CPR Lightning Damage Investigation and Mitigation Strategies

1. CPR Lightning Damage Investigation and Mitigation Strategies Peter Brackett Canadian Pacific Railway Peter_Brackett@cpr.ca

2. AAR Surge Testing at LTI Lab

3. AAR Surge Testing at LTI Lab

4. WOODEN BOARD 4000V++

5. AAR GND STRIP, #6 WIRE & 1.5” ALUM STRAP 3400V

6. 1.5” ALUMINUM STRAP1900VUSE TO RETROFIT EXISTING

7. METAL PANELS - LIRP2250VLOW ENERGY - REMOVE PAINTED EDGES

8. WOOD71”>5000v WOOD53”4000v WOODAAR&STRAP3400v WOOD1.5” STRAP19000v

9. METAL PANELS - LIRP2250V WOODEN TERMINAL BD1.5” ALUMINUM STRAP1900v

10. Lightning is Generated by Circulating Wind and Water in Thunderstorm Cloud

11. Lightning

12. Mystery of Lightning • Lightning is mysterious because it occurs in a time frame that is so different from our normal experiences. • We are familiar with 60Hz AC distribution and DC battery systems. This is our normal frame of reference. AC is like driving a car down a highway and DC is like walking along the same highway but lightning is like a supersonic jet flying at car level shooting off super-supersonic rockets. • So Lightning doesn’t seem to react the same way, it doesn’t need a conductor to move, it makes its own paths usually invisible paths through the air.

13. Mystery of Lightning • Lightning’s time horizons are microseconds, millionths of a second. • Lightning can be understood if we think in the timeframe of the lightning event and analyze the paths based on high-speed charge movement not the time frame of familiar electrical activity.

14. Surge Damage Investigation: 150’ Rolling Sphere of Lightning Protection Zone 150’ Tower Radio/Fiber Bungalow Maple Creek Saskatchewan Communication Tower Site View from the East

15. CPR 10 by12 Communication Site Antenna Coax & Lighting Cables 2by6 wood/drywall construction with metal skin Ground Wire

16. Site Physical Geometry: Remote Connections East North

17. Telephone Electrical Connections Fiber with Shield Ground Coax Grounds Fibre Racks Radio Racks Skid Frame AC Power AC SPD

18. Locations Telephone Damage Fiber with Shield Ground Coax Grounds Fibre Racks Coax Arrestors- No Damage Radio Racks Skid Frame AC Power AC SPD

19. Damage Summary: 1) All three telephone line connections (at both end of wires) 2) Radio Equipment In-Line AC protector and internal power supplies 3) Fibre AC connections to Power Supply 4) No Damage on Coax Antenna connections 5) No Damage to upstream AC power 6) No significant damage to Telephone equipment in Dispatcher Office where 25 pair cable originated from 7) No Damage to the Fibre Equipment- still functioned from Battery

20. How Did the Damage Occur? What was the Damage Mechanism? Challenge: What current flow path can explain: - the observed damage - the undamaged equipment - the undamaged remote connections.

21. Lightning Leader Fibre Charger Strike No Coax Damage Fibre2nd Row Charger Radio Telephone Interface In Line 120V SPD RTI Radio2 Radio1 Internal wiring Inductance Voltage moves faster than external Grid Inductance Voltage driving Current through AC Chargers Equipment Ground Plate Strike Raises Potential of Ground Plate Forcing Current into Site Charger Telco Remote Cable Current Flow Through Equipment Vaporizes Conductors

22. Multiple Equipment Damage Caused by:Ground Plate Potential Rise driving current into siteCurrent Flow through equipment out to remote telco connections vaporizing small wiresPotential Difference between Ground Plate and far side Power Ground driving current through Power Supplies vaporizing conductors

23. Surge Mitigation Strategies: 1. Reference all external connections to a Low Impedance Reference Plane (LIRP) with Surge Protection Devices (SPD’s). 2. Incorporate this Low Impedance Reference Plane (LIRP) into a conductive enclosure following the Faraday Cage shielding principles. (Charge applied to a conductive enclosure is forced to the outside of the enclosure).

24. LIRPLow Impedance Reference Plane (LIRP) with Surge Protection Devices (SPD’s).

25. FARADAY CAGE PRINCIPAL

26. CPR’s Implementation of Faraday Cage and Low Impedance Reference Plane (LIRP) Wiring

27. 4. Reduce Z*di/dt voltage rise across equipment by avoiding surge current paths through equipment. Designating one location ie top or bottom as the common path for external connections and routing all external connections via this path best accomplishes this. Avoid hidden paths such as connection of rack mounting bolts into frame of building beneath floor. 5. Use current division to control the dissipation of lightning strike energy on an antenna tower grounding system through multiple paths 6. Treat Surge Energy Conduction as high frequency current (~100Khz). The more surface area the surge path has the less Voltage Rise. For the same amount of metal a flat bar or hollow tube has less IZ (Impedance) voltage rise.

28. 7. Maximize bend radius in surge current wire paths.Surge currents are a high force event like water surging into a fire hose.Bends greater than 12” do not increase IZ voltage rise. 8. Minimize coupling between surge current carrying wires and signal wires. Insulated wires run close to each other couple 70% of surge energy between wiresInsulated wires run with a 3” separation couple less than 40%, 6” less than 25%Wire run against a conductive plane to radiate energy into plane and less into free space.Wires separated by a conductive plane have minimal coupling. Wires crossing at right angles have minimal coupling

29. CPR Lightning Damage Investigation and Mitigation Strategies Peter Brackett Canadian Pacific Railway Peter_Brackett@cpr.ca 403-319-7781