The introduction of Grid Supply Point (GSP) Technical Limits is an initiative developed as part of the ENA’s 3-Point Plan, working to accelerate the connection of generation and storage into the distribution network ahead of the required transmission reinforcement works.
The growing volume of connecting generation held off by the long build times of network assets makes initiatives such as GSP Technical Limits evermore relevant. Having a significant positive impact on the connection dates of customers, GSP Technical Limits will tie into components of the National Energy System Operators’ Connections Reform, which is currently in progress. This document is intended as a walkthrough for customers, detailing the methodology for the calculation and implementation of GSP Technical Limits.
Download the guidance document here.
Overview of the GSP Technical Limits solution
A Technical Limit is a limit for a specific Grid Supply Point (GSP) agreed between NESO and DNOs. It allows DNOs to connect customers within the scope and pre-requisites of the solution, ahead of the completion of required transmission reinforcement works, under the condition that the DNOs limit the power flow across the GSP to their agreed limit. This is facilitated through the DNOs’ deployment of an automated control scheme, such as Active Network Management (ANM) or Distributed Energy Resource Management System (DERMS), and the subsequent control of generation customers’ power imports and exports.
The GSP Technical Limits represent MW figures for the import and export of power across DNOs’ individual GSPs. Calculations are undertaken using formulas agreed through the ENA, with Distribution Network Operators (DNOs) being offered four GSP Technical Limits for both the import and export of power, reflective of four periods of the year, and considerate of factors such as capacities contracted to connect/already connected, energy demand at the GSP, as well as the impact of future demand growth. Whilst the import GSP Technical Limits are reflective of the differing values for four periods of the year, the export GSP Technical Limits take the largest figure calculated before extrapolating and applying it across the whole year.
With these figures agreed, the DNO can accelerate the connection of their customers, creating a larger pool of generation to be utilised to contribute to their GSP Technical Limit headroom. This process removes the need for the completion of transmission reinforcement works before the connection of generation, provided customers are happy to meet the requisite commercial and technical requirements, and they are eligible.
What does it mean for customers?
For customers prevented from connecting to the distribution network until the completion of transmission reinforcement works, GSP Technical Limits may allow for an earlier connection date. The primary impact on customers choosing to advance their connection through this initiative is their subjection to unpaid curtailment under specific conditions (an automatically applied reduction in the power export or import of the site). The level of this curtailment will vary, dependent on a customer’s connection queue position, and how the relevant DNO implements the curtailment.
Once it is established that a GSP can be allocated Technical Limits, the DNOs will discuss with relevant Small and Medium Restricted Generators to establish their interest in receiving a curtailed connection offer provided they hold a Gate 2 offer. This process will typically involve an application through an Expression of Interest (EOI). The DNO will then issue a variation to the customer’s connection offer, containing an estimate of the export and import curtailment values for the relevant Restricted Generator, based on the GSP Technical Limits for the GSP, and the methodology the DNO is using to calculate the curtailment.
When will this be implemented?
A phased rollout had been adopted to implement GSP Technical Limits in England and Wales. Subject to a series of pre-requisites, GSPs of simpler configurations formed Phase 1a and 1b, processed throughout Q3 2023 and Q4 2023 respectively. GSPs with a more complex configuration and fault level issues formed Phase 2 which was rolled out across 2024. Customers connecting to GSPs that partook in Phase 1 and Phase 2 should have already received offer variations subject to them holding a signed variation offer detailing their Transmission works outcome. For rollout in Scotland (SSEN network), Technical Limits were implemented in a similar phased approach with eligible customers being offered Technical Limits.
The ENA has published how Technical Limits offer will continue as Connections Reform is implemented. For more details, please refer to the Technical Limits offer plan within Connections Reform.
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What are GSP Technical Limits?
Calculated on an individual GSP basis, GSP Technical Limits are captured in the technical appendices of the DNO’s relevant Bilateral Connection Agreement (BCA) with NESO. It is important to note that commercial and technical requirements may vary between GSPs, and across different DER. However, there is a clear methodology associated with these requirements, detailed again in the technical appendices of the BCA, to ensure the DNOs take a transparent and fair approach to applications, especially when considering changes that may affect queue positions, or queue management milestones.
