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The DFF includes self-checking and auto-diagnosis.
These tests are performed during the power-up process of the relay and during normal operation. They check the
status of the power supply, ROM memory, RAM memory, oscillography memory and the EEPROM memory.
In case of an internal failure these functions detect the failure, disable the operation of the protection functions and
warn the user by operating the ALARM contact (terminals C9-D9).
2.3 ANALYSIS FUNCTIONS
The DFF relay has a circular log of the latest 144 events. Each event stores the following information:
•
Date and time (1 msec resolution)
•
Type of event
•
Voltage
•
Frequency
•
dF/dT measurement
•
Status of all internal digital signals (trips, pickups, inputs, outputs, etc.).
The events are stored in non-volatile EEPROM memory.
There are two types of record selectable by the OSCILLO TYPE setting: NORMAL or FREQ.
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:
• Waveforms of instantaneous samples of AC voltage inputs (V
• Frequency value at instant of trigger.
• Digital channels indicating status of protection functions.
• Date and time.
• Trigger source.
• Active settings.
12
OPERATING PRINCIPLES
DFF Digital Feeder Relay
2.2.3 SELF-CHECKING AND DIAGNOSIS
2.3.1 EVENT LOGS
2.3.2 OSCILLOGRAPHY
, V
, V
V
):
A
B
C,
N
GEK-106166E
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