For transformers in the choice of insulating materials, are generally used A-level insulation. That is, insulating materials have certain mechanical strength and electrical strength, mechanical strength is the ability to withstand mechanical loads (tension, pressure, bending, etc.); electrical strength (or dielectric strength) refers to the ability of insulation to withstand electrical breakdown. Transformers in the long run, due to atmospheric conditions and other physical and chemical effects of the insulation material mechanical and electrical strength of the gradual decline of the phenomenon, known as the insulation aging. When the insulation completely loses its elasticity, ie the mechanical strength is completely lost, there is still a considerable electrical strength as long as there is no mechanical damage. However, the loss of elasticity of insulation, has become dry, easy to brittle fracture, easy to damage due to vibration and electrodynamic force. Therefore, the degree of insulation aging can not be judged solely by the electrical strength, the degree of reduction of the mechanical strength must be considered, and mainly depends on the degree of reduction of the mechanical strength.
Transformer aging and service life is no specific requirements, but also related to the use of the environment, load factor, temperature and other factors, the aging aspect mainly refers to the degree of insulation aging, there is no correct instrument measurable, the general insulation test Generally divided into four levels:
1, good condition, flexible insulation, when pressed by hand will not produce deformation traces.
2, qualified, more rigid insulation, darker color, no cracks when pressed by hand, it will not be deformed.
3, not very reliable state, the insulation is hard and fragile, deep color, small cracks or deformation when pressed by hand, some manufacturers make the transformer, the original coil is poured insulating paint is black, do not misjudgment.
4, unqualified state, the insulation is very hard, when the hand is pressed off or cracks deep, or even into a carbon off the insulation. Three aging transformer, if the experiment everything is normal, you can continue to put into use, but in operation which pay attention to prevent overload, over-temperature operation, to the four aging must overhaul or replace the transformer. And then need to pay attention to the color and smell of the cooling oil is normal, the normal color is slightly yellow, clear and transparent, the smell is no cork smell, the rated load oil temperature is normal, the noise is normal.
