Design of sacrificial anode cathodic protection systems sometimes involves use of an array of anodes mounted on a sled, which is connected to the structure by cable to provide a return path. Two factors can limit the effectiveness of sled-mounted anode arrays: firstly the IR drop along the return path cable can significantly reduce the driving potential; secondly close proximity of anodes can reduce the output of the array to well below what would be expected if the anodes were well separated.

The effect of IR drop can easily be estimated using known cable resistance and anticipated current.

However with respect to anode output, available data for resistance to ground is limited to fairly simple groupings of anodes. For a complex anode sled design it is only practically possible to determine the theoretical maximum output by use of mathematical modelling performed using computer-based simulation techniques.

First, accuracy of the simulation method is established by comparison with exact analytical methods and approximate formulas used by industry.

Secondly, accuracy is assessed of approximate formulas when applied to anode geometries different from those for which the formulas were derived.

Finally, resistance to ground is determined for three different sled designs.

Key words: anode, resistance to ground, analytic, approximate, simulation, sled, interference ratio

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