GE Multilin G60 Generator Protection System 9-79 APPLICATION OF SETTINGS 9.1 SETTING EXAMPLE9The zone 3 reach will be set at 120% of the generator transient reactance. The time delay of this element should be com-pared to the generator decrement curve to verify the adequacy of this setting.(EQ 9.28)(EQ 9.29)An mho shape has been chosen for this example. Therefore, the quadrilateral settings are left at their default values. Makethe following changes in EnerVista UR Setup or through the SETTINGS GROUPED ELEMENTS SETTING GROUP 1 DISTANCE PHASE DISTANCE Z1(3) menus:9.1.11 STATOR GROUND FAULTa) AUXILIARY OVERVOLTAGEStator ground fault protection is implemented with an overvoltage element connected at the generator neutral resistor. Theauxiliary overvoltage element will be used in this example. The auxiliary voltage input has previously been assigned to theNEUTRL source. In this example the element will be set to protect 97% of the stator against ground faults.(EQ 9.30)The time delay should be longer than the longest normal clearing time for faults outside the generator zone. If the phaseVTs are wye-connected then this element should also be coordinated with VT secondary fuses to prevent false operationsfor VT secondary ground faults. For the sample system a time delay of 1 second will be used. Make the following changesin EnerVista UR Setup or through the SETTINGS GROUPED ELEMENTS SETTING GROUP 1 VOLTAGE ELEMENTS Generator impedance X dV L2MVAG----------------× j1.967 18( )2211--------------× j3.01 primary ohms= = =Zone 3 reach 1.2 Generator impedance CT ratioVT ratio---------------------××=1.2 j3.01× 1600157.5---------------×= j36.68 secondary ohms=PICKUP 0.03 Nominal Phase Ground Voltage–Ground VT Primary----------------------------------------------------------------------------------------× 0.03 18000 3⁄12000----------------------------× 0.026 pu= = =
