32,34) includes a first DC terminal and a second DC terminal; a controller programmed to block one or more of the plurality of first and second converters (32,34) in response to a fault occurring on either of the first and second DC poles; and a monitoring device configured to identify the faulty one of the first and second DC poles on which the fault has occurred, wherein the controller is further programmed to deblock the or each blocked converter (32,34) connected to the healthy other of the first and second DC poles after the monitoring device has identified the faulty one of the first and second DC poles on which the fault has occurred; wherein the bipolar DC power transmission scheme includes a current return path, wherein said current return path operatively connects the second DC terminal of the one of the plurality of first and second converters (32,34) to the second DC terminals of the others of the plurality of the first and second converters (32,34); and wherein the monitoring device is configured to identify the faulty one of the first and second DC poles on which the fault has occurred by monitoring the direction of current in the current return path. first and second DC poles, each DC pole including a respective power DC transmission medium (40,42) extending between two ends; a plurality of first converters and a plurality of second converters, wherein each end of the DC power transmission medium of the first DC pole is respectively operatively connected to at least one of the plurality of first converters, and each end of the DC power transmission medium of the second DC pole is respectively operatively connected to at least one of the plurality of second converters; wherein each converter (32,34) includes a first DC terminal and a second DC terminal; a controller programmed to block one or more of the plurality of first and second converters (32,34) in response to a fault occurring on either of the first and second DC poles; and a monitoring device configured to identify the faulty one of the first and second DC poles on which the fault has occurred, wherein the controller is further programmed to deblock the or each blocked converter (32,34) connected to the healthy other of the first and second DC poles after the monitoring device has identified the faulty one of the first and second DC poles on which the fault has occurred; wherein the bipolar DC power transmission scheme includes a current return path, wherein said current return path operatively connects the second DC terminal of the one of the plurality of first and second converters (32,34) to the second DC terminals of the others of the plurality of the first and second converters (32,34); and wherein the monitoring device is configured to identify the faulty one of the first and second DC poles on which the fault has occurred by monitoring the direction of current in the current return path.