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PR512/P (50-51-50N-51N) UNIT
Protection against instantaneous or
delayed earth fault (50N)
This function makes a family of definite adjustable
time curves available, indicated by the symbol
Io>>.
The corresponding trip time is indicated by the
symbol to>>.
Start of timing is signalled by the ALARM LED
lighting up, whereas circuit-breaker opening is
signalled on the front by the magnetic flag Io>
Io>>, turned to the yellow position. To reset
signalling, the FLAG RESET pushbutton on the
front of the release must be pressed, ensuring one
of the following conditions:
a) 24 Vdc auxiliary voltage present (display lit);
b) primary circulating current higher than 0.2 x In
c) application of the TT2 unit to the TEST connec-
Selection of Io>> threshold value
Setting the Io>> threshold is carried out by work-
ing on the Dip Switches as shown in the figure
below.
The sum of the values selected represents the
multiple of Io> and corresponds to threshold Io>>.
N.B. Even if protection Io> is OFF, the first Dip Switch
takes on the value 0.1.
Also remember that the Io>> function with internal
toroid is disabled when the fault current exceeds 3
x In, regardless of the value set for the threshold.
With an external toroid no disablement is fore-
seen.
18
(display lit with indication of the circulating
current);
tor on the front of the release (optional acces-
sory).
The following settings are possible:
• 16 threshold current values (Io>>)
2.5
3.5
4.5
5.5
8.5
9.5
10.5
12
14
15
17
18
20
OFF
5
6
Caption
5 Dip Switch for setting the trip threshold of protection
Io>>.
6 Dip Switch for setting trip time to>> of protection Io>>
Selection of to>> trip time
The function of protection Io>> has a single
definite time curve adjustable to 31 values. The
values available are between 0.05 s and 1.55 s
with steps of 0.05 s.
The following settings are possible:
• 31 trip times (to>>),
(0.05...1.55 with steps of 0.05)
0.05
0.10
0.15
0.20
0.30
0.35
0.40
0.45
0.55
0.60
0.65
0.70
0.80
0.85
0.90
0.95
1.05
1.10
1.15
1.20
1.30
1.35
1.40
1.45
7.5
13
19
x Io>
0.25
0.50
0.75
1.00
1.25
1.50
1.55 s
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