GE G60 Instruction Manual page 396

5.6 GROUPED ELEMENTS
This element provides protection against energization while the generator is at standstill or reduced speed. The feature is
armed using either the AND or OR combination of the undervoltage and machine off-line conditions, selected with the
ACCDNT ENRG ARMING MODE
The machine off-line status is indicated by a dedicated FlexLogic operand. Once armed, the accidental energization feature
operates upon detecting an overcurrent condition in any of the stator phases.
This feature can also provide protection against poor synchronization.
• ACCDNT ENRG ARMING MODE: This setting specifies whether the feature gets armed by either of the undervoltage
or machine off-line conditions ("UV or Off-line" value), or by both the conditions ("UV and Off-line" value). In both
cases, the element is armed after 5 seconds of the appropriate condition and de-armed 250 ms after the arming condi-
tion (UV and/or Off-line) ceases.
The "UV or Off-line" selection shall be made when the VTs are on the power system side of the disconnecting device.
If this is the case, the measured voltages may be normal regardless of the status of the protected machine, thus the
need for an OR condition. The "UV or Off-line" value provides protection against poor synchronization. During normal
synchronization, there should be relatively low current measured. If however, synchronization is attempted when con-
ditions are not appropriate, a large current would be measured shortly after closing the breaker. Since this feature does
not de-arm immediately, but after a 250 ms time delay, this will result in operation under imprecise synchronization.
The
ACCDNT ENRG OC PICKUP
The "UV and Off-line" value shall be made when the VTs are on the generator side of the disconnecting device. If this
is the case, both the undervoltage and machine off-line conditions are required to indicate that the protected generator
is not energized.
• ACCDNT ENRG OC PICKUP: This setting specifies the current level required to operate the armed Accidental Energi-
zation element. If any of the phase current is above the
• ACCDNT ENRG UV PICKUP: This setting specifies the voltage level required to arm the Accidental Energization ele-
5
ment. All of the line-to-line voltages must drop below the
age condition. The setting is entered in voltage pu values. As the element always responds to the line-to-line voltages,
care must be applied in picking up the value depending on the VT connection.
• ACCDNT ENRG OFFLINE: This setting specifies the FlexLogic™ operand indicating that the protected generator is
off-line.
5-236
setting (see below). The undervoltage condition is determined from the measured voltages.
setting can control the required precision of synchronization.
Figure 5–124: ACCIDENTAL ENERGIZATION SCHEME LOGIC
G60 Generator Protection System
level, the feature operates.
ACCDNT ENRG OC PICKUP
level in order to detect the undervolt-
ACCDNT ENRG UV PICKUP
5 SETTINGS
GE Multilin