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Grid connection requirements

Regulatory and legal background

All customers connected to a public electricity network, whether generators or consumers, must comply with agreed technical requirements, in order for the network to operate safely and efficiently.  Electricity networks rely on generators to provide many of the control functions, and so the technical requirements for generators are unavoidably more complex than for demand customers.  

These technical requirements are often termed ‘Grid Codes’, though the term should be used with care, as there are often different codes, depending on the voltage level of connection, or the size of the project. Also, there may be technical requirements that are not referred to in the Grid Code, but which apply to the project through the connection agreement, the power purchase agreement, or in some other way.

The purpose of these technical requirements is to define the technical characteristics and obligations of generators and the system operator, meaning that:

• electricity system operators can be confident that their system will be secure regardless of the generation projects and technologies applied;
• the amount of project-specific technical negotiation and design is minimised;
• equipment manufacturers can design their equipment in the knowledge that the requirements are clearly defined and will not change without warning or consultation;
• project developers have a wider range of equipment suppliers to choose from;
• equivalent projects are treated fairly;
• different generator technologies are treated equally.

In the past, with vertically-integrated utilities, the same organisation was responsible for the planning and operation of networks and generators, so the technical requirements did not need to be particularly clearly defined or fair. Nowadays, in order to avoid distortions of competition and to comply with a liberalised energy market in Europe, there is a trend towards the legal separation of generators and system owners/operators.  As a result, the technical requirements governing the relationship between generators and system operators need to be more clearly defined. The introduction of renewable generation has often complicated this process significantly, as these generators have physical characteristics that are different from the directly connected synchronous generators used in large conventional power plants. In some countries, this problem has caused significant delays in the development of fair grid code requirements for wind generation.

In some countries, a grid code specifically for wind farms has been produced, and in others, the aim has been to define the requirements as far as possible in a way which is independent of the power plant technology.

There are benefits to requirements that are as general as possible, treating all projects equally. However, this can result in small projects facing the same requirements as the largest projects, which may not be technically justifiable.

Requirements are usually written by the system operator, often overseen by the energy regulator body or government. The requirement modification process should be transparent, and include consultation with generators, system users, equipment suppliers and other affected parties.