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During Circuit continuity and Insulation resistance test main switch kept?
On condition
Off Condition
Uninstalled
Connected
Off Condition
During electrical continuity and insulation resistance tests, the main switch must be in the 'Off' condition. This ensures that the circuit under test is completely isolated from the main power supply, protecting the measuring instruments (like the Megger or Ohmmeter) from damage and preventing electrical hazards to the personnel.
During electrical continuity and insulation resistance tests, the main switch must be in the 'Off' condition. This ensures that the circuit under test is completely isolated from the main power supply, protecting the measuring instruments (like the Megger or Ohmmeter) from damage and preventing electrical hazards to the personnel.
RinsтАЛ=IleakтАЛVtestтАЛтАЛ тАФ The insulation resistance is calculated by applying a test voltage VtestтАЛ and measuring the leakage current IleakтАЛ.
The insulation resistance test uses a high-voltage DC source (Megger) to measure the resistance of cable insulation. If the main switch were left 'On', the presence of live AC supply would introduce high voltage, causing interference with the measurement or potentially causing a catastrophic short-circuit within the testing device. Similarly, a continuity test requires a dead circuit to prevent current from flowing through unwanted paths or damaging sensitive testing electronics.
Isolation is mandatory to prevent damage to the test instrument due to live mains voltage.
The circuit must be de-energized to ensure an accurate measurement free from external source interference.
Safety regulations (such as IS 732) mandate testing procedures on dead circuits.
Continuity tests involve checking the path of the conductor; accidental live supply can lead to instrument destruction.
Protects sensitive test instrumentation from overvoltage.
Ensures safety of the operator from electric shock.
Requires scheduled downtime as the supply must be cut.
Cannot be performed on live critical infrastructure without auxiliary isolation.
Periodic maintenance testing of electrical installations.
Verification of wiring integrity in residential and industrial buildings.
Commissioning of new electrical distribution networks.
The Megger (Insulation Tester) usually generates a high DC voltage (typically 500V DC for 230V installations).
If the main switch is left 'On', the Megger may experience reverse voltage injection, leading to internal damage.
Option A is dangerous as it risks instrument damage and operator safety; Option D is synonymous with 'On' condition regarding circuit continuity.
B is correct тАФ The main switch must be in the 'Off' condition to isolate the circuit from the power supply, protecting the operator and the test equipment.
Always remember that in industrial safety, the 'Lock-Out, Tag-Out' (LOTO) procedure is the professional extension of turning the switch 'Off' before performing any testing or maintenance.