UR - The Universal Relay

UR - The Universal Relay
g GE Power Management UR - The Universal Relay

g UR Features GE Power Management
FAMILY of relays built on a common platform Common “look & feel” for ease of use product to product All “bells & whistles”, present and future, available to whole family Reduced training time and drafting costs MODULAR architecture Scaleable - accommodates a scaleable I/O architecture Flexible - accommodates different types of I/O Upgradeable - accommodates upgrading to new technologies

g UR Features GE Power Management COMMUNICATIONS
High-speed networking capability (Ethernet - fiber, redundancy) Multiple Protocols - UCA 2.0, DNP 3.0, Modbus, IEC SUBSTATION Automation - System Solution PMCS + UR with UCA 2.0 MMS/Ethernet

Solution: Modular Software
g GE Power Management Software Issues Software accounts for 90% of digital relay design Most support functions are required in all types of relays Market needs are driving shorter development cycles Solution: Modular Software

g Modular Software GE Power Management
‘Object Oriented Design’ allows for scalable, flexible and re-useable software and features Protection Class TOC IOC Distance Differential Frequency Volts/Hz etc Objects

Solution: Modular Hardware Design
GE Power Management Hardware Issues Microprocessor / Integrated Circuit Functionality is increasing exponentially Components can become obsolete in 1 to 2 years Utility expect a 20+ year life Solution: Modular Hardware Design

Modular Hardware Design
GE Power Management Modular Hardware Design Concept Physical Realization

g Common Platform GE Power Management Common hardware modules
Application Software Transformer Application Line Generator Feeder Control (PLC) Common hardware modules Common software modules Capability to run a wide variety of applications Result: Universal Relay (UR)

g Hardware GE Power Management Flash memory
Draw-out modules for serviceability Expandable I/O Field upgradable

g Hardware GE Power Management 4RU, 19 inch rack-mount chassis
Hinged faceplate allows easy access to modules Faceplate can be mounted separately on doors for applications limited in depth Extension cable connects faceplate to main unit

g Hardware - Modular I/O GE Power Management
Configurable I/O via sub-modules Sub-Modules

g Draw-Out Modules GE Power Management
Modular design allows all modules to be easily inserted or removed for upgrading or repair. Field wiring is left undisturbed

g Hardware - Interfaces GE Power Management
CONTACT INPUTS (expandable) Configurable inputs may be used for: Breaker status Oscillography trigger Control inputs CONTACT OUTPUTS (expandable) Fully programmable Trip rated Form-A relays Form-C relays Fast Form-C relays

g User Interfaces GE Power Management PROGRAM UPDATING COMMUNICATIONS
Flash memory storage of firmware for field updating via communications port. Enables product updating on-site for latest features COMMUNICATIONS Modbus RTU on 115 kbps MMS/UCA 2.0 on Redundant 10BaseF POWERFUL PROCESSORS Numerical data processing using a 32 bit CPU and DSP for high speed complex task processing

g FlexLogic GE Power Management
FlexLogic minimizes the requirement for auxiliary components and wiring while making more complex schemes possible. URPC The power of this product comes from it’s ability to create user-defined logic through GE Flexlogicª. Flexlogicª includes the option of Virtual inputs. Virtual inputs are data values that are communicated over the LAN by the 10 MBit Ethernet LAN created at the substation. This allows the user to minimize wiring through using the communication line to send information from point to point. Traditionally, protective relay logic has been relatively limited and simplistic. Any unusual applications involving interlocks, blocking, or supervisory functions had to be hardwired using contact inputs and outputs if the requirement could be met at all. This would entail significant expense in implementation and troubleshooting, the only other option was to approach a manufacturer for a feature enhancement. If this approach was possible, it was rarely completed in a timely manner as the new feature had to be designed, implemented, and thoroughly tested. The advent of Flexlogicª minimizes the requirement for auxiliary components and wiring while making more complex schemes possible. The logic that determines the interaction of inputs, elements, and outputs is field programmable through the use of logic equations (“postfix” notation) that are sequentially processed. The use of virtual inputs and outputs in addition to hardware is available internally and on the communication ports for other relays to use (distributed Flexlogicª). Also, the F30 contact input/output capability is expandable. The contact inputs can accept wet or dry contacts and contact outputs can be trip rated Form-C or Form-A.

