FURSE materiāli, zibensaizsardzības un zemējuma risinājumi

2018
Earthing
An Overview of Earthing
Gary Blackshaw, Global Business Development Manager

History
Furse Overview
May 24, 2018 Slide 2
1893 2018
FoundedbyWilliamJosephFurse
OriginallyasaSteeplejackcompany
Celebrating125yearsinbusiness
1998
AcquiredbyThomas&Betts
1907
RelocatedtoTrafficStreet
MoreemphasisonEngineering
1912
IncorporatedasWJFurse&CoLtd
1937
WilliamJosephFursepassedaway
1950
PremisesbuiltatWilfordRoad
1987
Twobuy-outstookplace
1990
AcquiredbyEastMidlandsElectricityPLC
1958
AcquiredbyEVHoldings
1967
AcquiredbyCrownHouse
1996
AcquiredbyCinvenLtd
125 years of history & experience!
125 years of reliability & trust!
1993
Celebrated100yearsinbusiness
2012
ABBacquiredThomas&Betts

Divisions, business units & product groups
ABB Organization
Cable Ties,
Metal Framing,
Duct, Cable
Tray
Connectivity
& Grounding
Cable
Protection
Systems
Emergency
Lighting
Explosion
Protection
Cable
Apparatus
& Accessories
Solar
Distribution
Solutions
Building
Products
Protection &
Connection
Installation
Products
Discrete Automation
& Motion
Electrification
Products
Process
Automation
Power
Grids
Group
Divisions
Business Units
Product Groups

Where we make a difference
Furse Overview
Oil & Gas / Petrochemical Utilities / Energy Cultural & Heritage
Data Centers Rail & Infrastructure High Tech & Industrial
The Furse Total Solution for all project types and industry sectors worldwide

Earthing Systems
Earthing
Earthing for Lightning Protection Systems
 Applicable to Lightning Protection
systems
 IEC/BS EN 62305 Lightning Protection
Standard
 Generally simple
Power Earthing Systems
 Applicable to Substations, Power Stations,
Transformers, Transmission Lines,
Telecommunication Lines, Wind Farms,
Solar Farms, Data Centres etc.
 Various Standards
 Generally very complex

Earthing Systems
Earthing
 Lightning protection earthing systems are designed for high frequency applications.
For example, a lightning current will typically reach peak value between 10 and 20
microseconds whereas power earthing systems are generally designed for
applications operating at relatively low frequency and time spans from 0.2
milliseconds to 5 second duration
 Lightning protection standards recommend a resistance to earth of 10 Ω or less in
most cases
 Power earthing systems will typically require far lower values, calculated for each
separate project
 To achieve the low resistance values, designing a power earthing system requires
much more thought, information, and application than just simply installing an array
of rods into the ground as is fairly common practice

—

Functions of the Earthing System
 Safely & effectively dissipate the lightning current into the ground / earth
 Earthing products for use in lightning protection systems are designed to safely &
effectively dissipate lightning current to earth, whilst withstanding the stresses
placed on them
 Equipotential bonding is equally vital to prevent dangerous sparking between the
LPS and other components such as: metal installations, internal systems, external
conductive parts and lines connected to the structure. The products are designed to
achieve equipotential bonding of metal parts within and around the structure

Basic Principles of Lightning Protection
Lightning Protection
1. Capture/intercept the lightning
strike (air termination network)
2. Safely conduct the lightning
current to earth (down conductor
System)
3. Safely & effectively dissipate the
lightning current into the ground
(earth termination system)
4. Provide equipotential bonding &
electrical insulation (separation
distance) to prevent dangerous
secondary sparking
5. Protect against the secondary
effects of lightning caused by
surges & transients (i.e. SPDs)
1
2
3
4
5

Earth Termination Systems
Lightning Protection Standard IEC/BS EN 62305
May 24, 2018 Slide 10
 Recommended resistance of 10 Ohms or less in most situations
 The standard recommends a single integrated earth termination system for a
structure, combining lightning protection, power systems and telecommunication
systems
 The main principle behind such a system is to ensure that all systems are at the
same electrical potential in the event of a fault or lightning strike, thus
minimising and hopefully avoiding any risk of secondary flashing or arcing
between the various electrically connected parts of the structure and the
equipment contained within
 Note - Local electrical requirements and regulations may not permit the LP and
power earthing systems to be interconnected

