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© 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

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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