5-192 G30 Generator Protection System GE Multilin5.6 GROUPED ELEMENTS 5 SETTINGS5b) THIRD HARMONIC NEUTRAL UNDERVOLTAGEPATH: SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) STATOR GROUND 3RD HARM NTRL UNDERVOLTAGEThe third harmonic neutral undervoltage function detects a loss of third harmonic voltage at the generator neutral. The per-centage of stator winding covered by this function depends on the pickup setting and the amount of third harmonic gener-ated by the machine at the time of the fault. A settable window of forward power can supervise this element for enhancedsecurity. The element is also supervised by positive-sequence voltage measured at the generator output terminals. Thiselement can be used with either wye or delta connected VTs on the terminal side and requires the machine neutral voltageto be connected via an auxiliary voltage channel of a relay VT bank.• 3RD HARM NTRL UV PICKUP: This setting specifies the pickup level for the magnitude of the third harmonic of theneutral voltage. This setting is entered in pu of the nominal auxiliary voltage.The magnitude of the third harmonic voltage at the neutral point is monitored in the ACTUAL VALUES METERING STATOR GROUND menu. Measuring the actual value of the operating quantity for a specific machine under variety ofload conditions may be helpful when selecting the pickup threshold for this feature.• 3RD HARM NTRL UV MAX POWER: This setting specifies the maximum active power that inhibits this protectionfunction. If the measured power is below this setting but above the 3RD HARM NTRL UV MIN POWER setting the elementshall not operate. This setting applies to three-phase power and is entered in pu. The base quantity is 3-phase poweron primary side, which is calculated as x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case ofdelta connected VTs; and 3 x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of wye connectedVTs.For example, a setting of 20% for a 200 MW machine, is 0.20 × 200 MW = 40 MW. If 7.967 kV is a primary VT voltageand 10 kA is a primary CT current, the source pu quantity is 239 MVA, and thus, the pu power setting is 40 MW /239 MVA = 0.167 pu.• 3RD HARM NTRL UV MIN POWER: This setting specifies the minimum active power that inhibits this protection func-tion. If the measured power is above this setting but below the 3RD HARM NTRL UV MAX POWER setting the element shallnot operate. If the 3RD HARMONIC NTRL UV MIN POWER is set to “0.00 pu”, then the element will not operate for all powervalues less than the 3RD HARM NTRL UV MAX POWER setting.This setting applies to three-phase power and is entered in pu. The base quantity is 3 × VT pu base × CT pu base.If the VTs are located on the high-voltage (HV) side of the transformer, then the source should be configured usingCTs that are also on the HV side. Correspondingly, if the VTs are located on the low-voltage (LV) side of the trans-former, then the source should be configured using CTs that are also on the LV side. In both cases, the CT polarityshould produce a positive power measurement when the machine is generating. 3RD HARM NTRL UNDERVOLTAGE3RD HARM NTRL UVFUNCTION: DisabledRange: Disabled, EnabledMESSAGE 3RD HARM NTRL UVPICKUP: 0.3000 puRange: 0.0000 to 3.0000 pu in steps of 0.0001MESSAGE 3RD HARM NTRL UV PKPDELAY: 0.00 sRange: 0.00 to 600.00 s in steps of 0.01MESSAGE 3RD HARM NTRL UV MAXPOWER: 0.200 puRange: 0.000 to 30.000 pu in steps of 0.001MESSAGE 3RD HARM NTRL UV MINPOWER: 0.200 puRange: 0.000 to 30.000 pu in steps of 0.001MESSAGE 3RD HARM NTRL UVVOLT SUPV: 0.500 puRange: 0.000 to 1.250 pu in steps of 0.001MESSAGE 3RD HARM NTRL UV BLK:OffRange: FlexLogic operandMESSAGE 3RD HARM NTRL UVTARGET: Self-resetRange: Self-reset, Latched, DisabledMESSAGE 3RD HARM NTRL UVEVENTS: DisabledRange: Disabled, Enabled3NOTE
