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**Fault Location EE 526 Venkat Mynam Senior Research Engineer Schweitzer Engineering Laboratories**

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**Accurate Fault Location is Critical**

Expedite Service Restoration Reduce outage times Identify insulator problems Prevent potential recurring faults Verify Protective Relay Performance

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**Permanent Fault Need Immediate Attention**

We need accurate fault location

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**Temporary Faults Needs Attention Too**

Identify & Fix Damaged Insulators-Minimize Fault Recurrence

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**Hard to Find a Flashed Insulator**

Fault location investigations

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Finding Faults

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Visual Methods

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**Estimate Location From Current**

“JM Drop” circa 1936 Approximate fault location was calculated based on system and line parameters

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**Methods in Use Line impedance Based Traveling Wave Based**

Measure impedance to fault Compare it to the actual line impedance Traveling Wave Based Measure wave arrival time

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**System One-Line and Circuit Representation of System Fault**

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**Modified Takagi Method-Single Ended (Negative Sequence)**

Multiply by I2 and save Imaginary part Zero For: Rf=0 or system is homogeneous

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**IEEE Guide Defines Homogeneous System**

“A transmission system where the local and remote source impedances have the same angle as the line impedance”

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**Single End Impedance Method**

Accuracy of zero-sequence line impedance Effect of zero-sequence mutual coupling from parallel lines Time synchronization Communication Radial topology Fault resistance System nonhomogeneity Accuracy of measurements Accuracy of positive-sequence line impedance

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**SE Impedance Fault Location Phase-Ground Faults**

𝑚𝐴𝐺= 𝐼𝑚 𝑉𝐴𝐺∙ 𝐼 2 𝑎 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐴𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2 𝑎 ∗ 𝑚𝐵𝐺= 𝐼𝑚(𝑉𝐵𝐺∙ 𝐼 2 𝑏 ∗ ) 𝐼𝑚(𝑍1𝐿∙(𝐼𝐵𝐺+𝑘0∙𝐼𝐺)∙ 𝐼 2 𝑏 ∗ ) 𝑚𝐶𝐺= 𝐼𝑚 𝑉𝐶𝐺∙ 𝐼 2 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐶𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2 𝑐 ∗ 𝐼 2 𝑏 =𝑎∙𝐼 2 𝑎 𝐼 2 𝑐 = 𝑎 2 ∙𝐼 2 𝑎

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**SE Impedance Fault Location Multi-Phase Faults**

𝑚𝐴𝐵= 𝐼𝑚 𝑉𝐴𝐵∙ 𝑗∙𝐼 2 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ 𝑗∙𝐼 2 𝑐 ∗ 𝑚𝐵𝐶= 𝐼𝑚 𝑉𝐵𝐶∙ (𝑗∙𝐼 2 𝑎 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ (𝑗∙𝐼 2 𝑎 ) ∗ 𝑚𝐶𝐴= 𝐼𝑚 𝑉𝐶𝐴∙ (𝑗∙𝐼 2 𝑏 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐶𝐴∙ (𝑗∙𝐼 2 𝑏 ) ∗ 𝑚3𝑃= 𝐼𝑚 𝑉∅∅∙ 𝐼∅∅ ∗ 𝐼𝑚 𝑍1𝐿∙𝐼∅∅∙ 𝐼∅∅ ∗ 𝐼 2 𝑏 =𝑎∙𝐼 2 𝑎 𝐼 2 𝑐 = 𝑎 2 ∙𝐼 2 𝑎

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**Fault Loop Selection and Reporting**

Select appropriate Fault Loop Report a single fault location value Select a window of data from the fault data Provide the average value of fault location computed from the selected window

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**Modified Takagi Method-Multi Ended (Using Remote terminal current)**

Multiply by I2 and save Imaginary part THIS IS ZERO

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**Multi-End I2 Total Current**

Fault resistance System nonhomogeneity Accuracy of measurements Accuracy of positive-sequence line impedance Accuracy of zero-sequence line impedance Effect of zero-sequence mutual coupling from parallel lines Time synchronization Communication

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**ME_I Impedance Fault Location Phase-Ground Faults**

𝑚𝐴𝐺= 𝐼𝑚 𝑉𝐴𝐺∙ 𝐼 2𝑇 𝑎 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐴𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2𝑇 𝑎 ∗ 𝑚𝐵𝐺= 𝐼𝑚(𝑉𝐵𝐺∙ 𝐼 2𝑇 𝑏 ∗ ) 𝐼𝑚(𝑍1𝐿∙(𝐼𝐵𝐺+𝑘0∙𝐼𝐺)∙ 𝐼 2𝑇 𝑏 ∗ ) 𝑚𝐶𝐺= 𝐼𝑚 𝑉𝐶𝐺∙ 𝐼 2𝑇 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐶𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2𝑇 𝑐 ∗ 𝐼 2𝑇 𝑏 =𝑎∙𝐼 2𝑇 𝑎 𝐼 2𝑇 𝑐 = 𝑎 2 ∙𝐼 2𝑇 𝑎 𝐼2𝑇=𝐼2𝐿𝑜𝑐𝑎𝑙+𝐼2𝑅𝑒𝑚𝑜𝑡𝑒

