Settlement Metering for Offshore Wind Farms
This guidance note clarifies the Balancing and Settlement Code (BSC)
requirements for measuring and recording flows of electricity
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?
of the BSC requires the quantities of electricity
(i.e. Active Energy
, and where relevant, Reactive Energy
ed or Import
ed at a Boundary Point
to the Total System
, or flowing between System
s at Systems Connection Point
s, to be measured (and recorded) by Metering Equipment
. The Metering Equipment
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
, that does not form part of the Total System
, is connected to the Total System
. The Total System
is comprised of the following System
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 System
s. The definition also clarifies that the point of connection of OTSUA to the Transmission System is not
a Systems Connection Point
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?
defines what an Import
and an Export
at a Boundary Point
are and which BSC 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?
also defines who is responsible for Systems Connection Point
s and for measuring the flows of electricity
s. The Party
responsible for flows of electricity
at an OTCP is the National Electricity Transmission System Operator
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 Systems Connection Points need to be made. These are called the Defined Metering Points.
Under Modification Proposal P238
responsible for Boundary Point Metering Equipment
for Offshore Power Park Module
s (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
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.
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 Unit
s and includes a number of standard Primary BM Unit
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
following consultation with the NETSO. The BSC Panel
has delegated approval of non-standard Primary BM Unit
configurations (and Trading Unit Application
s) 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)
, to have a combination of Primary BM Unit
s in a Trading Unit
. Applications for Trading Unit
s 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 Unit
Transmission System Connected Offshore Wind Farm
Distribution System Connected Offshore Wind Farm
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