L2275
Emax UL
29/132
Doc. N°
Mod.
RH0109002
Apparatus
Scale
Page N°
RMS and Peak calculation
The protection allows the current signal to be processed in the following way:
•
with rms value up to a current of 2xIn and with a peak factor
≤
3 for protection function “L”
•
with peak value for currents
≥
2xIn and for protection functions “S”,”I” and “Iinst” (*).
•
with mean value for ground fault protection function “G”.
If the waveform has a deformation above the declared limit (2.1 @ 2.8 In), the calculation tolerance of the true rms value will increase.
(*) Processing is carried out taking into account the peak value divided
2
(the sinusoidal wave form is therefore considered). This is because of incompatibility between
the trip time and the rms value calculation time.
12.4.1
Protection “L”
Protection “L” is the only one which cannot be disabled since it carries out self-protection against overloads of the trip unit itself.
The type of curve settable is t=k/I
2
.
The trip time of the protection, inverse time, is given by the following expression:
(
)
In
I
per
0.75
,
In
I
per
0.
I
I
t
f
f
f
12
12
75
,
36
max
2
1
1
>
≤
⋅
I
f
is the fault current and
I
1
is the protection threshold, set by the user.
NB: Time expressed in seconds.
12.4.2
Protection “S”
The protection, which can be disabled, can either be with fixed time (t=k) or inverse time (t=k/I2). In the latter case the trip time is given
by the expression
( )
2
2
2
2
,
64
max
I
I
per
t
I
t
f
f
>
⋅
I
f
is the fault current and
I
2
the protection threshold, set by the user.
NB: Time expressed in seconds.
12.4.3
Protection “I”
The protection, which can be disabled, with fixed time (t=k) is carried out with nil intentional delay.
12.4.4
Protection “G”
The protection, which can be disabled, is of the inverse time type (t=k/I
2
).
The trip time is given by the expression
(
)
4
2
4
,
6
,
0
max
t
I
I
f
I
f
is the fault current and
I
4
the protection threshold, set by the user.
NB: Time expressed in seconds.
The PR111 unit is able to provide ground fault protection, carried out inside the trip unit, vectorially summing the phase and neutral currents. The
fault current is defined by the following formula
NE
G
I
I
I
I
I
+
+
+
=
3
2
1
.
In the case when there is no fault in the circuit, the module of the sum of these currents is always nil. Vice versa, the value of the fault current will
always take on a higher value depending on the size of the fault.
When the value of the phase current is above 4xIn, function “G” excludes itself since, in this case, there are other protections which
intervene as the fault is considered to be a phase fault.
12.4.5
Protection against “Iinst” instantaneous short circuit
This function has a single protection curve with fixed time.
When the protection trips, the power circuit breaker opens by means of the opening solenoid (SA).
