Vapour Phase Equipment for the Production of Power Transformers
Vapour phase drying systems are used for the production of power transformers and other high-voltage components. The technology requires – compared with drying processes using air – about just 25–40% of the time.
The production process of power transformers would be unthinkable without the drying technology by means of kerosene (vapour phase process). But also for other high-voltage components this process is applied. With its outstanding heat transferring coefficients the drying time is nearly halved compared to traditional drying processes using air. This energy-efficient process also minimizes thermal damage to the insulating material.
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Fall Film Evaporator |
The fall film evaporator that is installed outside of the vacuum chamber ensures homogenous heating through droplet-free kerosene vapour. The distillation (separation of kerosene from transformer oil washed out of the insulation) can take place in parallel without affecting the drying process. The transformer oils occurring in case of oil-impregnated repair transformers can therefore be immediately pumped off during the distillation process.
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Optimal Energy Supply |
With the patented system of condensate accumulation in the main condenser, the effective condensation surface is adjusted depending on the actually loaded parts (quantity of insulation, iron, copper etc.) so that only the kerosene portion condenses with water that is needed for fast drying. This construction guarantees that only the required energy is needed – a benefit to the total energy balance of the system and drying process.
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Online Determination of Residual Moisture |
HEDRICH was the first manufacturer to integrate into its vapour phase systems an electronic measuring instrument to determine the residual moisture of the parts to be dried. The sensors are constructed in such a way that the water diffuses through a gold membrane allowing only water vapour but no kerosene to pass and altering an applied electric field. The dew point is determined in comparison to an integrated calibration curve. A conversion into the water rate is possible.
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High-Performance Pumping Unit |
For high pumping speeds and a low ultimate vacuum HEDRICH developed the following solution for the vacuum pumping unit: use of liquid ring pumps with kerosene as sealing agent – combined with Roots pumps. This excludes the risk of kerosene condensation in the oil of conventional rotary vane pumps. When required, HEDRICH also delivers pump combinations with rotary vane pumps and dry pumps.
Advantages of the vapour phase equipment
• Energy-efficient controlled condensation by extracting kerosene/water vapour
• Large collecting vessel for kerosene – optimal for drying repair transformers
• Complete heating of the autoclave by heat transferring oil, including the door
• Auto-adaptation to adjust the drying process to the batch size
• Integrated safety PLC to increase the process safety
• Vacuum-tight and maintenance-free angle valves
• Parallel distillation during the drying process
• Online registration of dew point and water rate during the fine vacuum phase
• Stationary and mobile vapour phase systems are available
Applications
• High-voltage transformers
• Distribution transformers
• High-voltage bushings
