• Prok Devices Private Limited

Numerical Over Current & Earth Faulty Relay

Prok Devices’ PNA type numerical over current and earth faulty relay is a non-directional, combined over-current and earth fault relay or independent over current or earth fault relay intended for protection in medium-voltage networks. PNA type numeric relay receives input current signals (phase current and neutral current) via four input current transformers. These signals are galvanically de-coupled, suitably filtered and fed to the micro-controller within built A/D converter for amplitude calculation and further logical processing (i.e., samples, multiplexed). The micro-controller continuously monitors the magnitude of the phase current and the neutral current. Whenever the phase current or earth current magnitude exceeds the preset values corresponding line/earth element will pick up and relay will trip after the specific time interval calculated by the selected IDMT curves. Whenever the fault level exceeds the selected high set range, the relay will trip for high set, ignoring the selected IDMT curves. The timer logic is processed and after comparison with set time schedules, tripping signals are issued accordingly. There are two output relays, each out put relay has two changeover contacts either for alarm or tripping. The auxiliary supply for the numeric relay is provided by a switch mode power supply unit with input voltage either AC or DC with a wide operating voltage from 18-85 V or 85-275 V. And in case of AC, the power supply is designed operate from 45 to 65 Hz.