ABB REX 521 Technical Reference Manual, General

1MRS 751108-MUM
REX 521
29
Protection Relay
Technical Reference Manual, General
When the self-supervision detects a fault, different measures are taken depending on
the severity of the fault. If the fault is fatal, the microcontroller tries to get the system
to work by restarting ten times. If this attempt is not successful, a signal about the
internal relay fault (IRF) is linked to the output relay. Provided that the unit is
operating normally, the information about the fault is sent as an event
“IRF activated” (E31) over the serial communication and the green READY LED
on the front panel starts blinking. An indication about the character of the fault is
also shown as a textual message on the display.
If the fault is considered too dangerous to maintain normal protection, an inoperative
IRF state is entered and no output relay operations are allowed. On the other hand
if, for example, one output relay is found faulty and the others healthy, normal
operations targeted to a healthy relay are allowed.
Even a total breakdown of the relay, for example, on loss of power supply, will be
detected as the IRF relay operates in a fail-safe mode, causing a signal when the
relay drops off. The serial communication will also indicate loss of contact to the
module. When the relay is in the IRF state, it tries to recover by restarting every five
minutes.
As long as the fault remains, the relay continues to perform internal tests. Should the
fault prove to be of temporary nature, normal operation is recovered after restart and
an event “IRF reset” (E30) is sent over the serial communication.
4.1.11.1. Fault indication
The self-supervision signal output operates on the closed circuit principle. Under
normal conditions the output relay is energized and the contact gap 3-5 is closed.
Should the auxiliary power supply fail or an internal fault be detected, the contact
gap 3-5 is opened.
Table 4.1.11-1 Self-supervision functions
Supervised object Supervision method Execution frequency
RAM memories Write and read of all memory
locations
40 B / 200 ms
Nonvolatile memories Checksum When data is fetched
Microcontroller and program
execution
Internal watchdog 100 ms
A/D converter, multiplexer and
amplifiers
Reference voltage 1 min
Setting values Checksum, correct values 1 min
HMI (display) Visual inspection On connection of supply
voltage
Power supply module Measurement of supply
voltages
1 min
Output amplifiers and relay
coils
Feedback from the relay coils 1 min

ABB REX 521 Specifications

General

Brand	ABB
Model	REX 521
Category	Other
Language	English