Video: DIELECTROTEST – Product

Video transcript

The instrument that tells you whether transformer oil is still able to insulate, and that does it to the standard rather than to a habit. The oil inside a transformer is not there only to cool it. It is the insulation. And insulation gets tired: water and particles find their way in, and the oil stops holding back the voltage. The test itself is simple to picture. Two electrodes sit two and a half millimetres apart, under the oil. The voltage between them is raised slowly until a spark jumps across.

The voltage at that instant is the breakdown voltage. The Dielectrotest does that on its own. You prepare the sample, press start, and the instrument runs the whole sequence, breakdown after breakdown, and gives you the result. This is the part that matters when the result has to stand up. It is a standards instrument: it complies with UNE, EN 50160, and it carries the test methods themselves in the menu, each one with its own electrodes,

gap, ramp rate and number of breakdowns already set. And it is not one standard but a shelf of them. Every method the instrument carries is listed here, alongside the safety and electromagnetic compatibility standards the instrument itself is built to. One spark proves very little. Breakdown is a statistical event, so the standards ask for several in a row, and what matters is the average and how much the values scatter. When the series finishes, the result is on the screen and on paper.

The last 20 reports stay in the instrument, and everything can go to a computer. And it protects both the sample and the operator. The high voltage is cut in under a millisecond, so the spark does not burn the oil, and the lid is interlocked: no lid, no test. Three versions, and the only real difference is how far the voltage can go. Insulating oil testing, from Amperis.