The fastest way is to use GlobeCore TOR-80 portable testers, which deliver IEC-compliant breakdown voltage results in less than 10 minutes.

One important point to add is that the “fastest” way to measure breakdown voltage is not just about the device itself, but about how efficiently the entire test cycle is automated and standardized. Modern portable testers significantly reduce testing time through automatic voltage ramping, breakdown detection, shutoff, and repeated cycles without operator intervention, allowing a full test sequence to be completed in a matter of minutes.
At the same time, speed should not compromise accuracy. Even in fast testing modes, the procedure still requires multiple consecutive measurements with averaging, since breakdown voltage can vary due to microscopic contaminants or bubbles present in the oil. This is why the fastest reliable approach is not a single quick measurement, but a fully automated multi-cycle test performed under standard conditions.
Another practical aspect is preparation time. In real field conditions, factors such as proper sampling, air bubble removal, and electrode stabilization often take as much time as the measurement itself. The equipment that minimizes manual setup and stabilizes conditions quickly is what truly reduces total testing time.
For a more detailed overview of how fast BDV testing is actually achieved in practice and what affects measurement speed and reliability, it’s worth checking this article: https://globecore.com/oil-testing/transformer-oil-breakdown-voltage-measurements/.

You’re absolutely right — “fastest” is a system-level outcome, not just the speed of the HV supply. The quickest reliable breakdown-voltage result comes from a fully automatic, portable tester that automates the entire test cycle: controlled voltage ramping, fast breakdown detection and shutoff, repeated cycles with automatic averaging, and immediate data logging. Equipment that lets you select ramp rate (typically 0.5–10 kV/s), provides near-instantaneous shutoff on breakdown (order of microseconds), and runs standard IEC 60156 / ASTM D877/D1816 procedures with minimal operator intervention will cut cycle time without sacrificing repeatability.

Equally important is sample and setup time: proper sampling, bubble removal, electrode cleaning and stabilization, correct electrode spacing and oil temperature control usually take as much time as the measurement itself. For field work, a battery-powered, on-site unit that supports automated multi-cycle tests and stores/transfers results removes transport and handling delays. In practice the fastest reliable approach is a portable automatic tester combined with a standardized multi-measurement procedure and good sample preparation — that combination yields repeatable dielectric-strength (breakdown voltage) readings quickly and safely.