Power Industry

Sinopec transformer oil product standards and product series grades
Transfomer oil is one of the basic materials used in power transmission system, and mainly for insulation, cooling and heat dispersion of oil-filled electrical equipment, such as transformer, reactor, mutual inductor and switch,etc.
Sinopec transformer oil is composed of refined mineral base oil and selected antioxidant additives, without PCB. 
According to the using occasion, the amount of antioxidant additives and the lowest temperature, Sinopec transformer oil can be divided into multiple products.

Technical specification
The product meets the following specifications:
GB 2536-2011
IEC60296:2012
Q/SH303 0627-2013
Q/SH303 0628-2013
Q/SH303 0660-2017 (IEC 60296-2012)

Product series grades
According to the using occasion, the amount of antioxidant additives and the lowest temperature,Sinopec transformer oil can be devided into I-type transformer oil (general), I-type transformer oil (special), T-type transformer oil (general), U-type transformer oil (general), long life high cleanliness I-type transformer oil and super insulation transformer oil and other products. The grades are showed in the table below. 

Property Requirements of Transformer Oil
1. Appearance
Clear and transparent, without suspended solid or deposit at bottom, the color usually is water white or straw yellow.
2. Density
Density of oil has close relation with its compositions. As to transformer oil, the density shall be controlled low enough to effectively prevent floating ice in oil under cold climate which will consequently affect insulation property of oil.
3. Kinematic viscosity
Besides effect of insulation, transformer oil also provides effect of cooling and heat dispersion. As to transformer oil,proper high-temperature viscosity can ensure ideal effect of cooling and heat dispersion of transformer oil during long time service, while proper low-temperature viscosity can ensure working safety of lowest cold start of transformer.
4. Pour point
Pour point can reflects low temperature performance of transformer oil, from which low temperature environment for oil can be estimated.
5. Flash point
Flash point is a safety index of transformer oil during storage and use. Especially for supervision and control of transformer oil in service, flash point is an indispensable item. Descending of flash point indicates volatile combustible materials have been generated from oil. Such low molecular hydrocarbon is often generated during heating crack of transformer oil under high temperature, which is resulted from local overheating fault of electrical equipment. Therefore, from flash point, it can be observed whether electrical equipment have local overheating fault. For oil newly filled in equipment and after repair, checking flash point can discover whether there is light distillate mixed or not, thus ensuring operation safety of equipment.
6. Water content
Water content is a main factor affecting insulation property of transformer and aging of oil. Increasing of water content in transformer oil and insulation materials will directly result in decreasing of insulation property and aging of oil, which affects operation reliability and service life of equipment. To strictly supervise water content is a test item necessary for ensuring operation safety of equipment. However, care shall be taken to water absorptivity of transformer oil. Therefore, users shall implement vacuum dehydration treatment on transformer oil before filling it in equipment by requirements of guide for maintenance and supervision of transformer oil in service.
7. Interfacial tension
Interfacial tension refers to tension formed by interface between oil and water. Main functional groups of carboxylic acid, alcohol and ester and other active materials in oil belong to hydrophilic polar group, whose orientated arrangement on the two intersectant interfaces will change molecular arrangement status on the interface, thus reducing interfacial tension. The larger the interface tension value is, the less the hydrophilic polar materials in oil will be. To measure interfacial tension of transformer oil in service is an indirect and effective method for checking whether there is soluble polar impurities in oil resulted from aging. At initial aging phase of oil, the change of interfacial tension is slightly faster. The change speed will slightly reduce till medium-term aging phase, while oil sludge generated increases obviously. Therefore, measurement of interfacial tension also can reliably judge oil sludge generating trend of oil in service.
8. Breakdown voltage
Breakdown voltage is a very important index to check electric stress limit resistance of transformer oil, can be used to judge water content in transformer oil and pollution extent of other suspended solid, and check drying and filtering level of oil before filling it in equipment. Decreasing of breakdown voltage of oil in service is a signal for working danger of transformer. To avoid affecting water content and impurities in oil by transportation or other factors, users must remeasure transformer oil after filtering (dehydration) or other treatment before using.
9. Dielectric dissipation factor
Dielectric dissipation factor refers to power loss resulted from oil electrolytic polarization and conductance under electric field. Pure hydrocarbon is non-polar compound, which never or occasionally translocate under electric field, so no power loss will be generated. However, impurities in oil, such as gummy matter and acid polar materials will translocate with change of power line direction under electric field, which consumes part of power for transforming into heat. Therefore, such impurities not only consume power, but also increase temperature and reduce working capacity of transformer, thus accelerating aging and deterioration of transformer oil. For transformer oil in service, dielectric dissipation factor can send signal earlier than other indexes. From the value of dielectric dissipation factor, deterioration and pollution extent of oil can be judged.Generally, fresh oil has less impurities and polar components etc. so dielectric dissipation factor is less. However, when oil deteriorates or mixes with other impurities, as increasing of polar materials or impurities content in oil, dielectric dissipation factor will increase too. Therefore, dielectric dissipation factor is of vital importance for quality supervision of oil in service.
10. Oxidation stability
Affected by oxidation catalysis of iron core, copper core and other metals and high oil temperature in service, transformer oil will age and form acid materials, and low molecular watersoluble acid will corrupt solid insulation materials greatly. In addition, transformer oil will generate oil sludge after severe oxidation. The oil sludge separated will deposit on surface of iron core and coil, which results in bad thermal conductivity and high temperature rise of solid insulating layer as well as aging and cracking of solid insulation materials, thus greatly threatening long time operation of transformer. Transformer oil with good oxidation stability can not only reduce the cost of repair and oil changing, but also benefit long operation of transformer. Therefore, oxidation stability is an important index of transformer oil.