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An Active-Shunt Diverter for On-load Tap Changers

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2 Author(s)
Rogers, D.J. ; Institute of Energy, Cardiff University, Cardiff, UK ; Green, T.C.

This paper presents a new hybrid diverter design for on-load tap changers. The design uses “active-shunt” current diversion principles. At its core, the design employs a low-voltage high-current switch-mode amplifier to divert current out of the mechanical contacts and into a pair of anti-parallel thyristors. Commutation between transformer taps may then be performed by the thyristors. The amplifier and thyristors are placed outside the normal load current path and only conduct during a tap change, producing efficiency savings and improving robustness when compared to previous hybrid on-load tap changer implementations. An amplifier control loop that autonomously produces zero-current conditions at switch opening and zero-voltage conditions at switch closure is demonstrated. Experimental results investigating the wear characteristics of contacts operated under the new hybrid diverter are presented, along with comparison results from a passive-type switching scheme. Contact lifetime of more than 25 million operations is demonstrated under the new scheme.

Published in:

Power Delivery, IEEE Transactions on  (Volume:28 ,  Issue: 2 )