GE G30 Instruction Manual page 412

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 offline conditions, selected with the
ACCDNT ENRG ARMING MODE
The machine offline 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
machine offline conditions ("UV or Offline" value), or by both the conditions ("UV and Offline" value). In both cases, the
element is armed after five seconds of the appropriate condition and de-armed 250 ms after the arming condition (UV
and/or Offline) ceases.
Select "UV or Offline" when the VTs are on the power system side of the disconnecting device. If this is the case, the
measured voltages can be normal regardless of the status of the protected machine, thus the need for an OR condition.
The "UV or Offline" value provides protection against poor synchronization. During normal synchronization, there should be
relatively low current measured. If however, synchronization is attempted when conditions are not appropriate, a large
current is measured shortly after closing the breaker. Since this feature does not de-arm immediately, but after a 250 ms
time delay, this results in operation under imprecise synchronization. The
required precision of synchronization.
Select the "UV and Offline" value when the VTs are on the generator side of the disconnecting device. If this is the case,
both the undervoltage and machine offline conditions are required to indicate that the protected generator is not
energized.
ACCDNT ENRG OC PICKUP
element. If any of the phase current is above the
ACCDNT ENRG UV PICKUP
5
of the line-to-line voltages must drop below the
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
5-238
setting (see below). The undervoltage condition is determined from the measured voltages.
— This setting specifies whether the feature gets armed by either of the undervoltage or
— This setting specifies the current level required to operate the armed Accidental Energization
ACCDNT ENRG OC PICKUP
— This setting specifies the voltage level required to arm the Accidental Energization element. All
ACCDNT ENRG UV PICKUP
— This setting specifies the FlexLogic operand indicating that the protected generator is offline.
Figure 5-130: Accidental energization logic
ACCDNT ENRG OC PICKUP
level, the feature operates.
level in order to detect the undervoltage
G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
setting can control the