Oil-immersed transformers rely on the oil inside them to function properly. Without the oil, the transformer would not operate normally, and its efficiency would not improve.
The commonly known function of the oil in an oil-immersed transformer is just the tip of the iceberg. How much do you know about the various functions of the oil in this type of transformer? Let's explore some of the common functions of the oil in an oil-immersed transformer.
Insulation: The oil used in oil-immersed transformers has much higher insulation strength than air. When insulation materials are immersed in oil, not only does it improve insulation strength, but it also avoids erosion by dampness.
Cooling: The specific heat of oil in oil-immersed transformers is high, making it an ideal coolant. When the transformer is running, the heat generated raises the temperature of the oil near the core and windings, causing it to expand and rise. This convection flow carries away heat through the radiator and ensures the normal operation of the oil-immersed transformer.
Arc suppression: Arcs can be generated when the contact points in oil circuit breakers or on-load tap changers of oil-immersed transformer are switched. The oil in oil-immersed transformers has good thermal conductivity and can decompose a large amount of gas when high-temperature arcs occur. This produces high pressure, thus improving the arc extinction capacity of the medium and quickly suppressing the arc.
The role of oil in oil-immersed transformers is significant. It is essential to maintain and improve the quality of the oil in order for the transformer to run safely and efficiently.
Temperature is an essential indicator for inspecting the operation of an oil-immersed transformer. As the transformer's temperature fluctuates constantly, its temperature must be continually monitored to keep the transformer running smoothly and to improve its efficiency.
What are common methods for measuring the temperature of oil-immersed transformers? Let's study them together with oil-immersed transformer manufacturers.
In general, the temperature of the coil specified by the standard refers to the average temperature since the temperature of each part of the coil in operation is different. Therefore, the standard only evaluates the average temperature of the coil.
Both oil-immersed transformers and dry-type oil-immersed transformers use the resistance method to detect the DC resistance of the coil (taking into account the environmental temperature during detection), which is the most direct and correct method and the method specified by the standard.
Dry transformers use temperature sensors inserted into the end of the coils, which detect the coil temperature during oil-immersed transformer operation, but cannot be used to evaluate whether the coil temperature is qualified.
In oil-immersed transformers, it is more complicated to embed a temperature sensor probe, which often detects the hottest point temperature of the oil-immersed transformer coil.
Infrared temperature detection is often used to detect the surface temperature of dry transformer coils and the temperature of the oil tank outside the oil-immersed transformer. According to the standard, the first detection method is commonly used.