ABB REX 521 Technical Reference Manual, General

18
1MRS 751108-MUM
Protection Relay
Technical Reference Manual, General
REX 521
4.1.4. Auxiliary voltage
For its operation, the protection relay requires a secured auxiliary voltage supply.
The protection relay’s internal power supply module forms the voltages required by
the protection relay electronics. The power supply module is a galvanically isolated
(flyback-type) DC/DC converter. A green LED indicator on the front panel is lit
when the power supply module is in operation.
4.1.4.1. Power supply versions
There are two basic versions of power supply modules available for REX 521
protection relays: type PS_87H and type PS_87L.
The input voltage range of the power supply module is marked on the front panel of
the REX 521 unit. The power supply version is specified by a letter in the order
number of the protection relay (refer to section “Ordering information” on page 56).
The voltage range of the digital inputs is tied to the selected power supply. If a power
supply version with the higher rated input voltage is selected, the protection relays
will be delivered with digital inputs that also have the higher rated input voltage. The
digital input, DI9, on the CPU module has also lower rated input voltage.
The auxiliary voltages of power supply modules and the corresponding rated input
voltages of digital inputs are:
For further technical data of the power supply, see Table 4.2.1-2 on page 44.
4.1.4.2. Low auxiliary voltage indication
The relay is provided with a low auxiliary voltage indication feature. The power
supply module issues an internal alarm signal when a drop in the power supply
voltage is detected. The alarm signal is activated if the power supply voltage falls
about 10% below the lowest rated DC input voltage of the power supply module, see
the table below:
The indication of a low auxiliary voltage (ACFail) can be seen as an event via serial
communication.
Power supply module
Rated input voltage
of power supply
Rated input voltage
of digital inputs
PS_87H 110/120/220/240 V AC
or 110/125/220 V DC
DI1...DI8: 110/125/220 V DC
DI9: 24/48/60/110/125/220 V DC
PS_87L 24/48/60 V DC DI1...DI9: 24/48/60/110/125/220 V DC
Rated input voltage Low indication level
PS_87H
• Rated input voltage 110/125/ 220 V DC 99 V DC
• Rated input voltage 110/120/220/ 240 V AC 88 V AC
PS_87L
• Rated input voltage 24/48/60 V DC 21.6 V DC

ABB REX 521 Specifications

General

Brand	ABB
Model	REX 521
Category	Other
Language	English