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 Schemes Implementation 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

Multiterminal Alpha Plane

Faults on 87L Alpha Plane  0 0  180  InternalExternal Multiterminal Alpha Plane I LQ EQ I RQ EQ I LQ EQ I RQ EQ

Four-Terminal Scheme

Four-Terminal Scheme Point-to-Point Serial? Impractical Number of ports and channels Data alignment challenges TerminalsPortsChannels

Four-Terminal Scheme Ethernet With Dedicated Fiber 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

Four-Terminal Scheme Ethernet Over Protection-Class SONET 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

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

SONET Time 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 ICON Simplicity Service ModuleLine 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

Traveling Wave Fault Location Principle of Operation

Extracting the Waves 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 MHz each

Traveling Wave Oscillography

Field Experience mile 161 kV line at BPA (Goshen- Drummond) 18 sections with 4 different tower configurations

Event on April 24, Hz View

Event on April 24, 2012 Traveling Wave View

Event on April 24, 2012 Front Wave

Event on April 24, 2012 Fault Location Results MethodMiles From Goshen Two-End Traveling Wave (SEL-411L) Two-End Impedance66.03 Single-End Impedance Relay Single-End Impedance Relay “Using this information we asked the line crew to go to miles and they found the flashed insulator at 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, 2012 Flashed Over Insulator

Few More Examples Event Fault Location (Actual) Fault Location (SEL-411L) Flashover mi mi Insulator Damage mi mi Lightning StrikeUnder Investigation67.76 mi Lightning Strike Insulator Damage

Questions?