After seeing the post about the giant MP3-Player LED display panel Dave left a comment about this one.
Thanks Dave.

“Construction uses 1.6mm diameter tinned copper wire for the ground and +5V connections to the modules (ground connections run horizontally and vertically, +5V connections run horizontally). The vertical ground connections up the vertical leg of the T are 12 1.6mm diameter tinned copper wires. The horizontal power connectors are connected vertically by 4 1.6mm diameter tinned copper wires insulated with heat-resistant sleeving (yellow and red in the picture). They are connected in 4 banks and will be supplied by 4 300W standard PC power supplies. The power will be socketed to the T from the base, so 4 2mm-squared cross-section multi-core insulated cable is used to connect each bank to the sockets in the base. The idea of all the large amount of cross section of copper wire is to minimise the voltage drop across the cabling (the total peak current consumption of the array will be 100A at +5V). Signal wire and ribbon cable are used for the data connections. In the base of the T is a small circuit board containing 74LS374 latches for buffering the parallel port after the 5m length printer cable, and generating the chip select and clock signals for the LED module array. ”