I-Gard MGFR Series, Инструкция по эксплуатации

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2.7 BUTTON FUNCTIONS
2.7.1 SET FLASHING LEVEL AND FAULT CURRENT DISPLAY
Fault current display feature is common to all models of the MGFR series. After a relay has tripped due to a
ground fault, it keeps the last fault current value in internal memory. To see this value, in per unit, press the
uppermost momentary pushbutton on the faceplate and release immediately. The same operation will reset the
trip indicator, if it is on after a fault. When a relay is first energized, pressing the switch will show ‘0.00’.
The last fault value will stay always in the memory unless one of the following events occurs:
a) When the relay trips on a future fault, the previous value will be erased and the new value will be stored
in the memory.
b) If the control power is interrupted, for any reason after a fault has occurred (especially when MGFR-SE-
ZB is connected to the load side of the breaker).
c) When the preventive watchdog circuit inside the relay resets the microprocessor after detecting any
temporary problem, the memory will reset to ‘0.00’. This will also reset the trip indicator.
Since some of the models in the MGFR series can be used in resistance-grounded systems, monitoring a slow
developing fault from the LED display can be a useful feature. The display will start flashing, showing the fault
current, to attract the attention of operating personnel. It will keep on flashing until the relay trips itself or the
fault is cleared by a downstream relay.
The relay will start flashing when initialized at 50% of pick-up for a developing fault. However, this value is
user-programmable by the same pushbutton. The values of fault current at which the flashing can start to
occur are 0.16, 0.25, 0.75 and 0.90 of pick-up. After pressing and releasing the switch for the first time, the last
fault current value will appear on the display. Pressing the switch again after an interval of 1-1.5 seconds and
releasing it will cause the numbers ‘0.16’, ‘0.25’, ‘0.50’, ‘0.60’, ‘0.75’, ‘0.90’ to scroll through the display. When
the relay is first energized, the default setting ‘0.50’ will blink a few times to indicate that 0.50 is the preset
flash setting. In other words, the display will start flashing when the fault current is greater than or equal to
50% of pick-up. If the switch is pressed again and released when any of the values are shown on the display,
the relay will accept it as the new flash setting and will start flashing when the fault current exceeds that value.
The setting can be checked by repeating the operation but without pressing the button for the third time. While
doing so, the value at which the flashing has been set will blink when it appears on the display. The setting will
remain in the memory unless it is changed by the user or the power is interrupted, as explained in b) earlier in
this section. The relay will always flash above pick-up until it trips.
Selection of different flash settings is dependent on the two following conditions:
a) When there is no fault and the display is showing ‘0.00’.
b) When there is a developing fault in the system, but it is below pick-up level.
A sustained fault above pick-up level overrides the above operation and pressing the pushbutton will do nothing
until the fault clears, or falls below the pick-up level.