Universal Relay Family

Universal Relay Family
Protection Overview

FlexLogic™ and Distributed FlexLogic™ L90 – Line Differential Relay
Contents... Configurable Sources FlexLogic™ and Distributed FlexLogic™ L90 – Line Differential Relay D60 – Line Distance Relay T60 – Transformer Management Relay B30 – Bus Differential Relay F60 – Feeder Management Relay

Configurable Sources

Sources are then inputs to Metering and Protection elements
Concept of ‘Sources’ Configure multiple three phase current and voltage inputs from different points on the power system into Sources Sources are then inputs to Metering and Protection elements A W 51P  V I Source Metering Protection Universal Relay

Sources: Typical Applications
Breaker-and-a-half schemes Multi-winding (multi-restraint) Transformers Busbars Multiple Feeder applications Multiple Meter Synchrocheck

Sources Example 1: Breaker-and-a-Half Scheme

Sources Example 1: Traditional Relay Application

Sources Example 1: Inputs into the Universal Relay
VT1 CT1 CT2 CT3

Sources Example 1: Universal Relay solution using Sources

Sources Example 2: Breaker-and-a-Half Scheme with 3-Winding Transformer

VT1 CT1 CT2 CT3 CT4

Sources Example 3: Busbar with 5 feeders
Multiple Feeder + Busbar Sources Example 3: Busbar with 5 feeders

VT1 CT1 CT2 CT3 CT4 CT5

FlexLogicTM & Distributed FlexLogicTM
Universal Relay Family FlexLogicTM & Distributed FlexLogicTM

Universal Relay: Functional Architecture
Analog Inputs Programmable Logic (FlexLogic™) Virtual Outputs Ethernet (Fiber) Digital Remote Computed Parameters Metering Protection & Control Elements A/D DSP Hardware Software Ethernet LAN (Dual Redundant Fiber)

Distributed FlexLogic Example 1: 2 out of 3 Trip Logic Voting Scheme
AND OR Remote Input: Trip Relay 2 Remote Input: Trip Relay 3 Local: Trip ENABLE 0ms Remote Output Digital Substation LAN LOCAL RELAY RELAY 2 RELAY 3 Local RELAY

Distributed FlexLogic Example 1: Implementation of 2 out of 3 Voting Scheme

Distributed FlexLogic Example 2: Transformer Overcurrent Acceleration
TIME Current Pick-Up Level Coordination Time Feeder TOC Curve Transformer TOC Curve Accelerated Animation Substation LAN: 10/100 Mbps Ethernet (Dual Redundant Fiber) Transformer IED: IF Phase or Ground TOC pickup THEN send GOOSE message to ALL Feeder IEDs. Feeder IEDs: Send “No Fault” GOOSE if no TOC pickup ELSE Send “Fault” GOOSE if TOC pickup. If “No Fault” GOOSE from any Feeder IED then switch to accelerated TOC curve.

Distributed FlexLogic™
FlexLogic: Benefits FlexLogic™ Tailor your scheme logic to suit the application Avoid custom software modifications Distributed FlexLogic™ Across the substation LAN (at 10/100Mpbs) allows high-speed adaptive protection and coordination Across a power system WAN (at 155Mpbs using SONET system) allows high-speed control and automation

L90 Line Differential Relay
Universal Relay Family L90 Line Differential Relay

L90 Current Differential Relay: Features
Protection: Line current differential (87L) Trip logic Phase/Neutral/Ground TOCs Phase/Neutral/Ground IOCs Negative sequence TOC Negative sequence IOC Phase directional OCs Neutral directional OC Phase under- and overvoltage Distance back-up

L90 Current Differential Relay: Features
Control: Breaker Failure (phase/neutral amps) Synchrocheck & Autoreclosure Direct messaging (8 extra inter-relay DTT bits exchanged) Metering: Fault Locator Oscillography Event Recorder Data Logger Phasors / true RMS / active, reactive and apparent power, power factor

