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Grounding and Bonding in Grounding and Bonding in Communications SystemsCommunications Systems

David Brender, P.E.Copper Development Association Inc.

david.brender@copperalliance.us

Ennes WorkshopSacramento, February 23, 2013

©MMXIII©MMXIII

This talk concentrates on:This talk concentrates on:

Interconnection of equipmentConnection to earth

Physics is physics everywhere

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Grounding and BondingGrounding and BondingGrounding and bonding are fundamental

components of power quality and reliability, and should be robust before you do anything else

GroundingGroundingGrounding is the intentional connection of the

electrical system to the “earth” or a body that serves in place of the earth

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BondingBondingBonding is the intentional interconnection of

normally non-current-carrying parts of electrical equipment to prevent shock and voltage differences in the event of a faultdifferences in the event of a fault

The terms “grounding” and “bonding” are sometimes used incorrectly and often interchanged.

Orange County, FL 911 systemOrange County, FL 911 system

Retrofit of existing sites

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Orange County, FL 911Orange County, FL 911

11 transmitter sites

Orange County, FL 911Orange County, FL 911HeadquartersApopka, FL

• Source: Power & System Innovations, Inc., OrlandoInnovations, Inc., Orlando

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Orange County 911 Orange County 911 -- ApopkaApopka

280 foot tower3 sets of 5 guysg y

Orange County 911 Orange County 911 -- ApopkaApopka$100 K/yr. damage at

Apopka alone

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Orange County 911 SystemOrange County 911 System$1-2 million equipment losses system-wide /year

Step 1 Step 1

Staff was not expert in power quality, ll d i k l d bl f i lcalled in knowledgeable professional

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3 Independent grounds3 Independent groundsun-maintained elec svc gnd

No connection

guys

60 Ωcoax

firewall

tower threaded rod

Refitted siteRefitted site

Everything bonded together

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Throughout The SystemThroughout The System

Ungrounded equipment cabinets

Facility ground at ApopkaFacility ground at ApopkaMain electrode was all-thread rod

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Old Apopka ground rodOld Apopka ground rodMeasured 550 ohms

Apopka Tower GroundingApopka Tower GroundingRetrofits:Deep (60 ft) p ( )electrode supplements tower

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Coax ShieldsCoax ShieldsCoax shield bonded to bus, to electrode systemy

Proper coax shield grounds:

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New bus on tower New bus on tower For coax grounds then 4/0 to electrode

Outside Outside FFirewallirewallOnly ONE Cu strip connected to electrode

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Outside FirewallOutside FirewallStrip bonded together and to ring with 4/0

At all Equipment CabinetsAt all Equipment Cabinets

Bond equipment properly

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Separate BondingSeparate Bonding

All equipment bonds brought to busesBuses tied to halo rings g

Reedy CreekReedy Creek

Remote repeaternear Disney Worldy

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Reedy CreekReedy Creek

More real estate to work with

Reedy CreekReedy Creek

Grounding layout: double rings plus deep electrodesdeep electrodes

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Orange County 911 Orange County 911 –– Reedy CreekReedy Creek

Each rod was d i ddriven deep enough to achieve < 5 ohms independently

Orange County 911 Orange County 911 –– Reedy CreekReedy CreekWide, sweeping turns

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Orange County 911 Orange County 911 –– Reedy CreekReedy CreekReplacing connections like this

Orange County 911 Orange County 911 –– Reedy CreekReedy CreekNote lock washer, double nuts

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OC 911OC 911

SPD’s on main serviceentrance

OC ExperienceOC Experience

• Thousands of events recorded• One strike witnessed

• NO Downtime! No equipment damage.

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Major lessons from OC 911 Major lessons from OC 911

3 different contractorselectrical

•radio room•towerNo one party had•responsibilityresponsibility

Major lessons from OC 911Major lessons from OC 911

Political control (low bid)No maintenanceMinimal design

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Power Quality is CostPower Quality is Cost--effectiveeffective

OC 911:

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KPTMKPTM--TVTV

Two 300 ft. towers adjacent to studioLightning strikes damaged $1,000’s of equipment, took station off the air.

