Both the low-set overcurrent and earth-fault elements can be independently
configured to have following IDMT characteristic curves :-
• Normal inverse
• Very inverse
• Extremely inverse
• Long-time inverse
The relationship between current and time for the above curves comply with the
standard IEC255-4 and may generally be expressed as :
___kβ__
( I/I>)
α
-1
Where t = operating time in seconds
k = time multiplier
I = measured current
I> = set current
α = constant
β = constant
Both the high-set overcurrent and high-set earth-fault elements are
independently configured with definite time delay only. The time delay can be
from 0.05 sec (instantaneous) to 300 sec. The high-set feature can also be
disabled by the user.
MK2000
Page 13
3. Characteristic Curves
Characteristic curveCharacteristic curve
α β
Normal Inverse 0.02 0.14
Very Inverse 1.0 13.5
Extremely Inverse 2.0 80.0
Long-time Inverse 1.0 120.0
t =
To Next Page
Loading...
