Structure For Safety And Man Power Engineering Essay

Structure For Safety And Man Power Engineering Essay

Anchoring is required for the undermentioned intents and should be done for all active and inactive equipment and constructions for the safety of work force and equipment.

For edifice and constructions to supply protection against Lightning work stoppages. Lightning work stoppages on unprotected constructions may do terrible structural harm to the edifice / tower and damage the equipment installed inside the edifice.

To supply safety to equipment and personal due to any Earth mistake.

To supply a common mention land for all equipment installed in a web / system.

The foundation is ever provided via one or more Earth cavities which have an Earth music director / rod buried or drilled into the land.

The foundation system for AC and DC equipment should run into the undermentioned demands.

Forces Safety – All metallic parts in the system shall be grounded so that the electromotive force potency can non floor forces.

Equipment and distribution circuit protection – A proper low electric resistance land allows the fuses and circuit surfs to disrupt and unplug the mistake currents and prevent electrical fires and bound equipment harm.

Electrostatic Discharge ( ESD ) – Proper land connexion allows any ESD stored in the system to dispatch.

Reliability – the foundation system should be deterioration free and necessitate minimal care.

Noise decrease – The foundation system should minimise electrical intervention by keeping a low electric resistance way between land points throughout the telecom system. The foundation should forestall and minimise the consequence of noise currents and RF energy.

Definition

Impedance – Electric resistance ( Z ) is the combination of electrical electric resistance ( R ) to the flow of AC / DC current and the capacitive or inductive reactance ( X ) for Alternate current.

Land Impedance / Earth electric resistance – The value of electric resistance measured between a trial point on the dirt and the Earth cavity / Ground Electrode music director.

Land possible rise ( GPR ) – the electromotive force difference between anchoring music directors caused by conductivity of earth return currents, largely caused by mistake currents or due to lightning work stoppage.

Ground – A point in the electrical system designated as zero possible and connected to the infinite Earth / land via electrodes and music directors. Earth is considered as the chief “ Land ” point and all land points are connected to the chief “ land ” point the Earth.

Grounded – Grounded refers to a connexion to Earth.

Earth Pit ( Anchoring Electrode music director ) – An electrode buried in land to accomplish zero possible mention for the equipment land.

Earth system – A system of Earth cavities connected utilizing earth music directors in a ring to hold improved earth electric resistance.

Anchoring / Earth Conductor – Solid metal ( normally Cu ) music director either insulated or bare used to link the equipment land to earth cavities and besides used for connexion of lightning arrestors to the lightning Earth cavity.

Lightning Arrestor / Funnel – a solid Cu rod which is installed on top of a edifice or tower to supply a way to dispatch extra possible generated due to lightning work stoppage to the land via the lightning Earth music director and lightning Earth cavity.

Solid Ground – A point in the Earth system normally connected straight to earth pit via an insulated stranded Cu overseas telegram. The solid land usually refers to a Copper Bus saloon which is straight connected to the Earth cavity. This Cu coach saloon is farther connected to assorted equipment evidences such as Electrical panel organic structure, surge arrestors land point etc.

Down music director – the music director which connects the lightning funnel straight to the land Earth cavity.

Terra Firma – Terminology for the absolute land. Normally an Earth cavity with solid music director is considered as Terra Firma. A group of Earth cavities connected together are besides considered to be at same potency and considered as “ Terra Firma ” .

Main Earth terminal – A solid Cu coach saloon installed inside the equipment /plant room, to which other equipment land are connected. This coach saloon is farther connected via a Cu overseas telegram to terra firma or the music director in the Earth cavity.

Independent Earth / Clean Earth – A Earth Bus saloon which connects via a separate music director from e.g. a Main Earth Terminal ( MET ) and is straight connected to the equipment to be earthed. The clean Earth coach is ever separated from other earthing systems and coach bars in order to avoid noise “ transverse taint ” from one system to another.

