Grounding_Standards.PDF

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ENGINEERING

PROJECTSDEPARTMENT

ENGINEERING STANDARDSGROUNDING IN TECHNICAL FACILITIES

DRAFT

The True University Of These Days Is A Collection Of CD-ROMs(Apologies to Thomas Carlyle)

By Guy Lakeman

THE CONVERGENCE COMPANY LIMITED.


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ENGINEERING PROJECTS DEPARTMENT:

Submitted to: THE CONVERGENCE COMPANY LIMITED

Submitted by: Guy Lakeman

Date: 02/03/98

ENGINEERING STANDARDS

GROUNDING IN TECHNICAL FACILITIES TABLE OF CONTENTS

TABLE OF CONTENTS

STATEMENT ...........................................................................................................................0

INTRODUCTION AND SUMMARY ...........................................................................................0

GROUNDING...........................................................................................................................0LIFE SAFETY GROUNDING....................................................................................................................................... 0

GROUND FAULT PROTECTION .................................................................................................................................................0

LIGHTNING PROTECTION ........................................................................................................................................................0

ELECTRICAL NOISE - CONTROL GROUNDING ........................................................................................................... 0

SINGLE-POINT GROUND SYSTEM ............................................................................................................................................0

TRADITIONAL TRUNKING IMPLEMENTATION DRAWING................... ...................... ..................... ..................... ..................... ..................... 0

TRADITIONAL CONNECTIVITY IMPLEMENTATION DRAWING ................... ...................... ..................... ..................... ..................... .............. 0

MULTI-POINT GROUND SYSTEM..............................................................................................................................................0

CELLULAR RAISED FLOOR AND ZSRG (ZERO SIGNAL REFERENCE GRID) ............................................................................................... 0

CABLE TRAYS AND STGP (SIGNAL TRANSPORT GROUND PLANES) ........................................................................................................ 0

SIGNAL CONDUIT ..................... ..................... ..................... ..................... ...................... ..................... ..................... ...................... ...... 0ISOLATION TRANSFORMER WIRING.................... ...................... ..................... ..................... ...................... ..................... ..................... ... 0

LIMITING OF HIGH VOLTAGE ....................................................................................................................................................0

HUMIDITY CONTROL .................... ..................... ...................... ..................... ..................... ...................... ..................... ..................... ... 0

FLOOR SURFACE CONDUCTIVITY .................... ..................... ..................... ...................... ..................... ..................... ...................... ...... 0

ELECTROSTATIC DRAIN PATHS .................. ...................... ..................... ..................... ..................... ...................... ..................... .......... 0

REFERENCES.........................................................................................................................0


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GROUNDING IN TECHNICAL FACILITIES STATEMENT 1

STATEMENT

Two forms or grounding are discussed here and comparisons made.

Although traditional earth bus with star and spur distribution (no loop) earthing has been proven with what arenow considered to be low frequencies (5MHz and below) digital systems are currently in operation in the150MHz region for standard definition television. This will soon rise to 750MHz when large scale full bandwidthhigh definition systems are implemented.

The signal systems associated with broadcast television video and audio signals can be compared to those ofthe medical electronics profession.

Whereas television signals do not enter the realms of being life threatening if distorted or polluted with noise theBroadcast Engineer can be in the realms of being severely threatened by his or her CEO.


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GROUNDING IN TECHNICAL FACILITIES INTRODUCTION and SUMMARY 2

INTRODUCTION and SUMMARY

The foIlowing discussion has been taken from the Engineering Standards and Vade Mecum and FacilityConstruction Guidelines developed by The Convergence Company Limited.

This document addresses the problems associated with the development of facilities where very highfrequencies need to be drained to earth in order to produce a noise free environment.


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GROUNDING IN TECHNICAL FACILITIES GROUNDING 3

GROUNDING

Grounding requirements for Television Production facilities fall into the categories of:

Life Safety,

Electrical Noise Control and the

Limiting of High Voltage.

Although distinct in function the grounding systems that are implemented in a building servicing large technicalsystems, such as those found within a television broadcast or production facility, are not separable.

An overall systems approach to the grounding requirements must be developed and universally adhered to as tosatisfactorily address Life Safety code regulations, equipment protection and electrical noise controlrequirements. These multi-faceted requirements of Grounding often causes confusion and misapplication ofelectrical codes and further, usually result in unsafe conditions and poor electrical noise control in large systems.

