The document discusses various methods for measuring the resistance of materials, which is crucial for cable manufacturers and the maintenance of electrical equipment. It classifies resistance into low, medium, and high categories and outlines techniques for measurement including the Wheatstone bridge, ammeter-voltmeter method, and Kelvin double bridge. Specific formulas for calculating insulation resistance in cables are also provided.

1. MEASUREMENT OF
RESISTANCE
Prepared by,
Madhumitha Jayar

2. WHY resistance of material is measured ???
 Cable manufacturers
 Electric motor & generator manufacturers
 Installation & maintenance of power cables, switchgear &
voltage tap changers
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3. CLASSIFICATION
< 1 Ω
LOW RESISTANCE
1Ω < R < 100kΩ
MEDIUM
RESISTANCE
> 100kΩ
HIGH RESISTANCE
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4. MEDIUM RESISTANCE MEASUREMENT
Wheat stone Bridge
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5. Substitution method
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6. Ammeter-Voltmeter method
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7. LOW RESISTANCE MEASUREMENT
• AMMETER VOLTMETER METHOD
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8. KELVIN DOUBLE BRIDGE
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9. 9
COMMERCIAL KELVIN DOUBLE BRIDGE

10. MEASUREMENT OF HIGH RESISTANCE
DIRECT DEFLECTION METHOD
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Measurement of high resistance having metallic sheath

11. LOSS OF CHARGE METHOD
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R’ = t/(C loge V1/V2 )
While measuring insulation resistance of a cable or
a capacitor the test need not be repeated. In this
case C will be the capacitance of the cable under
test, which must be known and R1 will be the
insulation resistance to be measured. NO external
resistance is to be inserted in the circuit. The value
of R1 then can be obtained directly from the
expression.
R = t/(C log V2/V1 )

12. MEGOHM BRIDGE METHOD
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Modified Wheatstone Bridge

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QUERIES..?