25 Aug NMi Decides to Apply MID for DC Meters
NMi Decides to Apply MID for DC Meters
25 August 2022
Since its introduction in 2006, the MID has been applied in the European member states to certify AC electricity meters. As one of the leading Notified Bodies, NMi has issued many module B type approvals and module D certificates in this area.
However, due to new developments related to EV Charging, especially for fast chargers, manufacturers now increasingly use DC electricity meters. According to the traditional view, the MID does not cover DC meters. However, this view has changed. The most recent step in this evolution is the decision of the NMi Certification Board to issue MID approvals for DC meters.
DC electricity meters under the MID
In recent years several significant changes occurred. First, IEC TC 13 published a dedicated standard for DC meters, the 62053-41 . This document is used in conjunction with the updated 62052-11 standard . In practice, this document is a breakthrough because it provides specific requirements for DC applications by filling the gap of missing requirements so far.
Another development was the CENELEC TC 13 initiative to work on a new standard EN 50470-4 for DC meters. This standard would be used in conjunction with the EN 62052-11, a nearly identical copy of its IEC variant. Work on the new standard is still in progress. The documents are intended for use as part of harmonised standards under the MID.
Additionally, the German document VDE-AR-E 2418-3-100 , with its specific Annex A for DC meters, provides means to assess DC meters. In this standard, the MID philosophy is also implemented, with Annexe V’s requirements.
Intensively debated within organisations like WELMEC, the idea has grown as well that the MID, with its instrument specific Annex V, could be allowed for DC meters as well. Advocated in large part by the work of LegalEVcharge, the following arguments promote increased acceptance:
- The MID describes meters for ‘active electrical energy’. Fundamentally this covers both AC and DC electricity meters.
- As laid down in Annex V, instrument-specific requirements can be fulfilled for both types of meters.
- The fact that via Mandate M/541, European standardisation committees were requested to create standards for DC meters for legal metrological applications is also a clear sign that the European Commission wants to apply the MID for the use of DC meters.
NMi Certification Board decision
Based on the reasoning mentioned above, as well as the increased availability of dedicated standards for DC meters, the Certification Body of NMi recently took the decision to issue MID approvals for DC meters. The use of the MID for DC meters can be considered a breakthrough on the European level, also for the use in EV Charging Systems.
The recent decision provides that if a DC electricity meter fulfils the VDE-AR-E 2418-3-100, based on the harmonised standards EN 50470-1/-3, 61000-4-19 and WELMEC 7.2, the essential requirements of the MID are deemed to be fulfilled. On this basis, NMi can issue an MID approval for these measuring instruments.
NMi is accredited for the VDE-AR-E 2418-3-100 (ISO 17025 & 17065), as well as for the EN 50470-1/-3, 61000-4-19 and WELMEC 7.2 (ISO 17025 & 17020). Furthermore, the upcoming EN 62052-11 in conjunction with the EN 50470-4 is deemed sufficient to act as harmonised standard under the MID.
Find out more about standards for DC active electrical energy meters and the current state of legal requirements for EV charging systems in the recently updated NMi EV whitepaper.
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