Earth Termination Arrangements
Lightning Protection Standard IEC/BS EN 62305
May 24, 2018 Slide 11
Type A arrangement
 Vertical rods or horizontal radial
electrodes
 Connected to each down conductor
Type B arrangement
 Unbroken ring conductor around
perimeter of structure – depth >0.5m & 1m
from building edge
 Foundation reinforcement – piles or raft

What Do We Mean By “Earthing”?
Earthing
May 24, 2018 Slide 13
By “Earthing” we generally mean an electrical connection to the general
mass of earth.
The mass of earth generally being a volume of soil/rock whose dimensions
are very large in comparison to the electrical system being considered.

Functions of an Earthing System
Earthing
May 24, 2018 Slide 14
 Earthing is generally provided for reasons of safety
 To provide a definite path for fault currents from a fault point back to the
associated system neutral
 To provide a low impedance/resistance to ensure satisfactory protection system
operation under fault conditions
 To limit as far as it is practicable, the rise of earth potential under fault conditions to
a value that can safely be transferred outside the site boundary to a third party
 To eliminate persistent arcing ground faults
 To provide an alternative path for induced currents thereby minimising the electrical
noise in cables
 To ensure that a fault which develops between high and low voltage windings of a
transformer can be detected by primary protection systems

Standards -
Earthing
May 24, 2018 Slide 16
In Great Britain, earthing of an electricity supply system is governed by the:
 Electricity Safety, Quality and Continuity Regulations 2002
 Electricity at Work Regulations 1989
 Construction Design and Management (CDM) Regulations 1994
Breaches of the above constitute a criminal offence
 BS EN 50522: 2011 – Earthing of power installations exceeding 1 kV a.c.
 BS7430: 2011 - Code of practice for protective earthing of electrical installations
 BS7354: 1992 - Design of high-voltage open terminal substations
 BS7671: 2000 - Requirements for electrical installations
 BS EN IEC 61936-1: 2001 - Power installations exceeding 1 kV a.c. – Part 1: Common rules

Standards – US
Earthing
May 24, 2018 Slide 17
 IEEE Std 80 – 2000 - IEEE Guide for Safety in AC Substation Grounding
 IEEE Std 81 – 1983 – Guide for measuring Earth Resistivity, Ground
Impedance…..
 IEEE Std 142 – 1991 – Grounding of industrial and commercial power
systems
 IEEE Std 367 – 1996 – IEEE Recommended practice for Determining the
Electric Power Station Ground Potential Rise and Induced Voltage from a
Power Fault
 IEEE Std 665 – 1987 – IEEE Guide for Generating Station Grounding

Soil Resistivity
Earthing
May 24, 2018 Slide 19
 One of the most important factors
influencing the performance of an
earthing system
 The resistance to earth of a given
electrode depends upon the electrical
resistivity of the earth i.e. the actual
soil where the earth electrodes will be
positioned
 The resistivity of soil can vary not only
geographically but across the same
site, and quite dramatically at different
depths
 Different layers of strata will affect the
distribution of current passing through
the electrode

What Factors Influence Soil Resistivity?
Earthing
May 24, 2018 Slide 20
 Type of soil
 Moisture content
 Temperature
 Chemical composition
 Compactness/Density
 Seasonal variation
 Artificial treatment

—
Soil Resistivity Measurement

Soil Resistivity Measurement
Earthing
May 24, 2018 Slide 22
 The resistivity of soil can vary not only
geographically but across the same
site, and quite dramatically at different
depths
 Different layers of strata will affect the
distribution of current passing through
the electrode
 Generally the soil is made up of varying
layers of material, different thickness’
therefore differing resistivity values
 Soil resistivity measurements will
determine the soil resistivity for
different depths

