DSEGenset DSE8610, Operator'S Manual

Page: 99 / 118

Protections
99
8.8 SHORT CIRCUIT AND EARTH FAULT 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.
Short Circuit alarm operates in the same way as the Earth Fault, using the same curve formula, but
typically uses a lower value for K (time multiplier) to give a faster acting trip.
If the A larm is enabled, the DSE8610 Series controller begins following the IDMT ‘curve’. If the current
surpasses the Trip for an excess of time, the Alarm triggers ( Shutdown or Electric trip as selected in
Action ).
The higher the 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
Is 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
value)
K (time multiplier setting)
K (time multiplier setting)
I
S
(Trip setting
value)