L2275
Emax UL
66/132
Doc. N°
Mod.
RH0109002
Apparatus
Scale
Page N°
(
)
In
s
In
I
I
t
f
12
I
per
0.75
,
12
I
per
75
0.
,
9
max
f
2
1
1
f
>
≤
⋅
I
t h
15.2.6.1
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 protection trip time - inverse time - is given by the expression
where
I
f
is the fault current and
I
1
the protection threshold.
NB: Time expressed in seconds.
15.2.6.1.1 Thermal memory “L”
It is possible to enable the function of thermal memory for cable protection. This is based on the “
τ
L” parameter defined as the trip time of curve
(t1) selected at 1.25xI1.
The trip unit trip time is certainly 100% of the one selected after which a time of 3x
τ
L has passed since the last overload or since the last trip. Otherwise
the trip time will be reduced depending on the overload which has occurred and on the time passed.
The PR113 is fitted with two instruments to make up this thermal memory. The first only works when the trip unit is supplied (it remembers
overloads which did not last long enough to make the trip unit trip), whereas the second only works when the trip unit is not supplied (it reduces
any trip times in the case of immediate reclosing).
The PR113 trip unit automatically decides which of the two to use according to the various situations.
15.2.6.2
Protection “S”
This protection, which can be disabled, can be with fixed time ( t = k ) or inverse time. In the latter case, the trip time is given by the expression
NB: Time expressed in seconds.
15.2.6.2.1 Thermal memory “S”
It is possible to enable the thermal memory function for cable protection in the case where the curve with inverse time is selected: This is based
on the “tS” parameter defined as the trip time of the curve (t2) selected at 1.5xI2. The other characteristics are the same as those for thermal memory
“L” (see par.15.2.6.1.1).
15.2.6.2.2 Start-up threshold “S”
It is possible to select the start-up function in the case where the curve with fixed time is selected.
The function is disabled by selecting [-----] at the “StartUp” parameter on the protection “S” page.
The time the start-up threshold is valid for depends on what is set for the “ts” parameter on the page for general enabling of the START-UP function
(see par.15.4.2.2). If the function is placed on [Off] here, the start-up threshold is disabled for all the protections.
The start-up function allows modification of the protection threshold (S, D, I and G) during a time interval lasting “ts”, starting from “start-up”. The
latter must be intended as follows:
– Turning on of the trip unit, under self-supply;
– Passage of the peak value of the maximum current over 0.1xIn. A new start-up is possible after the current has gone down below 0.1xIn.
•
Start-up time
The start-up time is common to all the protections involved.
Range: 0.1 s … 1.5 s, with steps of 0.05 s.
Tolerance : ± 20%.
15.2.6.2.3 Zone selectivity “S”
It is possible to enable the zone selectivity function in the case where the curve with fixed time is selected and there is an auxiliary power supply.
This carried out by connecting all the zone selectivity outputs to one another (ZSO=K51/SZout) of the trip units belonging to the same zone and
taking this signal to the zone selectivity input (ZSI=K51/SZin) of the trip unit immediately on the supply side. If the cabling operation has been carried
out correctly, all the zone selectivity inputs of the last power circuit breakers in the chain and all the outputs of the power circuit breakers at the
head of each chain must be empty.
Start Up Threshold I
2
Start Up
Time Programmed ts
Threshold I
2
where
I
f
is the fault current and
I
2
the protection threshold.
( )
2
2
2
,
100
max
t
I
t
f
⋅
2
I
I
f
>
for
