Copyright © SEL 2010

Advancements in Transmission Line Protection and Fault Location

Brian Smyth

Lead Product Engineer

Today’s Focus

• Need for better line protection

• Multiterminal 87L over Ethernet

• Using time in critical applications

• Traveling wave fault location

• Validating complex protection schemes

Line Protection Challenges

• Stressed power systems demand more from protection

• Transient stability margins

• Unusual system conditions

• 87L schemes address many problems

Multiterminal SEL-411L Over Ethernet

Multiterminal 87L SchemesImplementation Requirements

• Communication of current signals

♦ One-to-many data transmission

♦ Many-to-one data reception

• Current data alignment

• Algorithm suitable for multicurrent differential zones

Traditional Three-Terminal Scheme

87L(1)

87L(2)

87L(3)

87L(1)

87L(2)

87L(3)

Traditional Three-Terminal Scheme

PORT 1

PORT 2

PORT 1

PORT 2

PORT 1 PORT 2

CHANNEL 1

CHANNEL 2 CHANNEL 3

Multiterminal Alpha Plane

CT-5 CT-6T3

CT-1

CT-2

T1

CT-3

CT-4

T2

IDIF(N)

IRST(N)

I3

I2

I1

I4IN

IDIF(2)

IRST(2)

IL EQ

IR EQ

IL EQ IR EQ

IL EQ

k = IR EQ

Faults on 87L Alpha Plane

0 180

InternalExternal

Multiterminal Alpha Plane

ILQ EQ

IRQ EQ

ILQ EQIRQ EQ

Im(k)

Re (k)

Four-Terminal Scheme

87L(1)

87L(2)

87L(3)

87L(4)

Four-Terminal SchemePoint-to-Point Serial?

Impractical• Number of ports and channels• Data alignment challenges

87L(1)

87L(2)

87L(3)

87L(4)

Terminals Ports Channels3 2 34 3 65 4 106 5 15

Four-Terminal SchemeEthernet With Dedicated Fiber

87L(1)

87L(2)

87L(3)

87L(4)

SWITCHSWITCH

SWITCH SWITCH

• All relays receive all remote data• Dedicated fiber between switches• Isolated Layer 2 Ethernet network• Optionally, a ring for fiber redundancy

SEL-411L Implementation

• Dedicated Ethertype from IEEE

• Layer 2 Ethernet

• VLAN for multiple 87L schemes

• Extra data integrity (Ethernet CRC)

• MAC addresses to identify relays in the same scheme

SONET RING

MultiplexerMultiplexer

Multiplexer Multiplexer

Four-Terminal SchemeEthernet Over Protection-Class SONET

87L(1)

87L(2)

87L(3)

87L(4)

• All relays receive all data• Relay to multiplexer over Ethernet• TDM between multiplexers• Advantages of SONET

87L Serial vs. Ethernet Over ICON

• Point-to-point between relay and multiplexer

• One physical connection per terminal

• ICON maps serial circuits between sites

• One point-to-point connection between relay and multiplexer

• ICON delivers packets based on VLAN

SEL ICONMultiplexer

SEL-411L

IEEE C37.94, EIA-422

TDM

SEL ICONMultiplexer

SEL-411L

Ethernet

TDM

87L Algorithm for Multiterminal Applications

• Tried-and-true Alpha Plane

• Generalized Alpha Plane to handle any number of currents

• External fault detection for CT saturation

• Charging current compensation

• In-line transformers

Technical paper “Tutorial on Operating Characteristics of Microprocessor-Based Multiterminal Line Current Differential Relays”

SEL-411L With 87L Over Ethernet

• Applicable with♦ Isolated network

with dedicated fiber

♦ Deterministic Ethernet over ICON

• Allows four-terminal applications

• Natural extension of serial applications

• Requires time for current alignment

Using Time in Critical Power System Applications

Time in Critical Applications

• Wide-area time needed for

♦ Line current differential

♦ Synchrophasors

♦ Multiended fault locators

• Need for robust time source and distribution

• Coherent time despite GPS problems

SONETTime Source and Distribution

• SONET keeps all multiplexers tightly synchronized

• ICON integrates GPS receivers

• GPS receivers act as redundant time inputs

• ICON provides coherent time across the network

Time Over ICONSimplicity

Service Module Line Module

GPS Antenna Input

IRIG-B Outputs

IRIG-B Input

IEEE 1588 Timing Protocol (Future)

Advanced Time Synchronization

• SEL-2488 GPS Clock

• Need a good holdover state to be reliable

• TCXO = 36us/day

• OCXO = 5us/day

Traveling Wave Fault Location

2 11

d L v • t t2

2 1L 2d v • t t

Traveling Wave Fault LocationPrinciple of Operation

L - 2d

t2

d

t1

d

t1

Extracting the Waves

0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34 0.36 0.38 0.4

-6000

-4000

-2000

0

2000

4000

6000

0.298 0.299 0.3 0.301 0.302 0.303 0.304 0.305-3000

-2000

-1000

0

1000

2000

3000

0.298 0.299 0.3 0.301 0.302 0.303 0.304 0.305-100

-50

0

50

100

150

10 kHz to 0.6 MHz

DC to 0.6 MHz

Traveling Wave Fault Locators (TWFLs)

• Accurate

♦ Down to a tower span

♦ Regardless of line length

♦ On series-compensated and coupled lines

• Immune to limitations of other methods

♦ Fault resistance and infeed effect

♦ Changing fault resistance

♦ Not enough data due to fast fault clearance

SEL Designed a TWFL Before ...

Dr. Schweitzer’s work in the mid-1980s for Bonneville Power Administration (dc lines)

SEL-411L Implementation

• Current-based

• Double-ended, using arrival times

• 87L channel to exchange time stamps

• Built-in traveling wave oscillography

• In parallel with impedance-based fault locator

TWFL Feasibility in Protective Relays

CT Primary

CT Secondary

CAL Board Output

10 s

SEL-411L TWFL Hardware

• 6 channels

• Sampling at 1.5625 MHz each

Traveling Wave Oscillography

Field Experience

• 72.78-mile 161 kV line at BPA (Goshen-Drummond)

• 18 sections with 4 different tower configurations

Event on April 24, 2012 60 Hz View

Event on April 24, 2012 Traveling Wave View

Event onApril 24, 2012

Front Wave

Event on April 24, 2012Fault Location Results

Method Miles From GoshenTwo-End Traveling Wave (SEL-411L) 68.181Two-End Impedance 66.03Single-End Impedance Relay 1 64.05Single-End Impedance Relay 2 64.15

“Using this information we asked the line crew to go to 68.181 miles and they found the flashed insulator at 68.242 miles. This was within one tower off where we said to look. The first span from 68 mile is 551 feet, the second span is 725 feet. Picture of the April 24th flashover attached.”

—Stephen Marx, BPA

Event on April 24, 2012Flashed Over Insulator

Few More Examples

Event Fault Location (Actual)

Fault Location (SEL-411L)

Flashover 68.242 mi 68.181 mi

Insulator Damage 38.398 mi 38.426 mi

Lightning Strike Under Investigation 67.76 mi

Lightning Strike Insulator Damage

Questions?