A mathematical model appropriate for the calculation of transient neutral currents, when a single circuit three-phase transmission line is switched on, is presented. The practical condition or sequential pole switching of multi-switch circuit breakers is considered. The analysts is based on the Laplace transform concept, while the convolution theorem is used for the determination of original and deduced Laplace transforms. The earth return effect is accounted for which makes the line parameters frequency dependent. The proposed concept is applied successfully to the calculation of transient neutral currents at the sending end of a typical 500 kV, 500 km transmission line. The results obtained indicate that, in such cases, special protection should be considered.