Research on characteristics and mechanism of transformer fifth harmonic under overexcitation condition

Abstract

Abstract:

The magnetic density of modern high-capacity transformers is large while running. In the case of shortterm overvoltage (overexcitation), the transformer excitation current will surge, which can easily cause the maloperation of differential protection. It is necessary to use the harmonic content of the excitation current to lock the differential protection when the multiple of overvoltage is small. The relationship between the excitation current fifth harmonic and the voltage of the transformer is deduced based on fitting 2 lines of transformer magnetic characteristic with 2 different slopes. Transformer overexcitation model is built by the simulation software PSCAD/EMTDC. The theoretical derivation and simulated waveform are compared, which verifies the correctness of the theoretical formula. It discusses the fifth harmonics locking values for transformer protection under overvoltage conditions.

Key words:

transformer, excitation current, fifth harmonic, overvoltage, locking value

WANG Zhe，GUO Xiao，XING Wu，HU Bing.

Research on characteristics and mechanism of transformer fifth harmonic under overexcitation condition

[J]. Huadian Technology, 2019, 41(5): 22-27.

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Research on characteristics and mechanism of transformer fifth harmonic under overexcitation condition

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