DC TOLERANCE OF CURRENT TRANSFORMERS AND ITS MEASUREMENT

Pavel Mlejnek – Petr Kašpar

   The measurement of energy is one of the most widespread measurements in energetics. The modern electricity meters mostly use the current transformers for current sensing. Two main errors exist in the current transformers: the ratio error and the phase displacement. These errors indirectly depend on amplitude permeability of the ferromagnetic core. The ferromagnetic core may be exposed to the DC magnetic field in the real condition. It causes saturation of the core and consequently rapid decrease of the amplitude permeability. It is important to know what value of magnetic field causes this problem. This article deals with the definition of DC tolerance of current transformers and the method of its measurement. Finally nine samples of current transformers have been measured and their properties have been compared.

Keywords: DC tolerance, current transformer, ratio error, phase displacement

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