1. Scope 1.1 This test method covers a referee and a routine procedure for determining the dielectric breakdown voltage of insulating liquids. These procedures are applicable to liquid petroleum oils, hydrocarbons, and askarels commonly used as insulating and cooling mediums in cables, transformers, oil circuit breakers, and similar apparatus. The referee procedure, with modifications, is suitable for testing silicone fluids (see Test Methods D2225). The referee procedure is also suitable for testing alkylbenzenes. The suitability of either the referee or the routine procedure for testing liquids having viscosities exceeding 900 cSt (mm /s) (5000 SUS) at 40°C (104°F) has not been determined. 1.2 This test method is recommended for acceptance tests on unprocessed insulating liquids received from vendors in tank cars, tank trucks, and drums. It may also be used for the routine testing of liquids from power systems apparatus rated 230 kV and below. 1.3 This test method is not recommended for testing filtered, degassed, and dehydrated oil prior to and during the filling of power systems apparatus rated above 230 kV, or for testing samples of such oil from apparatus after filling. Test Method D1816 is more suitable for, and is recommended for, testing such oils. 1.4 Both the SI and inch-pound units are equally acceptable. 1.5 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.