White Papers

Job Done: Transformer Paralleling with IEC 61850 GOOSE Messaging

By Joe Orth, Seattle City Light, Alan Beserra, POWER Engineers, Aaron Cowan, POWER Engineers


When multiple transformers with Load Tap Changers (LTC) can be operated in parallel, the paralleled status must be monitored, and the tap position must be controlled to avoid circulating current. Seattle City Light built a new substation in an urban location designed with a ring bus distribution system fed by three (with a future fourth) bifurcated transformers. A LTC Master-Follower scheme was designed to monitor the parallel status of the transformers and manage tap positions to eliminate circulating current. Various issues were encountered during the deployment of this scheme due to the complicated distribution topology. This paper discusses the design considerations, logic development, off-site testing, and on-site testing involved in implementing the scheme.

This paper was presented at the 2019 Power & Energy Automation Conference and Energy Summit.

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