Grid Code Compliance · Glossary

Grid Code Compliance means that an installation demonstrably complies with the technical connection and operating rules of an electricity grid. It is therefore not enough that a photovoltaic system, a wind farm, a battery storage system, an electrolyser or a power plant can feed in or draw electricity. Within defined limits, the installation must behave in such a way that the grid remains stable, secure and controllable. It can be compared with the road registration of a vehicle: a car can drive without registration, but it may only go on the road once it demonstrably meets the regulations for brakes, lights and emissions.

A grid code is a set of rules for the connection and operation of electrical installations on the grid. Among other things, it specifies which voltage and frequency ranges an installation must withstand, how it reacts to grid faults, which protection functions are required, to what extent it must provide or absorb reactive power, and which measurement, control and communication interfaces must be available. Compliance means that the installation meets these requirements and proves this to the grid operator. Depending on the installation class, this is done through unit and component certificates, installation certificates, declarations of conformity, validated simulation models, test reports, parameterisation records, commissioning reports and, in some cases, measurements during operation.

The term is closely linked to the grid connection, but does not mean the same thing. The grid connection is the physical and contractual link between an installation and the grid. Grid Code Compliance describes whether the installation is technically suitable at this connection and demonstrably behaves correctly. An installation can be fully built and electrically connected and still not be compliant. This is the case, for example, if protection parameters are set incorrectly, an inverter reacts in an impermissible way or a required certificate is missing.

Which requirements grid codes regulate

Electricity grids operate within narrow technical limits. The grid frequency shows whether generation and consumption in the synchronous system are in balance. The voltage must remain within permissible ranges locally. Short circuits, line outages or voltage dips must not cause a large amount of generation capacity to disconnect from the grid at the same time. Grid codes translate these requirements into concrete obligations for installation operators and manufacturers. At EU level, the network code for generators explicitly pursues the objective of ensuring system security and integrating renewable energy into the grid. Among other things, it requires installations to remain connected to the grid within defined frequency and voltage ranges.

A central requirement concerns frequency deviations. In the case of small deviations, installations must not disconnect immediately but must ride through defined ranges. Depending on the rules, they must reduce their active power as a function of frequency or, where technically possible, increase it. In the case of voltage dips, the issue is fault ride through: the installation must withstand a grid fault for a certain time without disconnecting impermissibly. This requirement is so important because a local fault can turn into a supra-regional stability event if many generating installations disconnect at the same time.

Another area is reactive power. In the narrower sense, it does not transport usable energy, but it influences the voltage in the grid. Modern wind turbines, PV inverters and battery storage systems can provide or absorb reactive power. Grid codes specify the range in which this capability must lie and how the grid operator uses it via characteristic curves, setpoints or remote control. In this way, installations become active building blocks of voltage control.

Protection and communication are also part of compliance. Protection systems must detect faults and disconnect installations in a targeted way. At the same time, they must not wrongly treat permissible grid events as a reason for disconnection. Via communication interfaces, the grid operator can specify setpoints, limit feed-in or monitor operating states. In Germany, for example, the NELEV requires proof of the protection concept as early as issuance in the case of a temporary type B installation certificate granted subject to conditions. This includes the higher-level decoupling protection, the decoupling protection of the generating unit and its own protection. In addition, the concept for active power control and reactive power control must be demonstrated.

Legal framework and power classes in the EU and in Germany

In the EU, the basis is Regulation (EU) 2016/631, the network code on requirements for grid connection of generators (Requirements for Generators, RfG). It applies to synchronous power-generating modules, to non-synchronous installations such as wind and PV parks, and to offshore installations. It is supplemented by separate connection codes for demand facilities and for high-voltage direct current (HVDC) transmission. The RfG divides installations into types A to D according to the voltage at the connection point and maximum capacity. Type A starts at 0.8 kW. Type D covers all installations with a connection point of 110 kV or above. For Continental Europe, the code names upper limits of 1 MW for type B, 50 MW for type C and 75 MW for type D. Member States may adjust these limits downwards.

