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Bus Protection

Home > Grid Automation > Protection Relays > Bus Protection > B90

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Multilin B90
Low Impedance Bus Protection System

The Multilin B90 bus protection relay, a member of the UR Family, features integrated protection and breaker failure for re-configurable MV, HV, EHV multi-section busbars with up to 24 feeders. Use one or more B90 relays together to build a flexible protection system that can be engineered to meet specific application requirements. The B90 performs fast and secure low-impedance bus protection with a sub-cycle tripping time of 0.75 cycles and 06 differential zones per phase.

Key Benefits

  • High-speed protection algorithm for enhanced stability with trip times of 0.75 power cycle with CT saturation detector that operates with only 2 msec of saturation-free current
  • Superior CT saturation detector that operates with only 2 msec of saturation-free current
  • Suitable for different bus configurations, scalable architecture to protect up to 24 feeders
  • Advanced IEC61850 Ed. 1 and Ed. 2 certified implementation and complete setting in a single SCL file ensures interoperability, device management optimization and reduced cost of ownership
  • Routable GOOSE (R-GOOSE) enables GOOSE messages going beyond the substation
  • Advance Cyber security features “CyberSentryTM” that helps meet modern industry requirements
  • Integrated isolator position monitoring, alarming and dynamic bus replica
  • Application flexibility with multiple I/O options including high density I/O, programmable logic, modularity, and specific customization
  • An integrated large, full color display, provides real-time visualization and control of the protected bay, via a bay mimic as well as annunciator functionality and graphical visualization of phasors


  • Single bus, breaker-and-half busbar configurations, double Bus and triple Bus with and without bus couplers
  • Re-configurable multi-section busbar with up to 24 feeders
What's New
Protection & Control
Monitoring & Diagnostic
Software & Security
UR 1 integrated Platform across all 18 applications
IEC 61850 icon

New and Enhanced Communication Capabilities

  • Support switchable IEC 61850 Ed. 1 and Ed. 2 and redundant SNTP (FW 7.7x)
  • New UR front panel with integrated 7” color, graphical display - providing operators with enhanced situational awareness (FW 7.6x)
  • High density I/O module supporting up to 120 inputs or up to 72 contact outputs – eliminating the need for additional discrete devices (FW 7.6x)
Cyber security icon

Cyber Security - CyberSentry UR (FW v7.xx)

CyberSentryTM enables UR devices to deliver full cyber security features that help customers to comply with cyber security requirements (NERC CIP, IEEE 1686, IEC 62443, etc):

  • Secured firmware upgrade: FW file includes hash code that enables authentication prior to being used for upgrading UR Relay (FW 7.9x)
Oscillography icon

Extended Oscillography Records (FW v7.xx)

  • Increased number of digital and analog channels (FW 7.90)
  • Supports IEEE C37.111-1999/2013, IEC 60255-24 Ed 2.0 COMTRADE 2013 standard (FW v7.40)
  • Configurable events allow for records of up to 45s at 64 samples per cycle
Protection and control icon

Protection and Control Functionality

  • Increased number of bus differential zones - Six zones (FW 7.30)

Key Benefits

  • Multi-zone bus differential protection with restrained and unrestrained function
  • Fast and reliable CT saturation detection
  • Breaker failure protection
  • End fault (dead zone) protection
  • Check-zone functionality
  • CT ratio mismatch compensation
  • Dynamic bus replica
  • Backup time and instantaneous overcurrent elements
  • Undervoltage function for supervision purposess
  • Supports Routable GOOSE (R-GOOSE)

Protection & Control

The B90 bus differential relay provides fast and secure low-impedance bus protection for reconfigurable LV, HV, and EHV busbars. Use one B90 to protect up to 8 feeders and use three or more B90s together in a centralized phase-segregated architecture to protect up to 24 feeders. Many busbar applications such as single, double, triple, breaker-and-a-half, with or without transfer bus, can be protected using the B90. The B90 relay is ideally suited in applications where high-impedance schemes were typically used. Part of the Universal Relay family, the B90 comes with a variety of versatile features, truly integrating protection, monitoring, metering, communication and control in one easy-to-use device. The Universal Relay family offers a high degree of modularity in its design and functionality, providing superior performance in protection and control, while meeting the toughest requirements of the marketplace.

