THE PHASE DISPLACEMENT OF DC TOLERANT CURRENT TRANSFORMERS UNDER DC BIASING

Pavel Mlejnek – Petr Kašpar

   The most of the electronic static energy meters employ current transformers for current sensing. The current transformer has to fulfil some requirements according to international standards. Accuracy, together with the immunity against the dc current, is one of the requirements. Therefore manufactures of energy meter use the dc tolerant current transformers with linear hysteresis loop. These types of sensors have constant parameters and behaviour in very wide range of dc biasing. Second type of current transformers employs two cores with different parameters. But the parameters and behaviour vary with dc biasing. This paper deals with the changes of phase error of current transformers under dc biasing and describes the consequences of these changes.

Keywords: current transformer, phase displacement, dc biasing

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