Improvement the Quality of Mineral Insulating Oil at High Voltage Equipments Using Vegetable Oil

Abstract

There is widespread global interest into research which related to improving the performance of power transformers and electrical equipment by improving the technical specifications of insulating oils used in high voltage equipments. Transformers considered the main part at high voltage networks,  where most of the faults in transformers cost money either for repair or replacement. Mineral oil is one of the most common liquid insulating materials used in insulation. The development of the properties of insulating liquids is connected to several factors, such as environmental requirements and other factors related to safety or economic cost. Vegetable oils are considered a new candidate to replace mineral oils in the future.

The aim of this research to verify:

• The possibility of using vegetable oil and its mixtures with mineral oils as insulating oils at power transformers.
• Verification of the effect of temperature on the breakdown voltage of the resulting mixtures, which are six mixtures with different ratios of mineral/vegetable oils.
• Determine the best ratio for mixing under the influence of temperature which fulfills the requirements of international standards for use at power transformers.

 All tests related to this research were carried out according to the international standard test procedures IEC60156. The results of this research indicated that an improvement of the characteristics of power transformers could be achieved via the improvement of the insulating liquid characteristics . Using mixtures of vegetable and mineral oils can be considered as an alternative liquid insulator for mineral oils in transformers, and showed the effect of temperature change on the value of the breakdown voltage of the resulting mixtures as ,the highest value of the breakdown voltage was at a temperature of 80°C, and the ratio 25% of the used mineral oil with 75% of the vegetable oil was chosen as the best mixing ratio of the vegetable and mineral insulating oils that achieve the required insulation