—
Earthing Materials and Connections

Earthing System
Dedicated Earthing
May 24, 2018 Slide 24

Earth Electrode - Conductor
Earthing
May 24, 2018 Slide 26
 Earthing conductors form an integral part of the single earthing arrangement,
whether they provide the means of connection to the final earth electrode (earth rod
or plate), or whether they comprise the earth electrode itself (through an earth grid
or ring earth arrangement)
 An earth conductor must be capable of carrying the maximum expected earth fault
current and leakage current likely to occur at a structure. The size or minimum cross-
sectional area of the conductor must therefore be calculated through the
specification of fault current, duration, and jointing type.
 A good earth conductor must also:
 Be able to withstand mechanical damage
 Be compatible with the material of the earth electrode
 Resist the corrosive effect of local soil conditions

Earth Electrode - Rods
Earthing
May 24, 2018 Slide 27
Copperbond Rod
 Molecularly bonding 99.99% pure
electrolytic copper on to a low carbon
steel core (not sheathed type)
 No interface or gap between the two
metals due to the bond at molecular
level which means a dissimilar metal
reaction cannot occur and the copper
cannot be separated from the steel
 Highly resistant to corrosion
 High tensile strength steel core means
they can be driven to great depths
Copperbonded / Solid Copper / Stainless Steel

Earthing
May 24, 2018 Slide 28
Solid Copper Rod
 99.99% pure copper
 Offers greater resistant to corrosion
 Ideally used in applications where soil
conditions are very aggressive, such as
soils with high salt content
 Lower strength

Earthing
May 24, 2018 Slide 29
Stainless Steel Rod
 Stainless Steel
 Used to overcome many of the
problems caused by galvanic corrosion
which can take place between
dissimilar metals buried in close
proximity
 High strength

Earth Electrode - Comparing Copperbonded & Galvanised Steel Rods
Earthing
May 24, 2018 Slide 31
 Copper is resistant to corrosion in most soils
 Zinc is sacrificial in most soils and with respect to most metals
 Corrosion protection mechanisms are different;
 The copper coating is designed to prevent corrosion of the steel core
 The zinc coating will delay corrosion of the steel core by providing a sacrificial
barrier

Earthing
May 24, 2018 Slide 32
¾” Galvanised Steel Earth Rod
5/8” Copperbonded Steel Earth Rod
Earth Electrode Rods excavated after 12 years
The loss of zinc on the galvanized
steel earth rod resulted in
excessive corrosion of the steel
The copperbonded steel earth
rod showed minimal corrosion

Earthing
May 24, 2018 Slide 33
Galvanised Earth Electrode Rod excavated after 11 years
Galvanised Steel Earth Rod
The loss of zinc resulted in
excessive corrosion of the steel.
One area is reduced from a ¾”
diameter to approximately a ¼”
diameter due to the corrosion
The eventual failure could result
in a potential, critical earthing
system collapse!

Corrosion
Earthing
May 24, 2018 Slide 34
Copper is one of the better and commonly used materials for earth electrodes. Solid
copper is particularly suitable and recommended where high fault currents are
expected

Corrosion
Earthing
May 24, 2018 Slide 35
Earth electrodes, being directly in contact with the soil, shall be made of materials
capable of withstanding corrosion. The factors associated with the corrosion of metals
in contact with soil that should be considered are;
 The chemical nature of the soil
 pH value (acidity/alkalinity)
 Salt content
 Differential aeration / drainage
 Presence of bacteria
The material has to resist the mechanical influences during their installation as well as
those occurring during normal service

Earth Electrode - Plates & Mats
Earthing
May 24, 2018 Slide 36
Difference in voltage potential
minimized through use of earth mat
Voltage potential curve
Image is for illustration purposes only
100V
600V
400V Difference
50V
50V Difference
1000V

Earth Electrode - Plates & Mats
Earthing
May 24, 2018 Slide 37
Copper Earth Plates
 Alternative style of electrode where
there is high resistivity soil or where
rock conditions prohibit the driving of
rods
Copper Earth Lattice Mat
 Designed to minimize the danger of
exposure to high step and touch
voltages to operators in situations such
as high voltage switching

Earth Electrode – Connections / Joints
Earthing
May 24, 2018 Slide 38
 It is critical that the earth electrodes connections / joints are conductively and
mechanically stable and reliable
 Mechanical (compression, bolted etc.) connections / joints rely on surface contact
and physical pressure to maintain connection
 Exothermic welded connections / joints form permanent, high quality electrical
connections
Compression Connection Mechanical Connection Exothermic Connection

