Curtailment and DERMS
What is DERMS?
DERMS (Distributed Energy Resources Management System) is a technology employed by UK Power Networks to connect more customers to our networks faster and at a lower cost by avoiding or deferring the need for network reinforcement.
We use a Distributed Energy Resources Management System (DERMS) to oversee and optimise the integration of Distributed Energy Resources (DERs) across our electricity distribution network.
DERMS achieves this by managing participating customers in real-time to keep the network within safe operational limits. DERMS utilises real-time measurements on the network and sends upper setpoints to customers.
DERMS is integrated into our Advanced Distribution Management System (ADMS) using an Inter-Control Centre Communications Protocol (ICCP) link. The setpoint instruction is passed over our Supervisory Control and Data Acquisition (SCADA) communication network to our Remote Terminal Unit (RTU) and onto the customers controller to implement.
Non-firm access products
What connection products does DERMS monitor and control? A range of non-firm access products (curtailable, flexible, profiled etc.) is available to support efficient connections to the grid while managing network constraints. These products are designed to address specific challenges, such as thermal constraints, voltage issues, or curtailment management, enabling tailored solutions for diverse energy projects.
Flexible Connection (Thermal)
Technical arrangement that allows demand sites triggering thermal import network constraint to connect to the distribution network ahead of network reinforcement accepting that operationally their import capacity will be reduced down to a predefined profile by UK Power Networks DERMS.
DCUSA (Distribution Connection and Use of System Agreement) DCP (DCUSA Change Proposal) 404: Sites applying after 1st of April 2023, known as curtailable connections based on CCCM (Common Connection Charging Methodology), will have curtailment measured relative to a defined Curtailment Limit. The DNO (Distribution Network Operator)’s ability to curtail the customer may cease after an agreed Curtailment End Date. Should curtailment exceed the Curtailment Limit, the DNO will be required to pay the customer at a published set price.
Demand vs Generation: Flexible Connection is available both for demand and generation. The asset needs to be able to be ‘flexed’ and receive real-time control from UK Power Networks RTU (Remote Terminal Unit).
Transmission vs Distribution, Interim vs Enduring Curtailment - post-SCR (Significant Code Review):
| Type | Description |
|---|---|
| Distribution (interim) | Site is subject to curtailment driven by distribution thermal constraints, in place until distribution reinforcement is completed. Applies to sites with an “end date” to curtailment (post-SCR). |
| Distribution (enduring) | Site is subject to enduring curtailment from distribution thermal constraints. Applies to sites without an “end date” (post-SCR) or pre-SCR sites. |
| Transmission (interim) | Site is subject to interim curtailment from transmission thermal constraints, in place until transmission reinforcement is completed. Applies to solutions like Technical Limits. |
| Transmission (enduring) | Site is subject to enduring curtailment from Super Grid Transformers (SGT) transmission thermal constraints. |
Profiled Connection
Technical arrangement that allows demand sites triggering thermal import constraint to connect to the distribution network ahead of network reinforcement accepting that operationally their output might be reduced down to a predefined fixed profile by UK Power Networks DERMS.
Profiled Connection is offered for distribution import constraint only and supersedes the legacy Timed Connection product.
Find out moreFlexible Connection (Voltage)
Technical arrangement that allows DER triggering steady state overvoltage/undervoltage constraint to connect to the distribution network deferring the need for network reinforcement. Accepting to operate at a certain power factor at times when voltages exceed the allowed limits specified in Security and Quality of Supply Standards (SQSS). Power Factor instruction is issued by UK Power Networks ADMS (Advanced Distribution Management System).
Engineering Design Standards (EDS)
Please visit our G81 Technical Library where you will find the relevant Engineering Design Standards (EDS) for your Connections product.
Independent Distribution Network Operator (IDNO)
Our DERMS products can be used if you are connecting directly to the UK Power Networks distribution network or via an Independent Distribution Network Operator (IDNO).
EDS 08-1101 IDNO Networks details the connection arrangements for embedded networks owned and operated by licensed IDNOs.
Useful Guides
This section offers essential guides and resources for commissioning and operating Distributed Energy Resources (DER) with UK Power Networks. It covers everything you need to know for smooth integration and ongoing operation, ensuring your system meets all necessary requirements. Explore the linked documents for detailed guidance on the full process.
Curtailment Methodology
Since the start of our Flexible Connection offering in 2019, we have been issuing curtailment assessment reports at the connection offer stage to provide a view on the expected level of curtailment a site might be subject to whilst in operation.
We have now updated the tool used to produce curtailment estimates to facilitate an open and transparent approach to providing curtailment information. This document details the methodology and summarises the assumptions taken as part of the curtailment assessment studies.
The Connections Lab
Discover our new Connections Lab app, designed to provide a transparent and user-friendly approach to assessing curtailment estimates for flexible connections. Developed in collaboration with customers, the app opens up our network data, offering insights into potential curtailment levels and visibility of the connection queue at each grid supply point.
This self-serve tool empowers users to explore scenarios, adjust assumptions, and strategically plan their connections, saving time and resources. Available now in Beta, we’re actively seeking feedback to refine the app throughout 2025. Visit the app today and see how it can support your projects.
Explore the app and, if it’s your first visit, view the user guide below to see how to create your account.
