ABB REX521BBHGLB01C｜Protection Relay｜

REX521BBHGLB01C

The relay is equipped with non-volatile memory to preserve critical configuration and operational information during auxiliary supply failures.

The memory technology provides:

No battery requirement
Long-term data retention
Lifetime service capability
Automatic data storage without manual commands

When a setting value is modified and transmitted to the relay, the updated value is automatically stored in the non-volatile memory immediately. No additional “Save” or “Store” command is required.

Data Stored in Non-Volatile Memory

The following important information is retained:

Stored Data Description
Setting values Protection parameters, control settings, and configuration values
Display state Last active display page and user interface status
Lockout state Protection lockout conditions and trip-related states
Recorded values Fault and operation records generated by protection functions
Last 50 events Event history including time and date information
2. Data Restoration After Auxiliary Supply Failure

When auxiliary power is restored after an interruption, the relay automatically recovers its previous operating status.

Restored information includes:

Previous LED alarm indications
Displayed text information
Event records
Fault records
Protection status information

This feature improves:

Post-fault analysis
Maintenance troubleshooting
System availability
Operational continuity
3. Recorded Values Storage

The REU615 stores important operational data from:

Protection starts
Protection trips
Alarm conditions
Other significant relay events

After an auxiliary power interruption, engineers can access recorded information through the relay HMI.

Available information includes:

Event timestamp
Fault occurrence time
Date information
Fault currents for the three latest recorded events

The data can be accessed through the Recorded Values section of the protection function block responsible for the indication.

4. Event Buffer Function

The relay maintains an internal event buffer that stores the latest 50 events before an auxiliary power failure.

Stored event information includes:

Event type
Event status
Date
Time stamp

After power restoration:

Previous events remain available
Time and date information are restored
Operators can review historical operating conditions through the HMI

This supports:

Fault investigation
Sequence-of-events analysis
Maintenance diagnostics
5. Real-Time Clock (RTC)

The REU615 contains an internal real-time clock (RTC) used for accurate event time stamping.

RTC Functions

The clock provides:

Accurate event recording
Fault sequence analysis
Time synchronization for protection operations
Historical event tracking

The RTC continues running during auxiliary supply interruptions.

RTC Backup Capability

The relay includes a capacitor-based backup system that maintains clock operation during power failures.

Backup characteristics:

Approximately 1 week clock retention
No battery replacement required
Automatic time recovery after auxiliary voltage restoration

When auxiliary power returns:

The relay restores operation.
The internal clock resumes normal operation.
New events receive correct time stamps.
6. Auxiliary Voltage Supply System

The REU615 requires a reliable auxiliary DC supply for operation.

The internal power supply module provides the required voltages for:

Protection electronics
Processing circuits
Communication interfaces
HMI functions
Power Supply Module Design

The relay uses a:

Galvanically isolated flyback-type DC/DC converter

Main advantages:

Electrical isolation between input and internal circuits
Improved safety
Stable internal voltage generation
Protection against supply disturbances
Front Panel Power Indication

A green LED indicator on the relay front panel provides power supply status information.

LED Status Meaning
Green LED ON Internal power supply module operating normally
Green LED OFF Auxiliary supply unavailable or internal power supply fault
Engineering and Maintenance Benefits

The REU615 memory and power management design provides several operational advantages:

Feature Benefit
Battery-free non-volatile memory Eliminates battery maintenance
Automatic setting storage Prevents configuration loss
Event retention Enables post-fault analysis
RTC backup Maintains accurate event timing
Fault record preservation Improves troubleshooting efficiency
Isolated DC/DC supply Enhances reliability and electrical safety