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Conductor continuity test and insulation resistance test is carried out with the help of
megger
impulse generator
multimeter
earth tester
megger
A Megger (high-range insulation tester) is used to perform insulation resistance tests and conductor continuity tests on electrical equipment and transmission lines. It applies a high direct current (DC) voltage to measure high insulation resistance (in Megohms) and checks continuity by verifying ultra-low resistance across conductor loops.
IS 10810 / IEEEStd 43
A Megger (high-range insulation tester) is used to perform insulation resistance tests and conductor continuity tests on electrical equipment and transmission lines. It applies a high direct current (DC) voltage to measure high insulation resistance (in Megohms) and checks continuity by verifying ultra-low resistance across conductor loops.
R=IVтАЛ тАФ Insulation resistance calculation formula
RinsтАЛтИЭLength1тАЛ тАФ Insulation resistance variation with length of line/cable
A Megger operates on the electromagnetic induction principle (or uses an electronic inverter with a battery) using a ratio-meter mechanism. It consists of two coilsтАФa Current Coil (CC) and a Voltage Coil (VC)тАФpositioned in a magnetic field. The torque generated depends on the ratio of voltage to current (R=V/I), making the reading independent of slight voltage variations.
Megger generates high direct voltage DC (500┬аV, 1000┬аV, 2500┬аV, or 5000┬аV) to test insulation.
Continuity test with Megger ensures that there is no open circuit break in the conductor.
Insulation Resistance (IR) value decreases as the cable length increases.
A good insulation typically gives resistance in the range of Megohms (M╬й) or Gigohms (G╬й).
Provides highly reliable insulation measurements at high voltages.
Portable and capable of testing long overhead lines and underground cables.
Hand-cranked type requires manual effort to maintain constant speed.
Can damage sensitive low-voltage electronic components if tested at high megger voltage.
Continuity test of overhead conductors and underground cables.
Insulation resistance measurement of transformers, motors, and line insulators.
Option B (Impulse generator) is used for high-voltage lightning surge withstand testing.
Option C (Multimeter) is used for low-voltage parameters (V, I, low R) and cannot generate high voltage required for IR tests.
Option D (Earth tester) is specifically used for measuring earth electrode resistance and soil resistivity.
A is correct тАФ Megger is specifically designed to supply high DC voltage to measure high insulation resistance (M╬й) and check conductor continuity.
Remember: Cable insulation resistance is inversely proportional to cable length (RinsтАЛтИЭL1тАЛ), whereas conductor resistance is directly proportional to length (RтИЭL).