Cathodic Protection Help Information
for
LORESCO Vertical Resistance Calculator

Data Input
Note: Do not use commas in the input values. If the decimal is not entered, it is assumed to be just to the right of the right-most digit entered.

English Units or Metric Units: You may choose Metric or English input units by use of the input unit selection button prior to entering variables. For example if you wish to enter variables in English units and English units (ft & in) appear next to the input variable entry slots, simply enter the proper numbers and continue. However, if you wish to enter the variables in English units and Metric units (m & cm) appear next to the input variable entry slots, left click the mouse on the "English Units" button. Note: the required units for Resistivity are ohm-cm regardless of the input units selection.

Environment Resistivity, (ohm-cm): Enter the average resistivity of the environment (earth) around the electrode (anode) in ohm-cm. This is the soil resistivity value determined through field testing. Soil resistivities may vary from a low of 100 to a high of 1,000,000 ohm-cm. Regardless of the input units selected, the units for resistivity must be in ohm-cm.

Length of single electrode column, (m or ft): Enter the length of a single electrode column in meters or feet. This is the length of the LORESCO carbon backfill column.

Number of electrodes: Enter the total number of LORESCO carbon columns. Regardless of the number of anodes installed in a single carbon column, this is considered one electrode.

Diameter of electrode columns, (cm or in): Enter the diameter of a single electrode column in centimeters or inches. This is the diameter of the LORESCO carbon backfill column.

Spacing between columns, (m or ft): Enter the center-to-center spacing in meters between individual LORESCO carbon columns in meters or feet. Typical spacings between surface electrodes vary between 1.5 to 10 meters (5 to 30 feet). Typical spacings between deep electrode systems vary between 7 to 30 meters (25 to 100 feet).

If the number of electrodes entered is one, no spacing value is required. If a value for spacing is entered with the number of electrodes equal to one, the spacing is ignored.

Deep or shallow: Select one of the two choices from the drop-down menu. Surface electrodes (anodes) generally are installed with the top of the active electrode within 15 meters (50 feet) from the surface. Deep electrodes are generally installed with the top of the active electrode below 15 meters (50 feet) from the surface.

Result: This is the resistance-to-earth in ohms of the electrode system described by the input data. In the case of a cathodic protection system, this is not the total circuit resistance seen by the rectifier. The total circuit resistance is the resistance-to-earth of the electrode system plus the resistance-to-earth of the protected structure, the interconnecting cable resistance, and any internal power supply resistance.

The most recent result along with the input data is displayed in output column 1. You may recalculate by reentering the required variables while changing any or all of the input values for the next calculation. As additional calculations are undertaken, the output results automatically scroll to the right. In other words, at any time you may compare the three most recent calculation results.

General Information

This calculator employs the surface and deep electrode (anode) equations developed by Erling D. Sunde and found in his book Earth conduction Effects in Transmission Systems. In the case of multiple electrode systems, correction for the mutual interference between the electrodes is accomplished using the general formula developed by Sunde. These equations apply to equally spaced, vertical electrodes placed along a straight line. Development of the equations assumed a homogeneous electrolyte with a single resistivity. The equations ignore any attenuation effects along the LORESCO column.

These calculations do not take into account the contact resistance between each anode and the LORESCO carbon backfill. However, the contact resistance between each electrode is small, being on the order of a few tenths of an ohm or less. Since all of the electrodes in a cathodic protection system are in parallel, the total contact resistance is the contact resistance for one electrode divided by the total number of electrodes. Therefore, for practical cases this contact resistance is negligible and may be ignored.