L90 Current Differential Relay: Overview
Direct point-to-point Fiber (up to 70Km) (64Kbps) - G.703 - RS422 OR - G.703 - RS422 Via SONET system telecom multiplexer (GE’s FSC) (155Mbps) FSC (SONET) FSC (SONET)

L90 Current Differential Relay: Line Current Differential
Improved operation of the line current differential (87L) element: dynamic restraint increasing security without jeopardizing sensitivity line charge current compensation to increase sensitivity self-synchronization

L90 Current Differential Relay: Traditional Restraint Method
Restraint Current Operate Current K1 K2 Traditional method is STATIC Compromise between Sensitivity and Security

L90 Current Differential Relay: Dynamic Restraint
Dynamic restraint uses an estimate of a measurement error to dynamically increase the restraint On-line estimation of an error is possible owing to digital measuring techniques In digital relaying to measure means to calculate or to estimate a given signal feature such as magnitude from the raw samples of the signal waveform

L90 Current Differential Relay: Digital Phasor Measurement
The L90 measures the current phasors (magnitude and phase angle) as follows: digital pre-filtering is applied to remove the decaying dc component and a great deal of high frequency distortions the line charging current is estimated and used to compensate the differential signal full-cycle Fourier algorithm is used to estimate the magnitude and phase angle of the fundamental frequency (50 or 60Hz) signal

Sliding Data Window present time window time time waveform magnitude

Sliding Data Window window window window window window window window window time time waveform magnitude

L90 Current Differential Relay: Goodness of Fit
A sum of squared differences between the actual waveform and an ideal sinusoid over last window is a measure of a “goodness of fit” (a measurement error) window time

L90 Current Differential Relay: Phasor Goodness of Fit
The goodness of fit is an accuracy index for the digital measurement The goodness of fit reflects inaccuracy due to: transients CT saturation inrush currents and other signal distortions The goodness of fit is used by the L90 to alter the traditional restraint signal (dynamic restraint)

L90 Current Differential Relay: Operate-Restraint Regions
ILOC – local current IREM – remote end current Imaginary (ILOC/IREM) Real (ILOC/IREM) OPERATE RESTRAINT

L90 Current Differential Relay: Dynamic Restraint
Dynamic restraint signal = Traditional restraint signal + Error factor Imaginary (ILOC/IREM) OPERATE Error factor is high Real (ILOC/IREM) REST. Error factor is low

L90 Current Differential Relay: Charge Current Compensation
The L90 calculates the instantaneous values of the line charging current using the instantaneous values of the terminal voltage and shunt parameters of the line The calculated charging current is subtracted from the actually measured terminal current The compensation reduces the spurious differential current and allows for more sensitive settings

L90 Current Differential Relay: Charge Current Compensation
The compensating algorithm: is accurate over wide range of frequencies works with shunt reactors installed on the line works in steady state and during transients works with both wye- and delta-connected VTs (for delta VTs the accuracy of compensation is limited)

L90 Current Differential Relay: Effect of Compensation
Local and remote voltages Voltage, V time, sec

Traditional and compensated differential currents (waveforms) Current, A time, sec

Traditional and compensated differential currents (magnitudes) Current, A time, sec

L90 Current Differential Relay: Self-Synchronization
Forward travel time tf t1 Relay turn-around time “ping-pong” t2 Return travel time tr t3

L90 Current Differential Relay: Ping-Pong (example)
Send start bit Store T1i-3=0 Initial clocks mismatch=1.4ms or 30° Communication path Send start bit Store T2i-3=0 8.33 ms Capture T2i-2=2.3 5.1 2.3 Capture T1i-2=5.1 8.33 ms Send T1i-2=5.1 8.33 8.33 Send T2i-2=2.3 8.33 ms Store T1i-2=5.1 13.43 10.53 Store T2i-2=2.3 8.33 ms Send T1i-1=16.66 16.66 16.66 Send T2i-1=16.66 8.33 ms Store T1i-1=8.33 Capture T2i=18.96 21.76 Store T2i-1=8.33 Capture T1i=21.76 18.96 T2i-3=0 T1i-2=5.1 T1i-1=16.66 T2i=18.96 a2=5.1-0=5.1 b2= =2.3 2=( )/2= = +1.4ms (behind) T1i-3=0 T2i-2=2.3 T2i-1=16.66 T1i=21.76 a1=2.3-0=2.3 b1= =5.1 1=( )/2= = -1.4ms (ahead) Speed up Slow down 30° 0° t1 t2

