If the insulating liquid is used in equipment that requires the application of vacuum and filtering of the oil before being placed into service, Test Method D877 is not recommended. Test Method D1816 should be used to determine the breakdown voltage of filtered and degassed liquids.
Test Method D877 describes two procedures, A and B, for determining electrical breakdown of specimens. Procedure A is used to determine the breakdown voltage of liquids in which any insoluble breakdown products easily settle during the interval between the required repeated breakdown tests. These liquids will include petroleum oils, hydrocarbons, and askarels (PCB) used as insulating and cooling liquids in transformers, cables, and similar apparatus.
Procedure B of Test Method D877 should be applied for liquid samples containing insoluble materials that settle from the specimen during testing. These may include samples taken from circuit breakers, load tap changers, and other liquids heavily contaminated with insoluble particulate material.
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