ABB REU 523 - Page 53

1MRS 750942-MUM
Combined Overvoltage and Undervoltage Relay
Technical Reference Manual
REU 523
53
Auxiliary voltage
The REU 523 requires a secured auxiliary voltage supply to operate. The internal
power supply of the relay forms the voltages required by the relay electronics. The
power supply is a galvanically isolated (flyback-type) DC/DC converter. When the
auxiliary voltage is connected, the READY indicator LED on the front panel will be
on. For detailed information on power supply, refer to table 4.2.3-2.
The primary side of the power supply is protected with a fuse located on the PCB of
the relay. The fuse size is 3.15 A (slow).
Table 4.2.3-12 Data communication
Rear interface, connector X2.2
• RS-485 connection for the fibre-optic interface module RER 103
• SPA-bus or IEC 60870-5-103 protocol
• 4.8 or 9.6 kbps
Front interface
• Optical RS-232 connection for the opto-cable
• SPA bus protocol
• 4.8 or 9.6 kbps