Significant Grid User (SGU)
Significant Grid User (SGU) in the terminology used in the European Union Internal Electricity Market is the existing and new Power Generating Facility and Demand Facility deemed by the Transmission System Operator (TSO) as significant because of their impact on the transmission system in terms of the security of supply including provision of ancillary services.
Significant Grid Users are assigned tasks important for the functioning of the EU Internal Electricity Market.
According to Article 4(2)(c) of the Emergency and Restoration Network Code (Commission Regulation (EU) 2017/2196 of 24 November 2017 establishing a network code on electricity emergency and restoration - NC ER) each TSO is required to submit to the relevant regulatory authority for approval the list of SGUs responsible for implementing on their installations the measures that result from mandatory requirements set out in the connection network codes:
- NC DC,
- NC RfG,
- NC HVDC, and/or
from national legislation and the list of the measures to be implemented by these SGUs, identified by the TSOs under Art. 11(4)(c) and 23(4)(c) of the NC ER.
These measures may relate, in particular, to the design of the Restoration Plan.
According to Article 35(3) of the NC ER in case of suspension of market activities upon request of the TSO, each SGU is required to operate, where technically possible, at an active power set-point established by the TSO.
Significant Grid Users are those grid users whose influence on the transmission system needs to be taken into account for operational security (ENTSO-E Supporting Document for the Network Code on Operational Security of 24 September 2013 2nd Edition Final (p. 154)).
The impact on the transmission system can have different causes: grid user directly connected to the transmission system are considered to be significant because they are large Power Generating Facilities or Demand Facilities; grid users providing ancillary services are also considered significant because they influence the generation-demand balance.
Besides, other large Power Generating Facilities connected to the distribution network can have significant impact to the transmission system so they also need to be considered as Significant Grid Users.
Connection codes define the technical requirements that Significant Grid Users must comply with to connect to the transmission system.
These requirements apply mainly to new grid users but cover a very broad range of them, from big to small ones.
SGU is a concept of the Network Code on System Operation, which was developed after connection codes and it takes them into account but applies different significance thresholds.
From operational security perspective the criteria are applied to grid users independently of the date of their connection to the system, but only to those with direct impact in the transmission system due to their size or the services they are providing.
This includes those grid users not individually significant, but that become significant when aggregated.
It follows that the criteria for Significant Grid Users are a combination of the criteria for Significant Power Generating Modules and Significant Demand Facilities, applied to both new and pre-existing ones.
According to Article 40 of the NC ER each TSO when in the following system states:
- blackout or
is entitled to gather from SGUs information about at least the following conditions:
(i) the current status of the installation;
(ii) the operational limits;
(iii) the full activation time and the time to increase generation; and
(iv) the time critical processes.
Perspectives for the SGUs' legal framework
The ACER first Implementation Monitoring Report of 20 July 2022 on the System Operation Guideline observes that a wide range of power thresholds considered to define the SGUs responsible to exchange data limits the level playing field in the EU.
Hence, the ACER recommends proportionate changes to the data exchange rules aiming at harmonising applicable criteria for SGUs definition when amending the Commission Regulation (EU) 2017/1485 of 2 August 2017 establishing a guideline on electricity transmission system operation (Network Code on System Operation or System Operation Guideline - SOGL), taking into account the non-discrimination and data exchange purposes.