sentences:  Failing insulation is essentially a high impedance fault which will allow current to flow through any available path to ground, a condition which can cause shocks or fires if left unmitigated.This leakage can occur when there is damage caused by physical, thermal, or chemical stresses to insulation on power lines, especially but not limited to underground or underwater cables.Examples of this damage are swollen or cracked insulation from overheating, abrasions caused by digging or ground seizing, and corrosion damage from salt or oil exposure.