L90 Current Differential Relay: Ping-Pong (example cnt.)
33.32 Store T1i-3=33.32 33.32 Store T2i-3=33.32 8.52 ms Capture T2i-2=35.62 38.28 35.62 Capture T1i-2=38.28 8.14 ms 41.55 Send T1i-2=38.28 41.55 Send T2i-2=35.62 8.52 ms Store T1i-2=38.28 Store T2i-2=35.62 8.14 ms Send T1i-1=50.00 50.00 49.93 Send T2i-1=49.93 8.52 ms 53.16 54.03 Store T1i-1=50.00 Capture T2i=53.16 Store T2i-1=49.93 Capture T1i=54.03 8.14 ms T2i-3=33.32 T1i-2=38.28 T1i-1=50.00 T2i=53.16 a2= =4.96 b2= =3.16 2=( )/2= = +0.9ms (behind) T1i-3=33.32 T2i-2=35.62 T2i-1=49.93 T1i=54.03 a1= =2.3 b1= =4.1 1=( )/2= = -0.9ms (ahead) Speed up Slow down 0° 19.5° 30° t1 t2

L90 Current Differential Relay: Digital “Flywheel”
“Virtual Shaft” clock 1 clock 2 If communications is lost, sample clocks continue to “free wheel” Long term accuracy is only a function of the base crystal stability

L90 Current Differential Relay: Peer-to-Peer Operation
Each relay has sufficient information to make an independent decision Communication redundancy L90-1 L90-2 L90-3

L90 Current Differential Relay: Master-Slave Operation
At least one relay has sufficient information to make an independent decision The deciding relay(s) sends a transfer-trip command to all other relays L90-1 L90-2 L90-3 Data (currents) Transfer Trip

L90 Current Differential Relay: Benefits
Increased Sensitivity without sacrificing Security: Fast operation (11.5 cycles) Lower restraint settings / higher sensitivity Charging current compensation Dynamic restraint ensures security during CT saturation or transient conditions Reduced CT requirements Direct messaging Increased redundancy due to master-master configuration

L90 Current Differential Relay: Benefits
Self-Synchronization: No external synchronizing signal required Two or three terminal applications Communication path delay adjustment Redundancy for loss of communications Benefits of the UR platform (back-up protection, autoreclosure, breaker failure, metering and oscillography, event recorder, data logger, FlexLogicTM, fast peer-to-peer communications)

D60 Line Distance Relay

D60 Line Distance Relay: Features
Protection: Four zones of distance protection Pilot schemes Phase/Neutral/Ground TOCs Phase/Neutral/Ground IOCs Negative sequence TOC Negative sequence IOC Phase directional OCs Neutral directional OC Negative sequence directional OC

Protection (continued): Phase under- and overvoltage Power swing blocking Out of step tripping Control: Breaker Failure (phase/neutral amps) Synchrocheck Autoreclosure

Metering: Fault Locator Oscillography Event Recorder Data Logger Phasors / true RMS / active, reactive and apparent power, power factor

D60 Line Distance Relay: Stepped Distance
Four zones of stepped distance: individual per-zone per-element characteristic: dynamic memory-polarized mho quadrilateral individual per-zone per-element current supervision multi-input phase comparator: additional ground directional supervision dynamic reactance supervision all 4 zones reversible excellent transient overreach control

D60 Line Distance Relay: Zone 1 and CVT transients
Capacitive Voltage Transformers (CVTs) create certain problems for fast distance relays in conjunction with high Source Impedance Ratios (SIRs): the CVT induced transient voltage components may assume large magnitudes (up to about 30-40%) and last for a comparatively long time (up to about 2 cycles) the 60Hz voltage for faults at the relay reach point may be as low as 3% for a SIR of 30 the signal is buried under the noise