Independent Earths are ever used for sensitive devices so as to halt signal taint and noise being fed from the other systems to them. The independent Earth is besides used to individually anchor any noisy devices to halt the dirty signals being fed to other devices via their Earths.

Standard REQUIREMENTS

Multiple Earth cavities or Ground electrodes.

Any telecom edifice / system / GSM site should hold multiple Earth cavities to guarantee full protection to the telecom / power / construction etc.

For most systems a multiple Earth connexion is done to guarantee that the equipment is ever good protected and connected to earth. Similarly two or more earth cavities are interconnected in analogue to accomplish multiple earth waies and besides to hold better Earth electric resistance.

Sites with High land electric resistance

For sites or evidences where the Earth values are high, two or more earth cavities should be prepared and interconnected to hold lower Earth electric resistance. The distance between two Earth cavities should be at least tantamount to the deepness of the larger / deeper Earth rod.

Location of Earth cavities

The ideal anchoring system should supply least electric resistance ( approaching zero or less than one ) and the undermentioned factors can impact the electric resistance to earth for a grounding electrode or Earth cavity.

Damp dirt provides least electric resistance. Overtime, current flow may vaporize wet around rods and Earth cavities. The rods should hence be located in countries where they can be sporadically watered by natural rain or by unreal lacrimation system.

Earth cavities should non be located really near to constructing foundations or at locations where the zone of influence is affected.

The arrangement of land rods should be at least one half of the length from any other construction which affects their zone of influence.

Measurement of Earth opposition

After put ining an Earth cavity / foundation music director and before linking it to the other Earth cavities, the land electric resistance of the Earth cavity should be tested utilizing an Earth Megger utilizing the 3 point method as per IEEE criterion 81. The acceptable electric resistance of the Earth oppose shall be less than 5 ohm.

Multiple Earth or pealing / aura land agreement should be used in order to accomplish better Earth electric resistance.

Electric resistance of multiple cavities connected together.

The Earth value is measured in footings of ohms. The Earth electric resistance value of less than 1 ohm is considered first-class. Deeper the Earth music director / rod the lower is the electric resistance value of the Earth cavity. Besides the Earth electric resistance is usually nearing nothing for Earth cavities which have the music director making land H2O tabular array or moist land.

The electric resistance of Earth cavity system so interrelated reduces and can be calculated by the undermentioned equation.

1 = 1 + 1 + 1. . . . . . . 1 Z Z1 Z2 Z3 Zn

Where Z is the entire electric resistance of the interrelated Earth system and Z1, Z2, Z3. . . .Zn are the earth electric resistance of Earth cavity 1, 2, 3 to earth pit N.

All interconnected earth cavities should be connected by a 70sqmm insulated Earth overseas telegram ( green / white ) or via tinned Cu flat at the lowest accessible point.

Minimum Earth opposition

At all locations where the Earth electric resistance is high, either the Earth rods should be bored deeper or multiple Earth cavities should be connected in analogue to hold the system earth electric resistance of less than 5 ohm.

Improvement of Earth opposition

For sites where the Earth opposition is high, the undermentioned steps can be taken to better the Earth opposition.

Multiple Earth cavities connected together.

Increase the deepness of Earth cavities / earth rods. Where of all time possible the Earth rods should be driven to make at least 2 to 3 pess below the H2O tabular array.

Use of dullard holes.

The Earth opposition is straight relative to the country of contact between the music director and the dirt. Where the boreholes or deep goaded Earth rods are non allowable ( impermanent sites ) , the Earth can be improved by supplying assorted methods as below.

Tinned Copper or Metal home bases. Multiple home bases can be provided and connected together. These home bases can be installed manually at a deepness of approx 1 metre below land degree.

Copper level Lattice. Works on same chief as above. Provides better country of contact between dirt and music director.

Use tinned Cu flat laid around site in a ring

Use of salt and coal mix around Earth rods – A mix of salt and coal is used to cut down dirt opposition and besides to retain wet for a longer clip.

Chemical Gel Earth – some companies have developed chemical gels which have first-class wet keeping features and besides increase dirt conduction. The chemical gels can be used after guaranting that the chemical used do non harm the environment adversely.