In Germany, the Bundesnetzagentur approved lower threshold values on 24 April 2018: type B from 0.135 MW, type C from 36 MW and type D from 45 MW. Irrespective of capacity, an installation connected at 110 kV or above is classed as type D. The technical details are set out in the VDE FNN application rules for the respective voltage level. For these rules, there is a rebuttable presumption that they correspond to the generally recognised rules of technology. How proof must be provided is regulated by the Elektrotechnische-Eigenschaften-Nachweis-Verordnung (NELEV, ordinance on proof of electrotechnical properties). It applies accordingly to electricity storage systems as well.

Types B and C: A proof document is required, consisting at least of an installation certificate and a declaration of conformity. It must be issued by a certification body accredited under DIN EN ISO/IEC 17065.
Simplification for smaller type B installations: If the feed-in capacity and the cumulative installed capacity at the point of interconnection are at most 270 kW and all units subject to certification have valid certificates, no installation certificate is required. In the medium-voltage grid or higher, this suffices for an installed capacity of up to 500 kW with an additional test report for the decoupling protection.
Types C and D: Simulation models for the behaviour of the installation must be verified by an accredited certification body.
Certificate register: Since 1 February 2025, manufacturers must deposit their unit and component certificates in a register under section 49d EnWG. In the operating permit procedure, operators only submit the registration number. Grid operators may not request the certificate contents by any other route.

Distinction from certification, connection commitment and operating permit

Grid Code Compliance is often equated with certification. This is imprecise. Certificates are proof documents, not a technical property. A unit certificate shows that a specific inverter or generator type meets the requirements under defined conditions. An installation certificate considers the specific combination of generating units, transformers, cables, protection concept, park control and grid connection point. Compliance only arises from the interplay of design, components, parameterisation, proof and actual operation.

A connection commitment likewise does not replace compliance. The grid operator can reserve a connection point or confirm that a connection is possible in principle. It does not follow that the installation may be operated in every technical configuration. Software and firmware are expressly regulated in this respect: under the NELEV, a unit or component certificate in principle loses its validity if the certified electrotechnical properties change. There is a narrowly limited exception for a one-off, mandatory change that is evidenced by a supplementary proof. Manufacturers must also ensure that a software update does not overwrite the settings specified by the grid operator.

The operating permit is also not a mere formality after construction. The RfG distinguishes the procedures by installation type. For type D installations, it provides for staged notifications: an energisation operational notification, an interim operational notification and finally the final operational notification. For types B and C, the procedure relies mainly on a proof document, for which equipment certificates from an authorised certifier may be used. Under the NELEV, the grid operator must refuse the final operating permit if the proof obligations are not met. It must disconnect an already operating, non-compliant installation from the grid after a period for remedying the defects. This period is generally two months, and one month for defects in the decoupling protection.

Why compliance is becoming more important in the renewable electricity system

Earlier electricity systems were shaped by large synchronous power plants. Their generators run directly in step with the grid frequency and inherently bring rotating mass and short-circuit power with them. With the expansion of wind, photovoltaics and storage, the share of installations connected to the grid via inverters is growing. Their behaviour does not result from the physics of a machine, but from measurement, control algorithm, parameters and software. An inverter can react very quickly. But it can also be parameterised incorrectly, disconnect unexpectedly during certain grid events or build up oscillations with other controls. The more such installations operate in the grid, the more important it is that their behaviour is right at the specific grid connection point and not only in the data sheet.

For a battery storage system, this question arises even more sharply, because it can both feed in and draw electricity. It can be used for frequency support, redispatch, self-consumption or arbitrage. From the grid's perspective, it also matters how it reacts to voltage dips, communication failure or protection events. Economically sensible operation is not automatically grid-compatible. The grid code sets out the technical framework within which economic optimisation is allowed. Large consumers such as electrolysers, data centres or industrial installations can also affect the grid through rapid load changes, reactive power demand or harmonics. A separate EU connection code for demand facilities applies to them.

Typical misunderstandings

A widespread error is to see Grid Code Compliance as a one-off product approval. Many requirements, however, depend on the specific connection point. Voltage level, short-circuit power, grid impedance, protection concept and neighbouring installations help determine whether a behaviour is permissible. A certified inverter can be used correctly in one installation and need additional proof or different settings in another.

