good earthing all

INSULATORSMORLYNN

Energy Division

Electronics

A

GuidePractical

TO

GoodEARTHING

Section 1 -The Basics of Earthing

What is “Earthing”?

Purpose of Earthing

Chief requirementof good Earthing islow soil resistivity

The Earth Path

Principal factorsaffecting soilresistivity

2

Earthing may be described as a system of electrical connections to the general mass of earth.The characteristic primarily determining the effectiveness of an earth electrode is theresistance which it provides between the earthing system and the general mass of earth.

The earthing of an electrical installation has two purposes -1. To provide protection for persons or animals against the danger of electric shock.2. To maintain the proper function of the electrical system.

Soil resistivity (specific resistance of the soil) is usually measured in Ohm metres, one Ohmmetre being the resistivity the soil has when it has a resistance of one Ohm between theopposite faces of a cube of soil having one metre sides.

The other unit commonly used is the Ohm centimetre. To convert Ohm metres to Ohmcentimetres, multiply by 100.

Soil resistivity varies greatly from one location to another. For example, soil around the banksof a river have a resistivity in the order of 1.5 Ohm metres. In the other extreme, dry sand inelevated areas can have values as high as 10,000 Ohm metres.

The resistance of the earth path is determined -1. by the resistivity of the soil surrounding the earth rod,2. by its contact resistance between the earth rod and the surrounding soil, and3. by the resistance of the earth rod and connecting conductors.

When an electrical current passes into the soil from a buried earth rod, it passes from a lowresistance metal into an immediate area of high resistance soil.

Reference to Figures 1 and 2 depict what happens when a current flows from an earth rod intothe surrounding earth. The areas of resistance can be described as being that of a number ofsheaths of ever increasing diameters.

The current path passes into the first sheath immediately adjacent to the earth rod and theninto the second sheath which is of a larger cross-section with a greater area for current flow,and therefore, of lower resistance than the first sheath. And so on into a succession of sheathsor shells of ever increasing area, and because of this, of ever decreasing resistance.

Eventually at a distance of three or four metres, the area of current dissipation becomes solarge, and the current density so small, the resistance at this point is negligible. Measurementsshow that 90% of the total resistance around an earth rod is within a radius of three metres.

However, it is this resistance at the interface where the current leaves the earth rod and flowsinto the main body of the earth that is important and explains why soil resistivity tests are verynecessary in order to secure lowest overall resistance.

Factors chiefly affecting soil resistivity are -

1. TType oof ssoilSoil composition can be - clay, gravel, loam, rock, sand, shale, silt, stones, etc. In manylocations soil can be quite homogenous, while other locations may be mixtures of these soiltypes in varying proportions. Very often soil composition is in layers or strata, and it is theresistance of the varying strata, especially at sub-soil level and lower where the moisturecontent is not subject to drying out, that is important in securing a good electrical earth. ReferTable 1 for typical soil resistivity values.

2. CClimateObviously arid and good rainfall climates are at opposite extremes for conditions of soilresistivity.

3. SSeasonal cconditionsThe effects of heat, moisture, drought and frost can introduce wide variations in “normal” soilresistivity. Soil resistivity usually decreases with depth, and an increase of only a few percentof moisture content in a normally dry soil will markedly decrease soil resistivity. Conversely,soil temperatures below freezing greatly increase soil resistivity, requiring earth rods to be dri-ven to even greater depths. See Table 2 for variations of soil resistivity with moisture content,and Table 3 for variations of soil resistivity with temperature.

4. OOther ffactorsOther soil properties conducive to low resistivity are chemical composition, soil ionisation,grain distribution and homogeneous grain size. All have much to do with retention of soilmoisture, as well as providing good conditions for a closely packed soil in good contact withthe earth rod.

In view of all the above factors, there is a large variation of soil resistivity between different soiltypes and moisture contents.

Fig. 1

Fig. 2

Potential (P)Probe

Current (C)Probe

Depth300 to500mm

Earth rodunder test

Earth testerC1 P1 P2 C2

Soil

Fig. 3

Depth‘a’20

Test rods

Earth testerC1 P1 P2 C2

Soil

Fig. 4

‘a’ ‘a’ ‘a’centre

3

A Practical Guide to Good Earthing

Every earth is an individual and the only way to know that an earthing installation meets coderequirements is to carry out proper resistance measurements on site.