Watering the Earth pits – Any addition in wet content reduces the Earth electric resistance. The local Air conditioning drains can be directed towards the Earth pits to better dirt conduction. Alternatively a government for staff to H2O the high opposition sites during visit can be followed so that Earth opposition improves.

Size of down music director and Earth music directors

Lightning work stoppages consequence in dissipation of really big sum of electrical energy thru the lightning music director. In a few micro seconds big sum of electrical energy discharges thru the down music director which should be of equal size and connected straight to land. As a criterion all lightning down music directors should be insulated 70sqmm isolated Cu overseas telegrams.

The Earth music directors from the assorted other Earth cavities to the coach bars should be insulated 35smmm isolated Cu overseas telegrams.

The interconnectedness overseas telegrams between assorted Earth cavities should be done under land at lowest degrees with 70sqmm canned Cu music director. If tinned Cu is non available so a tinned Cu flat or insulated Cu music director may be used.

The inside informations of assorted connexions and overseas telegrams are shown in Table 2. Other overseas telegrams can be sized depending upon mistake degrees and equipment evaluations as recommended by the maker.

Connections and exothermal welding

All interconnecting music directors should be decently bonded together sooner via exothermal welding / Brazing. Hydraulically crimped connexions are besides required to keep low opposition connectivity between wire and connections.

All connexions to the land rod shall be exothermal / brazed or an sanctioned compaction connexion to supply low electric resistance connexion.

All connexions buried or exposed should be protected with an anti corrosion merchandise.

Separate Earth cavity for Lightning

The down music director should be straight connected to a separate lightning Earth cavity in order to hold a shortest and low opposition way from the lightning funnel to the Earth electrode so that the lightning current can be safely released to the Earth. Any Sharp decompression sicknesss and articulations should be avoided in the down music director so as to keep the least electric resistance.

The Earth cavity system for the down music director should hold the minimal electric resistance of all the other nearby earthing systems so that the lightning discharge takes the way of least electric resistance.

Isolation of lightning down music director

The lightning down music director should be isolated from the other electrical anchoring / Earth system.

Labels and designations.

“ Do non unplug ” mark should be displayed or printed near all connexions.

All Earth cavities should be labeled and Numberss and besides identified on site layout drawings.

Distance between the Earth cavities

The Earth cavity of lightning protection system should be as far off from other Earth points.

The distance of two Earth cavities should be greater that the maximal length of one of the Earth music directors. A minimal distance of 10-15ftt should be kept for little secret plans.

For Earth cavities connected in a ring / aura manner a minimal spacing of 10 to 15 pess should be maintained between the rods.

Separation OF LIGHTNING EARTH PIT

The lightning Earth cavity should be at least 7 metres off from other electrical Earth cavities.

Anchoring Rods and stuffs

The 5/8 inch Defense Intelligence Agency. Solid Stainless steel rods of Cu clad steel rods should be used. The chromium steel steel rods should run into ANSI rate 32 or 34 which is immune to corrosion. Bare or galvanized steel rods should non be used as land rods.

Tinned Cu wires are preferred for exterior usage over the commercial class Cu as they provide a better life due to resistance to corrosion. Aluminum wires are prohibited.

Trial points

A trial point should be provided in all down music directors and Earth cavities to look into the continuity of Earth and to look into electric resistance of single Earth cavities.

Interconnection of all Earth cavities and anchoring systems as per NEC

A direct lightning work stoppage on any tower or monopole or an Earth system shall increase the land electromotive force environing the Earth pit up to a few million Vs. This induced electromotive force shall usually impact all Earth cavities within a radius of 15 metres and may make flash over in the electrical equipment connected to these environing Earth cavities. NEC 250 recommends that all Earth cavities are interconnected, at the lowest degree as a ring, so that full land electromotive force of any system addition by same increase degrees and therefore avoid any flash over.

The Lightning Earth cavity ( connected to the down music director ) may be interlinked to the other Earth cavities connected as a ring via a flicker spread isolation.

