Explore GE Vernova
Resource Library
Get access to curated content, tools, and useful resources to help you face all your grid challenges.
Access the library
Electrification Businesses
Electrification Software
Power Conversion
Solar & Storage Solutions
Category banner
Protection Relays
Transformer Protection

Home > Grid Automation > Protection Relays > Transformer Protection > 845

Multilin 845
Comprehensive Protection & Management for Transformers

The Multilin™ 845 Transformer Protection System is a member of the Multilin 8 Series protective relay platform and has been designed for the protection, control and management of 2- and 3-winding power and distribution transformers in both utility and industrial applications.

The Multilin 845 provides advanced functionality for a wide range of transformer applications delivering high-speed protection, customizable programmable logic, advanced transformer monitoring and diagnostics, and support for the latest communications protocols for easy integration into new or existing power systems.

The Multilin 845 delivers comprehensive transformer health monitoring, diagnostics, and reporting with integrated connectivity to composite and multiple gas transformer DGA solutions such as, GE’s Kelman Transformer Monitoring devices, delivering actionable analytics for asset optimization and transformer life extension.

Key Benefits

  • Comprehensive transformer protection including fast operating differential protection, unique CT saturation and directional detection
  • Advanced transformer monitoring, diagnostics and disturbance recording extending asset life
  • Integrated protection & DGA for continuous transformer monitoring
  • Integrated arc flash detection using light sensors to reduce incident energy and equipment damage
  • High-end cyber security tools such as AAA, Radius, RBAC, and Syslog enabling NERC CIP requirements
  • Draw-out design simplifies testing, commissioning and maintenance
  • Optional Wi-Fi minimizes system configuration and facilitates safe relay programming and diagnostic retrieval
  • Monitored environmental conditions helps reduce system downtime
  • High flexibility for customized protection and control logic
What's New
845 Overview
Monitoring & Diagnostics
Arc Flash
Communications & Cyber Security

Full Color Graphical HMI Front Display

Multilin 845 Full Color Graphical HMI Front Display

A large, full color Graphic Control Panel (GCP) ensures clear representation of critical status and measurements. The 8 Series offers two options for front panels:

  • 10 Programmable Push buttons with 12 programmable LEDs
  • 3 Programmable Push buttons and 12 programmable LEDs

Switchgear Control and Configurable SLD

The Multilin 8 Series provides a configurable dynamic SLD up to six (6) pages for comprehensive switchgear control of up to 3 breakers and 9 disconnect switches; including interlocks. Up to 15 digital and metering status elements can be configured per SLD page.

Platform Overview

The Multilin 8 Series platform delivers the highest level of quality, reliability and performance with…

Innovative Technology & Design

  • Patented environmental monitoring and diagnostics helps visibility on change in environmental parameters
  • Advanced, flexible and embedded communications: IEC® 61850 Ed2, IEC 62439/PRP, Modbus® RTU & TCP/IP, DNP3.0, IEC 60870-5-104, IEC 60870-5-103
  • Single setup and configuration across the platform
  • Field swappable power supply
  • Draw-out design simplifies testing, commissioning and maintenance, thereby increasing process uptime
  • Optional Wi-Fi connectivity minimizes system configuration and provides safe relay programming and diagnostic retrieval
  • Elimination of electrolytic capacitors

Exceptional Quality & Reliability

  • IPC A-610-E Class 3 Manufacturing standards – highest industry standards for electronic manufacturing
  • Highest reliability standards for electronics testing
  • Environmental Stress Screening and full functional testing
  • Rated for IP54 applications
  • Standard Harsh Conformal Coating

Uncompromising Service & Support

  • Covered under GE’s 10 year warranty plan
  • Fully designed, tested and assembled at GE facilities
8 series exploded view

Multilin 845 Overview

The 845 has been designed for the protection, control and management of 2- and 3-winding power and distribution transformers in both utility and industrial applications. The 845 delivers comprehensive transformer health monitoring, diagnostics, and reporting with integrated connectivity to single and multi-gas transformer DGA solutions such as, GE’s Kelman Transformer Monitoring devices, delivering actionable analytics for asset optimization and life extension.


