Measurement of Current in EHV and UHV Transmission Lines using YIG-tuned Devices

New systems for current measurement in HV DC and HV AC transmission are described. The systems utilize the YIG-tuned devices placed in close vicinity of the HV line conductor as a magnetic field sensor. The output signal of the system is proportional to the resonant frequency of the YIG sphere in the YIG-tuned device. This resonant frequency is linearly dependent on the magnetic field created by current to be measured. The system consists of two basic parts, a high potential unit placed at the HV line conductor and a ground potential unit. These both parts are connected by microwave link which provides necessary isolation. The block diagrams of the systems and some of the investigation results are given.