Commercial power supply Neutral

Neutral of commercial power supply should ne’er be connected to the premises land system except at the distribution transformer Y ( for DY transformers ) .

Generator / Alternator impersonal

For switched Generator sets with 4 pole ( TPN ) disconnect the alternator impersonal should be decently grounded and connected to the AC equipment land. In instance of three pole exchanging ( TP ) where the neutral of the power beginning is ne’er disconnected, if local codification licenses, the alternator impersonal should be connected to the commercial supply impersonal and in such a instance the Alternator impersonal should ne’er be connected to the AC equipment land.

UPS Supplies

For UPS supplies or invertors with insulating transformer are considered as a individually derived system and their impersonal ( on Secondary Delta side ) should be solidly connected to the equipment land.

Earthing Bus bars

All AC DBs, MDBs should be provided with a land coach saloon for the intent of supplying a convenient terminating point for the AC equipment land. The anchoring coach saloon is mounted inside the enclosure so that is electrically bonded to the enclosure. If no land coach is provided by the provider so same should be provide by the installer.

Earth cavity systems for telecom / GSM sites

A distant telecom or GSM site with tower / monopole should hold four Earth cavities ( system ) as below.

Earth cavity ( system ) for lightning for tower / edifice

Earth cavity system for DC +ve land, tower / mast organic structure, RF overseas telegram foundation, antenna / microwave dish land, BTS & A ; telecom single-foot organic structure land.

Mains power equipment land, shelter organic structure land

Impersonal Ground for Generator sets.

The pulling 1 & A ; 2 show the connexion and inside informations of overseas telegrams to be used for interconnectednesss of assorted Earth cavities.

Anchoring of Antenna, Microwave dishes

The organic structure of all Antenna and Microwave dishes shall be grounded to an insulated land busbar. The land saloon shall be farther connected to the Earth cavity system for the DC +ve land of the telecom equipment / BTS. The inside informations are provided in Attached Drawing No. 1

Anchoring of Co axial overseas telegrams

The outer music directors of all the coaxal overseas telegrams which run from the construction are bonded every 40 to 50 metres: at their upper terminals, at the point of entry into the equipment edifice or cell, and at every 40 to 50 metres in between along the length of the overseas telegram. The bonding should be done utilizing a coaxal rush arrestor connection. All such connections shall be connected to a Bus saloon which is further connected to the Earth cavity system used for the DC +ve land of the telecom equipment / BTS. The inside informations are provided in affiliated Drawing.

Data Communication Cables

These overseas telegrams when attached to the aerial should be routed through the mast so as to forestall exposure to direct lightning rushs. Since the information lines are susceptible to transient over electromotive forces, as a general regulation, all the entrance and surpassing informations communicating, signal and telephone lines should be provided with suited transient rush defenders.

Protection from induced currents

All the informations and telephone lines must be off from power supply and lightning protection systems.

The coaxal overseas telegram from the tower besides separated by a minimal distance of 50 centimeter from the lightning protection system. The organic structure of the tower is besides considered as lightning protection system.

Rush Protection on Mains Power Protection

Indirect Lightening work stoppages on nearby power lines, arc-welding machines, and unexpected electromotive force fluctuation create surges in the power system and can do jobs to the unprotected electronic equipment. These rushs can come in the unprotected powersystem inside edifices by assorted methods. The rushs should be stopped at all edifice power entryway so as to forestall harm to sensitive equipment. Most LV power system ( 230/415 V ) and the electronic and electrical equipment can defy rushs of approx 2 to 3 three times the extremum operating electromotive force.

Rush protection devises should be installed at appropriate locations in the electrical system to dispatch the high electromotive force surges to the land.

Color cryptography of Earth overseas telegrams

All above land insulated earth overseas telegrams should be colour coded Yellow / green. Insulated Cu overseas telegrams are preferred as they shall avoid any escape of induced electromotive forces into other environing systems.

