In Article " Introduction to Grounding System Design – Part One ", I explained the following points:
- Differences between Grounding and Earthing Terms,
- Differences between Grounded and Grounding systems,
- Differences between Bonding and Grounding,
- Grounding and bonding systems definitions.
Also, In Article " Introduction to Grounding System Design – Part Two ", I listed the Factors that must be considered in the construction of the earthing system, which were:
- Function,
- Type,
- Electrical properties,
- Construction material.
And, I explained the Functions of the Earthing System in this Article.
Today I will explain the different Types of Earthing Systems as follows.
Types of Earthing System (on LV Systems and Within Premises)
Different Types Of Earthing Systems
the Earthing systems can be divided according to
the following factors:
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Types of Earthing Systems according
to its Function
Generally,
the earthing systems can be divided to Six types according to function as
follows:
All of these systems are installed similarly. However, their purposes
are quite different. Some of the systems carry little or no current. Others
carry small to moderate currents at 50 or 60 Hz. Still others must be able to
carry currents over a very broad range of frequencies in order to be
considered effective. In the
following paragraphs, I will discuss each type in detailed.
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1- Static Grounding
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2- Equipment grounding "Safety grouding"
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3- System grounding "Functional earthing"
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4- Lightning protection grounding
Main lightning protection grounding requirements are dependent upon
the structure, component, or system to be protected. This system will be
discussed later in separate Articles.
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5- Electronic and computer grounding
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6- Maintenance safety grounding
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Types Of Earthing Systems According
To Its Size
Generally,
the earthing systems can be divided to Two types according to system size as
follows:
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1- Simple Earthing Systems
Simple
consist of a single ground electrode driven into the ground. The use of a
single ground electrode is the most common form of grounding and can be found
outside your home or place of business. This single electrode can be:
1- Single Ground Rod
One single ground electrode may be
sufficient for an electrical installation in a built up area where the local
supply authority utilizes a multiple or common multiple earth neutral system.
However, it may not provide adequately low impedance for lightning current
injection.
2- Single Strip End
Connected
This is a common option for
installations where, because of rock, driving an electrode is impractical.
It is not recommended for lightning
protection systems as there is only one path. Very high ground voltages will
be experienced at the injection point.
3- Single Strip Center Connected
Since the connection to the strip is
at the center, any fault/injection current travels in two directions.
This layout has lower impedance, but
it is generally not adequate for lightning protection systems.
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2- Complex grounding systems
Complex
grounding systems consist of multiple ground rods connected, mesh or grid
networks, ground plates and ground loops. These systems are typically
installed at power generating substations, central offices and cell sites.
Some types of complex grounding system are:
1- Radial Grounding, Single Radials
A design that is well suited to
lightning protection in areas of medium resistivity. The radials can run to
100 feet in length.
2- Radial Grounding, Multiple
Radials
Crows foot design. Well suited to
lightning as it allows energy to diverge as each conductor takes a share of the
current, offering lower impedance. Voltage gradients leading away from the
injection point will be lower, reducing danger from step potentials.
3- Equipotential Mesh Electrodes
Minimize the risk of step and touch
potential hazard by positioning a mat and bonding it to the structure or
operating handle at locations where personnel may be required to operate switchgear
or stand in the course of their duties. Low ground impedance.
4- Grid Electrodes
Grounding for installations where
there is concentration of electrical equipment, such as electrical
substations, are often designed to meet a specific value of resistance
(typically 1 ohm).
Under fault conditions, a grid can
dissipate currents over a large area.
5- Grid with Ground Rods
It may be advantageous to add ground
rods to the grid. In doing so, it may be possible to access a low resistivity
soil layer. Care must be taken to ensure each ground rod is spaced at least
twice the installation depth.
6- Ring Electrode
Installations, including
communications huts, pad mount transformers and fences surrounding high
voltage installations, are generally surrounded by a ground ring. This
practice also reduces the hazard of step and touch potential.
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In the next Article, I will continue explaining Other Types of Earthing Systems. Please, keep following.
انا لم أفهم اخى العزيز الجزء الخاص ب :
ReplyDeleteSingle Strip End Connected
وبحثت عنه وجدت انهم يستخدمون ما يسمى ب L SHAPED Earthing Electrode for Rocky/Hilly Areas
ولكنى لم افهم كيف يتم وضعه بالأرض , فهل يضعون الجزء القصير منه والجزء الطويل يكون مسطحا وظاهرا على الأرض ,
وأيضاً الفرق بين Equipotential Mesh Electrodes وال Grid Electrodes
هل الفرق انه فى ال Equipotential Mesh Electrodes
يتم التوصيل من منتصف الشبكة
اما فى حالة الGrid Electrodes
يتم التوصيل من بداية الشبكة ام ماذا ؟؟؟
وأيضا هل معنى ال Ring Electrode
هو محاصرة المكان المراد تأريضه بأربعة الكترود من الجهات الأربعة أما ماذا ؟؟؟
Question in English:
- can you explain the Single Strip End Connected much more and how L SHAPED Earthing Electrode for Rocky/Hilly Areas is connected ??
- what is the deference between Equipotential Mesh Electrodes & Grid Electrodes ??? is the difference in the point of connection ???
- does Ring Electrode mean surrounding the place with four electrodes and connecting them together ??