Abstract
Abstract A protection device is proposed that combines the functions of current transformers and current relays. The device contains a reed switch, two capacitors, two miniature relays, and three resistors. Reed switches are attached near the tires of the electrical installation at a safe distance. Relay parameters are calculated based on the operator method. The relay meets the requirements of sensitivity and performance. Unlike similar ones, it does not activate unnecessarily when contacts stick and the short-term interference is present, it is equipped with test diagnostics and simple mounting structures that allow the parameters of the relay operation to be adjusted. An experimental test confirmed the operability of the device.