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7/30/2019 Earthing System Measurement
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EARTHINGSYSTEM-MEASUREMENT
Performance of an earthing system can be evaluated by
measurement of earth resistance of the earthing system.
Results of measurement of an earthing system can be
used not only for confirming the adequacy of its design
and construction but also for determination ofadditions/modifications to be carried out in future.
At a station, the measurements are made initially when
the station is not energised to determine the earthresistance for comparison with designed value and
during station life periodically to monitor the condition of
earthing system.
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EARTHINGSYSTEM-MEASUREMENT
Measurement of ground resistance or impedanceand potential gradients on the surface of the earthdue to ground currents are necessary to :
Verify the adequacy of a new grounding system
Detect changes in an existing grounding system
Determine hazardous step and touch voltages
Determine ground potential rise(GPR)in order todesign protection for power and communicationcircuits
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EARTHINGSYSTEM-MEASUREMENT Earth resistivity measurement are useful for:
Estimating the ground resistance of a proposed substation or transmission tower
Estimating potential gradients including step and touchvoltages
Computing the inductive coupling between neighboringpower and communication circuits
Designing cathodic protection systems
Geological surveys
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EARTHINGSYSTEM-MEASUREMENT
Measurement of soil resistivity
Four point method
The most accurate method in practice of measuring theaverage resistivity of large volumes of undisturbed earthis the four point method.
Small electrodes are buried in four small holes in theearth, all at depth band spaced(in a straight line) atintervals a.
A test current I is passed between the two outerelectrodes and the potential V between the two innerelectrodes is measured with a potentiometer or highimpedance voltmeter. Then V/I gives the resistance R inohms
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EARTHING SYSTEM - MEASUREMENT
WENNERS FOUR PROBE METHOD
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EARTHING SYSTEM - MEASUREMENT
RESISTIVITY
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EARTHINGSYSTEM-MEASUREMENT
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EARTHINGSYSTEM-MEASUREMENT
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EARTHING SYSTEM - MEASUREMENT
RESISTIVITY
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EARTHING SYSTEM - MEASUREMENT
PRINCIPLE11
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EARTHINGSYSTEM-MEASUREMENT
MEASUREMENTOFRESISTANCEOFEARTHSYSTEM
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EARTHING SYSTEM - MEASUREMENT
CURRENT PROBE DISTANCE
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EARTHINGSYSTEMMEASUREMENT
RESISTANCEMEASUREMENTFORLARGESYSTEMBYSLOPE
METHOD
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EARTHINGSYSTEMMEASUREMENT
RESISTANCEMEASUREMENTFORLARGESYSTEMBY
SLOPE METHOD
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TABLE FOR SLOPE CO EFFICIENT
SLOPE METHOD
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MEASUREMENT OF LARGE
ELECTRODE SYSTEM
INTERSECTION OF CURVES METHOD
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MEASUREMENT OF LARGE
ELECTRODE SYSTEM
INTERSECTION OF CURVES METHOD
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MEASUREMENT OF LARGE
ELECTRODE SYSTEM
INTERSECTION OF CURVES METHOD
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EARTHINGSYSTEMMEASUREMENT
INTEGRITYCHECKFORSUBSTATIONEARTHSYSTEM11
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