Significant Grid User means 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 (source of the definition: the draft Network Code on Operational Security).
Significant Grid Users are assigned tasks important for the functioning of the EU Internal Electricity Market. For example, pursuant to the Emergency and Restoration Network Code, in the design of Restoration Plan, each TSO identifies Significant Grid Users that have to implement measures on their installations, when these measures are using mandatory requirements from NC DC, NC RFG, NC HVDC or national legislation and list the measures to be implemented by these Significant Grid Users.
"SGU: a unique concept of the System Operation Codes
Significant Grid User is significant for the important System Operation matters such as the provision to the TSO or DSO of structural data, forecast output or consumption data, provision of real-time data and other obligations such as to follow a TSOs instruction to protect Operational Security.
The term SGU is unique to the System Operation Codes and differs from the terms Significant Generating Module used in the NC RfG or Significant Demand Facility used in DCC, which primarily sets out the design and build capability requirements for different sizes. The definition of SGU clearly specifies that PGMs which are not type B, C, D will never be considered as SGU. Only their Aggregator providing services directly to TSO is SGU. The intention is not and there is no reason to hinder market development by putting limits with a minimum value for level of aggregation to participate in services to TSO. When needed harmonised minimum technical requirements are further defined in the respective network codes (like in NC LFCR for active power reserves or NC EB for balancing purpose).
The criteria to establish the significance of Grid Users relies on the following main aspects:
a) Grid Users directly connected to the Transmission System;
b) Influence of the Grid Users on the Generation-Demand Balance.
c) Grid Users providing services directly to the TSO.
Grid Users directly connected to the Transmission System are significant for two reasons: they are big Power Generating Facilities and big Demand Facilities so they have significant influence on the Transmission System. As they are directly connected to the Transmission System, they shall be accordingly taken into account in the System Operation. Type D Power Generating Modules, both old and new ones, and Demand Facilities directly connected to the Transmission System are included in this category.
All Grid Users that provide Ancillary Services directly to the TSO are also considered Significant Grid Users. Demand Facilities, Closed Distribution Networks and Aggregators according to Article 1(5)(b) and Aggregated Power Generating Modules according to Article 1(5)(d) are included in this category. This Significant Grid Users have influence on the Generation-Demand Balance via DSR, Redispatching or providing Active Reserve and doing so they are direct clients to the TSO. All Grid Users providing a service directly to the TSO need to be considered as Significant so the TSO can take into account and verify the provision of that service irrespective of their size. Provision of Service by SGU to TSO is always subject to contract and those contracts will define fulfilment of minimum technical requirements and pre-qualification tests.
Type B and C Power Generating Modules shall also be included in the group of SGUs. These Power Generating Modules generate up to 50 and 75 MW in Continental Europe. This is a noticeable size, particularly for smaller TSOs. It should be taken into account that the development of generation from RES has increased and will keep increasing the amount of small and medium Power Generating Facilities that cannot be aggregated due to their geographical dispersion; some examples are Denmark, Germany or Spain."
Source: ENTSO-E Supporting Document for the Network Code on Operational Security of 24 September 2013 2nd Edition Final, p. 61, 62
ENTSO-E Supporting Document for the Network Code on Operational Security of 24 September 2013 2nd Edition Final (p. 154) explains, moreover, Significant Grid Users are those Grid Users whose influence on the Transmission System needs to be taken into account for Operational Security.
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.
Network Code on Operational Security was developed after Connection Codes and it takes them into account but needs to apply different significance thresholds.
From Operational Security perspective the criteria shall be 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.
A subcategory of Significant Grid Users are those of a "high priority".
Pursuant to the Article 32(10) of the draft Network Code on Operational Security each Transmission System Operator must elaborate a list of high priority Significant Grid Users which are Power Generating Facilities or Demand Facilities, in terms of the conditions for their disconnection and re-energizing.