Electrical insulating oil composition

Abstract

An electrical insulating oil having a flash point (PMCC) of 130° C. or more and a pour point of −40° C. or lower, comprising hydrorefined mineral oil and/or synthetic hydrocarbon oil and in the range of from 0.5 to 10 wt. % of bright stock oil, based on the total weight of the electrical insulating oil composition.

1 . An electrical insulating oil having a flash point (PMCC) of 130° C. or more and a pour point of −40° C. or lower, comprising: 
 an oil selected from the group consisting of hydrorefined mineral oils and synthetic hydrocarbon oils; and    bright stock oil present in the range of from 0.5 to 10 wt. %, based on the total weight of the electrical insulating oil composition.    
   
   
       2 . The electrical insulating oil according to  claim 1  wherein the bright stock oil has a total sulphur content in the range of from 0.4 to 2.0 wt. %, a total nitrogen content in the range of from 100 to 500 wt. ppm, and a basic nitrogen content of 300 wt. ppm or less.  
   
   
       3 . The electrical insulating oil composition according to  claim 1 , wherein said composition has a pour point of −45° C. or lower.  
   
   
       4 . The electrical insulating oil composition according to  claim 1 , wherein said composition has a flash point (PMCC) of 135° C. or more.  
   
   
       5 . The electrical insulating oil composition according to  claim 1 , wherein said composition comprises in the range of from 0.01 to 0.4 wt. % of phenolic antioxidant, based on the total weight of the electrical insulating oil composition.  
   
   
       6 . The electrical insulating oil composition according to  claim 1 , wherein said composition comprises in the range of from 0.01 to 0.08 wt. % of phenolic antioxidant, based on the total weight of the electrical insulating oil composition.  
   
   
       7 . The electrical insulating oil composition according to  claim 1 , wherein said composition comprises in the range of from 0.08 to 0.4 wt. % of phenolic antioxidant, based on the total weight of the electrical insulating oil composition.  
   
   
       8 . The electrical insulating oil composition according to  claim 1 , wherein the hydrorefined mineral oil has a kinematic viscosity in the range of from 8.0 to 24 mm 2 /s at 40° C. and is selected from the group consisting of hydrorefined naphthenic mineral oils and API base oil classification Group II or Group III hydrorefined paraffinic mineral oils.  
   
   
       9 . The electrical insulating oil composition according to  claim 1 , wherein the synthetic hydrocarbon oil has a kinematic viscosity in the range of from 8.0 to 24 mm 2 /s at 40° C. and is selected from the group consisting of isoparaffinic synthetic oils, GTL synthetic oils, poly-α-olefins (PAOs) belonging to API base oil classification Group IV, and a mixtures thereof.  
   
   
       10 . The electrical insulating oil composition according to  claim 1 , wherein the bright stock oil is a heavy mineral oil base oil fraction obtained by reduced pressure distillation of the residual paraffinic mineral oil from atmospheric distillation of crude oil, and deasphalting, solvent extraction and solvent dewaxing treatment of the residual oil obtained from said reduced pressure distillation.  
   
   
       11 . The electrical insulating oil composition according to  claim 1 , which composition conforms to at least one of the following Standards: IEC (International Electrotechnical Commission) Standard 296 (Class II), IEC Standard 60296 (Type U), IEC Standard 60296 (Type I) and IEC Standard 60296 (Type T).  
   
   
       12 . The electrical insulating oil according to  claim 1  wherein the bright stock oil is a base oil belonging to API base oil classification Group I.  
   
   
       13 . The electrical insulating oil according to  claim 11  wherein the bright stock oil has a total sulphur content in the range of from 0.4 to 2.0 wt. %, mercaptan sulphur content of 100 wt. ppm or less, and sulphide-type sulphur content of 0.5 wt. % or less.  
   
   
       14 . The electrical insulating oil according to  claim 1  wherein the bright stock oil is a base oil has a total nitrogen content in the range of from 100 to 500 wt. ppm, and basic nitrogen content of 300 wt. ppm or less.  
   
   
       15 . The electrical insulating oil according to  claim 1  wherein the bright stock oil is a base oil has a total content of polar components (IP368) in the range of from 30 to 70 wt. %.