Sample CVT output voltages (the primary voltage drops to zero) Illustration of the signal-to-noise ratio

CVTs cause distance relays to overreach Generally, transient overreach may be caused by: overestimation of the current (the magnitude of the current as measured is larger than its actual value, and consequently, the fault appears closer than it is actually located), underestimation of the voltage (the magnitude of the voltage as measured is lower than its actual value) combination of the above

Estimated voltage magnitude does not seem to be underestimated 2.2% of the nominal = 70% of the actual value

Impedance locus may pass below the origin of the Z-plane - this would call for a time delay to obtain stability

Transient overreach due to CVTs - solutions: apply delay (fixed or adaptable) reduce the reach adaptive techniques and better filtering algorithms

Actual maximum reach curves D60 Relay S Relay A Relay D

D60 Solution: Optimal signal filtering currents - max 3% error due to the dc component voltages - max 0.6% error due to CVT transients Adaptive double-reach approach the filtering alone ensures maximum transient overreach at the level of 1% (for SIRs up to 5) and 20% (for SIRs up to 30) to reduce the transient overreach even further an adaptive double-reach zone 1 has been implemented

The outer zone 1: is fixed at the actual reach applies certain security delay to cope with CVT transients The inner zone 1: has its reach dynamically controlled by the voltage magnitude is instantaneous

No Trip Set reach Delayed Trip Instantaneous Trip

Multiplier for the inner zone 1 reach, pu Element’s Voltage, pu

Performance: excellent transient overreach control (5% up to a SIR of 30) no unnecessary decrease in speed

D60 Line Distance Relay: Zone 1 Speed

D60 Line Distance Relay: Pilot Schemes
Pilot Schemes available: Direct Underreaching Transfer Trip (DUTT) Permissive Underreaching Transfer Trip (PUTT) Permissive Overreaching Transfer Trip (POTT) Hybrid Permissive Overreaching Transfer Trip (HYB POTT) Blocking Scheme

D60 Line Distance Relay: Pilot Schemes
Pilot Schemes - Features: integrated functions : weak infeed echo line pick-up basic protection elements used to key the communication: distance elements fast and sensitive ground (zero- and negative sequence) directional IOCs with current/voltage/dual polarization

D60 Line Distance Relay: Benefits
Excellent CVT transient overreach control (without unnecessary decrease in speed) Fast, sensitive and accurate ground directional OCs Common pilot schemes Benefits of the UR platform (back-up protection, autoreclosure, breaker failure, metering and oscillography, event recorder, data logger, FlexLogicTM, fast peer-to-peer communications)

T60 Transformer Management Relay
Universal Relay Family T60 Transformer Management Relay

T60 Transformer Management Relay: Features
Protection: Restrained differential Instantaneous differential overcurrent Restricted ground fault Phase/Neutral/Ground TOCs Phase/Neutral/Ground IOCs Phase under- and overvoltage Underfrequency

T60 Transformer Management Relay: Features
Metering: Oscillography Event Recorder Data Logger Phasors / true RMS / active, reactive and apparent power, power factor

T60 Transformer Management Relay: Restrained differential
Internal ratio and phase compensation Dual-slope dual-breakpoint operating characteristic Improved dynamic second harmonic restraint for magnetizing inrush conditions Fifth harmonic restraint for overexcitation conditions Up to six windings supported

T60 Transformer Management Relay: Differential Signal
Removal of the zero sequence component from the differential signal: optional for delta-connected windings enables the T60 to cope with in-zone grounding transformers and in-zone cables with significant zero-sequence charging currents Removal of the decaying dc component Full-cycle Fourier algorithm for measuring both the differential current phasor and the second and fifth harmonics

T60 Transformer Management Relay: Restraining Signal
Removal of the decaying dc component Full-cycle Fourier algorithm for measuring the magnitude “Maximum of” principle used for deriving the restraining signal from the terminal currents: the magnitude of the current flowing through a CT that is more likely to saturate is used

