UL 2231-1:2021 PDF Download

UL 2231-1:2021 is a standard that specifies the general requirements for personnel protection systems used in electric vehicle supply circuits. The purpose of this standard is to reduce the risk of electric shock to users when accessing parts of the electric vehicle during charging.

The devices and systems covered by this standard are designed to be compatible with charging systems and vehicles, and they are rated accordingly. The standard ensures that the charging system, the vehicle, or both, meet the required features contained in sections 3-5 for compatibility.

The standard applies to vehicles that have provisions for equipment grounding conductors during battery charging, ground-monitoring conductors, reinforced or double insulation, or no direct connection between current-carrying conductors and the vehicle chassis. It also covers devices and systems where the grounding path impedance of the charging system to the vehicle is less than or equal to the impedance of the ungrounded conductor or conductors, and where a continuous current less than 70 mA RMS is available from any accessible part of the charging system.

The devices covered by this standard are intended to interrupt the electric circuit to the load in various fault scenarios, such as when the fault current to ground exceeds a predetermined value, when the grounding path becomes open-circuited or has an excessively high impedance, or when a path to ground is detected on an isolated (ungrounded) system.

The standard also specifies the application of these devices and systems on electrical systems that are either end-grounded, centrally grounded, or isolated (ungrounded), depending on the operating voltage. It further outlines the investigation criteria for charging circuit-interrupting devices based on the type of current and voltage present in the circuit to be protected.

It is worth noting that this standard does not cover ground-fault circuit-interrupters (GFCIs) intended for use as personnel protection on specific grounded circuits, as they are addressed separately in Annex A, Ref. No. 2 of the standard.