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7/30/2019 138073736 Practical Guide to Good Earthing
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INSULATORSMORLYNN
A
GuidePractical
TO
GoodEARTHING
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Section 1 -
The Basics of Earthing
What is Earthing?
Purpose of Earthing
Chief requirementof good Earthing is
low soil resistivity
The Earth Path
Principal factors
affecting 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. Type of soil
Soil 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 moisture
content is not subject to drying out, that is important in securing a good electrical earth. ReferTable 1 for typical soil resistivity values.
2. Climate
Obviously arid and good rainfall climates are at opposite extremes for conditions of soilresistivity.
3. Seasonal conditions
The 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. Other factors
Other 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
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Potential (P)Probe Current (C)Probe
Depth
300 to
500mm
Earth rod
under 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. Measuring resistance
Figure 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 manufacturers 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. Measuring soil resistivity
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:
= 2 a R (Ohm metres)
where = apparent soil resistivity
a = spacing of probes in metres
R = 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 ofa 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 1
Resistivity Values for Several Types of Soils and Water
Type of Soil or Water Typical Resistivity m Usual Limit m
Sea Water
Clay
Ground well and spring water
Clay and sand mixtures
Shale, slates, sandstones, etc
Peat, loam and mud
Lake and brook water
Sand
Morane gravel
Ridge gravel
Solid granite
Ice
2
40
50
100
120
150
250
2,000
3,000
15,000
25,000
100,000
0.1 to 10
8 to 70
10 to 150
4 to 300
10 to 1,000
5 to 250
100 to 400
200 to 3,000
40 to 10,000
3,000 to 30,000
10,000 to 50,000
10,000 to 100,000
Table 2
Variations of Soil Resistivity with Moisture Content
Moisture Content
% of Weight
Typical Value of Resistivity mClay mixed with sand Sand
0
2.5
5
10
15
20
30
10,000,000
1,500
430
185
105
63
42
---
3,000,000
50,000
2,100
630
290
---
Table 3
Variation of Resistivity with Temperature
in a Mix of Sand and Clay with a Moisture
Content of about 15% by Weight
TemperatureoC
Typical Value of Resistivity
m
20
10
0 (Water)
o (Ice)
-5
-15
72
99
138
300
790
3,300
Site Testing Essential
Lower layer
more conductive
Middle layer less
conductive
Lower layer more
conductive
Spacing (m)
(Depth)
Spacing (m)
(Depth)
Apparentsoilresistivity
(Ohm/m)
A
pparentsoilresistivity
(Ohm/m)
Fig. 5
Typical curve of apparent soil resistivity for 2 layer soils
Fig. 6
Typical curve of apparent soil resistivity for 3 layer soils
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250mm
Section 2 -
About Earth Rods
Types of Earth Rods
Steel core Earth
Rods have the best
attributes
Extendable Earth Rod
Coupling Systems
Earth Rod length
more important
than 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 Dulmisons 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 Ohms
= soil resistivity in Ohm metres
L = length of earth rod in metres
d = 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
( ln ( 8L ) - 1 ) Ohms
2L d
0 1.5 3.0 4.5 6.0
5Re
sistanceinOhms
510mm
500mm
250mm
510mm
1000mm
250mm
520mm
500mm
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
PLP 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 PLPs extendable earth rods is the low prole of the couplings. While theush (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 t to the earthrod. Both the ush and taper coupling designs provide excellent electrical connection asproven in laboratory testing and experience in service.
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5
A Practical Guide to Good Earthing
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 the
same 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 rods
in parallel
Copper
vsStainless Steel
Test showsno detectable corrosion
(after 10 years
in salty soil)
PLP 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 PLP stainless steel clad earth rods are favoured overcopper clad are -
PLP 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.
Cross section of copper sheathed PLP earth rod described above,
at 4x magnication after 10 years in salt-laden soil.