T60 Transformer Management Relay: Operating Characteristic
Two slopes used to cope with: small errors during linear operation of the CTs (K1) and large CT errors (saturation) for high through currents (K2)

T60 Transformer Management Relay: Operating Characteristic
Two breakpoints used to specify: the safe limit of linear CT operation (B1) and the minimum current level that may cause large spurious differential signals due to CT saturation (B2)

T60 Transformer Management Relay: Magnetizing Inrush
Sample magnetizing inrush current Second harmonic ratio

T60 Transformer Management Relay: Magnetizing Inrush
New second harmonic restraint: uses both the magnitude and phase relation between the second harmonic and the fundamental frequency (60Hz) component Implementation issues: the second harmonic rotates twice as fast as the fundamental component (60Hz) consequently the phase difference between the second harmonic and the fundamental component changes in time...

T60 Transformer Management Relay: New Inrush Restraint
Fundamental phasor 2nd harmonic Solution:

3D View Inrush Pattern

3D View Internal Fault Pattern

Basic Operation: if the second harmonic drops magnitude-wise below 20%, the phase angle of the complex second harmonic ratio is close to either +90 or -90 degrees during inrush conditions the phase angle may not display the 90-degree pattern if the second harmonic ratio is above some 20% if the second harmonic ratio is above 20% the restraint is in effect, if it is below - the restraint and its duration depend on the phase angle

New restraint characteristic The characteristic is dynamic

Effective restraint characteristic: time (cycles) the restraint is kept vs. complex second harmonic ratio

Effective restraint characteristic: time for which the restraint is kept vs. complex second harmonic ratio 3D View

T60 Transformer Management Relay: Benefits
Up to six windings supported Improved transformer auto-configuration Improved dual-slope differential characteristic Improved second harmonic restraint Benefits of the UR platform (back-up protection,metering and oscillography, event recorder, data logger, FlexLogicTM, fast peer-to-peer communications)

B30 Bus Differential Relay
Universal Relay Family B30 Bus Differential Relay

B30 Bus Differential Relay: Features
Configuration: up to 5 feeders with bus voltage up to 6 feeders without bus voltage

Protection: Biased differential protection CT saturation immunity typical trip time < 15 msec dynamic 1-out-of-2 or 2-out-of-2 operation Unbiased differential protection CT trouble

Metering: Oscillography Event Recorder Data Logger Phasors / true RMS active, reactive and apparent power, power factor (if voltage available)

B30 Bus Differential Relay: CT saturation problem
During an external fault the fault current may be supplied by a number of sources the CTs on the faulted circuit may saturate Saturation of the CTs creates a current unbalance and violates the differential principle The conventional restraining current may not be sufficient to prevent maloperation CT saturation detection and other operating principles enhance the through-fault stability

B30 Bus Differential Relay: DIF-RES trajectory
DIF – differential RES – restraining External fault: ideal CTs

External fault: ratio mismatch

External fault: CT saturation

Internal fault: high current

Internal fault: low current

External fault: extreme CT saturation

B30 Bus Differential Relay: Operating principles
Combination of Low-impedance biased differential Directional (phase comparison) Adaptively switched between 1-out-of-2 operating mode 2-out-of-2 operating mode by Saturation Detector

B30 Bus Differential Relay: Two operating zones
low currents saturation possible due to dc offset saturation very difficult to detect more security required

B30 Bus Differential Relay: Two operating zones
large currents quick saturation possible due to large magnitude saturation easier to detect security required only if saturation detected

B30 Bus Differential Relay: Logic
AND OR TRIP DIR OR AND SAT DIF2

B30 Bus Differential Relay: Directional principle
Internal faults - all currents approximately in phase

External faults - one current approximately out of phase

Check all the angles Select the maximum current contributor and check its position against the sum of all the remaining currents Select major current contributors and check their positions against the sum of all the remaining currents

B30 Bus Differential Relay: Saturation Detector
differential-restraining trajectory dI/dt