LIFE SAFETY GROUNDING

Fire Protection Refer to applicable local code regulations

Electrical Shock Avoidance - Refer to applicable local code regulations

GROUNDFAULTPROTECTION

A shock hazard exists if a power conductor faults to a metallic equipment housing. If the housing is not at a lowimpedance back to the overcurrent protection device the housing remains unsafe. To avoid this possibility, allmetal surfaces that may encounter a power conductor must be bonded together and connected back to thebuilding grounding electrode system via a low impedance path.

L IGHTNINGPROTECTION

Refer to applicable local Lightning Protection code regulations.

Lightning pulses can carry currents in excess of 100,000 amps. The best protection plan is one that provides aconvenient and direct path for the lightning current to flow to earth. This path must be deliberately designed andinstalled with the intent purpose of providing a very low inductance for the lightning current. In addition to highcurrent flows within the building, magnetic fields developed by these current flows can induce currents intoelectronic circuits. Shielding of circuit paths and maintaining low impedance bonding of the shielding system,grounding grid system, building steel and the lightning protection grounding electrode system provides the bestoverall protection. Separate non-bonded ground systems within the building can become sources of largegradient potential differences and therefore must not be allowed to exist.


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ELECTRICAL NOISE - CONTROL GROUNDING

It is imperative to note and to understand that electronic equipment does not require connection to any earthground to function properly (i.e., OB Truck systems running on generator power and Communication Satellites in

space function without an earth ground connection).

The principle task of a ground system designed to control electrical noise is to provide a grounding (noconnection to earth implied) platform that is common to all technical elements that operate within the system,and one that equalises any and all potential differences across the platform throughout the full operatingfrequency range of the equipment. The requirement to connect this ground platform to an earth ground is a LifeSafety and Building Code issue that must be addressed. The notion that the earth ground will "absorb" or "sink"all noise currents is false. The laws of physics, in particular Kirchoffs Current Law, demand that currentscirculate and that what goes in (the earth) must come out.

Beyond the Life Safety considerations, noted above, within a Television Production facility the next priority in thegrounding system design must address that of Electrical Noise Control. This is a very difficult task due toseveral operational parameters that co-exist in the systems that the grounding system is in place to protect andaid.

First, the system is large. It will contain many signal paths, many of which contain unbalanced grounded paths.Second, the base band operational frequencies of the in-building signal paths range from DC to over 30 MHz.This is a very wide spectrum to protect from electrical noise intrusion, both externally and internally generated.

SINGLE-POINTGROUNDSYSTEM

Tradi t ional Trunking Implementat ion Drawing

TECHNICAL AREA

TRADITIONAL TECHNICAL EARTH GROUNDING SYSTEM - BUSS STAR SPUR.

Guy Lakeman - The Convergence Company 1998

MAIN STAR

LOCAL STAR

LOCAL STAR

TDB

MONITOR STACK

OPERATOR

CONSOLE

LIFTS

CANTEEN

MOTORS

ETC

H&V

TECHNICALPOWERWITHEARTH

TECHNICALEARTH

BUILDINGPOWERWITHEARTH

BUILDING EARTH

LIGHTING

LIGHTING

TELCO

IT

FORBIDDEN CROSSOVER

FORBIDDEN CROSSOVER

ALL TECHNICAL

RACKS, CONSOLESAND MONITOR

STACKS MUST BE

ISOLATED FROM THEFLOORING AND

BUILDING SURFACES


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Tradi t ional Conn ect iv i ty Implementat ion Drawing

TECHNICAL AREA

TRADITIONAL TECHNICAL EARTH TRUNKING SYSTEM - BUSS SPUR.

Guy Lakeman - The Convergence Company 1998

MAIN STAR

LOCAL STAR

BUNDLE

LIFTS

CANTEEN

MOTORS

ETC

H&V

TECHNICALPOWERWITHEARTH

TECHNICALEARTH

BUILDINGPOWERWITHEARTH

BUILDING EARTH

LIGHTING

TELCO

IT

OPERATOR

CONSOLE MONITOR STACK

NO DIRECT CONNECTIONS BETWEEN GREYAREAS OR TO BUILDING GROUND

ALL TECHNICALRACKS, CONSOLES

AND MONITORSTACKS MUST BE

ISOLATED FROM THEFLOORING AND

BUILDING SURFACES

Historically the typical approach in addressing electrical noise control in a Television Production facility has beento utilize a Single-Point ground system (i.e., "Production Systems Ground", "Clean Ground" or "TechnicalGround"). Much of the noise present in a facility grounding system is usually traceable to the primary, 50 or 60HZ, power system. Single-Point grounding can be very effective in controlling this situation and has been oftensuccessfully employed in smaller systems. However, in a large installation a major disadvantage of the Single-Point ground configuration is the requirement for long runs of the grounding conductor. These long runs (i.e.,any ground run over 20 feet) prevent the realization of maintaining a satisfactory low impedance reference planeat higher frequencies.

