LV generator protection - engineering site - Schneider Electric
LV generator protection - engineering site - Schneider Electric
LV generator protection - engineering site - Schneider Electric
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4.3.1.2. Source Ground Return (SGR)The “Source Ground Return” system directly measures the earth fault current bya specific external sensor.This <strong>protection</strong> detects faults upstream and downstream of the circuit-breaker.It is only possible at the supply end of the <strong>LV</strong> installation.E88019 E88018Figure 33.Note: the SGR CT is specific to this application.The Ground <strong>protection</strong> and Neutral <strong>protection</strong> are separate and thus can becombined.Setting the <strong>protection</strong> devicesGround <strong>protection</strong> can be set for its threshold (limited to 1200 A) by 9 bands andby its time delay (same as the Short Time Delay).To enhance discrimination with fuses or other circuit-breakers, part of the ground<strong>protection</strong> curve can be converted into a reverse curve by choosing the l 2 tONsetting.The SGR <strong>protection</strong> requires use of the MDGF module.4.3.2. Residual current device (RCD) <strong>protection</strong> or“zero sequence” systemRCD <strong>protection</strong> is stipulated by installation standards (IEC 60 364) for <strong>protection</strong>of people and equipment in the following cases:b TT type grounding systems, in which currents resulting from insulation faultsare smallb TN-S type networks with very long cables, in which the instantaneous thresholdis not sufficient to protect a short-circuit at the end of the lineb IT networks with very long cables.This <strong>protection</strong> is also used to provide additional fire <strong>protection</strong>.Its threshold from 500 mA to 30 A and time delay can be set to ensure residualcurrent discrimination.Figure 34.An external rectangular toroid sensor is compulsory.39