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**ME Impedance Fault Location Multi-Phase Faults**

𝑚𝐴𝐵= 𝐼𝑚 𝑉𝐴𝐵∙ 𝑗∙𝐼 2𝑇 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ 𝑗∙𝐼 2𝑇 𝑐 ∗ 𝑚𝐵𝐶= 𝐼𝑚 𝑉𝐵𝐶∙ (𝑗∙𝐼 2𝑇 𝑎 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ (𝑗∙𝐼 2𝑇 𝑎 ) ∗ 𝑚𝐶𝐴= 𝐼𝑚 𝑉𝐶𝐴∙ (𝑗∙𝐼 2𝑇 𝑏 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐶𝐴∙ (𝑗∙𝐼 2𝑇 𝑏 ) ∗ 𝑚3𝑃= 𝐼𝑚 𝑉∅∅∙ 𝐼∅∅𝑇 ∗ 𝐼𝑚 𝑍1𝐿∙𝐼∅∅∙ 𝐼∅∅𝑇 ∗ 𝐼 2𝑇 𝑏 =𝑎∙𝐼 2𝑇 𝑎 𝐼 2𝑇 𝑐 = 𝑎 2 ∙𝐼 2𝑇 𝑎 𝐼2𝑇=𝐼2𝐿𝑜𝑐𝑎𝑙+𝐼2𝑅𝑒𝑚𝑜𝑡𝑒 𝐼∅∅𝑇 =𝐼∅∅𝐿𝑜𝑐𝑎𝑙+𝐼∅∅𝑅𝑒𝑚𝑜𝑡𝑒

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**Multi Ended Negative Sequence Using Remote terminal voltage and current**

ref V2F +

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**Use Synchronized Measurements to Calculate Voltage at Fault Point**

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** Double End With V2 and I2**

Fault resistance System nonhomogeneity Accuracy of measurements Accuracy of positive-sequence line impedance Accuracy of zero-sequence line impedance Effect of zero-sequence mutual coupling from parallel lines Time synchronization Communication

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**Multi-End Fault Location That Does Not Require Data Alignment**

Each Relay Receives: Magnitude and Angle of Z2R ½I2R½

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**Local and Remote Data Necessary for Fault Location**

Rearrange Above Equation to Form a Quadratic Equation Solve Quadratic for Fault Location m Download Paper

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**Multi-End Methods Needs Time Synchronized Data**

Synchrophasors Synchronized samples Devices with data acquisition synchronized to a common time source Fixed sampling rate

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**Series Compensated Lines**

Line Side PT Bus Side PT Challenges Steady State Transient (phasor estimate is not stable) Subsynchronous MOV and bypass breaker switching Download Paper

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Three-Terminal Line

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**Reduce From Three-Terminal Line to Two-Terminal Equivalent**

V2_SP = V2S – Z2L_SP • I2S V2_TP = V2T – Z2L_TP • I2T Same Result V2_UP = V2U – Z2L_UP • I2U

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**Use Two-Terminal Equivalent to Solve for m**

I2_Eq = I2T + I2U V2_Eq = V2_TP Solve for m using SE or Multi-terminal (ME_I, ME) ME_I

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**Mutually Coupled Lines**

Download Paper

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**Composite Lines Identifies faulted line section**

Calculates distance to fault

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**Intersection of Voltage Profiles Identifies Faulted Section**

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**Calculate Distance to Fault Within Faulted Section using ME method**

Download Paper

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**Impedance Method Approach Summary**

Measure VA, VB, VC, IA, IB, IC Extract fundamental components Determine phasors and fault type Apply impedance algorithm

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**Impedance Fault Location Methods**

Single-End Method using local voltage and currents SE Multi-End Method using local voltage and currents, and remote currents MEI Multi-End Method using local and remote voltage and currents ME

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**Some of the Challenging Situations for Z based Fault Location Methods**

Short faults: faster relays and breakers- phasor estimate is not stable Faults associated with time-varying fault resistance-phasor estimate is not stable Series compensation

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**Short Duration Faults Raw-Blue, Cosine Filtered-Green**

Magnitude of Filtered Quantity-Red

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**Lightning and Faults Launch Traveling Waves**

tL tR Download Paper

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**Double Ended TW Fault Location**

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**Single-End TW Fault Locator**

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**Image courtesy of Google**

Results From Field 117.11km, 161 kV line 18 sections with 4 different tower configurations Challenges with existing impedance based fault location methods Image courtesy of Google

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**Fault Location Results (161kV, 117.11km long line)**

TW Patrol SE_Z ME_Z_I ME_Z CG 109.74 109.29 105.44 106.24 106.56 BG 61.12 61.41 54.75 60.69 60.70 108.23 107.60 101.59 106.43 98.85 98.98 95.20 98.37

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**Temporary Fault Due to Insulator Flashover**

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Insulator Flashover

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