  • Primary and back-up protection and management of small, medium and larger power and distribution transformers, autotransformers and reactors
  • Designed for Utility (Transmission & Distribution) or Industrial applications
  • Integrated transformer protection, monitoring diagnostics and transformer health visualization

Multilin 845 feeder protection relay functional block diagram

845 Block Diagram

ANSI Device Numbers & Functions

Device Number Function
24 Volts per Hertz
25 Synchrocheck
27X Auxiliary Undervoltage
27P Phase Undervoltage
32 Directional Power
49 Hottest Spot Temperature
Aging Factor
Loss of Life
50/87 Instantaneous Differential Overcurrent
50BF Breaker Failure 
50G Ground Instantaneous Overcurrent
50N Neutral Instantaneous Overcurrent
Device Number Function
50P Phase Instantaneous Overcurrent
50_2 Negative Sequence Instantaneous Overcurrent
51G Ground Time Overcurrent
51N Neutral Time Overcurrent
51_2 Negative Sequence Time Overcurrent
55 Power Factor
59N Neutral Overvoltage
59P Phase Overvoltage
59X Auxiliary Overvoltage
59_2 Negative Sequence Overvoltage
Device Number Function
67G Ground Directional Element
67N Neutral Directional Element
67P Phase Directional Element
81O Overfrequency
81U Underfrequency
81R Frequency Rate of Change
87G Restricted Ground Fault (RGF)
87T Transformer differential
AFP Arc Flash Protection
VTFF Voltage Transformer Fuse Failure
Differential vs. Restraint Characteristic (ld vs.lr)

The settings for the dual-slope, dual-breakpoint characteristic provides higher flexibility for shaping up the characteristic and achieving better sensitivity and security.

Percent Differential Protection

The 845 provides enhanced security by including both restrained and unrestrained (instantaneous) differential protection. The percent differential element is based on a configurable dual-breakpoint/dual-slope differential restraint characteristic with inrush and overexcitation inhibits based on 2nd & 5th harmonics. The restraint current is calculated as a maximum of the internally compensated currents for better through-fault stability under CT saturation conditions.

The percent characteristic allows the element to account for both DC and AC saturation of the current transformers.

The “cubic spline” curve characteristics enables the relay to perform accurately for restraint current in range between the two slope breakpoints

Integrated Arc Flash Protection

The Multilin 8 Series supports an integrated arc flash module providing constant monitoring of an arc flash condition within the switchgear, motor control control centers, or panelboards. With a 2ms protection pass, the 8 Series is able to detect light and overcurrent using 4 arc sensors connected to the 8 Series relay. In situations where an arc flash/fault does occur, the relay is able to quickly identify the fault and issue a trip command to the associated breaker thereby reducing the total incident energy and minimizing resulting equipment damage.

Self-monitoring and diagnostics of the sensors ensures the health of the sensors as well as the full length fiber cables. LEDs on the front panel display of the 845 can be configured to indicate the health of the sensors and its connections to the relay.

Arc Flash

Fast, reliable arc flash protection with light-based arc flash sensors integrated within the Multilin 8 Series of protection & control devices. With arc flash detection in as fast as 2msec, the costs associated with equipment damage and unplanned downtime is significantly reduced.

Monitoring & Diagnostics

The Multilin 845 includes high accuracy metering and recording for all AC signals. Voltage, current, and power metering are built into the relay as a standard feature. Current and voltage parameters are available as total RMS magnitude, and as fundamental frequency magnitude and angle.

Learned Data

Transformer Learned Data Record Visualization

Data Logging & Learned Data

The 845 captures key electrical and DGA data values during transformer energization to trend and analyze transformer performance. Data is summarized and presented to operators through a pre-formatted Health Report to clear indication of changes to measured parameters. Up to 365 records are supported within the 845 relay. Up to 365 latest records are supported in the 845 relay. The data, when input cumulatively to the transformer model screens helps in visualizing trends and correlating key transformer electrical and DGA parameters.

Trip and Close Circuit Monitoring

The 845 relay provides Trip and Close Circuit Monitoring elements

Breaker Arcing Current

This element calculates an estimate of the per-phase wear on the breaker contacts by measuring and integrating the current squared passing through the breaker contacts as an arc. When the threshold is exceeded in any phase, the relay can set an output operand and set an alarm.

