The European region has high requirements for the standards and certification of electric vehicle charging piles. This article explores how to meet these standards to reduce design complexity and cost from the perspective of different leakage current standards in the European Standard IEC. By providing a detailed interpretation of mechanical coupling, electronic coupling, leakage current detection, and control circuits in the standards, this article proposes a leakage current solution that complies with the standards. We welcome readers to participate in the discussion of its feasibility and to offer valuable opinions and suggestions.

With the growing popularity of electric vehicles (EVs), the safety and compatibility of charging piles have increasingly become a focal point of attention. The European region, with its rigorous enforcement of standards, serves as a benchmark for global reference. Moreover, the presence of numerous renowned automotive manufacturers and top-tier automotive industry suppliers in Europe demonstrates the strength of its automotive industry. In the current period of strategic transformation towards new energy, the EV sector and its supporting industries in Europe have also entered a fast track.

In terms of standard interpretation, recognition, and implementation, European standards (Euro standards) enjoy high acceptance and trust globally. They are widely adopted not only by domestic products seeking to enter international markets but also by national standards, which often draw reference from Euro standards in their content. Specifically, in the detection of leakage current in charging piles, the European region typically adopts the IEC 62955 standard as the technical requirements and testing methods for residual direct current (DC) detection devices in Mode 3 charging of electric vehicles.

Figure 1: IEC 62955 8.1.2

This means that the RDC-DD module needs to be able to mechanically trigger the protective device (such as a circuit breaker or RCD) with which it is used to disconnect the circuit, as shown in Figure 2. This mechanical coupling can be achieved through mechanical coupling devices such as linkages or gears, ensuring that the circuit is quickly disconnected when the direct current residual current exceeds the set value, thereby protecting the electric vehicle charging system. However, the design requirements for this mechanical coupling disconnection function will significantly increase the complexity and cost of the design.

Figure 2: IEC 62955 ANNEX L L.2

The standard also proposes an electronic coupling method, which controls the circuit-breaking mechanism through electrical signals. In this case, the product needs to be equipped with a Type A RCD module to ensure that the circuit is quickly disconnected when the direct current residual current exceeds 6 mA, thereby protecting the electric vehicle charging system. However, compared with circuit breakers and relays, the cost of Type A residual current devices (RCDs) is still relatively high.

But the standard allows for Type A protection in the form of a CT (current transformer) + circuit breaker or relay configuration, which can also be considered a solution for Type A residual current protection, namely the RDC-M-module + circuit breaker or relay solution.

The RDC-M-module + relay solution can serve as a simplified design and cost-reducing option, and it is also an ideal solution. However, according to the certification description, this design still requires a Type A RCD module. To reduce costs, charging pile manufacturers will specify in their technical specifications that an additional Type A RCD must be installed on the distribution side in accordance with local regulations, as shown in Figure 3.

Figure 3: Specification Sheet of a European Domestic Charging Pile Manufacturer

It is not difficult to understand, through interpreting the standards, the considerations of the standard setters regarding reliability based on mechanical coupling methods, as well as their thoughts on the safety assurance of manual power disconnection and reset. Strictly speaking, the basic safety protection provided by Type A RCDs is irreplaceable and must be equipped with a DC 6 mA detection function to prevent the residual current device from becoming “blind” and to provide additional protection.

Within the IEC standard system, there is also the IEC 60947-2:2024 standard, which covers the requirements for low-voltage switchgear and control circuits. In particular, Annex M (ANNEX-M) provides a detailed description of the relevant specifications for residual current tripping control devices. Although this section comprehensively stipulates the technical requirements for residual current, it does not explicitly specify the details of the coupling methods.

Figure 4：IEC 60947-2 ANNEX M connection type

In IEC 60947-2:2024 ANNEX-M, Section M3 describes the connection forms but does not specify the coupling methods. This implies that both electronic and mechanical coupling methods are acceptable. Therefore, during the design process, it is possible to choose the electronic coupling method, which has a lower design complexity.

To ensure the safety of the coupling, Section M.8.9 sets specific requirements for the verification of connection mode failures, as shown in Figures 5 and 6. This involves checking whether the RCD can detect abnormal connections in the circuit. This verification, similar to a self-check function, can assess the functionality of the coupling to ensure that during the electric vehicle charging process, the power supply can be quickly and reliably cut off once an abnormal direct current residual current is detected.

Figure 5：IEC 60947-2 ANNEX M M.18 failure test circuit

Figure 6：IEC 60947-2 ANNEX M.8.9 failure test

From the perspective of coupling methods, the issue of design complexity has been addressed. The next considerations will be the technical requirements and testing methods for leakage current. In the field of leakage current detection for charging piles, the IEC 61008 + IEC 62955 standard is commonly adopted, which is referred to as the "A+6" testing standard. However, this requirement is not explicitly stated in IEC 60947-2:2024. In ANNEX-M, which describes the MRCD module, the requirements for leakage current functions cover three categories: TYPE A, AC, and B, as shown in Figure 7. For charging piles, the standard that should be applied is TYPE B.

Figure 7：IEC 60947-2 ANNEX M M.3.5 function type

For the testing of TYPE B, ANNEX-M does not refer to any other standards. However, there is an independent description of the TYPE B test in ANNEX-B.4.4.3. Although it is not explicitly referenced, by comparing the test clauses, it can be observed that the test items are identical to those described in IEC 62423:2009, as shown in Figures 8 and 9.

Figure 8：IEC 62423 3.2 Type B test method

Figure 9：IEC 60947-2 ANNEX B B.4.4.3 Type B test method

The European region enforces strict standards for electric vehicle charging piles. However, by thoroughly understanding the IEC 62955 and IEC 60947-2 standards, can a solution that simultaneously addresses standard compliance, design complexity, and cost control be achieved by adopting the IEC 60947-2 standard for Type B leakage current detection, thereby circumventing the stringent requirements of certification bodies and reducing design costs? The feasibility of this solution awaits discussion among readers.

Adopting the IEC 60947-2 standard does not mean compromising safety. Instead, it provides greater design flexibility while ensuring safety. This flexibility can help customers quickly adapt to market changes and meet the needs of different regions and a wider range of application scenarios. Magtron’s high-performance, low-zero-drift, and high-bandwidth leakage current sensors, developed using its proprietary iFluxgate technology, can meet the requirements for accurate leakage current detection and integrate Type B functionality. The company’s self-developed SoC chip also offers proprietary technical solutions for customers. Based on the latest market demands, it continuously upgrades and improves to address various current and leakage current collection issues in industries such as industrial manufacturing, electric vehicles, and energy storage, safeguarding electrical equipment across these sectors.

[1] IEC 62955. Residual direct current detecting device (RDC-DD) to be used for mode 3 charging of electric vehicles International Electrotechnical Commission, Geneva, Switzerland.

[2] IEC 60947-2. Low-voltage switchgear and controlgear –Part 2: Circuit-breakers International Electrotechnical Commission, Geneva, Switzerland.

[3] IEC 62423. Type F and type B residual current operated circuit-breakers with and without integral overcurrent protection for household and similar uses. International Electrotechnical Commission, Geneva,Switzerland.

Writer：Bobby Guo