5-220 G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUALGROUPED ELEMENTS CHAPTER 5: SETTINGS5Figure 5-111: Phase directional logic5.7.5 Neutral current5.7.5.1 MenuSETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) NEUTRAL CURRENTThe phase directional element responds to the forward load current. In the case of a following reverse fault, theelement needs some time—in the order of 8 ms—to establish a blocking signal. Some protection elements, such asinstantaneous overcurrent, respond to reverse faults before the blocking signal is established. Therefore, acoordination time of at least 10 ms must be added to all the instantaneous protection elements under thesupervision of the phase directional element. If current reversal is of concern, a longer delay—in the order of 20ms—is needed. NEUTRAL CURRENT NEUTRAL TOC 1See below NEUTRAL TOC 2 NEUTRAL IOC 1See page 5-222 NEUTRAL DIRECTIONAL OC1See page 5-223 NEUTRAL DIRECTIONAL OC2
