Browse our connections glossary of terms for descriptions and definition of acronyms, abbreviations and commonly used terms.


Allowed interruption

Where a customer is interrupted or tripped off within the parameters and provisions of their contract.

Appendix G

Appendix G is an Appendix to the Bilateral Connection Agreement of a Distribution Network Owner.

The Appendix G gives visibility to the DNO, TO and NGESO of the capability of their connection sites, available GSP capacity and an increased view of Embedded Generation levels.

Attributable works

Network reinforcement works between the point of connection and the nearest MITS.

Attributable works are secured by the customer under CMP192 and listed in the Appendix MM of the Construction Agreement where applicable.

ATV (Agreement to Vary)

The legal document signed to affect a change to your contracted position.



Backfeed will be required if you need to take power from the National Electricity Transmission System (NETS) to support your commissioning and build programme ahead of your connection date.

Balancing services

A range of services that are available for customers to provide to the ESO to assist in the operation and flexibility of the system.

BCA (Bilateral Connection Agreement)

This is an agreement required for any direct connections to the Transmission system.

It sets out requirements under relevant codes and is applicable to all types of direct connection e.g. generation, demand, DNO etc...

BEGA (Bilateral Embedded Generation Agreement)

A BEGA sets out requirements under the Grid Code, Connection and Use of System (CUSC) and Balancing and Settlement Code (BSC).

A BEGA will also provide you with Transmission Entry Capacity (TEC) and the right to operate in the electricity balancing market and export onto the NETS.

BELLA (Bilateral Embedded License exemptible Large power station Agreement)

This is a generator agreement in relation to an embedded connection to one of the Distribution networks in Scotland. The connection must be over a certain size in order to be eligible (10MW Northern Scotland or 30MW Southern Scotland). The agreement sets out requirements under relevant codes.

BM (Balancing Mechanism)

The balancing mechanism (BM) is a tool which we use to balance electricity supply and demand.

It allows generation customers to set prices for which they will increase or decrease their output if requested by the ESO.

All large generators must participate in the BM, whereas it is optional for smaller generators.

The process for participating will form part of the connections process after you have signed your offer. This will specify all the necessary communications equipment that you need to install to allow participation in the BM.

BSC (Balancing Settlement Code)

The Balancing and Settlement Code contains the rules and governance arrangements for electricity balancing and settlement in Great Britain.

The code covers the metering of the physical production and demand for electricity from generators, suppliers and interconnectors in relation to their contracted positions. And it also covers the calculating and settling of any imbalances when delivery or offtake doesn’t match those positions.

The BSC sets out a framework for making a submission to buy or sell electricity into or out of the market at close to real time.

BSUoS Charges (Balancing and Use of System Charges)

The BSUoS charge recovers the cost of day-to-day operation of the transmission system.


Cancellation charge

The charge that will be payable should a customer terminate their Construction Agreement ahead of connection.

Cancellation charges are visible for the coming 6 month period via bi-annual estimate statements sent by your ESO Contract Manager under both CMP192 and Final Sums methodology.

Capital contribution

A full or partial payment in respect of charges in your connection agreement, usually in relation to connection asset charges.

Capital contributions can be made via a set of payments pre-commissioning or a single payment on the Charging Date.

This is an alternative to paying charges over the life of a project.

CBA (Customer Build Agreement)

An Agreement between the customer and the relevant TO whereby the customer will procure and install certain transmission connection assets.

Also known as a User Self Build (USB) Agreement.

CEC (Connection Entry Capacity)

The CEC is the maximum potential output onto the system based on the capability of the plant equipment, which can be higher than the TEC.

It is often set higher than TEC to allow for changes over the years, without needing a change to the infrastructure or system, which leads to higher costs.

CfD (Contracts for Difference)

Contracts for Difference (CfDs) is intended to provide long-term revenue stabilisation to low-carbon Generators, allowing investment to come forward at a lower cost of capital and therefore at a lower cost to consumers.

Charging date

Normally the day after the connection date and the date upon which charges either become due or start e.g. one-off charges, TNuOS charges if applicable.

CION (Connections Infrastructure Options Note)

The CION process evaluates the respective transmission options required which leads to the identification and development of the overall efficient, coordinated and economical connection point, onshore connection design and, where applicable, offshore transmission system / interconnector design.

Clock start

The date on which your application & DRC data submission is deemed technically competent and your fee is paid (the latter of the two dates).

Clock start signifies the start of the 3 month offer period as defined in CUSC.