Virtual Inputs / Outputs
g GE Power Management Virtual Inputs / Outputs Virtual Inputs / Outputs extend the I/O capability of the relay to LAN communications. Virtual Inputs allow the user to combine and-gate, or-gate, inverters, counters and timers to create specific logics that can fit a customer’s unique requirements.

Peer to Peer Communications
g GE Power Management Peer to Peer Communications Networkable Peer to peer communications Self-defining data External data access via corporate WAN Peer to peer communications: one can send virtual data from one relay to another without being told to do so. In effect the relays high speed communications enables the relay to send out information on it’s own. This is the far superior to a master-slave relationship because information is received on a continuous basis. Self-defining data: On power up the relay will identify itself to the host computer. The host computer will then query the relay and ask for all the data that the relay has. The relay will then download a complete database of objects into the host. The significance to this is that during software upgrades, the host will automatically be updated with the newest variables available inside the relay. Peer-to-peer communications and self-defining data are important because it enables the relays to continuously communicate bits of data to entire network of relays. This continuous stream of information is possible because the F-30’s high speed communication abilities which results in quicker detection and communication of faults. In a master-slave relationship, the master continuously pulls information from the slave. The consequences of this relationship are that the time needed to detect and communicate important information is lost.

g Metering GE Power Management Current (Phase, Neutral and Ground) -
Accuracy: ± 0.25% of reading or ± 0.1% of rating from 0.1 to 2.0 x CT rating (whichever is greater) Voltage (Vab Vbc Vca Van Vbn Vcn) - Accuracy: ± 0.25% of reading from 10 to 208 V Apparent Power (VA) - Accuracy: ± 1.0% of reading Real Power (Watts) - Accuracy: ± 1% of reading Reactive (Vars) - Accuracy: ± 1% Power Factor - Accuracy: ± 0.02

g Monitoring GE Power Management Oscillography Event Recorder
64 samples / power frequency cycle Adjustable Memory (1 record / 128 cycles to 31 records / 8 cycles) 6 Analog, 15 digital channels can be displayed Selectable triggers Adjustable trigger position Event Recorder 1024 events, events are date and time stamped to nearest millisecond Selection of points to monitor (pickup, operation, logic, I/O)

g Connectivity GE Power Management Communications URPC™ Integration
Protocols Peer to Peer Communications URPC™ Integration GE Power Management has engineered the F-30 with the vision that this relay would be integrated easily into any system. To accommodate this specification we have focused on the following areas to enable the user to easily and effectively incorporate the F-30 relay into their power system.

g Communications GE Power Management PROTOCOLS Modbus RTU protocol
Standard Front Port: RS232 Rear Port: RS485 up to 115kbps UCA2Ô protocol Application: MMS Physical: 10BaseT (Ethernet) or 10BaseF (Fiber Optic) Transport layer ISO-OSI and TCP/IP

Windows 95/ NT Based Software
g GE Power Management URPC Program Features Windows 95/ NT Based Software View actual values View/edit setting on-line View Event Recorder for troubleshooting Upgrade relay firmware programming View relay Status View/edit setting off-line with setting file manager On-line instruction manual Download & view oscillography in Comtrade format The Windows based F30PC program may be run on a PC with the Windows 95 or Windows NT operating system. The program may be used locally on the RS232 serial port or remotely on the other ports. It provides full access to the relay data with the following features: See above. Metered parameters that may be viewed with the F30PC program include current, voltage, apparent power (VA), real power (W), reactive power (var), and power factor. Current and voltage can be displayed in a graphical, phasor format. This is a particularly valuable feature that can reduce the troubleshooting of connection problems during commissioning. All status information such as target messages and digital input/output states may also be viewed with the PC program. Setting files may be created off-line (at a desk without an F30) or on-line (while communicating to an F30) and backup files may be stored to disk for future reference. The F30 stores a record of the last 1024 events. All events are date and time stamped to the nearest millisecond. Events consist of a broad range of change of state occurrences, including element pickups and operations, alarms, trips, contact operations, and setting changes. This provides the information needed to determine a sequence of events, which can reduce troubleshooting time and simplify report generation in the event of system faults. With the F30PC program, the event recorder is used as an index for quick access of snapshot records, setting change records, and oscillography records. Snapshot records store analog parameters and digital states at the time of the event. Setting change records store the old value and new value of any setting that has been altered and stored. The oscillography records captured by the F30 consist of current and voltage waveforms at 64 samples/cycle (up to 72 cycles), digital input states, and settings at the point of trigger. The number of pre-trigger and post-trigger cycles may also be selected. The event record, snapshot data, and setting change data may also be viewed on the faceplate display.