A second error equates technical capability with verified performance. That an installation can provide reactive power or ride through faults does not mean that it does so in every operating situation to the required extent, with the right dynamics and in interaction with other installations. That is why grid codes require defined characteristic curves, response times, measurement accuracies and limit values.

It is also often overlooked that grid codes are not laws of nature. They are technically justified rules set by institutions: the EU Commission through network codes, regulatory authorities through thresholds and approvals, standardisation bodies and grid operators through application rules. This gives rise to costs, deadlines and responsibilities. Additional measurement transformers, protection technology, park controllers, certification and simulation studies increase the effort and time required for a project. These costs are not simply bureaucracy, even if procedures can be too slow or inconsistent. They arise because many decentralised installations must jointly produce a grid behaviour that a few large power plants used to provide. This is precisely why the legislator in Germany has created simplifications for smaller installations, such as the 270 kW limit.

Relationship to the market, grid operation and security of supply

Grid Code Compliance limits market participation and at the same time makes it possible in the first place. An installation may earn revenues on the electricity market as long as its operation meets the technical minimum requirements of the grid. In the event of congestion, frequency deviations or voltage specifications, grid requirements can change economic schedules. For security of supply, compliance is a foundation, but does not replace system planning. Compliant installations behave predictably within the defined framework. They do not replace sufficient grid capacity, firm capacity, reserves or grid expansion.

Further development: RfG 2.0 and grid-forming inverters

Because the share of inverter-based installations is growing, grid codes are being further developed. On 8 July 2026, the EU Commission published the draft of a delegated regulation revising the existing network code (RfG 2.0). The public consultation ran until 25 August 2026. The draft goes back to a 2023 recommendation by the European regulatory agency ACER. It expressly includes storage, electric vehicles and other inverter-based installations and also contains requirements for grid-forming capabilities intended to enable behaviour similar to inertia. Until adopted, however, it is not binding. As of November 2026, Regulation (EU) 2016/631 continues to apply. After adoption, transitional periods and national implementation steps are also to be expected. For manufacturers and operators, compliance thus becomes more dynamic: they must expect that more precise proof and more robust control concepts will be required in future.

Grid Code Compliance is thus the reliable proof that an installation does not merely exchange energy, but complies with the technical rules of the grid. The term distinguishes mere connectability from system-compatible operation. This distinction becomes all the more important the more the electricity system consists of many decentralised installations that are controlled by power electronics and economically optimised.

Sources

Verordnung (EU) 2016/631 der Kommission vom 14. April 2016 zur Festlegung eines Netzkodex mit Netzanschlussbestimmungen für Stromerzeuger — Europäische Union, EUR-Lex; 2016-04-14. Erwägungsgründe 3, 10, 17; Art. 1, Art. 5 (Typen A–D), Art. 29 ff. (Betriebserlaubnisverfahren), Art. 35 (vorübergehende Betriebserlaubnis Typ D)
Elektrotechnische-Eigenschaften-Nachweis-Verordnung (NELEV) — Bundesministerium der Justiz / Bundesamt für Justiz (gesetze-im-internet.de); 2017-06-12 (zuletzt geändert 2024-05-16). §§ 1–7, insbesondere § 2 Abs. 2–6, § 4 Abs. 3, 9, 10, § 5, § 6, § 7 Abs. 4
Beschluss BK6-16-166: Genehmigung der Schwellenwerte für die Maximalkapazität von Stromerzeugungsanlagen des Typs B, C und D — Bundesnetzagentur; 2018-04-24. Tenor und Abschnitt 3.1
Revision of Network Code on Requirements for Grid Connection of Generators — Energy Storage Europe; 2026-08. Nachrichtenseite, Abschnitte zum Entwurf und zur Konsultation
42nd Grid Connection European Stakeholder Committee (GC ESC) – Minutes — ENTSO-E; 2026 (genaues Datum unbekannt). Punkt 2, EC-RfG Network Code – Updates

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Edited by eCMS on 12.11.2026 05:05