Power Management

European regulation MID related to legal metrology

As mentioned in my previous post, legal metrology is usually covered by regulations and applies to measuring instruments used in:

  • Commercial transactions (e.g. weight-price scales for retail stores, petrol pumps, water meters, electricity meters, etc.), when there is a need to protect both the buyer and the seller.
  • Operations concerning public health or safety (e.g. gas analyzers, tachographs, radar speed detectors, breathalyzers, etc.).

The Measuring Instruments Directive (MID) (2014/32/EU, which supersedes directive 2004/22/EC) is related to CE marking issued by the European Union in 2004 and enforced on 30 October 2006. As a directive, this a legal act of the European Union that requires member states to achieve a particular result without dictating the means of achieving that result. Member states have to transpose directives into national regulations, with a certain amount of leeway as to the exact requirements to be adopted.

The MID is intended to harmonize many aspects of legal metrology across all European member states and to lower barriers to trade. It covers a range of measuring instruments, as described in annexes MI-xxx:

  • MI-001: Water meters
  • MI-002: Gas meters and volume conversion devices
  • MI-003: Active electrical energy meters (i.e. this covers measurements of active energy performed by devices called electricity meters, or utility meters, or revenue meters or billing meters)
  • MI-004: Heat meters
  • MI-005: Measuring systems for the continuous and dynamic measurement of quantities of liquids other than water
  • MI-006: Automatic weighing instruments
  • MI-007: Taximeters
  • MI-008: Material measures
  • MI-009: Dimensioning systems
  • MI-010: Exhaust gas analyzers

Even beer glasses are included, with a requirement that half-pint level needs to be CE marked as showed below:

M7_1

MID essential requirements

European directives intend to provide “technology independent” requirements that are called “essential requirements”. MID essential requirements are described in Annex I of MID, and a summary is provided below:

MID conformity assessment routes

The MID covers both meter design and its manufacturing, allowing several routes as specified in Annex II. For electricity meters module B + F, or module B + D, or module H1 are allowed as described in Figure 2.

Figure 2: MID conformity assessment routes for electricity meters

Figure 2: MID conformity assessment routes for electricity meters

A usual route is to go though module B (meter type testing during design phase) and module D (meter manufacturing audit).

MID notified bodies

MID requests the conformity assessment to be performed by a test lab or an organization recognized by European authorities as a “Notified Body”. When notified, this organization is indicated by a 4 digit number.

MID marking

MID also requests the MID meter to be marked as specified below:

M7_4

Specific MID requirements for electricity meters (utility meters, revenue meters, billing meters)

Devices need to comply with MID essential requirements, but in practice MID is used in conjunction with a harmonized standard or with OIML R46 standard.

EN 50470-3 is harmonized for MID for static meters, while EN 50470-2 is harmonized for MID electromechanical meters. Both have to be used in conjunction with EN 50470-1.

 

Specific member-state requirements for electricity meters (utility meters, revenue meters, billing meters)

Some EU member states have established requirements that are unique to their respective jurisdictions. For example:

  • In Holland, MID covers only “direct connected” meters (without external sensors) up to 80A.
  • In UK, MID covers billing applications and sub-billing applications.
  • In France and in Spain, a class D (equivalent to class 0,2 of IEC standards) is specified in addition to class A, B and C.
  • Static meters need to be verified every 8 years in Germany, every 10 years in France, and every 10 to 20 years in Belgium.

Additionally, the MID covers only active energy measurement. However, some national approvals might be necessary for reactive energy measurement.

Role of WELMEC

The principal aim of WELMEC is to establish a harmonized and consistent approach to European legal metrology. A lot of WELMEC’s work is done by its Working Groups. These groups produce guidance documents which are available on this website.

WELMEC WG11 issued Guide 11.1 related to utility meters.

If you are looking for more details, you can check out the following documents:

Theme Type Link
Measurement applications White paper Guide to energy measurement applications and standards

To learn more about Schneider Electric’s range of MID compliant energy meters please visit our website. Also, for additional tools, resources and product information, please register for our dedicated Consulting Engineer portal site.


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