Resource-Saving Current Protections

Works on creation of resource-saving protections without the use of measuring current transformers with metal cores have been carried out since the 60s of the 20th century. To build relay protection without measuring current transformers, in this work inductance coils and reed switches, which were magnetic field sensors, were used. Magnetic fields created by the currents of the current-carrying phases of complete switchgear cells have their maximum values in the immediate vicinity near the center of these busbars. These maximum values of magnetic fields in the form of EMFs are picked up inductance coils and reed switches. The reed switch and the inductance coil are installed in the location of the switchgear panel where the maximum magnetic induction is present. The inductance coil is the sensing element of the resource-saving protection. The reed switch is the sensing and actuating element of the resource-saving protection. Inductance coils and reed switches were chosen because, in comparison with other magnetically controlled elements, they have advantages for relay protection, such as: reed switches, for example, do not require amplifiers for signal transmission; the signal transmission itself is carried out through control circuits, not through measuring circuits; reed switches and inductance coils do not need temperature compensation devices. Reed switches can simultaneously act as an analog-to-discrete converter, a measuring converter and a measuring protection device. Inductance coils perform the functions of measuring converter and measuring protection body. The research relates to the protection of high-voltage electrical installations.