Event Recorder Capture Screen
g GE Power Management Event Recorder Capture Screen Snapshot Data Oscillographic Data Example of the F30PC program. Settings Change Data The three main types of data - Snapshot data, Oscillographic data, and Settings data - can be accessed from this screen, the Event recorder.

g GE Power Management Snapshot Data Example of the F30PC program.

g Oscillographic Data GE Power Management
Example of the F30PC program.

g Settings Change Data GE Power Management
Example of the F30PC program.

Staged release of enhancements to platform and individual relay models
GE Power Management UR Relay Types F30 Feeder Management Relay (9/98) L90 Line Current Differential (11/98) C30 Controller/Metering (2/99) C60 Controller/Metering/Breaker Failure (4/99) F60 Feeder Management Relay (4/99) T60 Transformer Management relay (4/99) D60 Line Distance Relay (5/99) L60 Line Current Phase Comparison Relay (6/99) Example of the F30PC program. Staged release of enhancements to platform and individual relay models

Substation Automation
g GE Power Management Substation Automation The UR Relay is the Engine for Substation Automation

UR - The Universal Relay
g GE Power Management UR - The Universal Relay

g GE Power Management UR L90 Line Differential Relay
The F30 is a digital relay that provides feeder protection and power metering in one integrated package. The UR F-30 establishes a platform that will serve as the basis for all future relays. This platform is the result/answer to the industry’s requests to standardize the protocol communication functions of relays. It may be used as a stand alone device or as a component of an automated sub-station control system. The relay establishes the high performance platform that will serve as the foundation to a highly flexible and easily connectable network of relays that will better serve the user’s needs. UR L90 Line Differential Relay An integrated transmission line protection system for series compensated lines

Power to Protect Your Lines
g GE Power Management L90 Line Differential Relay Power to Protect Your Lines Connectivity ModBus RTU MMS/UCA2TM Protocols SI Compatibility Flexibility The F30’s is the first relay to be UCA 2.0 (Utility Communications Architecture) compliant. UCA 2.0 protocol is the protocol identified by EPRI to be the future in communications protocol. This means that when MMS (Manufacturing Messaging Specification) technology is applied a “plug-and-play” effect is created because the user can communicate with the relay by simply “plugging” into the unit. (The user must have a laptop computer equipped with MMS software.) UCA 2.0 protocol, MMS technology and “plug-and-play” performance gives the F-30 the added flexibility that makes this product highly accessible and allows for painless integration into any protection scheme. The results of a highly flexible, easily connectable relay are an enhanced ability to allow you to control and protect a power system. These features also make this relay ideal for systems integration projects. FlexCurves FlexLogic FlexModules Other Features The second Relay designed from the ground up around the MMS/UCA 2TM Ethernet communications standard. Giving you the flexibility, connectivity and power to manage your facility.

Presentation Overview
g GE Power Management L90 Line Differential Relay Presentation Overview Applications Protection and Control New & Unique Concepts User Interfaces Order Codes

g Applications GE Power Management
L90 Line Differential Relay Applications The L90 is a digital current differential relay system intended to provide complete protection for transmission lines of any voltage level. Overhead Lines and Cables Lines with 2 Terminals EHV, HV, Sub-Transmission With/ without Series Compensation

