Concept of separation distance

ROOF-TOP PHOTOVOLTAIC(PV) LIGHTNING PROTECTION

By ABIN K RAJU S7 EEE ROLL NO:585-Oct-161

INTRODUCTIONEnergy crisis Perfect solution : Solar energyPhotovoltaics : Solar energy to electrical energyElectrical equipment requires protectionMain protection against lightening

5-Oct-162

LIGHTNING PHENOMENONDischarge of atmospheric charges from cloud to cloud or cloud to earthCloud is at higher potential(+) when compared to ground(-)Charge flow is always from higher to lower potentialThus cloud gets discharged to the earth or ground

5-Oct-163

LIGHTNING PROTECTION PHENOMENON

Charge flow is always through low resistance pathIn LPS ,we produce a low resistance path by external meansThe resistance of low resistance path should be less than the resistance of air

5-Oct-164

TYPES OF LIGHTNING STROKES

DIRECT STROKES Lightening discharge is directly from the cloud to the subject equipment . It produces high level transients.

INDIRECT STROKES It results from the electro statically induced charges on the conductors due to the presence of charge clouds . It produces low level transients.

5-Oct-165

ISOLATED AND NON-ISOLATED SYSTEMIsolated system : lightning protection system is isolated from the systemNon-isolated system: potentially damaging voltage differentials are limited by bonding the lightning protection system to the structure

Isolated and non-isolated protection5-Oct-166

SEPARATION(ISOLATION) DISTANCE REQUIREMENTSA separation distance between the external LPS and structural metal parts is necessaryThis reduces the induction of partial lightening current internallyThere should have a separation gap(s) between lightning conductor and structural parts

Concept of separation distance5-Oct-167

EARTHING SCREEN To protect the power stations and substations from direct strokesOVERHEAD GROUND WIRES To protect the transmission lines against direct strokes LIGHTENING ARRESTORS To provide protection against travelling waves which produces high voltage surge

METHODS OF LIGHTNING PROTECTION5-Oct-168

LIGHTENING PROTECTION SYSTEMS(LPS)

EXTERNAL LPS

AIR TERMINATION SYSTEMDOWN CONDUCTOR SYSTEMEARTH TERMINATION SYSTEM

INTERNAL LPS

5-Oct-169

EXTERNAL LPS

Used to avoid direct strikes on the structuresThe principle is to catch the lightning strike on a rod(lightning rod)And evacuate the energy to the ground with specific down conductors 5-Oct-1610

1. AIR TERMINATION SYSTEMA conducting device mounted above the highest point of a building It provides protection by discharging atmospheric electric charges to down conductorThey are of 3 types: 1.Air Rods(finials) 2.Catenary(suspended) 3.Meshed conductor

Air rod on the top of building5-Oct-1611

Continues..The tracing of optimum location of air termination system is determined by 3 methods 1.The rolling sphere method(RSM) 2.The protection angle method(PAM) 3.The mesh method(MM)

5-Oct-1612

ROLLING SPHERE METHODThis is a simple method to find area needs to be protectedUsed to determine side strikesIn this a sphere is rolled over the surface of structureThe point where sphere touches is vulnerable to lightning and needs air terminationThis determines which class of protection is needed

Rolling sphere method5-Oct-1613

CLASS OF PROTECTION

5-Oct-1614

THE PROTECTIVE ANGLE METHODThis method is a mathematical simplification of the rolling sphere methodThe protection angle is measured by the radius of the rolling sphereThe protection angle varies with the height of the air termination & thus the class of LPSThis method is limited to the height equal or less than the rolling sphere radius

PAM for a single air rod5-Oct-1615

Continues

Effect of height of the reference plane on the protection anglePAM applied to an inclined surface5-Oct-1616

THE MESH METHODThis method is for the protection of plane or flat surfacesThis method is used only if the meshed conductors are;Positioned on the edges of the surfaceThe mesh size is in accordance with the standard tableNo metallic structures should protrude outside the volumeFrom each points at least 2 separate path should exists to ground

Protection via mesh method5-Oct-1617

17

Continues..

Standard mesh size for mesh method

Mesh method for compound structures5-Oct-1618

COMBINED PROTECTION OF RSM,PAM&MM METHOD

5-Oct-1619

2. DOWN CONDUCTOR SYSTEMElectrically conductive connection between the air termination system&earth terminationTo conduct the intercepted lightning current in the earth termination systemImplemented by separate conducting rodsDown conductor system

5-Oct-1620

3. EARTH TERMINATION SYSTEMTo disperse the surge current in down conductorsMain characteristics are:Low electrical resistance between electrode and earthGood corrosion resistance

Earth termination system5-Oct-1621

INTERNAL LPSThe event of direct strike is protected by external lightning protection systemApart from direct strike ,indirect or near by strikes which generates electromagnetic pulse which produces inductive couplingInternal LPS is used for the protection against indirect strikesInternal LPS works on the principle of lightning protection zones(LPZ) 5-Oct-1622

LIGHTNING PROTECTION ZONEIn this the structure to be protected is divided into different zones In this the lowest zone has the highest effect of lightning electromagnetic pulses

Lightning protection zones5-Oct-1623

ARRANGEMENT OF LPZ

Lightning protection zone concept5-Oct-1624

ROOF TOP PV SYSTEMSBuilding Integrated Photo Voltaic(BIPV) as an implementation of solar energy had high demand at presentDue to the mounting height and extended surface it has a great vulnerability to lightning interceptionTherefore the mounting design of BIPV should given great care 5-Oct-1625

DESIGN OF LIGHTNING PROTECTION SYSTEMSIn this PV panel is an isolated system from LPSThat is a minimum separation is kept between LPS and PV panelThe mounting of the PV panel should be in side the range of protection angle

Protection of PV panels applying protection angle method

5-Oct-1626

SPD CONNECTION OF ROOF TOP PV SYSTEMSIn this the connection of surge protective device to the roof top PV system is shownFrom PV panel the dc output is fed to the inverterThen it is fed to the main distribution board and the to the power lineAll metallic portions are equipotentially connected to the bonding bar

5-Oct-1627

CONCLUSIONBIPV system is becoming emerging trend in indiaThe PV panels are usually placed on the roofs of tall buildings so the chance of lightning strikes are largeTo protect the panels available protection techniques for safe guarding the buildings against direct strikes are to be evaluated to provide a safe location to install the PV system5-Oct-1628

REFERENCEhttp://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6564584&isnumber=6564504https://en.m.wikipedia.org/wiki/lightning_rod#/search https://en.m.wikipedia.org/wiki/photovoltaic_system http://schirtec.at/technical-information/lightning-protection-theory/https://www.google.co.in/search?q=protection+by+lightening+rod+method&oq=protection+by+lightening+rod+method&aqs=mobile-gws-lite

5-Oct-1629