Electrical tree test method, electrode structure, and electrode setting assembly

An electrode structure for use in an electrical tree test method for testing electrical trees in an insulating member including a mica insulation applied to an electrical conductor, the structure comprising:

• a plate-like substrate which has electrical conductivity, and has a flat first surface and a flat second surface at the back of and parallel to the first surface;
• and
• a plurality of needle electrodes, which have electrical conductivity, are disposed on the first surface of the substrate, extend perpendicularly to the first surface of the substrate, and are disposed with intervals therebetween,
• wherein
• the needle electrodes include:
• a first needle electrode arranged on the first surface of the substrate, substantially at the center of the first surface;
• and
• second needle electrodes arranged at the same distance from the first needle electrode with circumferential intervals therebetween around the first needle electrode.

An electrode setting assembly for setting conditions of reproducing electrical trees, comprising:

• an electrode structure;
• a first electrode spacer shaped like a plate, having a flat first surface and a flat second surface parallel to and back of the flat first surface of the first electrode spacer, and having a thickness equal to that of the substrate, the thickness between the first and second surfaces of the first electrode spacer being substantially equal to that of the substrate;
• a second electrode spacer shaped like a plate, having a flat first surface and a flat second surface parallel to and back of the flat first surface of the second electrode spacer, and having a thickness equal to that of the substrate, the thickness between the first and second surfaces of the second electrode spacer being substantially equal to that of the substrate;
• and
• a holding plate having a first surface formed in a plane,
• wherein
• the electrode structure includes
• a plate-like substrate which has electrical conductivity, and has a flat first surface and a flat second surface at the back of and parallel to the first surface;
• and
• a plurality of needle electrodes, which have electrical conductivity, are disposed on the first surface of the substrate, extend perpendicularly to the first surface of the substrate, and are disposed with intervals therebetween,
• the second surface of the substrate of the electrode structure, the second surface of the first electrode spacer and the second surface of the second electrode spacer contact the first surface of the holding plate;
• and
• the first electrode spacer and the second electrode spacer are located oppose to each other in a planer direction sandwiching the substrate of the electrode structure therebetween.