KPTMKPTM--TVTV

Installed 2 electrodes at 125 foot deep3-ohm resistance3 ohm resistance

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KPTMKPTM--TVTV

Inspection well to test resistances

KPTMKPTM--TVTVSatellite dishes were not bonded to studio

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KPTMKPTM--TVTVRe-bonded all interior and exterior equipment:

Equipment racksSatellite dishesTowers

New ground bus

No damage•No damage•No downtime after retrofit

Sumter County 911Sumter County 911

2004 lightning strike t k t ti f ilittook out entire facility

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Tower had separate groundingTower had separate grounding121 foot tower erected in 2007Separate ground independent from buildingp g p g

230 ohms to ground230 ohms to ground

Building had single galvanized rod230 ohms

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Independent groundsIndependent grounds

2 emergency generators each had independent groundindependent ground

Hose clamp connection

Steel was not groundedSteel was not grounded

2 transformers were grounded to building steel, but steel was not bonded to ground electrodebonded to ground electrode

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Sumter County 911Sumter County 911

Complete renovation of bonding and grounding• Removed daisy-chained groundsy g• Ground system supplemented and tied

together• Building steel bonded to electrode

KKIT KKIT -- FMFM

Angel Fire, NMg ,

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Actual Tower groundingActual Tower grounding

Proper connection methods?

•KKIT-FM

Actual Connection to ground rodActual Connection to ground rod

Proper connection methods?

•KKIT-FM

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Actual Water pipe bondingActual Water pipe bonding

Corrosion and connection errors.

•KKIT-FM

Think of “current divider”Think of “current divider”

Energy

High R

Low R

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KPTH KPTH -- KMEGKMEG

1988 ft. towerNear S. Sioux City, NE

UferUfer ground after lightningground after lightning

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At tower baseAt tower base

2- 8 ft. ground rods190 Ω190 Ω

Ice bridgeIce bridge

#2 AWG connected to same rods

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Guy wiresGuy wires

Note double U-boltsConnectors not listedConnectors not listed90° anglesVibration

Guy groundingGuy grounding

Note right angles

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Guy groundingGuy grounding

New “listed” tin-plated silicon-bronze connectorsconnectorsParallel to guy wires

Guy groundingGuy grounding

3-80 ft. deep SS rods250 kcmil to ring250 kcmil to ring

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Ice bridgeIce bridge

Note rust

Strap has lower impedanceStrap has lower impedance

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ResultResult

One ground systemOne ground system

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Recommended PracticeRecommended Practice

Correct corrosion issues

Recommended PracticeRecommended Practice

Use bolt-in CB’s,not snap-inp

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Inadequate Tower GroundingInadequate Tower Grounding

Is Ufer EGC actually bonded to rebar?

Ground wire outside conduitGround wire outside conduit

Proper wiring methods?

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Separate Neutral and Ground Separate Neutral and Ground

Improper N-G bonds

Interior GroundingInterior GroundingLook for paint or other insulation

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After commissioning After commissioning

Check resistance to earth annuallyUnder 5 ohms is desirable

RulesRules

“Radial” bonding( d i h i )(no daisy-chains)

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Interior GroundingInterior GroundingThere should be ONE central point connecting the neutral to the ONE exterior grounding electrode systeme ect ode syste

Source: Dranetz Field HandbookSource: Dranetz Field Handbook

RulesRules

Earth is not a current path, i.e.: no independent ground paths

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RulesRules

No separate grounds – one grounding system

Desired GroundingDesired Grounding

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RulesRules

Equipment should be protected b SPDby SPDs

SPD SizesSPD Sizes

Type C Type B Type A• 150 kA 75 kA 25 kA /mode

/mode

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TakeawaysTakeaways

1. Exceed the Code, but don’t violate the Code!(Code minimum is one step above “illegal”)( p g )

2. You don’t get what you expect, you only get what you inspect.

3. Have a written plan and procedures. Insist contractors follow it.

3. Get the grounding and bonding right before anything else. Most lightning and transient problems can be cured at minimal cost.

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Contact InformationContact Information

Web site: www.copper.orgdavid.brender@copperalliance.us

212-251-7206 office917-297-5738 cell