Design and Research on the Improvement Scheme of Purely Mechanical On-load Tap-changers

A purely mechanical on-load tap-changer has the problem of arcing and transition wearing in the operation process because of its mechanical structure, thus should be maintained and overhauled regularly, which costs a lot of resources and has been concerned by a large number of engineering technical researchers. Consequently, on the basis of the engineering practice, taking a mechanical type of vacuum sliding integrated topology OLTC in China as an example, we theoretically researched and practically analyzed the aspects of arc restriction and reduction of working loss. Moreover, we analyzed the preliminary improvement scheme and the improvement mechanism; under the condition of not changing the original mechanical topology, we realized the optimization operation of equipment by adding auxiliary power electronic switch, and realized the elimination of the transition wear and decrease of the working pressure of the contact. Furtermore, a small power prototype was designed and built in the laboratory by the method of model-based design to realize the sequence control of diverter. Through modeling simulation and experimental analysis, the improved diverting arc burning time could be reduced to about 100μs, thus the diverting arc power could be effectively suppressed. This study can lay a theoretical and practical foundation for the full power tests in the future. © 2019, High Voltage Engineering Editorial Department of CEPRI. All right reserved.