Sample External Fault (Feeder 1)

Analysis of the DIF-RES trajectory enables the B30 to detect CT saturation

Sample External Fault (Feeder 4) - severe CT saturation after 1.5msec

dI/dt principle enables the B30 to detect CT saturation

Operation: The SAT flag WILL NOT set during internal faults whether or not the CT saturates The SAT flag WILL SET during external faults whether or not the CT saturates The SAT flag is NOT used to block the relay but to switch to 2-out-of-2 operating principle

B30 Bus Differential Relay: Benefits
Sensitive settings possible Very good through-fault stability Fast operation (less than 3/4 of a cycle) Benefits of the UR platform (back-up protection,metering and oscillography, event recorder, data logger, FlexLogicTM, fast peer-to-peer communication)

B30 Bus Differential Relay: Extensions
6 feeders fast communication 6 feeders 6 feeders

F60 Feeder Management Relay
Universal Relay Family F60 Feeder Management Relay

F60 Feeder Relay: Features
Protection: Phase/Neutral/Ground IOC & TOC Phase TOC with Voltage Restraint/Supervision Negative sequence IOC & TOC Phase directional supervision Neutral directional overcurrent Negative sequence directional overcurrent Phase undervoltage & overvoltage Underfrequency Breaker Failure (phase/neutral supervision)

F60 Feeder Relay: Features
Control: Manually Control up to Two Breakers Autoreclosure & Synchrocheck FlexLogic Metering: Fault Locator Oscillography Event Recorder Data Logger Phasors / true RMS / active, reactive and apparent power, power factor, frequency

F60 Feeder Relay: Phase Directional Element
Directional element controls the RUN command of the overcurrent element (emulation of “torque control”) Memory voltage polarization held for 1 second

F60 Feeder Relay: Neutral Directional Element
Single protection element providing both forward and reverse looking IOC Independent settings for the forward and reverse elements Voltage, current or dual polarization Fast and secure operation due to the energy based comparator and positive sequence restraint

F60 Feeder Relay: Ground Directional Elements
Limitations of Fast Ground Directional IOCs: Spurious zero- and negative-sequence voltages and currents may appear transiently due to the dynamics of digital measuring algorithms Magnitude of such spurious signals may reach up to 25% of the positive sequence quantities Phase angles of such spurious signals are random factors Combination of the above may cause maloperations

Sample three-phase fault currents

Sample three-phase fault currents (phasors) -10 -5 5 10 Fault phasors (symmetrical) Transient phasors (slightly asymmetrical) Transient phasors (slightly asymmetrical) Imaginary Pre-fault phasors (symmetrical) Real

Sample three-phase currents (symmetrical components) Positive Sequence Zero Sequence Negative Sequence

Solutions to the problem of spurious zero and negative sequence quantities: do not allow too sensitive settings apply delay new approach: energy based comparator positive sequence restraint

Operating “power” is calculated as a function of: magnitudes of the operating and polarizing signals the angle between the operating and polarizing signals in conjunction with the characteristic and limit angles Restraining “power” is calculated as a product of magnitudes of the operating and restraining signals

The “powers” are averaged over certain short period of time creating the operating and restraining “energies” The element operates when Both “forward” and “reverse” operating energies are calculated The factor K is lower for the reverse looking element to ensure faster operation

Forward looking element Restraining Energy Reverse looking element Operating Energy Operating Energy Despite spurious negative sequence neither the forward nor the reverse looking element maloperate Restraining Energy

Positive Sequence Restraint: Classical Negative Sequence IOC: Positive Sequence Restrained Negative Sequence IOC: K1 = 1/8 for negative sequence IOC K1 = 1/16 for zero sequence IOC

F60 Feeder Relay: Negative Sequence Directional Element
Single protection element providing both forward and reverse looking IOC Independent settings for the forward and reverse elements Mixed operating mode available: Negative Sequence IOC / Negative Sequence Directional Zero Sequence IOC / Negative Sequence Directional Energy based comparator and positive sequence restraint

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