© 2015 Electric Power Research Institute, Inc. All rights reserved.
Paul Myrda
Technical Executive
Project Information Webcast
March 2015
Automated Transmission Line
Impedance Calculation
Project
2© 2015 Electric Power Research Institute, Inc. All rights reserved.
Background
Can we use LIDAR / GIS
data to improve or automate
the transmission line
impedance calculation
process?
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First Step
Data Needed– Span lengths– Tower geometry– Conductor positions– Conductor properties– Conductor Attachments– …. more
Data Available in LIDAR– Yes– Yes– Yes– No– Yes– Yes
Data is in LIDAR but more useful data is actually in GIS
But we can get it elsewhere
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Provided Data – in XML
Conductor Attributes– Type and span length. No bundle information.
Transmission Line Discontinuities– Build type and span length
Unique ID numbers are given for all the data provided
Operating Voltages
Tower Characteristics– Height– Base elevation
Sample XML Data
structure_list_report rownum="11"><rowtext/><struct_number>99933399</struct_number><station units="ft">693.81</station><line_angle units="deg">5.89</line_angle><ahead_span units="ft">977.12</ahead_span><height_adjust units="ft">0.00</height_adjust><offset_adjust units="ft">0.00</offset_adjust><orient_angle units="deg">180.00</orient_angle></structure_list_report>
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Potential Data Gaps
Conductor Clearance– Tower height is provided but not the height (ground clearance) of the
actual conductor, we need tower drawings to determine points of attachment. Designed / survey route center line clearance data may be needed.
Transmission Line Discontinuities– Need to know where line segments are joined, originate, and
terminate– Transpositions
Conductor Geometry, Arrangement, and Attachment– Physical conductor specs are provided, however we still need
information relating to conductor attachment points, arrangement and geometry, specifically how the phases are arranged geometrically, and if they consist of one or multiple wires (if multiple need bundle bracket dimensions).
Data is actually in GIS
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Sample Tower Configuration
struct_number set_no phase_no set_label wire_attach_point_x units4 wire_attach_point_z units699933399 1 1 SW1 2081692.96 ft 942.65 ft99933399 2 1 SW2 2081750.83 ft 942.56 ft99933399 3 1 TW1 2081687.62 ft 891.97 ft99933399 4 1 TW2 2081701.05 ft 874.85 ft
Outlier
© 2015 Electric Power Research Institute, Inc. All rights reserved.
Support Provided by
Sean McGuinness
GOP
Calculating Sequence Impedances of
Overhead Lines
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Typical Single Circuit Tower Geometry
LIDAR measurements: – Phase and shield wire conductor relative position– Conductor position both at tower and along span
X1, B1 important for load flowX1, X0 important for short circuit
GIS
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Positive Sequence Impedance
ln
Message:– Phase conductor spacing increases X1
– Phase conductor spacing decreases C1
– Phase conductor spacing unlikely to vary in service
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Zero Sequence Impedance
j 3 ln· ·
··
Message:– Phase conductor spacing decreases X0
– Phase conductor spacing unlikely to vary in service
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Summary
GIS measurements provide conductor positions along entire routeCan help improve calculation of X1, X0, B1, B0
– X1, B1 important for load flow– X1, X0 important for short circuit
Most helpful measurements: – Phase conductor spacing– Distance between phase conductor and shield wire
The longer the line, the bigger the impact of impedance
errors on the overall network simulation result
12© 2015 Electric Power Research Institute, Inc. All rights reserved.
Conclusion
Can we use GIS data to
improve or automate the
transmission line impedance
calculation process?
13© 2015 Electric Power Research Institute, Inc. All rights reserved.
Automated Transmission Line Impedance Calculation
Benefits Improve network model impedance
process and accuracy Reduce manpower required to calculate
and maintain network models Simplify overall impedance model
creation through data reuse
Phase I – Complex Line Impedance Calculation Process based on a complex transmission line which has multiple mutually coupled lines and other complexities. Phase II – Improved Line Impedance Calculation Process includes terrain
variations, conductor sag and other parameters that may affect the actual line impedance and the accuracy of the actual impedance value.
Price of ProjectThe cost of the project is $100K and it qualifies for tailored collaboration or self-directed funding. A minimum of 5 participants are needed. Target participation is 8.
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Together…Shaping the Future of Electricity
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