Electronic current transformer based on low-power current transformer

An electronic current transformer based on a low-power current transformer (LPCT) is developed to overcome the disadvantages of traditional current transformer for the complexity of insulation, magnetic saturation of coils as well as the measuring accuracy of Rogowski coils that can be influenced by temperature characteristic and manufacturing technology. The output of the LPCT is converted to digital light pulse signal using an active electronic circuit at the high-tension side; the signal is then transmitted to the control room through a cable of optic fiber; the measuring and relay channels are provided after the signal processing unit in the control room. Testing results show that the electronic current transformer can meet the accuracy requirement of IEC 60044-8 0.2 class for measuring current transformer and 5P20 class for protective current transformer. Temperature test results show that the ratio error changes within ± 0.1% and phase error within ± 2′ at -30°C-70°C.