Earth Electrode – Connections / Joints
Earthing
May 24, 2018 Slide 40
FurseWELD Exothermic Welding offers the
following advantages;
 Connections are designed to have a larger
cross-sectional area than the conductors being
joined
 Equivalent or greater current carrying capacity
 Joints can therefore handle higher fault
currents than using mechanical clamps or
brazing
 Better corrosion properties
 Permanent connections that will not loosen

Where to use it?
FurseWELD Exothermic Welding
May 24, 2018 Slide 41
 Infrastructure projects
 Utility projects
 Power plants
 Substations
 Rail
 Windfarms
 Solar farms
 OHL
 Telecoms

—
Earth Electrode Backfill Materials

Earth Electrode Backfill Materials – Typical Application
Earthing
May 24, 2018 Slide 43
An earth electrode backfill material may be used to reduce the contact
resistance and increase the effective size of earth electrodes, e.g. as a
backfill for earth rods installed in drilled holes or as a layer encapsulating
horizontal earth conductors buried in a trench.

Earth Electrode Backfill Materials – Bentonite
Earthing
May 24, 2018 Slide 44
Bentonite is a moisture retaining clay consisting largely of sodium
montmorillonite, which when mixed with water swells to many times its dry
volume. Its main advantage as far as earthing is concerned, is that it has the
ability to hold its moisture content for a considerable period of time and to
absorb moisture from the surrounding soil.

Earth Electrode Backfill Materials – Bentonite
Earthing
May 24, 2018 Slide 45
 Bentonite will absorb up to five times its weight in water and swell up to
thirteen times its dry volume. At six times its dry volume it is a very
dense, pasty clay that can hold its own shape and will adhere to any
surface it touches. These two characteristics solve the compaction and
soil to rod contact problems
 Bentonite hydrates chemically, holding water in its structure. The
material is a natural clay formed years ago by volcanic action. It is non-
corrosive, stable and will not change characteristics as time elapses
 The resistivity of Bentonite varies from about 3 Wm upwards depending
on its moisture content (BS7430 clause 8.5)
 Generally not used in very dry or free draining locations

Earth Electrode Backfill Materials – FurseCEM
Earthing
May 24, 2018 Slide 46
FurseCEM is a granulated electrically conductive aggregate that replaces
normal concrete fine aggregates such as sand, permitting electrically
conductive concretes to be designed by applying conventional concrete
technology

Step and Touch Potential
Earthing
May 24, 2018 Slide 48
 When the human body is accidentally introduced into the circuit between live
(faulted) metalwork and earth a current may flow that could be lethal
 Current flow is dependant on many factors such as duration, body impedance,
footwear impedance, surface resistivity etc.
 The evaluation of ‘step’ and ‘ touch’ potentials are required by most international
earthing standards
 Most earthing standards set tolerable limits for step and touch potentials which are
determined by the product of allowable body current and the impedance of the
electrocution circuit model
 Definitions of voltage limits varies between standards

Step Potential
Earthing
May 24, 2018 Slide 49
 Step Potential is the difference in surface potential experienced by a person’s feet
bridging a distance of 1m without contacting any other grounded surface
 Step Potential can be controlled by the use of a properly designed ground electrode
system (grid) or the use of insulating ground coverings such as rock chips
50% Voltage drop between feet
Same potential between feet

Touch Potential
Earthing
May 24, 2018 Slide 50
 Touch Potential is the potential difference between EPR and the surface potential at
the point where a person is standing, while at the same time having hands in
contact with a grounded structure
 Touch Potential is controlled by proper bonding and protective systems, such as
personnel safety mats and insulating ground coverings (rock chippings)
No Protection
Same potential as tower

Design Overview
Earthing
May 24, 2018 Slide 52
 A vital first part of the earthing design is the accurate measurement and
interpretation of Soil Resistivity
 Accurate soil resistivity data together with other system design information are of
vital importance as the inputs to complex computer modelling processes
 This data is used to determine “Rise of Earth Potential” values under system fault
conditions
 The data is also used to calculate values of potentially hazardous touch, step and
transfer voltages and determine the “Hot” or “Cold” nature of the site
Hot Site – A site where the rise of earth potential, under the maximum earth fault current condition, can exceed the
value either 430 V or 650 V depending upon the fault clearance time
Cold Site – A site that has a earth potential rise below the telecommunication authorities limits (430 and 650 volts @
50Hzs)

