1. Determining Crossing Conductor Clearance Using Line-Mounted LiDAR
McCall, J., Spillane, P., Lindsey, K. Lindsey Manufacturing USA
CIGRE US National Committee 2015 Grid of the Future Symposium

2. The Trouble with Line Crossings
Numerous variables affect clearance between crossing or co-located lines:
Conductor characteristics
Ambient temperature and wind assumptions (for conductor movement)
Insulator and structure deflection
Sag of each line, which depend on:
Current (for heating)
Solar radiation
Cooling associated with wind
Insulator swing and tower movement from wind and conductor expansion/contraction,
Weight effects of ice and snow loading
etc

3. ENMAX’ Particular Problem
138kV line co-located above a 25kV circuit for 9.3km
The T and D lines have very different loading profiles
New Shepard Energy Centre adds 800MW local generation
Altered power flows result in very different loading profiles on 138kV circuit
Identified system contingencies could result in greatly increased sag
Concern over verifying clearance

4. Transmission Line Monitor with Integrated LiDAR
Enmax chose the Lindsey TLM conductor monitor designed for dynamic line rating applications
Integrated LiDAR provides direct and continuous measurement of conductor clearance to ground
Accurately detects changes in clearance from:
Conductor sag from heating / cooling
Vegetation growth
The Unique thing that it does, as I mentioned, is that it has an On-Board LiDAR that directly measures Clearance of the Conductor to Ground or to the next closest object.
Also it has sensors to measure Cond. Temp-., Cond. Vibration, Tilt and Roll of the Conductor and Ground temp.

5. Difference in measurements provides inter-line clearance
138kV
Difference in measurements provides inter-line clearance
25kV

6. Added algorithm to blocks step changes of >1m:
Reported line-to-ground clearance reported by either TLM
Calculated difference between monitor sets
Bad Measurement
TRUCKING

7. LiDAR Geometrical Corrections
LiDAR Angular Corrections
Both TILT (conductor slope) and ROLL (conductor roll) are corrected
Result is a direct downward looking measurement
Conductor Swing (Lateral)
Swing will result in either:
Slight under-reporting (report C instead of B),or
Report worse case (A)
Based on application need, no compensation required

8. While 25kV current is almost constant
Clearance varies by 2.3m over the day
BUT…
138kV line current is 2x as high here
as it is here,
While 25kV current is almost constant
Counterintuitive:
Increased current produces increased sag
Should reduce clearance
What’s happening?

9. 138kV Span Clearance Comparison
Why do spans less than ¼ mile away behave so differently?

10. 138kV Span Elevation Comparison
Span B
Span A

11. 138kV Span Elevation Comparison
Span B
Span A
Elevated adjacent spans
Uniform adjacent spans
Sag of the elevated spans lift the middle span.
A 100mm outward pull on the insulators results in 1.5m sag decrease

12. Summary
Ensuring clearance between line crossings or parallel lines is awkward at best
Line mounted LiDAR-based monitors successfully provide direct measurement of crossing clearance
Unexpected phenomena, such as traffic, can be successfully dealt with
Next Steps
Additional deployment of monitor steps along line
Evaluation of moving to pilot dynamic line rating system