Negative sequence voltages arise when the virtual representation of the phase rotation for an
unbalanced system appears negative.
Negative sequence voltages can occur where there are single phase loads, unbalanced line
short circuits and open conductors, and/or unbalanced phase-to-phase or phase-to-neutral
loads.
The alarm response is based on the estimated phase-to-neutral voltage phasors, as measured
from the source.
Controller types: This alarm is present in the GENSET and BUS TIE breaker controllers.
Configure the parameters under Configure > Parameters > [Source] > Voltage protections > Negative sequence voltage.
Table 3.33
Default parameters
Parameter Range Negative sequence voltage
Set point 1 to 100 % of nominal voltage 5 %
Time delay 0.1 s to 1 h 0.5 s
Enable Not enabled, Enabled Not enabled
Action Warning
3.4.6 Zero sequence voltage (ANSI 59Uo)
Protection
IEC symbol (IEC60617) ANSI (IEEE C37.2) IEC 61850 Operate time
Zero sequence voltage 59Uo PZOV < 200 ms*
*Note: This operate time includes the minimum user-defined delay of 100 ms.
Zero sequence voltages arise when the phases rotation is positive, but the vector zero value
(star point) is displaced. This zero sequence voltage protection can be used instead of using
zero voltage measurement or summation transformers (zero sequence transformers).
This protection is used for detecting earth faults.
The alarm response is based on the estimated phase-to-neutral voltage phasors, as measured
from the source.
Controller types: This alarm is present in the GENSET and BUS TIE breaker controllers.
Configure the parameters under Configure > Parameters > [Source] > Voltage protections > Zero sequence voltage.
Table 3.34
Default parameters
Parameter Range Zero sequence voltage
Set point 1 to 100 % of nominal voltage 5 %
Time delay 0.1 s to 1 h 0.5 s
Enable Not enabled, Enabled Not enabled
Action Warning
DESIGNER'S HANDBOOK 4189340911K UK Page 65 of 521
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