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Section 3 -
Everything for Earthing
6
Earth Rods - General
Dulmison earth rods have a structural steel core with an
outer 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 intoDulmisons 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 Series Copper Clad Rods
Rod Diameter
1440
1800
1800
2400
CNE1314
CNE1318
CNE1518
CNE1524
10/500
5/500
5/500
5/500
Cat. Numbers Pack/Bulk Qty
Domestic Rod Pack - CNE1314T
10 pcs/pk
10 pcs/pk
CNE1314
EC13D
Domestic earth rod
Earth clip
Domestic earth rod clip EC13D. Suitablefor cables in the range 6 - 16mm2
Certificate of Suitability CS571N
Rod Length
13
13
15
15
SNE Series Stainless Steel Clad Rods
Rod Diameter
1440
1800
SNE1314
SNE1318
10/500
5/500
Cat. Numbers Pack/Bulk QtyRod Length
13
13
Consult office for additional information &/or sizes
Commercial/Industrial LGR Series 19mm Copper Clad Rods
1800
2400
3000
3600
4500
LGR1918
LGR1924
LGR1930
LGR1936
LGR1945
1/20
1/20
1/20
1/20
1/20
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 Series Copper Clad Rods
RodLength
CTE1512
CTE1514
CTE1518
- - -
CTE1524
CTE1530
- - -
- - -
- - -
CTE1920
- - -
- - -
15mm Dia. 19mm Dia.13mm Dia.Pack/
Bulk QtyPack/
Bulk QtyPack/
Bulk Qty
1200
1440
1800
2000
2400
3000
CTE1312
CTE1314
CTE1318
- - -
CTE1324
CTE1330
10/500
10/500
5/500
- - -
5/500
1/50
10/500
10/500
5/500
- - -
5/500
1/40
- - -
- - -
- - -
1/20
- - -
- - -
Earth Rod Accessories
Coupling
Point
Star Point
CCT15
DPT15
SDP15T
CCT19
DPT19
- - -
CCT13
DPT13
SDP13T
10/100
50/200
10/100
10/100
50/200
10/100
10/50
10/50
- - -
Driving Accessories
Hand
Kango 950
A/C Tex 11
A/C Cobra
DHT15
MDH15K
MDH15A
MDH15AC
5/25
Each
Each
Each
5/25
- - -
- - -
- - -
DHT19
- - -
- - -
- - -
STE Series Stainless Steel Clad Rods
RodLength
STE1412
STE1415
STE1418
STE1424
STE1430
14mm Dia.13mm Dia.Pack/
Bulk QtyPack/
Bulk Qty
1200
1440
1800
2400
3000
STE1312
STE1314
STE1318
STE1324
STE1330
10/500
10/500
5/500
5/500
1/50
10/500
10/500
5/500
5/500
1/40
Earth Rod Accessories
Coupling
Point
Star Point
SCT15
DPT15
SDP15T
10/100
50/200
10/100
SCT13
DPT12
SDP12T
10/100
50/200
10/100
Driving Accessories
Hand
Kango 950
A/C Tex 11
A/C Cobra
DHT15
MDH15K
MDH15A
MDH15AC
5/25
Each
Each
Each
Type
CNE
Type
LGR
* Add (D-) in front of all part numbers. Example: D-CNE 13 14.
D-
*
*
**
*
*
*
D-
*
*
*
PLP earth rods have a structural steel core with an
outer 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.
PLP Earth Rods
Are Energy Authority approved around Australia andthe South Pacic
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 t of
earth clips comply with AS1882 Can be formed around footings without damage to
cladding or core Are 100% Australian made - labour and materials
All PLP 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 ttings that have been made frominferior materials such as brass. In fact, the EarthingHandbook expressly forbids the use of brass in buriedsituations. This design philosophy has been carried overinto PLPs range of earthing connectors.
PLP 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 at tip was developed forpenetrating all types of soil.
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7
A Practical Guide to Good Earthing
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. Asecure and non-detachable joint is achieved bymeans of the pins 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 the
connection 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. ERB1
Aluminium alloy casting
Cat. No. ERB3
Polymer concrete
CCE Series Copper Clad Rods
RodLength
CCE1312
CCE1314
CCE1318
CCE1324
CCE1330
CCE1512
CCE1514
CCE1518
CCE1524
CCE1530
10/500
10/500
5/500
5/500
1/40
10/500
10/500
5/500
5/500
1/50
15mmDia.
Pack/Bulk Qty
Pack/Bulk Qty
13mmDia.
1200
1440
1800
2400
3000
Earth Rod Accessories
Coupling
Point
Star Point
CCA15
DP15
SDP15
25/100
50/200
10/100
10/100
25/200
10/100
CCA13
DP13
SDP13
Driving Accessories
Hand
Kango 950
A/C Tex 11
A/C Cobra
Drive Pin
DH15
MDH15DF
MDH15AF
MDH15C
MDP10M
5/30
Each
Each
Each
100
SDE Series Stainless Steel Clad Rods
Rod Length
SDE1414L 10/500
Pack/Bulk Qty14mm Dia. Pin Lock
1440
Earth Rod Accessories
Coupling
Point
Star Point
C14L
DP14
SDP14D
25/75
50/200
10/100
Driving Accessories
Hand
Coupling Tool
DH14
CT14
5/30
5/25
Earthing Enhancement Compounds
Cat. No.