There are a variety of test instruments available. However, they can be generally categorisedas three-terminal or four-terminal test instruments.

1. MMeasuring rresistanceFigure 3 illustrates the test setup for measuring the resistance in Ohms between the installedearth rod and the general mass of earth. Refer to the instrument manufacturer’s manual onhow to carry out the test. As a general rule, the distance between the earth rod under test andthe current probe “C” is not less than 15 metres.

2. MMeasuring ssoil rresistivity

Figure 4 illustrates the simple test setup for measuring soil resistivity. The test results give aresistivity profile of the earth beneath the surface.

A four-terminal instrument is required for soil resistivity. The probes are installed in a straightline with an equal spacing of “a” metres and inserted to a depth of no more than a/20 metres,i.e. for spacing of 2 metres, depth must be less than 100mm. Now, keeping the centre posi-tion the same, resistance measurements are taken at increasing spacings (e.g. a = 2m, 3m,4m, etc). Always ensure that the spacing between individual test probes are identical.

The soil resistivity can be obtained from the following formula:

ρ = 2π a R (Ohm metres)where ρ = apparent soil resistivity

a = spacing of probes in metresR = resistance value in Ohms (as indicated on the tester)

The use of the resistivity at probe spacing “a” metres as the average resistivity to a depth of“a” metes is a good enough approximation for most circumstances.

From the calculation, a soil resistivity versus depth profile can be drawn as shown in Figures5 and 6. The profile can be used to identify where low resistivity soil occurs so that appropri-ate installation techniques can be used. As the soil resistivity decreases with depth, deepdriving earth rods are recommended.

If the soil resistivity increases with depth, earth rods should be installed in parallel to obtain alower resistance reading. Best results are achieved when the spacing of the parallel earth rodsis greater than their depth.

Table 11Resistivity VValues ffor SSeveral TTypes oof SSoils aand WWater

Type oof SSoil oor WWater Typical RResistivity ΩΩm Usual LLimit ΩΩm

Sea WaterClayGround well and spring waterClay and sand mixturesShale, slates, sandstones, etcPeat, loam and mudLake and brook waterSandMorane gravelRidge gravelSolid graniteIce

24050

100120150250

2,0003,000

15,00025,000

100,000

0.1 to 108 to 70

10 to 1504 to 300

10 to 1,0005 to 250

100 to 400200 to 3,00040 to 10,000

3,000 to 30,00010,000 to 50,000

10,000 to 100,000

Table 22Variations oof SSoil RResistivity wwith MMoisture CContent

Moisture CContent% oof WWeight

Typical VValue oof RResistivity ΩΩmClay mmixed wwith ssand SSand

02.5

510152030

10,000,0001,500

4301851056342

---3,000,000

50,0002,100

630290

---

Table 33Variation oof RResistivity wwith TTemperaturein aa MMix oof SSand aand CClay wwith aa MMoisture

Content oof aabout 115% bby WWeight

TemperatureoC

Typical VValue oof RResistivityΩΩm

2010

0 (Water)o (Ice)

-5-15

7299

138300790

3,300

Site Testing Essential

Lower layermore conductive

Middle layer lessconductiveLower layer moreconductive

Spacing (m)(Depth)

Spacing (m)(Depth)

App

aren

t soi

l res

istiv

ity(O

hm/m

)A

ppar

ent s

oil r

esis

tivity

(Ohm

/m)

Fig. 5Typical curve of apparent soil resistivity for 2 layer soils

Fig. 6Typical curve of apparent soil resistivity for 3 layer soils

250mm

Section 2 -About Earth Rods

Types of Earth Rods

Steel core EarthRods have the bestattributes

Extendable Earth RodCoupling Systems

Earth Rod lengthmore importantthan Rod diameter

4

At one time or another, all manner of conductor materials and shapes have been installed inthe ground to provide an electrical earth. These materials range from cast iron plates, tubes,galvanised steel stakes, copper strip, metallic rod, wire and water pipe.

Taking into account conductivity, high resistance to atmospheric corrosion and soil attack,ease and economy of installation and overall reliability, the steel rod clad with either copper orstainless steel has proven its superiority over all others.

