IEC 63012-2019 pdf free.Insulating liquids – Unused modified or blended esters for electrotechnical applications.
4.2Fire performance classification
The insulating liquids are classified for fire performance according to lEC 61039.4.3Viscosity classification
Viscosity influences heat transfer and therefore the temperature rise of the equipment. Thelower the viscosity, the easier the liquid circulates leading to improved heat transfer.
Viscosity of natural esters and some synthetic esters is usually higher than that of mineral oil.This requires special considerations at the equipment design stage and may affectperformance of equipment at low temperatures, too. Adjustment of modified or blended estercomposition allows for tailoring the viscosity and other properties to fit the equipment designrequirements.
Based on the viscosity,the liquids are classified as in Table 1.The category V1 refers toesters of low viscosity,similar to mineral oils. The category V2 refers to esters of higherviscosity than V1, but still lower than typical synthetic or natural esters. The category V3refers to modified or blended esters that do not show low viscosity characteristics.
NOTEAt the stage of development of this document, there are no commercial modified or blended esters withviscosity category V3.This category makes provision for future technical developments.
5 Properties, significance and test methods
5.1 Physical properties
A visual inspection of unused modified or blended esters (with light transmitted throughapproximately 10 cm thickness of the liquid at ambient temperature) shall not indicate thepresence of visible contaminants, free water or suspended matter.
lf required,colour shall be measured according to lSO 2211 (Hazen scale) or ISo 2049(ASTM scale).
Kinematic viscosity shall be measured according to lS0 3104 and reported at 40 °C.The usercan request viscosity values in the range of temperatures 0 °C to 100°C (with at least threepoints: o°C,40°C and 100°c).
NOTE Another suitable method for viscosity measurement is given in ASTM D7042.
lt is beneficial to have the value of viscosity at temperatures below 0 °C to understand thebehaviour of the liquid in temperatures near the pour point, for example at -20 °C.
NOTE Viscosity at very low temperatures can be measured according to lEC 61868.
At low temperatures, the resulting higher viscosity of liquid is a critical factor for the cold startof transformers with natural liquid circulation (no forced circulation and therefore possibleoverheating at the hot spots) and negatively influences the speed of moving parts, such as inpower circuit breakers,switchgear,on-load tap changer mechanisms, pumps and regulators.Lowest cold start energizing temperature (LCSET) requirements should be agreed uponbetween supplier and purchaser.
lf liquid is to be used in equipment with moving parts, for example switching equipment,tapchangers, the lubricity shall be measured.The test method shall be that given in ASTM D4172or DlN 51350 (parts 1 through 3). In the case of ASTM D4172,the test parameters shall be:load 392 N, rotation speed 1 200 r/min temperature 75 °C, duration 60 min.IEC 63012 pdf download.