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6mA DC Protection to IEC 62955

Overview

PlugStream 7S and PlugStream 7T include built-in protection intended to trip the output when a residual direct current (DC) of 6 mA is detected. The final installation still requires the Type A residual-current and overcurrent protection specified by the installation design.

IEC 62955 defines requirements for residual direct current detecting devices used with EV charging equipment. The exact standard edition, product test report, hardware revision, and scope must be confirmed from the controlled conformity pack before this support article is used as certification evidence.

Standard Requirements

IEC 62955 requires that the RDC-DD protection is tested under two conditions:

  • Sudden appearance of DC (Clause 9.9.2.1)
  • Gradual (ramped) increase of a smooth DC component (Clause 9.9.2.2)

Ambiguity in Testing

The requirements for the ramped DC test are not precisely defined.
As a result, test instruments from different manufacturers may produce different outcomes when evaluating the same device.

This inconsistency has led to updates in test equipment — for example, Metrel (a leading manufacturer of electrical test devices) issued a software update to ensure more consistent results when testing RDC-DDs.

Key Takeaway

Use a suitable EV chargepoint tester with current firmware/software and follow the equipment manufacturer's procedure. Test both sudden and ramped DC behaviour where required by the commissioning method. Record the tester, firmware version, result, and product serial number in the installation evidence.

Do not omit the upstream Type A protection on the basis of the built-in 6 mA DC function. If the result is inconsistent, stop commissioning and contact PlugStream Support rather than repeatedly energising the output.