JPS6015089B2 - electrical insulation oil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in electrical insulating oils used in oil-filled electrical equipment such as oil-filled transformers and power cables.

Recently, there has been a demand for downsizing and flame retardancy in oil-filled electrical equipment, and silicone oil has come to be used instead of conventional mineral oil or PCB (polychlorinated biphenyls).
However, silicone oils have the disadvantage of producing gas when exposed to an electric field. If a gas exists in an insulator under an electric field, ion discharge is likely to occur inside the gas, and this ion discharge can cause breakdown of the insulator.
Oils that have a tendency to generate gas under electric fields are not preferred as electrical insulating oils, so they must be gas-absorbing. In addition, when silicone oil deteriorates due to heat, it becomes a low-molecular cyclic siloxane [(CH3)bui○]n (n=3, 4,
5) is generated, which lowers the flash point. Therefore, it has been desired to improve gas absorption and heat resistance under an electric field. Taking these circumstances into consideration, the present invention has been developed to provide a novel electrical technology that has improved gas absorption and heat resistance under an electric field without impairing the flame retardancy and excellent dielectric properties inherent to silicone oil. The purpose is to supply insulating oil.

The gist of the present invention is to provide zero orthophosphoric acid esters having one or more aromatic rings in the molecule and/or phosphite esters having one or more aromatic rings in the molecule to silicone oil.
．． No 05, 5% by weight added to electrical insulating oil.

Orthophosphate esters according to the present invention include tricresyl phosphate, tricylenyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, triphenyl phosphate, phenyl cresyl phosphate, tris phosphate, etc. The phosphite esters are trisnonyl phenyl phosphite, diphenyl isodecyl phosphite, triphenyl phosphite, tricresyl phosphite, phenyl diisooctyl phosphite, phenyl diisodecyl phosphite, diphenyl Examples include isoalkyl phosphite, diphenyl alkyl phosphite, diphenyl phosphite, diphenylphenyl phosphite, /nylphenyl tridecyl phosphite, /nylphenyl phosphite.

The amount of phosphoric acid ester added in the present invention is within the range of 0.05% to 5% by weight based on the silicone oil.

If the content is outside this range, for example 0.05% by weight, there will be no significant effect on gas absorption under an electric field, and if it exceeds 5% by weight, it will not dissolve uniformly in silicone oil and will become cloudy.
Therefore, the amount added is within the range of 0.05 to 5% by weight. The silicone oil in the present invention relates to dimethyl silicone oil, but vinyl silicone oil,
Dimethyl silicone oil mixed with fluorosilicone oil, phenyl silicone oil, or a mixture thereof has similar effects, and is not limited to dimethyl silicone oil.

Examples will be explained below.

Example 1 Dimethyl silicone oil (manufactured by Toray Silicone KK, 25
Tables 1 and 2 show the gas properties, heat resistance, and lacquer properties of the products to which the required weights of xylenyl phosphate and tricresyl phosphite were added to the viscosity (St) at 5 °C.

Gas properties were measured as follows.

When an electric field is applied to oil in a hydrogen atmosphere, the oil generates or absorbs gas. The behavior of oil under such an electric field is called gas properties. In this application, the coexistence gas is 2,000 yen, and the method is based on the test method established by the Insulating Oil Subcommittee of the Agency of Industrial Science and Technology (Insulating Oil Subcommittee Sample No. 6, 1968 King, Corona Resistance Test Method for Insulating Oil). Measured at 5pi0. The gas characteristics are expressed by the pressure difference across the manometer (inner diameter 1 inch) after 120 minutes after setting the voltage at the chick V. A positive value indicates that gas was generated under the electric field, and a negative value indicates that gas was absorbed. The heat resistance of silicone oil is as follows: 150 ml of oil is placed in a glass ampoule with an internal volume of 300 ml, the air in the oil and the gas space above the oil surface is replaced with nitrogen gas, and the airtight seal is heated to 250 qo for 10 days. do. The degree of deterioration of silicone oil after deterioration was investigated by measuring the low molecular weight cyclic siloxane content of the oil. Table 1 Table 2 As is clear from the above examples, dimethyl silicone oil to which xylenyl phosphate or tricresyl phosphate is added has significantly improved gas properties and heat resistance.

Example 2 Table 3 shows the gas properties and heat resistance of dimethyl silicone oil (additive-free) and dimethyl silicone oil to which 0.5% by weight of various phosphate esters were added.

As is clear from the above examples in Table 3, the gas properties are not improved when trioctyl phosphate or trilauryl phosphite, which has no aromatic ring, is added.

On the other hand, phosphate esters having one or more aromatic rings have significantly improved gas properties and significantly improved heat resistance. Example 3 Table 4 shows the dielectric properties and flame retardance (flash point) of dimethyl silicone oil (no additives) and dimethyl silicone oil to which 0.5% by weight of various phosphate esters were added.

Table 4 Note: Cleveland-Auvencuff.

Claims (1)

[Claims] 1. An electrical insulating oil obtained by adding 0.5 to 5% by weight of an orthophosphoric acid ester having one or more aromatic rings and/or a phosphite having one or more aromatic rings to silicone oil.