How can I simulate a circuit in Electric?

RCDs operate by measuring the current balance between two conductors using a differential current transformer, and opening the device's contacts if there is a balance fault (i.e. a difference in current between the phase conductor and the neutral conductor). More generally (single phase, three phase, etc.) RCDs operate by detecting a nonzero sum of currents, i.e. the current in the "hot" or "hots" plus that in the "neutral" must equal zero (within some small tolerance), otherwise there is a leakage of current to somewhere else (to ground, or to another circuit, etc.). The National Electrical Code, which is the enforcable code in most of the United States, requires GFCI devices for personnel to interrupt the circuit if the leakage current exceeds a range of 4 to 6 milliamps of current (the exact trip setting can be chosen by the manufacturer of the device and is typically 5 milliamps) within 25 milliseconds. GFCI devices which protect equipment (not personnel) are allowed to trip as high as 30 milliamps of current.