L3447
Emax DC
53/108
Model
Scale
Page No.
Doc. No.
Apparatus
1SDH000635R0002
L3728
13.2.9.6
Protection “G”
This protection can be disabled; it can be of the fixed time (t=k) or inverse time (t=k/i
2
) type. In the latter case, the trip time is given by the expression
÷
÷
ø
ö
ç
ç
è
æ
,
2
I
2
max
t
4
where I=I
f
/I
4
, I
f
is the fault current and I
4
is the protection threshold.
NB: Time expressed in seconds.
It is possible to disable the trip control of the protection ("Enable Trip: Off").
For the whole duration of the earth fault, circuit-breaker opening does not take place, but only the alarm condition is signaled
("Alarm" LED lit and alarm message).
This is provided inside the release by calculating the vectorial sum of the currents of the two polarities. The fault current is defined by the following
formula:
In the case when the circuit does not show any fault, the module of the sum of these currents is always nil; vice versa the value of the fault current
will take on an increasingly large value depending on the size of the fault. This operating mode is enabled by default.
13.2.9.6.1 Start-up threshold “G”
The start-up function can be selected in the case where the curve with fixed time is selected.
The function can be enabled and disabled on the protection "G" page.
The function behaves in exactly the same way as the protection "S" (see par. 13.2.9.2.2).
13.2.9.6.2 Zone selectivity “G”
The zone selectivity function can be enabled providing the fixed time curve, and the function is assured only if auxiliary voltage is provided.
Zone selectivity "G" can be active at the same time as zone selectivity "S".
The behavior and wiring of the function are identical to those indicated for zone selectivity "S" (see par. 13.2.9.2.3).
13.2.9.7
Protection against unbalance “U”
The protection with fixed time, which can be excluded, trips in the case when, for a time greater than or the same as the time
t6
set, an unbalance
is determined between two or more polarity higher than the set threshold
I6
. Range: 2 … 90% by 1% steps.
The percentage of unbalance is therefore calculated
%Unb
100
max
min
max
⋅
−
=
I
I
I
where I
max
is the maximum and I
min
is the minimum polarity current.
It is possible to disable the trip control of the protection ("Enable Trip: Off").
In that case, for the whole duration of the unbalance the CB will not be opened, but only the condition will be
signaled by means of the "warning" LED lit up and a warning message.
When the value of the polarity current is above 6xIn, the function "U" excludes itself because, in this case, the other protections
intervene because the fault is considered as a polarity fault.
The protection is not enabled for maximum polarity current values lower than 0.3xIn.
13.2.9.8
Protection against overtemperature inside the relay “OT”
There is a sensor inside the PR123/DC unit that monitors the temperature of the unit.
This enables the signalling of any abnormal temperature conditions, which could cause temporary or continuous malfunctions of the unit's electronic
components.
This protection has two states of operation:
State of
“WARNING TEMPERATURE”
with
–25°C < temp. < -20°C
or
70°C < temp. < 85°C
: the display is turned off and
the "WARNING" LED flashes at 0.5Hz.
State of
“ALARM TEMPERATURE”
with
temp. < –25°C
or
temp. > 85°C
: the display is turned off,
the "WARNING" and “ALARM” leds flash at 2Hz and Trip is activated (if enabled by means of the "Over Temper. Trip = On" parameter).
N.B.:
In the event of Warning and Alarm, the display is momentarily turned off, to preserve its functionality.
The monitored temperature is not visible on the display.
The protection is always active, both with auxiliary supply and in self-powering.
Disabling the Trip control of the protection means that the PR123/DC unit could work, with the circuit-breaker closed, in a
range of temperatures where correct operation of the electronics is not guaranteed.
A
B