Connection procedure
On request, the grid operator is obliged to the plant operator to connect plants within their area of responsibility as soon as they comply with the technical requirements. The connection of plants shall be based on non-discriminatory criteria. There is no grid connection permit process as such. All renewable power installations can be connected to the grid, provided they fulfill the technical requirements and pay for grid connection according to the payment system in place, which is based on the length of the connection.
The application for grid connection has to be submitted to the TSO Elering or the DSO. According to the relevant Estonian regulation (TSO Elering Grid Connection Methodology), all project developers have to bear grid connection costs themselves. As a general rule, installations exceeding the rated power of over 1 MW need approval by the TSO for grid connection. For wind turbines and PV installations, the standard is lower: all installations with a capacity of more than 200 kW need approval from the TSO, and they can then be connected either to the TSO or DSO. All wind turbines and PV installations with a capacity exceeding 10 MW can be connected to the TSO only (art. 18 Grid Code). It is the responsibility of the DSO to inform TSO of installations to be connected to the network and provide information on their technical data (art 19 Grid Code). After submitting the application for grid connection, the process unfolds in the following steps:
- acceptance of the application
- entering the grid connection agreement
- building the connection point
- supplying electricity
- synchronising testing and
- final grid connection contract.
The final grid connection contract requires that the testing period has been successfully completed, the production unit has received the certificate of conformity to the grid code, and the production unit models have been verified (Guide to Connecting to National TSO).
Rules concerning the connection of a new producer to the grid
According to the Grid Code and Electricity Market Act, the grid operator is obligated to connect new plants within their area of responsibility as soon as they meet the technical requirements. Connections are made based on non-discriminatory criteria, and there is no formal grid connection permit process. All renewable power installations can be connected to the grid if they fulfill the technical requirements and pay for the connection costs, which are based on the length of the connection. Applications for grid connection must be submitted to either the Transmission System Operator (TSO), Elering, or the Distribution System Operator (DSO). Generally, installations exceeding 1 MW require TSO approval, while those over 200 kW for wind and photovoltaic (PV) systems also need TSO approval. The process includes acceptance of the application, entering a grid connection agreement, building the connection point, and finalising a grid connection contract after successful testing.
The Electricity Market Act designates the DSO as responsible for connecting distribution networks and ensuring long-term capacity. Power plants with over 5 MW must have remote reading devices installed and be coordinated with the TSO during the connection process. For plants up to 1 MW, approvals are handled by the DSO. All applications must include an environmental impact assessment and detailed plans. Connection fees are paid in instalments, and upon payment of the first instalment, construction of the network connection begins. The grid operator may also be required to upgrade the grid if necessary. The Grid Code specifies various technical requirements for different capacities, including relay protection systems that must be installed to ensure safe operation when connecting to the network.
The connection for 1-10 MW power plants is approved by either TSO or DSO. The decision on the connection is made based on the electrical design documentation. Relay protection, approved by the network operator, is required to be installed. At a power plant with synchronous generators, an automatic disconnection by frequency drop has to be installed. The network operator has to install a backup protection and a backup automatic disconnection at a point from the connection point towards the network. The connectee submits the set points of relay protection and automation to the network operator before connecting the power plant.
To submit the grid connection application, the producer must have selected the type of production unit, and the environmental impact assessment and detailed plan must also be ready. Elering will make an offer within 90 days. After receiving the offer, the producer seeking grid access has 60 days to sign the contract.
When submitting a grid access application, procedural costs must be paid. As per the grid code, the connection fee shall be paid in three instalments. After the first instalment is received, the TSO begins constructing the network connection and other necessary grid reinforcement works. The new customer, meanwhile, starts engineering and building its production unit and connecting up to the connection point.
Rules for connecting RES and storage to the grid
There are simplified conditions for connection to the network of power-generating installations whose capacity is below 15 kW and which use a renewable source for generation, according to the Grid Code. A self-consumer of renewable electricity has the right to install and operate, for their own use, electricity storage systems combined with plants producing renewable electricity, without these being subjected to double fees, including network fees, according to the Electricity Market Act.
Supplementary requirements apply to wind turbines, wind farms and solar power plants. Wind and solar power stations with a capacity of 10 and more MW are required to join the transmission system. Wind turbines and wind farms are required have a wind overspeed protection. Solar panels, wind farms and wind turbines must have relay protection, according to the Grid Code.
A DSO cannot own storage devices or charging infrastructure for electric cars unless the ECA has granted a separate exception. In order to sell an energy storage unit, a network operator arranges a public auction and obtains the ECA’s approval, according to the Electricity Market Act. The DSO has to file the real-time data to the TSO for the plants with the rated power of 200 kW to 1 MW. The data on the wind turbines, wind farms and solar panels is submitted separately from the other sources of electricity.
What are the specifications for islands, isolated grids, microgrids, local grids, etc.?
Regarding islands, the state shall ensure the supply of electricity to a small island. The additional expenses arising from the special nature of the settlement shall be compensated pursuant to the procedure established by the government, according to the Permanently Inhabited Small Islands Act.
In a micro-isolated network, the service is provided by the DSO where the micro-isolated network is located. According to the Electricity Market Act, the DSO and the electricity producer may be one and the same person.
Such networks are established either to meet legal obligations of the distribution network operator or in sparsely populated areas where energy consumption is less than 15 megawatt-hours per kilometre of power line. To create a micro-isolated network, it must be economically justified, and the network contract with consumers must guarantee standard terms of service as approved by the relevant regulations. Additionally, micro-isolated networks cannot be established in areas where consumers provide essential services or are located near national defence installations.
Energy communities
According to the Permanently Inhabited Small Islands Act, the state ensures an electricity supply to small islands. The additional expenses arising from the settlement's special nature are compensated according to government procedure.
An energy community is a legal person. It supplies electricity that it has generated itself for consumption to its members using installations erected by the community or a service provided by the area’s DSO. A DSO cooperates with an energy community to facilitate conveying any electricity that has been generated by the community for consumption to members of that community.
Renewable energy communities can produce renewable energy for their own consumption.
A renewable energy community has the right to produce, consume, store or sell renewable energy. It can share, within the community, renewable energy that is produced by production units owned by that community, maintaining the rights and obligations of the community’s members as customers. It has access to all suitable energy markets either directly or through aggregation. Energy metering points of a renewable energy community use a dedicated remote-reading device to measure the energy used, according to the Energy Sector Organisation Act.
Renewable energy sources are categorised as water, wind, solar, wave, tidal and geothermal, landfill gas, sewage treatment plant gas, biogases, and biomass. Liquid biofuel is regarded as a renewable energy source if it meets the criteria for the sustainability of liquid biofuels, according to Electricity Market Act.
Possibilities to differentiate RES in scale and technology
Renewable energy sources are categorised as water, wind, solar, wave, tidal and geothermal, landfill gas, sewage treatment plant gas, biogases, and biomass. Biomass is the biodegradable fraction of products, waste, and residues from agriculture, forestry, and related industries, and the biodegradable fraction of industrial and municipal waste. Liquid biofuel is regarded as a renewable energy source if it meets the criteria for the sustainability of liquid biofuels.