Voltage drop warnings will appear when the voltage drop between the Main Supply and a downstream circuit exceeds the voltage drop limit. To correct the problem, reconsider the cable sizes of the offending circuit, or the cable sizes of circuits upstream from it. Values that affect the voltage drop calculation are the design current (Ib), the circuit length and the cable size. The power factor and other correction factors such as circuit grouping and ambient temperature also take part in the voltage drop calculation. Note that you can change the voltage drop limit for each circuit under the Volt drop tab in the circuit editor.

See the Voltage drop calculations

To examine the voltage drop calculations go to the Volt drop tab at the properties area as shown below: