surgesafe lightning protection system -presentation

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PRESENTATION ON LIGHTNING PROTECTION SYSTEM

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An Essential Risk Management Element

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Statistical Data on Insurance Claims

Burglary29%

Flood5%

Fire6%Lightning

21%

Storm1%

Others14%

Misoperation24%

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US National Space & Science Technology Centre

Two instruments were used to gather data for the aerial map. The Optical Transient detector was launched aboard NASA's Microlab satellite in 1995 and the Lightning Imaging Sensor is fitted to a joint NASA-Japan satellite launched in 1997 to measure tropical rainfall levels. The sensors gathered lightning data over

periods of five and three years respectively.

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Lightning Strikes

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Typical formation of Lightning - Step 1

Negative electrical charges build up within clouds

Electric field intensification

Positive charges gather on ground

Air breakdown leads to stepped leader

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Typical formation of Lightning - Step 2

Continuation of downward step leader

Further electric field intensification

Strong upward positive streamer generation

Streamer racing towards downward step leader

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Typical formation of Lightning – Step 3

Positive upward streamer meets the downward step leader

Conducting path forms

Potential is equalised by the "return stroke“

Visible lightning flash

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Lightning Strikes

Streamers

Step Leaders

Main Discharge

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Typical characteristics of Lightning Pulse

LONG TAIL=> flow

HIGH ENERGY

HIGH VOLTAGEdi & dvdt dt

VERY FASTRISE TIME

Typical50 kA

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Typical Lightning StrikeInstantaneous Power : Over one Megawatt

Total Energy : Over 250 Kilojoules

Sound Pressure : 90 Atmospheres at 500m away

Temperature : 30,000°K+ (5 times Sun Surface)

Rise Time : 0.1 to 5 Microseconds

Average Current : 35 kA

Duration : 300 Microseconds + Repeats

Channel Length : 5 km

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How Transients enter your Equipment

Capacitive coupling is where the transient voltage is coupled due to the inherent capacitance between two circuits

Magnetic coupling occurs when magnetic field of a current carrying conductor induces lightning current on to an adjacent conductor

Galvanic coupling is a direct electrical connection

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Direct Lightning Damage

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Transient Damage

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4 Step ApproachIncludes:Definition and provision of area protection direct strike

Creation of a bonded earthing system

Protection of power lines

Protection of signal, data and communication lines

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Risk AssessmentMany standards have essential risk assessment methods

AS1768

IEC61024

NF C 17-102

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Definition and Provision of Area

Protection

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Electrical Field Modelling

Originally developed by AJ Ericksson

CAD software forms three dimensional representation of the structure to be protected and the air terminals to be used.

Based on this representation the software determines if protection is achieved to the required level of risk.

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Electric Field Modelling

Striking distance is influenced by geometry and dimensions such as height, width, radius and altitude all have effect.Corners and edges cause an up-leader to be launched when the down-leader is at a greater distance than flat surfaces. This striking distance is calculated for all directions from the terminal and from the structure resulting in two surfaces.

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Electrical Field Modelling

The software determines if coverage is successfully achieved based on the relative distances between the surfaces and typical leader velocities based on the site & location conditions

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Allywell Air Terminals

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Allywell Air Terminals

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Creation of a Bonded Earthing

System

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Why Grounding?By CODE Required

Personnel Safety ( Touch and step potential)

Equipment Protection (Operate over current device during a ground

fault 50/60Hz event)

Lightning Dissipation (5kHz - 50kHz)

Electro-Static Discharge (ESD)

Noise Control (Computer Grounding)

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Objective of Lightning Protection Earth

To dissipate the lightning energy with minimum voltage rise that may affect

people or equipment

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Earth Potential Rise

Consider only REarth potential rise: Ve = 1 x R

= 50000 x 10= 500 kV

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Lightning Frequency: 5 – 50KHz

SHUNT CONDUCTANCE Gis related to soil conductivity pand contact resistance

CHARACTERISTIC IMPEDANCE

Z0 = R+jwLG+jwC

We want: Z low = R low, L low, C high

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Types of Lightning Earth

Regular earthing Bi-polar earthing Radial earthing

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Earthing System

Combination ofhorizontal strip andvertical rods - Linea - Radial

Optimum spacingL > 2 x D

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Electrogrip with Earth Rods

ELECTROGRIP

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Thank You!

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