Conforms to
AS2239
N/A
Conforms to
AS2239
Bentonite, Gypsum, Sodium Sulphate
Bentonite, Gypsum, Sodium Sulphate
Calcium, Bentonite, Natural Gypsum
StandardComposition
EARTHFIL
EARTHRITE
EARTH5050
* Add (D-) in front of all part numbers. Example: D-CNE 13 14.
*
*
*
*
*
*
*
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Section 3 -
Everything for Earthing
8
Earth Rod Clamps
Single 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 Mats
Earth 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 Bond
For 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. No. C70
Mains cable
Bonding cable
3 sec current rating
Lug diameter
Terminal thread
Thread depth
50 - 630mm2
70mm2
10kA
10mm
M10
20mm
Cat No.
GRC5
CLAMP210
EP1
13 - 15
13 - 15
17 - 19
100
10/50
40
10 - 35
16 - 120
16 - 120
4.05 - 7.65
5.10 - 14.21
5.10 - 14.21
Rod Dia.mm
PackQty
Conductor Sizecsa mm2 Diameter mm
Type GRC5 Clamp 210
Type EP Type ET
Cat No.PackQty
GB1
GB2
GB3
EL21090
25
20
10
10
13 - 19
13 - 19
13 - 19
12 - 15
16 - 35
50 - 120
150 - 185
35 - 120
5.1 - 7.7
8.9 - 14.2
15.7 - 17.6
7.6 - 14.2
Rod Dia.mm
Conductor Sizecsa mm2 Diameter mm
CatNo.
PackQty
EP3EP4
ET1
ET2
ET4
2020
25
15
10
13 - 1913 - 19
13 - 19
13 - 19
13 - 19
16 - 3550 - 120
16 - 35
50 - 120
50 - 120
5.1 - 7.78.9 - 14.2
5.1 - 7.7
8.9 - 14.2
8.9 - 14.2
22
2
2
3
11
2
2
3
RodDia. mm
Conductor SizeDia. mm
No. ofConductors
FigNo.csa mm2
Fig. 1 Fig. 2 Fig. 3
Kit
Earthmat
Cat. No.
EARTHMAT
KITY
Material: Galvanised mild steel
Size: 1500mm x 900mm
Mesh: 76mmx 50mm
Installation kit for type RDB rotaryswitches with earth switch.
Description
* Add (D-) in front of all part numbers. Example: D-CNE 13 14.
*
*
*
**
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A Practical Guide to Good Earthing
Catalogue
No.
Pack
QtyOpen Section
Tap off Conductor
Dia. mm
CEC15000
CEC15035
CEC15070
CEC15120
50
40
40
50
Conductors
50 - 120mm2
or Earthrods
13 - 15mm dia.
Blank
8.4
11.0
15.0
Blank
25 - 40
50 - 70
95 - 120
DU1315
Crosssection
mm2
Die
Set
Catalogue
No.
Pack
Qty
Conductor
Combination
mm2
CEC050
CEC070
CEC095
50
50
50
DUOT
DUOT
DU1315
70 - 35
70 - 50
50 - 50
50 - 50
70 - 50
70 - 70
70 - 95
95 - 95
Die
Set
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 isrecommended.
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
* Add (D-) in front of all part numbers. Example: D-CNE 13 14.
*
*
PLP CEC connectors were specically developed to dissipate surges of high fault currentquickly and effectively to limit any potential damage to equipment, and to safeguardpersonnel close to that equipment.
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Section 3 -
Everything for Earthing
Airport Earthing Terminal
Survey and Mapping
Datum Marks
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
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
10
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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 the
earth 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 installing
Earth Rods
Driving Methods
Drilled Installation
Fig. 9
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 PLP extendable series earth rods.
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A Practical Guide to Good Earthing
PLP Australia190 Power StreetGlendenningNSW 2761 Australia
Mail Address:PO Box 626St. MarysNSW 1790 Australia
Telephone: +612.8805.0000Fax: +612.8805.0091Web Site: www.preformed.com.au
Email: [email protected]
2012 Preformed Line Products
Printed in Australia