D-PRO Protection relay Technical Manual 37
•
4 = ANSI
– Very inverse (not implemented yet)
The 51V protection uses the parameters P.0357, P.0358 and P.0359 and it differs from the
“normal” 51 because the threshold set in P.0358 is automatically restrained when the genset
voltage decreases. In detail:
•
If the generator voltage is higher than 80% the rated, the current threshold remains
the one set.
•
If the generator voltage is less or equal to 20% of the rated, the current threshold
becomes 20% of the one set.
•
If the generator voltage is between 20% and 80% of the rated, the current threshold
is reduced in percentage.
SICES Curve
– Extremely inverse
Time-dependant current protection (it activates as much quickly as higher the current overload
is). The curve used is called
EXTREMELY INVERSE
with function
I
2
t
. It is a generator
protection as it limits the thermal accumulation of the generator during the supply phase. As
engine protection, you must use the maximum power one, which is independent from the load
type.
You have to define a maximum current value and a maximum time that the genset can manage
for this current. If the current is lower than the defined threshold, the protection does not
activate. If the current rises above the threshold, the protection activates with a time that is
inversely proportional to the overcurrent. In order to correctly set the thresholds, you need to
perform the following steps:
•
Define the system rated current
•
Set the maximum current threshold with the parameter P.0352 (or P.0355 or P.0358),
as a percentage of the rated current.
•
Set the intervention time in the parameter P.0353 (or P.0356 or P.0359): the protection
will trigger within time set if the current is constantly equal to the threshold set in
P.0352 (or P.0355 or P.0358) multiplied by
2
. It will trigger more quickly when the
current is higher, more slowly when the current is lower.
In order to calculate the intervention time for a preferred current, please use the following
formula:
Current threshold reduction
Genset voltage (% nom)
40%
Cu
rr
e
n
t t
h
re
sh
o
ld
20%
60%
80%
100%
120%
0%
0%
40%
20%
60%
80%
100%
120%
Summary of Contents for D-PRO
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