We use the inversion algorithm which estimates the intensities and positions of the substorm current systems based on the mid-latitude magnetic field data. Using available Interplanetary Magnetic Field data, we group events according to the behaviour of IMF Bz-component and perform a superimposed epoch analysis to find the trends of dynamical behaviour of the Substorm Current Wedge (SCW) and of azimuthally symmetric ring current (DR) during substorm expansion phase. The preliminary results of studying 36 intense substorms (average maximal AE and total SCW current are about 600-800nT and 1Ma, respectively) are as follows: (1) In average, it took 16 min for the SCW total current to reach its maximal values. Little longitudinal expansion was inferred at this stage; (2) Initial longitudinal extent of the SCW changed between 1.1 and 5.5 h MLT. It was smaller for spontaneous substorms (2.0 h MLT) than for substorms triggered by the northward IMF turning (3.4 h MLT). The final width of the substorm current wedge was about 5-6 hours MLT 30min after the substorm onset in both cases. Main longitudinal expansion occured after the total SCW current reached its maximal value; (3) The Substorm Current Wedge was centered postmidnight and expanded mostly in dawnward direction in the group of triggered events; (4) we did not observe a systematic increase of symmetric ring current following immediately after strong current disruption.