engleski

Differential Protection Issues for Combined Autotransformer - Phase Shifting Transformer

In Žerjavinec substation, Croatian Power Company going to install a special type of power transformer, which has two different modes of operation. The power transformer can be used either as conventional 400MVA, 400/220kV autotransformer with on-load tap-changer or as phase shifting transformer interconnecting 400kV & 220kV networks. When power transformer is de-energized, its operation mode can be changed. This change can be done even remotely, by the network control centre in order to maximize utilization of the electrical network infrastructure. Two different operating modes of the power transformer, as well as remote selection facility, drastically complicate selection of power transformer protection scheme. Especially, proper operation of the power transformer differential protection must be assured during all operating conditions. Necessary calculations for proper selection of power transformer differential relay and final solution for overall power transformer protection scheme will be presented in this paper.

Autotransformer; Phase Shifting Transformer; Relay protection; Power transformer Differential protection

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