Functional Block Diagram

B90 Functional Block Diagram

ANSI Device Numbers & Functions

Device Number Function
27 Undervoltage
50 Instantaneous Overcurrent
51 Time Overcurrent
50/74 CT Trouble
87B Bus Differential
Device Number Function
50/87 Unrestrained Bus Differential
51 Time Overcurrent
50BF Breaker Fail
50EF End Fault Protection

Key Features

  • Isolator monitoring (up to 48) and alarming
  • CT trouble monitoring
  • VT supervision
  • Metering - current, voltage, frequency
  • Oscillography - 64 samples/cycle, up to 64 records
  • Event Recorder - 1024 time tagged events, with 0.5 ms scan of digital inputs
  • User configurable fault report

Monitoring & Diagnostic

Single line diagram

The B90 is the single point for protection, control, metering, and monitoring in one integrated device that can easily be connected directly into DCS or SCADA monitoring and control systems like Viewpoint Monitoring as shown.

Advanced Automation

The B90 incorporates advanced automation features including powerful FlexLogic programmable logic, communication, and SCADA capabilities that far surpass what is found in the average bus protection relay. The B90 integrates seamlessly with other UR relays for complete system protection.

FlexLogic diagram

FlexLogic allows for the customization of the B90 outputs for most bus protection schemes and applications.

Key Features

  • Three independent 100Mbps Ethernet ports enable purpose specific LAN support that eliminates latency effect of heavy traffic protocols on mission critical communication services
  • Embedded IEEE 1588 time synch protocol support eliminates dedicated IRIG-B wiring requirements for IEDs
  • Direct I/O secures high-speed exchange of binary data between URs
  • Increase network availability by reducing failover time to zero through IEC62439-3 "PRP" support

Advanced Communications

The B90 bus protection relay provides for secure remote data and engineering access, making it easy and flexible to use and integrate into new and existing infrastructures. Fiber optic Ethernet provides high-bandwidth communications allowing for low-latency controls and high-speed file transfers of relay fault and event record information. The available three independent and redundant Ethernet options provide the means to create fault tolerant communication architectures in an easy, cost-effective manner.

The B90 relay supports the most popular industry standard protocols enabling easy, direct integration into DCS and SCADA systems.

  • IEC 61850 Ed. 1/Ed. 2
  • DNP 3.0 (serial & TCP/IP)
  • IEC 60870-5-103 and IEC 60870-5-104
  • Modbus RTU, Modbus TCP/IP
  • HTTP, TFTP, SFTP and MMS file transfer
  • Redundant SNTP and IEEE 1588 for time synchronization
  • PRP as per IEC 62439-3

Cyber Security - CyberSentry™ UR (FW v7.4xx)

CyberSentry enables UR devices to deliver full cyber security features that help customers to comply with NERC CIP and NITIR 7628 cyber security requirements through supporting the following core features:

Secure FW upgrade

UR FW files v7.9 and up now include a hash code that allows for authentication prior to being used for upgrading UR devices.

Password Complexity

Supporting up to 20 alpha- numeric or special characters, UR passwords exceed NERC CIP requirements for password complexity. Individual passwords per role are available.

AAA Server Support (Radius)

Enables integration with centrally managed authentication and accounting of all user activities and uses modern industry best practices and standards that meet and exceed NERC CIP requirements for authentication and password management.

Role Based Access Control (RBAC)

Efficiently administrate users and roles within UR devices. The new and advanced access functions allow users to configure up to five roles for up to eight configurable users with independent passwords. The standard “Remote Authentication Dial In User Service” (Radius) is used for authentication. 

Event Recorder (Syslog for SEM)

Capture all cyber security related events within a SOE element (login, logout, invalid password attempts, remote/local access, user in session, settings change, FW update, etc), and then serve and classify data by security level using standard Syslog data format. This enables UR devices integration with established SEM (Security Event Management) systems.

EnerVista™ Software

The EnerVista™ suite is an industry-leading set of software programs that simplifies every aspect of using the B90 relay. The EnerVista™ suite provides all the tools to monitor the status of the protected asset, maintain the relay, and integrate information measured by the B90 into DCS or SCADA monitoring systems. Convenient COMTRADE and Sequence of Events viewers are an integral part of the UR setup software included with every UR relay, to carry out postmortem event analysis and ensure proper protection system operation.Learn More

EnerVista™ Software

Record the operation of the internal B90 elements and external connected devices with 1ms time-stamped accuracy.

EnerVista™ Software

Create B90 setting file templates to ensure critical settings are not altered.