Transmission Line Protection & Metering
GE Power Management L90 Line Differential Relay Transmission Line Protection & Metering

g Protection & Control Functions GE Power Management
L90 Line Differential Relay Protection & Control Functions Current Differential with Adaptive Restraint High Speed Tripping, 1/2 - 2 cycles Backup Overcurrent Direct Transfer Trip Stub Bus Protection Sensitive Ground Input The F30 CT/VT module may be ordered as sensitive ground. The sensitive ground CT input is ten times more sensitive than the regular ground CT input. This enables the F30 to provide ground fault protection on high impedance grounded or ungrounded systems and may be especially important when using a residual CT connection to detect ground faults. Phase Undervoltage The F30 has three individual phase Undervoltage elements (all with identical programmable characteristics): * Pickup level * Definite time or inverse time curve * Minimum operating voltage protection are: * Protection for sensitive loads such as induction motors * Permissive functions such as blocking of elements or external devices * Automatic re-Energization schemes Three Phase, Neutral and Ground Instantaneous Overcurrent The F30 instantaneous overcurrent protection includes: * Three individual phase instantaneous overcurrent elements (all with identical characteristics) * Neutral instantaneous overcurrent elements * Ground instantaneous overcurrent DC offset is removed from the input signal to prevent overreach. Each instantaneous overcurrent element has the following programmable characteristics: * Pickup level * A time delay during which current must exceed the pickup for operation Three Phase, Neutral and Ground Time Overcurrent The F30 time overcurrent protection includes: * Three individual phase time overcurrent elements (all with identical characteristics) * Neutral time overcurrent element * Ground time overcurrent element Neutral elements operate on the calculated 3I0 current; ground elements operate on the ground input current. Each time overcurrent element has the following programmable characteristics: * Pickup level * Choice of 13 standard curve shapes, 2 FlexCurvesª and curve multipliers n Instantaneous and electromechanical reset time characteristic

Current Differential Scheme
g GE Power Management L90 Line Differential Relay Current Differential Scheme Similar to a Percentage Restraint Scheme Adaptive Statistical Restraint Adaptive Based on Relay Measurements More Accurate and Sensitive Fault Sensing Detects High Impedance Single Line to Ground Faults that Existing Systems may not Detect The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function.

g GE Power Management L90 Line Differential Relay New & Unique Concepts Three key technical considerations in designing a new current differential relay: Data Consolidation Restraint Characteristic Sampling Synchronization The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function.

g Data Consolidation GE Power Management
L90 Line Differential Relay Data Consolidation Extract appropriate parameters to be transmitted from raw samples of transmission line currents Balance between transient response and bandwidth Phase consolidation: Phase current information is combined Faulted phase information is lost L90 does not use phase consolidation Time consolidation: Reduces communication bandwidth requirements Improves security caused by single corrupted data sample L90 uses time consolidation The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function.

g Phaselets Concept GE Power Management L90 Line Differential Relay
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Full Cycle Window = 8 Phaselets Phaselet ( 1/8 cycle) Disturbance Detector 50DD The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function.

Phaselets Concept - Prefault
g GE Power Management L90 Line Differential Relay Phaselets Concept - Prefault +X -X +R 1st Pre-Fault Phaselet: Disturbance Detector resets calculation window. Area of uncertainty +X -X +R +X -X +R The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function. -X +R +X Full Cycle Pre-Fault Phasor (No uncertainty) Phaselet 1 Phaselet 4 Phaselet 6 Phaselet 8

Phaselets Concept - Fault
g GE Power Management L90 Line Differential Relay Phaselets Concept - Fault -X +R +X 1st Fault Phaselet: Disturbance Detector resets calculation window. +X -X +R +X -X +R Phaselet 9 The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function. -X +R +X Full Cycle Fault Phasor (No uncertainty) Phaselet 12 Phaselet 14 Phaselet 16

g GE Power Management L90 Line Differential Relay Phaselets Concept - Fault Phaselet Simulation on ‘Noisy’ Waveform Sinusoid with random white Gaussian noise. The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function.

g GE Power Management L90 Line Differential Relay Phaselets Concept - Fault Phaselet Simulation on ‘Noisy’ Waveform Convergence of uncertainty area to equivalent of full cycle Fourier Transform. The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function. Decreasing ‘area of uncertainty’ (or variance error) as phaslet window size increases. Phaselets improve operating speed while maintaining security.

