GE Multilin F650 Digital Bay Controller 5-57
5 SETPOINTS 5.4 PROTECTION ELEMENTS
5
5.4.5.3 GROUND DIRECTIONAL UNIT (67G)
67G unit is a directional protection element, used for monitoring the ground overcurrent units. The operation magnitude is
the ground current measured directly from the corresponding input (B9-B10), while the polarization magnitude is the neutral
voltage (3Vo) calculated from the three phase voltages or measured from the dedicated voltage input (A11-A12).
In case of using the voltage measured from the dedicated voltage input terminals, the Auxiliary Voltage setpoint in
General setpoints must be VN.
If the F650 is set to have synchronism check protection, then this input will be adjusted as busbar voltage and it will not be
the 3V0 voltage (AUXILIARY VOLTAGE setpoint as VX)
If the F650 does not have a synchronism check unit, then this input can be set as 3V0 neutral voltage, and it can be used
as polarization magnitude for the 67G unit (AUXILIARY VOLTAGE setpoint as VN).
As in the case of a phase directional unit, this element incorporates a voltage loss logic that allows blocking or permitting
the trip by means of a setpoint
Table 5–51: 67G UNIT SETPOINTS
Operation of the Ground directional unit 67G is similar to the operation of the neutral directional unit 66N (please refer to
section NEUTRAL DIRECTIONAL UNIT (67N)), with the exception that the operation magnitude here is the ground current
Ig (67G), measured from the input terminals B9-B10 instead of the Neutral current, In (67N), calculated from the phase
currents.
Polarization magnitudes can be, as in the case of 67N, Polarization voltage (3V0), either calculated from the phase
voltages or measured from terminals A11-A12, or polarization current (Ip), measured from the firth input transformer
terminals, Isg, terminals B11-B12.
The following table shows the used magnitudes in each of the Polarization possibilities:
Table 5–52: USED MAGNITUDES ACCORDING TO THE POLARIZATION SETPOINT
SETPOINT > PROTECTION ELEMENTS > GROUND CURRENT > GROUND DIRECTIONAL >
GROUND DIRECTIONAL 1> GROUND DIRECTIONAL 2 > GROUND DIRECTIONAL 3
SETPOINT DESCRIPTION NAME DEFAULT VALUE STEP RANGE
Function permission Function DISABLED N/A [DISABLED – ENABLED]
Maximum Torque Angle MTA -45 1 Deg [-90 : +90]
Operation Direction Direction FORWARD N/A [FORWARD – REVERSE]
Polarization type Polarization VO N/A [V
0
– I
P
– V
0
+I
P
– V
0
*I
P
]
Block logic type Block Logic PERMISSION N/A [BLOCK – PERMISSION]
Polarization voltage threshold Pol V Threshold 10 1 V [0 : 300]
Snapshot event generation Snapshot Events ENABLED N/A [DISABLED – ENABLED]
POLARIZATION SETPOINT OPERATION MAG. POLARIZATION MAG.
Vo Ig 3V0
Ip Ig Isg
Vo + Ip Ig 3V0 or Isg
Vo * Ip Ig 3V0 and Isg
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