This document discusses high voltage transformers and the various types of tests performed on transformers. It describes partial discharge testing, insulation resistance testing, and routine testing. Partial discharge testing detects localized breakdowns in insulation under high voltage stress. Insulation resistance testing measures insulation quality. Routine testing confirms operational performance and checks for manufacturing defects. The document outlines advantages like safety, efficiency, and failure detection, and disadvantages like insufficient oil level and overloading.