Design changes to simplify maintenance and condition assessment on a tap changer

Sammanfattning: This master thesis investigates a redesign for a maintenance tube, used for both sampling and draining transformer oil from a tap changer compartment. With the current design, one can do one or the other of sampling and draining. The effect of this on a transformer site during maintenance means that personnel must bring extra equipment to do the maintenance routine. Along with the extra equipment, it also involves climbing the transformer an extra time to place the equipment for draining. The project aims to address several issues in the context of the product. Redesigning the product to reduce maintenance time, and therefore downtime and electrical outages. Reducing the number of times that the transformer housing needs to be climbed in order to perform maintenance work. This with the purpose of improving working environment for maintenance personnel. With the new design of the maintenance tube, draining and sampling can be done with the same pipe without the need for extra equipment. This is through a mechanism in the tube which allows the personnel to choose whether to drain oil from the bottom of the container or to take oil samples from an area in the tap-changer housing which gives more accurate results. The function of the mechanism can be described in the same way as a pen, where if you push the button, a tube will extract itself and close of the sampling inlets, enabling draining from the bottom. Push the button again and the same tube will retract, allowing you to take samples from the appropriate area again. The new design also adheres to the dimensional requirements needed for the design to fulfil the additional functions the tube has. The project results in a design which would not only fill requirements of functions but also preserves some of the previous parts along with their interfaces. This means that the new design could be installed on current versions of tap-changer models when the next service interval is due.