Complex sentence: Broken-down transformers, high-voltage cables, bushings and other equipment can usefully be investigated in this manner; the insulation is unrolled (in the case of paper insulation) or sliced in thin slices (in the case of solid insulating materials).
Split into simpler sentences: Broken-down transformers, high-voltage cables, bushings and other equipment can usefully be investigated in this manner. The insulation is unrolled (in the case of paper insulation) or sliced in thin slices (in the case of solid insulating materials).