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

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

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

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.

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

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

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

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?

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

138kV Span Elevation Comparison Span B Span A

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

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