How does the high-voltage isolation monitoring system work in EVs?

Isolation monitoring detects degradation of electrical insulation between HV system and chassis ground, preventing shock hazards. Methods include: Symmetric pulse injection measuring voltage response to detect resistance to ground, asymmetric injection detecting fault location (positive or negative side), and continuous monitoring during operation. ISO 6469 requires isolation resistance >100 ohms/V (typically >500 kohms for 400V system). The system must distinguish true faults from capacitive coupling, EMI, and moisture effects. Detection triggers warning/shutdown, with diagnostic codes identifying fault location for service.