Electric vehicle charging station
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Continuity measurement should be performed for protective conductors, including conductors in the main and additional equipotential. Measurement will have to be made between PE terminal of charging station’s socket and inlet PE conductor. If the charging station is equipped with cable, the measurement should be made between PE conductor of the cable plug and inlet PE conductor.
WARNING!
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Before carrying out the measurements, switch off the charging station or main power supply. |
Continuity measurement should be made with a current greater than or equal to 200 mA. The open circuit test voltage should be between 4 and 24V (AC or DC). The measuring range shall include values 0,2 Ω to 2 Ω and the maximum percentage operating uncertainty within this measuring range shall not exceed +- 30 %. The resolution of digital equipment shall be at least 0.1 Ω.
The use of instrument, with option of measuring at higher current than 200 mA increases the accuracy of the measurement. The method of measurement is shown in the figure:
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Figure 1: Continuity measurement
Continuity of the wire is considered to be met if the connection resistance does not exceed the value of 2 Ω.
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Insulation resistance, measured at a test voltage of 250 V d. c. is satisfactory if its value is not less than 1 MΩ.
Table 1: Insulation resistance measurement conditions
Nominal voltage | Test voltage | Insulation resistance |
230/400 V, up to 500 V (Applicable to all charging station from Etrel) | 250 V d. c. | ≥ 1 MΩ |
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Because the charging station has varistors installed, they may affect the measurement result or may be damaged. the test voltage for this circuit should be SET to 250 V DC. the measured insulation resistance should be at least 1 MΩ. To perform the insulation resistance test, the power supply must be disconnected. |
Explanation:
Please follow the procedure as stated in the standard IEC 60364-6, which is stating that all current-using equipment must be disconnected before the test of insulation resistance, Chapter 6.4.3.3. To perform the insulation resistance test, the power supply must be disconnected.
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The standard values of insulation resistance measurement, shown in the table below are not applicable.
Table 2: Standard values of insulation resistance measurement are not applicable
Nominal voltage [V] | Test voltage d. c. [V] | Insulation resistance [MΩ] |
SELV and PELV | 250 | 0,5 |
Up to 500 V including FELV | 500 | 1 |
Above 500 V | 1000 | 1 |
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The effectiveness of the protection measure can be considered satisfied if the trip occurs at a certain value of the leakage current and within a certain time.
Table 3: Type AC and A residual current circuit breakers without built-in overcurrent protection - normalized switching time values
Normalized tripping time values for residual current IΔn | ||||
RCD Type A | Testing current | IΔn | 2 IΔn | ≥ 5 IΔn |
General purpose | Maximum tripping times | 0.3 s | 0.15 s | 0.04 s |
Table 4: Type B RCDs - normalized tripping time values for residual currents in rectifier circuits and for smoothed residual current
Normalized tripping time values for residual current IΔn | ||||
RCD Type B | Testing current | 2 IΔn | 4 IΔn | ≥ 10 IΔn |
General purpose | Maximum tripping times | 0.3 s | 0.15 s | 0.04 s |
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ZS is the fault loop impedance,
Ia is a current that causes an automatic power cut-off within the time specified in the table below,
Uo is the rated AC or DC voltage with respect to earth.
Table 5: Maximum switch-off times
| 120 V < Uo ≤ 230V | 230 V < Uo ≤ 400V |
AC | AC | |
TN | 0,4 s | 0,2 s |
TT | 0,2 s | 0,07 s |
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RH Temporary auxiliary probe earth electrode resistance (current)
Figure 2. Measurements of the earth electrode resistance
Measurement of earth electrode resistance using a fault loop impedance test instrument (Method C2)
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It is important that the earthing conductor is reconnected to the MET of the installation before the supply is reinstated.
Earthing conductor temporarily disconnected from the main earthing terminal (MET).
Figure 3. Measurement of the earth electrode resistance using an earth fault loop impedance test instrument
Measurement of earth electrode resistance using current clamps (Method C3)
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To avoid possible risks due to currents caused by potential differences between neutral and earth, the system should be switched off during connection and disconnection. It should be noted that the values of resistance obtained using Method C3 will typically be higher than those obtained using Method C1 because of the earth loop measurement.
Figure 4. Measurement of earth electrode resistance using current clamps
2-point (dead earth) method
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