Frequency Out-Of-Band Accumulation - GE G60 Instruction Manual

CHAPTER 5: SETTINGS

5.8.8 Frequency out-of-band accumulation

5.8.8.1 Menu
SETTINGS  CONTROL ELEMENTS  FREQUENCY OOB ACCUMULATION
 FREQUENCY OOB
 ACCUMULATION
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 passes through operating
frequencies 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 provides diagnostic information and alarms based on the accumulated off-nominal frequency operation time
of a turbine over several frequency bands, that can then be used to schedule maintenance or other action.
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 wanted. For example, accumulation
can be blocked during an out-of-service condition as set via an input to the relay.
Settings are described as follows and apply to all accumulators.
— Selects the source for the signal to be measured. The element first checks for a live phase
FREQ OOB ACCUM SOURCE
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 does not operate, as it does not measure a parameter below the
minimum voltage/current setting.
FREQ OOB ACCUM MIN VOLT/AMP
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.
— This setting selects a FlexLogic operand to block out-of-band frequency accumulation in all bands.
FREQ ACCUM BLOCK
This is typically required to avoid unnecessary accumulation when relay testing is being performed.
5.8.8.2 Accumulators 1 to 7
SETTINGS  CONTROL ELEMENTS  FREQUENCY OOB ACCUMULATION  FREQUENCY OOB ACCUMULATOR 1(7)
 FREQUENCY OOB
 ACCUMULATOR 1
G60 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
FREQ OOB ACCUM

SOURCE: SRC 1
FREQ OOB ACCUM MIN

VOLT/AMP: 0.10 pu
FREQ ACCUM BLOCK:

Off
FREQ OOB ACCUM

TARGET: Self-reset
FREQ OOB ACCUM

EVENTS: Disabled
 FREQUENCY OOB

 ACCUMULATOR 1

 FREQUENCY OOB

 ACCUMULATOR 7
— This setting specifies the minimum per-unit positive-sequence voltage or current level
FREQ ACCUM 1

FUNCTION: Disabled
FREQ ACCUM 1 UPPER

FREQ 60.00 Hz
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 below
Range: Enabled, Disabled
Range: 20.00 to 70.00 Hz in steps of 0.01
CONTROL ELEMENTS
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