Settlement Metering for Offshore Wind Farms |
Guidance Note |
This guidance note clarifies the
Balancing and Settlement Code (BSC) requirements for measuring and recording flows of
electricity for
Settlement purposes at
Offshore wind farms that are subject to the
Offshore Transmission Regime, i.e.
Offshore wind farms that connect onshore to the
Transmission System, or a
Distribution System, where the
Offshore transmission assets convey
electricity from or to shore at or above 132,000 volts (132kV).
In particular it highlights, in example diagrams, the requirement to provide Settlement Metering Equipment to:
measure and record the flows of electricity to a wind farm generator’s assets at low voltages (e.g. 240/415 volts), at the onshore and Offshore substations; and
measure and record the flows of electricity at the point(s) onshore where the Offshore transmission assets for these Offshore wind farms connect to a Distribution System.
The guidance is primarily aimed at designers and developers of these Offshore wind farms and the companies (BSC Parties) that are ultimately responsible for registering the Metering Equipment (i.e. Registrants) installed at these Offshore wind farms to measure and record these flows of electricity. The guidance will also be useful to designers of Metering Systems, which may include Meter Operator Agents.
Which flows of electricity need to be measured for Settlement purposes?
Section L of the BSC requires the quantities of
electricity (i.e.
Active Energy, and where relevant,
Reactive Energy)
Exported or
Imported at a
Boundary Point to the
Total System, or flowing between
Systems at
Systems Connection Points, to be measured (and recorded) by
Metering Equipment. The
Metering Equipment must:
comply with the relevant metering Code of Practice (CoP) for the circuit capacity/demand;
be commissioned in accordance with CoP4; and
for Metering Equipment that is to be registered in the Central Meter Registration Service (CMRS) as a Central Volume Allocation (CVA) Metering System, undergo a proving test in accordance with BSC Procedure 02 (BSCP02).
What is a Boundary Point?
A
Boundary Point (BP) is defined in
Section X, Annex X-1 as a point at which any
Plant or
Apparatus, that does not form part of the
Total System, is connected to the
Total System. The
Total System is comprised of the following
Systems:
For its definition of Transmission System the BSC refers to the meaning of the term ‘National Electricity Transmission System’ (NETS) in the Transmission Licence. The meaning of the term NETS includes OTSUA and Offshore Transmission Systems (OTS).
When OTSUA are transferred to an Offshore Transmission Owner (OFTO), and its Transmission Licence becomes effective, the OTSUA become an OTS. The BSC considers both OTSUA and OTS part of the Transmission System and, therefore, the Total System.
This means that where any generator’s assets in the onshore or Offshore substation connect to OTSUA (or OTS, once operated by an OFTO) these points of connection will be Boundary Points to the Total System. The flows of electricity to or from them need to be measured and recorded by Metering Equipment for Settlement purposes.
What is a Systems Connection Point?
A
Systems Connection Point (SCP) is defined in
Section X, Annex X-1, as a point of connection (whether consisting of one or more circuits) between two or more
Systems. The definition also clarifies that the point of connection of OTSUA to the
Transmission System is not a SCP.
Since the introduction of term OTSUA into the BSC any Offshore transmission assets for these Offshore wind farms that connect onshore to a Distribution System, are considered part of the Transmission System. This means that the point(s) of connection onshore constitutes a SCP called an Offshore Transmission Connection Point (OTCP), a form of Grid Supply Point. The flows of electricity between the OTSUA (or OTS, once operated by an OFTO) and a Distribution System need to be measured and recorded by Metering Equipment for Settlement purposes.
Who is responsible for an Import/Export at a Boundary Point?
Section K defines what an
Import and an
Export at a
Boundary Point are and which BSC
Party (
Party) is responsible for separately measuring those flows. In the case of an
Import to and an
Export from a
Generating Plant, where
electricity is generated by a
Party who holds a
Generation Licence, then that
Party is responsible for those flows.
The Party responsible must register the Metering Equipment as a Metering System in the relevant registration system (i.e. CMRS or a Licenced Distribution System Operator’s (LDSO) Supplier Meter Registration Service). Metering Equipment measuring Imports/Exports related to any Licensable Generating Plant and sites connected directly to the Transmission System must3 be registered in the CMRS as a CVA Metering System(s).
Who is responsible for flows of electricity at an Offshore Transmission Connection Point?
Section K also defines who is responsible for
Systems Connection Points and for measuring the flows of
electricity between
Systems. The
Party responsible for flows of
electricity at an OTCP is the National Electricity
Transmission System Operator (NETSO).
The NETSO must ensure Metering Equipment is installed to separately measure these flows of electricity (imports and exports) and register the Metering Equipment as a Metering System in CMRS as a CVA Metering System(s).
