This test method describes the procedures for determining the oxidation induction time (OIT) of natural ester insulating fluids using either of two different test conditions and each with a different DSC testing cell. Method A utilizes a pressure DSC cell with a static pressure of air at 3.5 MPa (500 psig) and a programmed test temperature sequence that includes an isothermal portion at 140C followed by a ramp at 10C/minute. Method B utilizes a regular DSC with a dynamic flow of air at 50cc/min and a programmed test temperature sequence that includes an isothermal portion at 130C followed by a ramp at 10C/minute. This test method is applicable to natural ester fluids used as dielectric coolants in electrical equipment, such as transformers. This test method is applicable for the evaluation of the oxidation stability of natural ester fluids for quality control, quality assurance or research and development purposes.
Fluid and equipment manufacturers, specifiers, end-users, and testing labs have no standard method for measuring the oxidation stability of natural ester dielectric fluids for use in electrical equipment. Only one method has been proposed based on an IEC standard 61125 method C, but this method is very time consuming and cumbersome. Laboratory time can be cut from 2-3 weeks to 2-3 hours.
Pressure Differential Scanning Calorimeter; natural ester; electrical insulating fluid; oxidation induction time; OIT; PDSC; DSC; thermal analysis
The title and scope are in draft form and are under development within this ASTM Committee.
Citing ASTM Standards
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