Longer runs of greater than 20 feet, up to 100 feet, can be achieved by using stranded earth cable to maximisethe surface area of the conductors. High frequencies migrate to the surface of a conductor. Multi strandedcables allow these frequencies a larger area to flow so reducing their impedance to earth.

The key word here is impedance. Although the ground conductor may provide a low resistance path, noisephenomena is minimal at DC. How the grounding conductor acts at higher frequencies, 50/60 HZ to 30 MHzand above is the predominant concern.

The goal of the grounding system is to maintain low impedance throughout the entire 50/60 Hz to 30 MHz andabove frequency range and therefore the ground conductors inductance and capacitive coupling are a majorconcern. No single conductor can drive a ground plane to be at the same potential at a remote ground point.The only way this can be approached is to extend the ground plane, low impedance path to the remote point.


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Impedance, Z, is the term used to describe the opposition to current flow when resistance, inductance andcapacitance are considered in combination and is expressed as

( )Z R X XL C= + +2 2

The inductive reactance, XL, developed by a Single-Point ground conductor is

X fLL = 2

Where C is the inductance of the cable and f is the frequency of concern.

The capacitance reactance, XC, developed by a Single-Point ground conductor is

XfC

C =1

2

Where C is the capacitance of the cable and f is the frequency of concern.

The key here is the effect that frequency has on the impedance.

For example,

The resistance of a #10 conductor is about 0.01 ohm per 10 feet (3 metres). Whereas its inductance isabout 3.5 H per 10 feet. At 1 MHz this is 22 ohms.

A 3/0 conductor has a resistance of about 0.0006 ohm per 10 feet, very low, but at 1 MHz its impedance is18 ohms.

Thus heavy conductors are not the answer to low impedance for the grounding system. Multiple sets ofconductors and connections are required.

Further complicating a large Single-Point grounding system is the accumulative effect of stray capacitancebetween conductors and the building. This effect on single conductors, at high frequencies, essentially rendersthe grounding system useless.

A most noteworthy fact regarding the Single-Point technique is that under its "proper" implementation techniqueit represents an electrical code violation in the United States and in most international communities.

Utilizing a single "Technical Ground" conductor connected to each rack and/or console requires that theelectrical safety ground to each equipment component in the system be disconnected to prevent loop currents.This is not only a code violation but more importantly it creates a serious Life Safety defect in the Ground FaultProtection system.

In order to rectify this violation a technical earthing spike must be driven near to the building ground. In mostcountries these earth spikes are connected together at their proximity to meet regulations. (Although thetechnical earth does not require connection to the building earth if the earth spike does meet life safetyregulations)

An additional consideration in applying a Single-Point grounding scheme is that strict attention must be paidthrough all phases of installation, operation and maintenance to assure that the single-point configuration isretained. This can become a very difficult task in a large facility manned by numerous personnel over aprolonged period of time. Especially where several disciplines coincide, e.g. Broadcasters, Telcos, IT, etc.

Thus dependence upon a Single-Point Ground system for a large and complex technical facility, is not a sound

approach.


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MULTI-POINTGROUNDSYSTEM

The alternative approach to address electrical noise control in a Television Production facility is to utilise a multi-point grounding system. This configuration establishes numerous conductive paths between system

components and sub-systems. As discussed above, the development of a ground platform that provides forequalizing voltage potentials across the platform is a method that approaches that of a solid ground plane. Italso represents a more practical solution to grounding in a large facility since its guidelines for implementationfollow a common sense, logical approach and adhere closely to applicable electrical codes. Further, thisapproach integrates Life Safety, the Limiting of High Voltage and Electrical Noise Control groundingrequirements.

The key elements of this multi-point grounding system are a Zero Signal Reference Grid, ZSRG, and SignalTransport Ground Planes, STGPs. Implementing these grids and ground planes will form the basis of a qualitytechnical grounding system throughout the facility.

Facilities utilising areas of cellular raised flooring and cable tray systems for signal transportation, alreadycontains these key elements It is therefore a straight forward task to implement a successful multi-point groundsystem.

