Insulation Monitoring
Insulation monitoring is the continuous or periodic assessment of electrical isolation between an EV's high-voltage circuit and its conductive chassis or body.
What it detects
The traction system is normally isolated from the vehicle body. Reduced isolation resistance can indicate damaged cable or component insulation, water or coolant intrusion, conductive contamination, or a fault inside the battery, inverter, motor, charger, or other high-voltage equipment.
The vehicle can use the result to warn the driver, prevent high-voltage startup, stop charging, or disconnect external high-voltage equipment, depending on the fault and system design. Insulation monitoring does not check whether a connector or service cover is physically closed; that is the role of the High-Voltage Interlock Loop (HVIL).
For the wider electrical-safety context, see EV Battery Safety and Failure Management.