Testing Electric Vehicle Supply Equipment (EVSE)

It is clear that EVSEs must be tested immediately after installation to ensure that they operate safely and deliver the required performance. Testing will also be needed to aid fault finding when problems are reported. What may be less clear is that periodic testing is also important. 

EVSEs frequently operate in outdoor environments where they are subject to large temperature variations and are exposed to rain, wind and snow. This increases the risk of faults developing and makes regular testing highly desirable to guard against declining performance or the development of safety hazards. In most cases, routine tests will not need to be as detailed as initial post-installation tests, which means that, with suitable equipment, they can be carried out quickly and easily. Nevertheless, procedures for routine EVSE testing must always include basic safety tests.
 

Routine testing

Depending on the installation, the tests performed during routine testing of an EVSE should, as a minimum, include those listed below. This is not an exhaustive list; additional tests may be required in some circumstances.

• Visual inspection. Particular attention should be given to the condition of connectors and connecting cables.
• Protective earth test. This checks for open circuit ground connection or voltage present on the ground connection. 
• Protective conductor resistance measurement. This confirms that any metalwork on a Class I EVSE (an EVSE that doesn’t use double-insulated construction) is connected to the EVSE ground.
• Touch voltage measurement. This checks to ensure that the earth voltage of the charger will not rise to a dangerous level in fault conditions.
• Earth fault tripping time test. This checks that, in fault conditions, the protection device(s) – RCD/GFCI and/or RDC-DD – operate quickly enough to protect the user.

All of the preceding tests are safety tests. If the EVSE fails any of these tests, testing must be stopped, and the EVSE must be taken out of service until the reason for the failure has been located and remedied. When the safety tests have been successfully completed, the following tests can be carried out:

• Earth fault trip current measurement. This test looks primarily for unduly sensitive protection, which is likely to result in nuisance tripping.
• Proximity pilot (PP) check. This checks the operation of the connector latch and the proximity detection system, which prevents the vehicle from being driven away while charging is in progress.
• Control pilot (CP) check. This test simulates the EV CP states A, B, C, D, E and F. (See ‘Controlling the charging process’ earlier in this document). The tester then reads back the state from the EV to confirm that it is responding correctly. The CP check also displays the maximum current the EVSE is making available to the EV.

These tests can be carried out quickly and conveniently with a dedicated EVSE checker, such as the Megger EVCC300. However, it is important to be sure that the device provides the full suite of tests listed above, including, in particular, all of the safety tests.

Certification testing

While the tests listed above meet the requirements for routine in-service testing of EVSEs, they are not sufficient for certification testing of newly installed EVSEs. For this, additional tests are needed. These include earth loop impedance testing, insulation resistance testing, measurement of tripping time for protective devices and determination of voltage drop in conductors. 

The tests are similar to those required for the certification of any electrical installation and are most conveniently carried out with a multifunction installation tester (MFT) such as the Megger MFT-X1. When the MFT is used with a suitable adaptor, like the EVCA201, it can also carry out the tests listed above under the heading of ‘routine testing’. The combination of an MFT plus adaptor, therefore, offers a complete solution for EVSE testing.