The DNOs will utilise GSP Technical Limits to actively manage the queue of unconnected non-firm generators that have chosen to connect under the relevant terms. These generators will be referred to as 'Restricted Customers’ throughout the rest of this document. Under GSP Technical Limits terms, Restricted Customers’ DER schemes will connect on a non-firm basis, subject to receiving sufficient notices/evidence to progress from developers, and will be subject to unpaid curtailment by the DNO. The DNO will be responsible for reporting to NESO any changes to the DER as part of the existing processes.
Whilst the initiative allows connection ahead of the completion of transmission reinforcement works, it is important to note that some customers may also be subject to local GSP ‘attributable works’, such as the need for a new bay, fault level/safety mitigation works which are crucial for a safe and efficient connection. In these instances, an earlier connection date utilising GSP Technical Limits will not be possible until those works have been completed.
This initiative enables accelerated connections for some Restricted Customers on a non-firm basis, however, it will not affect the access rights or curtailment of 'Unrestricted Customers’, i.e. those downstream of the GSP that are already connected or contracted to connect and not subject to transmission reinforcement works.
How is it calculated?
The calculation process provides GSP Technical Limits for both power export and import across a defined transmission and distribution boundary and are calculated using the formulae presented below.
Export GSP Technical Limits
The calculation for the export GSP Technical Limits uses the sum of the Unrestricted Registered Capacities of the DER connected or due to connect without the need for transmission works, a pre-defined list of scaling factors, and gross demand data for four periods of the year, known as cardinal points. For GSP Technical Limits applied in Scotland, scaling factors have not been used, and just one demand point from the year will be used.
Since there are four cardinal points, defined below, four export GSP Technical Limits will be calculated, and following agreement between parties, the largest figure given will be extrapolated across the entire year.
Export GSP Technical Limit =(Unrestricted Registered Capacity*Scaling Factors)-Demand at Defined Cardinal Points
Definitions for formula:
Unrestricted Registered Capacity = all generation downstream of the GSP that is already connected or contracted to connect and not subject to transmission reinforcement works.
Scaling factors = specific to technology type, a value between zero and one that is multiplied by generator capacity to create assumed power output for scenario-based backgrounds. See Table 1 for Scaling Factors.
Demand at defined cardinal points = gross minimum GSP demand (i.e., absent of contributions from small, medium, or large embedded power stations), for each cardinal point, observed on dates below:
Winter cardinal point – 01 Dec to 28 Feb
Access Period (maintenance period) cardinal point – 01 Mar to 31 May, or 01 Sep to 30 Nov
Summer Solar Max cardinal point – 01 Jun to 31 Aug (between 10:00-16:00)
Summer Solar Min cardinal point – 01 Jun to 31 Aug (between 04:00-06:00)
Table 1: Scaling Factors proposed for creating assumed export/ import
Fuel Type
Winter
Access Period
Summer (Solar Max)
Summer (Solar Min)
Solar PV
0
0.051
0.84
0.051
Waste/ CHP
0.88
0.88
0.85
0.85
Hydro
0.84
0.84
0
0
Wind
0.7
0.7
0.5
0.1
Other
0.65
0.65
0.3
0.3
BESS/ Energy Storage
-1
-1
1
1
Note: For GSP Technical Limits applied in Scotland, scaling factors have not been used.
Import GSP Technical Limits
The calculation for the import GSP Technical Limits uses the maximum observed demand at the GSP for the four defined cardinal points, the import capacities of unrestricted Battery Energy Storage System (BESS) projects not yet connected, and 1 Year of Distribution Future Energy Scenarios (DFES) demand growth. A scaling factor for BESS was not used in this equation as import demand is assumed as maximum/full capacity.
Since there are four cardinal points, four import GSP Technical Limits will be calculated, and will be used accordingly throughout the year. During the summer period, the largest of the two GSP Technical Limits given, Summer Solar Max, will be used by the automated control schemes to operate to.
