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GEK – 106166B
2.3.3 SELF-CHECKING AND DIAGNOSIS
The DFF includes (due to its numerical technology) self-checking and autodiagnosis. These functions guarantee
proper operation, signalization in case of internal failure and disable the operation of the protection functions.
These tests are performed not only during the power-up process of the relay but also during normal operation
(making use of the so called "background free time"). They check the situation of the power supply, ROM memory,
RAM memory, oscillography memory and the EEPROM memory.
Additionally a hardware check for the signalling LEDs is incorporated. By pressing the TARGET RESET button all
of them will be lit up.
2.4 ANALYSIS FUNCTIONS
2.4.1 EVENT REGISTER
The DFF relay has a cyclic register of the last 144 events, each event stores the following information: date and
time (1 msec time tag), type of event, the voltage, frequency, and dF/dT measurement values at the time event
happened and equipment status.
The events are stored in non-volatile EEPROM memory (the events are maintained even in the case of power
supply loss).
The generated events are associated with the internal states of protection and communications.
2.4.2 OSCILLOGRAPHY REGISTER.
There are two types of oscillos, selectable by the OSCILLO TYPE setting, between NORMAL or FREC.
NORMAL Type
The DFF unit can store up to 4 oscillography records, with a resolution of 16 samples per cycle. Each record has a
maximum capacity of 99 cycles, and the number of pre-fault cycles is selectable between 2 and 10. Each record
includes the following information:
• Instantaneous values of voltage inputs (V
, V
, V
V
):
A
B
C,
N
• Frequency value
• Digital information (status of protection functions).
• Date and time
• Causes for the oscillography record.
• Active settings table in the moment of the record.
FREC Type
The DFF unit stores up to 4 oscillography records, with a resolution of 2 samples per cycle. Each record has a
maximum capacity of 1584 cycles, and the number of pre-fault cycles is selectable between 2 and 80. Each
record includes the following information:
• Frequency value
• Digital information (status of protection functions).
• Date and time.
• Causes for the oscillography record.
• Active settings table in the moment of the record.
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