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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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