Riello MULTI SENTRY MST 80 - PROTECTION DEVICES; SHORT-CIRCUIT PROTECTION; PROTECTION AGAINST BACK-FEED; INPUT LINE THERMAL MAGNETIC SWITCHES

PROTECTION DEVICES
SHORT-CIRCUIT PROTECTION
In the presence of a fault on the load, the UPS limits the value and duration of the output current (short circuit current) for protection.
These values are also functions of unit status at the time of the fault. Two different cases can be distinguished:
 UPS in NORMAL OPERATION: load is switched instantly on the bypass line (UPS 60kVA I
2
t=25000A
2
s; UPS 80kVA
I
2
t=110000A
2
s; UPS 100kVA I
2
t=145000A
2
s; UPS 125kVA I
2
t=145000A
2
s): the input line is connected to the output
without any internal protection (blocked after t>0.5s)
 UPS in BATTERY-LED OPERATION: The UPS protects itself by supplying a current of about 1.5 times the nominal
current in output for 0.5s, switching itself off after this amount of time
PROTECTION AGAINST BACK-FEED
The UPS is equipped with internal protection against backfeed via internal metal separation devices (Inverter contactor, see “UPS
block diagram").
INPUT LINE THERMAL MAGNETIC SWITCHES
Install a trip switch a with C (or D based on the type of load) trip curve on the power supply line upstream of the UPS, following
the information given in the table below:
Automatic external AC protections *
Mod. UPS
Network input
Separate bypass input
(optional for MST 60-80-100)
60kVA
100A
100A
80kVA
125A
125A
100kVA
160A
160A
125kVA
250A
250A
* In the case of non-linear loads, properly oversize neutral line N after on-site assessment
If the protection device upstream to the UPS interrupts the neutral conductor, all phase conductors must also be
interrupted at the same time (4-pole switch).
BATTERY LINE
Surge protector and a cut-off device must be provided on the UPS external battery line.
The size and type of fuses must be selected on the basis of the capacity of the installed battery box, referring to the table below.
External DC protections
Mod. UPS
Fuse type
Fuse size [ A ]
60kVA
gl / gG
2 x capacity in Ah of the battery up to max 150A
aR
2.5 x capacity in Ah of the battery up to max 150A
80kVA
gl / gG
2 x capacity in Ah of the battery up to max 200A
aR
2.5 x capacity in Ah of the battery up to max 200A
100kVA
gl / gG
2 x capacity in Ah of the battery up to max 250A
aR
2.5 x capacity in Ah of the battery up to max 250A
125kVA
gl / gG
2 x capacity in Ah of the battery
aR
2.5 x capacity in Ah of the battery
Example: the following fuses can be used with UPS 60kVA and 65Ah batteries: 125A (130A) gl/gG or 150A type aR
Ensure that the UPS has been fully switched off before handling the external UPS battery line switch/fuses