Dielectric Strength: (D877 & D1816)

Dielectric breakdown voltage of insulating oil is a measure of its ability to withstand voltage stress without failure. It is the voltage at which breakdown occurs between two similar electrodes under defined test conditions. The test serves primarily as an indicator of the presence of electrical conductive contaminants in the oil, such as water, dirt, moist cellulosic fibers and particulate matter.

Two methods are used for measuring the dielectric breakdown voltage of insulating oils, as follows:

a) ASTM D877 is generally recommended for routine acceptance of new, unprocessed oil from a supplier for use in circuit breakers. The test method uses thin flat-faced parallel cylindrical electrodes with a 2.5 mm gap. This method is not as sensitive to the general population of contaminates present in a liquid sample and is less sensitive than that of D1816 particularly with reference to water content and cellulosic fibers.

b) ASTM D18l6 is the recommended test for fluid that is being processed into transformers or contained in transformers and load tap changers. The method uses spherically shaped electrodes rather than flat disc or cylindrical-shaped as in D877. The fluid sample is circulated continuously in the test cell throughout the test by mechanical means. The gap distance standard settings are 1 mm and 2 mm with the 1 mm being used by our laboratory.

We current support both TOA 3.3c and TOA4 Online version, which is an Internet web-based software. Both versions interpret dissolved gas and insulating fluid test data for power transformers and other liquid-filled electrical apparatus such as load tap changers, regulators and oil circuit breakers.It provides a variety of reports and graphs to support basic testing, condition assessment and maintenance tasks. Automatic dissolved gas analysis and fluid quality analysis employ up-to-date methods which have been mathematically enhanced to account for measurement "noise" often found in DGA data. Trends and rate of changes are also provided for in this analysis. TOA$ reports may be accessed on the internet once a client account has been set up and information stored to this on-line storage file.