Import GSP Technical Limit= Maximum Observed Demand at Defined Cardinal Points+BESS Import+1 Year DFES Growth
Definitions for formula:
Maximum Observed Demand at Defined Cardinal Points = maximum observed/net demand at the GSP (i.e., includes contributions from small, medium, or large embedded power stations generating), for each cardinal point, observed on dates below:
Winter Cardinal Point – 01 Dec to 28 Feb
Access Period (maintenance period) Cardinal Point – 01 Mar to 31 May, or 01 Sep to 30 Nov
Summer Solar Max Cardinal Point – 01 Jun to 31 Aug (between 10:00-16:00)
Summer Solar Min Cardinal Point – 01 Jun to 31 Aug (between 04:00-06:00)
BESS import = those BESS Unrestricted Customers not yet connected.
DFES growth = 1 Year of Distribution Future Energy Scenarios (DFES) demand growth is used to calculate GSP Technical Limits.
Alternative GSP Technical Limits
Under some scenarios, it is possible that the export GSP Technical Limit calculated could be less than the current observed power flow across the Transmission and Distribution Boundary at a certain GSP. In such a case, the DNO should share evidence of this with NESO and the relevant TO. The export GSP Technical Limit should be the maximum observed export at each cardinal point added to, where applicable, the scaled generation of any unconnected Unrestricted Registered Capacity.
Each DNO’s DFES can be found on their respective websites, detailing the growth of the distribution network’s demand in the coming years.
Since there are four cardinal points, defined below, four export GSP Technical Limits will be calculated, and following agreement between parties, the largest figure given will be extrapolated across the entire year.
Alternative Export GSP Technical Limit =Maximum Observed Export at Defined Cardinal Points+(Unconnected Unrestricted Registered Capacity*Scaling Factors)
Definitions for formula:
Maximum Observed Export at Defined Cardinal Points = the maximum power exchange at the site from the previous calendar year, for each cardinal point, observed during the periods below:
Winter cardinal point – 01 Dec to 28 Feb
Access Period (maintenance period) cardinal point – 01 Mar to 31 May, or 01 Sep to 30 Nov
Summer Solar Max cardinal point – 01 Jun to 31 Aug (between 10:00-16:00)
Summer Solar Min cardinal point – 01 Jun to 31 Aug (between 04:00-06:00)
Unconnected Unrestricted Registered Capacity = all generation downstream of the GSP that is unconnected and not subject to transmission reinforcement works.
Scaling factors = specific to technology type, a value between zero and one that is multiplied by generator capacity to create assumed power output for scenario-based backgrounds. See Table 1 for Scaling Factors.
It should be noted that the formulae may need further revision as NESO’s work to utilise revised Construction Planning Assumptions is implemented. Further analysis is required to understand the impact of this work, which will continue alongside the initial rollout.
How is it managed?
GSP Technical Limits only become effective once the relevant DNO has signed their agreement with NESO to add the terms and conditions of GSP Technical Limits into their BCA.
A DNO may only advance the connection and energisation of Restricted Generators behind GSP Technical Limits when their GSP Technical Limits Scheme has commissioned, and achieved necessary compliance sign off by NESO.
The DNO will be required to monitor and control the pre-fault net power exchange at the Grid Supply Point (GSP) within the GSP Technical Limits specified in their technical appendices throughout the year. At some sites, this will be enabled through the provision of required data by NESO, via a real-time data exchange link between DNO and NESO control systems.
It is the DNO’s responsibility to design an automated control scheme that manages the power contributions from DER that are connected under GSP Technical Limit terms, so that the GSP’s power flow does not exceed either the export or import GSP Technical Limits agreed with NESO and is in accordance with the associated compliance process. The automated control scheme must be permanently armed, and this shall form part of the DNO’s System.
The GSP Technical Limit Scheme will be monitored by NESO to ensure it is healthy at all times. The DNO shall inform the TO and NESO of any issues related to the GSP Technical Limit Scheme that impacts on the operation of the Transmission System, and any proposed mitigating actions to ensure the GSP Technical Limits can continue to be met at all times.
