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Multilin L30

Cost-Effective Current Differential System for Lines and Cables

The Multilin L30 Line Differential System is a cost-effective line current differential protection relay intended for sub-transmission and medium voltage lines and cables, providing reliable and secure operation even under the worst-case power system conditions. The Multilin L30 provides secure high speed fault detection and clearance suitable for three-pole tripping applications.

Part of the Universal Relay (UR) family, the Multilin L30 comes with a variety of versatile features truly integrating protection, monitoring, metering, communication and control in one easy-to-use device.

Key Benefits

  • Proven current differential protection for secure, high-speed tripping

  • Increased sensitivity through dynamic charging current compensation and communication channel asymmetry compensation

  • Adaptive restraint characteristic provides security against measurement errors including CT saturation

  • Embedded Synchrophasor measurement capabilities (per IEEE® C37.118), eliminating the need for dedicated PMUs and support for synchrophasor multi-cast (per IEC® 61850-90-5) reducing bandwidth
    and communications infrastructure costs

  • 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

  • Advanced IEC 61850 Ed. 1 and Ed. 2 certified implementation, complete settings via SCL files and IEC 61850-9-2 process bus solution ensures interoperability, device managing optimization and reduced cost of ownership

  • Routable GOOSE (R-GOOSE) enables customer to send GOOSE messages beyond the substation, which enables WAPC and more cost effective communication architectures for wide area applications

  • Supports IEEE C37.111-1999/2013, IEC 60255-24 Ed 2.0 COMTRADE standard


  • Overhead lines and underground cables of different voltage levels

  • Circuits with tapped transformer feeders

  • Suitable for three-terminal lines, with channel redundancy and Direct Transfer Tripping (DTT)

  • Wide area system monitoring and control using integrated protection and synchrophasor measurement

  • Applications requiring three-pole autoreclosing and independent synchrocheck supervision

Protection and Control

The Multilin L30 offers a high degree of modularity in its design and functionality, providing superior performance while meeting the toughest requirements of the marketplace. Advanced protection and control features of this relay includes:

Current Differential Protection

​The L30 current differential protection relay uses superior and patented algorithms to address the challenges of bandwidth, security, dependability
and sensitivity in current differential relaying. Bandwidth requirements are effectively addressed by means of a patented new data consolidation technique called “phaselets”. This permits application within a communications bandwidth of 64 Kbps, and can detect faults within a half cycle plus channel delay.

The L30 innovative dual slope adaptive restraint characteristic, based on estimates of measurement errors, allows the relay to be secure on severe external faults while maintaining sensitivity for internal faults. The
estimate of errors in the input currents permits more sensitive settings than those used in the traditional percent differential schemes. The line differential element also has 2nd harmonic inrush-current inhibit for in-zone
power transformer protection. This functionality enables the L30 to protect 2 or 3-terminal lines that have a power transformer in between ends.

The L30 approach to clock synchronization relies upon precise distributed synchronization. Clocks are phase synchronized to each other and frequency synchronized to the power system frequency. Each relay compares its
clock to the phase of the other clocks and makes appropriate adjustments. This allows for greater transient ride-through for power system and communications disturbances. Enhanced additional security is provided by a sensitive current disturbance detector, which can be used to supervise the current differential element.

Charging Current Compensation

For long lines and especially for underground cables, the charging current may be large and result in excessively high pickup settings. The L30 can dynamically compensate the charging current, thus increasing its sensitivity to the fault current on long transmission lines.

Enhanced Monitoring Features

The L30 uses advanced error detection and supervising functions to secure the L30 against maloperation due to erroneous data. High bit error rates are addressed by means of computing a 32-bit CRC checksum, effectively addressing the concerns of multiple bit errors due to high channel noise. 

On multiplexed channels, channel asymmetry may be expected due to path switching causing spurious differential currents, which can endanger the security of the differential system. By using GPS time synchronization, up to 10ms of channel asymmetry can be compensated. Extra security has been implemented in the L30 to ensure proper operation in the event of IRIG-B
signal failure.

