Earth-leakage protection relay RD-1

for electric motorsDIN railautomatic reset

The Earth Leakage Relay RD is a microprocessor-based electronic protection device designed to recognize low-level leakage or unbalanced currents, due to insulation loss on conductors or equipment to be protected. The fundamental feature of the RD is to allow preventive control of the system's insulation with continuous display of the earth leakage current value for motors, transformers and power systems. The measure of the leakage currents is obtained by the use of a ring-type current transformer in witch all conductors of the circuit to be protected shall go through. The RD Relay is designed with a microprocessor in order to satisfy all protection requirements and to guarantee utmost reliability. The microprocessor carries up several functions, such as: - Digital display of earth-leakage or unbalanced currents (up to 20 A) - 1 Logic input for external reset. (only RD-1) - Independent digital current adjustments for alarm and tripping from 25 mA to 20 A. - Independent digital time adjustments for alarm and tripping, from 0.03 to 5 Sec. - Visual indication and storage of the maximum fault current for later viewing. The memory doesn’t lose the value after a power loss. - Integral test (relay + wiring + current transformer) with or without activation of the output relays. - Continuous control of wiring connection between the RD-1 and the current transformer. - Programmable local or automatic reset. The automatic reset mode includes a reset protection, which allows up to three automatic operations in maximum 9 minutes before blocking further reclosures (lockout). - Control through two out-put operational relays: alarm and tripping.