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Edit Configuration
47
Overcurrent Alarm
The overcurrent alarm combines a simple warning trip level combined with a fully functioning IDMT curve for
thermal protection.
Immediate warning
IEEE 37.2 -50 instantaneous overcurrent relay
If the current exceeds the
Trip
level the
Immediate Warning
activates.
IDMT Alarm
IEEE 37.2 -51 AC time overcurrent relay (shutdown / electrical trip)
If the
IDMT Alarm
is enabled, the DSE controller begins following the IDMT ‘curve’. If the
Trip
is surpassed for
an excess amount of time the
IDMT Alarm
triggers (
Shutdown
or
Electric trip
as selected in
Action
).
The higher the overload, the faster the trip. The speed of the trip is dependent upon the fixed formula:
T = t / ((IA / 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).
Typical settings for the
IDMT Alarm
when used on a brushless alternator are:
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.
See overleaf for details of the IDMT alarm factory settings and examples of different settings for the
Time
Multiplier (t)
.
The IDMT alarm factory settings, allows for overload of the set to the limits of the
Typical Brushless Alternator
whereby 110% overload is permitted for 1 hour.
If the set load is reduced, the controller then
follows
a cooling curve. This means that a second overload
condition may trip much sooner than the first as the controller
knows
if the windings have not cooled
sufficiently.
For further details on the
Thermal damage curve
of your alternator, you are referred to your alternator
manufacturer.
I
T (Trip setting value)
t
(time multiplier)
Содержание DSE8810
Страница 117: ...Edit Configuration 117 Actions Drive a PLC function Write a value to a Gencomm register Reset an alarm ...
Страница 126: ...Scada 126 5 8 2 POWER Shows the module measurements of the supply power ...
Страница 134: ...Scada 134 5 12 STATUS Shows the module s current status ...
Страница 144: ...Scada 144 5 19 COMMUNICATIONS INFORMATION Shows the module s communication ports settings ...
Страница 146: ...Scada 146 5 20 1 DATA LOG STATUS Shows the memory status of the data log allocated space ...
Страница 148: ...This Page Is Intentionally Left Blank 148 ...