Breaker Health

The 845 relay provides breaker health information by monitoring and analyzing the operation count, arcing energy of breaking current, arcing time, tripping time, closing time and spring charging time if applicable.

Integrated Electrical and DGA for Comprehensive Transformer Monitoring & Diagnostics

The Multilin 845 offers advanced transformer health monitoring and diagnostics through advanced notification of potential issues before they become critical. The Multilin 845 features detailed learned data, summarized pre/post-fault records, and integration with GE’s DGA devices to collect, trend, and analyze a transformer’s fault gases. This enables operators to minimize costly unplanned outages and equipment failures.

845 advanced transformer health monitoring and diagnostics

Environmental Monitoring

The 845 implements a patented environmental monitoring system that measures and provides operating condition information. Reliable and secure operation of the 845 relay and other electronic devices in the vicinity may be affected by environmental factors. The 845 relay has been designed to meet or exceed all required industry standards. Some operating conditions may be beyond those standards and reduce total lifespan of the device.

8 series health report


The 845 provides advanced communications technologies for remote data and engineering access, making it easy and flexible to use and integrate into new and existing infrastructures. Direct support for copper/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 845 also supports two independent IP addresses, providing high flexibility for the most challenging of communication networks. Two independent network ports enables the 845 to connect with the primary protection network and the secondary monitoring network to deliver integrated asset monitoring and diagnostics by combining protection and DGA data.

Providing several Ethernet and serial port options and supporting a wide range of industry standard protocols, the 845 enables easy, direct integration into DCS and SCADA systems. The 845 supports the following protocols:

  • IEC 61850 Ed2, IEC 62439 / PRP
  • DNP 3.0, IEC 60870-5-103, IEC 60870-5-104
  • Modbus RTU, Modbus TCP/IP

The 845 has two interfaces as USB front port and Wi-Fi for ease of access to the relay. Wi-Fi Connectivity:

  • Simplify set-up and configuration
  • Simplify diagnostic retrieval
  • Eliminate personnel in front of switchgear
  • WPA-2 security
Protection relay network diagram

Cyber Security

The 869 cyber security enables the device to deliver full cyber security features that help operators to comply with NERC CIP guidelines and regulations.

AAA Server Support (Radius/LDAP)

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 will enable integration with established SEM (Security Event Management) systems.

Cyber security with Radius Authentication

Software & Configuration

The EnerVista™ suite is an industry-leading set of software programs that simplifies every aspect of using the Multilin 845.

EnerVista provides all the tools to monitor the status of the protected asset, maintain the device and integrate the information measured by the Multilin 8 Series, into SCADA or DCS process control systems. The ability to easily view sequence of events is an integral part of the setup software, as postmortem event analysis is critical to proper system management.

EnerVista Launchpad

The setup tools within Launchpad allow for the configuration of devices in real-time, by communicating via serial, Ethernet or modem connections, or offline by creating device setting files to be sent to devices at a later time.

8 Series Setup Software

8 Series Setup Software is single setup and configuration tool across the platform and can reduce device setup and configuration time.

Simplified Setup & On-Going Maintenance

845 set up

8 Series Retrofit

8 Series retrofit

Explore the 8 Series Retrofit

Retrofit Existing SR 745 Devices to the Multilin 845 in Minutes

Traditionally, retrofitting an existing relay has been a challenging, time consuming task often requiring re-engineering, new drawings, panel modifications, re-wiring and re-testing.

The 8 Series Retrofit provides a quick, 3-step solution to upgrade previously installed SR 745 relays. With the new 8 Series Retrofit users are able to install the 845 Transformer System without modifying existing cutouts and wiring, and without any drawing changes or re-engineering time.

Buy 745 to 845 Retrofit

Easy 3-Step Process to Upgrade in as Fast as 21 Minutes

Step 1 update settings file

EnerVista 8 Series Setup Software provides automated setting file conversion. Once completed, a graphical report is provided to verify and call out any specific settings that may need attention.

Step 2 replace relay

Simply remove the upper, lower and low voltage terminal blocks and then remove the SR chassis from the panel. No need to disconnect any of the field wiring.

Step 3 plug & play reconnection

Insert the new 8 Series Retrofit chassis into the switchgear and simply plug-in the old terminal blocks - there is no need to make any cut-out modifications or push and pull cables.