1. Lightning Protection Chapter 6 PowerPoint slides by
Stf/C Harl Porter, SN
Marine Electronics
Rear Commander for Electro-Mechanical Systems is
R/C Gene Danko, SN

2. Overview Characteristics of Lightning Principles of Protection
Precautions for Personnel
Precautions for Electronic Equipment
Major sections in this chapter

3. Characteristics of Lightning
Static Electricity
Ultra-High Voltage Generation
The Discharge
Surface Dispersion
Basic Laws of Electricity
Topics in this section

4. Lightning Static Electricity Ultra-High Voltage Generation
Separation and storage of electrical charge
A spark is an extremely small lightning discharge
Ultra-High Voltage Generation
Surface of earth is normally negatively charged
Top of storm clouds are positively charged
Forces nearby earth to become positively charged
Develops a multimillion-volt potential
(No notes)

5. The Discharge Clouds send negative charged leaders down
Earth sends positive leaders up
From grounded sharp metal objects
Conducting path when leaders meet
Unidirectional (DC) current flow
Voltage potential 100 to 1,000 million volts
Current range 10,000 to 200,000 amperes
Duration from 1 microsecond to 1 second
(No notes)

6. Anatomy of a Lightning Stroke
Electrons begin zigzagging downward in a forked pattern. This is the “stepped leader.”
As the stepped leader nears the ground, it draws a streamer of positive charge upward.
As the leader and streamer come together, a powerful electrical current begins flowing.
Current begins the return stroke, an intense wave of positive charge traveling upward about 60,000 miles per second.
Copied from page 132 of The Weather Book by USA Today.
USPS has their permission to use their Art Work in our classes.

7. Surface Dispersion Surface dispersion Surface dispersion is deadly
Main portion of lightning bolt penetrates earth
Spurs find far-reaching paths along surface
Surface dispersion is deadly
Stay out of the water
Keep away from trees
Know that are no trees in water
Are not a safe place during a lightning storm
If lightning hits tree, it may explode
Also get surface dispersion around tree
as tree is not always a good ground

8. Basic Laws or Electricity
Lightning creates magnetically induced current in all metal items within its influence
The longer the wire, greater the current
The closer the strike, greater the current
Any impedance to current flow results in
Build up of high voltage at that location
Resulting in arc-over to reach ground
Ignites flammable material
Vaporizes metal of insufficient cross-section
(No notes)

9. Principles of Protection
Cone of Protection
Lightning Protection System
Power Boat Applications
Sail Boat Applications
Topics in this section

10. Cone of Protection Lightning rod protects areas within its cone
60 degree cone is 99% effective
45 degree cone is 99.9% effective
Fig 6-1
Less current flow from sharp pointed tip
More current flow from blunt or ball tip

11. Lightning Protection System
Air Terminal
Discharge Conductor
Water Terminal
Bonding
Topics in this section

12. Air Terminal Also known as a Lightning Rod
Traditionally ¼ inch copper rod
With sharpened point
Six inches above object to be protected
Blunt object will have more intense discharge

13. Discharge Conductor Not less than #4 AWG
Uninsulated stranded copper wire
“Straight” from Air Terminal to Water Terminal
No sharp bends (bend radius of 1 foot)
Should be run outside of hull
Electrical wiring should be at right angles
Split bolt for joining cables together
#8 AWG solid copper wire at top
#4 AWG solid copper wire in middle
#4 AWG stranded tinned copper wire at bottom
Lower left is Split-bolt connector
With South Carolina Quarter #4

14. Water Terminal Also known as a Ground Plate External to hull
Sailboats use metal keel
Area of one square foot
Not painted
No water film between plate and hull
Use bedding compound
Note size of commercial water terminal
Need one square foot in sea water
and four square feet in fresh water
If have water between plate and hull, may turn to steam during a lightning strike and “blast” a hole in hull
Size: 18” x 6” x ½”

15. Bonding (Chapter 2) Bonding is also for Lightning Protection
Purpose – keep all metal surfaces at zero potential
To prevent electrical shock
To prevent stray current corrosion
To prevent induced potential from lightning strike
Bonding conductor
Cross section of #6 AWG
Strap not less than #20 gauge (0.032 inch thick)
Normally #6 bare copper wire
(No notes)

16. Powerboat Application
Fiberglass antennas provide NO protection
Add lightning rod on other side for protection
e.g. grounded metal whip antenna
Ground the signal mast or “Tuna Tower”
Need a ground plate
Stay within the cone of protection
(No notes)

17. Powerboat Application
Grounded metal whip provides protection
Grounded HF whip antenna with loading coil
No protection above loading coil
Unless loading coil bypassed with large conductor
Fig 6-2

18. Sailboat Application Metal masts are grounded (bonded)
Add discharge conductor to wood mast
Shrouds and stays grounded
Keel is ground plate
Fig 6-3

19. Precautions for Personnel
Remain inside the boat
Trust lightning protection system
Stay Out of the Water
Surface dispersion
Avoid contact with metal surfaces
Induced voltage
Handle only one metal control at a time
(No notes)

20. Precautions for Electronics
Before a lightning storm
After a lightning strike
Topics in this section

21. Before Lightning Storm
Put a loop in cables
Signal
Power
Disconnect ALL unnecessary equipment
before, NOT DURING a lightning storm
All entertainment equipment
Redundant communications and navigation equipment
Disconnect power cables, if accessible
Disconnect and ground antennas
(No notes)

22. Before Lightning Storm 2
If underway, keep operational
One VHF radio
One GPS / chart plotter
Radar, if so equipped
Handhelds stored below
Want handhelds off and stored well inside cone of protection
Fixed equipment may be damaged by a lightning strike

23. After Direct Lightning Strike
First, check crew – CPR Required?
Next, check hull – repair any new leaks
Then check navigation & safety equipment
Radios with test call, or with handheld
Magnetic compass
Verify with GPS
Deviation table may no longer be accurate
If fixed VHF Radio or GPS inoperative
Go to backup handheld unit
People first
Boat second
Then electronics

24. Summary Tremendous energy in lightning strike Lightning protection
Based on cone of protection
Components
Air terminal
Discharge conductor (#4 AWG stranded)
Water terminal (1 sq ft)
Bond all metal above deck
Before lightning storm
Disconnect all unnecessary equipment
After lightning strike
First check people
Then hull
May have to go to backup electronics
(No notes)