Diagram representing the Total System (pre and post OFTO):
Where exactly are measurements required to be made for Settlements purposes?
Appendix A of each Half Hourly CoP (i.e. CoPs 1, 2, 3 and 5) sets out the points at which measurements of Imports and Exports at Boundary Points and flows of electricity between Systems at SCPs need to be made. These are called the Defined Metering Points.
Under
Modification Proposal P238 the
Party responsible for
Boundary Point Metering Equipment for
Offshore Power Park Modules (PPMs) can install the
Offshore Boundary Point Metering Equipment either at the point(s) of connection to the
Transmission System on the
Offshore platform or at a deemed
Boundary Point(s) on the
Offshore platform. Where the
Offshore Boundary Point Metering Equipment for the
Offshore PPM(s) is installed at a deemed
Boundary Point(s) on the
Offshore platform
BSC Section K (1.1.6) and the CoPs require accuracy compensation for any electrical losses to the point of connection to be considered and, where necessary, applied to the
Meter(s) or via the
Data Collector’s system.
For an Offshore Boundary Point to the Transmission System for low voltage supplies to the wind farm operators assets the Metering Equipment must be installed at the point of connection.
For an onshore Boundary Point to the Transmission System or a Distribution System (e.g. for low voltage supplies to the wind farm operators assets) the Metering Equipment must be installed at the point of connection.
For an OTCP the Metering Equipment must be installed at the point of connection between the Transmission System and the Distribution System.
The example diagrams provided, on the following pages, illustrate where Settlement metering is/may be required pre and post OFTO transfer for these Offshore wind farm that connect to the Transmission System or a Distribution System.
Under Change Proposal
CP1575 the use of busbar voltage transformers is allowed under CoPs 1 and 2. This change reduces the need for multiple voltage transformers at the string level on the Offshore wind farm power transformer platforms by allowing the placement of voltage transformers at the busbar. The example diagrams provided, on the following pages, illustrate the arrangement for busbar voltage transformers for CoPs 1 and 2 circuits where it is a single busbar and where the busbars are electrically split.
Additional information on Primary BM Units and Trading Units
The BSC requires the Party who is responsible for the Imports and/or Exports to or from Plant and Apparatus to assign that Plant and Apparatus to a Primary Balancing Mechanism Unit (BM Unit). This includes all flows to a wind farm generator’s assets at low voltages (e.g. 240/415 volts), at the onshore and Offshore substations.
BSC Section K3.1 sets out the requirements for the configuration of
Primary BM Units and includes a number of standard
Primary BM Units, including:
a Power Park Module (PPM) (defined in the Grid Code);
a Combined Offshore BM Unit (two or more Offshore Power Park Modules as defined in the BSC);
the Plant and Apparatus which comprises part of, and which Imports electricity through the station transformer(s) of a Generating Plant where the Metering System(s) for such Imports is or are registered in CMRS; and
the premises (of a Customer supplied by a Party) which are directly connected to the Transmission System, provided that such premises are so connected at one Boundary Point only.
If there is any Plant and Apparatus that does not fall into a standard Primary BM Unit category then the responsible Party can apply for a non-standard Primary BM Unit. Parties can also apply for non-standard Primary BM Units where the Plant and Apparatus does meet standard categories but the relevant Party considers that a different configuration would still meet the requirements of the BSC.
Applications for non-standard
Primary BM Unit configurations require BSC
Panel approval in accordance with
Section K3 and
BSCP15 following consultation with the NETSO. The BSC
Panel has delegated approval of non-standard
Primary BM Unit configurations (and
Trading Unit Applications) to the
Imbalance Settlement Group (ISG). Applications for non-standard
Primary BM Unit configurations need to be submitted to Elexon (
bm.unit@elexon.co.uk) at least 60 WD prior to the
Primary BM Unit Effective From Date (EFD).
A
Primary BM Unit is by default a
Trading Unit however a
Party can apply to the ISG, in accordance with
Section K4,
Section K (Annex K-2) and
BSCP31, to have a combination of
Primary BM Units in a
Trading Unit. Applications for
Trading Units need to be submitted to Elexon (
trading.unit@elexon.co.uk) at least 30 WD prior to the next available ISG meeting and can be made in advance of the registration of the relevant
Primary BM Units.
Transmission System Connected Offshore Wind Farm
Distribution System Connected Offshore Wind Farm
CoP1 (single busbar): using busbar voltage transformers at a Transmission System Connected Offshore Wind Farm
CoP1 (electrically split busbar): using busbar voltage transformers at a Transmission System Connected Offshore Wind Farm
CoP2 (single busbar): using busbar voltage transformers at a Transmission System Connected Offshore Wind Farm
CoP2 (electrically split busbar): using busbar voltage transformers at a Transmission System Connected Offshore Wind Farm
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