The error amount caused from cathode cable can be calculated as follows;
Erroneous measurement is caused by the voltage drop over the cathode cable,
This voltage will be:
V(cathode) = I(cathode) * R(cathode)
I(cathode) current can be read out from the display while the system is operating.
Cathode cable resistance can be calculated by the formula
R(cathode) = Cable length / (56 * Cable cross section)
I(cathode) = 10 A
Cathode cable length = 50 m
Cathode cable cross section = 25 mm²
R(cathode) = 50m / (56 *25 mm²) = 0,0357 Ohm and
V(cathode) = 10 A * 0,0357 Ohm = 0,357 V
This erroneous measurement voltage is added to the value read out from display.
In this case a separate measurement cabling for reference electrode is inevitable.
If we consider system current to be 0.1 A, erroneous voltage will be;
V(cathode) = 0,1 A * 0,0357 ohm = 0,00357 V (3,57 mV)
This value is too low. In this case there may be no need for second measurement cabling in terms of erroneous measurement.
It is strongly recommended that a separate cathode cable for measurement purpose to be installed in new systems. This measurement cable’s cross-sectional area has not great importance but it is foreseen that according to its place of use or length of the line, cables with 6mm² or thicker cross-sectional area are to be proper for mechanical robustness.