Protections
50
Part No. 057-129 DSE871x mono remote display ISSUE 2.1 21/09/2010 ADM
6.7 HIGH CURRENT SHUTDOWN / ELECTRICAL TRIP ALARM
The overcurrent alarm combines a simple warning trip level with a fully functioning IDMT curve for thermal
protection.
6.7.1 IMMEDIATE WARNING
If the Immediate Warning is enabled, the DSE87xx Series controller generates a warning alarm as soon as the Trip
level is reached. The alarm automatically resets once the generator loading current falls below the Trip level (unless
All Warnings are latched is enabled). For further advice, consult your generator supplier.
6.7.2 IDMT ALARM
If the IDMT Alarm is enabled, the DSE87xx Series controller begins following the IDMT ‘curve’ when the trip level is
passed.
If the Trip is surpassed for an excess amount of time the IDMT Alarm triggers (Shutdown or Electric trip as selected
in Action).
High current shutdown is a latching alarm and stops the Generator.
Remove the fault then press Stop/Reset
to reset the module.
High current electrical trip is a latching alarm and removes the generator from the load, before stopping the
Generator after the off load cooling timer.
Remove the fault then press Stop/Reset
to reset the module.
The higher the overload, the faster the trip. The speed of the trip is dependent upon the fixed formula:
T = t / ( ( I
A
/ I
T
) – 1 )
2
Where:
T is the tripping time in seconds
I
A
is the actual current of the most highly loaded line (L1 or L2 or L3)
I
T
is the delayed over-current trip point
t is the time multiplier setting and also represents the tripping time in seconds at twice full load (when I
A
/ I
T
= 2).
Factory settings for the IDMT Alarm when used on a brushless alternator are as follows (screen capture from the
DSE Configuration Suite PC software :
These settings provide for normal running of the generator up to 100% full load. If full load is surpassed, the
Immediate Warning alarm is triggered, the set continues to run.
The effect of an overload on the generator is that the alternator windings begin to overheat; the aim of the IDMT
alarm is to prevent the windings being overload (heated) too much. The amount of time that the set can be safely
overloaded is governed by how high the overload condition is.
I
T
(Trip setting
value)
t
(time
multiplier)
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