NewElec’s GA relay range protects variable speed drives against earth leakage faults or down-grading earth leakage protection thresholds, thereby avoiding nuisance trips on start-up. All GA relay models may be configured for either IDMT or instantaneous trip delay and include harmonic filtering. It is possible, for instance, to start a 250 kW motor by the direct-on-line method with a set 250 mA sensitive earth leakage trip threshold and not experience any nuisance trip whatsoever in the process. This can be done even when the instantaneous trip selection has been selected.
GA relays may be used to advantage when structured grading protection is required from the motor upstream in the distribution feeding train, as a number of GA models starting at 30 mA upwards are available. The relay is not passive and will require a supply of either 110 or 220 V AC, ideally supplied from a source upstream of the main feeder.
As a door-mounted unit, the front control panel clearly displays the user tripping curve selected, as well as the relay trip status by means of suitably coloured LEDs. The indicator and trip relay are latched until the control mounted reset pushbutton is pressed. However, the relay will automatically reset if the earth leakage current is removed to permit auto re-closure.
An additional feature is that the earth leakage cores used by NewElec may be used with either IDMT or instantaneous user selection curves, eliminating the need to stock two separate core types.
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