Document ID: chunk:federal_register_of_legislation:F2023L01526:body:0:p18
Version: federal_register_of_legislation:F2023L01526
Segment Type: other
Provision Reference: 
Character Range: 50938–54062

minimum value of 100 Ω/volt of the working voltage for DC buses, and a minimum value of 500 Ω/volt of the working voltage for AC buses.
         The measurement shall be conducted according to Annex 5A "Isolation resistance measurement method for vehicle based tests".
         5.1.3.2. Electric power train consisting of combined DC- and AC-buses
         If AC high voltage buses and DC high voltage buses are galvanically connected, isolation resistance between the high voltage bus and the electrical chassis shall have a minimum value of 500 Ω/volt of the working voltage.
         However, if all AC high voltage buses are protected by one of the two following measures, isolation resistance between the high voltage bus and the electrical chassis shall have a minimum value of 100 Ω/V of the working voltage:
              (a) At least two or more layers of solid insulators, electrical protection barriers or enclosures that meet the requirement in paragraph 5.1.1. independently, for example wiring harness;
              (b) Mechanically robust protections that have sufficient durability over vehicle service life such as motor housings, electronic converter cases or connectors;
         The isolation resistance between the high voltage bus and the electrical chassis may be demonstrated by calculation, measurement or a combination of both.
         The measurement shall be conducted according to Annex 5A "Isolation resistance measurement method for vehicle based tests".
         5.1.3.3. Fuel cell vehicles
         In fuel cell vehicles, DC high voltage buses shall have an on-board isolation resistance monitoring system together with a warning to the driver if the isolation resistance drops below the minimum required value of 100 Ω/V. The function of the on-board isolation resistance monitoring system shall be confirmed as described in Annex 6.
         The isolation resistance between the high voltage bus of the coupling system for charging the REESS, which is not energized in conditions other than that during the charging of the REESS, and the electrical chassis need not to be monitored.
         5.1.3.4. Isolation resistance requirement for the coupling system for charging the REESS
         For the vehicle conductive connection device intended to be conductively connected to the grounded external AC power supply and the electrical circuit that is galvanically connected to the vehicle conductive connection device during charging of the REESS, the isolation resistance between the high voltage bus and the electrical chassis shall comply with the requirements of paragraph 5.1.3.1. when the conductive connection is disconnected and the isolation resistance is measured at the high voltage live parts (contacts) of the vehicle conductive connection device. During the measurement, the REESS may be disconnected.
         5.1.4. Protection against water effects.
         The vehicles shall maintain isolation resistance after exposure to water (e.g. washing, driving through standing water). This paragraph shall not apply to electrical circuits that are galvanically connected to each