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Use of Phasors for
Fault Location
Presenter: Armando Maldonado
Instructor: Dr. Mladen Kezunovic Ph.D.
Course: ECEN 679 Computer Relays
Single Ended Protection
Relay Protection, voltage and current inputs at one end of transmission line.
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Fault type must be determined prior to fault location algorithm
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Algorithm calculates inductance from relay location to fault
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Fault Impedance = errors
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Load flow = errors
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Zero Sequence mutual coupling = errors
Single Ended Protection
Reduce the effect of fault resistance and load flow to combat errors.
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Voltage/Current phasors computed by Discrete Fourier Transforms
𝐴𝑠𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛
𝑅𝑓𝐿 = 𝑟𝑒𝑎𝑙 𝑟𝑒𝑠𝑖𝑠𝑡𝑖𝑣𝑒 𝑐𝑜𝑚𝑝𝑜𝑛𝑒𝑛𝑡; 𝑖𝑓 𝑐𝑢𝑟𝑟𝑒𝑛𝑡𝑠 𝐼𝑓𝐿 𝑎𝑛𝑑 𝐼𝑓𝑅 𝑎𝑟𝑒 𝑖𝑛 𝑝ℎ𝑎𝑠𝑒(ℎ𝑜𝑚𝑜𝑔𝑒𝑛𝑒𝑜𝑢𝑠)
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Separate into real and imaginary components
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Multiply equations with 𝐼𝑓𝐿 𝑟𝑒𝑎𝑙 𝑎𝑛𝑑 𝑖𝑚𝑎𝑔𝑖𝑛𝑎𝑟𝑦
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Subtract real from imaginary equations and solve for “n”
𝐼𝐿 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑠𝑖𝑔𝑛𝑎𝑙 𝑝𝑟𝑜𝑐𝑒𝑠𝑠𝑒𝑑 𝑏𝑦 𝑑𝑖𝑔𝑖𝑡𝑎𝑙 𝑚𝑖𝑚𝑖𝑐 𝑎𝑙𝑔𝑜𝑟𝑖𝑡ℎ𝑚 𝑒𝑙𝑖𝑚𝑖𝑛𝑎𝑡𝑖𝑛𝑔 𝐷𝐶 𝑜𝑓𝑓𝑠𝑒𝑡
Single Ended Protection
Voltage and current phasors determined by fault type to properly solve for “n”
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AG Faults
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LL Faults
ZR1 = positive sequence impedance of the transmission line
ZR0 = zero sequence impedance of the transmission line
K0 = ratio of zero sequence impedance to positive sequence impedance of the line.
Two Ended Protection
Data needed for calculation of fault location
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Voltages
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Currents
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Time Stamps = Communication to central location for analysis
Method for location based on negative-sequence voltage profile along transmission line
𝑍𝑙𝑖 = +𝑠𝑒𝑞𝑢𝑒𝑛𝑐𝑒 𝑖𝑚𝑝𝑒𝑑𝑎𝑛𝑐𝑒 𝑜𝑓 𝑙𝑖𝑛𝑒 𝑠𝑒𝑐𝑡𝑖𝑜𝑛 "𝑖"
𝑉𝑘_𝐿_𝑋
k = line section
L or R = left or right junction
X or Y = terminal
Two Ended Protection
Negative Sequence Voltage Magnitudes
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Voltage magnitudes indicate faulted line section
Two Ended Protection
Algorithm estimates the distance to the fault on the homogenous line section.
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Use the equivalent negative sequence voltages 𝑉2𝑘_𝐿_𝑋 and 𝑉2𝑘_𝑅_𝑌
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Voltage magnitudes at the fault location calculated form the two junctions should equal
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Algorithm solves “m” = distance to the fault
Comparisons
Single Ended Fault Location
Pros
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Only needs access to 1 terminal’s
voltage and current values
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No communication to other
terminals
Cons
Two Ended Fault Location
Pros
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Algorithm not affected by fault
resistance, load or zero sequence
mutual coupling.
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Accurate fault locations
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Nonhomogeneous systems
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Nonhomogeneous systems
Cons
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Subject to errors from load flow
mutual coupling
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Communication to other terminals
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Needs accurate time stamps
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Data at both ends gathered at one
location for analysis
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Fault location approximation
accuracy
References
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J.M. Kennedy, General Electric, “Evaluation of a Phasor-Based Fault Location Algorithm,”GE
Protection and Controls, GER-3963.
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Yanfeng Gong, Mangapathirao Mynam, Armando Guzmin and Gabriel Benmouyal, Schweitzer
Engineering Laboratories, “Automated Fault Location System for Nonhomogeneous Transmission
Networks,” Boris Schulim, Orange and Rockland Utilities, 2012.
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Abdolhamid Rahideh, Mohsen Gitizadeh, Sirus Mohammadi, “A Fault Location Technique for
Transmission Lines Using Phasor Measurements,” International Journal of Engineering and Advance
Technology (IJEAT), ISSN: 2249-8958, Volume-2,Issue-1, October 2013
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IEEE Guide for Determining Fault Location on AC Transmission and Distribution Lines, IEEE Standard
C37.114, 2004.
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S.M. Brahma, “New Fault Location Method for a Single Multi-Terminal Transmission Line Using
Synchronized Phasor Measurements,” IEEE Trans. Power Delivery, Vol. 21-3, pp. 1148-1153, July
2006.
Thank you
Questions?