Integrated channel monitoring provides real time diagnostic data on the health of the L30. Communications channel deterioration or failure will activate an alarm, and can be used to enable backup protection. Channel propagation delay is monitored and adjusted according to variations in communication paths.

Communication Topologies

Relays can communicate through direct fiber, RS422, G.703, and IEEE C37.94 interfaces at 64Kbps, with extensive channel monitoring and diagnostics. In a current differential scheme, the L30s exchange data via the communication link, acting either as master collecting data, making calculations and making all relevant trip and restraint decisions, or as slave only, transmitting current data to the one acting as master. For two-terminal applications, use the redundant communications capability of the L30 for
optimal reliability of the current differential line protection. For this scheme, data is continuously transmitted over both channels, so if a failure occurs, the L30 will continue to provide current differential protection.

For three-terminal applications, advanced inter relay communication features eliminate the need for redundant communication channels due to the ability of the L30 to automatically switch between master and slave mode, maintaining a dependable system even with a failure of one of the communication channels.

Overvoltage and Undervoltage Protection

Long lines under lightly loaded or no-load conditions may experience voltages exceeding rated per unit voltage level of the line. Use the three phase overvoltage elements of the L30 to initiate a local trip as well as a remote trip using Direct Transfer Tripping (DTT).

Overcurrent Functions

The L30 provides thermal overload, and time and instantaneous overcurrent elements for phase, neutral, ground, negative sequence, phase and neutral directional. The neutral directional overcurrent element supports enhanced dual polarization modes which can be configured to prioritize on voltage or current polarization. Any of them can run in parallel with primary differential protection or can be programmed to run when the differential
element is not available. 


Direct Transfer Trip (DTT)

Use the DTT feature of L30 to trip remote breakers. Both single and three-pole DTTs are supported. Up to eight signals can be sent over pilot communications channels, selectable through user-configurable logic.


The L30 provides multi-shot autoreclosing for three-pole applications with independently programmable dead time for each shot. Autoreclose can be dynamically blocked by user-programmable logic.

Synchronism Check

The L30 provides six synchrocheck elements that monitor voltage difference, phase angle difference and slip frequency taking the CB closing time into
account to ensure proper breaker closure as per user requirements. The L30 provides additional enhancements in synchronizing, by checking dead
source conditions for synchronism bypass under these conditions.

Breaker Failure

The L30 provides two fully independent breaker failure protection elements.

IEC 61850 Process Bus
The IEC 61850 Process Bus module is designed to interface with the GE Multilin HardFiber System, allowing bi-directional IEC 61850 fiber optic communications. The HardFiber System is designed to integrate seamlessly with existing UR applications, including protection functions, FlexLogic™, metering and communications. The GE Multilin HardFiber System offers the
following benefits:

  • Communicates using open standard IEC 61850 messaging

  • Drastically reduces P&C design, installation and testing labor by      eliminating individual copper terminations

  • Integrates with existing L30’s by replacing traditional CT/VT inputs with the IEC 61850 Process Bus module

  • Does not introduce new cyber security concerns

Advanced Automation

The L30 incorporates advanced automation features including powerful FlexLogic programmable logic, communication, and SCADA capabilities that far surpass what is found in the average line relay. The L30 integrates seamlessly with other UR relays for complete system protection.


FlexLogic is the powerful UR-platform programming logic engine that provides the ability to create customized protection and control schemes, minimizing the need and associated costs of, auxiliary components and
wiring. With 1024 lines of FlexLogic, the L30 can be programmed to provide the required tripping logic along with custom scheme logic for line breaker control and interlocking and dynamic setting group changes.

Scalable Hardware

The L30 is available with a multitude of I/O configurations to suit the most demanding application needs. The expandable modular design allows for easy configuration and future upgrades.

  • Flexible, modular high density I/O covering a broad range of input signals and tripping schemes

  • Mechanically latching outputs can be used to develop secure interlocking applications and replace electromechanical lockout relays

Monitoring and Metering

The L30 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.

Fault and Disturbance Recording

The advanced disturbance and event recordingfeatures within the L30 can significantly reduce the time needed for postmortem analysis of power system events and the creation of regulatory reports.