If the GSP Technical Limit Scheme is not healthy, or fails to meet the requirements as described above, NESO will notify the DNO as such, and the supporting Compliance Process will be followed. A remedial course of action will be sent by the DNO to the ESO in writing before a trilateral investigation between NESO, DNO, and TO is undergone to understand the causation for the scheme’s ill health/failure.
The NESO shall track the DNOs’ adherence to their GSP Technical Limits, and reserves the right to temporarily reduce or suspend the use of the GSP Technical Limits following consistent instances of non-compliance by the DNO.
When is a GSP Technical Limit changed?
The GSP Technical Limits may be changed periodically to reflect changes to the contracted background on both distribution and transmission systems. Triggers for this reassessment are typically as follows:
- Annual review. Each GSP Technical Limit will be reassessed annually, to take account of changes to GSP demand levels and changes to contracted generation background.
- Completion or removal of the need for transmission reinforcement works.
- Termination of transmission connected capacity.
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Frequently Asked Questions
If my project has received a Gate 1 offer, will I still be able to accelerate my connection under Technical Limits?
As per Connections Network Design Methodology (CNDM) 5.24.7, projects that do not receive a Gate 2 offer cannot connect under Technical Limits. Technical Limits is an interim solution for accelerating connections for projects with a Transmission queue position. As Gate 1 projects do not have a Transmission queue position, they are not eligible for Technical Limits.
What does Grid Supply Points (GSPs) with established Technical Limits mean?
These are GSPs where Technical Limits have already been agreed and established in the Distribution Network Operator's (DNO’s) Bilateral Connection Agreement (BCA) with NESO as part of the Technical Limits rollout.
The list of Technical Limit GSPs for each DNO can be found on their website:
Scottish and Southern Electricity Networks
Scottish Power Energy Networks
National Grid Electricity Distribution
When will Technical Limits be established in Grid Supply Points (GSPs) that currently do not have them?
GSPs that consist of eligible Relevant Embedded Power Stations (REPS) requiring Transmission works will be considered for establishing Technical Limits in the first National Energy System Operator (NESO) Gate 2 Application (CMP434) window. This enables network operators to better understand the transmission constraints for each GSP following Gate 2 To Whole Queue (CMP435) reassessment and identify eligible projects accordingly.
Why could Technical Limits offers not be issued along with the Gate 2 offer rather than an Expression Of Interest (EOI)?
Signing the Gate 2 offer is necessary before receipt of a Technical Limits offer because Technical Limits cannot progress projects held behind non‑thermal constraints such as fault‑level issues or physical works.
Accepting Gate 2 enables the Distribution Network Operator (DNO) to understand the agreed enduring solution and also produce a more accurate curtailment assessment, since the Technical Limits Last In First Out (LIFO) queue is determined by projects’ Gate 2 and EOI responses. Projects that do not accept their Gate 2 offer are removed from the LIFO.
If my project has accepted a Technical Limits offer and previously associated Transmission works now fall away, will I still be required to be managed to the GSP's Technical Limit?
No, if the Gate 2 To Whole Queue reassessment results in Transmission works associated with the project falling away or if Transmission works are completed, Technical Limits will no longer be a requirement to connect the project.
If I previously responded "No" to an Expression Of Interest (EOI), will my project still be eligible for Technical Limits from National Energy System Operator (NESO) and will I still obtain an EOI, given that I previously said "No"? i.e if I was Technical Limits applicable pre-reform, will I be Technical Limits applicable post-reform?
Subject to Gate 2 Whole Queue Reassessment confirming continued Technical Limits eligibility (i.e. no fault level or physical works triggered), the project will remain eligible for a Technical Limits offer. Projects that have not previously expressed interest in Technical Limits will be given the opportunity to submit an EOI alongside their Gate 2 variation offer. If the project expresses an interest, the project will be considered for a Technical Limits offer once all projects within the same Grid Supply Point (GSP) and phase have signed their Gate 2 offers.
- Appendices