Methods and apparatus are provided for a high voltage capacitor having a plurality of capacitor units connected in electrical series in a stacked configuration. An insulator element can be positioned between two adjacent capacitor units of the high voltage capacitor for providing separation between the adjacent capacitor units, where the insulator element has a first thickness at a first end of the insulator element and a second smaller thickness at a second end of the insulator element. The insulator element can have a wedge-shaped cross section.