Recording functions include:

  • Sequence of Event (SOE)

        - 1024 time stamped events

  • Oscillography

        - Supports IEEE C37.111-1999/2013, IEC 60255-24 Ed 2.0 COMTRADE                 standard
        - 64 digital & up to 40 analog channels
        - Events with up to 45s length

  • Data Logger and Disturbance Recording

        - 16 channels up to 1 sample/cycle/channel

  • Fault Reports

        - Powerful summary report of pre-fault and fault values

The very high sampling rate and large amount of storage space available for data recording in the L30 can eliminate the need for installing costly stand-alone recording equipment.

Advanced Device Health Diagnostics 

The L30 performs comprehensive device health diagnostic tests at startup and continuously during run-time to test its own major functions and critical hardware. These diagnostic tests monitor for conditions that could impact security and availability of protection, and present device status via SCADA communications and front panel display. Providing continuous monitoring
and early detection of possible issues help improve system uptime.

  • Comprehensive device health diagnostic performed at startup

  • Monitors the CT/VT input circuitry to validate the integrity of all signals

Cyber Security - CyberSentry UR

CyberSentry UR enabled UR devices deliver full cyber security features that help customers to comply with NERC CIP and NIST® IR 7628 cyber security requirements.

This software option delivers the following core features:


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.


The L30 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 Ethernet ports, redundant Ethernet option and the embedded managed Ethernet switch
provide the means to create fault tolerant communication architectures in an easy, cost effective manner. The L30 supports the most popular industry standard protocols enabling easy, direct integration into monitoring and
SCADA systems.

  • IEC 61850 Ed. 1 and Ed. 2 with 61850-9-2 and 61850-90-5 support

  • DNP 3.0 (serial & TCP/IP)•

  • Ethernet Global Data (EGD)

  • IEC 60870-5-103 and IEC 60870-5-104

  • Modbus RTU, Modbus TCP/IP

  • HTTP, TFTP, SFTP and MMS file transfer

  • IEEE1588 and redundant SNTP for time synchronization

  • PRP as per IEC 62439-3•

  • Support Routable GOOSE (R-GOOSE)

Interoperability with Embeded IEC 61850 Ed 1 and Ed2

The new IEC 61850 implementation in the UR Family positions GE as an industry leader in this standard.

  • Implements, user selectable, Ed. 1 and Ed. 2 of the standard across the entire UR Family

  • Provides full relay setting management via standard SCL files (ICD, CID and IID)

  • Enables automated relay setting management using 3rd party tools through standard file transfer services (MMS and SFTP)

  • Increases the number of Logical Devices and data mapped to them, GOOSE messages from up to 64 remote devices, and reports to support different organizational needs for data transfer and reduce dependency on generic logical nodes

  • Configures GE Systems based on IEC 61850 using universal 3rd party tools

  • Multicast IEEE C37.118 synchrophasor data between PMU and PDC devices using IEC 91850-90-5

  • R-GOOSE enable customer to send GOOSE messages beyond the substation, which enables WAPC and more cost effective communication architectures for wide area applications

Lan Redundancy

Substation LAN redundancy has been traditionally accomplished by reconfiguring the active network topology in case of failure. Regardless of the type of LAN architecture (tree, mesh, etc), reconfiguring the active LAN requires time to switchover, during which the LAN is unavailable. UR devices deliver redundancy as specified by PRP-IEC 62439-3, which eliminates the dependency on LAN reconfiguration and the associated switchover time. The UR becomes a dual attached node that transmits data packets over both main and redundant networks simultaneously, so in case of failure, one of the
data packets will reach the receiving device with no time delay.


UR devices support multiple languages: English, French, Russian, Chinese, Turkish, German, Polish and Japanese. These language options are available on the front panel, in the EnerVista setup software, and in the product manuals. Easily switch between English and an additional language on the local displays without uploading new firmware.


The L30 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.


Typical two-terminal application of L30. L30 supports a variety of media cards for signaling between L30’s including direct multimode or singlemode fiber, RS422, G.703 and IEEE C37.94.

L30 Brochure

L30 Manual

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