ABB REF542 1VCR007346 G0028｜Protection Relay｜

REF542

The ABB REF 542plus Feeder Protection and Control Unit provides comprehensive monitoring, self-diagnostic, and protection functions for medium-voltage switchgear applications. It is designed to supervise both the primary power equipment and the internal health status of the protection and control device, ensuring high availability, operational safety, and reliable fault protection.

Primary Equipment Monitoring Functions

The REF 542plus continuously calculates and monitors key operating parameters of the primary electrical equipment. These functions support condition monitoring, predictive maintenance, and asset management.

Available calculated monitoring values include:

Maximum current during the observation period
Observation period adjustable from 0 to 30 minutes
Average current during the observation period
Accumulated interrupted current
Total current interrupted by the circuit breaker over its operating life
Circuit breaker operating time
Number of switching operations
Open-close operation counter for circuit breakers
Spring charging time supervision
Available for circuit breakers equipped with spring operating mechanisms
Trip coil supervision
Monitoring of trip circuit availability and integrity

These monitoring functions help identify equipment aging, abnormal operating conditions, and maintenance requirements before failures occur.

Self-Diagnosis and Hardware Supervision

The REF 542plus includes integrated continuous self-diagnostic routines that monitor the condition of both hardware and software components.

The self-supervision system continuously checks:

Processor operation
Internal software execution
Protection modules
Input/output modules
Communication functions
Power supply conditions
Watchdog Monitoring

Every REF 542plus binary input and output module includes a dedicated watchdog contact.

The watchdog contact activates when:

A hardware fault occurs
Internal diagnostics detect a malfunction
Auxiliary power supply is lost

This signal can be connected to external monitoring systems to:

Detect IED failure
Generate alarms
Initiate predefined corrective actions
Improve system availability
Analog Input Supervision

The analog input channels can optionally be supervised to detect measurement circuit problems.

The monitoring function can identify:

Broken wires between instrument transformers and the IED
Faults in sensor connections
Loss of measurement signals

When an abnormal condition is detected, the REF 542plus generates an alarm notification.

Protection Functions

The REF 542plus provides a wide range of configurable protection functions for different power system applications. Multiple protection schemes can be implemented depending on the protected equipment and system requirements.

The available protection functions depend on the selected software license package.

Supported license levels include:

Basic Low
Basic
Multi Low
Multi
Differential
Distance

Each license level provides a different combination of protection functions, allowing users to select the required functionality for specific applications.

Current-Based Protection Functions

The REF 542plus provides extensive current protection functions, including:

Inrush Blocking

Inrush Blocking (ANSI 68)

Provides security against unwanted tripping during transformer energization by detecting magnetizing inrush conditions.

Overcurrent Protection
Instantaneous Overcurrent Protection

ANSI 50

Provides fast fault clearance for high-current short-circuit conditions without intentional time delay.

Definite-Time Overcurrent Protection

ANSI 51

Includes:

Two adjustable current thresholds
Independent time settings

Provides coordinated overcurrent protection for feeders and equipment.

Directional Overcurrent Protection

ANSI 67

Includes:

Two current thresholds
Directional supervision

Suitable for networks with multiple power flow directions, such as meshed distribution systems.

Inverse-Time Overcurrent Protection

ANSI 51 IDMT

Provides inverse definite minimum time characteristics for improved coordination with upstream and downstream protection devices.

Programmable Overcurrent Characteristics

Provides advanced directional earth fault detection using sector-based directional characteristics.

Key Benefits of REF 542plus
Comprehensive primary equipment condition monitoring
Continuous hardware and software self-diagnostics
Watchdog-based failure detection
Optional analog circuit supervision
Flexible software-based protection licensing
Wide range of current and earth fault protection functions
Support for simple feeders through complex distribution networks
Improved maintenance planning through operational statistics
Enhanced reliability for medium-voltage switchgear applications

The ABB REF 542plus combines feeder protection, equipment monitoring, diagnostics, and advanced protection algorithms into a single integrated platform, providing utilities and industrial users with a dependable solution for modern medium-voltage power distribution systems.