The clad steel rod is simple to install, its connection to the earthing system is easily made, andthe installation is readily accessible for inspection and test.

Additionally, with the use of deep driving techniques, extendable earth rods have beendeveloped to reach underlying strata of low permanent resistivity unaffected byseasonal drying.

Electrically, a good earth rod should have a low intrinsic resistance and be of sufficient sectionto carry high currents without damage when called upon.

Mechanically, its physical properties should exhibit strength, have a rigid core for easy drivingand be of durable, corrosion resistant material.

Dulmison has had wide experience in the design and production of a variety of copper andstainless steel clad earth rods for domestic, industrial and substation applications. The rangeincludes the specially designed extendable earth rods which may be joined end to end to reachinto the deeper levels of moist soil.

A key feature of Dulmison’s extendable earth rods is the low profile of the couplings. While theflush (pin and sleeve) coupling has proven itself with years of reliable service, the current trendis to a tapered coupling. This single piece taper coupling is quick and easy to fit to the earthrod. Both the flush and taper coupling designs provide excellent electrical connection asproven in laboratory testing and experience in service.

The elimination of coupling “bulges” enables close soil contact throughout the entire length ofthe electrode. This is an important consideration in dry/arid countries (such as Australia),where it may take some time for the soil to close back about the electrode. Close soil contactwill allow true earth resistance readings and may eliminate the need to drive deeper in orderto obtain the desired result.

Apart from considerations of mechanical strength, there is little advantage to be gained fromincreasing the earth rod diameter with the object in mind of increasing surface area in contactwith the soil.

The usual practice is to select a diameter of earth rod which will have enough strength toenable it to be driven into the particular soil conditions without bending or splitting. Largediameter rods may be more difficult to drive than smaller diameter rods.

The depth to which an earth rod is driven has much more influence on its electrical resistancecharacteristics than has its diameter. This is because it is not the actual area of contact withthe soil that counts, so much as the total resistance area of the sheath or shell surrounding theearth rod. (Refer paragraph “The Earth Path”.)

The resistance of an earthing installation by an earth rod is calculated according to thefollowing formula:

R =

Where R = resistance of earth rod in Ohmsρ = soil resistivity in Ohm metresL = length of earth rod in metresd = diameter of earth rod in metres

The curve shown in Fig. 8 is based upon this formula where the earth resistance using a 25mmdiameter earth rod is plotted against its length for soil having a resistivity of 10 Ohm metres.

Note that if the diameter of the earth rod is halved (or doubled), the resistance is changed bysome 121/2%. By comparison, it can be seen from the curve, a much more dramatic effect isobtained by increasing the length of the earth rod.

Fig. 7

Fig. 8

ρ ( ln ( 8L ) - 1 ) Ohms

2πL d

0 1.5 3.0 4.5 6.0

5

Res

ista

nce

in O

hms

510mm

50

0m

m

250mm

510mm

10

00

mm

250mm

520mm

50

0m

m

Shell area ‘A’

1.21 m2

Shell area ‘B’

1.24 m2

2.5% increase

Shell area ‘C’

2.01 m2

66% increase

10

15

20

Length of electrode in metres

5


The combined resistance of parallel rods is a complex function of the number of rods, roddiameter, rod length, rod separation, configuration of earth rods and soil resistivity. In mostcases, fewer rods coupled together for deep driving will achieve a lower resistance than thesame number in parallel. The earth rod spacing should not be less than the earth rod lengthto avoid overlap of resistance areas.

This is because multiple earth rods, unless spaced well apart, do not follow the law of resis-tance in parallel as their earth conducting paths overlap - see explanation under “Earth Path”.

Accordingly, the installation of multiple earth rods at sufficient distances apart takes up a largearea, involves long cabling and many connections, all adding up to higher costs in time, labourand equipment.

The permanence of copper in most soils, its resistance to chemical attack and corrosion, andits inherent low resistance, brings it into widespread use throughout the electrical industry inAustralia and around the world.

However, there are certain soils where it is inadvisable to use copper, such as in tidal lands,salt marshes, swamps and land filled with ashes, coke breeze and like materials.