Design Overview – Earthing System
Earthing
May 24, 2018 Slide 53
Using the soil model and taking account of the power system bonding requirements, an
economical earthing system layout can be developed and analysed
Example of a 3D earth electrode layout consisting of vertical electrodes and
horizontal interconnecting conductor tapes

Furse Earthing Design
 C‐DEGS
 Soil resistivity measurements
 System design
 Validation of existing designs
 Step & touch potential
calculations
 Hot / Cold site parameters

Glossary
Earthing
May 24, 2018 Slide 56
 Earth Potential Rise – Voltage between an earthing system and reference earth
 Reference Earth (remote earth) – Part of the earth considered as conductive, the
electric potential which is conventionally taken as zero, being outside the zone of
influence of the relevant earthing arrangement
 Hot Site – A site where the rise of earth potential, under the maximum earth fault
current condition, will exceed the value either 430 V or 650 V depending upon the
fault clearance time
 Cold Site – A site that has a earth potential rise below the telecommunication
authorities’ limits (430 and 650 volts @ 50Hz)
 Rise of Earth Potential (ROEP) - The radial ground surface potential around a earth
electrode referenced with respect to remote earth
 Local Earth – Part of the earth which is in electric contact with an earth electrode
and the electric potential of which is not necessarily equal to zero
 Foundation Earth Electrode – Conductive structural embedded in concrete which is
in conductive contact with the earth via a large surface

Glossary
Earthing
May 24, 2018 Slide 57
 Earth Fault – Fault caused by a conductor being connected to earth or by the
insulation resistance to earth becoming less than a specified value
 Fault Level – The fault level in amps that may be expected to flow through the earth
grid and on which calculations will be based
 Earth Fault Current – Current which flows from the main circuit to earth or earthed
parts at the fault location
 Resistivity – The reciprocal of conductivity. It is the inherent resistive property of a
material. Dimensionally it is resistance x length for a 1 metre cube in Ω/m

ABB Furse
Quality Expectations
 IEC/BS EN 62561 Lightning Protection Component Standard

—
Quality Expectations
 IEC/BS EN 62561 Lightning Protection Component Standard

IEC/BS EN 62561
Recognised Manufacturing Product Standards
IEC/BS EN 62561
Lightning Protection System Components (LPSC)
 Parts 1 – 7
 Governing lightning protection components quality &
performance
 Introduced to be the direct replacement of BS EN 50164

IEC/BS EN 62561
Lightning Protection System Components (LPSC)
 IEC/BS EN 62561-1:2012 Lightning protection system components (LPSC)
Part 1: Requirements for connection components
Part 2: Requirements for conductors and earth electrodes
Part 3: Requirements for isolating spark gaps (ISG)
Part 4: Requirements for conductor fasteners
Part 5: Requirements for earth electrode inspection housings and earth
electrode seals
Part 6: Requirements for lightning strike counters (LSC)
Part 7: Requirements for earth enhancing compounds
IEC/BS EN 62561
Recognised Manufacturing Product Standards

In order to comply with IEC/BS EN 62305 standard the components &
materials used shall comply with the IEC/BS EN 62561 series
Governs lightning protection component quality and performance
Has fully replace BS EN 50164
LPSC which conform to this standard offers assurance that their design
and manufacture is suitable for use in LPS installations.
IEC/BS EN 62561
Product Test Standards

IEC/BS EN 62561-1 Lightning protection system components (LPSC) Part
1: Requirements for connection components
A performance specification attempt to simulate actual installation
conditions
Preconditioning or environmental exposure followed by three 100kA
10/350s electrical impulses (simulating lightning discharge)
IEC/BS EN 62561-1

Examples of components before and after
testing
IEC/BS EN 62561-1

IEC/BS EN 62561-2 Lightning protection system components (LPSC)
Part 2: Requirements for conductors and earth electrodes
A performance specification attempt to simulate actual installation
conditions
Dimensional checks – radial copper thickness & adhesion
Preconditioning or environmental exposure
Bend testing
IEC/BS EN 62561-2

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