Below, each element of the Multi-Point grounding system is discussed in detail as to how it should be installedand utilised.

Also refer to the Figures for assistance.

Cellular Raised Floor and ZSRG (Zero Signal Reference Grid)

The cellular raised flooring system to be installed in the facility will provide the foundation for the ZSRG. Thechamber formed by the flooring system not only provides access to and a path for signal cables or as acomponent of the facilities HVAC system as a supply or return air plenum, but it also provides the foundation forthe ZSRG. The Cellular flooring system, if correctly installed, can become the ZSRG or it can provide the spacefor the installation of a sub-floor level ground grid system that provides the electrical function of the ZSRG.

Should the Cellular Flooring system be intended as the ZSRG it must be implemented utilizing bolted downlateral support braces or stringers and it must be solidly connected to the facilities electrical ground system. Thisconnection requires that the Cellular Floor Pedestals be electrically bonded, every fourth pedestal will due, to thefacilities building grounding electrode system.

The preferred method is to install a sub floor grid system. The laid grid shall be made of #4 AWG (or equivalent)bare copper conductor laid directly on the slab floor on 24 inch (600mm) centers electrically joined at theirintersections and around the perimeter. It shall extend under all areas of the raised flooring system.

Note: A new product line manufactured by Cadweld of Erico Products, Inca., Cleveland, Ohio is now availableusing 26 AWG copper strips Cadwelded on 2 foot centers, This product line should be explored as a preferredalternative.


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ZSRG - ZERO SIGNAL REFERENCE GROUND - TYPICAL GROUNDING

Guy Lakeman - The Convergence Company Limited 1998

2

1

2

3

4

5

6

1

2

3

4

5

#6 SDBC (16 mm sq)

CONNECTION KEY FORSDBC

(SOFT DRAWN BARE COPPER)

#4 SDBC (25 mm sq)

#2 SDBC (35 mm sq)

#4/0 SDBC (95 mm sq)

LOW IMPEDANCE RISER

3

FURNISH AND INSTALL A 25 mm2 SOFT-DRAWN BARE COPPER CONDUCTOR (SDBC) ON THEEXTERIOROF THECABLETRAY. FASTENTHISCONDUCTORTOTHE EXTERIOROFTHECABLE TRAYATNE METREINTERVALSWITH NYLONSELF-LOCKINGTIEWRAPS. THE25 mm2CONDUCTORSHALLBEEXOTHERMICVALLYWELDEDON BOTHSIDEDOFALL CABLETRAYJOINTS

FURNISHAND INSTALLA 25mm2 SDBCCONDUCTORBETWEENTHECABLETRAYAND ANYBUILDINGSTEELOR LIGHTNING PROTECTION DOWN CONDUCTORWITHIN 1800 mmOR LESS OFTH ECABLETRAY. THE25mm2 SDBCCONDUCTORSHALLBEEXOTHERMICALLYWELDEDBETWEENTHE25 mm2SDBCCONDUCTORONTHE EXTERIOROF THECABLETRAYANDTHE BUILDINGSTEEL.

ALLOPENBOTTOMTYPE LADDERCABLETRAYSSHALLHAVE22-GAUGEGALVANISEDSHEETSTEELLAIDIN THE BOTTOMOFTHETRAY ANDWELDEDTOTHE TRAYEVERYMETRE(WIREFED WELD). IFSOLID BOTTOMCABLETRAYIS USED THEN THE22-GAUGEGALVANISED SHEET STEEL IS NOTREQUIRED. THECABLE TRAY SHALLBE ASSEMBLEDUSING A FLAT WASHERANDA SPLITLOCKWASHERWITH THEASSEMBLYHARDWARETO PROVIDE A HIGH PRESSURE, LOWRESISTANCECONNECTION.

A 22-GAUGE GALVANISEDSHEET STEELSTRIPSHALL BEUSED TO TRANSITIONWITH THESIGNALCABLESFROM THECABLETRAYTO THEELECTRONICEQUIPMENTRACK. THESHEETSTEEL STRIP

SGHALLBE ATLEAST300 mmWIDE. THESTRIPSHALLBE FASTENEDTO THECABLETRAYAND THERACKWITHPOPRIVETSAT THREELOCATIONSATEITHEREND.