CMP192 (CMP192 – Enduring User Commitment Arrangements)

CMP192 is the CUSC modification code for User Commitment and became effective in April 2013.

Along with CUSC section 15 it explains the framework for customer security and applies to all customers categorised as generation or embedded generation.

Directly connected demand customers and DNOs secure under another methodology called Final Sums.

CMP192 principles include security requirements reducing as a connection becomes more certain and hits key milestones, the ability to fix attributable securities and the securing of a wider liability applicable to all parties.

Connection assets

A connected asset which has one sole user. These assets can be built, owned and maintained by the relevant TO Company and paid for by the customer or built and owned by the customer themselves dependent upon the agreed ownership boundary.

Connection date

The date by which a User can Connect to or make use of the Transmission Network following the completion of all necessary works.

Connection site

The point on the transmission system at which you connect (a substation or GSP).

ConsAg (Construction Agreement)

This agreement sits beside the BCA throughout the construction period of a project and contains the required works, key milestones and costs.

The construction agreement falls away on connection.

Contracted background

All contracted projects both connected and future.

Contracted party

Once an offer is signed and countersigned by NGESO the customer becomes a contracted party and will appear on the relevant registers dependent on the type of connection.

CUSC (Connection and Use of System Code)

This code that sets out the process for connection to and use of the transmission systems.

It contains all relevant commercial concepts in relation to the formation of your contract e.g charges, security.

It also contains the templates for the legal agreements used.

CUSC accession agreement

Any party with either a connection or generator agreement from NGESO is required to accede to the CUSC.

This agreement must be signed along with the other offer documents and all provisions under the CUSC will then apply to the contracted customer.

CUSC offer period

The 3 month period triggered by clock start in which NGESO has to issue an offer.


Directly connected

Any party physically connected to the transmission system rather than through a distribution network.

DNO (Distribution Network Operator)

DNO companies own and operate the power lines and infrastructure that connect homes and commercial properties to the NETS.

DRC (Data Registration Code)

The data registration code sets out the data that is required at each stage of the connections process.

There is also a DRC tool that can be populated using Excel for ease.



Elexon are an external entity who are responsible for administering the Balancing and Settlement Code (BSC), which states the rules and governance around balancing electricity in Great Britain.

They compare how much electricity generators and suppliers say they will produce and consume with actual volumes, helping to balance any differences.

Embedded generator

Generation projects connected to (embedded in) a distribution network.

Enabling works

Any works the relevant TO company must carry out on the transmission system to facilitate a customer connection.

EON (Energisation Operational Notification)

Issued by your compliance manager and required for first energisation of a new connection.


FID (Final Investment Decision)

This is the point at which your project is approved or sanctioned to go ahead(Customer side).

Final sums

Customers on Final Sums methodology for their security requirements secure all the TO spend for their project.

The security requirement is detailed in Appendix M to the Construction Agreement and updated bi-anually by your ESO Contract Manager.

This methodology applies to directly connected demand and DNO customers.


Unrestricted ability to export the maximum amount of contracted MW under any conditions.

FON (Final Operational Notification)

Issued by your compliance manager when all compliance activities have been resolved.


Grid Code

The Grid Code details the technical requirements for connecting to and using the National Electricity Transmission System (NETS).

Compliance with the Grid Code is one of the requirements of the Connection and Use of System Code (CUSC).

GSP (Grid Supply Plant)

A point of supply from the NETS to the local system of the DNO, or Connection Point at which the Transmission System is connected to a Distribution System.



An Intertrip is a piece of equipment that will automatically disconnect a generator from the transmission system, if it detects a specific event such as a system fault.

This is to relieve localised circuit overloads. There are two types of Intertrips:

Operational Intertrip: those that are a condition of connection to the transmission system

Commercial Intertrip: these may be specified at the time of connection or agreed on an adhoc basis. Within your connection offer, you may be required to install an Intertrip due to the location where you are connecting.

ION (International Operational Notification)

Issued by the Compliance team and required for first export on to the system.

IONs for Offshore connections come in two parts.


Key consents

It is the customer's responsibility to obtain the relevant planning consents for a project from the appropriate body.

Obtaining key consents will be a key project and milestone and will also impact on the level of security you will be required to place (CMP192 only).


LARF (Local Asset Reuse Factor)

A term related to the User Commitment methodology.

The LARF is the proportion of an asset or scheme that can be reused should a customer terminate once construction has commenced or spend has been committed.

