Neutral Overvoltage Unit (High Level And Low Level) - GE Multilin F650 Instruction Manual

5 SETPOINTS
5.4.8.3 NEUTRAL OVERVOLTAGE UNIT (HIGH LEVEL AND LOW LEVEL) (59NH/59NL)
59NH unit is a neutral overvoltage protection element that uses as input magnitude the system neutral voltage (3V0)
calculated from the phase voltages, or the voltage value measured by the 4
unbalanced system voltage conditions, caused by a ground fault condition, or by the loss of one or two of the voltages. The
unit time delay is selectable between 0 and 900 seconds. The unit incorporates a reset with a selectable delay between 0
and 900 seconds.
A setpoint makes the selection of the input voltage for this unit, either calculated from the phase voltages or measured from
the 4th transformer of the F650. The setpoint to select the source of this voltage is configured in Setpoint > System Setup
> General Setpoint >Auxiliary Voltage (Vn or Vx). By selecting Vn, the neutral voltage used in the phase overvoltage
element will be measured at the fourth relay voltage transformer (A11-A12), and in this case the synchronism element of
the relay will not be available. If Vx is selected as auxiliary voltage, this setpoint corresponds to the busbar voltage input
used for the synchronism element, and the neutral voltage used in protection elements 59NH and 59NL will be calculated
from the phase voltages.
Notice that the neutral overvoltage element will not be available if a DELTA Connection is set in the Phase VT Connection
setpoint in General setpoints, and the fourth voltage transformer input is set to the busbar voltage for the synchronism
element (Vx in Auxiliary Voltage setpoint). This is due to the fact that with this combination of setpoints is not possible to
calculate the zero sequence component from the phase-to-phase voltage magnitudes.
Table 5–61: 59NH/59NL UNIT SETPOINTS
SETPOINT > PROTECTION ELEMENTS > VOLTAGE ELEMENTS >
>NEUTRAL OV HIGH > NEUTRAL OV HIGH 1> NEUTRAL OV HIGH 2 > NEUTRAL OV HIGH 3
>NEUTRAL OV LOW > NEUTRAL OV LOW 1> NEUTRAL OV LOW 2 > NEUTRAL OV LOW 3
SETPOINT DESCRIPTION
Function permission
Pickup Level
Trip time
Reset time
Snapshot Event generation
The snapshot event setpoint enables or disables the snapshot event generation for this unit.
If the voltage input is calculated from the phase voltages, the equation for obtaining the input value will be as
follows:
If the voltage input is set as the voltage measured by the 4
directly to the algorithm. This voltage can be taken through a grounding resistance, a high impedance grounding, a busbar
voltage etc.
GE Multilin
NAME DEFAULT VALUE STEP
Function DISABLED
Pickup Level 10
Trip Delay 10.00
Reset Delay 0.00
Snapshot Events ENABLED
3V = V + V
0 A
th
voltage transformer, then the metered value will be applied
F650 Digital Bay Controller
5.4 PROTECTION ELEMENTS
th
voltage transformer. It is used for detecting
RANGE
N/A [DISABLED – ENABLED]
1 V [3 : 300]
0.01 s [0.00 : 900.00]
0.01 s [0.00 : 900.00]
N/A [DISABLED – ENABLED]
+ V
B C
5
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