Q277 : Touch Voltages Around Disconnected Structures in MALZ
Question When I plot the touch voltage above a system consisting of several disconnected grids, I get very sharp variations in the plotted values. What is wrong?
Answer When computing touch voltages, the program needs to use a GPR as a reference voltage. When using the "Nearest Conductor" method, for instance, the program takes the GPR of the segment that is closest to the computation point as a reference.
When a grounding structure consists of several disconnected pieces, the different pieces are normally at different potential. The program may use the potential of different pieces of the structure as a reference when computing the touch voltage for different computation points. This can lead to apparently wild variations in touch voltages when the touch voltage at one observation point is computed using the potential of one piece of the structure as a reference and the touch voltage at a neighboring point is computed using the potential of a different piece of the structure as a reference. The boundaries delimiting the "zone of influence" of the disconnected pieces of the structure can normally easily be seen on a spot plot or a contour plot.