telecommunications lt1302

8/9/2019 Telecommunications LT1302

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Grounding,Lightning Protectionand Surge Protection

For Telecommunications


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Indoor Bonding Layout

ERITECH ground bars can be used to achieve the ideal indoorgrounding arrangement as required at the telecommunicationsfacility.

LEGEND

Main Ground BarBonding Terminal or Isolated SparkGap (optional)Telecommunications Ground ElectrodeAC Ground ElectrodeCommunications Ground BarBattery Ground

Grounding/earthing, lightning protection and surge protectionare critical parts of a telecommunications facility installation.ERICO® has complete telecommunications applications solutionsto help protect the facility against electrical noise, lightninginduced surges and transients caused by switching componentsin the power systems.

ERICO solutions include ERITECH®

ground rods, ground mats,ground enhancing material (GEM), ground bars, CADWELD®

connections, ERITECH lightning protection systems and CRITEC®

MDF, co-axial and power surge protectors.

To make the application of these products simpler, thegrounding, lightning protection and surge protection systemat a telecommunications facility is divided into 5 components.

1. Indoor Bonding Arrangement2. Outdoor Grounding Arrangement3. Surge Protection for Power Lines4. Surge Protection for Telephone Lines5. Direct Strike Lightning Protection

A

AB

CDEF

B

D

C

E

F

Surge Protection


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Outdoor Grounding / Earthing Layout

LEGEND

Telecommunication ground electrode systemVertical ground electrodesTower groundCoaxial and Waveguide feedersCoaxial surge protectors or ground kitRF Ground Bar

The outdoor arrangement of a grounding system at atelecommunications facility is depicted here. This arrangement isnot always possible due to certain constraints at the site. Wherethe telecommunication equipment is installed in a large multifunctional building or several floors above the ground floor thislayout may not be possible.

Alternative outdoor ground electrode system needs to beconsidered on a case by case basis if the suggested layoutbelow is not possible to implement.

ERICO® offers a full range of products to form the outdoorgrounding system at a telecommunications facility.

ABCDEF

A

B

D

C

E

F

E


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ERITECH® Ground Rods, Connections and Accessories

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ERITECH® Ground RodsERICO® offers a range of ground rods for telecommunicationsapplications to suit the needs and preferences of the carriers. The mostcommon of these are copper bonded steel ground rods, due to theirversatility in varied soil conditions and compatibility with various commonmetals used underground.The copper-bonded ground rod has an electrolytic coating of copper

deposited over a layer of nickel. This process helps ensure a long lasting,molecular bond between the copper layer and the steel core. ERICOrecommends copper-bonded ground rods because the copper coatingwill not slip or tear when driven, nor will it crack if the rod is bent. Thetough, carbon steel core has good characteristics for deep driving.Copper-bonded ground rods have a high resistance to corrosion andprovide a low resistance path to ground.It is important to note that certain soils and landfill areas may not becompatible with copper. In these situations, stainless steel is a betterchoice. Stainless steel may also be an alternative, when structures orcomponents, such as steel towers, poles or lead sheathed cables are inclose proximity to an array of ground electrodes. In these circumstances,consideration must be given to the consequence of galvanic corrosion.

Grounding ConnectionsGrounding connections are vital to the proper operation and integrityof the electrical system. ERICO offers a range of mechanical groundingconnections including clamps, jumpers, fence connections, U-Bolts andother clamps.

However, the CADWELD® welded electrical connection is ourrecommended method of making grounding connections. The principletechnology consists of bringing together a welding material and ignitionagent in a suitable graphite mold. The reduction of copper oxide byaluminum produces molten copper and aluminum oxide slag at extreme-ly high temperatures. The shape of the mold, its dimensions, and the sizeof welding material, are all dependent on the items to be welded.

The CADWELD connection is essentially a fusing through of thegrounding conductor, whereby there is greater amount of metal acrossthe cross section of the connection than that across the conductor. It canbe intuitively seen that the connection is as good as the conductor, if notbetter, which is a unique feature of CADWELD. Independent scientifictests have been done to CADWELD using the most stringent standardsassociated with high voltage electrical installations.

Grounding Conductors and AccessoriesThe two most common grounding conductors used in telecommunica-tions are round cables or flat tape. Flat tape conductors have a lowerinductance and provide a higher capacitive coupling to the ground,which results in a lower impedance earth system, especially at highfrequencies associated with lightning and telecommunications noise.ERICO offers a range of conductors including bare or tinned copper tape,bare copper cables and smooth weave cable conductors.In situations where ground conditions make it difficult to achieve therequired resistance, ERICO offers Ground Enhancement Material (GEM).GEM is a low-resistance, non-corrosive, carbon dust based material thatimproves grounding effectiveness, especially in areas of poor conductivi-ty. GEM contains cement, which hardens when set to provide a perma-nent, maintenance-free, low-resistant grounding system that will notleach or wash away.ERICO also provides a range of coaxial surge protectors that are suitablefor use up to a frequency of 3 GHz. It is strongly recommended thatfeeders not fitted with coaxial surge protectors be grounded viaappropriate grounding kits.The ERITECH EST series of earth testers are available for testing of soilresistivity and ground resistance of electrodes.

