คำตอบที่ 1
เติมได้ แต่ไม่นานเครื่องคงเจ๊ง
เพราะคุณสมบัติของมันไม่ได้ทำมาเพื่อหล่อลื่น แต่ทำมาเพื่อเป็นฉนวนไฟฟ้า และใช้ระบายความร้อนของตัวหม้อแปลง
The insulating fluid that has the greatest use in electrical equipment is mineral oil. There are insulating
materials that may be superior to mineral oil with respect to both dielectric and thermal properties;
however, to date, none has achieved the requisite combination of equal or better performance at an equal
or better price. Consequently, mineral oil continues to serve as the major type of liquid insulation used
in electrical equipment
For electrical equipment, the main concerns are:
Paraffinic oils tend to form waxes (solid compounds) at low temperature.
Paraffinic oils have a lower thermal stability than that of naphthenic and aromatic oils.
Paraffinic oils have a higher viscosity at low temperature than that of naphthenic and aromatic oils
These factors can impair the performance of high-voltage electrical equipment. The first two factors
have an unfavorable effect on the dielectric characteristics of the oil. The third factor unfavorably affects
the heat/dissipation ability of the oil. Unfortunately, the availability of insulating oil is limited. Therefore,
electrical equipment owners have a choice of only a few producers, who produce only a very few different
products.
3.1.2.2 Functions of Oil
3.1.2.2.1 Electrical Insulation
The primary function of insulating oil is to provide a dielectric medium that acts as insulation surrounding
various energized conductors. Another function of the insulating oil is to provide a protective coating
to the metal surfaces within the device. This coating protects against chemical reactions, such as oxidation,
that can influence the integrity of connections, affect the formation of rust, and contribute to the
consequent contamination of the system.
Insulating oil, however, is not a good lubricant. Despite this fact, it is widely used in load tap changers,
circuit breakers, and transformers. Therefore, Its use in these devices presents a challenge to the mechanical
design of the system.
3.1.2.2.2 Heat Dissipation
A secondary function of the insulating fluid is to serve as a dissipater of heat. This is of particular
importance in transformers where localized heating of the windings and core can be severe. The oil aids
in the removal of heat from these areas and distributes the thermal energy over a generally large mass
of oil and the tank of the device. Heat from the oil can then be transferred by means of conduction,
convection, and radiation to the surrounding environment.
All mineral oils are comparable in their ability to conduct and dissipate heat. To ensure that a given
oil will perform satisfactorily with respect to heat dissipation, several specifications are placed on the oil.
These specifications are based upon certain factors that influence the oils ability to dissipate heat over
a wide range of possible operating conditions. These factors include such properties as viscosity, pour
point, and flash point.
3.1.2.2.3 Diagnostic Purposes
The third function of the insulating fluid is to serve as an indicator of the operational condition of the
liquid-filled equipment. The condition (both chemical and electrical) of the insulating fluid reflects the
operational condition of the electrical device. In a sense, the fluid can provide diagnostic information
about the electrical device much like blood can provide diagnostic information about the human body.
The condition of the blood is important as it relates to its primary function of transporting oxygen and
other chemical substances to the various parts of the body. Indeed the condition of the blood is symptomatic
of the overall health of the body. For example, the analysis of the blood can be used to diagnose
a wide variety of health problems related to abnormal organ function.
In much the same way, insulating fluid can be viewed as serving its primary functions as an insulator
and heat dissipater. It can also be viewed as serving another (and perhaps equally important) function
as a diagnostic indicator of the operational health of liquid-filled equipment. This is possible because
when faults develop in liquid-filled equipment, they cause energy to be dissipated through the liquid.
This energy can cause a chemical degradation of the liquid. An analysis for these degradation products
can provide information about the type of fault that is present
จากหนังสือ Electric Power Transformer
