Protections
90
7.8 EARTH FAULT SHUTDOWN / ELECTRICAL TRIP ALARM
When the module is suitably connected using the ‘Earth Fault CT’. The module measures Earth Fault
and can optionally be configured to generate an alarm condition (shutdown or electrical trip) when a
specified level is surpassed.
If the Earth Fault alarm is enabled, the controller begins following the IDMT ‘curve’. If the Trip is
surpassed for an excess amount of time the Alarm triggers (Shutdown or Electric trip as selected in
Action).
The higher the Earth Fault, the faster the trip. The speed of the trip is dependent upon the fixed
formula :
T = K x 0.14 / ((I / I
s
)
0.02
-1)
Where: T is the tripping time in seconds (accurate to +/- 5% or +/- 50ms (whichever is the greater)
K is the time multiplier setting
I is the actual earth current measured
I
s
is the trip setting value
The settings shown in the example above are a screen capture of the DSE factory settings, taken
from the DSE Configuration Suite software.
I
S
(Trip setting
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