Dulmison stainless steel earth rods have a high resistance to both atmospheric and soilcorrosion, being clad with an austenitic grade stainless steel having a chromium content ofapproximately 17%.

Typical of the applications where Dulmison stainless steel clad earth rods are favoured overcopper clad are -

1. Where the chemical composition of the soil reacts more unfavourably than copper - as perconditions described above.

2. Where the earthed item needs to be protected against galvanic attack and corrosion, e.g.lead sheathed cables, steel poles, etc.

3. Where the tougher sheathing of stainless steel will provide for a more durable and rigidearth rod better suited to hard driving conditions than its copper counterpart. Moreover,the cladding operation imparts an extra toughness to the stainless steel through workhardening.

A Dulmison copper clad earth rod which had been installed on the shores of Botany Bay atSans Souci, near Sydney, NSW for 10 years, was submitted to Metal Manufacturers Limited,Port Kembla, NSW, for examination.

The report read in part: “As you can see, there has not been any detectable corrosion of thecopper sheathing.”

The cross section, reproduced here at 4x magnification shows no circumferential irregularitiesindicating sheath corrosion. Etching and examination at 100x magnification confirmed this.

Cross section of copper sheathed Dulmison earth rod described above,at 4x magnification after 10 years in salt-laden soil.

Earth Rod lengthmore important than

number of rodsin parallel

Coppervs

Stainless Steel

Test showsno “detectable corrosion”

(after 10 yearsin salty soil)

Section 3 -Everything for Earthing

6

Earth Rods - General

Dulmison earth rods have a structural steel core with anouter cladding of either electrolytic pure copper oraustenitic stainless steel. This type of constructionprovides the rods with high mechanical strength for drivingand good resistance to corrosion.

Dulmison Earth Rods

• are Energy Authority approved around Australia andthe South Pacific

• are tested to 5kA fault current - 9kA peak with noappreciable effect to the rod itself

• have bonded-for-life cladding

• have consistent OD throughout length ensuring fit ofearth clips comply with AS1882

• can be formed around footings without damage tocladding or core

• are 100% Australian made - labour and materials

All Dulmison couplings are made from stable materialscompatible with the earth rod core and sheath. They arenot prone to de-alloying or stress corrosion which canadversely affect earthing fittings that have been made frominferior materials such as brass. In fact, the EarthingHandbook expressly forbids the use of brass in buried sit-uations. This design philosophy has been carried over intoDulmison’s range of earthing connectors.

Non Extendable Earth Rods

Dulmison manufacture a broad range of non extendableearth rods. Each rod incorporates an integral driving point,machined (not ground) to preserve the strength andrigidity of cold drawn steel. The flat tip was developed forpenetrating all types of soil.

CNE SSeries CCopper CClad RRodsRod Diameter

1440180018002400

CNE1314CNE1318CNE1518CNE1524

10/5005/5005/5005/500

Cat. Numbers Pack/Bulk Qty

Domestic RRod PPack - CCNE1314T

10 pcs/pk10 pcs/pk

CNE1314EC13D

Domestic earth rodEarth clip

Domestic earth rod clip EC13D. Suitablefor cables in the range 6 - 16mm2

Certificate of Suitability CS571N

Rod Length

13131515

SNE SSeries SStainless SSteel CClad RRodsRod Diameter

14401800

SNE1314SNE1318

10/5005/500

Cat. Numbers Pack/Bulk QtyRod Length1313

Consult office for additional information &/or sizes

Commercial/Industrial LLGR SSeries 119mm CCopper CClad RRods

18002400300036004500

LGR1918LGR1924LGR1930LGR1936LGR1945

1/201/201/201/201/20

Catalogue Number Pack/Bulk QtyRod Length

Extendable Earth Rods

Taperlock Coupled - Types CTE and STE

The simplest of all extendable earth rods to install is thetaperlock earth rod. Available in either copper or stainlesssteel clad rod, there are a variety of sizes to meet allsituations.

The extremities of the rod terminate in identical tapers.

The coupling is a single piece with taper matching that ofthe rod. A single blow is all that is required to lock the rodand coupling together. This is ideally suited to light sandysoil conditions where there is little driving resistance fromthe soil.

Taperlock coupled earth rods present slim profile (lessthan 1mm deviation) to ensure minimal soildisplacement.

