What could cause an impressed current system to show normal DC voltage but zero current output?

The scenario where an impressed current system shows normal DC voltage yet has zero current output can indeed be attributed to a broken cable to the anodes. In an impressed current cathodic protection system, the anodes are essential for delivering the protective current needed to mitigate corrosion. If there is a break in the cable connecting the rectifier to the anodes, even if the rectifier is functioning correctly and producing the appropriate voltage, that voltage will not translate into current flow because the electrical circuit is incomplete. This disconnection means that while the system appears to have the necessary voltage, the absence of a current flow indicates a failure in delivering that current to the area needing protection.

In contrast, a faulty transformer would typically result in inadequate voltage being provided, while the absence of an AC supply would imply that the rectifier isn't functioning, which would show a lack of both voltage and current. Faulty rectifying elements can cause a lack of proper conversion from AC to DC, leading to insufficient voltage or current. Thus, the presence of normal DC voltage coupled with zero current output points specifically to an issue with the connection to the anodes, such as a broken cable.