Q12598 : In ROW | Creating Total Interference model, which energization type (Tower Shunt Current vs. Tower GPR) should be selected?
Answer: If the structure ground resistances modeled in SPLITS are the same as those computed by MALZ in the soil structure modeled in MALZ, then it does not matter which option is used: identical results will be obtained. On the other hand, if the two resistances are different, then one energization type will result in exaggerated earth potentials, while the other will underestimate them. For example, when the structure ground resistances used in SPLITS are smaller (sometimes much smaller) than the resistances computed by MALZ, using the Tower Shunt Current option could lead to excessive tower GPRs and earth potentials in MALZ. On the other hand, the Tower GPR option will ensure that the structure GPR in MALZ remains the same as that computed by SPLITS, which may be artificially high if the SPLITS structure ground resistances are higher than they should be (or artificially low, if the SPLITS structure ground resistances are lower than they should be), given the soil structure measured in that area. If the structure ground resistances specified in SPLITS represent an upper limit on those that are expected to be encountered in the field, then use of the Tower GPR option will result in pessimistic predictions. Also, since the structure GPR computed by SPLITS is less sensitive to structure ground resistance than the current injected into the earth, the Tower GPR energization (default in ROW) represents a more practical approach as compared with Tower Shunt Current.