VDE application rules
2018-04-12 page

Technical Connection Rules explained

With its Technical Connection Rules (TCR), VDE FNN provides an important basis for the success of the energy revolution. It signifies the secure integration of renewable energies to the grid, grid interoperability, as well as investment and planning security.

The most important facts

  • The TCR outline the essential requirements for the connection of customer systems to the public utility grid.
  • Provide important information for the operation of equipment
  • Determine the duties of the grid operator, plant operator, planner and customer
  • FNN is currently revising all four TCR (one per voltage level)
  • The main focus of the revision is the implementation of the European Network Codes

Need for technical connection rules

Because of changes caused by the energy revolution, supplying power is becoming more complex. This change is particularly noticeable in the number of customer systems on the power grid. Thanks to the numerous, often small, renewable energy plants, significantly more plants are connected to the grid than before. In contrast to large, conventional power plants, many of these smaller ones are connected to low and medium voltage grids. As the number of plants increases and the new challenges for lower network levels grow, it has become essential to implement requirements on customer systems that are uniform nationwide.

According to § 19 Energy Industry Law (EnWG), operators of electricity supply grids are obliged to set minimum technical requirements for the design and operation of customer systems, taking into account the conditions laid down in § 17 EnWG (for the grid connection of generating plants, electricity distribution networks, directly connected customers’ equipment, connecting cables, and direct lines), and publish them on the Internet.

The minimum technical requirements must ensure grid interoperability and be objective and non-discriminatory. The minimum requirements are to be shared with regulatory authorities.

Modernizing regulations with VDE|FNN

VDE FNN is currently updating and aligning all existing regulations for the different voltage levels. At the moment, for each voltage level there are different guidelines from several associations. In the future, there will be only one long-term document per voltage level. In interdisciplinary project groups VDE FNN is developing Technical Connection Rules for each voltage level. In addition to the regulations that are being updated with the energy revolution in mind, the focus will also be on the national implementation of European Network Codes.

Benefits for...


  • Application Rules provide customers with a secure and functional grid connection.
  • Compliance with the requirements ensures connection by grid operator.

Plant manufacturers and operators

  • The increased transparency of the requirements, as a result of the Application Rules, facilitates market access, simplifies follow-up and contract negotiations and, if adhered to, reduces the risk of liability due to the presumption rule.
  • Application Rules provide clarity for all market players, and thereby also reduce disputes about the need for specific requirements.

Grid operators

  • For grid operators, increased security is ensured since all customer systems are at least grid-compatible when adhering to the Application Rules.
  • The nationally uniform requirements make it easier for the grid operator to create their own grid-specific requirements, as many aspects are already covered in the regulations.
  • On the basis of the Application Rules, from the perspective of the grid, requirements can be introduced into European standardization processes at an early stage, and thereby help shape European standardization.


  • Strengthening of socio-economic autonomy, and relief of pressure on lawmakers by means of private and technical standardization of a voluntary nature

On the following pages you will find the VDE FNN Technical Connection Rules concerning voltage levels. These rules include those currently in force and those in the process of being updated.