Lightning presentation QCWA FM.pightning Protection PPT is useful for Electrical Engineers. code and Practice of Lightning pt

Lightning Protection PPT is useful for Electrical Engineers.
code and Practice of Lightning

1. A presentation to the QCWA
Chapter 70 about Lightning and
Grounding

2. Many of the following slides courtesy
of
Todd Sirola C.O.O.
SAE Inc.
Todd provided a presentation to the CCBE last fall
on the following topics
Threats To Equipment
Grounding Fundamentals
Electrical Protection Systems
Case Studies

3. How do we get lightning?
•We need convection, cumulo-nimbus clouds,
the ones with the anvil shape, the result of a
collision of warm and cold air masses
•Ice pellets and grauple
•Super cooled water droplets above the
freezing level
•Earth has a positive charge, the bottom of the
cloud negative charge
•Air is a great insulator so the charges build up

4. Capacitor Analogy

5. And then, BOOM!

6. •At some point the charge is large enough to
overcome the insulator
•The leaders build out slowly at relatively low
current in both directions
•Once they join the current flows. Upwards of
400,000 amps peak
•Power levels in excess of 1 Gigawatt may be
encountered
•Systems need to be engineered with this in
mind

7. •lightning can, and often does, strike the same
spot more than once--even the same person.
U.S. park ranger Roy Sullivan reportedly was
struck seven times between 1942 and 1977.
•Take especially swift action if your hair stands
on end, as that means charged particles are
starting to use your body as a pathway.

9. Just remember
Lightning energy and power system ground
faults will find a path to earth.

The key is to design an electrical protection
system to ensure it doesn’t damage
equipment.

10. 09/03/93 - 29.6 kA
strike - Sandia
National Labs

14. Evidence in Nature

15. Electrical representation of a tree
Roots
Branches
Trunk

17. Types of Lightning
•Cloud to Cloud (CC)
•Cloud to Air (CA)
•In Cloud
•Cloud to Ground (CG)
•Peak or Positive Giant
•Blue Streak
•Red Sprite

19. A plug for Todd, he can provide
Design, Supply and Install
Professional Engineering Support
Grounding System Audits
System Resistance (R-Value) Testing
Soil Resistivity Testing
Forensic Analysis
Educational and Training Seminars

20. What are the threats
Lightning
•Direct
•Induced
•AC mains
•Telecom twisted pair
Electric power systems
•Switching operations
•Power system ground faults

27. A typical Ham installation

28. Definition of Grounding
An engineered , low impedance path to
earth.
Definition of Soil Resistivity
A measurement of the electrical resistance of
a unit volume of soil. The commonly used unit
of measure is the ohm-m.

29. Factors Influencing Soil Resistivity
Soil Type (chemical makeup)
•natural elements (clays, quartz)
•foreign elements (salts, fertilizer)
Moisture Content
Temperature

30. Soil Type
Soil Type Resistivity (ohm-m)
Clays 10-150
Sandy Clays 150-600
Pure Sand 600-5000
Gravel 5000-30,000
Shale/Slate 400-1,000
Limestone 1,000-5,000
Sandstone 5,000-50,000
Granite 1,000-80,000

31. Moisture Content

32. Temperature
Temperature Resistivity (ohm-m)
20
0
C 72
10
0
C 99
0
0
C 130
0
0
C (ice) 300
-5
0
C 790
-15
0
C 3,300

33. Ground Resistance Formula
R =  X f
R= ground resistance
 = soil resistivity
f = a function determined by
the
shape and size of the
electrode

34. Electrical Protection Systems
Outside Ground Electrodes
•Low R value, Low Impedance, High
capacitance,
• High energy dissipation
Inside/Equipment Grounding
•Single point
Surge Protection Devices (SPD’s)
•AC system, Incoming telecom, Transmission
lines
Structural Lightning Protection
•Lightning rods, Down conductors
Proactive Lightning Detection

35. What makes a good outside
grounding system?
Low Impedance
•Low Resistance
•Low Inductance
•High Capacitance
High Energy Dissipation
Proper Orientation
Corrosion Resistance
Theft Resistant

36. Low Impedance Grounds
Z = V / I
or
Z = [ R
2
+ (2ƒL - 2ƒC
-1
)
2
]
1/2
Lower Resistance
Lower Inductance
Increase Capacitance

37. Low Impedance Grounds
•Increase electrode surface area
•Use a capacitive enhancement
product
•Increase conductor size
•Minimize bends
•Maximize bending radius
•Eliminate 90º bends
•Decrease # of connections

38. The Trouble with “T”
Connections
Lightning travels in straight lines.
90 degree connections offer much higher
impedance than a straight horizontal conductor.

