A New Electronic Current Transformer Based on Light Intensity Detection of Light Emitting Diode

A389 electronic current transformer (ECT) based on light intensity detection of light emitting diode (LED) was presented. Two light emitting diodes were connected to the secondary winding. LEDs emitted infrared alternately and the radiant intensity was proportional to the primary current. Radiant intensity converted into voltage signal by two light-to-voltage optical sensors. Digital signal processor (DSP) captured the two signals and then calculated the primary current. Since secondary winding was floating potential and connected to the ground through optical fiber, the proposed electronic current transformer has the advantages of small size, low cost and strong insulation capability. The new method can be used to design protective current transformers. A 110kV/3000A prototype was designed and the experiments are conducted. The ratio error of designed prototype is 1% and phase displacement is 60u0027.