Partial shade is known to cause significant de-rating for most photovoltaic (PV) systems. However, the specific de-rating due to partial shade from differently shaped objects like overhead wires is not well known. We present current-voltage (I-V) curves from three different strings containing 4 to 9 PV modules while applying various types of partial shade, including shade from electrical cables in front of the modules. We show that a 1-kW string of nine poly-Silicon modules manufactured by Sharp can have a power loss of 13% due to shading just 1% of its surface area. We verify that blocking columns of cells in a module has less impact on power loss than blocking rows. This demonstrates how the non-linear response to partial shade can depend on the placement of bypass diodes that isolate different sub-strings within each module. Furthermore, we quantify the reduction in power and I-V parameters caused by shade from wires (or PVC pipes in our experiments). © 2012 IEEE.