The key benefits of CADWELD are:• Connections are permanent and will not loosen or corrode.• Connections are made with inexpensive, lightweight equipment.• Connections can be made without the need for any special skills.

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Typical CADWELD Connections used in telecommunicationsgrounding and bonding

TA

BM

Ground Bar

Ground Clamp

Ground Clamp Earth Tester

LJ GL

GY

VS

PT

LQ


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Surge Protection for Power and Telephone Lines

The SPD arrangement shown left is called shunt surge protection whereby the SPD connected in parallel with the load. The limitation of this type of protection is that wthe surge voltage is controlled to a manageable level, these devices do not lower thevoltage rise time of the incoming surges. It is widely acknowledged that both the volevel as well as the rise time of power surges can cause damage to sensitive electronIn applications where a higher level of protection is deemed necessary due to the crnature of the telecommunications network element, surge reduction filters can be useffectively reduce the voltage levels and rise times.

Surge Protection for Telephone Lines

Lightning surges can get coupled into telephone lines, in a verysimilar manner that they couple into power lines.

A single stage gas arrestor installed at the main distribution frame helpsensure that both of the lines are shorted to ground momentarily to takebulk of the energy down to ground when a surge occurs. However, becait is not possible to short out the two lines at exactly the same moment, differential mode transient develops which is very damaging to the endequipment. Hence in critical applications, the use of single stage gas arrmodules at main distribution frame is not adequate. Surge protective dewith secondary clamping stages provide a better protection.

Topologies for Telephone Line Protection

Mains Supply

CB or Fuse

SPD SPD

Neutral

Ground

VariousLoads

Typical Wiring of a SPD at a Main Switch Board

A telecommunications site needs reliable grounding for the purpose ofgood reference ground, noise control and dissipation of any lightningenergy. Surges in the power and copper based telephone lines can alsooriginate from lightning strikes that have struck objects some distancefrom the actual site, in many cases, even miles away. Having a goodground alone is not enough to minimize damage due to these surgescaused by distant strikes. Surges can also occur in power lines due toswitching of circuit breakers in the power systems under fault conditions.It is important to have adequate surge protection on the AC mains andon telephone lines.

The best starting point in the selection of surge protection devices is tolook at the following 5 ratings as defined by IEC® standards and choosesuitable levels for the application.

• Maximum Discharge Current, or Imax. This is the single shot ratinof the SPD.

• Nominal Discharge Current or In. This is the 15 shot rating of the S

• Voltage Protection Level, or Up. This is the voltage to which surgetested to IEC standards are limited to. Normally this test is done at Sometimes this test is done at 3kA 8/20us. The lower the Up thebetter the SPD is as a protection device.

• Maximum Continuous Operating Voltage, or Uc. SPD’s can experidamage if the supply voltage exceeds their clamp voltage for aprolonged duration. A high Uc will mean that the product is ruggeagainst over-voltage events.


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Lightning Protection for Telecommunications Towers

OR

OR OR

ERITECH®DYNASPHERE

ERITECH®

ERICOREISODC* Conventional Cable

Smoothweave

Conventional /ISODC*

Direct lightning strikes to telecommunications towers are areasonably regular occurrence, more so on mountain topsand in certain parts of the world. The traditional approachto lightning protection on towers is to have a lightning rodon the top of the tower and a dedicated down conductorcomprised of bare cable or tape that is installed on thetower to connect the lightning rod to the ground.

A modern method is to use an optimal air terminal design,the ERITECH® DYNASPHERE mounted on top of thetelecommunications mast on a 3-4 metres long fibreglassreinforced pole, FRP. The FRP provides isolation between theair terminal and the tower and helps ensure that the

lightning does not flash over and electrify the mast or theantenna. A special purpose downconductor, called theERITECH® ERICORE is routed in the core of the FRP andconnects to the bottom of the ERITECH® DYNASPHERE viaa high voltage, impulse rated termination. The ERITECH®ERICORE runs along a leg of the tower away from the routesof feeders, down to the tower grounding system. ERITECH®

ERICORE cable is designed to minimize the voltage betweenitself and the tower so that the bulk of the lightning energyis contained within the cable, thereby protecting the towerand feeders from conducted lightning currents and havingmuch less reliance on bonding practices which sometimesare overlooked or completed incorrectly.

* ISODC - is an isolated lightning protection cable system based around IEC62305. It is designed to isolate the lightning current fromsensitive equipment, eliminating the need for separation distances required with conventional cable. Contact ERICO® for further information.


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E656B-WWEN E190LT07WWEN 0082Copyright ©2007 ERICO International Corporation. All rights reserved.CADDY, CADWELD, CRITEC, ERICO, ERIFLEX, ERITECH, and LENTON are registered trademarks of ERICO International Corporation.

IEC is a registered service mark of Independent Electrical Contractors, Inc.

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