Liebert EXL S1 Installation
User Manual 10H52226UM60 - Rev. 1 - 01/2017
45
3.4.2. Primary line power input
The
se should be capable of protecting the primary AC line power ahead of the UPS. It should be able
to handle the maximum input current of the UPS (Table 1 on page 38) and to interrupt the circuit at
its maximum current level during
a short circuit.
3.4.3. Bypass line power input
Bypass line power input protection devices must have the following characteristics:
1 Maximum current rate
d in accordance with the values in Table 1 on page 38;
2I
2
t
rating lower than the thyristor rating (see chap. 9. on page 102 for pre-arc I
2
t ratings) in
order
to protect it in case of output short circuit. To allow for component tolerances, the external
protection device pre-arc I
2
t rating should not exceed 80% of the thyristor I
2
t rating;
3 Pre-arc I
2
t rating higher than that of the Inverter fuse (already installed inside the UPS - see chap.
9.
o
n page 102 for pre-arc I
2
t ratings) so that the Inverter fuse will blow in case of an overcurrent
caused by an internal failure. In this case the load is supplied by the Bypass - to allow for
component tolerances, the external protection device pre-arc I
2
t rating should be at least 20%
higher than that of the Inverter fuse.
3.4.4. Battery input
These should be capabl
e of protecting the battery against short-circuits, and should take into account
the maximum current drain (during discharge at 1.8V per cell), see Table 1 on page 38. These devices
should be installed as close as possible to the battery.
3.4.5. UPS Output line
Since load(s) can be supplie
d through the Uninterruptible Power System from two sources, the ratings
of the following supplies should be taken into account when designing the output line protection
s
ystem.
Supply from inverter:
see Table 1 on page 38 and chap. 9. on page 102
Supply from Static Bypass Switch and maintenance Static Bypass Switch:
see Table 1 on page 38 and chap. 9. on page 102
N.B.
If a single differential breaker is installed ahead of the UPS, any fault in the installation
grounding system will result in the interruption of power to both the line power input and the direct
line.
3.5. Backfeed protection
To prevent electric
shock hazards caused by backfeed through the Static Bypass Switch, an external
disconnector must be installed in conformance with Product Standard IEC/EN 62040-1+A1:2013. The
UPS generates a logic command at
X29 (see Fig. 40) to ensure that the disconnector operates
correctly.
N.B.
In case of single-line feeder, the disconnector must be installed ahead of the UPS primary and
bypass inputs. When this disconnector is activated, the UPS switches to Battery Mode.
N.B. The PE and N terminals must be connected in ac
cordance with the requirements of the local
line power distribution system (TN-C, TN-S, TN-C-S, TT etc.). For instance, in
T
N-C installations the PEN conductor from the supply transformer must be connected to the UPS PE
and N terminals. See para. 3.6 on page 46 and Fig. 50 on page 91.
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