Restraint Characteristic
g GE Power Management L90 Line Differential Relay Restraint Characteristic Classic Dual-Slope Restraint Characteristic Ioperate = Iop = | I1 + I2 | Irestraint = Ir = K [ |I1| + |I2|] Ioperate Irestraint K1 K2 Protected Element The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function. I1 I2 Iop = | I1 + I2 |

Restraint Characteristic
g GE Power Management L90 Line Differential Relay Restraint Characteristic L90 combines the classic method with adaptive elliptical restraint to improve both security and dependability. Classic Dual-slope Characteristic L90 - Adaptive Elliptical Restraint Im Static restraint region formed by classic method Im Re Iop Ir Iop Re The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function. Dynamic restraint region based on magnitude of the variance error measurement (i.e. the difference between the actual values measured and the estimated data from the Fourier Transform calculation) When the waveform is distorted due to CT saturation, harmonic content, or fault initiation transients, the restraint region will grow larger.

Sampling Synchronization
GE Power Management L90 Line Differential Relay Sampling Synchronization L90 uses distributed clock synchronization Clocks are synchronized to each other (no master clock) Phases are synchronized to each other Primary source is current measurements Secondary source is time tagged messages (ping-pong) Timing error is driven to zero Phase angle deviations are minimized (<0.6 degree) Clocks are synchronized to the power system frequency Eliminates one source of error in phasor measurements Loop filter adjusts clock frequency Uses frequency and phase angle deviation The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function.

Sampling Synchronization “Ping-Pong” Synchronization Technique:
GE Power Management L90 Line Differential Relay Sampling Synchronization Current differential requires both relays to be in time synchronization for differential calculations. Tx Rx Rx Tx L90 #1 L90 #2 “Ping-Pong” Synchronization Technique: tf = forward travel time t0 Communications Channel tf tf = tr = t3 - t0 - (t2 - t1) 2 The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function. t1 t2 Traditional “Ping-Pong” synchronization technique assumes forward time delay (tf) is equal to the return travel time (tr). This is NOT the case for communications equipment found in the utility/industrial environment. tr = return travel time tr t3

Sampling Synchronization
GE Power Management L90 Line Differential Relay Sampling Synchronization L90 Improvements on “Ping-Pong” Synchronization scheme: Minimizes variance on channel delays and jitter by averaging “Ping-Pong” calculations Implements a DPLL (digital phase-locked-loop) allowing the Ping-Pong algorithm to stabilize to new path delays. Calculates phase error at each end due to channel delays and compensates clocks at both ends The user has a choice of any one of the above curves or curve multipliers to provide the desired TOC protection function.

g Flexibility GE Power Management Relay Channels FlexCurvesTM
L90 Line Differential Relay Flexibility Relay Channels FlexCurvesTM FlexLogicTM FlexModulesTM Metering and Monitoring The F-30’s flexibility will allow the user to better utilize their existing facilities by optimizing protections schemes through FlexCurvesÔ, FlexLogicÔ and high speed communications.

g Relay Channels GE Power Management
L90 Line Differential Relay Relay Channels Two Terminal Communication Channels 820 nm Multi-mode Fiber (LED) 1300 nm Multi-mode Fiber (LED) 1300 nm Single-mode Fiber (ELED) 1300 nm Single-mode Fiber (Laser) G.703 (April 99) RS422 (April 99) The F-30’s flexibility will allow the user to better utilize their existing facilities by optimizing protections schemes through FlexCurvesÔ, FlexLogicÔ and high speed communications. Three Terminal Available in April ‘99

g FlexCurves GE Power Management Typical application of FlexCurves:
L90 Line Differential Relay FlexCurves Typical application of FlexCurves: When the protection curves used for lateral taps 2 and 3 differ; custom FlexCurves can be constructed to coordinate with both. The user can create downloadable curve shapes described by the user themselves. The user can design FlexCurvesÔ to coordinate with multiple devices containing unusual curve shapes to best fit the users specific needs. Such applications include F-30’s used with fusses or F-30’s used in combinations of fuses with other standard time overcurrent relays.