CTE SSeries CCopper CClad RRods

RodLength

CTE1512CTE1514CTE1518

- - -CTE1524CTE1530

- - -- - -- - -

CTE1920- - -- - -

15mm Dia. 19mm Dia.13mm Dia. Pack/Bulk Qty

Pack/Bulk Qty

Pack/Bulk Qty

120014401800200024003000

CTE1312CTE1314CTE1318

- - -CTE1324CTE1330

10/50010/5005/500

- - -5/5001/50

10/50010/5005/500

- - -5/5001/40

- - -- - -- - -

1/20- - -- - -

Earth RRod AAccessories

CouplingPoint

Star Point

CCT15DPT15

SDP15T

CCT19DPT19

- - -

CCT13DPT13

SDP13T

10/10050/20010/100

10/10050/20010/100

10/5010/50

- - -

Driving AAccessories

HandKango 950A/C Tex 11A/C Cobra

DHT15MDH15KMDH15A

MDH15AC

5/25EachEachEach

5/25- - -- - -- - -

DHT19- - -- - -- - -

STE SSeries SStainless SSteel CClad RRods

RodLength

STE1412STE1415STE1418STE1424STE1430

14mm Dia.13mm Dia. Pack/Bulk Qty

Pack/Bulk Qty

12001440180024003000

STE1312STE1314STE1318STE1324STE1330

10/50010/5005/5005/5001/50

10/50010/5005/5005/5001/40


CouplingPoint

Star Point

SCT15DPT15

SDP15T

10/10050/20010/100

SCT13DPT12

SDP12T

10/10050/20010/100


HandKango 950A/C Tex 11A/C Cobra

DHT15MDH15KMDH15A

MDH15AC

5/25EachEachEach

TypeCNE

TypeLGR

7


Features: Stable, high conductivity providing long termlow ground resistance. High expansion,low shrink characteristics. Non-toxic, non-corrosive.

Packaging: 20kg non-tear, plastic lined bags.

Installation: Apply as a dry mix or pourable slurry.

Dry mix will yield a volume of approximately0.0176m3 (roughly 57 bags to the cubicmetre).

Slurry will yield a vol-ume of approximately0.030m3 when mixedwith 20 to 25 litresof water (roughly33 bags to thecubic metre)

Extendable Earth Rods

Flush Jointed - Type CCE

This flush jointed, copper clad earth rod series is availablein a variety of lengths to 3000mm, with either 13mm or15mm nominal diameter. The ends of the rod are identical,having a reduced section with precision drilled hole.

Coupling is via a two piece arrangement comprisingcopper sleeve and hardened steel pin. The whole couplingmechanism finishes flush with the main body of the rod.Effective contact is established along the entire length ofthe driven electrode from day one. This can mean areduction in the number of rods required to achieve aspecific resistance value.

Expansion Jointed - Type SDE (Telstra)

Telstra designed and approved earth rod featuringcorrosion resistant stainless steel clad rods, extendablein 1440mm lengths.

The coupling system comprises of a stainless steel sleeveand hardened steel pin having a raised convolution at themidpoint. A secure and non-detachable joint is achieved bymeans of the pin’s convolute expanding and deforming theends of the rod into the coupling sleeve as the rods aredriven together.

Connection Boxes

These enclosures provide a tidy means of protecting theconnection of the main earth conductor to the earth rod.Manufactured from high strength aluminium alloy orpolymer concrete, they are well suited to use in high trafficareas. Hinged covers allow easy access for inspection ortesting.

76

120120

127127

165

165

240

200

200

Cat. No. ERB1Aluminium alloy casting

Cat. No. ERB3Polymer concrete

CCE SSeries CCopper CClad RRods

RodLength

CCE1312CCE1314CCE1318CCE1324CCE1330

CCE1512CCE1514CCE1518CCE1524CCE1530

10/50010/5005/5005/5001/40

10/50010/5005/5005/5001/50

15mmDia.

Pack/Bulk Qty

Pack/Bulk Qty

13mmDia.

