Complex sentence: Increasing the tension in the line and adopting more rigid insulator attachments have the effect of reducing galloping motion but are costly, often impractical after the line has been constructed, and can increase the tendency for the line to instead exhibit high frequency oscillations.
Split into simpler sentences: Increasing the tension in the line and adopting more rigid insulator attachments have the effect of reducing galloping motion. However these measures can be costly, are often impractical after the line has been constructed, and can increase the tendency for the line to instead exhibit high frequency oscillations.