Can I verify my BDV test set performance by comparing the results from two test sets on the same sample of oil?
Yes, but you must consider these potential issues:
(1) Even if you can transfer the oil sample from one test set to another in the same test vessel you may not get exactly the same test results. This is because by-products produced by the breakdown arcs from the first set of tests are now somewhere in the oil sample and likely to effect any subsequent tests.
(2) Changes in oil sample temperature will produce changes in test results.
(3) Pouring oil from one vessel to another vessel is likely to produce bubbles that will introduce additional air and moisture to the sample resulting in lower test results than the previous testing
(4) If the time between comparative tests on the same oil sample is excessive it will absorb moisture from the air, even if a test vessel has a lid as it is not sealed in the same manner as an oil sample bottle.
(5) Two oil samples taken from the same drum are in effect two different samples of oil. They can, if particle contamination is present, exhibit different levels of breakdown voltage.
(6) Oil with unknown contamination can cause large changes in test results, particles or moisture can circulate in the oil between the electrodes, causing variation in test results. This can easily lead to an incorrect conclusion with regard to the performance of the test sets being compared. That is why five or six breakdown tests are performed during each test sequence to take into account this variation
(7) Cleanliness is extremely important to ensure reliable test results that can be reliably compared.