12001440180024003000


CouplingPoint

Star Point

CCA15DP15

SDP15

25/10050/20010/100

10/10025/20010/100

CCA13DP13

SDP13


HandKango 950A/C Tex 11A/C CobraDrive Pin

DH15MDH15DFMDH15AFMDH15CMDP10M

5/30EachEachEach100

SDE SSeries SStainless SSteel CClad RRodsRod Length

SDE1414L 10/500Pack/Bulk Qty14mm Dia. Pin Lock

1440

Earth RRod AAccessoriesCoupling

PointStar Point

C14LDP14

SDP14D

25/7550/20010/100


HandCoupling Tool

DH14CT14

5/305/25

Earthing Enhancement Compounds

Cat. NNo.

Conforms toAS2239

N/A

Conforms toAS2239

Bentonite, Gypsum, Sodium Sulphate

Bentonite, Gypsum, Sodium Sulphate

Calcium, Bentonite, Natural Gypsum

StandardComposition

EARTHFIL

EARTHRITEEARTH5050


8

Earth Rod ClampsSingle Conductor - Parallel

Simple and robust, these pinch and U Bolt type clampshave a vee groove embodied in the casting to accommo-date the earthing cable.Material: Copper alloy casting, bronze set screw or

stainless steel U-bolt and nuts.

Earth MatsEarth mats and installation kits

Single Conductor - Versatile

These clamps are designed for either parallel or rightangle connections, as illustrated.Material: High copper content alloy castings with

stainless steel U-bolt, spring washers and nuts.

Multiple Conductor Installationsfor multi-conductor earthing

For 2 earth conductors parallel to rod or 2 or 3 earth con-ductors at right angles to rod.Material: High copper content alloy castings with

stainless steel U-bolt, spring washers and nuts.

Earthing BondFor commercial earthing installations C70

The Earthing Bond system provides an earth connectionwelded to the steel reinforcement, thus offering a virtuallyindestructible, stable and low resistance path to earth.

Specification Cat. NNo. CC70

Mains cableBonding cable

3 sec current ratingLug diameter

Terminal threadThread depth

50 - 630mm2

70mm2

10kA10mmM10

20mm

Cat NNo.

GRC5CLAMP210

EP1

13 - 1513 - 1517 - 19

10010/50

40

10 - 3516 - 12016 - 120

4.05 - 7.655.10 - 14.215.10 - 14.21

Rod DDia.mm

PackQty

Conductor SSizecsa mmm2 Diameter mmm

Type GRC5 Clamp 210

Type EP Type ET

Cat NNo.PackQty

GB1GB2GB3

EL21090

25201010

13 - 1913 - 1913 - 1912 - 15

16 - 3550 - 120

150 - 18535 - 120

5.1 - 7.78.9 - 14.2

15.7 - 17.67.6 - 14.2

Rod DDia.mm

Conductor SSizecsa mmm2 Diameter mmm

CatNo.

PackQty

EP3EP4ET1ET2ET4

2020251510

13 - 1913 - 1913 - 1913 - 1913 - 19

16 - 3550 - 12016 - 35

50 - 12050 - 120

5.1 - 7.78.9 - 14.25.1 - 7.7

8.9 - 14.28.9 - 14.2

22223

11223

RodDia. mmm

Conductor SSizeDia. mmm

No. oofConductors

FigNo.csa mmm2

Fig. 1 Fig. 2 Fig. 3

Kit

Earthmat

Cat. NNo.

EARTHMAT

KITY

Material: Galvanised mild steelSize: 1500mm x 900mmMesh: 76mmx 50mmInstallation kit for type RDB rotaryswitches with earth switch.

Description

9


CatalogueNo.

PackQty Open SSection

Tap ooff CConductorDia. mmm

CEC15000CEC15035CEC15070CEC15120

50404050

Conductors50 - 120mm2

or Earthrods13 - 15mm dia.

Blank8.4

11.015.0

Blank25 - 4050 - 70

95 - 120

DU1315

Crosssection

mm2

DieSet

CatalogueNo.

PackQty

ConductorCombination

mm2

CEC050

CEC070

CEC095

50

50

50

DUOT

DUOT

DU1315

70 - 3570 - 5050 - 5050 - 5070 - 5070 - 7070 - 9595 - 95

DieSet

CEC Connectors

A heavy duty compression connector for earth rods and conductors

Dulmison CEC connectors were specifically developed to dissipate surges of high fault currentquickly and effectively to limit any potential damage to equipment, and to safeguardpersonnel close to that equipment.

