A waveform separator system for determining Direct Current, DC, leakage current flowing through an insulating structure in a high voltage direct current power system wherein the DC leakage current is a composite DC current comprising one or more momentary spikes, and having a DC component and an Alternating Current, AC, component, the system comprising: a waveform separator configured to receive the composite DC current flowing through the insulating structure and to separate the composite DC current into corresponding DC and AC components wherein the AC component has a first rate of change, and wherein the DC component has a second rate of change, and wherein the first rate of change is greater than the second rate of change; an amplifier configured for amplifying the AC component and the DC com ponent; a comparator configured to receive the AC component, wherein the AC component comprises one or more positive components and one or more negative components characterised in that the comparator includes a positive voltage comparator configured for counting the one or more positive components and a negative voltage comparator configured for counting the one or more negative components, the comparator being further configured for producing a positive digital signal corresponding to the counted one or more positive components and a negative digital signal corresponding to the counted one or more negative components; and a processor configured to: (a) receive the positive digital signal and the negative digital signal and the DC component, (b) analyze the positive digital signal and the negative digital signal and the DC component, and (c) determine a resultant leakage current flowing through the insulating structure. a waveform separator configured to receive the composite DC current flowing through the insulating structure and to separate the composite DC current into corresponding DC and AC components wherein the AC component has a first rate of change, and wherein the DC component has a second rate of change, and wherein the first rate of change is greater than the second rate of change; an amplifier configured for amplifying the AC component and the DC com ponent; a comparator configured to receive the AC component, wherein the AC component comprises one or more positive components and one or more negative components characterised in that the comparator includes a positive voltage comparator configured for counting the one or more positive components and a negative voltage comparator configured for counting the one or more negative components, the comparator being further configured for producing a positive digital signal corresponding to the counted one or more positive components and a negative digital signal corresponding to the counted one or more negative components; and a processor configured to: (a) receive the positive digital signal and the negative digital signal and the DC component, (b) analyze the positive digital signal and the negative digital signal and the DC component, and (c) determine a resultant leakage current flowing through the insulating structure. (a) receive the positive digital signal and the negative digital signal and the DC component, (b) analyze the positive digital signal and the negative digital signal and the DC component, and (c) determine a resultant leakage current flowing through the insulating structure.