GE DBF, Instructions Manual

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2. OPERATION LOGIC
10 DBF Breaker Failure Protection GEK-106168E
2.2.5 BUILT-IN SELF-CHECKING UNIT
The digital technology of the DBF system allows providing a built-in self-checking function which guarantees the
correct performance of the unit, and provides an external alarm in case of error detection.
Two built-in self-checking functions are performed, one when the unit is started up and the other during normal
operation. Internal tests are provided for power supply, program memory (ROM), working memory (RAM),
oscillography memory (RAM), and settings and calibration memory (EEPROM).
In addition, there is a hardware test for the Target LEDs, which lights them all up when the button TARGET
RESET is pressed. The sealed-in targets (latched) reset if the TARGET RESET button is kept pressed during
three seconds.
2.3. ANALYSIS FUNCTIONS.
The DBF system includes an event recorder and an oscillography waveform recorder with a resolution of 1 ms for
the first one, and 1 sample for the second one (1.04 ms at 60 Hz and 1.25 ms at 50 Hz). To avoid the loss of
date/time and oscillography records during any Vdc power failure, the unit is equipped with a capacitor, which
allows the information to be kept for at least 24 hours after power loss.
2.3.1 EVENT RECORDER.
The DBF system keeps a record of the last 144 events and stores for each one the following information: date and
time (accurate to one millisecond), the type of event, current RMS values during the event, and the state of the
unit (set of digital signals that describes the status of the relay at any given moment in time).
This event recorder is stored in a non-volatile memory and can be maintained indefinitely, even with no power
supply.
The list of events that the relay stores are factory fixed, and corresponds to standard relevant
situations/operations, like Settings Change, Program initiate, Active Table 1, Opening 52 phase C, Closing
52 phase C, Digital Input 1 Activated, etc.
2.3.1 OSCILLOGRAPHY
The DBF unit stores up to 4 oscillography records, with a resolution of 16 samples per cycle. Each record has a
maximum capacity of 66 cycles. The number of pre-fault cycles can be selected from 2 to 10 cycles. Each record
includes the following information:
•
Date and time.
•
Name of the signal that triggered the oscillography.
•
Active settings table when recording
•
Digital information (Status of internal digital signals)
•
Instantaneous rms values of currents (I
A
, I
B
, I
C
and I
N
)
A configurable mask is available for selecting which functions or internal signals are able to trigger the
oscillography. It can either be triggered by a configurable digital input, by a command received from the
communication program (GE_LOCAL), or directly from the HMI.