Manufactured from pure wrought copper, the CEC connector is fitted by use of standardcompression tools to form a dependable, tamper-proof joint from conductor to earth rod orburied earthing cable.

Features and benefits

• Simple installation - One crimp from a standard compression tool• Range taking - From 35mm2 to 120mm2 (13 to 15mm diameter earth rods)• Connector design - Current carrying capacity greater than that of the conductor• Corrosion resistant - Identical material to the conductor eliminates problems caused by

electrolytic corrosion and the corrosive effects to some soil.• Pre-coated with Coppalube - A specially formulated jointing compound heavily laden

with copper particles, to increase the mechanical and electrical integrity of the connection,exclude moisture and resist rotation of the connector on the earth rod.

• All weather application - This connector may be installed in damp or fire risk areas withno adverse effects on the joint or the environment.

• Easy identification - Each CEC connector is clearly stamped with the appropriatecatalogue number, conductor size and installation die reference.

• Individually packed - For cleanliness and ease of handling.

Installation notes

• Standard “C” head compression tool of minimum 12 tonne capacity recommended• Full compressive force of the tool is utilised as application is not limited by die halves

meeting, but the pressure release valve in the tool• Regular use of a load test cell to confirm compression performance of the tool is

recommended.

Application to Earthing Grid Systems

By joining two Compress-On connectors - either of the same or ofdifferent catalogue numbers - by means of length of bare strandedcopper cable, a number of various combinations of conductor sizes and gridconnections arrangements are readily accommodated, and more to thepoint, are quickly and economically made.

Consult office for additional information and/or sizes


The Cadweld Connection

Airport Earthing Terminal

Survey and MappingDatum Marks

10

The “Forever Connection” for -

• Electrical systems earthing• The earthing of heavy duty industrial equipment• The cathodic protection of plant and installations• Busbar connections• Electric transport and communication systems

Simple, portable and extremely fast, Cadweld is ideal for on-site welding of connections to awide range of metals as follows -

Copper to -

About the Cadweld Connection

A Cadweld connection is a true fusion, or molecular weld of virtually pure copper. Although thetemperatures reached to effect this weld are extremely high, the process itself is so fast(a matter of seconds) the total amount of heat applied to the connection surfaces isconsiderably less than that of a comparable brazing or soldering operation.

Thus it is that insulated cables and thin walled tube may be Cadwelded without detriment toadjacent insulation or tube wall strength.

The Cadweld connection provides for -

1. A connection with a cross sectional area that is in most cases, twice that of the connectedconductors

2. A connection with a high current carrying capacity equal to or greater than, that of theconnected conductors.

3. A connection not affected by high current surges. On short circuit tests the conductorsmelt before the Cadweld connection.

4. A connection without contact pressures to loosen or corrode - the Furseweld connection isan integral part of the conductor system.

Illustrated here are just a few of the many uses for Cadweld applicable to earthing. Consultoffice for technical information.

For static electricity earthing - Cat. No. AET1918

Standard length: 1800mm, other lengths to special order Pack Qty: 15

Type AET electrodes provide for the earthing of airport tarmac areas where anygeneration of static electricity could be hazardous, i.e. aircraft refuelling, servicingand cargo loading areas. The heavy duty capping has a ribbed design affording afast and positive earthing connection by means of earth lead connector clips.

Material: Solid steel core overlaid with copper cladding; heavy bronze cap.

Installation procedure: Drive electrode into ground to required depth. Removeprotruding portion of rod above cap and finish flush.

Also available, new release flush fitted static terminal Cat. No. AET1918F

Mild steelStainless steelCopper clad steelGalvanized steel

CopperBronzeBrassMonel metal

Cadweld Connections -

• Are self contained• Require no arc welding equipment• Require no gas cylinders• Require no external power source

SDE Series 14mm rods

• Stainless steel for permanence

• Extendable for deep driving

• Manual or machine driven

• Special stainless steel ‘drive fit’ protective capCat. No. F20634 secures datum permanence

• Consult office for further details

11

Earth rods are installed by one of two methods. More often than not, the rod can be driven intothe ground by either a hand held hammer or mechanically operated hammer. However, wheredriving is difficult or progress non-existent, the only option is to drill a hole to take theearth rod.

