Insulating plates are sometimes used in an attempt to increase the robustness of the load cells against damage by isolating the load cell from its surrounding environment. Unfortunately such means are limited in effectiveness. The lightning strike is essentially a constant current source with an open circuit voltage that can exceed many millions of volts. It is relatively easy for lightning to flash over such insulation plates in order to find a path to ground.
Consider also that during most lightning storms the plates will be wet or exposed to high humidity, and over the passage of time, pollutants will affect the insulation. Insulating plates may afford some false sense of security in case of a smaller lightning strike but will not protect in the case of large lightning strikes. With a correctly installed surge protection system, insulating plates are not required and greater system reliability can be provided against a wider range of threats by bonding the load cell to its local ground.