EXOTHERMICALLYWELDA 16mm2 SDBCCONDUCTORTO THESRG ANDRAISEDFLOORPEDESTALBAS. EXTENDTHEBASEENDOF THE16mm2 CONDUCTORUPTH EPEDESTALANDACROSSTHEJAVCKSCREW. BONDTHE 16mm2CONDUCTORTOTHEUPPERPORTIONOFTHE PEDESTALWITHASTAINLESS STEEL WORM GEAR TYPE CLAMP. USE AN ANTI-OXIDANT PASTE AT THIS POINTBETWEEN THEWIRE ANDTHE PEDESTAL. SECURE THE16 mm2CONDUCTOR TO THEPEDESTALWITHSELF-LOCKINGNYLONTIE WRAPS.

2

2

1

1800MMORLESS

SIGNAL

CABLES

ELECTRONIC

EQUIPMENT

RACKS

RAISED

FLOORINGBUILDING

STEEL

BUILDING

STEEL

GALVANISED

STEEL LADDER

CABLE TRAY

CHANNEL TYPE

SUPPORT STEELWITH ALL

THREADED RODS

TO STRUCTURAL

CONCRETE

CEILING

RAISED

FLOOR

PEDESTAL

SIGNAL

REFERENCE

GRID

(SRG)

2

1

1800

MM

OR

LESS

1800MMORLESS

2

6

7

2

2

2

1 1

1

2

7EXOTHERMICALLYWELDA 16mm2SDBCCONDUCTOR TOTHESRG ANDALLEXPOSEDBUILDINGSTEELS.

1

FURNISH ANDINSTALLTWO LOWIMPEDANCESTRAPSFROMEACH ELECTRONICEQUIPMENT RACKTOTHE SRG. THELIR SHALLBE BOLTEDTO THEELECTRONIC EQUIPMENTRACK FRAME ANDEXOTHERMICALLY WELDED TO THE SRG. THE LENGTH OF LIR SHALL BE KEPT AS SHORT ASPOSSIBLEWITHNICE SWEEPINGCURVATURE.

4

5

5 5

55

1

Cable Trays and STGP (Signal Transpo rt Groun d Planes)

The metal cable trays that will be utilised to transport signal cables throughout the facility will form the basis ofthe STGP system. Proper installation of the trays is paramount to receive the benefits of cable transportshielding and grounding.

All cable tray runs shall originate at the ZSRG. If the cable tray is destined for the ceiling space above the raisedflooring system, it must run contiguous from the ceiling space down a wall or chase and to the raised floor spaceand the ZSRG. It shall then be bonded to the ZSRG.

The cable tray system implemented shall be listed by the manufacture for this electrical application. To maintainlow impedance throughout the trays run length, it shall be assembled utilizing Bellvill washers with the assemblyhardware as to maintain the pressure connections. Additionally all sections of the tray system shall be bonded

together. This should be accomplished by running a #4 AWG copper conductor in parallel with the tray andelectrically connecting each section to the conductor.

At terminating ends of the cable tray system, the cable tray shall follow the signal cables to the rack, console orremote ZSRG where the signal cables will terminate and be bonded to the rack, console, ZSRG or junction boxat that location.

As cable trays are routed throughout the building they shall be bonded to any intersecting or adjacent buildingsteel, conduit, metal piping and metal race way.

If any tray sections pass within 6 feet (180Omm) of any lightning protection system conductors, the cable trayshall be bonded to the lightning system ground conductor at that point.


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Signal Condui t

In areas of the building where signal cables must terminate and it is impractical or impossible to complete therun with cable tray, metal conduit shall be used. This conduit shall be connected and bonded to the cable trayand/or the ZSRG at its point of origin, at all intersections with building steel and at the terminating end toadjacent metal enclosures and/or junction boxes.

As signal conduits are routed throughout the building they shall be bonded to any intersecting or adjacentbuilding steel, other conduit, metal piping and metal race way.

Isolat ion Transformer Wiring

TECHNICAL GROUNDING - ISOLATION TRANSFORMER WIRING


LINE 1

LINE 3

LINE 2

NEUTRAL

TYPICAL DEDICATED ISOLATION TRANSFORMER

EQUIPPED WITH ELECTROSTATIC SHIELDS A

DELTA PRIMARY (INPU) AND A WYE CONNECTED

SECCONDARY (OUTPUT)

E

IE

E

E

AC SYSTEM

GROUNDING

ELECTRODE

CONDUCTOR IN METAL

CONDUIT

SHIELDS

WHEN A METAL

RACEWAY IS USED TO

ENCLOSE THE AC

SYSTEM GROUNDING

ELECTRODE

CONDUCTOR, IT IS

REQUIRED TO BE

GROUNDED/BONDED T O

THE ENCLOSURE

CONDUCTOR EXACTLY

AS SHOWN

INPUT FEEDER

CONTAINED IN MENTALCONDUIT. 3-WIRE + E AS

SHOWN.

