Frequency Out-Of-Band Accumulation - GE G30 Instruction Manual

5.7 CONTROL ELEMENTS
a) GENERAL SETTINGS

PATH: SETTINGS CONTROL ELEMENTS
 FREQUENCY OOB
 ACCUMULATION
5
The turbine portion of a generator is designed to operate in a narrow frequency range around the nominal, typically ±5%.
As the turbine overspeeds (typically due to load rejection) or coasts down, the turbine will pass through operating frequen-
cies where the turbine blades find stimulus at their natural frequencies. Blade vibrations at these natural frequencies result
is stress on the blades that is accumulated and can result in cracking in some parts of the blade structure, most likely the tie
wires or blade covers. Though typically not catastrophic, the stress can change the vibration behavior of the blade so that
they can have natural resonances closer to the normal operating frequency. This element will provide diagnostic informa-
tion and alarms to the customer based on the accumulated off-nominal frequency operation time of a turbine over several
frequency bands and can then be used to schedule maintenance or other actions as desired by the customer.
The available setting of an upper and lower frequency for each band enables the user to overlap bands of frequencies in
the accumulation function. The accumulation function in any band can be blocked as desired. For example, accumulation
may be blocked during an out-of-service condition as set via an input to the relay.
The following settings are available and apply to all accumulators.
• FREQ OOB ACCUM SOURCE: This setting selects the source for the signal to be measured. The element first checks
for a live phase voltage available from the selected source. If voltage is not available, the element attempts to use a
phase current. If neither voltage nor current is available, the element will not operate, as it will not measure a parame-
ter below the minimum voltage/current setting.
• FREQ OOB ACCUM MIN VOLT/AMP: This setting specifies the minimum per-unit positive-sequence voltage or cur-
rent level required to allow the frequency out-of-band accumulators to operate. This threshold is used to prevent an
incorrect accumulation when operating quantity is too low.
• FREQ ACCUM BLOCK: This setting selects a FlexLogic operand to block out-of-band frequency accumulation in all
bands. This is typically required to avoid unnecessary accumulation when relay testing is being performed.
5-208

FREQUENCY OOB ACCUMULATION
FREQ OOB ACCUM
SOURCE: SRC 1
FREQ OOB ACCUM MIN
MESSAGE
VOLT/AMP: 0.10 pu
FREQ ACCUM BLOCK:
MESSAGE
Off
FREQ OOB ACCUM
MESSAGE
TARGET: Self-reset
FREQ OOB ACCUM
MESSAGE
EVENTS: Disabled
 FREQUENCY OOB
MESSAGE
 ACCUMULATOR 1
 FREQUENCY OOB
MESSAGE
 ACCUMULATOR 2
 FREQUENCY OOB
MESSAGE
 ACCUMULATOR 7
G30 Generator Protection System

5.7.8 FREQUENCY OUT-OF-BAND ACCUMULATION

Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 0.10 to 1.25 pu in steps of 0.01
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Enabled, Disabled
See following section.
See following section.
↓
See following section.
5 SETTINGS
GE Multilin