Q. What is the allowable megohm level at 500v AC for the DSX fixture family to megger the cable?
A. The megger or IR test is performed with a DC voltage, not AC. The resultant resistance reading should be quite large from a phase lead to ground on a single fixture, > 10 Meg at least or much more to tens or hundreds of megs, but I don’t know the exact value. 500 VDC is the maximum test voltage that could be used with our 480V fixture from a phase to ground, as a 750VDC or 1000VDC value will cause the MOV in the SPD to conduct.
500 VDC will more than likely power up the fixture (or try to) if they apply the voltage across the input leads of the fixture (driver), which won’t be a good megger result. Also, long runs of cable to the fixtures from the test point will introduce additional capacitance, which too will alter the results. (response provided by VP of outdoor electronic luminaires)