FROM AC SUPPLY TO LOAD

SOLIDLY GROUND/BOND ALL

CONDUITS TO THE METAL

ENCLOSURE OF THE

TRANSFORMER IA ALL CASES.

DO NOT USE INSULATION

OUTPUT FEEDER CONTAINED

IN METAL CONDUIT. 4-WIRE +E

+IE AS SHOWN.

ALL CONDUCTORS MUST BE

CARRIED IN THE SAME

CONDUIT AND CAN ONLY BETERMINATED WITHIN THE

EQUIPMENT THE OUYPUT FEED

IS SERVING.

MECHANICAL

CONNECTION

TO FRAME

ENCLOSURE

FRAME OF

TRANSFORMER

SIGNAL

REFERENCE

GRID

EARTH BUS BAR

MOUNTED ON WALL

ADJACENT TO

TRANSFORMER

BUILDING STEEL CLOSEST TO THE EARTH

BUS. IF BUILDING STEEL IS NOT AVALABLE IN

THE AREA, THEN MECHANICAL BOND THE 95

mm2 CONDUCTOR TO AN ADJACENT 254 mm

OR LARGER COPPER COLD WATER PIPE

25 mm2

95 mm216 mm2

25 mm2

G

Weld

MechanicalM.O.D. standard

def stan 052.

When bonding, use spring

washers, flat washers and a

star washer which bites into

the copper strip.


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Technical and UPS Power Distr ibut ion

TECHNICAL AND UPS POWER DISTRIBUTION


MAIN SWITCHBOARD PANELSTEPDOWN - ISOLATIONTRANSFORMER, POWER

CONDITIONER OR UPS

TECHNICAL CIRCUIT

DISTRIBUTION PANELEQUIPMENT RACK OR CONSOLE

G

N

G

METALWIREWAY

IGRECEPTICAL

IGPOWERDISTRIBUTION

STRIP

EQUIPMENT

LOAD BOLTED

TO RACK RAIL

RACKRAIL

RACK - CONSOLESTEEL BONDED

TO RACK RAIL


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L IMITING OFHIGHVOLTAGE

The limiting of high voltage build up which will result in Electrostatic Discharge, EDS, is a very importantconsideration in all areas of a Television Production and Broadcast facility because of the sensitivity of the

electronic circuits found throughout the building.The average operational personnel is not sensitive to a discharge until it exceeds 8,000 to 10,000 volts, this levelof discharge wilt create a spark gap of about one-half an inch and contains approximately l/l00 of a Joule ofenergy.

l/l000 af a Joule, 10 times less energy than can be felt in a discharge, is more than enough to destroy anintegrated circuit or to disrupt an electronic signal. Discharges in the range of 2,000 to 4,000 volts are notperceivable to operational personnel but do contain sufficient energy to cause problems. Therefore, systemelements must be designed and implemented within the Studio facility to limit the build up of high voltages. Thefollowing system elements will control EDS problems:

Humidi ty Contro l

Implement humidity control throughout the Television Production facility as to maintain the relative humidity at 50%. At no time shall the interior relative humidity be allowed to fall below 40% or rise about 65%.

Floor Surface Conduct iv i ty

Floor surface conductivity is a controllable element which can prevent or limit the electrostatic build-up onoperational personnel and mechanical units that travel across them.

Nylon, Acrylic and Polyester carpets and Vinyl Asbestos tile must be avoided.

Carpeting, with low propensity to electrostatic build-up, containing conducting fibers and un-waxed pressurelaminates must be utilised.

Electrostat ic Drain Paths

The most critical areas for controlling electrostatic build-up within the facility are those also serviced by thecellular raised flooring system. By nature of its design and integration with the grounded ZSRG, this flooringsystem will provide sufficient electrostatic drain paths provided that the cover material, carpeting and/or pressurelaminates are conducting and un-waxed, as discussed above.


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GROUNDING IN TECHNICAL FACILITIES REFERENCES 13

REFERENCES

IEE Regulations

R.Mossison and W.H. Lewis, Grounding and Shielding in Facilities, John Wiley and Sons inc.,1990

U.S. Department of Commerce. FIPS Guideline on Electrical Power for ADP Installations, FIPS PUB 94.

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