A dielectric medium placed between conductors of different potentials, or between a conductor and ground, to confine the electric current to its intended path. In power systems, this ranges from solid polymers on cables to insulating oil in transformers and pressurized sulfur hexafluoride gas in switchgear. Its primary function is to withstand operating voltages and transient overvoltages without breaking down.
The megger test showed that the insulation on the B phase cable has degraded significantly since the last maintenance outage.
Related terms
Insulation coordination
Sizing insulation and surge arresters together so any flashover lands at a cheap, self-restoring point, not inside plant.
Insulation resistance test
DC test that applies a high voltage between conductors and earth and reads leakage resistance in megohms.
Creepage distance
Shortest route over an insulating surface from one conductive part to another, the dimension that resists tracking.
Clearance
Straight-line air gap between two conductive parts, the dimension that decides whether a surge can flash across.