39. Weaknesses of
Conventional Grounding Systems
•Poor lightning protection
•Higher surge impedance
•Seasonal fluctuation of R value
•Subject to corrosion
•Multiple connections

40. How can I lower Ground Resistance?
Add more rods?

41. How can I lower Ground Resistance?
Rods must be spaced appropriately or
their benefit is diminished.
#Rods *Multiply By
2 1.16
4 1.36
8 1.68
16 1.92
24 2.16
*Multiplier if rods are spaced one length apart.

42. How can I lower Ground Resistance?
Conductive Concrete

43. Horizontal Electrode Construction

51. Vertical Electrode Construction

52. What about inside the shack
Or how to keep Greg on the air

53. Single Point Grounding
Buildings should be converted to single point grounding.
This method eliminates current loops and creates an
environment in which it is easier to protect equipment
against power surges from whatever source.

54. Single Point Grounding
Typical Radio Site Layout

55. Single Point Grounding
Typical Radio Site Layout

56. Single Point Grounding

57. Single Point Grounding

58. Single Point Grounding
Materials used for inside grounding
•Green insulated grounding conductor
•Rated double holed compression lugs with
stainless steel hardware
•Copper ground bars with insulated
mounting brackets
•NON-Metallic mounting clips
•Parallel Compression Connectors
Label all conductors at both ends with
permanent identification labels

59. Surge Protection
Surge Protection is required for all metallic
conductors that enter the building:
•Telephone lines
•Intranet Line
•AC Power Systems
•Transmission lines

60. Surge Protection

61. Types of Surge Protection
Voltage Limiting Devices
•Gap devices e.g. air gap carbon arrestors and gas tubes
•silicon avalanche diodes, metal oxide varistors.
Current Limiting Devices
•Fuse links
•Circuit breakers
•Heat coils
Other
•Quarter Wave Stubs
•Neutralizing transformers
•Isolation transformers
•Dielectric fiber optics

62. Case Studies
CKVR Television, Barrie Ontario
Tower located at the studio
Complex on top of the hill overlooking Barrie

63. Case Study:
CKVR - Barrie Broadcast Tower

The protection system included a comprehensive approach to eliminating
damage due to lightning and electrical surges.
•Outside grounding electrodes
•Inside single point grounding
•LSC2000 Lightning Strike Counter
•ESID storm monitor linked directly
to a stand-by Generator

64. CKVR - Barrie Broadcast Tower
Outside Grounding
A total of 378 m of horizontal
electrode was installed at the
tower center and each of the guy
anchors. The overall ground
resistance of the system is 0.9
ohms.

65. CKVR - Barrie Broadcast Tower
Outside Grounding
Guy Anchor GroundingCompound Grounding

66. CKVR - Barrie Broadcast Tower
Inside Grounding
SAE Inc. installed a
Master Ground Bar
(MGB) in the equipment
building.
MGB

67. CKVR - Barrie Broadcast Tower
Lightning Strike Counter


Sensor Unit
Counter Unit

68. CKVR - Barrie Broadcast Tower
ESID - Generator Installation
The ESID detects storms in the area and automatically
switches the site to generator power.


ESID
Generator

69. Is there any science to this?
•It’s a lot of money to spend on the off hand
chance it might take a lightning hit.

70. Case Study:
CKVR - Barrie Broadcast Tower

On June 11, 2000 a severe storm rolled through
Barrie. Lightning knocked out a substation at 6:21
am cutting off power to the surrounding area.
Fortunately at 5:08 am the ESID had identified the
storm activity and switched the site to generator
power. The site remained on generator until 9:40
am when the storm had passed.
CKVR was never off the air.

71. Case Study:
CKVR - Barrie Broadcast Tower

During the same storm the LSC2000 registered 3
direct strikes to the tower. Global Atmospherics
data confirmed the times and provided peak
currents:
4:55 am 20 kA
5:10 am 35 kA
5:59 am 59 kA
The grounding system absorbed the energy of the
strikes and no damage occurred to any of the
sensitive broadcasting equipment.