The door-mounted NewElec GA relay range offers earth leakage protection that makes them suitable for use with VSDs as they include harmonic filtering. The earth leakage trip thresholds are spread over a range of 30, 250, 375, 500 and 1000 mA. However, the trip curve characteristic is user-selectable as instantaneous or inverse IDMT.
The earth leakage relays have been approved by many leading mining houses
The corresponding core balance CTs are available in diverse I.D. sizes but are designed for use with both instantaneous or IDMT selected trip curves. As such, protection grading for distribution networks may be achieved using the full range of relays.
GA relays are equipped with control panel mounted LEDs depicting the user selected trip curve, a relay ‘healthy’ LED and a relay ‘tripped’ LED.
The trip indicating LED is driven from the latching relay, which can only be reset by pressing the control panel mounted reset pushbutton. The main trip relay automatically resets once the earth leakage current is interrupted to permit the re-closing of the main MCCB when it has cleared the earth fault.
An additional start lock-out changeover contact shown across terminals 15 and 16 is latched open when the main trip contact energises to facilitate a forced reset on the control panel in order to re-close the circuit. An alternative use could be as an input to a PLC.
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