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.
Network Code on System Operation
Responsibility of the SGUs
1. Each SGU shall notify the TSO or DSO to which it has a connection point about any planned modification of its technical capabilities which could have an impact on its compliance with the requirements of this Regulation, prior to its execution.
2. Each SGU shall notify the TSO or DSO to which it has a connection point about any operational disturbance in its facility which could have an impact on its compliance with the requirements of this Regulation as soon as possible after its occurrence.
3. Each SGU shall notify the TSO or DSO to which it has a connection point of the planned test schedules and procedures to be followed for verifying the compliance of its facility with the requirements of this Regulation, in due time and prior to their launch. The TSO or DSO shall approve in advance and in a timely manner the planned test schedules and procedures and the approval shall not be unreasonably withheld. Where the SGU has a connection point to the DSO and interacts, pursuant to paragraph 2, only with the DSO, the TSO shall be entitled to request from the concerned DSO any compliance testing results, which are relevant for the operational security of its transmission system.
4. Upon request from the TSO or DSO, pursuant to Article 41(2) of Regulation (EU) 2016/631 and Article 35(2) of Regulation (EU) 2016/1388, the SGU shall carry out compliance tests and simulations in accordance with those Regulations at any time throughout the lifetime of its facility and in particular after any fault, modification or replacement of any equipment, which could have an impact on the facility's compliance with the requirements of this Regulation regarding the capability of the facility to achieve the values declared, the time requirements applicable to those values and the availability or contracted provision of ancillary services. Third parties providing demand response directly to the TSO, providers of redispatching of power generating modules or demand facilities by means of aggregation, and other providers of active power reserves shall ensure that the facilities in their portfolio comply with the requirements of this Regulation.
"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
Network Code on System Operation, Article 54
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), Article 4(2)(c), Article 35(3), Article 40