Where holes are drilled, the gap between the earth rod and wall of the drilled hole is commonlyfilled with a water expanding compound. Such a compound is EARTHRITE. This is a mixtureof Bentonite and Gypsum with a small amount of Sodium Sulphate to reduce the resistivity ofthe backfill.

Earth rods up to 3m long can be driven satisfactorily in one length. Where rods have to belonger than 3m, it is preferable to use one of the Dulmison extendable series earth rods.

There are a variety of methods for driving earth rods into the ground from the simple hand heldhammer to power operated mobile rigs. Their use is dictated by the nature of the soil and ter-rain, the length of drive needed to secure minimum resistance, and the number of rods to bedriven. The driving methods are -

The Hand Held Hammer is an effective method for most domestic installations encounteredin suburban lots. The earth rod should be driven lightly using a hammer of around 11/2 to 3 kgs,keeping the force of the blows axial to the rod to obviate the risk of whipping.

A large number of comparatively light hammer blows are more effective, and preferable, toheavy blows which are destructive to the metal and can cause deformation to the rod end aswell as bending and possible splitting. The fitting of a guide to the rod will assist rigidity andreduce whipping when the rod comes up against resistance to penetration.

The Mechanical Hammer, which can be one of three types: a. Electricb. Pneumaticc. Petrol engine driven

These power operated aids are used when soil conditions are not suited to hand driving andwhen long earth rods have to driven to great depths.

A range of machine driving heads are given in the Driving Accessories tables on pages 6 and7, and they interface between the earth rod driving end and the mechanical hammer.

General note: Very light and very heavy hammers with a long stroke are not suited to earthrod driving. Medium tools in the 71/2 to 12 kgs range with a stroke of approximately 58 to108mm delivering 2200 blows per minute are ideal for normal applications.

a. Electric hammers - typical are Kanga models 1800, 900 or 950 and similar weightequipment suitable for light driving to medium depths - Fig 9. The Kanga model 2500, aheavy duty hammer, is suited to deeper driving and heavier earth rods but should be rigmounted because of its size and weight.

b. Pneumatic hammers - typical are Atlas Copco, Cobra, and similar chipping hammersin the 7kg range with speeds of around 2000 blows per minute.

c. Petrol engine driven hammers - of which Pionjar, Atlas Copco and similar are suited.These have the advantages of being self-contained and independent of compressed air orelectricity supply for operation.

Driving an earth rod with a mechanical hammer calls for special care to ensure the force of theblows are axial to the rod. While it may be possible to maintain this when manually using alight type hammer such as an electric Kanga, it is certainly advisable to use rig mounting toensure correct driving especially when it comes to driving the longer earth rods.

Machine drilling equipment is available commercially and ranges from electric, pneumatic andpetrol-driven drills and augers to hydraulic plant with diamond bits that can penetrate rock.

There are two methods of installing earth rods into the drilled hole. One method is to backfillthe hole with dry EARTHRITE and as extendable rods are driven to the required depth, wateris poured into the backfilled hole.

The second option is to assemble the extendable rods together and insert into the drilled hole.A thick, well mixed slurry of EARTHRITE and water is then poured in to backfill the hole.

As a rule of thumb, 20kgs of EARTHRITE will yield a volume of approximately 0.0176 cubicmetres (i.e. roughly 57 bags to the cubic metre).

Section 4 -Getting Down to Earth

Methods of installingEarth Rods

Driving Methods

Drilled Installation

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All the information, including drawings, illustrations and graphic designs contained in this brochure, reflect our present understanding and is to the best of our knowledge and belief,correct and reliable. Users, however, should independently evaluate the suitability of each product for the desired application. Under no circumstances does this constitute an assurance ofany particular quality or performance. Such an assurance is only provided in the context of our product specifications or explicit contractual arrangements. Our liability for this product is setforth in our standard terms and conditions of sale. ALR, AMP, AXICOM, B&H, Bowethorpe, EMP, Cevolit, Critchley, Dorman Smith, Dulmison, Hellstern, La Prairie, Morlynn, Raychem andSIMEL are trademarks of Tyco International Ltd.

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