US Patent 9702917 Detection of and response to second leakage detection circuit

A system includes an isolation detection unit (IDU) having a first leakage detection circuit and being configured to determine an isolation characteristic for a voltage bus; and a circuit detection and response unit (CDRU) configured to determine whether the first leakage detection circuit is coupled to a second leakage detection circuit by a common ground. The CDRU can use a change in isolation characteristic of the voltage bus to determine whether a second detection circuit is coupled, and can characterize a coupled circuit. IDU operation and fault detection thresholds can be altered to mitigate confounding effects caused by simultaneous operation of both circuits. A system can be disposed at an electric vehicle to detect coupling of a detection circuit at a charging apparatus, or disposed at a charging apparatus to detect coupling of a leakage detection circuit at an electric vehicle.