g Monitoring GE Power Management Fault Location
L90 Line Differential Relay Monitoring Fault Location IRIG-B Time Synchronization CT Failure/Current Unbalance Trip Circuit Monitors Channel Monitor Test Features Local loopback for channel Manual test mode Playback of oscillography files The F-30’s flexibility will allow the user to better utilize their existing facilities by optimizing protections schemes through FlexCurvesÔ, FlexLogicÔ and high speed communications.

g User Interfaces GE Power Management L90 Line Differential Relay
PROTECTIVE COVER Protects keypad when not in use Can be fitted with a seal RESET KEY Clears event, EVENT CAUSE LED indicators, and latched alarms

STATUS INDICATORS IN SERVICE: The relay is operating normally TROUBLE: Self-test detected a problem TEST MODE: The relay is in test mode TRIP: A trip command had been issued ALARM: An alarm condition is present PICKUP: Pickup condition detected RS232 SERIAL PORT Connect to a PC to run URPC Use for downloading settings, monitoring data, sequence of events reports, Oscillography

EVENT CAUSE LED INDICATORS VOLTAGE: Event caused by voltage CURRENT: Event caused by current FREQUENCY: Not applicable OTHER: Not applicable PHASE A Indicates which PHASE B phase was PHASE C involved NEUTRAL/GROUND RS232 SERIAL PORT Connect to a PC to run URPC Use for downloading settings, monitoring data, sequence of events reports, Oscillography

g User Interfaces GE Power Management GE POWER MANAGEMENT RELAY
L90 Line Differential Relay User Interfaces GE POWER MANAGEMENT RELAY MENU HELP ESCAPE ENTER MESSAGE VALUE DISPLAY 40 character vacuum fluorescent display Visible in dim lighting or at any angle Used for programming, monitoring, status, fault diagnosis, user programmable messages and settings KEYPAD Numerical keypad and command keys allow full access to the relay Rubber keypad is dust tight and splash-proof with door Website address via HELP for technical support

CONTACT INPUTS (Expandable) Configurable inputs may be used for: Breaker status Oscillography trigger Control inputs CONTACT OUTPUTS (Expandable) Trip rated Form-A relays Form-C relays that may be programmed for auxiliary functions

COMMUNICATIONS ModBus® RTU on 115 kbps MMS/UCA 2.0 on Redundant 10BaseF PROGRAM UPDATING Flash memory storage of firmware for field updating via communications port. Enables product updating on-site for latest features. POWERFUL PROCESSORS Numerical data processing using a 32 bit CPU and DSP for high speed complex task processing

g Order Code GE Power Management L90 Line Differential Relay
L90 - * H C * - F ** - H * * - L * *- N* *- S**- U**- W** Base Unit L Base Unit CPU A RS485 + RS485 C RS BaseF D RS485 + Redundant 10BaseF Software Options No software options Mounting H Horizontal Faceplate C Faceplate with keypad and display Power Supply L /48 V (Low); VDC, VAC H /250 V (High); VDC, VAC CT/VT A Standard 4CT/4VT Digital I/O XX No module 6G 4 Form-A, 8 inputs I 4 SCR outputs, 16 inputs Digital I/O 6A A A 6A 2 Form-A, 2 Form-C, 8 inputs 6B B B 6B 2 Form-A, 2 Form-C, 4 inputs 6C C C 6C 8 Form-C outputs 6D D D 6D 16 Inputs 6E E E 6E 4 Form-C, 8 inputs 6F F F 6F 4 Form-A, 8 inputs 6G G G 6G 8 Fast Form-C outputs 6H H H 6H 4 Form-A, 8 inputs 6I I I 6I 6 Form-A, 4 inputs 6J J J 6J 4 SS SCR outputs, 8 inputs 6K K K 6K 4 Form-C, 4 Fast Form-C Inter-Relay Communications A 820 nm, multi-mode, LED, 2 Terminal 7B 1300 nm, multi-mode, LED, 2 Terminal 7C 1300 nm, single-mode, ELED, 2 Terminal 7D 1300 nm, single-mode, LASER, 2 Terminal 7R G Terminal 7T RS422 2 Terminal

g GE Power Management UR L90 Line Differential Relay
An integrated transmission line protection system for series compensated lines

UR - The Universal Relay

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