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POST-LAB # 03

Group Members:M.Sayem Suleman EE-060

M. Taha a!ar EE-0"

M. $an%sh Ba%& EE-036M. Al% 'a(a EE-0)"

M. A*a! ul +asan EE-30"

,lass: T.E

Se%on: E

,ourse ,o/e: EE-3)

Bah: 0"-"3Lab Teaher: M%ss. 1ar2%s a%ma

4n%5ers%y: 1E$ 4n%5ers%y o! En&%neer%n& Tehnolo&

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Electrical Power Distribution & Utilization Pre Lab#07

DIGITAL EARTH TESTER:

A digital earth tester allows for the measurement of Earth  Resistances and Soil SpecificResistivity, and also the spurious voltages caused  by parasitic voltages present in the soil. This

equipment is suitable for fast and easy measurement of the grounding  resistance in house and

industrial buildings, hospital installations, lightning rods, 

antennas, substations, etc.Soil resistivity measurement allows for soil stratification in order to optimize the most comple

grounding systems engineering. !ts state"of"the"art system of active and passive filters provides it

with high immunity to electric interferences, ma#ing it possible to obtain reliable  measurementseven in the presence of spurious voltages, such as the ones that  can be found in some urban areas

and near primary substations.

SOIL RESISTIVITY:

Soil resistivity is a measure of how much the soil resists the flow of electricity. !t is a critical

factor in design of systems that rely on passing current through the Earth$s surface. An

understanding of the soil resistivity and how it varies with depth in the soil is necessary to design

the grounding system in an electrical substation, or for lightning conductors.

!t is needed for design of grounding %earthing& electrodes for substations and 'igh"voltage direct

current transmission systems. !n most substations the earth is used to conduct fault current when

there are ground faults on the system.

!n single wire earth return power transmission systems, the earth itself is used as the path of 

conduction from the end customers %the power consumers& bac# to the transmission facility. !n

general there is some value above which the impedance of the earth connection must not rise,

and some maimum step voltage which must not be eceeded to avoid endangering people and

livestoc#.

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Electrical Power Distribution & Utilization Pre Lab#07

The soil resistivity value is sub(ect to great variation, due to moisture, temperature and chemical

content. Typical values are)

• *sual values) from + up to + %-"m&

• Eceptional values) from + up to + %-"m&

GROUNDING RESISTANCE:

The earths ground resistance impacts the effectiveness of shunting high voltage surges fromlightning and other sources to the earth. The generally accepted practice is to have the earths

ground resistance not eceed /01. 'owever, to protect communication systems %cell phone sites&

and sensitive electronic installations %computers&, the voltage dissipation capability of the earth%earth ground resistance& might be required to be less than 21 , and in some cases less than +1.

3ailure to provide a low resistive earth ground can result in the migration of voltage fromlightning or line surges onto the premise wiring, which can cause electric shoc# and4or fire

within the building or structure.

3actors that significantly impact the earth ground resistance include the contact resistance of thegrounding conductor to the electrode, the type of electrode used and the resistivity of the soil.