Which testing method is conducted to ensure that RCDs operate correctly on current leakage to earth?

The correct testing method to ensure that Residual Current Devices (RCDs) operate correctly on current leakage to earth is the Earth fault loop impedance testing. This method assesses the impedance of the earth fault loop and ensures that the RCD will correctly detect any leakage current and disconnect the faulty circuit in a timely manner to protect against electric shock hazards.

Earth fault loop impedance testing involves verifying the effectiveness of the earthing system and measuring the impedance of the path that fault current would take in the event of an earth fault. If the impedance is too high, the RCD may not trip effectively, making it crucial to test this aspect to ensure safety.

Insulation resistance testing evaluates the integrity of the insulation of electrical installations but does not specifically test the operation of RCDs regarding leakage currents. Continuity testing primarily checks that conductors are continuous and properly connected, and while important, it does not measure current leakage or RCD performance. Voltage drop testing assesses voltage loss along conductors under load but does not provide insights into RCD functionality concerning earth leakage. Thus, for verifying RCDs, earth fault loop impedance testing is the key method to ensure their proper operation in protecting against leakages to earth.