Based on the focus pre-search a method is presented to measure the characteristics of the traverse focus error detection system:focus offset,focus error sensitivity and linear range.

The radial and tangential tilt angles between the emission laser axis of objective lens and test disc are the key parameters to develop,produce and detect the DVD traverses.

The result of investigation shows if that connecting small unit which had automatic disconnection to 110kV grid at the power grid terminal, there will be no more influence to the transient stability of main power grid.