Operation Principles; Sensitive Ground Directional Unit (67Sg) - GE Multilin F650 Instruction Manual

5 SETPOINTS

OPERATION PRINCIPLES:

Operation of the isolated Ground unit is based on the detection of a current that exceeds the setpoint, with neutral voltage
supervision (3V0). This allows to set the unit in a very sensitive way, with a very low current level, ensuring that small angle
or ratio errors in the current transformers will not produce the relay operation, as the neutral voltage verified is higher than
the one set.
Values for h, IL, Vh and VL, which define the relay operation area, are configurable. H magnitudes must be higher than L
magnitudes. The 50IG unit can be supervised by directional unit 67SG.
Using the relay input magnitudes In and Vn, if the point defined by (In, Vn) is inside the operation area and if the directional
unit (if directional supervision is set) allows it, the unit picks up and the set delay time starts counting down. If a directional
block appears during the countdown, the unit is reset. After the set time the unit trips. Once tripped, the relay cannot be
blocked by the directional unit, and the trip remains while the fault exists.
After the trip, the deviation time to instantaneous starts to run, so that all pickups produced during this time will produce an
Instantaneous trip. This means that, if after a trip the breaker is reclosed and the fault persists or reappears, the relay trip
will be instantaneous. If the user doesn't want to use this function, then the Deviation Time to Instantaneous (Time to
inst) setpoint must be set to zero seconds. Once the time has expired, the unit returns to its normal operation.

5.4.6.4 SENSITIVE GROUND DIRECTIONAL UNIT (67SG)

Function 67SG is a directional element used for supervising sensitive ground overcurrent functions. The operation
magnitude is the ground current measured directly from the corresponding input (terminals B11-B12), while the polarization
magnitude is the neutral voltage (3Vo) either calculated from three phase voltages or measured from the dedicated voltage
input (A11-A12)
In case of using the voltage measured at the dedicated voltage input terminals, the Auxiliary Voltage setpoint in Setpoint
> System Setup > 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 67SG unit (AUXILIARY VOLTAGE setpoint as VN).
The same way as the directional unit for phases, it has a polarization voltage loss logic that allows blocking or producing
trip depending on the setpoint.
Table 5–57: 67SG UNIT SETPOINTS
SETPOINT > PROTECTION ELEMENTS > SENSITIVE GROUND CURRENT > SENSITIVE GROUND DIRECTIONAL >
SENSITIVE GROUND DIRECTIONAL 1> SENSITIVE GROUND DIRECTIONAL 2 > SENSITIVE GROUND DIRECTIONAL 3
SETPOINT DESCRIPTION
Function permission
Maximum Torque Angle
Operation Direction
Block logic type
Polarization voltage threshold
Snapshot event generation
Available setpoints are:
Function permission (Function): This setpoint determines whether the sensitive Ground directional unit is enabled or
Maximum Torque Angle (MTA): This angle is used to rotate the Polarization voltage. Positive angles mean counter
GE Multilin
NAME DEFAULT VALUE
Function DISABLED
MTA -45
Direction FORWARD
Block Logic PERMISSION
Pol V Threshold 10
Snapshot Events ENABLED
Disabled.
clockwise rotation, and negative angles mean delay (counter clockwise). The
polarization magnitude, once rotated, defines the MTA line. Vn rotated this angle points
the semi plane that corresponds to a Reverse fault. (-Vn) rotated this angle points the
semi plane that corresponds to a Forward fault.
F650 Digital Bay Controller
5.4 PROTECTION ELEMENTS
STEP RANGE
N/A [DISABLED – ENABLED]
1 Deg [-90 : +90]
N/A [FORWARD – REVERSE]
N/A [BLOCK – PERMISSION]
1 V [0 : 300]
N/A [DISABLED – ENABLED]
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