The belowground Earth music directors used for interconnectedness of Earth cavities should be solid au naturel music director of 70 sqmm. Copper flat of tantamount size may be used alternatively of overseas telegrams.

Roof top Installations

Roof top installings are more susceptible to lightning work stoppages and hence should be adequately protected by proper foundation of all exposed metal parts.

The Antenna and micro-cook dishes should be protected from lightning by proviso of lightning music directors fixed above them. The tallness of such music director should supply a 30 deg. Umbrella protection and cover each aerial and dish. Separate music directors should be used for different delta stands or constructions. The lightning music directors should be connected in a ring manner and farther connected to the edifice lightning down conductivity. If no down music directors are available so the “ Ring ” should be connected via a dedicated down music director to the Earth cavity.

Two separate Earth music director should be laid and used for anchoring the “ Clean Earth Bus ” and the “ Main Earth Terminal coach saloon ” .

PERIODIC INSPECTION AND RECORDS

The lightning protection and the electrical Earth and anchoring system should be inspected as per the agenda below.

On commissioning

Every six months after commissioning ( twice every twelvemonth ) .

Following records should be maintained at site degree and at part office. These records should be inspected by quality review squads. A verification of sites tested and maintained should be sent every six months to the HO subdivision.

Site layout demoing earth cavity location

Single line diagram with Earth cavity interconnectedness inside informations and land overseas telegram.

Site Earth pit opposition measuring. History to be maintained for each site as per format in Table 1

Table 2 provides the inside informations of interconnectednesss and the duty of assorted Etisalat subdivisions

Table 1:

Site Name

Date of trial

Earth System

Earth pit No.

Earth cavity deepness

Resistance of single Earth cavity

A Resistance of Earth Pit system joined togetherA

A Lightning

A

A

A DC +ve

A

A

Commercial Power + equipment Earth

A

A

Generator impersonal

The trial papers to be filled and transcripts kept at site / part office.

A

Tested byA Verified by

Table 2

Sr.

Earth Pit / System

Description of Earthing connexion

Connection overseas telegram

overseas telegram size Sqmm

Duty

from

To

Shelter and equipment

1

Earth Pit 1

Shelter indoor Earth Bus saloon ( +ve DC land )

DC Earth coach

Bus Bar 3

35

Shelter contractor

2

Rectifier Body

DC Earth coach

Rectifier Body

35

Rectifier provider

3

BTS Body

DC Earth coach

BTS organic structure

35

BTS installing squad

4

TX rack

DC Earth coach

Texas rack

35

TX rack installing squad

Monopoles and Towers

5

Earth Pit 1

Bus Bar 1 ( at Antenna / Dish degree )

Antenna / Dish

Bus Bar 1

35

Mobile rigger

6

Bus Bar 2 ( every 40 metres ) for RF connections with rush suppression.

RF Connector

Bus Bar 2

35

Mobile rigger

7

Bus Bar 3

RF Connector with rush suppression

coach saloon 3

35

Mobile rigger

8

Interconnection between Bus saloon 1, 2, and 3

Busbar 1, 2

Bus saloon 3

35

Mobile rigger

9

Bus Bar 3 to Ground Pit 1

Bus Bar 3

Land Pit 1

35

Power Plant / Efm

10

Earth Pit 2

Lightning Arrestor

Lightning Arrestor

Earth Pit 2

70

Tower contractor

15

Earth pit 3

Mains Power Earth ( available from Dewa / ADWEA )

MDB / Shelter organic structure

Earth Pit 3 & A ; 4

35

Power Plant / Efm

11

Shelter organic structure Earth

Shelter Body

35

Power Plant / Efm

12

Tower monopole / overseas telegram tray construction

construction

35

Power Plant / Efm

13

Generator Earth ( Provided by Etisalat ) pit 4.

Generator Body

Genset Body

35

Power Plant / Efm

14

Generator impersonal Earth

Generator impersonal point

35

Structure contractor

Duty of interconnectedness between all cavities at land degree by Etisalat Region PP / Efm.