How does an oil furnace transformer tester work in relation to transformer oil in power transformers?

An oil furnace transformer tester works by applying a high voltage to the transformer oil in power transformers to assess its dielectric strength and insulation properties. The tester measures the breakdown voltage of the oil, which indicates its ability to withstand electrical stress without failing. This testing is crucial for ensuring the reliability and safety of power transformers, as degraded transformer oil can lead to insulation failure and operational issues.