LDTEC (Limited Duration Transmission Entry Capacity)

Any customer who has already connected to our transmission network can apply for LDTEC, this means a TEC increase or decrease for a period of up to six months.

LEEMPS (Licence Exemptible Embedded Medium Power Station)

LEEMPS is a classification of embedded generators that are ’medium’ (between 50-99 MW), and are therefore only applicable in England and Wales. LEEMPS generators do not have to have an agreement with NGESO but the relevant DNO company must have additional technical conditions and parameters added to their BCA.

LON (Limited Operation Notification)

Issued where a user was previously on a FON but the connection has been modified to a fault has occurred where the customer has an agreed limited amount of time to resolve the issue.


Modification application

A formal CUSC request to make changes to your existing agreement.

This will incur a fee and will follow the same offer process as your original application.


NETS (National Electricity Transmission System)

The high voltage transmission system operated by NGESO.

NGET (National Grid Electricity Transmission)

Onshore Transmission Owner in England & Wales.


Non-Firm contracts contain restrictions that limit a user being able to export their full capacity under certain conditions. The non-firm period can either be temporary (staged contract) or permanent.


OFTO (Offshore Transmission Owner)

An OFTO company is the owner of the infrastructure of an offshore transmission system.


Charges in respect of any additional one off works in your agreement. These charges are normally due on the Charging Date.


Additional works over and above the minimum technical solution required under SQSS.

One off works are usually the result of ‘customer choice.

These works can be found in Appendix B1 of the Construction Agreement appendices.

Operational notification

A certificate provided by our Compliance team required before any export of power onto the transmission system is made.

OSD (Offer Summary Document)

A summary document that will form part of your formal offer from NGESO.


Project progression

An application by a DNO to change their connection agreement in respect of embedded generation connected to their network.



The financial securing of the TO company spend by the customer in relation to their project, either through Final Sums or CMP192

SHET (Scottish Hydro-Electric Transmission)

Onshore Transmission Owner in Northern Scotland.

SIF (Strategic Investment Factor)

The proportion of a scheme spend attributable to a particular customer under the CMP192 securities methodology using the scheme capability and the CUSC

SPT (Scottish Power Transmission)

Onshore Transmission Owner in Southern Scotland.

SQSS (Security and Quality of Supply Standards)

The Security and Quality of Supply Standard sets out the criteria and methodology for planning and operating the National Electricity Transmission System (NETS).

SQSS (Security and Quality of Supply Standards)

Statement of works

A submission made by a DNO company in respect of new embedded generation connecting to their network to ascertain whether or not works are triggered and a project progression is required.

STTEC (Short Term Transmission Entry Capacity)

Any customer who has already connected to our transmission network can apply for STTEC, which is a temporary increase in TEC.

Find out how by referring to section 6.31 of the CUSC.


TEC (Transmission Entry Capacity)

TEC is the amount of MW you want to put on to NETS.

If you hold TEC you must also pay an annual fee to use the transmission system (TNuOS).

TEC Register

A list of contracted parties both existing connections and future projects that hold TEC with NGESO.

Technical competency

Review and approval of your application & DRC data submission.


The termination of contracts either by NGESO due to an event of default or customer driven

Third party works

These are works required for a customer connection that impact up to one or more other users where works are required to be carried out by a third party.

TNUoS charges (Transmission Network Use of System charges)

Charges payable by any party holding TEC with NGESO for use of the NETS.

Tariffs are published on an annual basis.

TO (Transmission Owner)

TO companies build, own and maintain the transmission system.

There are currently three onshore TO companies.

TOCO (Transmission Owner Construction Offer)

The contract offer the TO company will prepare for signature by NGESO in respect of the works required for a customer connection.

TRA (Transmission Related Agreement)

Where a customer contract specifies restrictions on availability a TRA will be required.

The TRA sets out what is expected of a customer that does not comply with their restrictions on availability.

Trigger date

The date under the securities methodology at which point wider liabilities and securities become applicable.

TWR (Transmission Works Register)

A list of TO network reinforcement schemes being progressed in relation to the contracted background.


User works

Works set out in the Construction Agreement that the project developer expected to achieve to facilitate their connection.


Wider tariff

Generic £/MW for all generators in a particular zone, each zone has a £/MW tariff.

The Tariff is based on total annual TO asset spend and customers are only expected to secure against this once they have hit their trigger date.

A Tariff Statement is published annually and contains the tariff for the coming year (effective from 1st April) and three years forecast.