The operation of existing relay protection devices is based on the measurement of electrical network parameters (voltage, frequency, current) performed using sensors installed in the electrical network. Current sensors are subject to high requirements for output data in various modes of operation of the electrical network. As current sensors in the 0.38 kV electrical grid, the following are widely used: current transformers, transreactor sensors, resistive sensors, Hall effect current sensors. (Research purpose) The research purpose is experimentally studying current sensors of various types used in electrical networks of 0.38 kilovolts. (Materials and methods) Conducted laboratory studies on a prepared laboratory stand of various current sensors in three operating modes: steady-state mode, switching mode with initial magnetic flux, switching mode without initial magnetic flux. (Results and discussion) It has been shown that not all types of current sensors can be used as a source of reference data in the construction of high-speed current protection. It was determined that transformer-type sensors can introduce a significant error in the operation of relay protection for reasons of significant angular error, pronounced processes of magnetization and enticement in switching modes. It was found that sensors based on the types of transreactor and Hall effect have the lowest angular error and resistance to switching modes. (Conclusions) It was revealed that when choosing current sensors as a source of reference data, not only passport characteristics, but also laboratory studies should be taken into account. The necessity of taking into account the operational operating time and inductance of the current sensor, the angular error and the shape of the current curve of the secondary circuit was stated.