A modular current sensing system, comprising: a rigid support structure disposed inside a packaging unit, the rigid support structure defining a hollow center for receiving a current carrying conductor; and a plurality of current detecting units disposed on the rigid support structure such that the plurality of current detecting units are electrically coupled to one another, wherein each of the plurality of current detecting units comprises a flexible circuit having a first side and a second side opposite the first side, the flexible circuit comprising: a plurality of cells defined therein, each of the plurality of cells having a first side and a second side respectively corresponding to the first side and second side of the flexible circuit; a plurality of conductive windings (230, 232, 234, 236) disposed on at least one of the first and second sides of the plurality of cells; a cell boundary separating each of the plurality of cells from adjacent cells of the plurality of cells, wherein the flexible circuit is folded proximate to the cell boundaries in alternating fashion to form a stacked configuration, such that magnetic flux generated by the conductive windings (230, 232, 234, 236) are mutually additive; a stress reduction feature disposed proximate to the cell boundary between each of the plurality of cells; and a sealing element configured to secure the flexible circuit in the stacked configuration, wherein a number of current detecting units in the modular current sensing system is selected based on a level of current flowing through the current carrying conductor. a rigid support structure disposed inside a packaging unit, the rigid support structure defining a hollow center for receiving a current carrying conductor; and a plurality of current detecting units disposed on the rigid support structure such that the plurality of current detecting units are electrically coupled to one another, wherein each of the plurality of current detecting units comprises a flexible circuit having a first side and a second side opposite the first side, the flexible circuit comprising: a plurality of cells defined therein, each of the plurality of cells having a first side and a second side respectively corresponding to the first side and second side of the flexible circuit; a plurality of conductive windings (230, 232, 234, 236) disposed on at least one of the first and second sides of the plurality of cells; a cell boundary separating each of the plurality of cells from adjacent cells of the plurality of cells, wherein the flexible circuit is folded proximate to the cell boundaries in alternating fashion to form a stacked configuration, such that magnetic flux generated by the conductive windings (230, 232, 234, 236) are mutually additive; a stress reduction feature disposed proximate to the cell boundary between each of the plurality of cells; and a sealing element configured to secure the flexible circuit in the stacked configuration, a plurality of cells defined therein, each of the plurality of cells having a first side and a second side respectively corresponding to the first side and second side of the flexible circuit; a plurality of conductive windings (230, 232, 234, 236) disposed on at least one of the first and second sides of the plurality of cells; a cell boundary separating each of the plurality of cells from adjacent cells of the plurality of cells, wherein the flexible circuit is folded proximate to the cell boundaries in alternating fashion to form a stacked configuration, such that magnetic flux generated by the conductive windings (230, 232, 234, 236) are mutually additive; a stress reduction feature disposed proximate to the cell boundary between each of the plurality of cells; and a sealing element configured to secure the flexible circuit in the stacked configuration, wherein a number of current detecting units in the modular current sensing system is selected based on a level of current flowing through the current carrying conductor.