Document ID: chunk:federal_register_of_legislation:F2023L01529:body:0:p30
Version: federal_register_of_legislation:F2023L01529
Segment Type: other
Provision Reference: 
Character Range: 83813–86848

or Ri = Ro*Vb*(1/V2' – 1/V2)

       Figure 3
       Measurement of V2'

       2.2.3.5. Fifth step

        The electrical isolation value Ri (in Ω) divided by the working voltage of the high voltage bus (in volts) results in the isolation resistance (in Ω/V).

        Note: The standard known resistance Ro (in Ω) should be the value of the minimum required isolation resistance (in Ω/V) multiplied by the working voltage of the vehicle plus/minus 20 per cent (in volts). Ro is not required to be precisely this value since the equations are valid for any Ro; however, a Ro value in this range should provide good resolution for the voltage measurements.

Annex 4B

Isolation resistance measurement method for component based tests of a REESS

       1. Measurement method

        The isolation resistance measurement shall be conducted by selecting an appropriate measurement method from among those listed in paragraphs 1.1. through 1.2. of this annex, depending on the electrical charge of the live parts or the isolation resistance, etc.

        If the operating voltage of the tested-device (Vb, Figure 1) cannot be measured (e.g. due to disconnection of the electric circuit caused by main contactors or fuse operation) the test may be performed with a modified test device to allow measurement of the internal voltages (upstream the main contactors).

        These modifications shall not influence the test results.

        The range of the electrical circuit to be measured shall be clarified in advance, using electrical circuit diagrams, etc. If the high voltage buses are galvanically isolated from each other, isolation resistance shall be measured for each electrical circuit.

        Moreover, modification necessary for measuring the isolation resistance may be carried out, such as removal of the cover in order to reach the live parts, drawing of measurement lines, change in software, etc.

        In cases where the measured values are not stable due to the operation of the isolation resistance monitoring system, etc., necessary modification for conducting the measurement may be carried out, such as stopping the operation of the device concerned or removing it. Furthermore, when the device is removed, it shall be proven, using drawings, etc., that it will not change the isolation resistance between the live parts and the ground connection designated by the manufacturer as a point to be connected to the electrical chassis when installed on the vehicle.

        Utmost care shall be exercised as to short circuit, electric shock, etc., for this confirmation might require direct operations of the high-voltage circuit.

       1.1. Measurement method using voltage from external sources

       1.1.1. Measurement instrument

        An isolation resistance test instrument capable of applying a DC voltage higher than the nominal voltage of the tested-device shall be used.

       1.1.2. Measurement method

        An insulation resistance test instrument shall be connected between the live